Fragmentation driven effects of temperature on lizard distribution and abundance: Long term, experimental evidence

Background/Question/Methods

Habitat loss and fragmentation is considered the greatest single contributor to biodiversity loss worldwide and increasing rates of fragmentation underscore the importance of understanding the full spectrum of its ecological consequences. One of the most immediate and universal effects of fragmentation is the increased incidence of solar radiation at newly created edges, resulting in higher and more variable surface temperatures within remaining forest patches. These changes in thermal conditions can have important implications for thermoregulation and energetics, particularly in ectothermic organisms.

In this study, we model air temperature within remnant forest patches in the long-term, controlled, and replicated Wog Wog habitat fragmentation experiment in southeastern Australia. Air temperature is modeled for each of the 188 pitfall trapping sites, in each year, using forest type, topography, wind speed and intensity, and the height of the pine plantation surrounding the native Eucalyptus forest patches. We use biophysical equations to translate that modeled air temperature into a set of biologically relevant measures of thermal conditions: operative body temperature (the temperature experienced by the organism), energy expenditure, and activity time. In this study, we focus on a small, ground-dwelling skink species (Lampropholis guichenoti)—the most abundant reptile species at the Wog Wog site.

Results/Conclusions

Sampling at Wog Wog began in February 1985 when six replicates were delineated. Four of the six replicates became habitat fragments when the surrounding Eucalyptus forest was cleared in 1987. Two replicates remain in adjacent continuous forest and serve as non-fragmented control plots. More than 5,000 L. guichenotiindividuals have been trapped within Wog Wog since 1985, presenting an opportunity to test the relationship between thermal conditions and skink distribution and abundance before fragmentation, immediately following fragmentation, and over time.

Results suggest operative body temperature, energy expenditure, and activity time can serve as useful predictors for skink distribution and abundance. Differences in thermal conditions correlate with differences in distribution and abundance between fragmented and continuous forest treatments and within remnant patches. We also found that topography, wind speed and intensity, and the height of the pine plantation surrounding the patches were important variables for modeling air temperature.

This study provides insight into the influence of fragmentation-driven temperature changes on ectotherm persistence in fragmented landscapes. These results help expand our understanding of the effects of fragmentation by expanding our understanding of changes in the thermal environment that follow fragmentation and the impact of those changes on organisms in remaining habitat patches.