Direct long‐distance dispersal shapes a New World amphitropical disjunction in the dispersal‐limited dung moss Tetraplodon (Bryopsida: Splachnaceae)

Abstract

AbstractAimMany intercontinental disjunctions, especially among spore‐producing plants, are shaped by long‐distance dispersal (LDD) via wind currents. Amphitropical disjunctions are most commonly explained through LDD, but other vectors and dispersal scenarios must also be considered. To interpret the New World amphitropical disjunction in the dung‐moss genus Tetraplodon, we compared stepwise migration along the Andes, direct LDD and ancient vicariance.LocationGlobal, specifically high‐latitude and high‐elevation localities, with a focus on the New World.MethodsPhylogenetic relationships were inferred from four loci sampled from 124 populations representing the global range of Tetraplodon, and analysed using maximum‐likelihood and Bayesian optimality criteria, with divergence dates estimated in beast.ResultsThe monophyletic T. mnioides complex diversified between the early Miocene and early‐to‐mid Pliocene into three well‐supported clades, each with a unique geographical distribution: Laurasian, primarily high‐elevation tropical, and amphitropical. Populations from southernmost South American were reconstructed as a monophyletic lineage that diverged from high‐latitude Northern Hemisphere populations around 8.63 Ma [95% highest posterior density (HPD) 3.07–10.11 Ma].Main conclusionsDirect LDD has resulted in the American amphitropical disjunction in Tetraplodon. A lack of modern or historical wind connectivity between polar regions and the poor resistance of Tetraplodon spores to the conditions associated with wind‐dispersal suggest that bird‐mediated LDD provides the best explanation for the establishment of amphitropicality.