Climatic niche evolution in Smilacaceae (Liliales) drives patterns of species diversification and richness between the Old and New World

Abstract

Geographical variation in species richness in plant groups is determined by the interplay between historical, evolutionary, and ecological processes. However, the processes underlying the striking disparity in species richness between Asia and the Americas remain poorly understood. Here, we synthesize global phylogenetic and macroecological data on the diversification of Smilacaceae, deciphering potential drivers underlying the species diversity pattern biased toward Asia. We compiled global distributions of all Smilacaceae species, and reconstructed the biogeographic history and niche evolution using a new time‐calibrated phylogeny (eight genes, 135 species). Integrating these data sets, we estimated evolutionary histories and diversification rates for each region, and tested correlations among species diversification, niche evolution, and niche divergence. Smilacaceae probably originated during the Late Cretaceous/Early Palaeocene and began to diversify in middle to low latitudes in Central America and Eurasia during the Late Eocene. Both the Old and New World clades exhibited a steady, albeit slight, increase of species diversification from the Late Eocene to Early Miocene. However, the Old World clade experienced an abrupt increase in net diversification during the Late Miocene. Our findings also revealed that species diversification rates were positively correlated with ecological niche evolution and niche divergence. Niche shifts and climatic niche evolution since the Middle Miocene played crucial roles in species diversification dynamics within Smilacaceae. The high plant richness in Asia may be explained by greater diversification in this region, potentially promoted by heterogeneous environments.

A New Endemic Smilax (Smilacaceae) from Tafelberg, Suriname, Supported by Morphometric and Phylogenetic Evidence

“…Phylogenetic Sampling and Sequencing-Taxon sampling for DNA sequencing was based on three criteria: 1) taxa not included in Qi et al (2013Qi et al ( , 2023 and/or GenBank, 2) species from the Guiana Shield, and 3) species that resemble the Tafelberg populations, which are known from Brazil. We extracted genomic DNA from 16 herbarium specimens, representing 15 species, using a modified CTAB (Doyle and Doyle 1987) and employed a genome skimming approach (Straub et al 2012) as part of ongoing phylogenomic study of the New World clade.…”

“…SANGER DATASET-Because the plastome dataset did not achieve the same level of taxonomic sampling as what could be with existing data from Sanger loci on GenBank (Qi et al 2013(Qi et al , 2023, we extracted these Sanger loci from our plastome assemblies to place the taxa of interest in a broader phylogenetic context. To extract Sanger loci, we retrieved Sanger sequences of five plastid loci from Smilax offinicalis Kunth that are widely available for Smilax species on GenBank, rbcL, matK, ndhA, ndhF, and the rpl16 intron.…”

“…We used Geneious to map our plastome sequences (see "Plastome Dataset" above) to the Sanger loci and manually inspected alignments. The mapped regions from the plastome sequences were extracted and combined with GenBank data (Appendix 2) that were generated from Sanger-based studies (Qi et al 2013(Qi et al , 2023. Each locus was individually aligned with MAFFT with the '-adjustdirection' option to identify and correct reverse complement sequences.…”

“…Smilax L. is the sole genus of Smilacaceae, which is nearcosmopolitan in distribution and consists of approximately 300 described species. Molecular phylogenetic research has recovered three main subclades in Smilax (Qi et al 2013(Qi et al , 2023, 1) Smilax aspera DC., 2) species mostly distributed in the Americas, or New World, with exceptions of a handful of taxa that appear to represent long distance dispersal events, and 3) species mostly distributed in the Old World, with the exception of North American members of Smilax section Nemexia (Raf.) A.DC.…”

“…& C.DC. The Neotropics, one of the centers of diversity for Smilax, contains species that all putatively belong to the New World clade, but species from the region remain poorly sampled in comparison to the rest of the genus (Qi et al 2013(Qi et al , 2023.…”