Abstract Detail

Phylogenomics

Gallego-Narbón, Angélica [1], Wen, Jun [2], Valcarcel, Virginia [3].

Ancient allopolyploidy, early radiation and extensive hybridization have shaped the evolutionary history of the Asian Palmate Group (Araliaceae).

Araliaceae is a diverse plant family (c. 50 genera and 1500 species) distributed mostly in tropical and subtropical latitudes [1]. Phylogenetic studies reveal three main named clades (Asian Palmate group, Aralia-Panax, and Polyscias-Pseudopanax) in addition to a basal polytomy with a number of poorly diversified genera. The Asian Palmate Group (AsPG) is the most diverse clade of Araliaceae, including 23 genera and c. 900 species. Although the evolutionary history of this group has been extensively studied, the phylogenetic relationships of its genera remain unclear. The latest plastome-based study did not resolve most internal nodes, suggesting an early radiation [2]. Additionally, the nuclear phylogenies obtained using ITS display low resolution. Nevertheless, incongruence at internal nodes when compared with plastid topologies was found, suggesting inter-genera hybridization [3]. In this study we use the next-generation sequencing (NGS) technique Hyb-Seq to obtain nuclear and plastid phylogenies. We seek to test the radiation with inter-genera hybridization hypothesis for the early diversification of the AsPG and evaluate if hybridization was also a driving force for the origin of the large AsPG clade. A Hyb-Seq library with 62 samples was obtained and analyzed with 10 other samples already available, representing the main clades of Araliaceae with a special emphasis on the AsPG. We extracted 926 targeted nuclear loci using the HybPiper pipeline and plastomes were obtained using an Eleutherococcus senticosus genome as a reference (JN637765). Paralogy was assessed running phylogenetic analyses with and without paralogs. Concatenation-based maximum likelihood (ML) and Bayesian Inference (BI) analyses were applied for nuclear and plastid matrices and ASTRAL was used to implement a coalescent-based approach for nuclear data and quartets support was obtained. The impact of hybridization and incomplete lineage sorting (ILS) was decoupled using SNaQ. Chromosome evolution was assessed using ChromEvol. The resulting nuclear concatenation-based phylogenies without paralogs had 315 loci and the plastid phylogeny included 261 loci, with 94% and 97% of branches supported, respectively. The two phylogenies supported the early radiation hypothesis, and major conflict signals confirmed the hybridization hypothesis. Interestingly, coalescence-based analyses (ASTRAL, SNaQ) provided low resolution at internal nodes, and suggest extensive hybridization coupled with ILS. Altogether, these results provide robust support for the early radiation with inter-genera hybridization hypothesis of the AsPG. Besides, evidence of inter-lineages hybridization has also been recovered among the main clades of Araliaceae and, particularly, for the origin of AsPG. This hybridization is also coupled with a whole genome duplication, as inferred with ChromEvol. Our results point to an allopolyploid origin of the AsPG followed by a radiation event that lead to extensive ILS. These events in combination with the early inter-genera hybridization have complicated the phylogenetic signal in the early evolution of this large major clade of Araliaceae.
[1] Wen et al. 2001. Systematic Botany 26: 144-167
[2] Valcárcel & Wen. 2019. JSE 57: 547-560
[3] Valcárcel et al. 2014. Mol Phylogenet Evol 70:492-503

1 - Universidad Autónoma de Madrid, Department of Biology, Campus de Cantoblanco, C/ Darwin 2, Madrid, 28049, Spain
2 - Botany, MRC-166 National Museum Of Natural History, 10th St. & Constitution Ave., NW, Mrc 166, Washington/DC, 20013, United States
3 - Universidad Autonoma De Madrid, Molecular Biology, Campus De Canto Blanco. Fac. Ciencias., Calle Darwin, 2 (Edif. Biologia, Botanica), Madrid, M, 28049, Spain

Keywords:
Araliaceae
phylogenomics
hybridization
Radiation
ILS.

Presentation Type: Poster
Number: PPL001
Abstract ID:102
Candidate for Awards:None