The Ghost of Competition

Yesterday I visited Elise, better known as “the anole lady”, to "help" with lizard catching. According to "the anole lady", it was a relatively successful day. We spotted a couple of previously marked males, and a handful of new individuals from both sexes. For someone used to working in the West Indies, I would have categorized such a performance as way bellow par; but it looks like working with A. carolinensis in natural forest around NC is a different story.
    Which brings me to next point. Anolis carolinensis is widely distributed, from Florida to Tennessee, however much of what we know about this species with regards to its ecology comes from studies from the southern range of its distribution (e.g., Florida, Georgia, Louisiana). Although, Sandy Echternacht, at UT Knoxville, has been studying A. carolinensis in Tennessee where he has found that their behavior is different from what is commonly observed in FL. 

    In Florida a significant amount of research has been done to evaluate the impact of A. sagrei (a somewhat recent invader) on A. carolinensis. One of the main findings is that A. sagrei seems to be displacing A. carolinensis from the lower portion of tree trunks. To my surprise nearly all of the activity we observed yesterday took place relatively high, above 3 meters.  Moreover, although we saw a nice amount of movement, in one instance a male travelled approximately 5 meters, none of the individuals ventured lower than 1.75 meters. Instead, individuals moved from tree to tree by the using connecting braches or by jumping between them. How common is this behavior (i.e. selection of relatively high perches in the absence of congeners) is an open question waiting to be answered. Its response might shed some light into our current understanding of the outcome of the interactions between A. carolinensis and A. sagrei.  For example, if we were working in Florida, I would have told Elise "you see, A. sagrei is displacing A. carolinensis"; however no A. sagrei here, which brings me back to the title of the blog. Working with competition is not for the faint of heart. It takes some clever thinking to design an elegant experiment, and even then you are always left wondering if the species' evolutionary history might partially account for the observed pattern.