UBC Theses and Dissertations
Economies of scale, social immunity, and host-parasite interactions in a social spider system Straus, Samantha
This thesis work addresses Anderson and May’s four main postulates of parasitism: (i) parasites are nutritionally dependent on the host, (ii) parasites cause the harm to their host, (iii) the host can evade parasites through immunity, and (iv) parasites must transmit (i.e., disperse) between hosts. To a parasite or pathogen, a host provides a suitable “habitat” through which they can move to complete various life stages, mirroring dispersal in metacommunities. Typically, host-parasite theory considers a single host-single parasite system. In reality, a host can potentially house multiple species, and parasites may be able to use multiple species of host, resulting in a metacommunity that occurs at multiple scales. My research aims to expand Anderson and May’s postulates in the context of a social host using modern metacommunity concepts. Using a community of kleptoparasitic invaders found in colonies of social and subsocial spiders that steal prey resources from their host, my PhD research is at the intersection of metacommunity ecology and host-parasite theory. First, we quantified energetic surplus in social spider colonies as a function of colony size, which may impose nutritional limits on parasitism. Next, we tested whether hosts engage in social immunity to limit kleptoparasite burden along an elevational gradient. Finally, we used DNA sequencing and laboratory experiments to quantify dispersal ability of kleptoparasites and harm to their host. We found that intermediately sized colonies have the greatest energetic surplus, but that kleptoparasite density is greatest in small colonies and in environments with greater productivity. Additionally, using genetic markers, we found that kleptoparasites can freely move between host colonies, while hosts are more limited in their dispersal abilities. Finally, we found that kleptoparasitism negatively affects host body condition, such that immature individuals may grow more slowly in parasitized colonies. This thesis has combined classic host-parasite theory with a modern metacommunity framework to demonstrate Anderson and May’s four postulates of parasitism in action across multiple levels of organization within a social system.
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