Hierarchical genetic structure shaped by topography in a narrow-endemic montane grasshopper

[Background]: Understanding the underlying processes shaping spatial patterns of genetic structure in free-ranging organisms is a central topic in evolutionary biology. Here, we aim to disentangle the relative importance of neutral (i.e. genetic drift) and local adaptation (i.e. ecological divergence) processes in the evolution of spatial genetic structure of the Morales grasshopper (Chorthippus saulcyi moralesi), a narrow-endemic taxon restricted to the Central Pyrenees. More specifically, we analysed range-wide patterns of genetic structure and tested whether they were shaped by geography (isolation-by-distance, IBD), topographic complexity and present and past habitat suitability models (isolation-byresistance, IBR), and environmental dissimilarity (isolation-by-environment, IBE).[Results]: Different clustering analyses revealed a deep genetic structure that was best explained by IBR based on topographic complexity. Our analyses did not reveal a significant role of IBE, a fact that may be due to low environmental variation among populations and/or consequence of other ecological factors not considered in this study are involved in local adaptation processes. IBR scenarios informed by current and past climate distribution models did not show either a significant impact on genetic differentiation after controlling for the effects of topographic complexity, which may indicate that they are not capturing well microhabitat structure in the present or the genetic signal left by dispersal routes defined by habitat corridors in the past.[Conclusions]: Overall, these results indicate that spatial patterns of genetic variation in our study system are primarily explained by neutral divergence and migration-drift equilibrium due to limited dispersal across abrupt reliefs, whereas environmental variation or spatial heterogeneity in habitat suitability associated with the complex topography of the region had no significant effect on genetic discontinuities after controlling for geography. Our study highlights the importance of considering a comprehensive suite of potential isolating mechanisms and analytical approaches in order to get robust inferences on the processes promoting genetic divergence of natural populations.VN was supported by a FPI pre-doctoral scholarship (BES-2012-053741) from Ministerio de Economía y Competitividad. JO was supported by Severo Ochoa (SEV-2012-0262) and Ramón y Cajal (RYC-2013-12501) research fellowships. This work received financial support from research grants CGL2011-25053 (Ministerio de Ciencia e Innovación and European Social Fund), POII10-0197-0167, PEII-2014-023-P (Junta de Comunidades de Castilla-La Mancha and European Social Fund) and UNCM08-1E-018 (European Regional Development Fund).We acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).Peer reviewe

Do climate-driven altitudinal range shifts explain the intraspecific diversification of a narrow ranging montane mammal, Taurus ground squirrels?

WOS: 000427518900008Understanding how species have responded to strong climatic fluctuations accompanying glacial-interglacial cycles is critical to predicting their likely responses to future climate change, and therefore can help guide conservation strategies. Using molecular phylogeography and ecological niche modelling, we aimed to understand how a newly recognized cryptic montane mammal (Spermophilus taurensis, Taurus ground squirrels) has responded to global climate changes through the Late Quaternary glacial-interglacial cycles as a means to better predict their likely responses to future climate change. Accordingly, 51 cytochrome b mitochondrial DNA sequences from throughout the known distribution of Taurus ground squirrels were used to investigate the intraspecific diversification. Besides molecular phylogeography, ecological niche modelling was also employed to get insights into possible climate-driven altitudinal range shifts in the past (the Last Glacial Maximum, 22 kya and the Mid-Holocene, 6 kya) and in the future (2050). Taurus ground squirrels survived the Late Quaternary glacial-interglacial cycles by altitudinal migrations without large geographical displacements. As warming occurred from the Last Glacial Maximum to the Mid-Holocene to the present, the potential distribution of Taurus ground squirrels shifted towards higher altitudes, resulting in a smaller range in the present. As warming continues, the potential distribution of Taurus ground squirrels will continue to shift towards higher altitudes, resulting in a much smaller range in the future. Particular sources of concern are the synergistic effects of future climate change and anthropogenic impacts on Taurus ground squirrels and their montane environments.Ahi Evran University Scientific Research Projects Coordination UnitAhi Evran University [PYO-FEN.4001.15.008]We would like to thank M. Cakir, M. Celik, H. Sevgili, and H. Yilmaz for sharing their field observations. This study was supported by the Ahi Evran University Scientific Research Projects Coordination Unit (Project Number: PYO-FEN.4001.15.008)

Pan-African phylogeny of Mus (subgenus Nannomys) reveals one of the most successful mammal radiations in Africa

International audienceBackground: Rodents of the genus Mus represent one of the most valuable biological models for biomedical and evolutionary research. Out of the four currently recognized subgenera, Nannomys (African pygmy mice, including the smallest rodents in the world) comprises the only original African lineage. Species of this subgenus became important models for the study of sex determination in mammals and they are also hosts of potentially dangerous pathogens. Nannomys ancestors colonized Africa from Asia at the end of Miocene and Eastern Africa should be considered as the place of their first radiation. In sharp contrast with this fact and despite the biological importance of Nannomys, the specimens from Eastern Africa were obviously under-represented in previous studies and the phylogenetic and distributional patterns were thus incomplete.Results: We performed comprehensive genetic analysis of 657 individuals of Nannomys collected at approximately 300 localities across the whole sub-Saharan Africa. Phylogenetic reconstructions based on mitochondrial (CYTB) and nuclear (IRBP) genes identified five species groups and three monotypic ancestral lineages. We provide evidence for important cryptic diversity and we defined and mapped the distribution of 27 molecular operational taxonomic units (MOTUs) that may correspond to presumable species. Biogeographical reconstructions based on data spanning all of Africa modified the previous evolutionary scenarios. First divergences occurred in Eastern African mountains soon after the colonization of the continent and the remnants of these old divergences still occur there, represented by long basal branches of M. (previously Muriculus) imberbis and two undescribed species from Ethiopia and Malawi. The radiation in drier lowland habitats associated with the decrease of body size is much younger, occurred mainly in a single lineage (called the minutoides group, and especially within the species M. minutoides), and was probably linked to aridification and climatic fluctuations in middle Pliocene/Pleistocene.Conclusions: We discovered very high cryptic diversity in African pygmy mice making the genus Mus one of the richest genera of African mammals. Our taxon sampling allowed reliable phylogenetic and biogeographic reconstructions that (together with detailed distributional data of individual MOTUs) provide a solid basis for further evolutionary, ecological and epidemiological studies of this important group of rodents