Nancy L. Stanton

Cushion plants as islands

SummaryThe acarine fauna of two abundant species of cushion plant on the high, short-grass prairie of S.E. Wyoming were used to test The MacArthur-Wilson Theory of Island Biogeography. Multiple regression analysis using area, distance and percent moisture as independent variables and number of mite species and number of mite individuals were run for the two sampling dates. Results showed area alone to be consistently and highly correlated (r=0.84–0.94) with both species and individuals for one cushion species. The slopes of the species-area and individuals-area curves are among the highest recorded and were significantly higher on the second sampling date. Selective seasonal changes in the fauna were shown by increases both in numbers of species and individuals, mainly on larger cushions, for the later sampling period. It is hypothesized that seasonal changes are due to an increase in the number of predator species in response to an increase in the number of prey items. The slopes of the species-area curves are compared with those in the literature and it is argued that slope values are more dependent upon the taxonomic group being studied than on whether the island is insular or oceanic. Finally, we suggest that The MacArthur-Wilson Theory is not applicable to islands which 1) exhibit continuous growth, 2) lack a discrete species source, and 3) are relatively transitory.

Coccidian assemblages in the Wyoming ground squirrel, Spermophilus elegans elegans

One thousand nineteen Wyoming ground squirrels (Spermophilus elegans elegans) from 4 populations in southern Wyoming were examined for intestinal parasites. The most prevalent parasites were 6 species of coccidia: Eimeria beecheyi, Eimeria bilamellata, Eimeria callospermophili, Eimeria larimerensis, Eimeria morainensis, and Eimeria spermophili. Most ground squirrels harbored 2 or more species. This eimerian assemblage was present across populations and over years. Differences in the prevalence of infection were not found among host age classes or between sexes. The presence or absence of helminths was independent of the presence and absence of Eimeria. A log-linear model to test the independence of the distribution of Eimeria spp. among hosts revealed 3 significant positive associations, for E. bilamellata and E. beecheyi, E. morainesis and E. callospermophili, and E. larimerensis and E. bilamellata.

Spontaneous, field tested and tethered flight in healthy and infected Magicicada septendecim L.

SummaryFlight capabilities of healthy and fungus infected Magicicada septendecim L. (Homoptera: Cicadidae) were compared using 3 complementary techniques: 1) observations of spontaneous flights, 2) field-tested flights, and 3) tethered flights in which endurance was measured. Spontaneous flight distances are much lower than those obtained on field tested fliers. While healthy individuals flew significantly greater distances than did individuals bearing conidia or resting spores of the fungus, Massospora cicadina Peck, the two groups-healthy versus conidia and resting spores pooled-did not differ in flight speed or flight endurance. The magnitude of each of the 3 flight indicators is much lower than those of most dispersing insects, suggesting that this periodical cicada species is a relatively poor disperser.Nevertheless, and contrary to the results of one published study, cicadas flew long distances in single flights, also they often took many flights. Our data help to explain how periodical cicadas can invade new, sometimes distant, habitat each generation. Since infected individuals have both the speed and the endurance of healthy individuals, we conclude that the conspicuous absence of the fungus from early successional, manmade, and second growth habitat is due either to the inability of resting spores of this fungus to survive in recently plowed or fertilized soils or to an intrinsic aversion to flight of infected individuals.

Eimerian guilds (Apicomplexa: Eimeriidae) in Richardson's (Spermophilus richardsonii) and wyoming (Spermophilus elegans) ground squirrels

Feces of Richardsons ground squirrels (Spermophilus richardsonii) were examined to determine occurrence and prevalence of eimerian species and to compare guilds in these hosts to previously described guilds from Wyoming ground squirrels (Spermophilus elegans). Six species of Eimeria were collected from 100 Richardsons ground squirrels: Eimeria beecheyi (36% infected); Eimeria bilamellata (13%); Eimeria callospermophili-Eimeria morainensis complex (41%); Eimeria lateralis (6%); and Eimeria spermophili (9%). The species composition and prevalences were essentially identical in the 2 congeneric hosts. Three species were consistently more (> 30%) and 3 were consistently less (< 20%) prevalent in both host species. Furthermore, in both squirrel species the rare species were more prevalent in juveniles. Eimerian guilds such as these may be common to many species of ground-dwelling sciurid squirrels. The report of E. beecheyi in Richardsons ground squirrel constitutes a new host record for this species.

Synonymy of Eimeria larimerensis with Eimeria lateralis

Oocysts of Eimeria lateralis were isolated from feces of Spermophilus richardsonii and compared to published descriptions of E. lateralis and Eimeria larimerensis from other spermophiline rodent hosts. A comparison from other spermophiline rodent hosts. A comparison of these 2 eimerian species, combined with an examination of host specificity of spermophiline eimerians and host and parasite distributions, suggests that E. larimerensis is synonymous with E. lateralis.