Geographical or ecological divergence between the parapatric species Ephedra sinica and E. intermedia?

Abstract

Understanding the factors that contribute to population genetic structures and ecological niche divergence is crucial for elucidating the biogeographical history and speciation of plants. To disentangle the present phylogeographical patterns and evolutionary history of two closely related parapatric species from Ephedra (Ephedra sinica and E. intermedia), we systematically profiled their population genetic structures, niche divergence and potential speciation processes based on sequence variation of four chloroplast DNA fragments and climate-based ecological niche modelling (ENM). Phylogenetic analyses suggested that E. sinica formed a monophyly which was nested in E. intermedia. The latter species formed two paraphyletic subclades, corresponding to Western and Eastern lineages. Furthermore, the phylogeographical analysis results indicated very significant inter-and intraspecies genetic differentiation, and BEAST inference suggested that E. sinica diverged from E. intermedia at 3.20 million years ago (Ma; 95 % HPD: 2.05-8.10 Ma), while the Western lineage of E. intermedia diverged much earlier at 6.10 Ma (95 % HPD: 4.10-11.82 Ma). In addition, niche identity tests performed using MaxEnt strongly supported the hypothesis that the two sister species had significantly diverged on their ecological niches. Isolation by geographical and environment distance (IBD and IBE) tests suggested that the overall divergence of the populations from the two species were more influenced by environmental factors. Our data provide new insight into the ecological speciation of Ephedra and also provides molecular evidence for the identification and genetic conservation of these important pharmaceutical plants.

The East Asian Winter Monsoon Acts as a Major Selective Factor in the Intraspecific Differentiation of Drought-Tolerant Nitraria tangutorum in Northwest China

“…Our analysis also revealed that both East-A and East-B lineages located in the eastern region exhibited intraspecific divergence [ Φ ST (East-A versus East-B) = 0.388, p < 0.01], and that the East-A lineage possessed the highest level of genetic diversity ( H T = 0.930, p < 0.05) relative to the other lineages. An analogous phylogeographical genetic structure has been found in other xerophytes, such as R. soongarica , Ephedra sinica , E. intermedia , A. squarrosum , and Panzerina lanata [ 6 , 23 , 28 , 45 , 46 ]. The genetic divergence induced by the Quaternary climate oscillations was the result of this climatic event fostering habitat fragmentation, geographic isolation, and an increase in dispersal distance, which has been well established in many plant species [ 3 , 28 , 29 , 47 ].…”

“…These findings were made based on the fact that the level of genetic diversity among populations was approximately two-fold greater than within populations ( H T = 0.922 vs. H S = 0.470, respectively) ( Table 2 ). The higher differentiation level among populations of N. tangutorum may be due to the intensifying aridification of northwest China induced by geological and paleoclimate scenarios, such as the uplift of the QTP, the fluctuation of glacial–interglacial cycles, as well as the onset and development of EAMS [ 11 , 23 , 46 ]. We hypothesize that the regional vast deserts encompassing the range of N. tangutorum species, such as the Bardain Jaran and Tengger Deserts, could potentially drive population divergence by impeding gene flow between N. tangutorum populations.…”

“…The isolation of ecological niches may also contribute to genetic divergence. For example, genetic differentiation of the closely-related species E. sinica and E. intermedia resulted from changes in their ecological niches [ 46 ]. Based on the ENM analysis conducted in the present study, the potentially suitable ranges for N. tangutorum were significantly affected by paleoclimate changes ( Figure 6 ).…”

Species Delimitation and Lineage Separation History of a Species Complex of Aspens in China

“…Hence the genetic divergence between these two species might reflect adaptation to these two environmentally divergent subkingdoms. Genetic divergence between sister species or sister lineages within species due to ecological differentiation have been observed in many plant species in China (Li et al, 2013 ; Wang et al, 2013 ; Sun et al, 2015 ; Yin et al, 2016 ), especially within the “Sino-Himalayan Forest” floristic subkingdom (Fan et al, 2013 ; Liu et al, 2013 ; Zhao et al, 2016 ) where environmental heterogeneity is relatively high.…”

A snapshot of progenitor-derivative speciation in action inIberodes(Boraginaceae)

“…adaptation of lineages to changes in the environment, Donoghue and Edwards 2014) have been argued to play a role in speciation and lineage diversification (Wiens and Graham, 2005; Cavender-Bares, 2019). Nevertheless, the contribution of ecological factors as primary drivers of speciation remains more elusive (Mayr, 1954; Pyron and Burbrink, 2010; Yin et al, 2016).…”