Evol Ecol Res 19: 353-364 (2018)     Full PDF if your library subscribes.

Front-loading life histories: the enduring influence of juvenile growth on age, size, and reproduction of primiparous female freshwater turtles

Justin D. Congdon¹, Roy D. Nagle^1,2 and Owen M. Kinney^1,3

¹University of Georgia Savannah River Ecology Laboratory, Aiken, South Carolina, USA, ²Environmental Science and Studies, Juniata College, Huntingdon, Pennsylvania, USA and ³Darlington School, Rome, Georgia, USA

Correspondence: J.D. Congdon, University of Georgia Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802, USA. email: congdon2016@outlook.com

ABSTRACT

Primary questions: (1) How do juvenile growth rates influence age and body size at maturity of females of three species of freshwater turtles? (2) Are the patterns similar among species that occupied the same wetlands over the same three decades? (3) What are the reproductive traits (i.e. clutch size and egg size) of primiparous females (first lifetime reproduction)? (4) Is there evidence that adult growth rates subsequently reduce the initial differences in the body size and reproductive traits of primiparous females?

Secondary questions: We asked several additional questions of Painted Turtles. Are growth rates of older juveniles more similar to growth rates of young juveniles or adults? What is the earliest age at which juvenile growth rate is detectably correlated with age and body size of primiparous females? Sample sizes of the other two species were too small to use for these questions.

Organisms: Three long-lived freshwater turtle species: Painted Turtles (Chrysemys picta marginata), Blanding’s Turtles (Emydoidea blandingii), and Snapping Turtles (Chelydra serpentina).

Field site: University of Michigan, E.S. George Reserve, southeastern Michigan, USA.

Methods: We conducted a 33 year mark-recapture study to document juvenile and adult growth rates and age and body size at maturity of females. We used X-radiography to determine clutch size and egg widths of primiparous and older females of all three species.

Conclusions: (1) Juvenile growth rate was the most influential trait determining within-population variation in life-history trait values of primiparous females of all three species of long-lived freshwater turtles, and that variation persisted for many years in older adults. (2) Fast-growing juveniles of all three species matured earlier and at larger (or similar) body sizes than slow-growing juveniles. (3) The relationship between juvenile growth rates and age and size at maturity in Painted Turtles was established by age 4 years. (4) Variation in indeterminate (post-maturation) growth was insufficient to reduce differences in reproductive traits within cohorts of females. (5) Similar results from all three turtle species (families Emydidae and Chelydridae) suggest that the relationships between juvenile growth rates and age and size at maturity were established in a common ancestor early in the evolutionary history of turtles.

Keywords: age and size at maturity, freshwater turtles, juvenile growth rates, reproductive traits of primiparous females.

DOWNLOAD A FREE, FULL PDF COPY
IF you are connected using the IP of a subscribing institution (library, laboratory, etc.)
or through its VPN.

 

        © 2018 Justin D. Congdon. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

       Subscribing institutions/libraries may grant individuals the privilege of making a single copy of an EER article for non-commercial educational or non-commercial research purposes. Subscribing institutions/libraries may also use articles for non-commercial educational purposes by making any number of copies for course packs or course reserve collections. Subscribing institutions/libraries may also loan single copies of articles to non-commercial libraries for educational purposes.

       All copies of abstracts and articles must preserve their copyright notice without modification.