Resumen de Conservation genetics of the critically endangered Montseny brook newt (Calotriton arnoldi)
Many scientists agree that we are achieving the midst of the sixth great mass extinction, what it has been named as ¿biodiversity crisis¿. Anthropogenic pressure is affecting both directly or indirectly natural environments. The amphibians are one of the most severally affected groups, and are the only ones catalogued globally at risk. The climate change, pollution, emerging diseases, habitat loss, introduction of invasive species and harvesting are probably the main factors that have contributed most to the overall decline of this group; in fact, surely the global decline of amphibians is due to the synergy of these factors. In that sense, conservation genetics will be a crucial tool for managing these endangered species. The main concern of this discipline is the identification and protection of the evolutionary potential of endangered species through understanding the importance of genetic diversity in preventing the extinction of species. The loss of genetic diversity and changes in the genetic structure can affect the long-term survival of a species, especially in small and endangered populations. One of the main threats affecting small populations is inbreeding depression due to genetic drift. This could drive the species to the extinction vortex. Molecular markers are a very useful tool in conservation genetics to evaluate and manage the genetic state of these populations. The Montseny brook newt (Calotriton arnoldi) is one of the most endangered vertebrates in Europe and it is classified as critically endangered by the International Union for Conservation of Nature (IUCN). This species is endemic to the Montseny Natural Park (NE Iberian Peninsula). Its disconnected populations are found within a restricted altitudinal range in seven geographically close brooks, occupying a total area of 8 km2. Moreover, its habitat is fragmented into two main sectors (eastern and western) on both sides of the Tordera river valley and separated by unsuitable terrestrial habitat. The current census population size of this species has been estimated at less than 1500 adult individuals. Recent human activities such as the extraction of large amounts of water for commercial purposes, deforestation and the building of tracks and roads are disturbing the habitat and are affecting the species negatively. The main goal of this thesis is to provide basic knowledge about the genetics of the Montseny brook newt to contribute towards the conservation of this emblematic species. The main aim of this thesis is to identify the different management units in order to apply appropriate conservation measures. To achieve this goal, we have explored the biogeography of the species (Chapter IV), the design of polymorphic markers (Chapter V), the characterization and genetic structure of its populations (Chapter VI) and the ex situ reproductive program (Chapter VII) by analyzing sequence data of two genes, one mitochondrial and one nuclear, together with 24 microsatellite markers. Within this thesis, we confirm the validity of the two species of Calotriton. Despite the limited distribution range of the Montseny brook newt compared to its sister species, the Pyrenean brook newt, C. arnoldi presents a high genetic structure. The morphological and molecular analyses suggest two geographically distinct population groups, to the east and west of the Tordera river valley, with no gene flow between them. The fifteen polymorphic loci described in this thesis, together with nine loci previously developed for C. asper that successfully cross-amplified in C. arnoldi, provided a powerful tool for the conservation genetics studies presented in this Thesis. The fragmentation of the species¿ natural habitat has resulted in a strong genetic division of population in two sectors, with no detectable migration between them. Although estimates of effective population size suggest critically low values for all populations, no evidence of high levels of inbreeding was found. Thus, the levels of genetic diversity of C. arnoldi are comparable to other amphibian species with much larger distribution ranges. This is one of the few species in which habitat fragmentation does not seem to have had a negative effect on an evolutionary time scale. It is suggested that this species could have developed reproductive strategies (eg, mate choice) to deal with their small populations. However, it is warned that fragmentation of natural habitats should be assessed as a distinct factor than habitat loss or degradation. The effect of both factors should be considered independently in planning strategies for the conservation of endangered species. The strong genetic structure observed in this species suggested that both sectors should be considered as two separate management units for conservation, both in situ and ex situ. In terms of ex situ conservation, it is concluded that, currently, the genetic diversity of captive populations and its representativeness are good but not optimal. New genetic material should be incorporated into the captive stock through the introduction of new unrelated individuals or their sperm. It is strongly recommended to maintain the two different breeding lines independently to avoid cross-fertilization between them and consequently possible outbreeding depression effects. In addition, it is recommended to keep an open-program to allow in situ continuous gene flow to captive populations to avoid adaptation to captivity in successive generations. The knowledge provided by this research is relevant to the conservation and management of the Montseny brook newt. The knowledge of the biology of this species is scarce due to the difficulty of observing and studying it in the wild. This information, however, is needed to assess the risk of extinction and thus to determine proper management actions. In this case, the genetic information has been of paramount importance to increase this knowledge, helping to fill some important gaps in the knowledge of the population dynamics of C. arnoldi and to provide some strategies and recommendations to be considered in its conservation plan.
