More Like this

1. Has past climate change affected cold-specialized species differentially through space and time?

   https://doi.org/10.1111/syen.12341  

   Schoville, S.D. ; Bougie, T.A. ; Dudko, R.Y. ; Medeiros, M.J. ( January 2019 , Systematic entomology)

   Quaternary climate change has been strongly linked to distributional shifts and recent species diversification. Montane species, in particular, have experienced enhanced isolation and rapid genetic divergence during glacial fluctuations, and these processes have resulted in a disproportionate number of neo-endemic species forming in high elevation habitats. In temperate montane environments, a general model of alpine population history is well supported, where cold-specialized species track favorable climate conditions downslope during glacial episodes and upslope during warmer interglacial periods, which leads to a climate-driven population or species diversification pump. However, it remains unclear how geography mediates distributional changes and whether certain episodes of glacial history have differentially impacted rates of diversification. We address these questions by examining phylogenomic data in a North American clade of flightless, cold-specialized insects, the ice crawlers (Insecta: Grylloblattodea: Grylloblattidae: Grylloblatta). These low vagility organisms have the potential to reveal highly localized refugia and patterns of spatial recolonization, as well as a longer history of in situ diversification. Using continuous phylogeographic analysis of species groups, we show that all species tend to retreat to nearby low elevation habitats across western North America during episodes of glaciation, but species at high latitude exhibit larger distributional shifts. Lineage diversification wasmore »examined over the course of the Neogene and Quaternary periods, with statistical analysis supporting a direct association between climate variation and diversification rate. Major increases in lineage diversification appear correlated to warm and dry periods, rather than extreme glacial events. Finally, we identify substantial cryptic diversity among ice crawlers, leading to high endemism across their range. This diversity provides new insights into highly localized glacial refugia for cold-specialized species across western North America.« less
2. Is Phylogeographic Congruence Predicted by Historical Habitat Stability, or Ecological Co-associations?

   https://doi.org/10.1093/isd/ixab018  

   Garrick, R.C. ; Hyseni, C. ; Arantes, Í.C. ; Zachos, L.G. ; Zee, P.C. ; Oliver, J.C ( April 2021 , Insect systematics and diversity)

   Lozier, J (Ed.)

   Comparative phylogeographic studies can distinguish between idiosyncratic and community-wide responses to past environmental change. However, to date, the impacts of species interactions have been largely overlooked. Here we used non-genetic data to characterize two competing scenarios about expected levels of congruence among five deadwood-associated (saproxylic) invertebrate species (i.e., a wood-feeding cockroach, termite, and beetle; a predatory centipede, and a detritivorous millipede) from the southern Appalachian Mountains—a globally recognized center of endemism. Under one scenario, abiotic factors primarily drove species’ responses, with predicted congruence based on the spatial overlap of climatically stable habitat areas estimated for each species via ecological niche modeling. The second scenario considered biotic factors to be most influential, with proxies for species interactions used to predict congruence. Analyses of mitochondrial and nuclear DNA sequences focused on four axes of comparison: the number and geographic distribution of distinct spatial-genetic clusters, phylogeographic structure, changes in effective population size, and historical gene flow dynamics. Overall, we found stronger support for the ecological co-associations scenario, suggesting an important influence of biotic factors in constraining or facilitating species’ responses to Pleistocene climatic cycles. However, there was an imperfect fit between predictions and outcomes of genetic data analyses. Thus, while thought-provoking, conclusions remainmore »tentative until additional data on species interactions becomes available. Ultimately, the approaches presented here advance comparative phylogeography by expanding the scope of inferences beyond solely considering abiotic drivers, which we believe is too simplistic. This work also provides conservation-relevant insights into the evolutionary history of a functionally important ecological community.« less
3. Recent lineage diversification in a venomous snake through dispersal across the Amazon River

   GIBBS, HL. ( January 2018 , Biological Journal of the Linnean Society)

   Identifying the evolutionary and ecological mechanisms that drive lineage diversification in the species-rich tropics is of broad interest to evolutionary biologists. Here, we use phylogeographic and demographic analyses of genomic scale RADseq data to assess the impact of a large geographic feature, the Amazon River, on lineage formation in a venomous pitviper, Bothrops atrox. We compared genetic differentiation in samples from four sites near Santarem, Brazil that spanned the Amazon and represented major habitat types. A species delimitation analysis identified each population as a distinct evolutionary lineage while a species tree analysis with populations as taxa revealed a phylogenetic tree consistent with dispersal across the Amazon from north to south. Phylogenetic analyses of mtDNA variation confirmed this pattern and suggest that all lineages originated during the mid- to late-Pleistocene. Historical demographic analyses support a population model of lineage formation through isolation between lineages with low ongoing migration between large populations and reject a model of differentiation through isolation by distance alone. Our results provide a rare example of a phylogeographic pattern demonstrating dispersal over evolutionary time scales across a large tropical river and suggest a role for the Amazon River as a driver of in-situ divergence by both impeding (butmore »not preventing) gene flow and through parapatric differentiation along an ecological gradient.« less
4. Patterns of speciation are similar across mountainous and lowland regions for a Neotropical plant radiation (Costaceae: Costus)

   https://doi.org/10.1111/evo.14108  

   Vargas, Oscar M. ; Goldston, Brittany ; Grossenbacher, Dena L. ; Kay, Kathleen M. ( December 2020 , Evolution)

   Emerson, B. (Ed.)

   High species richness and endemism in tropical mountains are recognized as major contributors to the latitudinal diversity gradient. The processes underlying mountain speciation, however, are largely untested. The prevalence of steep ecogeographic gradients and the geographic isolation of populations by topographic features are predicted to promote speciation in mountains. We evaluate these processes in a species‐rich Neotropical genus of understory herbs that range from the lowlands to montane forests and have higher species richness in topographically complex regions. We ask whether climatic niche divergence, geographic isolation, and pollination shifts differ between mountain‐influenced and lowland Amazonian sister pairs inferred from a 756‐gene phylogeny. Neotropical Costus ancestors diverged in Central America during a period of mountain formation in the last 3 million years with later colonization of Amazonia. Although climatic divergence, geographic isolation, and pollination shifts are prevalent in general, these factors do not differ between mountain‐influenced and Amazonian sister pairs. Despite higher climatic niche and species diversity in the mountains, speciation modes in Costus appear similar across regions. Thus, greater species richness in tropical mountains may reflect differences in colonization history, diversification rates, or the prevalence of rapidly evolving plant life forms, rather than differences in speciation mode.
5. Microevolutionary dynamics show tropical valleys are deeper for montane birds of the Atlantic Forest

   https://doi.org/10.1038/s41467-021-26537-9  

   Thom, G. ; Gehara, M. ; Smith, B.T. ; Miyaki, C.Y. ; do Amaral, F.R. ( November 2021 , Nature communications)

   Tropical mountains hold more biodiversity than their temperate counterparts, and this disparity is often associated with the latitudinal climatic gradient. However, distinguishing the impact of latitude versus the background effects of species history and traits is challenging due to the evolutionary distance between tropical and temperate assemblages. Here, we test whether microevolutionary processes are linked to environmental variation across a sharp latitudinal transition in 21 montane birds of the southern Atlantic Forest in Brazil. We find that effective dispersal within populations in the tropical mountains is lower and genomic differentiation is better predicted by the current environmental complexity of the region than within the subtropical populations. The concordant response of multiple co-occurring populations is consistent with spatial climatic variability as a major process driving population differentiation. Our results provide evidence for how a narrow latitudinal gradient can shape microevolutionary processes and contribute to broader scale biodiversity patterns.