INVASION CONTINUUM: UTILIZING ECOLOGICAL TRAIT DATA TO CHARACTERIZE LATE PLEISTOCENE INVASIVE SPECIES IN SOUTHERN CALIFORNIA

Marine ecosystems in southern California are influenced by severe threats due to climate change caused by human activities. The Quaternary of Southern California provides valuable paleo records from glacial-interglacial cycles that offer insight into past climatic impacts on coastal ecosystems. Marine invertebrates, in particular mollusks, have been used to identify biogeographic patterns, with sea surface temperature as a major factor in predicting those patterns. The fossil faunas have thermally anomalous assemblages found outside their modern-day distribution range, referred to as extralimital species or local invasives. Such records have been used to infer paleoclimatic conditions. These invasives can be valuable to define paleoenvironmental conditions in relation to community dynamics and habitat suitability. Ancient invasions are facilitated by the collapse of climatic, geographic, or ecological barriers and can be categorized based on their level of intensity, ranging from short-lived to established populations.

Our research goal is to recognize different functional traits of these invasives utilizing both fossil and modern occurrence data derived from museum collections. Ecological traits, including abundance, reproductive output, behavior and fitness proxies can assist in determining where these non-native species fall on the spectrum of introduction, naturalization, and invasion hierarchy. Within Los Angeles Basin, which has one of the richest Late Pleistocene fossil records (762 spp.) in Western North America, as much as 25% of the molluscan fauna could be considered extralimital. However, many (43%) of these species' records occur less than 1° of latitude beyond their current latitudinal range. The species found far beyond their latitudinal range endpoints (>2°) are usually infrequent. Our ongoing investigation will seek whether there are any other overarching ecological trends. An initial finding shows that many extralimitals get smaller in body size as they reach the edge of their biogeographic range, suggesting sensitivity in fitness levels at the boundaries. Exploring the synergy between paleontological and neontological data, our study enhances the understanding of climate change's effects on invasion hierarchy, informative for future conservation planning.