Species coexistence and conservation: the influence of habitat on the coexistence of a native and an invasive crayfish.
Murray, Jody*,1, Lodge, David1, 1 University of Notre Dame, Notre Dame, IN
ABSTRACT- Understanding the circumstances that allow species coexistence is one of the fundamental topics of community ecology. This topic is also increasingly relevant to managing the impact of nonindigenous species. In some lakes of northern Michigan and Wisconsin the invasive rusty crayfish (Orconectes rusticus) and the native virile crayfish (O. virilis) coexist, while in other lakes the invader has extirpated the native. Using long-term data on many lakes, we examined the duration of persistence of the native crayfish after invasion by rusty crayfish. In eight of 13 lakes for which we have good time series, rusty and native crayfish currently coexist and have done so for an average of 24 years. In the remaining five lakes, rusty crayfish have been in the lakes for an average of 22 years and extirpated native crayfish in an average of 11 years. To test the hypothesis that habitat availability is an important determinant of coexistence, we compared habitat availability in 24 lakes that differed in the fate of the native crayfish. Lakes where rusty crayfish have extirpated native crayfish have a littoral zone comprised of a significantly higher percentage of cobble habitat (51% vs. 30%, p=0.008) and a significantly lower percentage of vegetated habitat (11% vs. 41%, p=0.005) than lakes where the two species coexist. Vegetated habitats thus appear to provide a refuge for native crayfish. This is consistent with observations from our sampling, in which native crayfish are most often found in vegetated habitats in lakes where they coexist with rusty crayfish.
Key words: invasion biology, freshwater, crayfish
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