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Evolutionary demography of populations of garter snakes with alternate life-history patterns.
Bronikowski, Anne1, Arnold, Stevan2, 1 2
ABSTRACT- We model the demographic consequences of variation in life-history traits for populations of western terrestrial garter snakes. In seven long-term study populations, snakes exhibit one of two life-history phenotypes that generally can be classified on the fast/slow continuum. Snakes in lakeshore populations have fast growth, high mortality, much reproductive effort, and early maturation relative to snakes in meadow populations. We ask what are the evolutionary demographic implications of such variation by modeling the intrinsic rate of population increase, an estimate of Darwinian fitness under certain assumptions. Using traditional matrix approaches, we find that the "slow" phenotype has a higher estimate of fitness than the "fast" phenotype. In contrast, maximum likelihood estimation based on mark-recapture data with subsequent log-likelihood ratio tests among competing models indicates equivalent fitness estimates for the two phenotypes. The implications of these results are discussed.
KEY WORDS: demography, life-history, garter snakes, mark-recapture data