Morphological differences between Tetragonisca angustula and Tetragonisca fiebrigi (Apidae: Meliponini)

Abstract

Tetragonisca angustula and T. fiebrigi are morphologically similar and differentiated mainly by the mesepisternum color, black in the former and ferruginous in the latter. Mixed mesepisternum color on some bees has raised discussions about the taxonomic status of these species if some degree of hybridization can occur between them and they should be regarded as subspecies. Our goal was to investigate if T. angustula and T. fiebrigi are two valid species and contribute to their taxonomic identification. We sampled several colonies from distant Brazilian regions (range of 3,000 km) to analyze the mesepisternum color variation of males and workers, genitalia morphology of males and females (queens and workers), and aggressiveness of the workers in both species. Despite some color variations in some colonies, there are always individuals with typical mesepisternum color inside each colony, i.e., black in T. angustula and ferruginous in T. fiebrigi. The fact that both T. angustula and T. fiebrigi males have black mesepisternum could be causing species misclassifications. The genitalia morphology of males (shape and length of gonostylus and penis valve) and females (gonostylus shape) was consistently different between both species. None of the analyzed male aggregations exhibited mixed males of T. angustula and T. fiebrigi, which indicates that the queen attracts only co-specific males. Tetragonisca angustula workers displayed an aggressive behavior, whereas T. fiebrigi workers were unaggressive. The observed morphological and behavioral differences may be indicators of reproductive isolation between the two species. Therefore, we conclude that T. angustula and T. fiebrigi are two valid species.