3RAD-based systematics of the transitional Nearctic-Neotropical lubber grasshopper genus Taeniopoda (Orthoptera: Romaleidae)

摘要

The genus Taeniopoda Stal (Romaleidae) is a group of Nearctic-Neotropical grasshoppers whose systematics has been largely neglected. A recent phylogenetic study based on morphology and mitochondrial and nuclear markers failed to resolve the species boundaries in this genus and showed a lack of reciprocal exclusivity between T. eques (Burmeister) and T. tamaulipensis Rehn. Here we assessed the species limits and phylogenetic relationships in Taeniopoda based on 3RAD data, and evaluated the presence of gene flow and niche overlap between the above two species using clustering and ecological niche modelling (ENM) analyses to determine their taxonomic status. We performed de novo assembly of different 3RAD data sets with distinct parameters settings to explore whether they impact the recovered relationships. Ten species were consistently delimited, with T. picticornis and T. stali regarded as conspecific and the populations of T. auricornis from Guatemala representing a separate species. We maintained the specific status of T. eques and T. tamaulipensis, though our results suggest that they represent a ring species since their genetic composition appear to change gradually following a "loop form" along their geographical distribution. The phylogenomic analyses confirmed the paraphyly of Taeniopoda with respect to Romalea and recovered three major clades. Similar to previous studies, the relationships of our examined matrices were highly congruent despite their different levels of missing data. However, the similarity threshold and minimum number of samples that must share a locus for it to be retained impact the amount of loci and missing data of the matrices. This study demonstrates the utility of 3RAD to detect gene flow and to resolve species limits and phylogenetic relationships among closely related taxa.