Refugia within refugia: the case study of a canopy tree (Eurycorymbus cavaleriei) in subtropical China

Abstract

Aim Eurycorymbus cavaleriei (Lévl.) Rehd. et Hand.‐Mazz. (Sapindaceae) is a Tertiary relict tree endemic to subtropical China. This area is a centre for speciation and evolution within the East Asia biome and one of its most important refugial locations. In this study we aim to elucidate the phylogeographical patterning in E. cavaleriei, in order to identify the locations of the species’ main refugia and the predominant patterns of migration that have led to the contemporary spatial genetic structure of chloroplast variation. Location Subtropical China. Methods We sampled 18 populations of E. cavaleriei throughout its geographical range. Chloroplast DNA (cpDNA) sequence data from two non‐coding regions ((trnS/trnG and pl20/5′‐rps12) were obtained from 170 individuals for phylogeographical analyses. Relationships among cpDNA haplotypes were determined using median‐joining networks. Genetic structure was examined by spatial analysis of molecular variance (SAMOVA). Population differentiation was estimated by GST and NST statistics. Results Ten distinct haplotypes were identified. The level of differentiation among populations was relatively high (GST = 0.817), and NST was significantly higher than GST (P < 0.05), indicating that strong phylogeographical structure is exhibited by this species. The SAMOVA revealed five diverging groups of related haplotypes, which coincide with major landscape features in this region. Main conclusions The high differentiation among populations of E. cavaleriei may be a combined effect of historical and contemporary processes, such as the low effective population size for the chloroplast genome of a dioecious species, long‐term range fragmentation and limited seed dispersal for the species. Clear‐cut geographical distributions of ancestral haplotypes of the species suggest multiple potential refugia across subtropical China. The identified refugial regions have long been recognized as centres of plant diversity and endemism for China and have also been suggested as glacial refugia for many other plant species. The combination of these factors means that these locations should be considered as the highest priority for inclusion in conservation policies and sustainable forest management strategies for subtropical China.

Quaternary phylogeography: the roots of hybrid zones

“…These include a variety of organisms, such as frogs, turtles, bats and trees (eg. Gong et al 2009;Wang et al 2009;Wei et al 2010;Zhang et al 2010). These studies show ancient and more recent divergences, indicate the location of refugia and give signals of demographic changes consequent on ice ages.…”

Phylogeography of the seaweed Ishige okamurae (Phaeophyceae): evidence for glacial refugia in the northwest Pacific region

“…The presence of 14 missing haplotypes between C17 and phylogroup I further suggests long-term isolation from other phylogroups. Northern Taiwan was linked to the Asian continent via a land bridge during the glacial expansion 100 kya-20 kya and provided a refuge for many terrestrial organisms (Wang et al 2009). The presence of four diVerent haplotypes and haplotype C17 with many missing haplotypes to phylogroup I suggests that northern Taiwan populations were remnants of a marine glacial refugia, which has not expanded as the ice receded.…”

Chloroplast DNA phylogeographic analysis reveals significant spatial genetic structure of the relictual tree Davidia involucrata (Davidiaceae)

“…On this basis, these populations may represent potential local refugia (Avise 2000). This region has been presumed to be a long-term refuge for plant species in general because of its high diversity and endemism (Ying et al 1993;Wu and Wu 1996;Ying 2001;Wang et al 2009). Many ancient plant species, such as Cathaya argyrophylla, Emmenopterys henryi, C. japonicum, Tetracentron sinense, Ginkgo biloba, Thuja sutchuenensis and Metasequoia glyptostroboides, are found in this region (Ying et al 1993;Wang and Ge 2006;Gong et al 2008).…”