Jim Carrel (see photo, this page) studies the chemical ecology of toxic insects at Archbold, particularly antipredator defenses of beetles and caterpillars. Some of these projects are collaborative efforts with Thomas Eisner (see page 19) and Mark Deyrup (see pages 17-18). Recently Carrel demonstrated that aposematic caterpillars, Uresiphita reversalis, use substances in their integument to ward off several species of spiders, but this defense does not deter assassin bugs, Zelus sp., which quickly poke their sharp beaks into the soft larvae (J. Kansas Entomol. Soc., in press). Also, he and his students are continuing long-term monitoring of populations of four rare, scrub-endemic spiders to document the pattern of interannual variation in spider densities. For example, he showed that the red widow spider, Latrodectus bishopi, exhibited an 80-fold variation in density during 1989-98 (Fla. Entomol., 84(3):385-390, 2001). [Link to Fla. Entomol. on-line for a PDF file of this article.] This work will form the basis for future manipulative studies aimed at understanding the causes of population variation in scrub-adapted spiders. In collaboration with his wife, Jan C. Weaver, Carrel has initiated an inventory of the arthropods that live as a community in, and derive their livelihood from, leaf litter produced by scrub plants.

Margaret Hodge. Intraguild predation (IGP) refers to predatory interactions between different species which use similar resources. Hodge studied the potential for IGP interactions between two species of wolf spiders sympatric in scrub habitats at Archbold: Hogna osceola (the larger species) and H. ceratiola. These two species represent over 80% of the nocturnal wolf spider fauna. I measured diet and habitat use and report here on the latter. Discriminant analysis of habitat use found that H. osceola tends to forage in vegetation, whereas H. ceratiola tends to forage on open sand. The two species overlap, however, in their use of leaf litter. As leaf litter has more insect prey than open sand, field-enclosure experiments were designed to examine how interspecific interaction affects ground substrate preference by the two species. When alone in enclosures, H. osceola preferred leaf litter and H. ceratiola showed no distinct preference for either substrate. When both species shared the enclosure, H. osceola retained their preference for leaf litter while L. ceratiola exhibited a distinct preference for sand. In addition, H. ceratiola gained significantly less weight when with H. osceola than they did when in enclosures by themselves, indicating a potential interference effect of H. osceola. These results suggest that habitat use by H. ceratiola may be mediated by IGP interactions with H. osceola. [Link to abstract of poster in 2001 Archbold Symposium.]

Sam Marshall. Florida has nine burrowing wolf spiders in the genus Geolycosa, seven of which live in scrubs and sandhills across the state (see map, this page). Marshall’s current research focus has been to: (1) estimate the evolutionary relationships among Floridian Geolycosa populations and species using comparisons of cytochrome c oxidase subunit I mitochondrial DNA sequences, and (2) use the hypothesized relationships to infer the historical patterns of the evolutionary diversification of Geolycosa in Florida. Preliminary phylogenetic analyses of the gene sequence data suggest that (1) Floridian Geolycosa are not a monophyletic assemblage, (2) G. xera, G. escambiensis, G. hubbelli, G. patellonigra, and G. micanopy are not valid species in a phylogenetic sense, and (3) the two distinct ecological morphs of Geolycosa (i.e., those pale species that build burrows in barren areas vs. those dark species that colonize areas covered in leaf litter) have evolved repeatedly in Florida. The data suggest that the Geolycosa of eastern USA are derived from ancestors in the western Panhandle, and that the pattern of divergence within Florida occurred from west to east, rather than from north to south as previously proposed. [Link to abstract of paper in 2001 Archbold Symposium.]