Natural history, behavior, and bacterial microbiomes of a socially polymorphic spider, Anelosimus studiosus

Anelosimus studiosus is a unique spider; throughout its range from Argentina to New England, most adult females are solitary and subsocial (provide maternal care). However, in the northernmost parts of its range in the United States, adult females sometimes live in cooperative aggregations. While this social polymorphism has been well defined in specific regions of A. studiosus’ range, it is not so thoroughly described elsewhere. Therefore, I first describe the aggregative behavior, natural history, and population sex ratios for A. studiosus across a latitudinal gradient in Texas (Chapters 1 and 2). I discovered that A. studiosus tend to aggregate at higher latitudes in Texas, but that this tendency was not correlated with female-biased primary sex ratios, suggesting that outbreeding still occurs in these populations. I then compared the social behavior of A. studiosus from Texas populations to those further east (Alabama and Tennessee) using tests of aggressive tendency (Chapter 3). Individuals from western and eastern populations vary in aggressive tendency, but I was unable to corroborate previous findings that different measures of aggressive tendency correlate. Finally, I used 16S rRNA metagenomics to describe the bacterial microbiome of A. studiosus (Chapter 4). Similar to some spider species but unlike many other animals, A. studiosus do not harbor a consistent, core bacterial community, and instead, their bacterial communities reflect their rearing environment and diet. In all, this dissertation on the socially polymorphic Anelosimus studiosus adds to a growing body of literature on the complexity of animal personalities, and their effect on organismal biology.