Habitat disturbances differentially affect individual growth rates in a long-lived turtle

摘要

Disturbances often help structure ecological communities, and their impacts may have consequences on population dynamics and long-term species persistence. Should disturbances affect resources, a trade-off may result between reproduction and individual growth, which in turn could affect the timing of sexual maturity in animals dependent on reaching a requisite size for the onset of maturation. We used a 14-year mark-recapture dataset to determine the effects of catastrophic storms and the removal of nonindigenous vegetation on individual growth rates of a long-lived turtle Terrapene carolina bauri. Adult male growth rates increased 19% after the disturbances, whereas female growth rates decreased by a similar percentage. Juvenile growth rates briefly increased, but as these animals became subadults, their growth rates slowed after disturbance, a change more pronounced in females than males. After the disturbances, the onset of male sexual maturity decreased by c. 1 years (from 10.8 to 9.5 years), female maturity was delayed by 2.5 years (from 8.5 to 11.0 years), and the subadult life stage was extended from 2 to 3.5 years. With resources and habitats similarly available to adults, we hypothesize that adult females diverted resources from growth to reproduction, whereas males allocated available resources to growth. Subadult growth rates decreased regardless of sex, implying that fewer or lower quality prey were available to smaller sized turtles in the years following disturbance. The results of this study suggest that habitat disturbances affected individual growth rates differently according to sex and life stage, which in turn affected the timing of maturation. In long-lived vertebrates, such perturbations on life-history traits such as growth rates likely affect population recovery, and may help to explain why turtle populations recover slowly following catastrophic disturbance, even when adult survivability is high.