Importance of demographic history for phylogeographic inference on the arctic–alpine plant Phyllodoce caerulea in East Asia

et al. 2017

Molecular Ecology

The circumarctic ranges of arctic-alpine plants are thought to have been established in the late Pliocene/early Pleistocene, when the modern arctic tundra was formed in response to climate cooling. Previous findings of range-wide genetic structure in arctic-alpine plants have been thought to support this hypothesis, but few studies have explicitly addressed the temporal framework of the genetic structure. Here, we estimated the demographic history of the genetic structure in the circumarctic Kalmia procumbens using sequences of multiple nuclear loci and examined whether its genetic structure reflects prolonged isolation throughout the Pleistocene. Both Bayesian clustering and phylogenetic analyses revealed genetic distinction between alpine and arctic regions, whereas detailed groupings were somewhat discordant between the analyses. By assuming a population grouping based on the phylogenetic analyses, which likely reflects a deeper intraspecific divergence, we conducted model-based analyses and demonstrated that the intraspecific genetic divergence in K. procumbens likely originated during the last glacial period. Thus, there is no need to postulate range separation throughout the Pleistocene to explain the current genetic structure in this species. This study demonstrates that range-wide genetic structure in arctic-alpine plants does not necessarily result from the late Pliocene/early Pleistocene origin of their circumarctic ranges and emphasizes the importance of a temporal framework of the current genetic structure for understanding the biogeographic history of the arctic flora.

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Ikeda

Eidesen²,

et al. 2017

Molecular Ecology

“…caerulea that showed statistical evidence for introgression from P . aleutica (Ikeda, Sakaguchi, Yakubov, Barkalov, & Setoguchi, ) were excluded from the analysis. Analysed individuals are indicated in Table S1.1 in Appendix S1.…”

Section: Methodsmentioning

confidence: 99%

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

Ikeda

Journal of Biogeography

Barkalov

et al. 2018

Aim: The ice-free area around the Bering Land Bridge, Beringia, has been noted as an important refugium of organisms preferring cold environments such as arctic-alpine plants throughout the Pleistocene climate oscillations. Although numerous phylogeographical studies have supported this refugium, recent studies have challenged the idea of a homogeneous refugium in Beringia. We aim to examine a novel scenario of the post-glacial colonization history of an alpine plant Phyllodoce aleutica in Beringia.Location: The Japanese Archipelago, the Kamchatka Peninsula, the Aleutian Islands, Alaska.Method: The range-wide genetic structure of P. aleutica was elucidated by sequencing 13 nuclear loci. The phylogeographical history was inferred using model-based approaches based on coalescent simulations together with the potential distributions predicted by ecological niche modelling.Results: Bayesian clustering and phylogenetic networks revealed that P. aleutica was divided into three geographically structured groups: the main island of the Japanese Archipelago, the northern island of the archipelago (Hokkaido) and Beringia, including eastern Hokkaido. The demographic history underlying the genetic structure and the potential distributions at present and during Last Glacial Maximum suggest that their divergence likely predated the last glacial period. Except for genetic admixture with the sister species Phyllodoce glanduliflora, populations in Alaska exhibited lower genetic diversity than those in East Asia and exclusively shared two widespread genotypes. Approximate Bayesian computation showed that a demographic model postulating post-glacial expansion into Alaska fit better than alternative models. Main conclusions:Our study suggests that P. aleutica in eastern Beringia originated through post-glacial colonization from East Asia, providing novel insight into the biogeographical history of alpine flora in Beringia. K E Y W O R D S alpine plants, approximate Bayesian computation, Beringia, East Asia, ecological niche modelling, phylogeography

“…Nevertheless, without phylogeographical investigation in intermediate populations such as the Kuril Islands, we cannot fully support this scenario. As with previous inferences in the other alpine shrubs Cassiope lycopodioides (Ikeda et al ., ) and Phyllodoce caerulea (Ikeda et al ., ), the connected range between northern Japan and Beringia is a plausible alternative scenario for T. camtschaticum during the last glacial period. In this case, a scenario of range fragmentation following post‐glacial climate warming plausibly resulted in the genetic divergence between Beringia and Japan; however, genetic drift concurring the scenario would not explain the geographically structured pattern of genetic divergence.…”

Section: Discussionmentioning

confidence: 96%

“…These studies indicate that the disjunct ranges of alpine plants are considered to have been connected widely in East Asia during the last glacial period. This biogeographical history is further supported by another alpine shrub Phyllodoce caerulea (Ikeda et al ., ). Accordingly, phylogeographical investigations including Kamchatka and northern Japan could provide insight into the biogeographical history of flora in the Aleutian Islands.…”

Section: Introductionmentioning

confidence: 97%

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

Hata

Higashi

Journal of Biogeography

et al. 2016

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.