Evolutionary history influences the effects of water–energy dynamics on oak diversity in Asia

Abstract

Aim Water–energy dynamics are often correlated with geographical patterns of terrestrial plant richness. However, the relative importance of water and energy on species richness is still being debated. Some studies suggest a transition in the relative importance of water and energy along a latitudinal gradient, i.e. that water is the most important factor at low latitudes, whereas energy is the leading factor at high latitudes. The generality of this transition is yet to be established and is the focus of the current study. In particular, we examine whether differences in the evolutionary histories of two subgenera of Asian oaks influence the derived models of water–energy dynamics. Location Asia (70–140° E; 10–60° N). Methods We performed geographically weighted regressions to quantify geographical variation in the relative importance of water and energy on the species richness of Asian oaks (Quercus L.). We also evaluated how evolutionary history influences the relative importance of water and energy in determining species richness, by comparing patterns in the two oak subgenera: Quercus subg. Quercus and Quercus subg. Cyclobalanopsis. In particular, we assessed how the ancestral climatic niche of these two subgenera (i.e. subgenus Quercus of temperate origin versus subgenus Cyclobalanopsis of tropical origin) relates to the relative importance of water and energy on contemporary diversity patterns. Results We found no geographical transition line in the relative importance of water and energy along the latitudinal gradient studied. Instead, we found that the importance of energy relative to water on the species richness of subgenus Quercus increased from mid‐latitudes (warm temperate regions) towards both tropical and boreal regions: this pattern might reflect that this subgenus originated in the temperate region. In contrast, the importance of both water and energy on the species richness of the tropical subgenus Cyclobalanopsis increased from tropical to boreal regions, probably due to a lack of adaptation to winter coldness. Main conclusions Our results suggest that differences in the evolutionary history – specifically the ancestral climatic niche – of the two subgenera of oaks influence the effects of water–energy dynamics on species richness along a latitudinal gradient through niche conservatism.

Allopatric divergence, local adaptation, and multiple Quaternary refugia in a long-lived tree (Quercus spinosa) from subtropical China

“…Our analyses evidenced the significant roles of geography and climate in shaping Q. spinosa genetic structure (Table 2). Similar to that revealed in previous studies highlighting the importance of water availability and temperature on oak species demography (Sardans & Penuelas, 2005; Yang et al, 2009; Xu et al, 2013), the present study showed the effect of precipitation (PC1) on Q. spinosa genetic divergence but failed to uncover the effect of temperature (PC2). However, at the lineage level, both temperature (BIO 4) and precipitation (BIO 18) influenced the divergence of CEC lineage (Table 2).…”

A consistent species richness–climate relationship for oaks across the Northern Hemisphere

“…The explanatory power of winter temperature on species with tropical affinity is higher than for those with temperate affinity (Wang et al, ). Previous studies on Quercus have also found that the effect of environmental energy on the species richness of different groups depends on their ancestral niches; environmental energy limits species richness of tropical lineages at high latitudes but of temperate groups at both low and high latitudes (Xu et al, ). Here, we found stronger phylogenetic conservatism in the climatic niches represented by energy, water and seasonality variables for the temperate groups Quercus and Lobatae and the entire genus than for tropical group Cyclobalanopsis .…”

“…To determine whether the species richness–climate relationship is mediated by climatic niche conservatism, as suggested by Xu et al (), we reconstructed ancestral climatic niches and estimated the phylogenetic niche conservatism for each species group present on the same continent. A consensus supertree of Quercus was built by merging two recently published Quercus phylogenies (Deng et al, ; Hipp et al, ) based on RAD sequences.…”

“…Many Quercus species are important components of forest ecosystems in temperate regions in the Northern Hemisphere (Nixon, 1997;Wu et al, 1999). Previous studies on the species richness patterns of Quercus indicate that the species richness-climate relationship of this group is rooted in its evolutionary history due to niche conservatism (Xu, Wang, Rahbek, Lessard, & Fang, 2013) and that a water-energy interaction significantly influences Quercus species richness (Xu, Wang, Rahbek, Sanders, & Fang, 2016).…”

Effects of contemporary environment and Quaternary climate change on drylands plant diversity differ between growth forms

“…Global herbaceous floras show an accelerated speciation within a relatively recent history due to their shorter generation time than woody species (Linder 2008, Smith and Donoghue 2008, Hughes and Atchison 2015. Most previous studies on plant richness patterns are focused on woody species (Svenning and Skov 2007, Wang et al 2012b, Xu et al 2013. Many studies focusing on herb-dominated vegetation types (e.g.…”