Author
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BUDISCHAK, SARAH - University Of Georgia |
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Hoberg, Eric |
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Abrams, Arthur |
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JOLLES, ANNA - Oregon State University |
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EZENWA, VANESSA - University Of Georgia |
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Submitted to: Journal of Animal Ecology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 4/26/2016 Publication Date: N/A Citation: N/A Interpretive Summary: Community assembly is a fundamental process that has long been a central focus of ecology. Extending community assembly theory to assemblages of parasites co-infecting hosts, we experimentally removed gastrointestinal nematodes from African buffalo (Syncerus caffer). We compared the composition of reassembled communities to parasite communities of control hosts, and then tested the alternative hypotheses that parasite communities are random vs. non-random assemblages. We predicted that if assembly is non-random, community composition in treated hosts would differ from controls, vary with reassembly time, and deviate from environmental patterns. If random, we expected no differences between treated controls, no temporal patterns in community composition with reassembly time, and no deviations from environmental patterns. Interestingly, our data suggest that parasite communities are initially non-random assemblages, but subsequently that environmental availability of infective stages drives assembly. Specifically, we found that early on in the reassembly process, treated hosts had more diverse communities and preferentially accumulated a less common species, rather than randomly accumulating parasites based on their environmental availability. However, with increasing reassembly time, parasite communities of treated hosts progressively resembled control communities and the environmental availability of infective stages. Our results suggest there is a high degree of resiliency and environmental dependence to the nematode communities of buffalo, but that non-random factors might influence parasite communities early in the assembly process. This study reveals the dynamic nature of the parasite reinfection process by showing that, initially, parasite communities are non-random, but later represent random collections of the environmentally available infective parasite stages. Implications of these observations suggest that responses designed to control parasites in ungulates need to account for the timing and process of community assembly. Results are of interest and significance to parasitologists, ecologists, wildlife disease biologists and the veterinary community involved in the management of helminth infections among ungulates. Technical Abstract: 1. Community assembly is a fundamental process that has long been a central focus in ecology. Extending community assembly theory to communities of co-infecting parasites, we used a gastrointestinal nematode removal experiment in free-ranging African buffalo to examine community assembly patterns and processes. 2. We first asked whether reassembled communities differ from undisturbed communities by comparing anthelmintic-treated and control hosts. Next, we examined the temporal dynamics of assembly using a cross-section of communities that reassembled for different periods of time since last experimental removal. Next, we tested for evidence of assembly processes that might drive such reassembly patterns: environmental filtering based on host traits (i.e. habitat patches), interspecific interactions, priority effects, and chance dispersal from the environmental pool of infective stages (i.e. the regional species pool). 3. On average, reassembled parasite communities had lower abundances, but were more diverse and even, and these patterns varied tightly with reassembly time. Over time, the communities within treated hosts progressively resembled controls as diversity and evenness decreased while total abundance increased. Notably, our experimental removal treatment allowed us to attribute observed differences in abundance, diversity, and evenness to the process of community assembly. 4. During early reassembly, parasite accumulation was biased towards a subordinate species and, by excluding stochastic assembly processes (i.e. chance dispersal and priority effects), we were able determine that early assembly is deterministic. Later in the reassembly process, we established that each of the host traits we examined as well as stochastic dispersal from the environmental pool infective stages can affect community composition. 5. Overall, our results suggest there is a high degree of resiliency and environmental dependence to the worm communities of buffalo. More generally, our data show both deterministic and stochastic processes may play a role in the assembly of parasite communities of wild hosts, but the importance of these processes may vary over time, therefore the best strategy for managing reassembling parasite communities may also need to shift over time. |
