Molecular ecology of the Egyptian mongoose (Herpestes ichneumon) in Portugal =Ecologia molecular do sacarrabos (Herpestes ichneumon) em Portugal

摘要

The central challenge on studying population expansions is to provide an in-depth characterization of the expanding individuals and their dynamics across invaded ranges. By combining ecological data with molecular techniques, one can understand those dynamics, population structure and the biology of expanding species. The general aim of this thesis was assessing which factors contributed for the expansion of the Egyptian mongoose, analyse the genetic structure and population genetics of this expanding species and relate landscape factors with the gene flow within the mongoose population of the Iberian Peninsula. The expansion was evaluated across 1980-1990, 1990-2000 and 2000-2010, by projecting presence/absence data of the species and proposing four explanatory hypotheses gathering environmental, geographic and anthropogenic factors. The results suggested that land-use alterations coupled with temperature and rainfall variations over the decades were the main drivers promoting the mongoose expansion. Moreover, geographic barriers and human infrastructures acted as barriers towards the Egyptian mongoose expansion. Genetic patterns, demographic history and genetic structure of the species were evaluated by mitochondrial DNA and microsatellite markers. The distribution of mitochondrial diversity fitted the pattern of a historically diversified population in southern Iberian Peninsula, from where recent dispersals into northern areas occurred. Long-term dispersal migrants from south towards northern areas were evidenced by 1) higher levels of haplotype and nucleotide diversities in the northern areas, 2) heterogeneous distribution of population genetic differentiation, and 3) weak signal for isolation by distance. Sudden and spatial expansion scenarios were reinforced by mismatch analysis and marginally supported by neutrality tests. On the other hand, microsatellite analyses evidenced a central-northern subpopulation (CNorth) and a southern subpopulation (S) with significant differentiation. Allelic frequencies, levels of heterozygosity and evidences of bottleneck occurred after the expansion in CNorth supported the recent northwards range expansion, with S individuals contributing with a higher allelic diversity. Inversely to mitochondrial DNA, microsatellites evidenced a pattern of isolation by distance together with a pattern of isolation by barrier due to the Tagus River, which was identified as a semi-barrier towards gene flow which possibly caused the presence of the two genetic clusters. The presence of S and CNorth in opposite locations of their general distribution might be related with long-range dispersals. A landscape genetics approach was implemented under the original and reciprocal causal modelling frameworks with the objective of investigate the relation between genetic structure and landscape aspects. Isolation by distance was the best model identified by original causal modelling explaining genetic patterns within the mongoose population. The newer reciprocal causal modelling approach identified high shrub cover at middle elevations as the best model. These results demonstrate the high dependency of the Egyptian mongoose on ecosystems dominated by Mediterranean shrub cover. The recent land-use changes in Portugal related with rural abandonment promoted the connectivity among the mongoose populations in areas with high shrub cover at middle elevations, where anthropogenic disturbance is lower. This thesis represents a holistic study of the dynamic patterns of this expanding species, with new and essential findings of the Egyptian mongoose in the Iberian Peninsula. The results should be perceived as a model for expanding species under a changing environment, especially Mediterranean carnivores, with a special emphasis on assessing which key factors act as drivers for the expansion of species, the effect of the alterations of species' ranges on their genetic patterns, and ultimately how landscape influences gene flow of those species.