Litoria gracilenta - CSIRO Publishing

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Australian Journal of Zoology, 2004, 52, 191–214

Litoria gracilenta (Anura:Hylidae) and related species in New Guinea J. I. MenziesA,B and M. J. TylerA A Department of Environmental Biology, University of Adelaide, Adelaide, SA 5005, Australia. B To whom correspondence should be addressed. Email: [email protected]

Abstract We examined a large collection (n = 132) of tree frogs, hitherto identified as Litoria gracilenta, from various localities in New Guinea and compared them with Litoria gracilenta from Queensland and with the recently described Litoria elkeae from far west New Guinea. We found that the frogs in question were neither L. gracilenta nor L. elkeae but comprised two distinct taxa described herein as new species. We call attention to the problems of performing statistical analysis on measurements of soft-bodied organisms and consider that the conclusions reached in this analysis are both conservative and realistic. ZO0308 .JLIit.roMieangizarescilanedtM.a nJ.dTreyleatdr speceisin NewGuiena

Introduction The occurrence of Litoria gracilenta (Peters) (as Hyla gracilenta) in New Guinea was first recorded by Tyler (1968) on the basis of three specimens from a locality near Tari, in the Southern Highlands Province of Papua New Guinea at an altitude of ~1500 m. Prior to this date, the species was known to occur only in the lowland coastal fringe of eastern Australia from New South Wales north to Cape York (see Cogger 2000 for distribution in Australia). The type locality is Port Mackay (=Mackay) in central Queensland. Tyler (1968) expressed surprise that a lowland Australian species should occur in the mountains of New Guinea. In the same volume, Tyler included an account of another small green tree frog, Litoria aruensis (Horst), known from scattered lowland localities in the New Guinea region from Misool Island in the west to Rossel Island in the far east. These localities are shown in Fig. 1. Although the dimensions and proportions of the one species completely enclosed those of the other, Tyler did not compare them or suggest any possibility of synonymy. However, the illustrations (figs 12 and 30) clearly indicate differences in head shape and finger webbing. Menzies (1976) reported a much wider geographic distribution of L. gracilenta in New Guinea, with locality records from Daru on the southern coast through the coastal lowlands to the Southern Highlands Province, and suggested that L. aruensis was a junior synonym of L. gracilenta. This amalgamation would have given L. gracilenta one of the most extensive distributions of any Australo-Papuan congener, from the temperate lowlands of northern New South Wales through the wet and seasonally dry tropics to the highlands of New Guinea, and from the Aru Islands and Misool in the west to the eastern Papuan Islands in the east. Menzies’ conclusions were based on morphological similarity and the similarity in male vocalisation in frogs recorded at several different localities in Australia and New Guinea. More recently, Günther and Richards (2000) described Litoria elkeae from a lowland locality, the Wapoga River, in west New Guinea (Papua, formerly Irian Jaya, Indonesia), © CSIRO 2004

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J. I. Menzies and M. J. Tyler

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Fig. 1. Records of Litoria gracilenta, s.l. in (a) New Guinea, Australia and nearby Islands and (b) central area of New Guinea, enlarged. Solid circles denote localities of specimens used in the analysis, crosses denote collection localities of other specimens examined by the authors but not used. Contour line at 1000 m in (a), 1000 and 2000 m (dotted) in (b). 1, Misool; 2, Waigeo Island; 3, Tehak; 4, Aru Island; 5, Wapoga River; 6, Alkmaar; 7, Ok Ma; 8, Mt Sisa (Bobole and Namosado); 9, Tari, 10, Komo; 11, Nipa; 12, Balimo; 13, Daru Island; 14, Karimui; 15, Haia; 16, McDowell Island, Purari River; 17, localities on the Pio River; 18, Rossel Island; 19 Sudest Island; 20, unspecified localities in Queensland, Australia.

Litoria gracilenta and related species in New Guinea

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comparing it with specimens of Australian gracilenta and noting the difference in call structure but general similarity in size (though somewhat smaller) and colouration. They also made comparison with a small sample of gracilenta-like frogs from two middle-altitude locations in eastern New Guinea: Ok Tedi in the upper Fly River and Heroana in the middle reaches of the Purari River (Fig. 1). They noted that the New Guinea examples had larger eyes than those from Australia do and concluded, on this limited evidence, that gracilenta-like frogs in New Guinea were not conspecific with those of Australia. They made no specific designation for the Ok Tedi or Heroana frogs beyond concluding that they were neither elkeae nor gracilenta. This is clearly an unsatisfactory situation for it leaves a common species without a name or a diagnosis. This taxonomic ambiguity has prompted the present study. Günther and Richards (2000) also examined the syntypes of Litoria aruensis and noted, inter alia, that they had green bones, which immediately distinguished them from gracilenta or elkeae. The occurrence of green bones is widespread, though uncommon, in frogs (Barrio 1965) and has been noted previously for two Papuan species, Litoria lutea and L. thesaurensis, neither of which is related to the gracilenta-group. No new material of Litoria aruensis has come to light in recent years, call data are lacking and the three syntypes came from two distant islands so may not even be conspecific. No green colour has been detected in the bones of any specimens other than the syntypes. Materials and Methods We based our analysis on a collection of 132 specimens of gracilenta-like frogs from several different localities. These localities include six lowland and highland sites in New Guinea (n = 4–27) and one group from coastal Queensland (n = 25) from various places between Brisbane and Cairns but no more than three from any one locality. We also had access to data on several other groups of gracilenta-like frogs, including the syntypes of L. aruensis, and these data have been included in our statistical analyses. Table 1 defines the eleven variables (sex, HB, TL, HL, HW, EN, IN, EY, TY, f3d and t4d) that were recorded from each specimen. A list of all specimens examined, the range of dimensions and locality data is given in Appendices 1–3. Statistical analyses taken from the software packages JMP (Sall et al. 1996) and SPSS (SPSS Inc. 1983) were used in the analyses. Field recordings of male vocalisation were made with several different models of tape recorders and microphones and were analysed with the programme ‘Avisoft’ (Specht 2003). Institutional abbreviations used in the text and appendix are as follows: AMNH, American Museum of Natural History, New York; RMNH, Rijksmuseum of Natural History, Leiden; SAM, South Australian Museum, Adelaide; SR, Steven Richards, personal collection; UP, University of Papua New Guinea, Port Moresby; ZMB, Zoologisch Museum der Humboldt Universität, Berlin.

Table 1.

Body dimensions of Litoria gracilenta s.l. used in the analyses

Code

Definition

HB TL

Head+body length: from the tip of the snout to the distal end of the urostyle Tibial length: external distance between knee and ankle with the knee and ankle joints held at right angles Head length between the tip of the snout and the jaw articulation Head width at mid-tympanic level Distance between the anterior margin of the eye and centre of the nostril Distance between the nostrils, centre to centre Horizontal eye diameter Tympanic diameter (not used in final analyses) Horizontal diameter of the disk on 3rd finger Horizontal diameter of the disk on 4th toe

HL HW EN IN EY TY f3d t4d

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In this paper ‘New Guinea’ refers to the whole island, comprising (western half) the Indonesian Province of Papua (formerly Irian) and (eastern half) Papua New Guinea. Localities are identified by the Regency (if in Papua) or Province (if in Papua New Guinea). Adult frogs were defined by the presence of vocal sacs and pigmented nuptial pads in males or by the presence of maturing ova in females.

Results Preliminary morphometric analyses We plotted the distribution of head+body size (HB) and the ratios TL:HB, HL:HB, HL:HW, EN:IN, EY:HB in order to determine whether there were any differences between males and females. In each population females, on average, were slightly larger than males but with all populations combined there was no significant difference in size (Fig. 2a). There were no differences between male and female regression lines (Fig. 2b–f). However, relatively few females were available and statistical differences between sexes in these tests must be accepted with caution. Sexual dimorphism was ignored in the next two analyses. The correlation of all variables with head+body length was then plotted to reveal any outliers and to indicate which variables were likely to give significant results in subsequent analyses. This was done for each geographical group separately. Results are shown in Table 2. The ratio TY:HB gave a non-significant correlation in five of the seven groups and may have been due to the difficulty of accurately measuring the tympanic diameter when it is often not well defined. Tympanic diameter was eliminated from subsequent analyses. All other variables revealed a significant correlation in at least four of the seven groups. Small sample size in several groups may have been responsible for non-significant results. Data for all specimens then underwent a cluster analysis, without a priori designation of group membership, in order to determine the homogeneity of the geographic groups. Initial analyses used raw data but males and females from the same group tended to cluster separately, suggesting that size was biasing the result. The data were then transformed (standardised) and the analysis repeated but this produced no clear group structure, with lowland and highland examples mixed, suggesting no differences other than size. Data transformation was therefore abandoned. Analysis using raw data produced two primary clusters (Fig. 3). The upper cluster in Fig. 3 includes only 18 specimens (13 males, 5 females) from highland localities. The second cluster includes 39 specimens from lowland (New Guinea and Queensland) and intermediate (Haia, 1100 m) localities plus 12 females from the mountains. Fifteen specimens showed no close relationship to either of the two primary clusters. Eight of these were from Queensland, two from New Guinea highlands and five from New Guinea lowlands. These specimens were re-examined and found to be either poorly preserved, immature or, for some reason, difficult to measure accurately. Final analyses These analyses were designed to resolve several questions. (a) Can all gracilenta-like frogs from all localities in New Guinea be considered conspecific with L. gracilenta? (b) If the frogs from the New Guinea highlands and lowlands are different, are the lowland frogs Litoria gracilenta s.s.? (c) Can any of the lowland frogs be allied to L. elkeae? (d) Where does Litoria aruensis (including frogs from the Louisiade Islands) fit into the gracilenta group?


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Fig. 2. Litoria gracilenta s.l. (a) head+body size and (b-f) linear regressions of various body ratios in males (m) and females (f).

To establish the conditions necessary for continuing the analyses, all variables from each group were tested separately for normal distribution. All but Groups 3 and 9 were significant for normality (Kolmogorov–Smirnov test) in most variables. Those two groups were too small to be tested. All specimens, males and females together, were then subjected to a discriminant analysis. The first three discriminant axes contained a significant proportion of the between-groups variance (significant Wilks’ λ) and the first two axes

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Table 2.

Correlation of body parameters with head+body (HB) length in seven groups of Litoria gracilenta s.l. See Table 1 for definitions of body parameters. n.s., not significant; *, P < 0.05; **, P < 0.01

TL v. HB HL v. HB HW v. HB EN v. HB IN v. HB EY v. HB TY v. HB f3d v. HB t4d v. HB

Group 1 Nipa (n = 6)

Group 2 Komo (n = 5)

Group 3 Haia (n = 4)

Group 4 Tari (n = 23)

Group 5 Purari R. (n = 8)

Group 6 Daru (n = 27)

Group 7 Queensland (n = 25)

** ** ** n.s. ** ** n.s. ** **

n.s. * n.s. n.s. n.s. n.s. n.s. n.s. n.s.

* n.s. n.s. n.s. n.s. n.s. n.s. n.s. n.s.

** ** ** ** ** ** ** ** **

** ** ** ** n.s. n.s. n.s. ** n.s.

** ** ** ** ** ** ** n.s. n.s.

** ** ** ** ** ** n.s. ** **

accounted for 87% of the between-groups variance. Head+body length, eye size, eye–naris distance and tibial length carried most weight in the first axis whereas head+body length and head length, eye–naris distance, third finger disk diameter and inter-narial distance carried most weight in the second. Fig. 4a plots the positions of the group centroids and their 95% confidence limits. The highlands groups (1, 2 and 4) fall to the lower side of the figure, the lowland groups (5 and 6) to the top and Queensland to the right. It should be noted that Levene’s test for homogeneity of variances was not satisfied in all groups in this analysis but the result of Box’s test for equality of covariance matrices was significant and we felt justified in proceeding. In view of the size difference between males (smaller) and females (larger) and the weight given by body size in Discriminant Axes 1 and 2, it was clearly necessary to base further analyses on single-sex groups. Fig. 4b is a plot of group centroids using male frogs only and here the separation of highland and lowland groups is much wider. The largest contribution to the first axis now is from head width and length, head+body length and tibial length while the second axis derives most from eye–naris distance and tibial length. The three highland groups were then combined and the analysis repeated with added data on Litoria elkeae taken from Günther and Richards (2000), syntypes of L. aruensis and a small collection from the Louisiade Islands listed as aruensis by Tyler (1968). Because data on disk size were not available for the Louisiade frogs measured by Tyler, variables f3d and t4d were omitted from this analysis. The position of the male syntype of L. aruensis was calculated and fitted to the figure by hand. Fig. 4c displays the results and indicates five distinct clusters. These are: (1) the highland groups numbered 1, 2 and 4; (2) L. elkeae, numbered 9; (3) lowland groups numbered 3, 5 and 6; (4) L. gracilenta s.s., numbered 7, from Queensland; and (5) a fifth group, numbered 8, from the Louisiade Islands, which occupies a distant position, as does the male syntype of L. aruensis (HT) although that comes closer to the Louisiade group than to any other. Characters now carrying most weight on the first axis are head width and length, head+body size and eye diameter and, on the second axis, eye–naris distance, tibial length and, again, eye diameter and head width. All groups except 3 and 5 were significantly distant from one another. To ascertain the most useful variables for distinguishing between groups, we then plotted male head+body size and the ratios TL:HB, HL:HB, EN:HB, EN:IN and EY:HB, with t-tests, for


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Fig. 3. Cluster analysis (% similarity) of specimens of Litoria gracilenta s.l. from Australia and New Guinea. Circles, montane frogs; squares, New Guinea lowland frogs; triangles, Queensland frogs; open figures, male, solid figures, female.

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Fig. 4. Discriminant analysis on specimens of Litoria gracilenta s.l. for (a) males and females, and (b, c) males only. Solid circles denote groups’ centroids, ellipses are 95% confidence limits. Place: 1, Nipa; 2, Komo; 3, Haia; 4, Tari; 5, Daru; 6, Purari; 7, Queensland; 8, Louisiade; 9, Litoria elkeae. HT, syntype of Litoria aruensis.

all variables between all groups (Fig. 5a–f). Highland frogs (Group 1) are significantly smaller than all others (Fig. 5a) but do not differ in any other variable. Specimens of Litoria elkeae (Group 9) are also significantly smaller and have larger eyes than those from Queensland (Group 7) and Louisiade (Group 8) (Fig. 5a, c). Specimens from Queensland are significantly larger than all except those from Louisiade and have significantly smaller eyes than any of the others. They also have significantly wider heads (Fig. 5e). There are no other significant differences to be observed between any of the groups.


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Fig. 5. Pair-wise comparisons of various body dimensions and ratios in Litoria gracilenta s.l. (males only). Left side: range, mean and standard deviation diamonds for each group; right side: pair-wise comparison of means by Student’s t-test. Overlapping circles indicate non-significant differences at P ≤ 0.05. 1, New Guinea highland; 3, New Guinea lowland; 7, Queensland; 8, Louisiade; 9, Litoria elkeae. (a) Head+body length; (b) comparative tibial length; (c) comparative eye diameter; (d) comparative head length; (e) head length:width ratio; (f) snout shape ratio.

Bearing in mind the small sample sizes and the non-significant result of the Levene’s test for homogeneity of variance, we are inclined to recognise only four groups: New Guinea highland, New Guinea lowland, Queensland (L. gracilenta s.s.) and L. elkeae. The positions of L. aruensis (based on the single male syntype) and the Louisiade group are unclear. Colouration In life, Litoria gracilenta s.l. is green dorsally and white or yellow below (Menzies 1976; Cogger 2000). The lateral surfaces of the limbs that are concealed at rest may be yellow or purplish brown. The dorsal colour is restricted to a very narrow band on the upper limbs, or may be completely absent from those parts. The dorsal green colour can be a bright leaf-green or darker blue-green and the yellow colour may be pale or a brilliant golden as

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Fig. 6. (a) Oscillogram, (b) frequency spectrum and (c) sonagram of call of Litoria auae, specimen UP2498, recorded near McDowell Island at an air temperature of 24.5°C.

illustrated by Menzies (1976) (plate 3c) for a frog from Tari. A pale line along the canthus rostralis commences at the point of the snout and fades out over the tympanic membrane. The dorsum may bear scattered small white or yellow spots. Frogs preserved in alcohol are grayish-blue and the yellow colour is lost. In the series of frogs under consideration, the blue colour is either light or dark with few intermediates. However, the colours vary little within a population. In specimens from all three highland localities (Komo, Nipa, Tari, over 1400 m above sea level) the dorsum is dark blue-grey (one exception) and there are rarely any white spots. The four specimens from Haia (1100 m), a single specimen from Ok Ma (800 m) and all those from the middle Purari River (