ABSTRACT
The process of hybridization occurs in approximately 40% of vascular plants, and this exchange of genetic material between non-conspecific individuals occurs unequally among plant lineages, being more frequent in certain groups such as Opuntia (Cactaceae). This genus is known for multiple taxonomic controversies due to widespread polyploidy and probable hybrid origin of several of its species. Southern Mexico species of this genus have been poorly studied despite their great diversity in regions such as the Tehuacán-Cuicatlán Valley which contains around 12% of recognized Mexico's native Opuntia species. In this work, we focus on testing the hybrid status of two putative hybrids from this region, Opuntia tehuacana and Opuntia pilifera, and estimate if hybridization occurs among sampled southern opuntias using two newly identified nuclear intron markers to construct phylogenetic networks with HyDe and Dsuite and perform invariant analysis under the coalescent model with HyDe and Dsuite. For the test of hybrid origin in O. tehuacana, our results could not recover hybridization as proposed in the literature, but we found introgression into O. tehuacana individuals involving O. decumbens and O. huajuapensis. Regarding O. pilifera, we identified O. decumbens as probable parental species, supported by our analysis, which sustains the previous hybridization hypothesis between Nopalea and Basilares clades. Finally, we suggest new hybridization and introgression cases among southern Mexican species involving O. tehuantepecana and O. depressa as parental species of O. velutina and O. decumbens.
ABSTRACT
Aim A number of processes can lead to weak or conflicting phylogenetic signals, especially in geographically dynamic regions where unstable landscapes and climates promote complex evolutionary histories. The Middle American pitviper genus Bothriechis has a complex biogeographic distribution and previous phylogenetic analyses have recovered conflicting topologies based on the data type used. Here, we tested whether historic conflicts in the phylogeny were the result of reticulate evolution and whether the inferred biogeographic history of the group would enable contact among reticulate lineages.Location Middle America. Taxon Palm-pitvipers (genus Bothriechis). Methods We generated a phylogenomic dataset using an anchored phylogenomics approach and inferred a genomics-based species tree and mitochondrial tree to assess incongruence among datasets. We then generated a dated phylogeny and conducted ancestral area reconstruction to examine the biogeographic history surrounding the diversification of these species. We additionally tested whether the discordance among trees is better explained by lineage sorting or reticulate evolution by testing models of reticulate evolution inferred through multiple methods. Results We found strong support for discordance in the phylogeny of Bothriechis and corresponding evidence for reticulate evolution among lineages with incongruent placement. Ancestralarea reconstruction placed these taxa in adjacent regions during the time period when reticulation was projected to take place and suggested a biogeographic history heavily influenced by vicariant processes. Main conclusions Reticulation among geographically proximate lineages has driven apparent genomic discordance in Bothriechis and is responsible for historical incongruence in the phylogeny. Inference of the order of events suggests that reticulation among nuclear Middle American taxa occurred during a time of geologic upheaval, promoting lineage divergence and secondary contact. Reticulate evolution and similar processes can have substantial impacts on the evolutionary trajectory of taxa and are important to explicitly test for in biogeographically complex regions.