BackgroundEcological adaptation to host taxa is thought to result in mistletoe speciation via race formation. However, historical and ecological factors could also contribute to explain genetic structuring particularly when mistletoe host races are distributed allopatrically. Using sequence data from nuclear (ITS) and chloroplast (trnL-F) DNA, we investigate the genetic differentiation of 31 Psittacanthus schiedeanus (Loranthaceae) populations across the Mesoamerican species range. We conducted phylogenetic, population and spatial genetic analyses on 274 individuals of P. schiedeanus to gain insight of the evolutionary history of these populations. Species distribution modeling, isolation with migration and Bayesian inference methods were used to infer the evolutionary transition of mistletoe invasion, in which evolutionary scenarios were compared through posterior probabilities.ResultsOur analyses revealed shallow levels of population structure with three genetic groups present across the sample area. Nine haplotypes were identified after sequencing the trnL-F intergenic spacer. These haplotypes showed phylogeographic structure, with three groups with restricted gene flow corresponding to the distribution of individuals/populations separated by habitat (cloud forest localities from San Luis Potosí to northwestern Oaxaca and Chiapas, localities with xeric vegetation in central Oaxaca, and localities with tropical deciduous forests in Chiapas), with post-glacial population expansions and potentially corresponding to post-glacial invasion types. Similarly, 44 ITS ribotypes suggest phylogeographic structure, despite the fact that most frequent ribotypes are widespread indicating effective nuclear gene flow via pollen. Gene flow estimates, a significant genetic signal of demographic expansion, and range shifts under past climatic conditions predicted by species distribution modeling suggest post-glacial invasion of P. schiedeanus mistletoes to cloud forests. However, Approximate Bayesian Computation (ABC) analyses strongly supported a scenario of simultaneous divergence among the three groups isolated recently.ConclusionsOur results provide support for the predominant role of isolation and environmental factors in driving genetic differentiation of Mesoamerican parrot-flower mistletoes. The ABC results are consistent with a scenario of post-glacial mistletoe invasion, independent of host identity, and that habitat types recently isolated P. schiedeanus populations, accumulating slight phenotypic differences among genetic groups due to recent migration across habitats. Under this scenario, climatic fluctuations throughout the Pleistocene would have altered the distribution of suitable habitat for mistletoes throughout Mesoamerica leading to variation in population continuity and isolation. Our findings add to an understanding of the role of recent isolation and colonization in shaping cloud forest communities in the region.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0648...

Aim: The formation of the Trans-Mexican Volcanic Belt (TMVB) played an important role in driving inter-and intraspecific diversification at high elevations. However, Pleistocene climate changes and ecological factors might also contribute to plant genetic structuring along the volcanic belt. Here, we analysed phylogeographical patterns of the parrot-mistletoe Psittacanthus calyculatus to determine the relative contribution of these different factors. Location: Trans-Mexican Volcanic Belt. Methods: Using nuclear and chloroplast DNA sequence data for 370 individuals, we investigate the genetic differentiation of 35 populations across the species range.We conducted phylogenetic, population and spatial genetic analyses of P. calyculatus sequences along with ecological niche modelling and Bayesian inference methods to gain insight into the structuring of genetic variation of these populations.Results: Our analyses revealed population structure with three genetic groups corresponding to individuals from Oaxaca and those from the central-eastern and western TMVB regions. A significant genetic signal of demographic expansion, an eastto-west expansion predicted by species distribution modelling, and approximate Bayesian computation analyses strongly supported a scenario of habitat isolation and invasion of TMVB by P. calyculatus during the late-Pleistocene.Main conclusions: The genetic differentiation of P. calyculatus may be explained by the combined effects of (1) geographical isolation linked to the effects of the glacial/interglacial cycles and environmental factors, driving genetic differentiation from congeners into more xeric vegetation and (2) the invasion of TMVB from east to west, suggesting a role for both colonization and glacial/interglacial cycles models.

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The state of Oaxaca is positioned in a rather unique biogeographical position with the highest diversity of vascular plants in Mexico. The isolation of xeric valleys surrounded by complex mountain ranges in Oaxaca supplies an excellent opportunity to investigate the influence of the Pleistocene events on xeric species. To test for the alternative hypotheses of Pleistocene glacial refugia, we used sequences of two chloroplast markers to examine the phylogeographic patterns of the endemic mistletoe species Psittacanthus auriculatus (Loranthaceae) across its known range in Oaxaca and conducted ecological niche modeling (ENM) to explore changes of its distribution range through present, future, and palaeo periods. Our results revealed two groups corresponding to the distribution of individuals/populations from the northern locations (western valleys), and those from southern localities at central valleys of Oaxaca. A significant genetic signal of differentiation, demographic stability, and contraction of suitable habitat during the Last Glacial Maximum predicted by ENMs strongly supported a scenario of habitat fragmentation during the Late Pleistocene. We conclude that the genetic differentiation of P. auriculatus is consistent with a model of range contraction during glacial cycles and expansion during interglacials with no major range changes under future scenarios of climate change. The findings verified the profound effects of Pleistocene climatic fluctuations on this endemic mistletoe species, and the low genetic diversity within populations highlights, paradoxically, the urgency of preserving vulnerable populations of endemic yet parasitic mistletoes.

Background Hepatozoon canis is a protozoan transmitted to dogs and other wild carnivores by the ingestion of ticks containing mature oocysts and is considered the principal cause of canine hepatozoonosis in the world. Here, we examined ribosomal RNA 18S gene sequence variation to determine the genetic differences and phylogeographic diversity of H. canis from various geographical areas around the world. Methods We used 550 publicly available sequences of H. canis from 46 countries to assess haplotype relationships, geographical structure, genetic diversity indices, and relationships among populations. We performed neutrality tests and pairwise comparisons of fixation index (FST) values between groups and pairwise comparisons of FST values between populations. To determine whether populations are structured, analyses of molecular variance (AMOVAs) and spatial analysis of molecular variance (SAMOVA) were performed. Results The dataset of H. canis yielded 76 haplotypes. Differentiation among populations indicated that there is no phylogeographical structure (GST = 0.302 ± 0.0475). Moreover, when samples were grouped by continents a significant FST was obtained, meaning that populations were genetically differentiated. The AMOVA showed that 57.4% of the genetic variation was explained by differences within populations when all locations were treated as a single group and revealed that there is no population structure when populations are grouped into two, three, and four groups (FCT, p > 0.05), suggesting that dispersal between populations is high. SAMOVA revealed significant FCT values for groups K = 5. The Tajima’s D and Fu’s Fs show that populations have undergone recent expansion, and the mismatch distribution analysis showed population expansion (multimodal distribution). Conclusions The current molecular data confirmed that H. canis does not show phylogeographic or population structure. The haplotypes exhibit low genetic differentiation, suggesting a recent expansion due to gene flow among populations. These results provide pivotal information required for future detailed population genetic analysis or to establish control strategies of this parasite. Graphical abstract

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