Biology subjects

Liu, B.-B.

Publications and source records attributed to Liu, B.-B..

5 recordsLinked to original sources

bioRxiv2023

A phylogenomic approach, combined with morphological characters gleaned via machine learning, uncovers the hybrid origin and biogeographic diversification of the plum genus

The evolutionary histories of species have been shaped by genomic, environmental, and morphological variation. Understanding the interactions among these sources of variation is critical to infer accurately the biogeographic history of lineages. Here, using the geographically widely distributed plum genus (Prunus, Rosaceae) as a model, we investigate how changes in genomic and environmental variation drove the diversification of this group, and we quantify the morphological features that facilitated or resulted from diversification. We sequenced 587 nuclear loci and complete chloroplast genomes from 99 species representing all major lineages in Prunus, with a special focus on the understudied tropical racemose group. The environmental variation in extant species was quantified by synthesizing bioclimatic variables into principal components of environmental variation using thousands of georeferenced herbarium specimens. We used machine learning algorithms to classify and measure morphological variation present in thousands of digitized herbarium sheet images. Our phylogenomic and biogeographic analyses revealed that ancient hybridization and/or allopolyploidy spurred the initial rapid diversification of the genus in the early Eocene, with subsequent diversification in the north temperate zone, neotropics, and paleotropics. This diversification involved successful transitions between tropical and temperate biomes, an exceedingly rare event in woody plant lineages, accompanied by morphological changes in leaf and reproductive morphology. The machine learning approach detected morphological variation associated with ancient hybridization and quantified the breadth of morphospace occupied by major lineages within the genus. The paleotropical lineages of Prunus have diversified steadily since the late Eocene/early Oligocene, while the neotropical lineages diversified much later. Critically, both the tropical and temperate lineages have continued to diversify. We conclude that the genomic rearrangements created by reticulation deep in the phylogeny of Prunus may explain why this group has been more successful than other groups with tropical origins that currently persist only in either tropical or temperate regions, but not both.

evolutionary biology↗

bioRxiv2023

Phylogenomic analyses support a new infrageneric classification of Pourthiaea (Maleae, Rosaceae) using multiple inference methods and extensive taxon sampling

In this comprehensive study, we conducted extensive taxon sampling and performed phylogenomic analyses based on plastome and nuclear ribosomal DNA (nrDNA) datasets. We employed multiple inference methods, including concatenated and coalescent-based strategies, to generate an accurate phylogeny of the woody Rosaceae genus Pourthiaea. The nrDNA phylogeny of Pourthiaea strongly supported three major clades, which were consistent with morphology. However, the plastid tree provided an alternative phylogenetic topology, indicating cytonuclear discordance. Frequent hybridizations between and among the species of Pourthiaea could explain the cytonuclear discordance. Considering the evidence from morphology and phylogenomic data, we propose a new infrageneric classification for Pourthiaea, consisting of three sections: P. sect. Pourthiaea, P. sect. Amphidoxae B.B.Liu, and P. sect. Impressivenae B.B.Liu.

plant biology↗

bioRxiv2023

Nightmare or delight: taxonomic circumscription meets reticulate evolution in the phylogenomic era

Phylogenetic studies in the phylogenomics era have demonstrated that reticulate evolution greatly impedes the accuracy of phylogenetic inference, and consequently can obscure taxonomic treatments. However, the systematics community lacks a broadly applicable strategy for taxonomic delimitation in groups identified to have pervasive reticulate evolution. The red-fruit genus, Stranvaesia, provides an ideal model for testing the effect of reticulation on generic circumscription when hybridization and allopolyploidy define a groups evolutionary history. Here, we conducted phylogenomic analyses integrating data from hundreds of single-copy nuclear (SCN) genes and plastomes, and interrogated nuclear paralogs to clarify the inter/intra-generic relationship of Stranvaesia and its allies in the framework of Maleae. Analyses of phylogenomic discord and phylogenetic networks showed that allopolyploidization and introgression promoted the origin and diversification of the Stranvaesia clade, a conclusion further bolstered by cytonuclear and gene tree discordance. The well-inferred phylogenetic backbone revealed an updated generic delimitation of Stranvaesia and a new genus, Weniomeles, characterized by purple-black fruits, trunk and/or branches with thorns, and fruit core with multilocular separated by a layer of sclereids and a cluster of sclereids at the top of the locules. Here, we highlight a broadly-applicable workflow for inferring how analyses of reticulate evolution in phylogenomic data can directly shape taxonomic revisions.

evolutionary biology↗

bioRxiv2021

Phylogenomic analyses in the apple genus Malus s.l. reveal widespread hybridization and allopolyploidy driving the diversifications, with insights into the complex biogeographic history in the Northern Hemisphere

Phylogenomic evidence from an increasing number of studies has demonstrated that different data sets and analytical approaches often reconstruct strongly supported but conflicting relationships. In this study, hundreds of single-copy nuclear (SCN) genes (785) and complete plastomes (75) were used to infer the phylogenetic relationships and estimate the historical biogeography of the apple genus Malus sensu lato, an economically important lineage disjunctly distributed in the Northern Hemisphere involved in known and suspected hybridization and allopolyploidy events. The nuclear phylogeny recovered the monophyly of Malus s.l. (including Docynia); however, it was supported to be biphyletic in the plastid phylogeny. An ancient chloroplast capture event best explains the cytonuclear discordance that occurred in the Eocene in western North America. Our conflict analysis demonstrated that ILS, hybridization, and allopolyploidy could explain the widespread nuclear gene tree discordance. We detected one deep hybridization event (Malus doumeri) involving the ancestor of pome-bearing species and Docynia delavayi, and one recent hybridization event (Malus coronaria) between M. sieversii and a combined clade of M. ioensis and M. angustifolia. Furthermore, our historical biogeographic analysis combining living and fossil species supported a widespread East Asian-western North American origin of Malus s.l., followed by a series of extinction events in the Eocene in northern East Aisa and western North America. This study provides a valuable evolutionary framework for the breeding and crop improvement of apples and their close relatives.

evolutionary biology↗

bioRxiv2021

Capturing single-copy nuclear genes, organellar genomes, and nuclear ribosomal DNA from deep genome skimming data for plant phylogenetics: A case study in Vitaceae

With the decreasing cost and availability of many newly developed bioinformatics pipelines, next-generation sequencing (NGS) has revolutionized plant systematics in recent years. Genome skimming has been widely used to obtain high-copy fractions of the genomes, including plastomes, mitochondrial DNA (mtDNA), and nuclear ribosomal DNA (nrDNA). In this study, through simulations, we evaluated optimal (minimum) sequencing depth and performance for recovering single-copy nuclear genes (SCNs) from genome skimming data, by subsampling genome resequencing data and generating 10 datasets with different sequencing coverage in silico. We tested the performance of the four datasets (plastome, nrDNA, mtDNA, and SCNs) obtained from genome skimming based on phylogenetic analyses of the Vitis clade at the genus-level and Vitaceae at the family-level, respectively. Our results showed that optimal minimum sequencing depth for high-quality SCNs assembly via genome skimming was about 10x coverage. Without the steps of synthesizing baits and enrichment experiments, we showcase that deep genome skimming (DGS) is effective for capturing large datasets of SCNs, in addition to plastomes, mtDNA, and entire nrDNA repeats, and may serve as an economical alternative to the widely used target enrichment Hyb-Seq approach.

evolutionary biology↗