Blow to the Northeast? Intraspecific differentiation of Populus davidiana suggests a north‐eastward skew of a phylogeographic break in East Asia

Abstract

AimThere is increasing interest in the role that biological traits, and historical and biogeographic processes, play in the formation of phylogeographic patterns. An arid belt that once existed in northern China might have affected many plants, but this has yet to be tested in an arid‐tolerant, wind‐dispersed species. Here, we tested how intrinsic and extrinsic factors have affected the phylogeography of Populus davidiana.LocationEast Asia.MethodsGenetic variation was surveyed across 40 populations (555 individuals) covering the Chinese range of P. davidiana, using 16 nuclear microsatellite loci (nSSRs) and four chloroplast fragments (cpDNA). Demographic and migration hypotheses were tested using coalescent‐based approaches, and the present and past potential distributions were predicted using species distribution modelling.ResultsMolecular data divide P. davidiana into two lineages, north‐eastern China (NECR) and central and northern China (CNCR); however, the dividing line is around 118ºE for nSSRs, but 122ºE for cpDNA. The range and habitat of the two lineages barely overlap at present, and their ecological separation may have initiated around the Pliocene‐Quaternary boundary, when major intraspecific cpDNA clades diverged. NECR and CNCR experienced post‐glacial north‐eastward and northward range shifts respectively. Bi‐directional historical gene flow was detected between NECR and CNCR for both bi‐parentally inherited nSSRs and maternally inherited cpDNA. Demographic inferences suggest a severe bottleneck for CNCR and especially NECR, around the latest Pleistocene.Main conclusionsThe phylogeographic break within P. davidiana reflects the impacts of biogeographic history, climate and biological traits. Its plumed, wind‐dispersed seeds might be especially significant because prevailing south‐western spring winds may have moved the NECR‐CNCR boundary further east than similar phylogenetic breaks in other species, and also moved the cpDNA boundary relative to that for nuclear markers. Biological traits, therefore, should also be considered when examining the genetic and ecological differentiation between closely related taxa.

Different rates of pollen and seed gene flow cause branch‐length and geographic cytonuclear discordance within Asian butternuts

“…Similar phylogeographic breaks in northern China have been also demonstrated for several other species, including Acer mono , Populus davidiana and Lindera obtusifolia (Guo et al ., 2014; Liu et al ., 2014; Zong et al ., 2015; Bai et al ., 2016; Ye et al ., 2017; Song et al ., 2020). The breaks are generally attributed to the climatic barrier of the arid belt since the late Miocene (Milne & Abbott, 2002), and the Pleistocene glaciation appeared to intensify the isolation between two sides of the belt where populations persisted in multiple refugia (Chen et al ., 2008; Tian et al ., 2009; Bai et al ., 2010; Guo et al ., 2014; Ye et al ., 2017; Song et al ., 2020). During the interglacial periods, hybrid zones were formed through range expansion as well as pollen/seed mediated gene flow.…”

“…During the interglacial periods, hybrid zones were formed through range expansion as well as pollen/seed mediated gene flow. These species varied in locations and ranges of hybrid zones, possibly because the species had different degrees of gene flow and different levels of tolerance to aridity (Song et al ., 2020).…”

“…Upon secondary contact, the two lineages could exchange genetic material and formed a broad hybrid zones through substantial pollen gene flow, but the chloroplast genomes swapped little and formed a dividing line because of limited seed dispersal. Geographic cytonuclear discordance has also been found in Acer mono (Guo et al ., 2014) and Populus davidiana (Song et al ., 2020). For Acer mono , chloroplast DNA rather than nuclear DNA gave rise to a wider contact zone, this is likely to be as a result of extensive dispersal by winged seeds and limited pollen dispersal by insect pollination (Guo et al ., 2014).…”

“…Ó 2021 The Authors New Phytologist Ó 2021 New Phytologist Foundation New Phytologist (2021) www.newphytologist.com New Phytologist mediated gene flow. These species varied in locations and ranges of hybrid zones, possibly because the species had different degrees of gene flow and different levels of tolerance to aridity (Song et al, 2020).…”

Insights Into the Significance of the Chinense Loess Plateau for Preserving Biodiversity From the Phylogeography of Speranskia tuberculata (Euphorbiaceae)

“…First, Meng et al (2015) have suggested the CLP to be an important refugium for the dry-adapted flora of northwestern China. Furthermore, disjoint distribution of same haplotype between CLP and northeastern China may result from long distance dispersal from the CLP ( Tian et al, 2009 ; Song et al, 2020 ). Finally, haplotypes of S. tuberculata in the Sichuan Basin (H13–14) are derived from the ancestral haplotype (H1), indicating the CLP may be the source of genotypes in southwestern China.…”