Boletín de la RSEHN. Sección Geológica

La cabra montesa ibérica (Capra pyrenaica, Schinz 1838) es un endemismo de la Península Ibérica que en los últimos siglos ha sufrido la pérdida de dos de sus cuatro subespecies (C .pyrenaica pyrenaica y C. pyrenaica lusitanica, actualmente extintas, C. pyrenaica hispanica y C. pyrenaica victoriae). La taxonomía para esta especie, al igual que para el género Capra, plantea un debate ya que la taxonomía habitualmente empleada se basa en caracteres morfológicos, tales como la morfología de los cuernos o el pelaje, que muchos autores sugieren que no son suficientes para definir una especie o subespecie. Los distintos problemas de conservación que plantea esta especie, así como su valor añadido por ser la pieza de caza mayor más importante de la Península, hacen que la gestión de esta especie sea una prioridad tanto desde el punto de vista biológico como socioeconómico. En este trabajo, se aplican las técnicas moleculares utilizadas en los estudios de ADN antiguo para investigar la historia paleo-genética de la cabra montesa en el yacimiento de Chaves (Huesca). Con los datos obtenidos se pretende analizar las relaciones filogenéticas entre las distintas subespecies de la Península así como las fluctuaciones demográficas y cambios en diversidad genética a través del tiempo. Este tipo de estudio es importante ya que nos proporciona información sobre los cambios genéticos sufridos por esta especie a través del tiempo y que han llevado a sus poblaciones a su situación actual. Por ello, esta información puede ayudar a tomar decisiones más fundamentadas para su gestión.

El estudio consistió en la amplificación y análisis de tres fragmentos del gen mitocondrial citocromo b de diecinueve muestras del yacimiento de Chaves de contextos neolíticos y paleolíticos. El análisis muestra, por un lado, una continuidad poblacional desde el Paleolítico hasta el presente en el yacimiento sin flujos genéticos externos y, por otro lado, una disminución de la diversidad genética desde el Paleolítico hasta el Neolítico sugiriendo que la reducción de biodiversidad que terminó con la extinción del bucardo ya estaba presente en el Neolítico. El estudio de las relaciones filogenéticas estimado por inferencia bayesiana agrupa en el mismo clado la cabra montesa y el íbice, apoyando este estudio la teoría de una sola ola de migración del género Capra en Europa seguido de una separación geográfica y especiación.

The Iberian wild goat (Capra pyrenaica, Schinz 1838) is an endemic species of the Iberian Peninsula that has recently suffered the loss of two of its four subspecies (C.pyrenaica pyrenaica, C. pyrenaica lusitanica, currently exctinct, C. pyrenaica hispanica and C. pyrenaica victoriae). The taxonomic position of this species has opened an intense debate among researchers; this is due to the fact that its classification has been based mainly on morphological characters, in particular on the horn morphology. It has been argued that horn morphology does not provide enough information to define a species. In addition, given its conservation concerns and the value it represents as a hunting species within the Peninsula, the wild goat is a complicated species to manage from a conservation perspective. In this study, we apply ancient DNA techniques in order to investigate the paleo-genetic history of the wild goat in the site of Chaves (Huesca, Spain) and re-analyse the controversial phylogenetic relationships among the different subspecies This information is important to analyse the population structure of the present goat populations to make educated conservation management decisions. For this, forty ancient goat bones were sampled (14 samples date back to the Neolithic and 26 to the Paleolithic). Three non overlapping fragments of the cytochrome b region were targeted and amplified with goat specific primers designed in this study with a total length of 264bp. The sequences recovered in this study were analysed together with modern sequences available in Genbank from the different goat subspecies and species using as outgroup Capreolus pygargus. The sequences were collapsed to haplotype and a haplotype network was constructed. In this, two groups were identified (see figure 1): one group with the modern Iberian Wild goats haplotypes (yellow) and the Capra ibex haplotype (green) and other group with the ancient haplotypes of Chaves (pink and blue). Whithin the latter, there is one haplotype that is found in the Paleolithic, in the Neolithic and in the modern goats. Thus, this analyses suggests that this haplotype, belonging to the recent extinct bucardo (Capra pyrenaica pyrenaica), would have survived since the Paleolithic until recent times. The fixation index Fst was calculated and does not show population differentiation, suggesting that there has been population continuity within Chaves all throughout the Paleolithic to the present with no evidence of gene flow. Both Haplotype diversity (Hd) and Nucleotide diversity (P) analyses show a decrease of genetic diversity from the Paleolithic to the Neolithic suggesting that the reduction in levels of diversity, that led to the wild goat extinction, was already evident in the Neolithic, perhaps as a consequence of a bottleneck during the Paleolithic/Neolithic transitions. The presence of the domestic animals at the site during the Neolithic may have affected to the wild goats population in the area. The phylogenetic relationship estimated by Bayesian inference do not show a clear structure (see figure 2). This pattern has been observed by other authors when studying the taxonomy of the genus Capra. It can be observed that the Iberian Wild goats and the Alpine Ibex are grouped together within clade 3. The monophyletic origin for both species is concordant with the theory of a single migration wave of wild goats in Europe followed by a geographic separation and speciation 6, 7, 8, 9. It can be also observed that the bucardo (Capra pyrenaica pyrenaica) seems to have a different common ancestor from the Alpine Ibex and the rest of modern Iberian Wild goats.