CABI International Institute of Parasitology, 395A Hatfield Road, St Albans, ...... in the Gulf of California (Polis & Hurd, 1995) may be relevant in the explanation.
Biocontrol Science and Technology (1996) 6, 317± 331
Entomopathogenic Nematodes: Biodiversity, Geographical Distribution and the Convention on Biological Diversity W ILLIAM M. HOM INICK, ALEXANDER P. REID, DAVID A. BOHAN BERNARD R. BRISCOE
AND
CABI International Institute of Parasitology, 395A Hatfield Road, St Albans, Herts AL4 0XU, UK
This pape r address es thre e m ajor issues. Firstly, m olecula r taxono m y and its applicat ion to elucidat e the biodiver sity and biogeog raph y of ento mopathog enic nem atodes is conside red. Accurat e identific atio n is fundam enta l for underst andin g biodiver sity , and becaus e these nem atodes are m orpholo gically conserv ative , molecula r techniq ues will provid e the insight s necessa ry to develo p a robust , morpholo gically base d taxono m y. Secondly, a review of the knowledg e on their biogeog raph y and habita t specific ity, includin g a conside ration of the lim itation s to the availabl e data is given . M uch of the infor mation is presente d in tw o table s which sum marize the distribu tion s of recogniz ed specie s at continen tal and nationa l levels. Thirdly , this pape r provide s a brie f conside ration of the Conventi on on Biologica l Diversit y and its im plication s for future work with ento mopathog enic nem atodes and biologic al control . K eyw ord s: Steinerne m a, H eterorha bditis, biodive rsity, geograp hica l distribu tion, m olecula r taxono my, habita t specific ity
INTRO DU CTIO N K now ledg e of the biodiver sity and geograp hica l distribut ion of ento mopathog enic nem atodes is in its infancy , yet these are key issues for regulatory authorit ies. Even thoug h a num ber of survey s have been carrie d out, coverin g parts of every continen t, m ost of the w orld rem ains unexplo red. In m any of these surveys , m ajor question s regarding the identific atio n of the nematode s isolate d and the m ethods used to recove r them canno t be resolved . To add to the uncertai nty, the Conventi on on Biologica l Diversity , w hich cam e into effec t in December 1993, has legally bindin g regulati ons regarding ownershi p of organis ms, rights to collec t them and rights to involv e thir d parties . This will undoubt edly imping e on future w ork, but in an unkno wn w ay becaus e the mechanis ms for dealin g with the Convention are not yet in place. This pape r is structure d to deal w ith three m ajor topics : (1) m olecula r taxono m y and its applicat ion to elucidat e the biodiver sity and biogeog raphy of ento m opathog enic nem atodes ; (2) a revie w of curren t know ledg e of the biogeog raph y and habita t specifici ty of thes e nem atodes; (3) a brief conside ratio n of the C onventi on on Biologica l Diversit y and its im plication s for future work. 0958±3157/96/030317±15 $7.50
Ó 1996 Journals Oxford Ltd
318
W . M . H OM INIC K ET AL .
M O LECU LAR TA XO NO M Y A ccurat e identifi catio n is funda mental to understa ndin g the geograp hical distribut ion and habita t specificity of any organis m. Thus, while the results of a large number of survey s are reporte d in the literatur e, thos e in w hich the ento mopathog enic nematode s w ere identifie d only as Steinernem a sp. or Heterorha bditis sp. are useles s for biogeog raph y and habita t inform ation . The only conclus ions that can be draw n from such studie s are that ento m opathog enic nem atodes are w idesprea d. How ever, accurat e identific ation of the nem atodes is not a trivia l task. It is both labou r intensiv e and time consu m ing, and thes e nematode s are m orpholo gically conserv ative. W e w ould argue that this is a case w here m olecula r techniqu es m ust lead tradition al m orpholo gical m ethods . That is, distincti ons base d on molecula r charact erizatio n will elucidat e specie s and groupin gs w hich can then be studie d for m orpholo gical characte rs that distingui sh them from each other. W e do not advocat e the replace ment of tradition al method s by m olecula r ones, but w e do believ e that m olecula r techniqu es will provid e the insight s necessa ry to develo p a robust , m orpholo gically base d taxono m y. A num ber of molecula r techniqu es have been used for ento mopathog enic nematode identifi cation , includin g isoenzy m e pattern s (Akhurst , 1987) , tota l protein pattern s (Poinar & Kozodoi , 1988), im munologi cal techniqu es (Jackso n, 1965 ) and restricti on frag m ent length polym orphis m (RFLP) detectio n within tota l genom ic DN A (C urra n & W ebster , 1989 ; Smits et al., 1991 ; Reid & Hom inick , 1993). H ow ever , thes e techniq ues all dealt with relativel y small num bers of sam ples. To identif y larg e num bers of sam ples, a sim ple and, m ost importantl y, reliabl e test is require d. T he RFLP analysi s of poly m erase chain reactio n (PCR) amplified product s from specific region s of the geno m e satisfie s these criteria , and is a pow erful taxono mic tool that can be used for the identifi catio n of single nematodes . Region s of taxono mic importanc e includ e the interna l transcri bed spacer (ITS) of the riboso m al DNA (rD NA ) repea t unit and the regio n of the m itochon drial geno me w hich separate s the cytochr om e oxidas e subuni t II (CO II) and the 16S genes. Both of thes e region s have been w idely used for nem atode identific atio n (V rain et al., 1992; Pow ers & H arris, 1993; Curran & Driver, 1994 ; Joyc e et al., 1994a,b ; Reid, 1994), and w ill m ake m ajor contribu tions to the identific atio n of ento mopathog enic species . It is now abunda ntly clea r that ento mopathog enic nem atodes can exist as strains w hich differ biologi cally (e.g . H ominick & R eid, 1990; G laze r et al., 1993; Goug e & H ague, 1995). Thus, the next stage is the develop m ent of techniqu es for the identific atio n of strains of ento mopathog enic nematodes . C urran and Driver (1994 ) have recentl y shown intra-sp ecific variatio n in heteror habditids, and Reid and Hominic k (1993 ) have show n that S. feltiae exists as tw o RFLP types. To this end, it may be possibl e to use the rando m amplificati on of poly m orphic DNA (RA PD) techniq ue (W elsh & M cClelland , 1990 ; W illia ms et al., 1990). U nlik e the PCR procedu re to am plify portion s of the ITS and m itochond rial D NA the RA PD procedu re obviate s the need for prio r sequenc e information by usin g a single 10-m er oligonuc leotid e of arbitrar y sequenc e. W hen tw o such prim er sequenc es are presen t in the targe t geno mic D NA , in the correc t orientation and on opposit e strand s within a readily am plifiabl e distanc e (usuall y less than 3 kilobase s), a discret e produc t is formed. In many cases, individu al RA PD primers w ill detect a number of such product s from a geno mic D NA sam ple (typicall y betw een 5±10 bands in the size rang e 30±3000 base pairs) which yield s a `fingerp rint’ for the sample. H owever, of all the PCR method s availabl e, the RA PD reactio n is the m ost sensitiv e to change s in the reactio n conditio ns such as D NA concentration, buffe r conditio ns (especia lly the M gCl 2 concentration) , the num ber of am plificati on cycle s and the accurac y of cyclin g of the PCR m achine . The potentia l for artefact ual results is therefor e high , and a large num ber of differen t prim er sequenc es must be screene d to ensur e that only thos e that give clear , unequiv ocal and consiste nt results are used and to ensure , as far as possible , that the reactio n conditio ns from one run to the next are identical . D espite these potential proble m s, applicat ion of the RA PD techniqu e to plant-pa rasitic nem atodes has yielde d poly m orphis m s that can be used for strain identifi catio n (Fargette et al., 1994; Opperm an et al., 1994). There is no reaso n to suppos e that strain s of ento mopathog enic specie s will not be characte rized as w ell, althoug h initial work on the use of RA PDs for
EN TOM O PA THO G ENIC N EM ATO DES: B IOD IV ER SITY AND D ISTR IBU TIO N
319
entom opathog enic nematod e identifi catio n has largely centre d on specie s identific ation (G ardner et al., 1994 ; Berry & Liu, 1995). The ability to charact erize strain s w ould be usefu l in order to m onito r the outco me of release s of non-indi genou s strains . In some cases , such as in populati on biolog y studies , individu al nem atodes need to be identifi ed to strain level. If so, it will be necessa ry to develo p techniqu es furthe r becaus e individu als cannot be reliabl y identifie d w ith the R APD techniqu e, at least for the presen t tim e. G EOG RA PHICA L DISTRIBUTION The term `geogra phica l distribut ion’ is m eaningle ss w ithou t an attendan t scale . Geograph ical distribu tion can be viewed at the global , continen tal, nationa l and local field level (m acrodist ribution) , and then on a scale relate d to the distribut ions of individu als in the soil (microdist ribu tion). In this section , we conside r m acrodistr ibution to the nationa l level. In the next section it is consider ed at the field level, which. can also be discusse d as habita t specific ity. M icrodistribu tion is beyon d the scop e of this paper, thoug h it is a funda menta l conside ratio n for populati on biology , gene flow and biologic al contro l progra m mes. In discussi ng geograp hical distribut ion, the fundam ental assu mptions are that specie s were original ly correctl y identified and that sampling has been adequat e (see W alther et al., 1995). The questio n of identific ation has been discusse d and it is necessar y to consider , thoug h briefly , the adequa cy of sam plin g for ento mopathog enic nem atodes . M ost survey s have used a bioassa y based on the `Galleria trap ’ (Beddin g & A khurst , 1975), w hich recover s nem atodes which are infectiv e to Galleria at the time of sam plin g but which leave s the identit y of the natura l host unkno wn. W hat abou t specie s w hich m ay not infect G alleria? Also, infectivi ty may vary temporally , so that a negativ e assay at one plac e m ay not prov e to be negativ e if a sam ple is take n from the sam e site at anothe r time (e.g . Hom inic k & B riscoe , 1990a ) or the sam e sam ple may test negativ e in one bioassa y but positiv e in a later one (Hominick & Briscoe , 1990a,b ; Stuar t & G augler , 1994). Passiv e soil extractio n m ethods , such as centrifu gation , differen tial settlin g or W hitehea d trays, recove r m any more nem atode s and specie s (see Ehler s & Peters , 1995), and henc e are to be preferre d for geograp hical studies . H owever, the m ethods are very labou r intensiv e, so fewer samples can be process ed (Curra n & H eng, 1992). Further m ore, spatia l patchin ess in populati ons (Fan, 1989; Boag et al., 1992; Stuart & G augler , 1994 ; J. M . M ason & W . M . Hominick , persona l comm unicatio n, 1993 ) has im plication s for sam pling , w hether techniqu es use activ e or passiv e m ethods of extracti on. Also, the information available may reflec t the distribut ion of scientis ts workin g on particul ar group s or specie s rather than the distribut ion of the organis m s. Finally , the increasi ng use of thes e nematode s for biologic al contro l m ay result in the establis hment of exotic species , and henc e a w ider distribut ion than w ould occu r naturall y. For example, S. scapteri sci w as though t to be a strain of S. carpoca psae w hen it was isolate d in Uruguay . It w as release d into Florida, w here it has now beco me establis hed and can be disperse d by infecte d m ole cricket s (see Parkman & Sm art, 1996). W hen all these limitation s are conside red, the reader should be cautiou s in draw ing conclus ions from w hat follo ws. G lobal Distributions In the broades t sense , ento m opathog enic nem atodes are w idesprea d. The only contine nt where they have not been foun d is Antarctic a (Griffin et al., 1990). This conclusi on arise s from the results of a number of survey s (m ost of them cited in this revie w) but, for reason s outline d in the taxono m y section , m ore precis e statem ents are difficul t becaus e identifi catio n frequen tly stoppe d at the generi c level. Also, some literatur e suggest s that steinern ematid s dom inate in cooler , tem perate soils while heterorh abditid s dom inate in tropica l conditio ns, but this broad generali zatio n has recently been called into questio n (Am arasingh e et al., 1994). Table 1 sum m arizes the infor mation on the geograp hica l distribu tion by continen t for the ento m opatho genic specie s describe d up to the tim e of writing. Table 2 is an attem pt to narro w the availabl e inform atio n dow n to a nationa l level, assu ming that the author s identifie d the nematode s
320
W . M . H OM INIC K ET AL .
accurat ely. Readers should also consul t the revie w by Peters (1996) , w hich sum marize s all availabl e information from naturall y infecte d hosts and w hich provide s valuabl e biogeog raphical , as well as host specific ity, inform ation . W ithin the steinern ematids, two specie s appea r to have a global distribu tion , nam ely S. feltiae and S. carpoca psae (Table s 1 and 2). In fact, S. feltiae is w idesprea d in Tasmania and other state s of south-ea stern A ustralia , and is foun d in habitat s such as pastures , roadsid es, forests and gardens , as well as in nationa l park s where hum an influenc es on the environ ment are minim al (R. A . Bedding , persona l com municatio n, 1995) . This specie s also dom inates in E urope, particul arly in field s and roadsid e verge s (see below ). Such a wide globa l distribut ion suggest s that S. feltiae is an efficien t disperse r, possibl y throug h m an’ s activitie s in m ovin g soil and/or by infecte d insects . A lternativ ely, this is an ancien t specie s w hich w as presen t before continents bega n breakin g up and drifting . The othe r steinern em atid specie s appear to have a m ore restricte d distribut ion and are recorde d at continen tal or nationa l levels. For example, S. affinis and S. krausse i appear to be restricte d to Europ e (H om inick et al., 1995), w hile S. rara and S. ritteri appear to be restricte d to South A merica . The picture is som ewhat differen t for the heterorh abditids . To start with, fewer heterorh abditids have been describe d and few er Heterorh abditis isolate s have been identifi ed to the specie s level becaus e they are m orpholo gically conserva tive and positiv e identifi catio n require s rare expertis e, D NA fingerpr inting or cross-br eedin g techniqu es (Dix et al., 1992). Neverthel ess, the data that are availabl e yield entirel y differen t results when compared with the steinern em atids. O ne specie s in particul ar, H. indicus , appear s to be found through out the tropics . Identific ation based on RFLPs of the ITS region of the rDN A repea t have show n this specie s to be presen t in India, Sri Lanka, Japan , norther n Australia , C uba and the C aribbea n (Joyc e et al., 1994a; A . P. Reid, unpubli shed) . Anothe r w idely distribut ed heterorh abditid is H. bacteri ophora, found in N orth and South Am erica (Poinar, 1990), souther n Europ e (Sm its et al., 1991 ; D e D oucet & G abarra , 1994), A ustrali a (Poinar, 1990 ) and C hina (Li & W ang, 1989). In comparison , H . hawaiiensi s has so far only been found in H aw aii (G ardner et al., 1994 ) and therefor e appear s to be m ore localize d, but this m ay sim ply reflect its recent discover y. The identific ation and distribu tion of H . m egidis raise some intriguin g question s. This specie s w as originall y isolate d from O hio in the US and has two very closely related RFLP types in Europe. O ne w as designat ed the `NW Europea n species ’ (Sm its et al., 1991 ; Joyce et al., 1994a) and is found through out the N etherlan ds and G erm any and has also been isolate d once from the U K (Hominick et al., 1995). The othe r w as designat ed the `Iris h species ’ and is found only in Ireland and the UK . How ever, both of these are extrem ely closely relate d at the DN A level to the origina l O hio H . megidis (Curran & Driver, 1994 ; Reid, 1994). To furthe r com plicate m atters, w e have recentl y identifie d the Ohio type H. m egidis from Japanes e soils (M . Yoshida & A. P. R eid, unpubli shed). Question s such as whethe r we are dealin g with differen t specie s or strains , their relatedn ess and their origin and evolution rem ain to be answered before the geograp hical distribu tion of this com plex is resolved . Exam ination of T ables 1 and 2 and compariso n of Table 1 in Curra n and Drive r (1994 ) w ith Table 1 in Reid (1994) revea l that m any more steinern ematids than heteror habditid s have been describ ed. This m ay simply be an artefact , reflectin g the practica l difficult y of distingu ishing heteror habditi d species . A lternatively, it may be a real pheno menon , reflectin g the fact that the biodive rsity of steinern ematids is greate r than that of heteror habditid s. Recen t work in our laborat ory in collabor ation w ith M . Y oshid a of T he Nationa l Institut e of Agro-Environ mental Sciences , Tsukuba , Japan support s such an hypothe sis. O f 93 sam ples collecte d from Japa n and identifi ed by m olecula r techniqu es, eigh t distinc t Steiner nem a geneti c types were identifie d. Steinerne m atid s m ade up 73% of the collectio n and only one of these had been describe d (S. kushidai ); the other seven were all new to science . One of the specie s dominate d and made up 45% of the identifie d samples . In contrast , only tw o H eterorha bditis specie s w ere isolated , H . indicus and H. m egidis , thoug h they made up 15 and 12% of the collecti on respecti vely . RFLP studie s of the ITS region s showed that the Japanes e H. indicus is identica l to our Sri Lankan (HSL 43) isolate and the D 1 populat ion from Australia . T he Japanes e H . megidis
a
H. H. H. H. H. H.
a
1
1 1
1
1
1
1
1
1
1
1
N orth A m erica
1
1
1
1
1
1
1
South A m erica
1
A frica and India
1
1
1
1
1
1
A ustralia and N ew Z ealand
Current nam es of nem atodes are giv en; author citations in parentheses refer to papers w here prev ious nam es w ere used.
argentinensis, S tock , 1993b bacteriophora, Poinar, 1976 hawaiiensis, Gardner et al., 1994 indicus, Poinar et al., 1992 megidis, Poinar et al., 1987 zealandica (Poinar, 1990)
N. longicurvicauda, N guy en & S m art, 1994
1
1
1
1
1
1
1
Europe and R ussia
1
1
1
1
1
1
1
1
Japan and China
1
1
1
1
1
Others
R ecorded distribution of described species of entom opathogenic nem atodes of the genera Steinernema, Neosteinernema and Heterorhabditis in different continents
S. af® nis (B ovien, 1937) S. anomali (K oz odoi, 1984) S. bicornutum, T allosi et al., 1995 S. carpocapsae (W eiser, 1955) S. caudatum, X u et al., 1991 S. cubana, M raÂcÏ ek et al., 1994 S feltiae (Filipjev , 1934) S. glaseri (S teiner, 1929) S. intermedia (Poinar, 1985) S. kraussei (Steiner, 1923) S. kushidai, M am iy a, 1988 S. longicaudum, Shen, 1992 S. neocurtillis, N guyen & S m art, 1992 S. rara (De Doucet, 1986) S. riobravis Cabanillas et al., 1994 S. ritteri, De Doucet & De Doucet, 1990 S. scapterisci, N guy en & S m art, 1990 S. serratum, L ui, 1992
S pecies
T A B L E 1.
EN TOM O PA THO G ENIC N EM ATO DES: B IOD IV ER SITY AND D ISTR IBU TIO N
321
322 TABLE 2.
W . M . H OM INIC K ET AL .
Recorded distribution of described species of entomopathogenic nematodes of the genera Steinernema, Neosteinernema and Heterorhabditis in different countries
Species
Country
Reference
S. af® nis
Belgium Denmark Ireland Germany Holland Switzerland UK
A. P. Reid (unpublished) Poinar (1988) Griffn et al. (1991) Ehlers et al. (1991) Hominick et al. (1995) Steiner (1994) Hominick et al. (1995)
S. anomali
Russia
Kodozoi (1984)
S. bicornutum
Serbia
Tallosi et al. (1995)
S. carpocapsae
Australia Brazil Canada Czech Republic France Italy Korea Mexico Poland Russia Sweden USA
Poinar (1986) A. P. Reid (unpublished) Poinar (1986) Poinar (1986) Poinar (1986) Ehlers et al. (1991) Choo et al. (1996) Poinar (1986) Poinar (1986) Poinar (1986) Poinar (1986) Poinar (1986)
S. caudatum
China
Xu et al. (1991)
S. cubana
Cuba
M raÂcÏ ek et al. (1994)
S. feltiae
Argentina Australia Belgium Denmark Ireland Estonia Finland France Greece Hawaii Holland Hungary New Zealand Norway Poland Russia Slovakia Sweden Switzerland Turkey UK USA
Stock (1993a) Poinar (1986) J. S. Miduturi & A. P. Reid (unpublished) Poinar & Lindhardt (1971) Grif® n et al. (1991) A. P. Reid (unpublished) VaÈ nninen et al. (1989) Poinar (1986) A. P. Reid (unpublished) A. P. Reid (unpublished) Hominick et al. (1995) M raÂcÏ ek & Jensen (1988) Poinar (1986) Haukeland (1993) Sandner & Bednarek (1987) A. P. Reid (unpublished) M raÂcÏ ek et al. (1982) Burman et al. (1986) Steiner (1994) A. P. Reid (unpublished) Hominick et al. (1995) Poinar (1992)
S. glaseri
Brazil China Spain USA
Pizano et al. (1985) Li & W ang (1989) De Doucet & Gabarra (1994) Poinar (1986)
S. intermedia
USA Switzerland
Poinar (1985) Steiner (1994)
EN TOM O PA THO G ENIC N EM ATO DES: B IOD IV ER SITY AND D ISTR IBU TIO N
TABLE 2.
323
Continued
S. kraussei
Czech Republic Germany Germany Holland Russia Switzerland UK
M raÂcÏ ek (1980) M raÂcÏ ek et al. (1992) M raÂcÏ ek (1994) Hominick et al. (1995) A. P. Reid (unpublished) Steiner (1994) Hominick et al. (1995)
S. kushidai
Japan
M amiya (1988)
S. longicaudum
Australia China
R. A. Bedding (personal communication, 1995) Shen (1992)
S. neocurtillis
USA
Nguyen & Sm art (1992)
S. rara
Argentina
De Doucet (1986)
S. riobravis
USA
Cabanillas et al. (1994)
S. ritteri
Argentina
De Doucet & De Doucet (1990)
S. scapterisci
Argentina Uruguay
Stock (1992) Nguyen & Sm art (1990)
S. serratum
China
Lui (1992)
N. longicurvicauda
USA
Nguyen & Sm art (1994)
H. argentinensis
Argentina
Stock (1993b)
H. bacteriophora
Australia China Israel Italy Korea Spain USA
Akhurst (1987) Akhurst (1987) Glazer et al. (1993) Akhurst (1987) Choo et al. (1995) De Doucet & Gabarra (1994) Poinar & Georgis (1990)
H. hawaiiensis
Hawaii
Gardner et al. (1994)
H. indicus
Australia India Japan Sri Lanka Trinidad
Akhurst (1987) Poinar et al. (1992) A. P. Reid (unpublished) Am arasinghe et al. (1994) A. P. Reid (unpublished)
H. megidis
Belgium Canada Ireland Holland Japan UK USA
M iduturi & A. P. Reid (unpublished) M raÂcÏ ek & Webster (1993) Joyce et al. (1994a) Hominick et al. (1995) A. P. Reid (unpublished) Hominick et al. (1995) Poinar et al. (1987)
H. zealandica
New Zealand
Akhurst (1987)
yielde d an identica l pattern to that from the origina l isolate from O hio (which display s m inor, but distinct , RFLPs w hen com pare d w ith the NW Europea n and Irish types) . These differen ces in the biogeog raphy of the two fam ilies could be an effect of the first-gen eratio n hermaphrodi tic reprodu ctiv e strateg y of the heterorh abditids , which could lead to the producti on of `clones ’ after infectio n by single nematodes , while the obligat e sexua l life cycle of the steinern em atid s m ay favou r greate r geneti c diversit y and speciati on. This hypothe sis is support ed by molecula r data. A phyloge netic tree construc ted from restricti on enzy m e site data of the rDN A repeat unit suggest s that heterorh abditid specie s are much m ore closely related to one anothe r than
324
W . M . H OM INIC K ET AL .
are steinern ematid specie s (Reid, 1994). Sim ilarly , despit e testin g a large num ber of geograp hically separate d isolates , Curra n and D river (1994 ) foun d that the heteror habditids fell into a few specie s groups and that more work was require d to determ ine whethe r these group s represe nted specifi c or subspec ific differen ces. Hence , many more steinern em atid than heterorhab ditid specie s m ay exis t on a globa l scale and these m ay show a greate r biologic al diversit y, w ith attendan t divers e characte rs usefu l for particul ar biologic al contro l progra m mes. E uropean Studies In docum entin g geograp hica l distribu tion , the prevalen ce of specie s (i.e. whether particular specie s are com mon or rare) is an im portan t consider ation . For regulato ry purpose s, it is probably differen t to conte m plate releas e of a strain of a specie s w hich is indigen ous and dominan t compared w ith releasin g a strain of a specie s which is rare . W hile the questio n of prevale nce canno t be addresse d on a global basis becaus e of the scarcit y of survey s and henc e sm all sam ple sizes, it can start to be addresse d w ithin Europe . A s a result of the Europea n Union C ooperati on in the Field of Scienc e and Technica l Researc h (COST) Action 812 (Burnell et al., 1994 ) and its success or COST 819 on ento mopathog enic nem atodes , Europea n collabor ation is extensiv e and a number of survey s exist, both publishe d and unpubli shed . Thus, Europ e is the m ost intensiv ely surveye d regio n of the glob e for ento m opathog enic nem atodes and is the regio n for which most quantita tive data is availabl e. A grea t deal of variatio n in the prevale nce of ento mopathog enic nem atode s has been recorde d in Europea n soils and steinern ematid s predo minate com pare d with heterorh abditids . Hom inic k et al. (1995 ) used a sensitiv e hom ologou s rD NA prob e cloned from a steinern ematid to provid e unequiv ocal identific atio n of entom opathog enic nem atodes isolate d during survey s of the U K and the Netherlan ds. T he prevale nces of steinern em atid s that they reporte d (37±49% ) are the highes t docu mente d so far in norther n Europ e and are at least partly explaine d by their m ethod. In this, the soil in a negativ e assa y w as expose d to G alleria larvae for a secon d tim e becaus e nematode s frequen tly do not infec t in the first bioassa y (Hom inic k & Briscoe , 1990a,b ). O ther norther n Europea n survey s varie d w idely in the prevalen ce of steinern em atids, rangin g from 5.8% in Finlan d (V aÈ nnine n et al., 1989) to 10.4% in the R epubli c of Irelan d (Griffin et al., 1991), 18.3% in N orway (Haukelan d, 1993), 25% in Sweden (Burman et al., 1986), 26.5 % in the Sw iss A lps (Steiner, 1994 ) and 36.8% in C zechoslo vakia (M raÂcÏ ek, 1980). B oag et al. (1992 ) foun d that only 2.2% of 1014 sites in Scotlan d tested positive , and felt that this low recover y was a reflecti on of the cold climate in that country . Such a conclusi on is supporte d by data from a recen t surve y in wester n Canad a (M raÂcÏ ek & W ebster , 1993). Blacksha w (1988 ) reporte d a prevale nce of 3.8% in N orther n Ireland , althoug h the m ajority of the sample site s containe d clay type soils which consiste ntly yield low numbers of insect-p arasiti c nem atodes (H ominick & B riscoe , 1990a) . It thus appear s that the clim ate and soils of England , W ales and the Netherlan ds provid e excelle nt conditio ns for steinern em atid populati ons in particul ar. Heterorha bditids are rare in most Europea n surveys . This contrast s with a recen t quantitative surve y in New Jersey , U SA, w here heterorh abditids , probabl y H. bacterio phora, predo m inated over steinern em atid s (Stuart & G augler , 1994). H ominick and Brisco e (1990a ) and Steine r (1994) each found only one site positiv e for heteror habditid s. In their surve y of the R epubli c of Ireland , G riffin et al. (1991) also found only one heterorh abditid , which was isolate d from a coastal , sand y site. A subsequ ent survey of coasta l area s in Ireland , Scotlan d and W ales (Griffin et al., 1994) show ed that heterorh abditid s are m uch m ore com m on than previou sly indicate d, w ith prevale nces as high as 45% , but only w hen this particular habita t type is sampled . The secon d U K survey of Hominick et al. (1995 ) targete d sandy , coasta l soils within 1 km of the sea and yielde d tw o heterorh abditid isolates , at a prevalen ce highe r by an orde r of magnitud e compared with their first inlan d survey . H eterorha bditid s are frequen tly foun d in sites adjacen t to the sea (H ara et al., 1991; Poinar, 1993 ; Am arasingh e et al., 1994 ; Griffin et al., 1994), an associat ion that is intrigui ng and unexpla ined . A recent stud y on spider s living on barren island s in the G ulf of C aliforni a (Polis & Hurd, 1995 ) may be relevan t in the explanat ion. W ashed-u p m arine detritu s provide s a rich sourc e of nutrient s in the form of kelp and other algae and
EN TOM O PA THO G ENIC N EM ATO DES: B IOD IV ER SITY AND D ISTR IBU TIO N
325
carcass es of anim als, which suppor t larg e populations of insects which then suppor t larg e populat ions of spiders . Entom opathog enic nem atodes could flouris h equall y well unde r thes e conditi ons. H ow ever , a longe r distanc e from the sea does not preclud e the occurre nce of heteror habditid s, as Hominick et al. (1995 ) foun d that 13 of the 100 sites they sampled in the N etherlan ds yielde d heterorh abditid s even thoug h m ost of the site s were inland . The results of Stuar t and Gaugle r (1994) from N ew Jersey are sim ilar. W hen the nem atodes from norther n Europea n survey s have been identifie d, they have proved to be mostly S. feltiae . T his agrees with Hom inic k et al. (1995 ) w ho foun d that this specie s was the m ost com m on in the UK and the N etherlan ds. In additio n to the standar d R FLP type of S. feltiae , their survey s yielde d a furthe r R FLP varian t of this specie s foun d only in the UK , and six other species /RFLP types, one of w hich was S. affinis , one S. krausse i (designa ted B1; see R eid & Hom inick, 1993; H ominick et al., 1995 ) and som e of them new to science . Steine r (1994 ) surveye d the Swiss A lps and foun d S. affinis , S. interm edia, S. feltiae , S. krausse i and an isolate close to S. interm edia but with a distincti ve RFLP type . H e also reporte d that S. kraussei predo m inated in the alpin e environ ment while S. feltiae predom inated in the low er Alps. A lthough S. carpoca psae has been found in B ritis h soils (Georgis & Hague , 1981 , 1988), the extensi ve survey s reporte d abov e have neve r positive ly identifie d this species , so it m ust be rare in norther n Europea n localitie s. H abitat R ange The literatur e on habita t preferen ce for steinern ematids is, by and large , contradi ctory . This is m ainly due to the need for larg e sample sizes and accurat e identific atio n to m ake a meaningf ul assess ment of potentia l habita t preferen ces. M ost survey s yield insuffici ent data to test for correlat ions. H ow ever, H ominick et al. (1995 ) demonstrate d that at least som e steinern em atid species /strain s show a distinc t habita t preferen ce, w ith four out of five specie s (S. feltiae, S. kraussei , S. affinis and Steinern em a sp. B 3) foun d in sufficien t num bers and displayi ng signific ant associat ions w ith specifi c habita t types . Their pape r should be consult ed for details , but S. krausse i (B1) was most frequen tly foun d in woodland , S. feltiae and S. affinis were found in fields and verge s and B3 w as exclusiv e to woodland s. A nother specie s (Steinern ema sp. C1) also appeare d to show a habita t preferen ce for roadsid e verge s when data from a surve y by G wynn (1993) were combine d with that of H om inic k et al. (1995) . Steiner (1994 ) foun d no relation ship betw een vegetati on and the presenc e of S. kraussei , but did conclud e that S. feltiae, S. affinis and S. interm edia w ere typica l of grasslan d ecosyste m s. These habita t preferen ces m ay reflect the distribut ion of suitabl e hosts and lend suppor t to the grow ing opinio n that thes e nematode s are m ore restricte d in their natura l host range than laboratory infectio ns sugges t (see K aya & G augler , 1993). In addition , the variou s specie s w ill be physiolo gically and behaviourally adapte d so that their specifi c nich e require m ents are satisfie d only in particular habitats . Thus, Steine r (1994) reporte d that S. kraussei dom inated in soils with relativel y low pH values , w hile S. interm edia and S. feltiae avoide d extrem es of pH and S. affinis was confine d to a pH near neutralit y. Information from othe r Europea n survey s is m ore equivoc al. G riffin et al. (1991 ) found S. feltiae in w oodland , tille d fields , pastur e and roadsid e verges , w hile S. affinis was absent from w oodland . How ever, the prevalen ces were low and statistic al analyse s show ed no significa nt associat ions between nematod e occurre nce and habitat . Boag et al. (1992 ) found S. feltiae mostly in pastur e and absen t from heathlan d, but again prevale nces of less than 5% m ade it difficul t to draw firm conclus ions. So far, inform atio n on habita t specific ity for heterorh abditid s is dom inated by the correlat ion between m em bers of this fam ily and coasta l sandy soils (G riffin et al., 1994) . This observa tion has led to the hypothe sis that heterorh abditid s evolve d from marin e nem atodes and steinern em atid s from terrestri al nematode s (Poinar , 1993). The validit y of such a broa d generali zation awaits furthe r studies , but D NA analyse s and other m olecula r techniq ues have the potentia l to verify the possibili ty. One other relevan t stud y on habita t preferen ce of heterorh abditid s is that of Stuart and G augler (1994) . In their New Jerse y survey , they found that heterorh abditid s were
326
W . M . H OM INIC K ET AL .
equall y abundan t in turf and weedy habitats , but w ere absen t from closed-c anop y forest. This contrad icted a previou s survey and pointe d to the difficult ies of m akin g valid com parison s between survey s becaus e of the influenc e of many confoun ding and uncontr olled factors . The associat ion w ith the sea rem ains the most robus t correlati on betw een habita t and the presenc e of heteror habditid s. In all these correlati ons and associat ions w ith habitat s it is prevalen ce that is bein g assesse d and definitive statem ents should be m ade cautious ly. A m uch m ore critica l assess m ent require s m easure ment of populati on sizes and the spatial variabili ty of the nematodes . A s discusse d earlier , there is a samplin g proble m in that the distribut ion of ento mopathog enic nem atodes is highly aggrega ted at very low spatia l scales . H ence , sm all sam ple size s and chance can togethe r produc e misleadin g results . Using spatiall y structur ed sam plin g and large sam ple sizes J. M . M ason (unpubli shed) and S. Spirodon ov (unpubl ished ) both found that som e specie s of steinern em atid s do not progres s beyon d certain habita t boundar ies. J. M . M ason (unpubl ished ) found that the m ean densitie s of certain specie s change d from grasslan d to woodlan d sites. In Spirodon ov’ s surve y (unpubl ished) , particul ar specie s stoppe d at the canop y boundar y of a woodlan d site and w ere also associat ed with specifi c strata of soil. In any case , habita t specifici ty should not be surprisi ng as all organis m s have nich e require m ents that w ill be satisfie d only in particular habitats . It should now be apparen t that large sample sizes and accurat e identific ation s are necessar y befor e detaile d question s regardi ng geograp hica l and habita t specifici ty can be answered . The collecti on of such results require s a larg e amount of effor t which is beyon d the capabili ty of most individu als and laborato ries. H ow ever , if all the data collecte d globall y were put into a single databas e, the possibil ity for gainin g valuabl e insight s into the distribut ion of ento mopathog enic nematode s becom es realistic . Therefore , we have establis hed an ento mopathog enic nem atod e databas e, base d on our ow n extensi ve survey s and collabor ations . Questionn aire s are availabl e from us for individu als w ho would like to add their record s to ours, with confide ntialit y guarant eed if requeste d. W e emphasis e that we can only use data from site s w here the specie s of nem atod e was deter mined , even if som e doub t rem ains. Filling in a question naire for each sam ple will be laboriou s, as will enterin g the inform atio n into the databas e, but w e feel that the effort w ill be w orthw hile . For example, reliabl e inform atio n on habita t specific ity could be useful for biologic al contro l progra mm es. There m ay be little poin t in atte mptin g to contro l an insect pest in pastur e with a nematod e specie s foun d exclusiv ely in w oodland . The infor mation w ill also prov e invaluab le for regulato ry purpose s.
C ON VEN TION O N BIO LOG ICA L D IVE RSITY The U nite d Nations Conferen ce on the Environ m ent and Develop m ent (the E arth Sum mit) was held in Rio de Janeir o in June 1992 and produce d two internati onal treaties Ð the Conventi on on B iologica l Diversit y and the C onventio n on Clim ate Change . The Conventi on on Biologica l D iversit y was signe d by 153 countrie s and the Europea n Union , and cam e into effec t in D ecem ber 1993. It has now been ratifie d by over 100 countrie s and is a legally bindin g docu m ent. W hile it is beyon d the scop e of this paper to conside r the Conventi on in detail, accurat e identific atio n of organis m s and an understa ndin g of their biogeog raph y are funda m ental for its im plementation , and it is im portan t to be aware of the obligati ons that the Conventi on on B iologica l D iversit y imposes. T he Internat iona l Institut e of Biologica l Control (IIB C) has produce d a docu ment (Internat ional Institut e of Biologica l Control , 1994 ) to explain biologic al contro l w ithin the contex t of the Conventi on. It provide s the basis for som e of the follow ing discussi on. The objectiv es of the Conventi on are the conserva tion of biodiver sity , the sustaina ble use of its com ponent s and the equitabl e sharin g of benefit s arising from the utilizatio n of geneti c resourc es. B iologica l contro l require s continu ed, responsi ble exchang e of natura l enemies between countrie s, as well as in situ conserv atio n of natura l enem ies and their habitats . These
EN TOM O PA THO G ENIC N EM ATO DES: B IOD IV ER SITY AND D ISTR IBU TIO N
327
require m ents are em bodie d in variou s article s of the Conventi on, and therefor e the futur e of biologi cal contro l is intim ately linked to the Conventi on on Biologica l Diversity . The Conventi on has an im portan t role to play in ensurin g continui ng, globa l acces s to biologi cal diversit y for contro l of alie n pests. In Article 15.2, partie s to the C onventio n are asked to ª Endeavou r to create conditio ns to facilitat e acces s to geneti c resource s for environ m entally soun d uses by other Contracti ng Partiesº . B iologica l contro l agents are part of these geneti c resourc es and the Conventi on stipulate s that their collection should be carrie d out by mutual agree ment betw een partie s and that the party providin g these agents should do so in a contex t of prio r inform ed consent . In practice , this will m ean clos e cooperat ion betw een countrie s providin g and receivin g biologic al contro l agents , and it place s an even greate r respons ibility on intergov ernmental instituti ons such as IIBC and Food and Agricultu re Organizat ion (FAO ), w hich assist countri es in this process . The Conventi on has been signed into law, but in m any cases the fund s and officia l m echanis m s to implem ent and regulat e the Articles do not exist. For exam ple, in the contex t of this paper, much of the world has not been surveye d for entom opathog enic nem atodes , yet habitat s are continuo usly unde r threat. Loss of habitat s m eans loss of biodiver sity and loss of potentia lly usefu l species . The Convention require s contract ing parties to take actio n to improv e in situ conserv atio n of geneti c resource s throug h a broa d progra m m e of habita t conserv ation (Article 8). Few countri es have submitted nationa l plan s for protecti ng their biodiver sity and, for develop ing countri es, the questio n of who w ill pay is not resolve d. It is consiste nt w ith the C onventi on on B iologica l Diversit y that m aterial should not be collecte d from anothe r countr y w ithou t perm ission from that country ’ s appropri ate authorit y. This assu m es that an appropri ate authorit y exists, w hich m ay not always be the case . Sim ilarly , for materia l sent outsid e a country , it is im plie d that the sender has the perm issio n of the relevan t authorit ies to do so. Also, the receive r of the materia l should not m ake it availabl e to thir d parties withou t permission. H owever, for collabor ativ e scientifi c research , in which the biolog y of the organis m s is studie d to facilitat e their use in biological contro l progra mm es, the conditio ns m ay be perceive d as being differen t, and henc e third partie s could becom e involve d provide d they agreed to abid e by the C onventi on on Biologica l Diversity . It is clea r that the C onventio n is highly relevan t for w ork on ento m opathog enic nem atodes and for the practic e of biologic al contro l and that the issues are complicated . It is also clear that nationa l and internati onal agreem ents and regulati ons will be a long time in develop ing. It is not practica l to stop all internat iona l work or to restric t w ork to nationa l projects . In our opinion , the w ay forward is to be aware of the legal obligati ons of the C onventio n, and to operat e w ithin its spirit on a case-by -case basis, until agreem ents and the legal m achiner y necessar y to assure the im plem entatio n of the Conventi on are in place.
A CK NO W LEDG EM EN TS The author s are indebte d to a larg e num ber of colleagu es who provide d specim ens from their collecti ons and unpubli shed data and information , m akin g their netw ork truly international. Som e of this work w as support ed by contracts from the Agricultu ral Genetic s Com pany and by grants from the Agricultu re and Food Researc h C ouncil (now Biotechno logy and Biologica l Science s R esearc h C ouncil) . R EFEREN CES A KHURST , R.J. (1987) Use of starch gel electrophoresis in the taxonomy of the genus Heterorhabditis (Nematoda: Heterorhabditidae). Nematologica 33, 1±9. A M ARASING HE , L.D., H OMINIC K , W.M ., B RISCOE , B.R. & R EID , A.P. (1994) Occurrence and distribution of entomopathogenic nematodes (Rhabditida: Heterorhabditidae and Steinernematidae) in Sri Lanka. Journal of Helminthology 68, 277±286. B EDDING , R.A. & A KHURST , R.J. (1975) A simple technique for the detection of insect parasitic rhabditid nematodes in soil. Nematologica 21, 109±110.
328
W . M . H OM INIC K ET AL .
B ERRY , R.E. & L IU , J. (1996) Phylogenetic analysis of the genus Steinernema by morphological characters and random ampli® ed polymorphic DNA fragments. Fundamental and Applied Nematology (in press). B LACKSHAW , R.P. (1988) A survey of insect parasitic nematodes in Northern Ireland. Annals of Applied Biology 113, 561±565. B OAG , B., N EILSON, R. & G ORDON , S.C. (1992) Distribution and prevalence of the entomopathogenic nematode Steinernema feltiae in Scotland. Annals of Applied Biology 121, 355±360. B OVIEN , P. (1937) Some Types of Association between Nematodes and Insects. Videnskabelige M eddelelser fra Dansk Naturhistorisk Forening, Copenhagen, Denmark, 101, pp. 1±114. B URMAN , M ., A BRAHAM SSON, K., A SCARD , J., S JOÈ BERG , A. & E RIKSSON , B. (1986) Distribution of insect parasitic nematodes in Sweden, in Proceedings of the Fourth International Colloquium of Invertebrate Pathology (S AMSON , R.A., V LAK , J.M . & P ETERS , D., Eds) Society of Invertebrate Pathology, W ageningen, the Netherlands, p. 312. B URNEL L , A.M ., E HLERS , R.- U. & M ASSON , J.P. (Eds) (1994) COST 812 Biotechnology: Genetics of Entomopathogenic Nematode± Bacterium Complexes, Proceedings of Symposium and W orkshop, St Patrick’ s College, Maynooth, Co. Kildare, Ireland. European Commission, DG XII, Luxembourg. C ABANIL LAS , H.E., P OINAR , G.O., J R . & R AUSTON , J.R. (1994) Steinernema riobravis sp. nov. (Rhabditida: Steinernematidae) from Texas. Fundamental and Applied Nematology 17, 123±131. C HOO , H.Y., K AYA , H.K. & S TOCK , S.P . (1996) Isolation of entomopathogenic nematodes (Steinernematidae and Heterorhabditidae) from Korea. Japanese Journal of Nematology (in press). C URRAN , J. & D RIVER , F (1994) M olecular taxonomy of Heterorhabditis, in COST 812 Biotechnology: Genetics of Entomopathogenic Nematode± Bacterium Complexes, Proceedings of Symposium and Workshop, St Patrick’ s College, Maynooth, Co. Kildare, Ireland (B URNELL , A.M., E HLERS , R.U. & M ASSON , J.P., Eds) European Commission, DG XII, Luxembourg, pp. 41±48. C URRAN , J. & H ENG , J. (1992) Comparison of three methods for estimating the number of entomopathogenic nematodes present in soil samples. Journal of Nematology 24, 170±176. C URRAN , J. & W EBSTER , J.M . (1989) Genotypic analysis of Heterorhabditis isolates from North Carolina, USA . Journal of Nematology 21, 140±147. D IX , I., B URNELL , A.M ., G RIFFIN , C.T ., J OYCE , S.A., N UGE NT , M.J. & D OWNE S, M .J. (1992) The identi® cation of biological species in the genus Heterorhabditis (Nematoda: Heterorhabditidae) by breeding second generation amphimictic adults. Parasitology 104, 509±518. D E D OUCET , M.M.A . (1986) A new species of Neoaplectana Steiner 1929 (Nematoda: Steinernematidae) from Cordoba, Argentina. Revue de Nematology 9, 317±323. D E D OUCET , M.M .A. & D OUCET , M .E. (1990) Steinernema ritteri n. sp. (Nematoda: Steinernematidae) with a key to the species of the genus. Nematologica 36, 257±265. D E D OUCET , M.M .A. & G ABARRA , R. (1994) On the occurrence of Steinernema glaseri (Steiner, 1929) (Steinernematidae) and Heterorhabditis bacteriophora Poinar, 1976 (Heterorhabditidae) in Catalogne, Spain. Fundamental and Applied Nematology 17, 441±443. E HLERS , R.- U. & P E TERS , A. (1995) Entomopathogenic nematodes in biological control: feasibility, perspectives and possible risks, in Biological Control: Bene® ts and Risks (H OKKANE N , H.M .T. & L YNCH , J.M ., Eds) Cambridge University Press, Cambridge, pp. 113±136. E HLERS , R.-U., D E SEOÈ , K.V. & S TACKE BRAND T , E. (1991) Identi® cation of Steinernema spp. (Nematoda) and their symbiotic bacteria Xenorhabdus spp. from Italian and German soils. Nematologica 37, 360±366. F AN , X. (1989) Bionomics of British strains of entomopathogenic nematodes (Steinernematidae). PhD thesis, Imperial College, University of London, UK. F ARGE TTE, M., B LOK , V.C., P HILLIPS , M.S. & T RUDGILL , D.L. (1994) Genetic variation in tropical M eloidogyne species, in Advances in M olecular Plant Nematology (L AMBERT I, F., D E G IORGI , C. & B IRD . D. M C K., Eds) Plenum Press, New York, NY, pp. 91±96. F ILIPJEV, I.N. (1934) Micellanea Nematologica 1. Eine neue Art der Gattung Neoaplectana Steiner nebst Bemerkungen uÈ ber die systematische Stellung der letzteren. Magazine de Parasitologie de l’ Institut Zoologique de l’ Academie de l’ USSR 4, 229±239. G ARDNER , S.L., S TOCK , S.P. & K AYA , H.K . (1994) A new species of Heterorhabditis from the Hawaiian islands. Journal of Parasitology 80, 100±106. G E ORGIS , R. & H AGUE , N.G.M . (1981) A neoaplectanid nematode in the larch saw¯ y Cephalcia lariciphila (Hymenoptera: Pamphiliidae). Annals of Applied Biology 99, 171±177. G E ORGIS , R. & H AGUE , N.G.M . (1988) Field evaluation of Steinernema feltiae against the web-spinning larch saw¯ y Cephalcia lariciphila. Journal of Nematology 20, 213±320. G L AZER , I., L IRAN , N., P OINAR , G.O. J R . & S MIT S , P.H . (1993) Identi® cation and biological activity of newly isolated heterorhabditid populations from Israel. Fundamental and Applied Nematology 16, 467±472. G OUGE , D.H. & H AGUE , N.G.M . (1995) The susceptibility of sciarid ¯ ies to entomopathogenic nematodes. Journal of Helminthology 69, 313±318. G RIFFIN , C.T ., D OWNES , M.J. & B LOCK , W . (1990) Tests of Antarctic soils for insect parasitic nematodes. Antarctic Science 2, 221±222. G RIFFIN , C.T., M OORE , J.F. & D OWNE S, M.J. (1991) Occurrence of insect-parasitic nematodes (Steinernematidae, Heterorhabditidae) in the Republic of Ireland. Nematalogica 37, 92±100.
EN TOM O PA THO G ENIC N EM ATO DES: B IOD IV ER SITY AND D ISTR IBU TIO N
329
G RIFFIN , C.T., J OYCE , S.A., D IX , I., B URNE LL , A.M. & D OWNE S, M .J. (1994) Characterisation of the entomopathogenic nematode Heterorhabditis (Nematoda: Heterorhabditidae) from Ireland and Britain by molecular and cross-breeding techniques, and the occurrence of the genus in these islands. Fundamental and Applied Nematology 17, 245±254. G W YNN , R.L. (1993) Development of cold active nematodes for insect control. PhD thesis, University of Reading, UK. H ARA , A.H., G AUGLER , R., K AYA , H.K. & L E BECK , L.M. (1991) Natural populations of entomopathogenic nematodes (Rhabditida: Heterorhabditidae, Steinernematidae) from the Hawaiian islands. Environmental Entomology 20, 211±216. H AUKE LAND , S. (1993) Entomopathogenic nematodes found in Norway. Norwegian Journal of Agricultural Sciences 7, 17±27. H OMINIC K , W.M . & B RISCOE , B.R. (1990a) Survey of 15 sites over 28 months for entomopathogenic nematodes (Rhabditida: Steinernematidae). Parasitology 100, 289±294. H OMINIC K , W .M. & B RISCOE , B.R. (1990b) Occurrence of entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) in British soils. Parasitology 100, 295±302. H OMINIC K , W.M . & R EID, A.P. (1990) Perspectives on entomopathogenic nematology, in Entomopathogenic Nematodes in Biological Control (G AUGLER , R. & K AYA , H.K., Eds) CRC Press, Boca Raton, FL, 327±345. H OMINIC K , W .M ., R EID , A.P. & B RISCOE , B.R. (1995) Prevalence and habitat speci® city of steinernematid and heterorhabditid nematodes isolated during soil surveys of the UK and the Netherlands. Journal of Helminthology 69, 27±32. I NT ERNAT IONAL I NSTITUTE OF B IOLOGICAL C ONTROL (1994) Using Biodiversity to Protect Biodiversity. Biological Control, Conservation and the Biodiversity Convention. CAB International, W allingford, p. 14. J ACKSON , G.J. (1965) Differentiation of three species of Neoaplectana (Nematoda: Rhabditida), grown axenically. Parasitology 55, 571±578. J OYCE , S.A., B URNE LL , A.M . & P OWE RS , T.O. (1994a) Characterisation of Heterorhabditis isolates by PCR ampli® cation of segments of mtDNA and rDNA genes. Journal of Nematology 26, 260±270. J OYCE , S.A., R EID , A., D RIVER , F. & C URRAN , J. (1994b) Application of polymerase chain reaction (PCR) methods to the identi® cation of entomopathogenic nematodes, in COST 812 Biotechnology: Genetics of Entomopathogenic Nematode± Bacterium complexes, Proceedings of Symposium and Workshop, St Patrick’ s College, Maynooth, Co. Kildare, Ireland (B URNELL , A.M ., E HLE RS , R. -U. & M ASSON , J.P., Eds) European Commission, DG XII, Luxembourg, pp. 178±187. K AYA , H.K. & G AUGLE R , R. (1993) Entomopathogenic nematodes. Annual Review of Entomology 38, 181±206. K OZ ODOI , E.M. (1984) A new entomophagous nematode Neoaplectana anomali sp. n. (Rhabditida: Steinernematidae) and its biology. Zoologicheskii Zhurnal 63, 1605±1909. L I, X.F. & W ANG , G.H . (1989) Preliminary investigation on the distribution of Steinernematidae and Heterorhabditidae in Fujian, Guangdong and Hainan. Chinese Journal of Zoology 24, 1±4. L UI, J. (1992) Taxonomic study of the genus: Steinernema Travassos and Heterorhabditis Poinar, in Proceedings of the XIX International Congress of Entomology, Beijing, China, p. 318. M AMIYA , Y. (1988) Steinernema kushidai n. sp. (Nematoda: Steinernematidae) associated with scarabaeid beetle larvae from Shizuoka, Japan. Applied Entomology and Zoology 23, 313±320. M RAÂCÏ EK , Z. (1980) The use of `Galleria traps’ for obtaining nematode parasites of insects in Czechoslovakia (Lepidoptera: Nematoda, Steinernematidae). Acta Entomologica Bohemoslovaca 77, 378±382. M RAÂCÏ EK , Z. (1994) Steinernema kraussei (Steiner 1923) (Nematoda: Rhabditida: Steinernematidae): redescription of its topotype from W estphalia. Folia Parasitologica 41, 59±61. M RAÂCÏ EK , Z. & J ENSEN , G. (1988) First report of emomogenous nematodes of the families Steinernematidae and Heterorhabditidae from Hungary. Acta Phytopathologica et Entomologica Hungarica 23, 153±156. M RAÂCÏ EK , Z. & W EBSTER , J.M . (1993) Survey of Heterorhabditidae and Steinernematidae (Rhabditida, Nematoda) in western Canada. Journal of Nematology 25, 710±717. M RAÂCÏ EK , Z., G UT , J. & G ERDIN , S. (1982) Neoaplectana bibionis Bovien 1937, an obligate parasite of insects isolated from forest soil in Czechoslovakia. Folia Parasitologica 29, 139±145. M RAÂCÏ EK , Z., H ERNAND EZ , E.A. & B OEMARE , N.E. (1994) Steinernema cubana sp. n. (Nematoda: Rhabditida: Steinernematidae) and the preliminary characterisation of its associated bacterium. Journal of Invertebrate Pathology 64, 123±129. M RAÂCÏ EK , Z., W E ISER , J., B URES , M . & K AHOUNO VA , L. (1992) Steinernema kraussei (Steiner, 1923) (Nematoda: Rhabditida)Ð rediscovery of its type locality in Germany. Folia Parasitologica 39, 181±199. N GUYE N , K.B. & S MART , G.C., J R . (1990) Steinernema scapterisci n. sp. (Rhabditida: Steinernematidae). Journal of Nematology 23, 187±199. N GUYE N , K.B. & S MART , G.C., J R . (1992) Steinernema neocurtillis n. sp. (Rhabditida: Steinernematidae) and a key to the genus Steinernema. Journal of Nematology 24, 463±477. N GUYE N , K.B. & S MART , G.C., J R . (1994) Neosteinernema longicurvicauda n. gen., n. sp. (Rhabditia: Steinernematidae), a parasite of the termite Reticulitermes ¯ avipes (Koller). Journal of Nematology 26, 162±174. O PPERMAN , C.H., D ONG , K. & C HANG , S. (1994) Genetic analysis of the soybean±Heterodera glycines interaction, in Advances in Molecular Plant Nematology (L AMBE RT I, F., D E G IORGI , C. & B IRD . D. M C K., Eds) Plenum Press, New York, NY, pp. 65±67.
330
W . M . H OM INIC K ET AL .
P ARKM AN , J.P. & S MART , G.C. (1996) Entomopathogenic nematodes, a case study: introduction of Steinernema scapterisci in Florida. Biocontrol Science and Technology 6, 413±419. P ETERS , A. (1996) The natural host range of Steinernema and Heterorhabditis spp. and their impact on insect populations. Biocontrol Science and Technology 6, 389±402. P IZANO , M.A., A GUILERA , M .M ., M ONTEIRO , A.R . & F E RROY , L.C. (1985) Incidenciade Neoaplectana glaseri Steiner, 1929 (Nematoda: Steinernematidae) parasitando ovo de Mygdolus frynus (Westwood 1863) (Col: Cerambycidae), in Proceedings of the Ninth M eeting of the Society of Brasilian Nematology, Piracicaba, Brazil, pp. 9±10. P OINAR , G.O., J R (1976) Description and biology of a new insect parasitic rhabditoid, Heterorhabditis bacteriophora n. gen. n. sp. (Rhabditida: Heterorhabditidae N. Fam.). Nematologica 21, 463±470. P OINAR , G.O., J R (1985) Neoaplectana intermedia n. sp. (Steinernematidae: Nematoda) from South Carolina. Revue de NeÂmatologie 8, 321±327. P OINAR , G.O., J R (1986) Recognition of Neoaplectana species (Steinernematidae: Rhabditida). Proceedings of the Helminthological Society of Washington 53, 121±129. P OINAR , G.O., J R (1988) Redescription of Neoaplectana af® nis Bovien (Rhabditida: Steinernematidae). Revue de NeÂmatologie 11, 143±147. P OINAR , G.O., J R (1990) Taxonomy and biology of Steinernematidae and Heterorhabditidae, in Entomopathogenic Nematodes in Biological Control (G AUGLE R , R. & K AYA , H.K., Eds), CRC Press, Boca Raton, FL, pp. 23±61. P OINAR , G.O., J R (1992) Steinernema feltiae (Steinernematidae: Rhabditidae) parasitizing adult fungus gnats (Mycetophilidae: Diptera) in California. Fundamental and Applied Nematology 15, 427±430. P OINAR , G.O., JR (1993) Origins and phylogenetic relationships of the entomophilic rhabditids, Heterorhabditis and Steinernema. Fundamental and Applied Nematology 16, 332±338. P OINAR , G.O., J R & G EORGIS, R. (1990) Description and ® eld application of the HP88 strain of Heterorhabditis bacteriophora. Revue de NeÂmatologie 13, 387±393. P OINAR , G.O., J R & K OZ ODOI , E.M . (1988) Neoaplectana glaseri and N. anomali: sibling species or parallelism? Revue de NeÂmatologie 11, 13±19. P OINAR , G.O., J R & L INDHARD T , K. (1971) The re-isolation of Neoaplectana bibionis Bovien (Nematoda) from Danish Bibionids (Diptera) and their possible use as biological control agents. Entomologica Scandinavica 2, 301±303. P OINAR , G.O., J R , J ACKSON , T. & K LEIN , M. (1987) Heterorhabditis megidis sp. n. (Heterorhabditidae: Rhabditida), parasitic in the Japanese beetle, Popillia japonica (Scarabidae: Coleoptera), in Ohio. Proceedings of the Helminthological Society of Washington 53, 53±59. P OINAR , G.O., J R , K ARUNAK AR , G.K. & D AVID , H. (1992) Heterorhabditis indicus n. sp. (Rhabditida: Nematoda) from India: separation of Heterorhabditis spp. by infective juveniles. Fundamental and Applied Nematology 15, 467±472. P OLIS , G.A. & H URD , S.D . (1995) Extraordinarily high spider densities on islands: ¯ ow of energy from marine to terrestrial food webs and the absence of predation. Proceedings of the National Academy of Sciences 92, 4382±4386. P OWE RS , T.O., & H ARRIS , T.S. (1993) A polymerase chain reaction method for the identi® cation of ® ve major Meliodogyne species. Journal of Nematology 25, 1±6. R EID , A.P . (1994) Molecular taxonomy of Steinernema, in COST 812 Biotechnology: Genetics of Entomopathogenic Nematode± Bacterium Complexes, Proceedings of Symposium and W orkshop, St Patrick’ s College, Mamooth, Co. Kildare, Ireland (B URNELL , A.M., E HLE RS , R.-U. & M ASSON , J.P., Eds) European Commission, DG XII, Luxembourg, pp. 49±58. R EID , A.P. & H OMINICK , W .M . (1993) Cloning of the rDNA repeat unit from a British entomopathogenic nematode (Steinernematidae) and its potential for species identi® cation. Parasitology 107, 529±536. S ANDNER , H. & B EDNARE K , A. (1987) Entomophilic nematodes in the Swietokrzyski National Park. Fragmenta Faunistica 31, 3±9. S HEN , C.P. (1992) Description of a entomopathogenic nematode, Steinernema longicaudum sp. nov. and its application, in Proceedings of the 19th International Congress of Entomology, Beijing, China, pp. 220±231. S MIT S, P.H., G ROE NEN , J.T.M . & D E R AAY , G. (1991) Characterisation of Heterorhabditis isolates using DNA restriction fragment length polymorphisms. Revue de NeÂmatologie 14, 445±453. S TEINER, G. (1923) Aplectana kraussei n. sp., eine in der Blattwespe Lyda sp. parasitierende Nemodenform, nebst Bemerkungen uÈ ber das Seitenorgan der parasitischen Nematoden. Zentralblatt fuÈr Bakteriologie, Parasitenkunde, Infektions, Krankheiten und Hygiene, Abteilung II 59, 14±18. S TEINER, G. (1929) Neoaplectana glaseri n. g. n. sp. (Oxyuridae), a new nemic parasite of the Japanese beetle (Popillia japonica, NEW M). Journal of the W ashington Academy of Science 19, 436±440. S TEINER, W.A. (1994) Distribution of entomopathogenic nematodes in the Swiss Alps, in COST 812 Biotechnology: Genetics of Entomopathogenic Nematode± Bacterium Complexes, Proceedings of Symposium and Workshop, St Patrick’ s College, M aynooth, Co. Kildare, Ireland (B URNELL , A.M., E HLERS , R. -U. & M ASSON , J.P., Eds) European Commission, DG XII, Luxembourg, p. 218. S TOCK , S.P . (1992) Presence of Steinernema scapterisci Nguyen & Sm art parasitizing the mole cricket Scapteriscus borellii in Argentina. Nematologia Mediterranea 20, 163±165.
EN TOM O PA THO G ENIC N EM ATO DES: B IOD IV ER SITY AND D ISTR IBU TIO N
331
S TOCK , S.P . (1993a) Description of an Argentinian strain of Steinernema feltiae (Filipjev, 1934) (Nematoda: Steinernematidae). Nematologia M editerranea 21, 279±283. S TOCK , S.P. (1993b) A new species of the genus Heterorhabditis Poinar, 1976 (Nematoda: Heterorhabditidae) parasitizing Graphognathus sp. larvae (Coleoptera: Curculionidae) from Argentina. Research and Reviews in Parasitology 53, 103±107. S TUART , R.J. & G AUGL ER , R. (1994) Patchiness in populations of entomopathogenic nematodes. Journal of Invertebrate Pathology 64, 39±45. T ALLOSI, B., P ETERS, A. & E HLERS , R.-U. (1995) Steinernema bicornutum sp. n. (R habditida: Nematoda) from Vojvodina, Yugoslavia. Russian Journal of Nematology, 3, 71±80. V AÈ NNINEN , I., H USBERG , G.-B. & H OKKANE N , M .T. (1989) Occurrence of entomopathogenic fungi and entomoparasitic nematodes in cultivated soils in Finland. Acta Entomologica Fennica 53, 65±71. V RAIN , T.C ., W AKARCH UK , D.A., L EVESQUE , A.C. & H AMIL TON , R.I. (1992) Intraspeci® c rDNA restriction fragment length polymorphisms in the Xiphinema americanum group. Fundamental and Applied Nematology 15, 563±574. W ALTHER , B.A., C OTGREAVE , P., P RICE , R.D., G RE GORY , R.D. & C L AYTON , D.H . (1995) Sampling effort and parasite richness. Parasitology Today 11, 306±310. W EISER , J. (1955) Neoaplectana carpocapsae n. sp. (Anguillulata, Steinernematidae) novy cizopasnik housenik obalece jablecneÂho, Carpocapsa pomonella L. Vestnik Ceskoslovenske Zoologicke Spolecnosti 19, 44±52. W ELSH , J. & M C C LELLAND , M. (1990) Fingerprinting genomes with PCR using arbitrary primers. Nucleic Acids Research 18, 7213 ±7218. W ILLIAMS , J.G.K., K UBELIK , A.R., L IVAK , K.J., R AFOLSKI, J.A. & T INGE Y , S.V . (1990) DNA polymorphisms ampli® ed by arbitrary primers are useful as genetic markers. Nucleic Acids Research 18, 6351±6535. X U , Z., W ANG , G. & L I, X. (1991) A new species of the genus Steinernema (Rhabditida: Steinernematidae). Zoological Research 12, 17±20.
