effects of host and spatial factors on a haemoproteid ... - BioOne

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alyzed certain aspects of the component level structure and pattern in a micropar- asite community using quantified density data. Our objectives were to examine.
Journal

EFFECTS

OF HOST

AND

SPATIAL

COMMUNITY

IN MOURNING

Ralph

Jr.,

2

0. Godfrey,

Department

of Range

Department

of Pathology,

Author

to whom

Danny

and

reprint

DOVES

B. Pence,23

Wildlife

Management,

Texas Tech University requests

FACTORS

should

FROM

and

Alan

Texas

Tech

Health

Sciences

of Wildlife

Diseases, © Wildlife

26(4), 1990, pp. 435-441 Disease Association 1990

ON A HAEMOPROTEID WESTERN

TEXAS

M. Fedynich University,

Lubbock,

Center,

Texas

Lubbock,

Texas

79409, USA 79430, USA

be addressed

ABSTRACT: Two species of hematozoa, Haemoproteus columbae and H. sacharovi, were observed on thin blood smears from populations of mourning doves (Zenaida macroura) in the Rolling Plains (RP, a semiarid dryland farming and grazing area) and Southern High Plains (SHP, an intensively cultivated and irrigated agricultural region with playa lakes) of western Texas (USA). Prevalences of H. columbae and H. sacharovi were 91 and 18% in doves from the RP (n = 44 doves examined) and 81 and 36% in those from the SHP (n = 84), respectively. Although the prevalences of these species were not significantly different between the RP and SHP, the prevalence of H. sacharovi was significantly greater in juvenile versus adult doves from both localities. Mixed infections of both haemoproteid species occurred in 11 and 24% of the doves from the RP and SHP, respectively. The frequency distributions of the relative density values (numbers of parasites/2,000 erythrocytes counted) of H. columbae and H. sacharovi were overdispersed in hosts from both localities. Relative densities of H. columbae were significantly higher in mourning doves from the RP versus the SHP; likewise those of H. sacharovi were significantly greater in juvenile versus adult doves and between localities. Observed differences in prevalence and relative density of the two species in the haemoproteid community across spatial and host variables may reflect differences in vector transmission and in the physiological and immunological status of the

host.

This

study

emphasizes

the

importance

of

using

adequately

quantified

density

data

versus

only prevalence data when examining microparasite communities at the component community level. Key words: Hematozoa, Haemoproteus columbae, Haemoproteus sacharovi, mourning dove, Zenaida macroura, component level community ecology, host sex effects, host age effects, locality effects,

prevalence,

relative

density,

field

study.

microparasites, INTRODUCTION

Most the

contemporary

component

roparasite sembleges hosts

(helminths occupying are

based

Alternatively,

utilizing

studies level

on

at mac-

and arthropods) niches in vertebrate

on

relative

because

ciated with communities the parasitic prevalence dicated host,

ecology

community

density

of difficulties

as-

data.

on the ponent

asso-

macroparasitic

quantification, most studies on of microparasites, including protozoa, have been based on data. However, even studies

only trends temporal

data

on

prevalence

of changing and spatial

have

such

as the

avian

hemato-

zoa, have been based on only frequency data or, at best, frequency data and subjectively ranked density data. Therefore, these analyses lack the robustness of studies community community

ecology at the level of free-living species

where

comor

relative

dis-

tributions a habitat

in numbers of individuals can be considered. Utilizing

across the

methods

of Godfrey

et al.

(1987),

we

an-

alyzed certain aspects of the component level structure and pattern in a microparasite community using quantified density data. Our objectives were to examine the

in-

patterns across variables in

communities of such groups as avian haemosporidians (see Greiner, 1970, 1975). Although there have been attempts to quantify microparasites within host individuals and to examine these data across host and temporal variables, the methods

main and interactive effects of selected host and spatial variables on the hematozoan community in an avian host. We examined the effects of (1) host age, (2) host sex and (3) locality on the prevalence and density

were

moproteus

in the

mourning

macroura)

from

western

Thus,

often

subjective

previous

studies

(Godfrey on

et a!., the

ecology

of

1987). of 435

a community

of

two

species dove Texas

of

Hae-

(Zenaida (USA).

436

JOURNAL

OF WLDLIFE

MATERIALS Study

DISEASES,

AND

VOL.

26, NO. 4, October

METHODS

area

Doves were collected from localities in Castro County (34#{176}25’N, 102#{176}02’W) and Foard County (33#{176}71’N, 99#{176}38’W) in western Texas. These counties are in the Southern High Plains (SHP) and Rolling Plains (RP) vegetation zones, respectively. The SHP was originally a short grass prairie which is now used largely for intensive agricultural cultivation of row crops such as corn, grain sorghum and cotton; there are numerous (>0.5 km2) shallow intermittently flooded basins called playas that provide most of the habitat for wildlife in the region (Guthery, 1981; Simpson et al., 1981). Bruns (1974) and Bolen and Guthery (1982) further discuss the characteristics of Castro County. Major land use features of the RP include dryland grain production and rangeland for cattle. Vegetation in the RP consists of mixed grass species interspersed by juniper (Juniperus sp.) breaks and mesquite (Prosopis glandulosa) flats. The area is described in detail by Koos and Dixon (1964). The greater availability of wildlife habitat in the RP suggests a more homogeneous distribution of doves than occurs in the SHP where they are concentrated near the playas. Additionally, surveys by the Texas Department of Parks and Wildlife (Austin, Texas 78744, USA) indicate that breeding populations of mourning doves were higher in the RP than the SHP (George, 1988).

Data

collection

Mourning doves (n = 128) were collected by shooting from 1 to 8 September 1985. We regarded these birds as residents because (1) band recovery analyses of mourning doves harvested in

the

northern

hunting

zone

of

Texas

showed

that the majority of all birds shot originated from the same zone (Dunks, 1977) and (2) all doves were collected prior to any major cold frontal activity, thus assuring that mainly resident and not northern migrants were collected. Birds were aged by plumage and gonad characteristics (Cannell, 1984; Bivings and Silvy, 1980) and sexed by gonad examination. Two thin blood smears from each dove were made from heart blood immediately (