Genetic diversity within populations of an arctic–alpine species declines with decreasing latitude across the Northern Hemisphere

Abstract

Aim We identified and evaluated general latitudinal trends in genetic diversity within populations of a widespread arctic–alpine plant, Dryas octopetala, to examine the applicability to this species of the dominant hypothesis that intraspecific genetic diversity is highest in the tropics and declines towards the poles. Location The circumpolar Arctic and northern temperate alpine ranges, with a focus on high altitude mountains at the species lowest latitudinal margin in the Japanese archipelago. Methods Within‐population genetic diversity was assessed using genotypes determined at nine microsatellite loci (n = 489), chloroplast DNA sequences (atpB‐rbcL and trnV‐ndhC spacers, n = 181) and a nuclear gene sequence (LEAFY, n = 173) of 18 populations, as well as a previously published amplified fragment length polymorphism dataset for 26 populations, across the distributional range of the species. The latitudinal pattern of intra‐population genetic diversity was modelled at hemispheric scale to discriminate linear latitudinal and quadratic central–marginal trends in genetic diversity. Population genetic structure was assessed by Bayesian clustering analyses. Results At hemispheric scale, we identified two interacting effects: a general latitudinal decline in genetic diversity towards the equator and a central–marginal effect, whereby genetic diversity decreases towards the margins of a species’ range. This decrease was more marked in low‐latitude marginal populations than in high‐latitude marginal populations. Populations at the lowest latitudes in the Japanese archipelago showed the lowest level of genetic diversity but exhibited distinctive genetic variation. Main conclusion The latitudinal decline in genetic diversity within populations of this arctic–alpine plant across its range was opposite to the commonly observed trend. A significant part of the equator‐ward latitudinal decline in genetic diversity in this arctic–alpine species may be attributable to a “sky island” effect, which played a greater role at low latitudes.

Northern areas as refugia for temperate species under current climate warming: Atlantic salmon (Salmo salarL.) as a model in northern Europe

“…Moreover, the contrary is observed here, with a latitudinal cline of genetic variation in northern areas and lower values in southern areas. This pattern, which has been reported in some cold-adapted species (Hirao et al, 2017), as well as in other salmonids (Ninua et al, 2018) and other anadromous species (Hasselman et al, 2013), has also been expected in S. salar (Valiente et al, 2005), but it had been found only for major histocompatibility complex class II genes (Dionne et al, 2007); to our knowledge, our study is the first report of the pattern for microsatellite markers in this species. Thus, anadromous species appear to exhibit the opposite of the pattern that usually occurs in vertebrates (Adams & Hadly, 2013).…”

“…This pattern, which has been reported in some cold‐adapted species (Hirao et al . , ), as well as in other salmonids (Ninua et al ., ) and other anadromous species (Hasselman et al ., ), has also been expected in S. salar (Valiente et al . , ), but it had been found only for major histocompatibility complex class II genes (Dionne et al .…”

Ecotypic divergences of the alpine herbPotentilla matsumuraeadapted to fellfield–snowbed habitats across a series of mountain sky islands

“…The genetic boundary between P. matsumurae in Central Honshu and the northern regions corresponds to that found by phylogeographic studies of several alpine plant species belonging to various taxa in Japan (e.g., Fujii et al., ; Ikeda et al., , , ; Hirao et al., ). This genetically disjunct structure in multiple alpine plant species strongly suggests historical isolation of alpine plant communities between Central Honshu and the northern regions during past climate oscillations (reviewed by Fujii and Senni, ).…”

“…However, a broad‐scale approach with a historical (phylogeographic) perspective is required to infer the evolutionary history of ecotype differentiation. Phylogeographic studies on Japanese alpine flora have demonstrated the existence of distinct lineages in Central Honshu and northern populations across multiple alpine plant species (e.g., Fujii et al., ; Fujii and Senni, ; Ikeda et al., , ; Hirao et al., ), including P. matsumurae (Ikeda et al., , ). On the basis of these findings, it has been proposed that the mountains of Central Honshu serve as refugia during historical climatic oscillations and populations in this area have been historically isolated from the populations of the more northern regions (reviewed by Fujii and Senni, ).…”

Relict populations and Central European glacial refugia: The case of Rhododendron ferrugineum (Ericaceae)

“…The general large‐scale scenario based on the concept of southern refugia is especially altered when considering cold‐adapted (mountainous and arctic‐alpine) species (Birks & Willis, ; Eidesen et al., ; Hirao et al., ). The habitat availability and dynamics of populations in the mosaic of the European LGM periglacial areas depended substantially on species’ ecology.…”