Exploring mechanisms that shape Siphonaptera composition and distribution patterns on small mammals across South Africa

[摘要] ENGLISH ABSTRACT: Fleas (Siphonaptera) are obligate ectoparasites of mammals and birds. Due to their economic importance as disease vectors, most contemporary studies on macroparasites now also consider the spatial variation of parasite communities and the underlying mechanisms involved in shaping current distribution patterns. Fleas differ in life history traits, such as the level of host specificity and microhabitat preferences, which can result in differential evolutionary responses to similar abiotic events. The main objectives of this study are to investigate: (1) the influence of vicariance and host association on the genetic structure of two generalist flea species, Listropsylla agrippinae, and Chiastopsylla rossi. The taxa differ in the time spent on the host (fur vs. nest) and the level of host specificity; (2) the taxonomy of Dinopsyllus ellobius to determine whether more than one species exist and if so to then elucidate the mechanisms of speciation; and (3) the influence of flea life history on species distribution model performance and see if the relative importance of predictor variables differ between species with different life histories. A total of 1423 small mammals were brushed to collect 2906 flea individuals originating from 31 geographically distinct localities throughout South Africa (SA). Phylogeographic structure of L. agrippinae and C. rossi were determined by making use of 315 mitochondrial COII (mtDNA) and 174 nuclear EF1-α (nDNA) sequences. The more host specific fur flea, L. agrippinae, displayed pronounced spatial phylogeographic structure, based on mtDNA, which was congruent with host vicariance in the region. In contrast, the more generalist nest flea, C. rossi, showed a higher level of inter-populational divergence, based on mtDNA and nDNA, and this may be attributed to comparatively higher restrictions to dispersal when compared to the more specific fur flea. In an attempt to resolve the taxonomy of D. ellobius, 151 mtDNA and 68 nDNA alleles were generated from individuals meeting the morphological description of D. ellobius. Two distinct D. ellobius lineages that corresponded to previously described species (D. ellobius and D. abaris) were recorded. The results indicate that the two species indeed differ morphologically and based on the distribution of the two species it was concluded that the diversification could be a result of climate driven vicariance and subsequent ecological segregation according to habitat use. Locality records from Segerman (1995) were digitized and used as background data in species distribution modelling. Sufficient information was obtained for 21 flea species. A total of 68 climatic and landscape feature predictor variables were obtained and through a process of elimination, 19 variables were ultimately used. Model performance was good to excellent on average and the contribution of climate and landscape feature variables differed between fleas with different life histories. Historical and contemporary climate has the most prominent effect on flea distribution at the regional scale, but the level of host association influences the phylogeographic pattern of fleas. This study provides the first evidence of congruent phylogeographic patterns between a generalist temporary parasite and its hosts. Our findings provide further support for the notion that more than one species exist within the D. ellobius complex and that speciation is a result of complex interactions. The study also provides novel data on the role of environmental variables in shaping the geographic distribution of flea species with different life histories. With the anticipated rise in flea-borne diseases worldwide, due to changes in vector distribution, the study further emphasize the need for studying the mechanisms involved in shaping flea distribution patterns.

[发布机构] Stellenbosch University