Yardeni et al. 2023 (Book) Tillandsia

The explosive radiation of the Neotropical Tillandsia subgenus Tillandsia (Bromeliaceae) has been facilitated by pervasive hybridization

Author(s):—G. Yardeni, M. Barfuss, W. Till, M. Thornton, C. Groot Crego, C. Lexer, T. Leroy & O. Paun

Publication:— (2023). — DOI

Abstract:—The recent rapid radiation of Tillandsia subgenus Tillandsia (Bromeliaceae) provides an
attractive system to study the drivers and limits of species diversification. This species-rich
Neotropical monocot clade includes predominantly epiphytic species displaying vast
phenotypic diversity. Recent in-depth phylogenomic work revealed that the subgenus
originated within the last 7 MY while expanding through one major event from South into
Central America within the last 5 MY. However, disagreements between phylogenies and
lack of resolution at shallow nodes suggested that hybridization occurred throughout the
radiation, together with frequent incomplete lineage sorting and/or considerable gene family
evolution. We used whole-genome resequencing data and a newly available reference
genome to explore the evolutionary history of 34 representative ingroup species employing
both a tree-based and a network approach. Our results indicate that lineage co-occurrence
does not predict relatedness and confirm significant deviations from a tree-like structure,
coupled with pervasive gene tree discordance. Focusing on hybridization, ABBA-BABA and
related statistics were used to infer the rates and relative timing of introgression, while
topology weighting uncovered high heterogeneity of the phylogenetic signal along the
genome. High rates of hybridization within and among clades suggest that, in contrast to
previous hypotheses, the expansion of subgenus Tillandsia into Central America proceeded in
several dispersal events, punctuated by episodes of diversification and gene flow. Network
analysis revealed reticulation as a prominent propeller during radiation and establishment in
different ecological niches. This work contributes a plant example of prevalent hybridization during rapid species diversification, supporting the hypothesis that interspecific gene flow
facilitates explosive diversification.

Keywords:—Tillandsia, gene tree discordance, hybridization, phylogenomics, bromeliad, Neotropical diversity, species network