Phylogeographical insight into the Aleutian flora inferred from the historical range shifts of the alpine shrub Therorhodion camtschaticum (Pall.) Small (Ericaceae)

Abstract

Aim The Aleutian Islands, one of the southern margins of Beringia, were covered with ice caps during the Last Glacial Maximum (LGM). Although insular refugia for animal species have been hypothesized in this region, phylogeographical studies have never explored the biogeographical history of plant species. We aim to assess the population history of the flora of the Aleutian Islands and its biogeographical relevance to East Asia.Location The Aleutian Islands, Kamchatka, the Japanese Archipelago.Methods We sequenced seven nuclear loci from the alpine shrub Therorhodion camtschaticum (Pall.) Small (Ericaceae) and elucidated the geographical distribution of genetic variation. The divergence history among populations from the Aleutian Islands, Kamchatka and northern Japan was inferred by analyses based on coalescent simulations.Results Populations were genetically distinct between northern Japan and Beringia. In spite of the genetic differentiation, the divergence between Beringia and northern Japan occurred during or after the last glacial period [maximum-likelihood estimates (MLEs) = 10.6-15.5 ka with 95% highest posterior densities (HPDs): 1.7-43.5 ka]. The latter region has a larger population size than the former region. In contrast, widespread genetic similarity was revealed among the geographically separated populations in the Aleutian Islands and southern Kamchatka. Among these populations, a model assuming population decline fits better than a model that assumes either constant population size or population growth. Main conclusionsOur study suggests that insular refugia were unlikely for T. camtschaticum in the Aleutian Islands. Instead, T. camtschaticum may have had a wider range during LGM, encompassing both the Aleutian Islands and southern Kamchatka, or have colonized the Aleutian Islands from a LGM refugium that was the source of colonization into southern Kamchatka as well or encompassed the latter region. Our study provides novel insight into the biogeographical history of terrestrial biota in the Aleutian Islands.

Late Pleistocene origin of the entire circumarctic range of the arctic‐alpine plant Kalmia procumbens

“…The blue cluster occurs in Beringia and in northern Japan (Figure ), which largely corresponds to the widespread AFLP cluster dominating in Beringia (no Japanese samples were included in the AFLP study of Eidesen et al., ). Recent phylogeographic studies have revealed genetic similarity as well as demographic closeness between northern Japan and Beringia in alpine as well as arctic‐alpine plants (Hata et al., ; Ikeda, Higashi et al., , Ikeda et al., ), suggesting that cold‐adapted species may have spread widely in northern East Asia. Thus, the present distribution of the blue cluster probably reflects an extensive distribution of K .…”

East Asian origin of the widespread alpine snow‐bed herb, Primula cuneifolia (Primulaceae), in the northern Pacific region

“…Because there is no specific substitution rate in P . cuneifolia , we assumed 5.3–7.8 × 10 –9 substitutions per site per year to scale the divergence time following our previous studies (Hata et al., 2017; Ikeda et al., 2017, 2018) based on spontaneous mutation rates in Arabidopsis thaliana mutation accumulation lines (Ossowski et al., 2010).…”

“…Although a recent study inferred that the arctic–alpine plant Kalmia procumbens colonized central Japan from Beringia during the last glacial period (Ikeda et al., 2017), other studies have not addressed whether Japanese lineages of alpine plants were derived from lineages occurring in Beringia or vice versa. Recent phylogeographic studies have revealed that populations of several alpine plants exhibited high genetic similarity and low genetic diversity across extensive ranges in the northern Pacific region including northern Japan (Hata et al., 2017; Ikeda et al., 2014, 2017; Ikeda, Yakubov, Barkalov, & Setoguchi, 2018). These patterns can be explained by recent range expansion across the northern Pacific region from the Kamchatka Peninsula, which is a part of Beringia.…”

Post‐glacial East Asian origin of the alpine shrub Phyllodoce aleutica (Ericaceae) in Beringia

“…camtschaticum supports this inference in C . lycopodioides (Hata et al., ). Although sequence variation of seven nuclear loci revealed genetic differentiation between T .…”