Evidence of cryptic speciation in mesostigmatid mites from South Africa

Abstract

Laelaps giganteus and Laelaps muricola (Mesostigmata; Laelapidae) are widespread and locally abundant host generalists on small mammals in southern Africa. The large host range and complex life history of these ectoparasites may allude to possible intraspecific cryptic diversity in these taxa. To assess genetic and morphological diversity in L. giganteus and L. muricola, we sampled 228 rodents at eight localities in South Africa. This sample included nine previously recorded host species and on these, L. muricola was only recorded from Mastomys natalensis and Micaelamys namaquensis while L. giganteus was found on Rhabdomys dilectus and Lemniscomys rosalia. Phylogenetic analyses of partial mtDNA cytochrome oxidase subunit I (COI) and nuclear ITS1 data strongly supported the recognition of L. giganteus and L. muricola, a scenario partly supported by the Tropomyosin intron. Strong support for evolutionary distinct lineages within L. giganteus is found: L. giganteus lineage 1 is confined to R. dilectus and L. giganteus lineage 2 is confined to L. rosalia. These host specific monophyletic lineages were also separated by 9.84% mtDNA sequence divergence and 3.44% nuclear DNA sequence divergence. Since quantitative morphometric analyses were not congruent with these findings, these two lineages more than likely represent cryptic species.

Comparative phylogeography of parasitic Laelaps mites contribute new insights into the specialist-generalist variation hypothesis (SGVH)

“…To test the paradigms associated with the SGVH we compare the genetic geographic structures of two evolutionary closely related nest bound ecotoparasite mite species, Laelaps gigantues and L. muricola [6, 13] . The two parasite species have overlapping distributions in southern Africa and it seems reasonable to suggest that samples taken from the same geographic locality will be broadly subjected to similar abiotic influences derived from the external environment.…”

“…The two parasite species have overlapping distributions in southern Africa and it seems reasonable to suggest that samples taken from the same geographic locality will be broadly subjected to similar abiotic influences derived from the external environment. Since the two species are also morphologically similar [6, 22] they most likely have the same intrinsic abilities to disperse across the landscape. Both Laelaps species occur for short periods on the hosts for feeding, have low prevalence’s on their hosts [6, 23] and are characterized by female sex bias dispersal [18, 24].…”

“…Since the two species are also morphologically similar [6, 22] they most likely have the same intrinsic abilities to disperse across the landscape. Both Laelaps species occur for short periods on the hosts for feeding, have low prevalence’s on their hosts [6, 23] and are characterized by female sex bias dispersal [18, 24]. The most obvious variables that can influence neutral genetic diversity and population structure in these taxa are linked to their individual level of host specificity [6] and the differential intrinsic abilities of the various host species to move across the landscape [15, 25, 26].…”

“…Laelaps giganteus is a host specialist that is found exclusively on the four striped mouse genus Rhabdomys [6]. The mite shows a significant signal of co-divergence [13] with the four Rhabdomys species recognized in the region [26], and each Rhabdomys species harbors their own unique L. giganteus lineage [13].…”

“…The generalist nature of L. muricola is confirmed by the absence of strong host association at the genetic level [6], suggesting that the parasites on the different host are not structured by host species. The dispersal capabilities of the various hosts can be inferred from previous phylogeographic investigations [15, 25].…”