Population genetics and species distribution modeling highlight conservation needs of the endemic trout from the Northern Sierra Madre Occidental

Recent climatic conditions are affecting biodiversity, particularly those species highly isolated and at their distribution limits such as trout (Oncorhynchus sp.) inhabiting the Northern Sierra Madre Occidental (NSMO) in Mexico, which is a current conservation concern due to their fragmented distribution and anthropogenic threads. Here, we compiled previously published data from 24 microsatellite loci from multiple localities of trout throughout the NSMO to construct geographic genetic structuring hypotheses. Our results confirm two genetically distinct subgroups within the NSMO corresponding to the northern populations from Rio Yaqui-Rio Bavispe and Rio Casas Grandes, and the southern population from Rio Yaqui-Rio Sirupa and Rio Conchos. In addition, we found a strong genetic differentiation between most of the locations sampled. We assembled species distribution models (SDM) to estimate the current distribution of trout. The SDM show that suitable environmental conditions may exist between northern and southern populations but are highly fragmented. In addition, association analyzes between F-ST and environmental factors show that the minimum temperature of the coldest month, the precipitation of wettest month, and the compound topographic index were responsible for the genetic structure. These results along with the limited mobility of the species, support limited connectivity as a possible explanation for current north and south arrangement of diversity. This study provides deep insights into the ecology and divergence processes within Northern Sierra Madre Occidental trout, and for the urgent development of effective conservation strategies for each of those lineages.