The merger of formerly isolated lineages is hypothesized to occur in vertebrates under certain conditions. However, despite many demonstrated instances of introgression between taxa in secondary contact, examples of lineage mergers are rare. Preliminary mtDNA sequencing of a Malagasy passerine, Xanthomixis zosterops (Passeriformes: Bernieridae), indicated a possible instance of merging lineages. We tested the hypothesis that X. zosterops lineages are merging by comparing mtDNA sequence and microsatellite data, as well as mtDNA sequence data from host-specific feather lice in the genus Myrsidea (Phthiraptera: Menoponidae). Xanthomixis zosterops comprises four deeply divergent, broadly sympatric, cryptic mtDNA clades that likely began diverging approximately 3.6 million years ago. Despite this level of divergence, the microsatellite data indicate that the X. zosterops mtDNA clades are virtually panmictic. Three major phylogroups of Myrsidea were found, supporting previous allopatry of the X. zosterops clades. In combination, the datasets from X. zosterops and its Myrsidea document a potential merger of previously allopatric lineages that likely date to the Pliocene. This represents the first report of sympatric apparent hybridization among more than two terrestrial vertebrate lineages. Further, the mtDNA phylogeographic pattern of X. zosterops, namely the syntopy of more than two deeply divergent cryptic clades, appears to be a novel scenario among vertebrates. We highlight the value of gathering multiple types of data in phylogeographic studies to contribute to the study of vertebrate speciation.

We examine patterns of morphological and molecular genetic differentiation in the endemic Mentocrex kioloides complex of Madagascar. This forest-dwelling rail (often placed in Canirallus) is known from two subspecies: M. k. kioloides, which occurs in the island’s humid central and eastern forests; and M. k. berliozi, which occurs in the transitional dry deciduoushumid forests of the northwest. Two new specimens (an adult and a downy young) recently became available from limestone karst areas of the lowland central west, the adult of which is notably different in size and plumage coloration, as well as showing considerable genetic divergence, from the two recognized subspecies of M. kioloides. The central west animals are herein named as a species new to science, Mentocrex beankaensis, sp. nov.

A new feather mite genus Bernierinyssus gen. n. (Analgoidea: Pteronyssidae), associated with endemic Malagasy warblers (Passeriformes: Bernieridae), is proposed based on morphological evidence and DNA sequence data. Within this genus, we detected six mite species, including five new species described here: Bernierinyssus angulatus sp. n. from Crossleyia xanthophrys, B. bernieriae sp. n. from Bernieria madagascariensis, B. bifenestratus sp. n. from Hartertula flavoviridis, B. randiae sp. n. from Randia pseudozosterops, B. xanthomixis sp. n. from Xanthomixis zosterops (type host) and X. cinereiceps, and B. oxylabis (Mironov and Wauthy 2005) comb. n. (transferred from Pteronyssoides Hull). Phylogenetic relationships of these mites were nearly perfectly congruent with those of their hosts, indicating that ancestral Bernierinyssus probably co-dispersed to Madagascar on the common ancestor of Malagasy warblers and then cospeciated with their hosts. Species of Bernierinyssus are well-delimited based on several lines of evidence: morphology (clear among-specific differences in discrete characters), host associations (one mite species per one host species, except for B. xanthomixis), genetic distances (large COX1 barcoding gap between among- and within-species K2P distances: 8.22¨C12.38% vs 0¨C2.9%, respectively), and molecular phylogenetics (all species are well-supported, monophyletic clades). Our study suggests that species of the genus Bernierinyssus have evolved slower than their avian hosts or co-associated feather lice. Despite the discordance in the mitochondrial DNA evolutionary rates, speciation events in mites largely corresponded to bird species divergences, resulting in a nearly perfect correlation between mite and bird species richness (Eichler's Rule). The mite B. xanthomixis was associated with two avian species, but still formed two distinct shallow lineages (COX1 distance: 1.65%) separated by the host species. The nearly strict host-specificity pattern found in Bernierinyssus contrasts with that of continental feather mites, which tend to be less host-specific and have nearly equal proportions of single-host vs multi-host species.