Abstract
The eastern subterranean termite, Reticulitermes flavipes, currently inhabits previously glaciated regions of the northeastern U.S., as well as the unglaciated southern Appalachian Mountains and surrounding areas. We hypothesized that Pleistocene climatic fluctuations have influenced the distribution of R. flavipes, and thus the evolutionary history of the species. We estimated contemporary and historical geographic distributions of R. flavipes by constructing Species Distribution Models (SDM). We also inferred the evolutionary and demographic history of the species using mitochondrial (cytochrome oxidase I and II) and nuclear (endo‐beta‐1,4‐glucanase) DNA sequence data. To do this, genetic populations were delineated using Bayesian spatial‐genetic clustering, competing hypotheses about population divergence were assessed using approximate Bayesian computation (ABC), and changes in population size were estimated using Bayesian skyline plots. SDMs identified areas in the north with suitable habitat during the transition from the Last Interglacial to the Last Glacial Maximum, as well as an expanding distribution from the mid‐Holocene to the present. Genetic analyses identified three geographically cohesive populations, corresponding with northern, central, and southern portions of the study region. Based on ABC analyses, divergence between the Northern and Southern populations was the oldest, estimated to have occurred 64.80 thousand years ago (kya), which corresponds with the timing of available habitat in the north. The Central and Northern populations diverged in the mid‐Holocene, 8.63 kya, after which the Central population continued to expand. Accordingly, phylogeographic patterns of R. flavipes in the southern Appalachians appear to have been strongly influenced by glacial‐interglacial climate change.OPEN RESEARCH BADGES This article has been awarded Open Materials, Open Data Badges. All materials and data are publicly accessible via the Open Science Framework at https://doi.org/10.5061/dryad.5hr7f31.
Highlights
Geographic barriers to dispersal, such as mountains and rivers, are considered major drivers of genetic divergence within and among species
In Europe, when ice sheets reached their maximum extent during glacials, this repeatedly resulted in range contraction into southern refugia, which subsequently served as key reservoirs for recolonization via northward expansion during interglacials (Hewitt 1996, 2004)
We investigated the genetic consequences of glacial-interglacial climate change on R. flavipes from the unglaciated southern Appalachian Mountains and surrounding areas, and considered distributional shifts as a plausible hypothesis to be assessed using Species Distribution Models (SDM) and genetic data
Summary
Geographic barriers to dispersal, such as mountains and rivers, are considered major drivers of genetic divergence within and among species. In Europe, when ice sheets reached their maximum extent during glacials, this repeatedly resulted in range contraction into southern refugia, which subsequently served as key reservoirs for recolonization via northward expansion during interglacials (Hewitt 1996, 2004). In montane areas with deeply dissected topography, latitude alone may be a poor proxy for the locations of refugial areas, as the steep environmental gradients that occur locally can exert a strong influence on persistence of habitat patches that can support viable populations In such regions—in contrast to the traditional view of refuges being continuously occupied longterm stable areas—successive glacial-interglacial cycles are less likely to have repeatedly played out in the same way. Consideration of how major shifts in geographic distributions contributed to population differentiation during the Pleistocene is important for understanding speciation processes (e.g., Carstens and Knowles 2007 and references therein)
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