Factors Affecting the Distribution and Abundance of Microtus Ochrogaster and M. Pennsylvanicus in East-Central Illinois (Competition, Agonistic)
Klatt, Brian Jerome
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https://hdl.handle.net/2142/77625
Description
Title
Factors Affecting the Distribution and Abundance of Microtus Ochrogaster and M. Pennsylvanicus in East-Central Illinois (Competition, Agonistic)
Author(s)
Klatt, Brian Jerome
Issue Date
1986
Department of Study
Ecology, Evolution, and Conservation Biology
Discipline
Ecology, Evolution, and Conservation Biology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Ecology
Language
eng
Abstract
An apparent case of habitat segregation between the meadow vole (Microtus pennsylvanicus) and the prairie vole (M. ochrogaster) was investigated in east-central Illinois. Local distribution of the two species indicated a strong negative association. Multivariate analysis of variance of the vegetation characteristics of M. ochrogaster and M. pennsylvanicus sites were characterized by a greater total vegetation biomass, a higher percent composition of grasses other than Poa and by a lesser amount of Taraxacum than were M. ochrogaster sites. Discriminant function analysis indicated that the structure of the vegetation is a better predictor of whether a site is occupied by M. ochrogaster or M. pennsylvanicus, than are floristics. It is suggested that differential predation risk resulting from differences in nest location is responsible for the preference of M. pennsylvanicus for dense vegetation and tolerance of M. ochrogaster for sites with more sparse cover. A series of three manipulative field experiments using the addition or removal of individuals, to or from, open and enclosed vole populations were conducted between 1977 and 1984 to determine if the apparent habitat segregation was due to an interspecific competitive interaction. The experiments strongly suggested that: (1) a competitive interaction exists between M. pennsylvanicus and M. ochrogaster in central Illinois; (2) the two species do not compete directly for food; (3) the competitive interaction is a key determinant of the local distribution of the two species; and (4) some advantage in the competitive interaction accrues to the species which is first resident at a particular site. Interspecific dyadic encounters, conducted in each species' typical habitat, showed a strong habitat effect on the agonistic behavior of the two species. M. pennsylvanicus females tended to dominate both sexes of M. ochrogaster in dense vegetation, whereas male M. ochrogaster tended to dominate both sexes of M. pennsylvanicus in sparse vegetation. It is concluded that the between-habitat shift in agonistic behavior plays a key role in the competitive interaction, thus determining the distribution of these two species in east-central Illinois.
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