The ontogeny of postmaturation resource allocation in turtles

Area of Science:

• Comparative physiology
• Vertebrate life-history evolution
• Reproductive ecology

Background:

• Life-history strategies dictate resource allocation, with long-lived endotherms favoring growth early and reproduction later.
• Resource allocation patterns in long-lived ectotherms remain understudied, limiting understanding of vertebrate life-history generality.
• Investigating resource allocation in ectotherms like turtles is crucial for a comprehensive view of vertebrate strategies.

Purpose of the Study:

• To examine age-related resource allocation in reproductively mature female painted turtles (Chrysemys picta).
• To determine if resource allocation patterns differ between younger and older females over a four-year period.
• To assess the influence of nesting experience on resource allocation in this long-lived ectotherm.

Main Methods:

• Compared body size, egg mass, and reproductive frequency between two distinct age classes of female painted turtles.
• Analyzed steroid hormone concentrations (testosterone, progesterone, estradiol) in egg yolks.
• Tracked resource allocation patterns over a four-year observation period.

Main Results:

• Younger female turtles were smaller and allocated fewer resources to reproduction compared to older females.
• Eggs from younger females exhibited higher testosterone levels.
• Eggs from second (seasonal) clutches showed increased progesterone and estradiol concentrations.
• Older, larger females produced larger eggs and more frequent second clutches.

Conclusions:

• Resource allocation patterns demonstrably vary with age in long-lived ectothermic vertebrates.
• Age is a significant factor influencing reproductive investment and strategy in painted turtles.
• Findings contribute to understanding the diversity of life-history strategies across vertebrate taxa.