An odd disjunction

Delphinium exaltatum

Range disjunctions are common in the natural world and, in eastern North America, are thought to arise from barriers formed by the Mississippi River embayment, vicariance due to glacial flooding during the Pleistocene, colonization from separate glacial refugia, or long-distance dispersal in recent times. Led by Rebekah Mohn and Christy Edwards, our new paper in American Journal of Botany tests these hypotheses using a genetic and phylogeographic analysis of Delphinium exaltatum, a threatened larkspur–and finds that none of these hypotheses match!

Rather, the species likely harbored in a single, large refugium during the last glaciation, then slowly moved north as conditions warmed. Sometime between 12,000-18,000 years ago, as the species reached the southern Appalachians, a group splintered off to move higher elevations, thus separating themselves from the other “lowland” populations. Interesting, the major range disjunction between the eastern populations and the Ozarkian populations is associated with much less genetic divergence than this lowland/highland split!

The phylogeographic history of a range disjunction in eastern North America: the role of post-glacial expansion into newly suitable habitat [article]
Mohn, R.A., Oleas, N.H., Smith, A.B.,Swift, J.F., Yatskievych, G., and Edwards, C. 2021. American Journal of Botany 108:1042-1057.

Highlighted as a noteworthy article of the issue