DISSERTATION RESEARCH: How Ecological, Behavioral, and Morphological Traits have Shaped Diversification Patterns in Assassin Spiders

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Assassin spiders have an enigmatic distribution where numerous extinct fossil lineages are known only from the northern hemisphere and with all living species being restricted to the southern hemisphere. This distribution could have arisen if the spiders were once widespread and now only exist as survivors in small habitat patches on isolated continents. Alternatively, it could be that this distribution is a result of continental breakup or ancient dispersal. This study seeks to determine the evolutionary relationship between living and extinct species, which will enhance understanding of biogeographic and evolutionary history. Morphological characters of fossil species will be examined using X-ray scanning techniques with the purpose of placing fossil species into a phylogeny, a branching diagram of evolutionary relationships. The current study makes use of a unique opportunity to study a lineage of spiders with extinct and living species, which includes species radiations that appear to have arisen at very different periods of time and across multiple continents. The study will allow assessment of morphological characteristics of fossil lineages and will examine whether these characteristics can be used to understand past behaviors in extinct taxa. These discoveries may then be compared to patterns in other extinct and living organisms to test whether the patterns are general for earth history. Results of this work will be used in displays at the California Academy of Sciences.