Ecological speciation in Nolina parviflora (Asparagaceae): lacking spatial connectivity along of the Trans-Mexican Volcanic Belt

The importance of environmental conditions in maintaining lineage identity in Epithelantha (Cactaceae)

The use of environmental variables to explain the evolution of lineages has gained relevance in recent studies. Additionally, it has allowed the recognition of species by adding more characters to morphological and molecular information. This study focuses on identifying environmental and landscape variables that have acted as barriers that could have influenced the evolution of Epithelantha species and its close genera.Our results show that soil pH, isothermality, temperature seasonality, and annual precipitation have a significant phylogenetic signal for Epithelantha. Soil type and landforms are also relevant as ecological barriers that maintain the identity of Epithelantha species.The variables associated with the soil (pH) have influenced the evolution of Epithelantha and probably in other genera of Cactaceae. Additionally, Epithelantha is frequent in the piedmont and haplic kastanozems. Bioclimatic variables reinforce the recognition of E. micromeris, and E. cryptica as independent species. Therefore, ecology can be considered as a factor to explain the high level of endemism in Cactaceae.

Landscape genomics provides evidence of climate-associated genetic variation in Mexican populations of Quercus rugosa

Local adaptation is a critical evolutionary process that allows plants to grow better in their local compared to non-native habitat and results in species-wide geographic patterns of adaptive genetic variation. For forest tree species with a long generation time, this spatial genetic heterogeneity can shape the ability of trees to respond to rapid climate change. Here, we identify genomic variation that may confer local environmental adaptations and then predict the extent of adaptive mismatch under future climate as a tool for forest restoration or management of the widely distributed high-elevation oak species Quercus rugosa in Mexico. Using genotyping by sequencing, we identified 5,354 single nucleotide polymorphisms (SNPs) genotyped from 103 individuals across 17 sites in the Trans-Mexican Volcanic Belt, and, after controlling for neutral genetic structure, we detected 74 F ST outlier SNPs and 97 SNPs associated with climate variation. Then, we deployed a nonlinear multivariate model, Gradient Forests, to map turnover in allele frequencies along environmental gradients and predict areas most sensitive to climate change. We found that spatial patterns of genetic variation were most strongly associated with precipitation seasonality and geographic distance. We identified regions of contemporary genetic and climatic similarities and predicted regions where future populations of Q. rugosa might be at risk due to high expected rate of climate change. Our findings provide preliminary details for future management strategies of Q. rugosa in Mexico and also illustrate how a landscape genomic approach can provide a useful tool for conservation and resource management strategies.

Pleistocene glacial cycles drive isolation, gene flow and speciation in the high-elevation Andes

Mountain ranges are amongst the most species-rich habitats, with many large and rapid evolutionary radiations. The tempo and mode of diversification in these systems are key unanswered questions in evolutionary biology. Here we study the Andean Lupinus radiation to understand the processes driving very rapid diversification in montane systems. We use genomic and transcriptomic data of multiple species and populations, and apply phylogenomic and demographic analyses to test whether diversification proceeded without interspecific gene flow - as expected if Andean orogeny and geographic isolation were the main drivers of diversification - or if diversification was accompanied by gene flow, in which case other processes were probably involved. We uncover several episodes of gene flow between species, including very recent events likely to have been prompted by changes in habitat connectivity during Pleistocene glacial cycles. Furthermore, we find that gene flow between species was heterogeneously distributed across the genome. We argue that exceptionally fast diversification of Andean Lupinus was partly a result of Late Pleistocene glacial cycles, with associated cycles of expansion and contraction driving geographic isolation or secondary contact of species. Furthermore, heterogeneous gene flow across the genome suggests a role for selection and ecological speciation in rapid diversification in this system.