Habitat and life history differences between two s

Authors: Daniella M Swenton Astrid KodricBrown

Publish Date: 2012/05/22

Volume: 94, Issue: 4, Pages: 669-680

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Abstract

Life history strategies reflect tradeoffs that tend to maximize fitness such as investment in a few large or many small offspring We compared life histories of two temperate livebearing fishes Gambusia affinis and G nobilis an endangered species which is virtually unstudied The two species persist in environments that differ widely in abiotic and biotic factors in the same local area Gambusia affinis were typically found in habitats with high productivity and wide fluctuations in temperature salinity and dissolved oxygen whereas G nobilis occurred in more stable springfed habitats We collected data on lifehistory traits embryo mass brood size number of embryos total maternal reproductive effort population sex ratios and size mass and length distributions of adults and juveniles There was no difference between species in reproductive effort per brood but they differed in investment strategy Gambusia affinis females produced large broods with small embryos whereas G nobilis females produced broods of fewer larger embryos These differences in life history strategies reflect a tradeoff between individual productivity and differential mortality rates in different environments At our field site G affinis persists as an annual species with relatively high growth rates and corresponding reproductive patterns whereas G nobilis females have a slower reproductive tempo and may live multiple yearsWe thank JA Baker EL Charnov and JC Trexler for comments on the conceptual presentation of this work JH Brown MJ Ryan and BO Wolf provided editorial comments on the manuscript L Snyder T Kennedy CL Hayes A Hung S Netz A Olson and G Warrick assisted with data collection This work was funded by a grant through the New Mexico Department of Game and Fish Share with Wildlife Program to A KodricBrown and D Swenton and a National Science Foundation Doctoral Dissertation Improvement Grant an Alvin and Caroline Groves Research Scholarship UNM Biology Department Crawford Scholarship UNM Biology Department SRAC grant UNM Graduate and Professional Student Association Student Resource Allocations Committee and GRAC grant UNM Biology Department Graduate Resource Allocations Committee to D Swenton Experiments were conducted in accordance with University of New Mexico UNM Institutional Animal Care and Use Protocol number 04MCC006 Gambusia nobilis a federally endangered species were acquired maintained and tested in accordance with NM state permit 2968 and federal permit TE6768110

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