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Phylogeography and evolutionary patterns in Atlanto-Mediterranean butterflies: A hotspot of biodiversity in the context of global change
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Palaearctic butterflies are among the best studied organisms in the world due to their usefulness as bioindicators of climate and habitat change, relatively resolved identification and appreciation by the general public. Yet, many aspects of their biogeography and evolution remain unknown and novel, integrative research lines have proven useful at resolving old taxonomic uncertainties, at unveiling cryptic species or explaining how evolution has generated current diversity patterns. The Atlanto-Mediterranean area is the ideal laboratory where to study these phenomena. It encompasses the Iberian Peninsula and nearby southern France and the extreme north of Africa, and clearly stands-out as a hotspot of this diversity, combining both ancient lineages which survived major climatic and geological changes of the last 15 My, and newly arrived ones or recently differentiated forms. But to what extent have these butterflies been affected by changing geology and past climate phenomena and how has the partitioned character of the Atlanto-Mediterranean region affected the distribution of genetic diversity? While the possibilities are almost endless, in this thesis we chose three different endemic focal groups of butterflies so as to explore all these aspects and infer biogeographic patterns translational to a wider biotic community: 1) the Portuguese Dappled-White (Euchloe tagis, Pieridae) suffered from taxonomic oversplitting and uncertain phylogenetic placement whereas 2) the mechanisms and tempo of differentiation of too often considered conspecific Sooty-Coppers in Iberia (Lycaenidae) the widespread European Lycaena tityrus and its Iberian endemic counterpart Lycaena bleusei were in need of resolution after decades of uncertainty and conflicting published information. Finally, with project 3) we took the opportunity given by Argeformia Marbled-White butterflies (Nymphalidae, Satyrinae) to resolve the relationships among all taxa in the group and test the effect of major barriers to gene flow within the Atlanto-Mediterranean and beyond. Throughout all these projects, a broad integrative approach was preferred, including as much information as possible, but fundamentally coupling various genetic approaches using independent markers (mtDNA, nuDNA – all projects) under phylogenetic and phylogeographic frameworks and the inference of divergence-times among lineages, with one or several other tools such as up-to-date distribution of conflictive taxa (Lycaena, Melanargia), species distribution modelling (Lycaena, Melanargia), geometric morphometrics (Lycaena) and morphological analysis (Euchloe, Lycaena). While each case-study and methodology delivered interesting outputs at the taxonomic, evolutionary and biogeographic levels, contributing for the resolution of long-standing uncertainties regarding these butterflies, they may also be used in tandem to define broader biodiversity and evolutionary patterns. For instance, the case study of Euchloe tagis unveiled the Iberian Peninsula as a major reservoir of genetic diversity for this exceedingly old species and the Messinian Salinity Crisis (MSC) as a fracturing event in the divergence of populations in the Maghreb and Europe but we found the barrier imposed by the Gibraltar Strait is not fully impermeable and the Rif mountains of Morocco may have been back-colonised from Iberia after the MSC. In the case of Sooty-Coppers (Lycaena tityrus and L. bleusei), not only the very thorough analyses permitted a clear distribution, ecological, morphological and genetic distinction between them, it was also possible to infer their differentiation to be much older than hypothesized previously, raising new questions. With Argeformia Marbled-Whites, it was possible to identify the MSC and later Glacial-Interglacial cycles as major drivers of fundamentally allopatric differentiation, with interesting biogeographic connections such as Sicily with the Maghreb (M. occitanica), the contrasting fates of populations of both Maghrebian species (ines and occitanica) versus their mainland European counterparts, the isolation of M. arge in Italy and all their refugia across time.
Globally, these results constitute a major improvement regarding previous knowledge on the evolutionary relationships, taxonomy, stages of differentiation, ecology and chronology of cladogenesis in European butterflies, and particularly in the rich and important assemblage constituted by Atlanto-Mediterranean species. This becomes particularly relevant in the current context of accelerated climate-change, Man-made habitat depletion and the need to conserve genetic diversity for future generations.
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Atlanto-Mediterrâneo borboletas filogeografia análise integrativa taxonomia Atlanto-Mediterranean butterflies phylogeography integrative-analysis taxonomy