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TROUT PREDATORS AND DEMOGRAPHIC SOURCES AND SINKS IN A MAYFLY METAPOPULATION
Author(s) -
Caudill Christopher C.
Publication year - 2005
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/03-0411
Subject(s) - metapopulation , trout , mayfly , biology , ecology , predation , abiotic component , habitat , population , occupancy , biological dispersal , fishery , demography , nymph , sociology , fish <actinopterygii>
Habitat patches often differ in environmental conditions, and the degree of environmental heterogeneity among patches is thought to influence population dynamics at the regional (metapopulation) scale. In a previous study, I found evidence of a source– sink dynamic in a metapopulation of the mayfly Callibaetis ferrugineus hageni occupying beaver ponds with or without brook trout predators, where adult females frequently dispersed among ponds, and frequently oviposited in ponds with trout. Here, I tested the hypothesis that trout create habitat sinks by manipulating trout densities and estimating local population growth rates (λ) of Callibaetis . In addition, Callibaetis emergence rates were estimated in the mayfly generation before the manipulation. Among ponds, λ ranged from 0.062 to 2.631, and nine Monte Carlo simulations scenarios revealed that four ponds had λ significantly below replacement (sinks) while the presence of source ponds was less conclusive. The manipulation of trout did not result in a detectable treatment effect, perhaps because of low statistical power resulting from high within‐treatment variation in trout densities. However, point estimates of λ and emergence rates were negatively and exponentially related to trout density, such that nearly all ponds with more than 1 trout/100 m 2 were sinks. Further, multiple regression analyses were consistent with the hypothesis that trout reduced λ and emergence rates, while other biotic and abiotic factors did not provide explanatory power. The results support the hypothesis that source–sink population dynamics may be common in freshwater habitats, and that prey metapopulation dynamics may be predicted from the distribution of predators, prey movement and habitat selection behaviors, and factors influencing the outcome of predator–prey interactions.