UC Merced

Introduced species often are considered one of the major threats to biodiversity in island and marine habitats. However, generalizations from anecdotal observations, bias in scientific literature, and the unpredictability of species’ responses to new environments have limited our understanding of the impact of invasive species. To address this limitation, there is a need for an increase in quantitative studies that objectively assess occurrence, distribution and impact of non–native species in systems that are under–represented in the scientific literature. Here, we describe the introduction of a non-native sea anemone species into Jellyfish Lake, an isolated tropical marine lake. From 2003–2012, we gathered samples to identify the introduced species and quantitative data using transect and photo–quadrat surveys to describe its abundance and distribution. We also assessed its impact on native species through possible competition for space. The non–native species was found at the tourist entry into the lake in 2003 and identified as Exaiptasia sp., a symbiotic sea anemone; temporal patterns of tourism, the spatial extent of the anemone, and genetic analyses of the symbiont, were consistent with the early stages of invasion. Subsequent expansion of Exaiptasia sp. occurred within six years, fully encompassing the perimeter of the lake, occurring predominately on mangrove roots. Species’ assemblages that experienced invasion were significantly different among surveys and habitats. Using Pearson’s and Spearman rank correlation, we determined both positive and negative relationships between the percent cover of Exaiptasia sp. and a subset of 20 native species that were present in all four surveys. Overall, Exaiptasia sp. percent cover had a significant but weak negative correlation (-0.5