Taxonomy & Evolution

Variation between alpine and coastal populations of Vaccinium vitis-idaea

Can changes in ploidy level explain why certain Arctic and alpine species are able to survive at lower latitudes and elevations?

Plant species originating from Arctic regions also commonly grow in alpine habitats further south. However, some species also exist in specific low-elevation habitats. Local populations at lower elevations may have different origins, ploidy levels, mating systems and/or morphological traits from alpine populations, but comparative studies between alpine and low-elevation populations are scarce.

In their new study published in AoBP, Wakui & Kudo investigate the ecological and genetic differentiations between alpine and low-elevation populations of Vaccinium vitis-idaea in northern Japan. V. vitis-idaea is an evergreen dwarf shrub broadly distributed in boreal forests and bogs across the northern hemisphere. In Hokkaido, it grows mainly in alpine zone but also exists at lower elevations in unique environments, such as algific talus slopes and coastal grasslands.

Flowering inflorescence of tetraploid Vaccinium vitis-idaea in one of the low-elevation populations in Hokkaido, Japan. Image credit: A. Wakui.

In their study, Wakui & Kudo surveyed and sampled 22 V. vitis-idaea populations across Hokkaido (including alpine, open-montane, montane-forest and coastal habitat types) to investigate ploidy level, genetic structure, mating system and ecological characteristics of the populations. They found that most of the alpine and Arctic populations were diploids. Unexpectedly, most of the low-elevation populations were tetraploids, the first record of tetraploidy in this species. The tetraploid populations showed unique genetic composition, higher self-compatibility, and larger morphological traits compared to diploids.

The authors concluded that alpine and low-elevation populations are composed of different ecotypes suited to persistence in each specific environment. Most populations at lower elevations contained unique ecotypes suited to persistence in isolated situations. Local, low-elevation populations of typical alpine species maintain ecologically and genetically specific characteristics and could be valuable in terms of evolutionary and conservation biology. This study demonstrates the biological importance of small and isolated populations at the edges of a species’ distribution.