Abstract

Habitat loss and degradation are the leading causes of local extinctions, making preservation and restoration of remaining habitat increasingly critical to conserving biodiversity. Mechanisms driving species extinction, however, often begin with habitat loss and seldom are well understood, which greatly limits our ability to mitigate their impacts. The first step in understanding mechanisms that drive local extinction is to identify vital rates affected by habitat degradation. Here we provide a case study of the impact of habitat degradation on individual growth and reproductive rates of Eastern Collared Lizards (Crotaphytus collaris), a species of special concern in the Ozark Mountains. Our data suggest that C. collaris in habitats encroached by dense woody vegetation have reduced age-specific body size, primarily as a result of depressed individual growth rates in their first 2 yr of life. In turn, female C. collaris in habitats with high woody vegetation density have delayed age of maturity (by 1 yr in 70% of females), smaller age-specific clutch size and reduced clutch frequency (up to a 50% decrease in population annual fecundity). We conclude that depressed reproductive rates of C. collaris in degraded habitats likely contribute to population declines in Ozark glades. Our study provides the basis for understanding mechanisms driving population declines of C. collaris in the Ozarks and highlights an underutilized perspective that can be used to link causal factors to local extinction.