Effects of landscape structure in Florida scrub: A population perspective

Understanding how patchy landscapes affect the distribution and abundance o f species is a central issue in applied ecology. We examined the effects of landscape structure on the distribution of the Florida scrub lizard (Scelo porus woodi) in naturally fragmented habitat. Scrub lizards were absent fro m 89 of 132 patches, and their distribution was explained in multifactor mo dels by two landscape variables: patch size and patch isolation. Mark-recap ture studies of S. woodi and experimental displacement trials indicate that this species exhibits low vagility within a patch and that movement throug h dense habitat, which often characterizes the landscape matrix, is restric ted. Poor dispersal ability relative to the degree of isolation of patches in this landscape may account for large Saps in its distribution. To examin e the applicability of the scrub lizard model to other species, we applied the model to a sympatric lizard, the six-lined racerunner (Cnemidophorus se x-lineatus), which is similar in body size, food habits, and habitat requir ements. The racerunner was more widely distributed than the Florida scrub l izard within our scrub landscape, and the model failed to predict its distr ibution. This differing response to landscape structure by a similar specie s is likely due to the greater dispersal ability of C. sexlineatus. Our res ults, and similar studies of other scrub organisms, indicate that each spec ies may have a unique response to habitat fragmentation. The design and man agement of effective preserves for Florida scrub will require a multiscaled , multispecies approach that reflects the differences in the dispersal abil ities, area requirements, and habitat preferences of the species to be pres erved.