Two colors, one species: The case of melissodes nigroaenea (Apidae: Eucerini), an important pollinator of cotton fields in Brazil

Accurate taxonomic delimitation in ecological research is absolutely critical as studies that seek to evaluate levels of biodiversity and quantify human effects on the environment are rapidly undertaken. Coloration is a widely used morphological character for species identification through dichotomous keys. However, taxonomic identification based upon coloration is often unreliable because this character can exhibit high degree of intraspecific variation. An uncertain interpretation of mesosoma color-morphs (yellow or black) occurred when we used this character, in association with the bristle bands in the TII, for the identification of eucerine bee Melissodes nigroaenea (Smith), an important pollinator of cotton fields in South America. Thus, we used a DNA barcoding approach to investigate if different color morphs within this species reflected two distinct evolutionary lineages. Our Bayesian phylogenetic reconstruction revealed that both yellow and black individuals clustered in a highly supported monophyletic group. Additionally, pairwise genetic distances between M. nigroaenea color-morphotypes were lower than 3%. These results indicate that both mesosoma color-morphs correspond to intraspecific variability within the same evolutionary unit. Although the mesosoma coloration is not the unique character considered for taxonomic differentiation among Melissodes species, our results indicate that this character is not reliable for Melissodes species differentiation. The incorporation of DNA barcoding approaches to taxonomic classification can help resolve some of the problems that originate while relying on purely morphological taxonomy.