INTERSECTIONS BETWEEN ICHNOLOGY AND INVASION ECOLOGY ON THE GEORGIA BARRIER ISLANDS, WITH APPLICATIONS TO CONSERVATION BIOLOGY

The Georgia barrier islands are geologically unique among barrier-island systems worldwide by having six composite islands formed by temporally separate but spatially overlapping sea levels during the Pleistocene and Holocene. Like most barrier islands worldwide, though, their ecological traits have been altered considerably by invasive species, most of which were introduced in only the past few hundred years. Hence these islands serve as living laboratories for studying the effects of invasive species on modern environments, which can be contrasted with Pleistocene and late Holocene environments and their biota there before European colonization. The most easily visible effects on Georgia barrier-island ecosystems are by large feral mammals, such as hogs (Sus crofus), cattle (Bos taurus), and horses (Equus caballus). The Pleistocene and Holocene fossil record of the barrier islands and nearby Georgia coastal plain reveals no evidence of mammals ecologically analogous to these species, other than possibly Bison bison. Nonetheless, each of these exotic species have Pleistocene and Holocene fossil records elsewhere, hence these evolutionary histories can be applied to better understand the behavioral ecology of what are no longer domesticated species. Furthermore, neoichnologically based studies can greatly increase our understanding of these species in a wild state without unduly influencing their behaviors. Preliminary summaries of traces made by S. crofus, B. taurus, and E. caballus on the Georgia barrier islands will be reviewed in this study, including what is perhaps their most surprising aspect, that these three species interact with substrates and biota of coastal dunes, salt marshes, and intertidal beaches. These findings call into question their designation as “terrestrial only ” species, and should be taken into account in their assessment and management. In short, a combination of paleontology and neoichnology can expand useful knowledge for conservation biologists when assessing the ecological impacts of invasive species on barrier islands.