Indeterminate growth in longlived freshwater turt

Authors: Justin D Congdon J Whitfield Gibbons Ronald J Brooks Njal Rollinson Ria N Tsaliagos

Publish Date: 2012/07/10

Volume: 27, Issue: 2, Pages: 445-459

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Abstract

Although evidence that reptiles exhibit indeterminate growth remains equivocal and based on inadequate data the assumption that they do is still widely accepted as a general trait of reptiles We examined patterns of variation in adult growth using longterm markrecapture data on 13 populations of 9 species representing 3 families of freshwater turtles located in South Carolina Michigan and Arizona in the USA and in Ontario Canada Across 13 study populations growth rates of all adults and only those that grew averaged 15 and 19 mm/yr respectively Sources of variation in growth rates included species population sex age and latitude Most adults of both sexes with recapture intervals greater than 10 years grew but across all populations an average of 19  of individuals did not grow some with recapture intervals up to 30 years For knownage adults of three species the highest growth rates occurred during the 10 years following sexual maturity and the proportions of nongrowing individuals increased with age Growth rates of adults were on average 92  lower than those of juveniles Based on linear relationships of clutch size and body size of females at average juvenile and adult growth rates it would take 07 02–12 years and 86 min–max = 23–185 years respectively to grow enough to increase clutch size by one egg The majority of within population variation in adult body size in 3 species appeared to be a combination of differences in ages at maturity and juvenile and early adult growth rather than indeterminate growth The results from our study populations indicate that increases in body size and associated reproductive output that results from indeterminate growth are not substantial enough to represent a major factor in the evolution of life histories in general or the evolution of longevity and aging specificallyRoy Nagle and Owen Kinney Richard van Loben Sels and Todd Quinter provided many years of field assistance and continuity to the ESGR study Judy Greene Peggy Burkman and Ruth Estes provided invaluable assistance with managing the extensive data sets from SREL and the ESGR We thank Tony Tucker Judy Greene and Mike Dorcas for providing data on Malaclemys terrapin R G Farmer provided assistance with analyses of growth rates National Science Foundation grants supported some of the longterm research conducted by JWG DEB7904758 and JDC DEB74070631 DEB7906301 BSR8400861 and BSR9019771 The last half of the E S George Reserve study was primarily funded by J Congdon and N Dickson Manuscript preparation was aided by the Environmental Remediation Sciences Division of the Office of Biological and Environmental Research US Department of Energy through the Financial Assistant Award no DEFC0996SR18546 to the University of Georgia Research Foundation Previous drafts of the manuscript were improved by comments from N Dickson M Pappas and L Vitt

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