Effects of Landscape Structure in Florida Scrub: A Population Perspective

Abstract

Understanding how patchy landscapes affect the distribution and abundance of species is a central issue in applied ecology. We examined the effects of landscape structure on the distribution of the Florida scrub lizard (Sceloporus woodi) in naturally fragmented habitat. Scrub lizards were absent from 89 of 132 patches, and their distribution was explained in multifactor models by two landscape variables: patch size and patch isolation. Mark–recapture studies of S. woodi and experimental displacement trials indicate that this species exhibits low vagility within a patch and that movement through dense habitat, which often characterizes the landscape matrix, is restricted. Poor dispersal ability relative to the degree of isolation of patches in this landscape may account for large gaps in its distribution. To examine the applicability of the scrub lizard model to other species, we applied the model to a sympatric lizard, the six‐lined racerunner (Cnemidophorus sexlineatus), which is similar in body size, food habits, and habitat requirements. The racerunner was more widely distributed than the Florida scrub lizard within our scrub landscape, and the model failed to predict its distribution. This differing response to landscape structure by a similar species is likely due to the greater dispersal ability of C. sexlineatus. Our results, and similar studies of other scrub organisms, indicate that each species may have a unique response to habitat fragmentation. The design and management of effective preserves for Florida scrub will require a multiscaled, multispecies approach that reflects the differences in the dispersal abilities, area requirements, and habitat preferences of the species to be preserved.

The importance of remnant native vegetation of Amazonian submontane forest for the conservation of lizards

“…Lizard movements in distinct matrices are significantly reduced in relation to movements in forested areas (Hokit et al, 1999).…”

The effects of habitat and spatial features of wetland fragments on the abundance of two rallid species with different degrees of habitat specialization

“…Metapopulation theory predicts that both habitat size and habitat isolation are important in determining species' distribution and abundance (Hanski & Gaggiotti 2004). While patch size is likely to determine population size, which in turn affects extinction rates, the degree of patch isolation can affect colonization rates, and empirical evidence consistent with these assumptions has been reported from several systems (Hokit et al 1999, Hames et al 2001, Hanski & Gaggiotti 2004, Bennett & Saunders 2010. Patch quality may be a further determinant of species' occupancy and turnover rates (Summerville & Crist 2001, Thomas et al 2001, Fleishman et al 2002, Bennett & Saunders 2010.…”

“…Patch quality may be a further determinant of species' occupancy and turnover rates (Summerville & Crist 2001, Thomas et al 2001, Fleishman et al 2002, Bennett & Saunders 2010. The response to habitat quantity, quality, fragmentation and isolation differs between species, with the relative importance of these factors depending on species traits (Hokit et al 1999, Marshall et al 2000, Johansson & Ehrlén 2003. Most specialized and low-dispersal species show distinctive ecological requirements and are often sensible to variation in the aforementioned factors, while species with broader niches and high mobility are often less affected by environmental traits and occur over a broader range of combinations of isolation, habitat types and features.…”

Modeling Approaches in Avian Conservation and the Role of Field Biologists

“…Some of these parameters require information that is nearly impossible to obtain in the field (e.g. rate of mortality during migration), but techniques that require a few simplifying assumptions are available to estimate them from readily obtainable field data (Hanski 1994b(Hanski , 1999 (Hanski 1999, Hokit et al 1999. Also, by changing the number or configuration of patches, the relative importance of each patch to metapopulation persistence can be evaluated (Hanski 1994a(Hanski , 1999.…”

“…Because they are based on presence-absence data and are designed to predict patch occupancies, occupancy models generally are not used to predict population densities or actual population size. Patch models have an advantage here; in addition to turnover rates and equilibrium occupancy, they also provide population trajectories, risk of population extinction or decline, and related measures of population size (Akcakaya and Atwood 1997, Hokit et al 1999).…”