Doctoral Candidate Department of Ecology & Evolution, Stony Brook University Stony Brooik, New York, United States
Background/Question/Methods
Resource competition is theorized to be a critical process driving community assembly and adaptive radiation. Anoles (genus Anolis) of the Greater Antilles are a key example of adaptive radiation in a higher-order taxonomic group, yet there remains little empirical evidence for competition occurring between Greater Antillean anole species. We conducted experimental manipulations between three species of Puerto Rican anole over a three-month period to identify possible markers of competition. The three study species represent two ecomorph classes – two trunk-ground anoles (Anolis gundlachi and A. cristatellus) and one trunk-crown anole (A. evermanni) – allowing us to explore competitive strength between ecomorphs. While most competition studies focus exclusively on interspecific competition, our experimental design allowed us to explore both intra- and interspecific competition. To conduct the experimental manipulations, we manually removed or added one of the three study species from each of our 12 experimental plots, surveying each plot prior to manipulation (“pre-manipulation”) and one-month after manipulation (“post-manipulation”). We sought to quantify changes in gravidity, growth rates, relative abundance (using catch per unit effort, CPUE), and movement patterns between the pre- and post-manipulation phases of the study. All results are in the context of the effect on A. gundlachi.
Results/Conclusions
As expected, intraspecific competition in A. gundlachi was highest, followed by interspecific competition between the two trunk-ground anoles (A. gundlachi and A. cristatellus), and weakest between anoles of differing ecomorphs (A. gundlachi and A. evermanni). A. gundlachi growth rates significantly decreased following the additions of A.gundlachi, A. cristatellus, and A. evermanni. The proportion of gravid A. gundlachi females significantly decreased following the additions of A. gundlachi and A. cristatellus, however exhibited no change to the addition of A. evermanni. No reciprocal significant increases in growth rates or gravidity were found when individuals of any species were removed. Relative abundance only exhibited a significant change between pre- and post-manipulation phases of the study when A. gundlachi was removed, leading to the CPUE of A. gundlachi significantly decreasing; however, this was expected given the experimental treatment. The experimental manipulations did not result in any significant changes in the movement patterns of A. gundlachi. Our study provides direct evidence that intraspecific competition is stronger than interspecific competition, and that the strength of interspecific competition may not be as strongly correlated to anole ecomorph as previously thought.
