Biogeography and ecological niche evolution in Diapensiaceae inferred from phylogenetic analysis

Abstract

Diapensiaceae (Ericales) are a small family of about 15 species. Within this clade, two species are broadly distributed throughout the Northern Hemisphere, whereas the remaining species have a disjunct distribution between eastern North America and eastern Asia. To address patterns and processes of diversification in Diapensiaceae, we conducted biogeographic analyses and inferred shifts in the ecological niche across the phylogeny of the clade. Although Diapensiaceae have been the focus of multiple phylogenetic and biogeographic studies, previous studies have been taxonomically limited. This study has greatly improved the phylogenetic underpinning for Diapensiaceae with the most inclusive taxonomic sampling thus far, employing both nuclear and plastid gene sequence data for at least one sample per species in the family. Our estimates indicate that genera of Diapensiaceae variously diverged in the Eocene, Oligocene, and early to mid‐Miocene. The biogeographic analysis suggests that the probable ancestor of the Diapensiaceae crown clade originated in the Nearctic, with vicariance events contributing to the current distribution of the disjunct taxa. Ecological niche, when considered in a phylogenetic context, was observed to be clustered on the basis of biogeographic realm. In general, a greater ecological overlap was found at younger nodes and a greater niche divergence was found among distantly related species. Diversification in Diapensiaceae appears to have been shaped by both large‐scale biogeographic factors, such as vicariance, and divergence in an ecological niche among closely related species.

Taxonomy and biogeography ofDiapensia(Diapensiaceae) based on chloroplast genome data

“…2, S2). The result is congruent with findings from the previous studies that recognized two tribes in the family: Galaceae (monogeneric) and Diapensieae (Airy Shaw, 1964;Xi & Tang, 1990;Rönblom & Anderberg, 2002;Higashi et al, 2015;Gaynor et al, 2020). Morphologically, the anthers of the ENA endemic genera (Galax and Pyxidanthera) all have short appendages (Rönblom & Anderberg, 2002).…”

“…S1, node 1), and a normal distribution with a mean (± SD) of 62.0 ± 1.3 Ma (Fig. S1, node 2) to constrain the crown group of Diapensiaceae according to previous studies (Hou et al, 2016;Rose et al, 2018;Gaynor et al, 2020).…”

“…The distributional pattern of Diapensiaceae has attracted the phylogeographic interest of many botanists (Li, 1952;Hosokawa, 1958;Thorne, 1972;Boufford, 1992;Wen, 1999;Ye et al, 2012;Higashi et al, 2015;Gaynor et al, 2020). Three of the genera are endemic to a specific geographic region: Galax and Pyxidanthera are endemic to eastern North America (Figs.…”

Phylogenomics, biogeography, and evolution of the blue‐ or white‐fruited dogwoods (Cornus)—Insights into morphological and ecological niche divergence following intercontinental geographic isolation

“…We used the cor function to compute the Pearson's correlation coefficient among variables in R. Variables were then filtered out, so that only one variable represented the correlated pair(s) (r ≥ 0.8) to use in comparative analysis of EA-NA trends across all three disjuncts (Table S4.2-3) following previous studies (Zhao et al, 2018;Gaynor et al, 2020;Kenar & Kikvidze, 2020). This filtering resulted in the following four variables for analysis: annual mean temperature (BIO1), annual temperature range (BIO 7), annual mean precipitation (BIO12), and elevation (Table S3).…”

“…Estimating rates of morphological and molecular changes on branches of the phylogenetic tree will provide strong evidence for testing the hypothesis and shed light on how the rate of morphological evolution correlated with the rate of molecular evolution in the sister clades isolated in different geographic regions. Furthermore, comparison of abiotic environmental conditions between the disjunct counterparts can illuminate potential ecological drivers underlying the morphological changes (e.g., Du et al, 2020;Gaynor et al, 2020;Zhou et al, 2020). Therefore, studies characterizing and comparing morphological and abiotic environmental differences between disjunct pairs using a phylogenetic framework would be highly useful to address the questions of morphostasis and to better understand the evolution of EA-ENA disjunct floras post-isolation.…”