Author: Victor Frankel Vilches

Publisher:

Published: 2017

Total Pages:

ISBN-13:

"ABSTRACTBiological invaders typically lose parasites and pathogens from their native range but can acquire parasites from their native range or from their introduced range. As a result, host-parasite communities in invaded habitats need to be re-assembled - and this assembly can echo aspects of host-parasite associations in the native range. In Panama, the invasive red-rimmed melania snail Melanoides tuberculata (Muller 1774) is commonly infected by trematode parasites with complex life cycles. In this research, I investigate the ecological factors driving the transmission of parasites in an invaded community by considering the interactions of trematodes with different host species throughout their life cycle. I specifically consider the ecological processes that affect the extent to which biological invasions facilitate the transmission of introduced parasites in expanded geographic ranges.In the first chapter, I test the idea that "host diversity begets parasite diversity" in an introduced range by evaluating the influence of native bird hosts and habitat features on the abundance and species richness of trematode parasites infecting M. tuberculata in an invaded range. I show that the abundance and diversity of trematodes in M. tuberculata is strongly associated with the abundance and diversity of potential bird hosts in lake sites but found no evidence for this association from field surveys in stream sites. This system therefore shows how the assembly of host-parasite associations in new ranges is a complex mosaic of historical processes, novel associations and environmental effects. In the second chapter, I investigate how these trematodes described in the previous chapter interact with first intermediate snail hosts. Specifically, I consider the effect of parasitism by an invasive trematode, Centrocestus formosanus (Nishigori 1924), on snail reproduction and investigate the extent to which infected hosts exhibit plasticity in life-history strategies in response to parasitic castration. Field surveys showed that infected snails are castrated and unable to produce new offspring. However, infected snails could harbor juvenile snails in their brood pouch and thus provide maternal investment in brood development post-infection. Snails infected in laboratory had depressed growth rates and produced larger juveniles compared to uninfected snails. These results support the idea that trematode infection induces a plastic response in the energetic budget allocated to reproduction to boost reproduction at the cost of growth. I discuss the implications of the ability of snails to "make the best, if not the most, of a bad situation " In the third chapter, I consider how C. formosanus, which is transmitted by snails to fish, interacts with a community of potential fish hosts with which they do not share a common evolutionary history. Field surveys across three field sites in Gatun Lake, Panama, revealed that the invasive peacock bass, Cichla monoculus, was more commonly infected by C. formosanus than were three other common cichlid fishes. Laboratory infection experiments were conducted to determine if parasitism might be driven by differential encounter to parasites or by differential infection susceptibility/preference across different host species. In all cases, the peacock bass exhibited higher infection rates relative to other potential fish hosts. These data provide support that an introduced 'generalist' parasite shows specialization on a novel host, which could be the product of rapid local adaptation post-invasion. As a whole, this research illustrates the ecological complexity associated with the establishment of parasites with complex life cycles in new environments, creating a mosaic of interactions with different host species that are driven by different ecological and evolutionary processes." --