Marine blue mussels (Mytilus spp.) are widespread species that exhibit an antitropical distribution with five species occurring in the Northern Hemisphere (M. trossulus, M. edulis, M. galloprovincialis, M. californianus and M. coruscus) and three in the Southern Hemisphere (M. galloprovincialis, M. chilensis and M. platensis). Species limits in this group remain controversial, in particular for those forms that live in South America. Here we investigated structural characteristics of marine mussels mitogenomes, based on published F mtDNA sequences of Northern Hemisphere species and two newly sequenced South American genomes, one from the Atlantic M. platensis and another from the Pacific M. chilensis. These mitogenomes exhibited similar architecture to those of other genomes of Mytilus, including the presence of the Atp8 gene, which is missing in most of the other bivalves. Our evolutionary analysis of mitochondrial genes indicates that purifying selection is the predominant force shaping the evolution of the coding genes. Results of our phylogenetic analyses supported the monophyly of Pteriomorphia and fully resolved the phylogenetic relationships among its five orders. Finally, the low genetic divergence of specimens assigned to M. chilensis and M. platensis suggests that these South American marine mussels represent conspecific variants rather than distinct species.

Extensive livestock production and urbanization entail modifications of natural landscapes, including installation of fences, development of agriculture, urbanization of natural areas, and construction of roads and infrastructure that, together, impact native fauna. Here, we evaluate the diversity and genetic structure of endemic guanacos (Lama guanicoe) of the Monte and Patagonian Steppe of central Argentina, which have been reduced and displaced by sheep ranching and other impacts of human activities. Analyses of genetic variation of microsatellite loci and d-loop revealed high levels of genetic variation and latitudinal segregation of mitochondrial haplotypes. There were indications of at least two historical populations in the Monte and the Patagonian Steppe based on shared haplotypes and shared demographic history among localities. Currently, guanacos are structured into three groups that were probably reconnected relatively recently, possibly facilitated by a reduction of sheep and livestock in recent decades and a recovery of the guanaco populations. These results provide evidence of the genetic effects of livestock activity and urbanization on wild herbivore populations, which were possibly exacerbated by an arid environment with limited productive areas. The results highlight the importance of enacting conservation management plans to ensure the persistence of ancestral and ecologically functional populations of guanacos.

Adaptation to warming conditions involves increased heat tolerance and metabolic changes to reduce maintenance costs and maximize biological functions close to fitness. Evidence shows that energy metabolism evolves in response to warming conditions, but we know little about how heat stress intensity determines the evolutionary responses of metabolism and life history traits. Here, we evaluated the evolutionary responses of energy metabolism and life-history traits to artificial selection for increasing heat tolerance in Drosophila subobscura, using 2 protocols to measure and select heat tolerance: slow and fast ramping protocols. We found that the increase in heat tolerance was associated with reduced activity of the enzymes involved in the glucose-6-phosphate branchpoint but no changes of the metabolic rate in selected lines. We also found that the evolution of increased heat tolerance increased the early fecundity in selected lines and increased the egg-to-adult viability only in the slow-ramping selected lines. This work shows heat tolerance can evolve under different thermal scenarios but with different evolutionary outcomes on associated traits depending on the heat stress intensity. Therefore, spatial and temporal variability of thermal stress intensity should be taken into account to understand and predict the adaptive response to ongoing and future climatic conditions.

Although guanacos (Lama guanicoe) are widely distributed throughout much of their historic range, they are often restricted to small, isolated populations that are at risk of inbreeding and loss of genetic diversity. Here we document and interpret baseline patterns of genetic variation in a guanaco population inhabiting in the Bolivian Chaco that is threatened by hunting and habitat degradation. The region, once open grasslands, is dominated by dense shrubs, the result of livestock grazing. The most-recent census identified only 74 individuals and is designated as at ‘risk of extinction’ by the Bolivian government. We assessed the population’s genetic health and uniqueness from the genetic patterns of 16 microsatellite loci, the Hyper-variable Domain I of the mitochondrial Control Region and SRY gene with 29 fecal samples. We identified 19 male and 10 female unique individuals. Microsatellite variation (Ho = 0.64) was similar to larger, less-isolated populations. However, the estimated effective population size was low and consistent with the continuing loss of allelic variation. The two observed mtDNA haplotypes are common in other L. g. guanicoe populations. Although we documented moderate genetic diversity, gene flow among Bolivian and Paraguayan guanaco Chaco populations should be assessed and integrated into explicit conservation management plans.