Smaller space, smaller skinks: Exploring the morphological consequences of habitat fragmentation within the Wog Wog Experiment

Background/Question/Methods:

Body size and morphology are overwhelmingly important to an individual’s performance and long-term survival. They provide limits to physiological functions, like sprinting speed, dispersal distance, ingestion rate, and reproductive potential. They also provide limits to an individual’s success in biological interactions, including competition for mates, predator avoidance, and territory defense. Studies have repeatedly shown a connection between morphology and fitness, however, morphometrics have rarely been used to study the effects of processes known to affect population persistence such as habitat loss and fragmentation. In this study, we track changes in key morphological traits for a skink species (Lampropholis guichenoti) within a 28-year forest fragmentation experiment in southeastern Australia. Using individual morphometrics to draw conclusions about a population’s fitness, this study offers new insight into the effects of habitat fragmentation on species’ persistence in remnant patches.

More than 2,500 individual skinks have been trapped within the Wog Wog Fragmentation Experiment since the project’s launch in 1985. In this study, we measured four morphological features in over 1,800 individuals: snout-vent length, head width, body width, and femur length.

Results/Conclusions:

We found that individuals varied dramatically between fragmented forest habitat and continuous forest habitat. Snout-vent length was not different between the forests types prior to fragmentation but diverged over time after fragmentation was experimentally implemented, with snout-vent length and body width declining significantly in the fragments. Skink body size then began to converge again in fragments and continuous forest over time, corresponding with the closure of the canopy in the pine matrix that surrounds the fragments.

Invertebrate surveys suggest that changes in skink body size are not related to food availability and avian surveys suggest that changes are not related to predation pressure. Rather we suspect that thermoregulation requirements are likely responsible for differences in body size across treatments, as evidenced by site-specific microclimate data that confirms both temperature and solar radiation differ across forest types. Indeed, preliminary analyses suggest that forest types vary in their heating and cooling properties, in that continuous forests experience temperature fluxuations with less amplitude than fragmented forests.

Results from this study help to expand our understanding of the effects of fragmentation on a population’s fitness through the use of individual morphometric analyses. Measuring the impacts of fragmentation on fitness proxies—such as body size—brings us closer to a mechanistic understanding of biodiversity loss in the face of habitat loss and fragmentation.