Inbreeding levels and prey abundance interact to determine fecundity in natural populations of two species of wolf spider |
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Authors: | David H Reed Amy C Nicholas Gail E Stratton |
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Institution: | (1) Department of Biology, University of Mississippi, P.O. Box 1848, University, MS 38677-1848, USA |
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Abstract: | Long-term effective population size is expected, and has been shown, to correlate positively with various measures of population
fitness. Here we examine the interacting effects of population size (as a surrogate for genetic factors) and prey consumption
rates (as a surrogate for environmental quality) on fecundity in two sympatric species of wolf spider, Rabidosa punctulata and Rabidosa rabida. Population size was estimated in each of seven genetically isolated populations in each of 3 years using mark-recapture
methods. Fecundity was estimated as the mean number of live offspring produced by ∼15 females sampled from each population
of each species each year for 3 years. Prey consumption rates were estimated by sampling ∼300 spiders per population per year
and assaying the proportion of spiders with prey. Larger populations have higher fecundity and more genetic diversity than
smaller populations. Variation among populations in fecundity for a given year could be attributed most strongly to differences
in population size, with variation in prey consumption rates and the interaction between population size and prey consumption
playing smaller but still important roles. During the most stressful environmental conditions, the smallest populations of
both species experienced disproportionately low-fecundity rates, more than doubling the estimated number of lethal equivalents
during those years. The evidence presented in this paper for inbreeding-environment interactions at the population level and
further evidence for a log-linear relationship between population size and fitness have important implications for conservation. |
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Keywords: | Extinction Fitness Genetic diversity Genetic stochasticity Population size Prey consumption Wolf spiders |
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