Is Phylogeographic Congruence Predicted by Historical Habitat Stability, or Ecological Co-associations?

Abstract

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 remain 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.

Genetic signatures of lineage fusion closely resemble population decline

“…Additional criteria for lineage fusion candidacy might include the absence of spatial genetic structure or phylogeographic structure within a given species, despite its broad geographic distribution across an area known to have harbored multiple Pleistocene refugia, coupled with the presence of strong spatial genetic structure or phylogeographic structure of co‐distributed members of the same ecological community (Garrick et al., 2019 ). Other circumstances conducive to lineage fusion would include paleoclimatic ecological niche models and/or spatial projections of climatic stability surfaces (e.g., Garrick et al., 2021 ; Hyseni & Garrick, 2019 ) that clearly indicate historical disjunction of present‐day unstructured populations. Indeed, these and other criteria for lineage fusion candidacy could be used to formulate expectations prior to re‐analysis of publicly available genetic datasets from ecologically and taxonomically diverse taxa, to investigate the prevalence of lineage fusion in nature.…”

Genome-wide markers show continental structuring and mitonuclear discordance in the forest tent caterpillar (Malacosoma disstria Hübner) (Lepidoptera: Lasiocampidae)

“…Similar population structures among different forest species reflect the common demographic responses to historic bioclimatic change and ecological co-associations (Garrick et al. 2021). For example, midcontinent biogeographic breaks, similar to what we observed in M. disstria , have been detected in other forest animals, including Choristoneura fumiferana (Lepidoptera: Tortricidae) (Lumley et al.…”

“…Combinations of drift and adaptation in these regions have led to intra-and interspecific diversification in many forest species. Similar population structures among different forest species reflect the common demographic responses to historic bioclimatic change and ecological co-associations (Garrick et al 2021). For example, midcontinent biogeographic breaks, similar to what we observed in M. disstria, have been detected in other forest animals, including Choristoneura fumiferana (Lepidoptera: Tortricidae) (Lumley et al 2020), Lynx canadensis (Carnivora: Felidae) (Stenseth et al 1999;Rueness et al 2003), Ursus americanus (Carnivora: Ursidae) (Puckett et al 2015; but see Bradburd et al 2018), Campanula americana (Campanulaceae) (Prior et al 2020), and Eptesicus fuscus (Chiroptera: Vespertilionidae) (Yi and Latch 2022).…”

Whole genome demographic models indicate divergent effective population size histories shape contemporary genetic diversity gradients in a montane bumble bee

“…However, genetic variation is also influenced by the legacy of historical events that have driven fluctuations in effective population size ( N e ). The impact of Quaternary climate variation on genetic diversity is well‐recognized (Hewitt, 2000 ), and recent studies have more explicitly examined links between species range stability and genetic diversity (Carnaval et al, 2009 ; Garrick et al, 2021 ; Koch et al, 2018 ). Revealing how landscape changes drive declines and recovery in N e has thus become important for reconstructing evolutionary histories, but also for interpreting contemporary genetic diversity and making predictions about vulnerability to environmental change.…”