Effects of environmental changes during the quaternary on the distribution of extant species :|bthe case of the butterflies "Erebia triaria" and "E. palarica"

Abstract

[Abstract] Although phylogeography has only recently emerged as a research field in its own right, several models are already treated as fact and are widely accepted to be true. My thesis critically examines three of these theories. First, I considered the widespread use of molecular rates of nucleotide substitution as a methodological approach for the timing of historical events and/or estimation of demographic parameters. 1 assess the value of this approach for the subfamily of butterflies Satyrinae (Nymphalidae) concluding that it is improper and that relative parameters are more realistic than absolute estimates when dealing with DNA datasets. Second, I conducted an extensive literary review to test the assumption that the three southern European peninsulas acted as three isolated glacial refugia for most of the temperate European fauna during the Quaternary period. Genetic patterns, palaeontological evidence and geographic distributions imply that many animal taxa may actually have sought refuge in North Africa at this time. Finally, because the Iberian Peninsula is now in vogue as several taxa have shown evidence of isolated glacial refugia within it, I examined in detail specit7c examples from this region. I have evaluated the geographic pattern of mtDNA diversity and phylogeny in the populations of two butterflies, Erebia triaria de Prunner 1798 and E. palarica Chapman 1905 (Nymphalidae: Satyrinae), from formerly glaciated areas of NW Spain, in relation to reported ages for the last deglaciation and information about the progress of vegetation since then. The genealogy of the haplotypes clearly shows associations between specific clades and geographic location in both species. The low degree of genetic variation found in the current genetic pattern of E. palarica appears strongly influenced by recent bottlenecks and the narrow distribution of this endemic taxon. The colonization history of E. triaria is interpreted as following two temporal stages and at least two isolated glacial refugia, whose mitochondrial lineages currently meet in NW Iberia. In addition, estimates of genetic divergence between E. triaria mtDNA haplotypes and analyses on population ditterentiation through microsatellite nuclear loci are used to evaluate the taxonomic definition of one particular population (Xistral), previously defined as a subspecies, and draw attention to its status as a conservation unit.

[Resumen]La filogeografía es un área de estudio reciente y multidisciplinar que trata de inferir los procesos microevolutivos causantes de la aparición de distintas variantes biológicas en áreas geográficas determinadas. El primer artículo de esta tesis cuestiona el modelo clásico de tres refugios glaciares para la fauna europea. Tras una revisión bibliográfica, se aporta evidencia empírica a favor de la hipótesis del Norte de África como posible refugio glacial Cuaternario para algunas especies. El grueso de la tesis se centra en la filogeografía de dos mariposas del género Erebia (Nymphalidae: Satyrinae), para lo cual se desarrollaron marcadores mitocondriales apropiados. Los artículos segundo y tercero de la tesis, evaluaron su utilidad a distintos niveles taxonómicos, y revisaron sus tasas de evolución molecular, respectivamente. Así, la región control mitocondrial es útil en Lepidoptera tanto a nivel poblacional como interespecífico, conteniendo información tanto desde punto de vista de genética de poblaciones como filogenético. El tercer artículo advierte contra el uso indiscriminado de la tasa 2.3% de divergencia de secuencia mitocondrial por millón de años, ampliamente asumido en estudios filogenéticos en entomología. Secuencias de ADN mitocondrial (región control + COI) de Erebia palarica de una misma localidad en años consecutivos mostraron el patrón esperado bajo un ciclo de vida anual, conformando el cuarto artículo. Secuencias de ADN mitocondrial de tres poblaciones aisladas de Erebia palarica, endémica del N.O. Ibérico, mostraron diferenciación significativa desde el punto de genética de poblaciones, si bien ninguna de las tres poblaciones constituyeron un grupo monofilético. El artículo quinto propone que las tres poblaciones buscaron refugio a baja altitud durante los periodos fríos del Cuaternario, desde donde ascendieron tras las deglaciaciones.