Species delimitation and phylogenetic relationships in the genus Trypoxylon (Hymenoptera: Crabronidae) using molecular markers: an alternative to taxonomic impediment

Abstract

The taxonomic identification of species is an essential issue in biological studies, as the uncertain taxonomy of a species hinders the investigation of its biology. Limitations regarding the description and identification of new species characterizes the “taxonomic impediment”. The genus Trypoxylon is an example of a taxon with this difficulty, particularly in the Neotropical region. It is a diverse genus composed of 631 described species that is divided in two subgenera – Trypoxylon (Trypoxylon), and Trypoxylon (Trypargilum), which are subdivided into groups and species complexes. To overcome the taxonomic impediment of Trypoxylon, the aim of the present study is to i) estimate molecular variation in order to delimit Trypoxylon species, and ii) determine evolutionary relationships among species to validate the morphological and behaviour-based infrageneric classification employing molecular data. The species delimitation analysis based on 333 COI sequences using genetic distance and phylogenetic and coalescence methods enabled us to define the single-threshold GMYC as the best model, as 45 out of 40 morphotypes/species were defined using this method. To determine phylogenetic relationships, we used sequences from two mitochondrial markers COI (n = 38) and CytB (n = 38) and a nuclear marker pol (n = 26), showing that molecular data were congruent with the infrageneric division of Trypoxylon and pointing to a probable third clade among Trypoxylon (Trypargilum) species. Moreover, the COI sequence-based estimation of divergence time (n = 102) suggests that Trypoxylon diversified in the Upper Cretaceous, and subsequent cladogenetic events occurred more frequently between the Eocene/Oligocene and throughout the Neogene. In summary, the molecular approach proved to be useful for overcoming difficulties in identifying Neotropical species of Trypoxylon.

Key words:

• COI
• DNA Barcode
• mitochondrial markers
• molecular systematics
• nuclear markers
• phylogenetic analysis

Acknowledgements

We are grateful to the editorial of Systematics and Biodiversity for the suggestions and contributions in our study. We would also like to show our gratitude to Danúbia Maria da Costa, Dr. Gustavo Araújo, Dr. Tiago Izzo and Dr. Daércio Lucena for contributing with specimens for this study, and to José Carlos Serrano for identifying some Trypoxylon specimens. Our sincere thanks are addressed to Fernando Gabriel Mazur, whose commentaries and useful suggestions improved the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplemental data

Supplemental data for this article can be accessed here: https://doi.org/doi/10.1080/14772000.2020.1758824.

Associate Editor: Rosa Fernandez

Additional information

Funding

This research was supported by the Brazilian fostering agency Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq; Grant No. 456118/2014-4) and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brazil (CAPES) – Finance Code 001.