Wednesday, August 4, 2010 - 9:20 AM

COS 53-5: Effects of an insular lizard translocation on the local invertebrate assemblage

Michael L. Treglia and Lee A. Fitzgerald. Texas A&M University


Long term success of translocations is influenced by multiple factors including propagule size environmental conditions, and resource availability. However, for lizards, the relationship between the focal organisms and local prey resources is not well understood. Few studies have investigated their impacts on the invertebrate prey base, and most that have were focused on sit-and-wait predators and specific prey taxa. In an attempt to better understand the dynamics between lizards and their prey, we examined the potential for food depletion in a translocated population of the active-foraging lizard, Ameiva polops using a controlled enclosure experiment. From May through June, 2008, we contained 57 translocated adult A. polops in a series of eight 10 x 10 m enclosures at Buck Island Reef National Monument, U.S. Virgin Islands. In the first and sixth weeks of containing the lizards, we sampled invertebrates from the enclosures with A. polops, and from control enclosures, without A. polops, using pitfall traps. To determine whether A. polops was impacting the invertebrate assemblage, we compared relative changes in abundance of individual taxa between control and lizard enclosures, and looked at shifts in the overall community using nonmetric multidimensional scaling.  


Overall, the invertebrate community in enclosures decreased in abundance from the first week to the sixth, but exhibited more rare taxa. Generally, changes in abundance of individual taxa were not explained by the presence of A. polops in enclosures, with a main exception being Thysanoptera, which was rare in the first week in all enclosures, but became common in control enclosures in the sixth week. It is not clear why this group became abundant in control enclosures, as they are not typically prey of lizards. With no other major changes caused by A. polops, it is unlikely for there to be another trophic interaction contributing to this difference. Our ordinations show that in the first week, control and lizard enclosures generally overlapped with respect to the invertebrate communities, but in the sixth week, they separated slightly, indicating that to some extent, the changes in them were different. Thus, A. polops may have small impacts on the composition of invertebrate communities at a site, though they do not seem likely to completely deplete those resources.