The general prevalence of sexual reproduction over asexual reproduction among organisms testifies to the evolutionary benefits of recombination, such as accelerated adaptation to changing environments and elimination of deleterious mutations. Documented instances of asexual reproduction in groups otherwise dominated by sexual reproduction challenge evolutionary biologists to understand the special circumstances that might confer an advantage to asexual reproductive strategies. Here we report one such instance of asexual reproduction in the ants. We present evidence for obligate thelytoky in the asexual fungus-gardening ant, Mycocepurus smithii, in which queens produce female offspring from unfertilized eggs, workers are sterile, and males appear to be completely absent. Obligate thelytoky is implicated by reproductive physiology of queens, lack of males, absence of mating behavior, and natural history observations. An obligate thelytoky hypothesis is further supported by the absence of evidence indicating sexual reproduction or genetic recombination across the species' extensive distribution range (Mexico-Argentina). Potential conflicting evidence for sexual reproduction in this species derives from three Mycocepurus males reported in the literature, previously regarded as possible males of M. smithii. However, we show here that these specimens represent males of the congeneric species M. obsoletus, and not males of M. smithii. Mycocepurus smithii is unique among ants and among eusocial Hymenoptera, in that males seem to be completely absent and only queens (and not workers) produce diploid offspring via thelytoky. Because colonies consisting only of females can be propagated consecutively in the laboratory, M. smithii could be an adequate study organism a) to test hypotheses of the population-genetic advantages and disadvantages of asexual reproduction in a social organism and b) inform kin conflict theory.For a Portuguese translation of the abstract, please see Abstract S1.

International audienceSeveral groups of solitary bees, known as oil-collecting bees, gather lipids from flowers that offer them as their main reward to pollinators. In the Neotropical region, oil-collecting bees belong to the tribes Centridini, Tapinotaspidini, and Tetrapediini (Apidae: Apinae). The floral oils collected by females of these groups are used as larval food or in nest construction. The interaction of these bees with oil flowers is characterized by the presence of specialized structures for oil collection on the legs that morphologically match the location and type of the oil-producing glands on flowers they visit. In addition, these bees have specialized arrays of setae (including the scopae) for oil transport. In a few genera, both sexes display such specialized structures, although floral oil collection has hitherto been regarded as an exclusively female task. Here, we report floral oil collection by males of Tetrapedia, a Neotropical genus of oil-collecting bees. We describe behavioral aspects of oil foraging by males, present data on morphological structures associated with the collection of this resource, and discuss potential hypotheses to explain the significance of floral oils in the mating system of Tetrapedia

Eglandular flowers represent a shift in the pollination system in which oil is being lost and pollen is becoming the main reward of P. pyroidea flowers. Pollination shifts of this kind have hitherto not been demonstrated empirically within Neotropical Malpighiaceae and this species exhibits an unusual transition from a specialized towards a generalized pollination system in an area considered the hotspot of oil-collecting bee diversity in the Neotropics. Transitions of this type provide an opportunity to study ongoing evolutionary mechanisms that promote the persistence of species previously involved in specialized mutualistic relationships.

A new study provides the first broad timeline of bee diversification. Several ancient bee clades are identified as ghost lineages that have left little fossil evidence of their existence. This timeline suggests that the rise of bees coincided with the largest flowering plant clade, the eudicots.