Two Colors, One Species: The Case of Melissodes nigroaenea (Apidae: Eucerini), an Important Pollinator of Cotton Fields in Brazil

Abstract

Accurate taxonomic delimitation in ecological research is absolutely critical as studies that seek to evaluate levels of biodiversity and qualify 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. In this study, we use a DNA barcoding approach to investigate the interpretation of two color morphs (yellow or dark) in the eucerine bee Melissodes nigroaenea. Our hypothesis is that if significant genetic divergence exists between each morphotype of M. nigroaenea, coloration reflects two distinct evolutionary lineages within this species, which may require taxonomic revision. Our alternative hypothesis is that, if genetic divergence is low between each morphotype of M. nigroaenea, we can attribute this variation to color polymorphism. Our Bayesian phylogenetic reconstruction revealed that both yellow and black individuals clustered together in a highly supported phylogenetic group. Additionally, pairwise genetic distances between M. nigroaenea color morphotypes were lower than 3%. These results indicate that both mesosome color morphs correspond to intraspecific variability within the same evolutionary unit. Together, our results indicate that mesosome coloration is not a reliable character for taxonomic differentiation of these Melissodes species, and that the incorporation of DNA barcoding approaches to taxonomic classification can help resolve some of the problems that originate while relying on purely morphological taxonomy.

Crop and Semi-Natural Habitat Configuration affects Diversity and Abundance of Native Bees (Hymenoptera: Anthophila) in a Large-Scale Cotton Agroecosystem

“…Despite the dominance of the crop-crop interfaces and other aspects of agricultural intensification, the bee communities were similar in terms of species richness at different interfaces of this highly structured large-scale cotton agroecosystem, suggesting benefits or at least no antagonism of crops intermixed and dominating the original natural gulf prairie habitat. Compared to other studies, where increasing native bee diversity and richness in more diverse landscapes was seen, our findings were rather unexpected given the higher diversity and abundance within agricultural interfaces [10,43,44]. Further, samples taken from natural habitat alone (NH) appeared to have a lower estimated species richness than all cottoncrop or cotton-natural habitat interfaces, supporting that flowering cotton and possibly other resources provided by sorghum benefited at least M. tepaneca in this agroecosystem that was designed from a cotton production perspective.…”

“…The genus Melissodes also appears to be important in cotton outside of the U.S. In Brazil, M. nigroaena (Smith) has been identified as an important pollinator in small-scale cotton agroecosystems systems [43,44].…”

A Native Bee, Melissodes tepaneca (Hymenoptera: Apidae), Benefits Cotton Production

“…In these studies, the most abundant pollinator was in the genus Melissodes . In Texas, M. tepeaneca was found to be most abundant (species used in our study), and in Brazil, M. nigroaenea was most abundant [ 16 ]. A key difference in our study is that the M. tepaneca sourced for our experiments were taken from large scale commercial cotton fields with relatively little semi-natural habitats present compared to those monitored by Grando et al [ 16 ].…”

“…We note that in the caged flowers not exposed to M. tepaneca , some remnant insects (primarily sucking bugs [ 9 ]) may have been trapped inside at the time of covering the plants. However, these insects have not been noted as cotton pollinators in the literature [ 3 , 5 , 11 , 16 ]. Further, although direct pollination observations were not done for M. tepaneca within the experimental plots, native bees and other potential pollinators were observed in the cotton field where the experiment was conducted and in cotton fields within the region [ 4 , 10 , 15 , 17 ].…”

“…For example, three species in the genus Melissodes were found to be relatively abundant in Pima cotton fields in Arizona [ 4 ]. In Brazil, Melissodes nigroanea has been found to be the most abundant species of native bee in cotton [ 16 ]. Melissodes nigroanea has also been recorded in studies that indicate benefits to cotton flowers left exposed to pollinators compared to caged flowers in Brazil [ 2 ].…”