Phylogenomics reveals within species diversification but incongruence with color phenotypes in widespread orchid bees (Hymenoptera: Apidae: Euglossini)

Authors: SANDOVAL-ARANGO, STEPHANIA - Pennsylvania State University; Branstetter, Michael; CARDOSO, CAROLINA - Universidade Federal De Minas Gerais; LOPEZ-URIBE, MARGARITA - Pennsylvania State University

Submitted to: Insect Systematics and Diversity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2023
Publication Date: 3/14/2023
Citation: Sandoval-Arango, S., Branstetter, M.G., Cardoso, C.F., Lopez-Uribe, M.M. 2023. Phylogenomics reveals within species diversification but incongruence with color phenotypes in widespread orchid bees (Hymenoptera: Apidae: Euglossini). Insect Systematics and Diversity. 7(2). Article 1. https://doi.org/10.1093/isd/ixad005.
DOI: https://doi.org/10.1093/isd/ixad005

Interpretive Summary: Color is often used in bee taxonomy to separate and identify species. Increasing evidence, however, suggests that color can often be misleading in taxonomic research due to a variety of factors. One bee group where it is uncertain if color is a good separatory character or not is the orchid bee genus Eulaema, which is a large group of orchid pollinating bees that primarily occur in the tropics. To test species boundaries based on color, researchers generated ultraconserved element phylogenomic data for all color forms in two groups of Eulaema species. In both cases, molecular data revealed that color does not accurately separate species and that each species group likely includes a single species with many color morphs. This study improves knowledge of bee species diversity and demonstrates the value of including molecular data in taxonomic research.

Technical Abstract: Coloration is an important phenotypic trait for taxonomic studies and has been widely used for identifying insect species and populations. However, coloration can be a poor diagnostic character for insect species that exhibit high polymorphism in this trait, which can lead to over-splitting of taxonomic units. In orchid bees, color variation has been interpreted by different taxonomists as either polymorphism associated with Mullerian mimicry complexes or diagnostic traits for species identification. Despite this uncertainty, integrative approaches that incorporate multiple independent datasets to test the validity of hair coloration as a character that identifies independent evolutionary units have not been used. Here, we use phylogenomic data from Ultraconserved Elements (UCEs) to explore whether color phenotypes in the widespread orchid bee species complexes Eulaema meriana and Eulaema bombiformis correspond to independent lineages or polymorphic trait variation within species. We find that lineages within both species are structured according to geography and that color morphs are generally unassociated with evolutionarily independent groups except for populations located in the Atlantic Forest of Brazil. We conclude that there is compelling evidence that E. atleticana and E. niveofasciata are subspecies of E. meriana and E. bombiformis, respectively, and not different species as previously suggested. Therefore, we recognize Eulaema meriana atleticana comb. n. and Eulaema bombiformis niveofasciata comb. n. and discuss their morphological characteristics. We make recommendations on the use of color traits for orchid bee taxonomy and discuss the significance of subspecies as evolutionary units relevant for conservation efforts.