Phylogenetic and Taxonomic Status Analyses of the Abaso Section from Multiple Nuclear Genes and Plastid Fragments Reveal New Insights into the North America Origin of Populus (Salicaceae)

Abstract

Although, the Abaso section is widely accepted as an independent section, the taxonomic status of Populus mexicana (section Abaso) has not yet been resolved due to the limited availability markers and/or the lack of P. mexicana specimens in previous studies. Thirty-one poplar species that represent six sections of the Populus genus were sampled, and 23 single-copy nuclear DNA and 34 chloroplast fragments were sequenced. The present study obtained two updated phylogenies of Populus. We found that monophyly of the genus Populus is strongly supported by nuclear and plastid gene, which is consistent with previous studies. P. mexicana, diverged first in the nuclear DNA tree, which occupied the basal position, implying that the section Abaso may be the most ancestral lineage in extant populous species. Given that the short branches and low statistical support for the divergence of sections Abaso and Turanga, this observation probably indicated that a rapid radiation evolution following the early split of the genus Populus. In the plastid tree, P. mexicana clustered with modern-day species of section Tacamahaca in the plastid tree. Based on cytoplasmic and single-copy nuclear marker sequences, we hypothesized that chloroplast capture resulted in the inconsistent position of P. mexicana between the phylogenetic trees. Given the first unequivocal records of poplar fossils from the Eocene with similar leaf morphology to the extant P. mexicana and the phylogenetic positions of P. mexicana in our study, we support the hypothesis that the Populus genus originated in North America, which will provide new insights to the development of the origin of Populus species.

Ancient polymorphisms and divergence hitchhiking contribute to genomic islands of divergence within a poplar species complex

“…Populus euphratica Oliv. (Pe) and Populus pruinosa Schrenk (Pp) are two sister species in section Turanga ( 37 – 39 ), both of which are well adapted to the extreme desert environment ( SI Appendix , Fig. S1 ).…”

Targeted sequence capture array for phylogenetics and population genomics in the Salicaceae

“…S1). Previous studies have provided evidence of historical introgression among these species, including a history of chloroplast capture and hybridization Sanderson -Targeted sequence capture in Salicaceae p. 12 between P. mexicana and species in the section Tacamahaca (including P. balsamifera; Wang et al, 2014Wang et al, , 2020Liu et al, 2017). The second most supported alternative topology that we recovered placed P. mexicana and P. tremula as sister taxa, a pattern that does not support this hypothesis, likely due to incomplete lineage sorting (Wang et al, 2020).…”

“…Our primary focus was on the genera Populus and Salix, which diverged approximately 48 Mya, and the species Idesia polycarpa Maxim, which diverged from other clades approximately 56 Mya, which we use as an outgroup (Zhang et al, 2018b). Although we were interested in using these probes for phylogenetics with both Populus and Salix species, we focused on maximizing capture efficiency for the species in Salix, because the phylogeny for Populus is already much better resolved than that for Salix (Trybush et al, 2008;Wang et al, 2014Wang et al, , 2020Percy et al, 2014;Liu et al, 2017).…”

Comparative Genome and Transcriptome Analysis Reveals Gene Selection Patterns Along with the Paleo-Climate Change in the Populus Phylogeny

“…[2] and Populus pruinosa Schrenk [3]. Several studies have focused on this genus, particularly with regard to its phylogenetic relationships [4,5], origin and speciation [6][7][8]; the timing of diversification events [9][10][11]; and environmental stress tolerance [12,13]. However, no study explains how poplars have adapted to various climates during its long evolutionary history.…”