title: Hierarchical genetic structure shaped by topography in a narrow-endemic montane grasshopper.
abstract: 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-by-resistance, 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.
authors.affiliation: Grupo de Investigación de la Biodiversidad Genética y Cultural, Instituto de Investigación en Recursos Cinegéticos - IREC (CSIC, UCLM, JCCM), Ronda de Toledo 12, E-13071, Ciudad Real, Spain. victor.noguerales@csic.es.
authors.forename: Víctor
authors.initials: V
authors.lastname: Noguerales
authors.affiliation: Grupo de Investigación de la Biodiversidad Genética y Cultural, Instituto de Investigación en Recursos Cinegéticos - IREC (CSIC, UCLM, JCCM), Ronda de Toledo 12, E-13071, Ciudad Real, Spain.
authors.forename: Pedro J
authors.initials: PJ
authors.lastname: Cordero
authors.affiliation: Department of Integrative Ecology, Estación Biológica de Doñana (EBD-CSIC), Avda. Américo Vespucio s/n, E-41092, Seville, Spain.
authors.forename: Joaquín
authors.initials: J
authors.lastname: Ortego
mesh_terms: D000818:Animals; D002980:Climate; D016000:Cluster Analysis; D017753:Ecosystem; D019143:Evolution, Molecular; D005602:France; D051456:Gene Flow; D017344:Genes, Insect; D040961:Genetic Drift; D014644:Genetic Variation; D006110:Grasshoppers / Q000235:genetics*; D018895:Microsatellite Repeats; D008957:Models, Genetic; D058974:Phylogeography
keywords: Chorthippus saulcyi moralesi; Ecological niche modelling; Hierarchical genetic structure; Isolation by environment; Isolation by resistance; Landscape genetics; Pyrenees; Topographic complexity