The phylogeography of Fagus hayatae (Fagaceae): genetic isolation among populations

Abstract

The beech species Fagus hayatae is an important relict tree species in subtropical China, whose biogeographical patterns may reflect floral responses to climate change in this region during the Quaternary. Previous studies have revealed phylogeography for three of the four Fagus species in China, but study on F. hayatae, the most sparsely distributed of these species, is still lacking. Here, molecular methods based on eight simple sequence repeat (SSR) loci of nuclear DNA (nDNA) and three chloroplast DNA (cpDNA) sequences were applied for analyses of genetic diversity and structure in 375 samples from 14 F. hayatae populations across its whole range. Both nDNA and cpDNA indicated a high level of genetic diversity in this species. Significant fixation indexes and departures from the Hardy–Weinberg equilibrium, with a genetic differentiation parameter of R st of 0.233, were detected in nDNA SSR loci among populations, especially those on Taiwan Island, indicating strong geographic partitioning. The populations were classified into two clusters, without a prominent signal of isolation‐by‐distance. For the 15 haplotypes detected in the cpDNA sequence fragments, there was a high genetic differentiation parameter (G st = 0.712) among populations. A high G st of 0.829 was also detected outside but not within the Sichuan Basin. Consistent with other Fagus species in China, no recent population expansion was detected from tests of neutrality and mismatch distribution analysis. Overall, genetic isolation with limited gene flow was prominent for this species and significant phylogeographic structures existed across its range except for those inside the Sichuan Basin. Our study suggested long‐term geographic isolation in F. hayatae with limited population admixture and the existence of multiple refugia in the mountainous regions of the Sichuan Basin and southeast China during the Quaternary. These results may provide useful information critical for the conservation of F. hayatae and other Chinese beech species.

Potential effects of climate change on geographic distribution of the Tertiary relict tree species Davidia involucrata in China

“…It can be concluded that past refugia of D. involucrata were restricted to the same locations as contemporary populations (that is, in situ survival, as usually reported for plant species in subtropical China58, especially the mountains in the Sichuan Basin and its adjacent areas59). This would probably be true again in the future, although sizes might well be smaller.…”

Multiple refugia from penultimate glaciations in East Asia demonstrated by phylogeography and ecological modelling of an insect pest

“…Although Sichuan Basin has a higher latitude than Yunnan, the basin has a lower altitude resulting in warm temperatures during the glacial period compared to other areas at a similar latitude. This region has also been identified as a refugium of several species [ 29 , 32 , 50 – 53 ]. These studies either identified local-scale refugia in endemic species within one of these regions [ 50 , 51 ], or multiple refugia widely distributed in eastern Asia as well as the adjacent regions of eastern QTP [ 28 , 29 , 32 , 52 ].…”

“…Multiple microrefugia were identified in QTP and its adjacent areas for many endemic species [ 22 , 25 , 26 ]. Other studies focused on regional areas, such as northeastern China [ 21 , 27 , 28 ] and southern China [ 20 , 29 ] and refugia were identified within these areas. There is a lack of study on wider range-scale identification of Quaternary climate on species evolutionary history in East Asia [ 30 – 32 ], which might be caused by the limited distribution of the species used in previous studies.…”

“…The repeated influence by Quaternary climate oscillations made the postglacial history of species complicated in east Asia. Range expansion and inter−/postglacial recolonization were reported in species of east Asia [ 36 – 38 ], however, limited population admixture with multiple refugia existed in some other species [ 29 ]. Thus, species in eastern Asia might be survived in single or multiple refugia and impacted by different glacial periods of the Quaternary, although the evidence remains relatively limited.…”

A Transcriptomic Variation Map Provides Insights into The Genetic Basis of Pinus massoniana Evolution and Association of Oleoresin Yield

“…Sichuan Basin was one of glacial refugees for many species at the last Pleistocene glaciations [28,29], which may rescue the masson pine from extinction event. The masson pine gradually migrated to Guizhou plateau after end of glacial epoch and gradually adapted the plateau habitat.…”