Paulo Nogueira-Neto

Male production in stingless bees: variable outcomes of queen—worker conflict

The genetic structure of social insect colonies is predicted to affect the balance between cooperation and conflict. Stingless bees are of special interest in this respect because they are singly mated relatives of the multiply mated honeybees. Multiple mating is predicted to lead to workers policing each others’ male production with the result that virtually all males are produced by the queen, and this prediction is borne out in honey bees. Single mating by the queen, as in stingless bees, causes workers to be more related to each others’ sons than to the queens sons, so they should not police each other. We used microsatellite markers to confirm single mating in eight species of stingless bees and then tested the prediction that workers would produce males. Using a likelihood method, we found some worker male production in six of the eight species, although queens produced some males in all of them. Thus the predicted contrast with honeybees is observed, but not perfectly, perhaps because workers either lack complete control or because of costs of conflict. The data are consistent with the view that there is ongoing conflict over male production. Our method of estimating worker male production appears to be more accurate than exclusion, which sometimes underestimates the proportion of males that are worker produced.

Pulsed mass recruitment by a stingless bee, Trigona hyalinata

Research on bee communication has focused on the ability of the highly social bees, stingless bees (Hymenoptera, Apidae, Meliponini) and honeybees (Apidae, Apini), to communicate food location to nest–mates. Honeybees can communicate food location through the famous waggle dance. Stingless bees are closely related to honeybees and communicate food location through a variety of different mechanisms, many of which are poorly understood. We show that a stingless bee, Trigona hyalinata, uses a pulsed mass–recruitment system that is highly focused in time and space. Foragers produced an ephemeral, polarized, odour trail consisting of mandibular gland secretions. Surprisingly, the odour trail extended only a short distance away from the food source, instead of providing a complete trail between the nest and the food source (as has been described for other stingless bees). This abbreviated trail may represent an intermediate strategy between full–trail marking, found in some stingless bees, and odour marking of the food alone, found in stingless bees and honeybees.

The queen is dead—long live the workers: intraspecific parasitism by workers in the stingless bee Melipona scutellaris

Insect societies are well known for their high degree of cooperation, but their colonies can potentially be exploited by reproductive workers who lay unfertilized, male eggs, rather than work for the good of the colony. Recently, it has also been discovered that workers in bumblebees and Asian honeybees can succeed in entering and parasitizing unrelated colonies to produce their own male offspring. The aim of this study was to investigate whether such intraspecific worker parasitism might also occur in stingless bees, another group of highly social bees. Based on a large‐scale genetic study of the species Melipona scutellaris, and the genotyping of nearly 600 males from 45 colonies, we show that ∼20% of all males are workers’ sons, but that around 80% of these had genotypes that were incompatible with them being the sons of workers of the resident queen. By tracking colonies over multiple generations, we show that these males were not produced by drifted workers, but rather by workers that were the offspring of a previous, superseded queen. This means that uniquely, workers reproductively parasitize the next‐generation workforce. Our results are surprising given that most colonies were sampled many months after the previous queen had died and that workers normally only have a life expectancy of ∼30 days. It also implies that reproductive workers greatly outlive all other workers. We explain our results in the context of kin selection theory, and the fact that it pays workers more from exploiting the colony if costs are carried by less related individuals.

Multi-source odor-marking of food by a stingless bee, Melipona mandacaia

Social bees can deposit specialized glandular secretions, or signals, that allow foragers to revisit rewarding and to avoid unrewarding food sources. However, it is not known if bees can orient towards olfactory cues such as excreta deposited near food sources. We report that Melipona mandacaia foragers (stingless bees) deposit an odor cue, anal droplets, and a previously undescribed ventro-abdominal odor on food sources. Surprisingly, foragers deposited attractive odor marks on good food sources to which they recruited and on poor food sources to which they did not recruit. Foragers left the most anal droplets on dilute food sources to which they did not recruit (1.25-M sucrose solution), yet returning foragers were attracted to anal droplets obtained on poor food sources and presented in bioassays. Foragers were attracted to ventro-abdominal odors obtained on good food sources (2.5-M sucrose solution). Chemical extractions suggest that odor marks contain attractive polar compounds. We also provide the first detailed description of forager waggling and spinning behavior on poor and good food sources. Waggling may be a method of dispersing anal droplets and spinning may help foragers learn local landmarks.

Comparative study in stingless bees (Meliponini) demonstrates that nest entrance size predicts traffic and defensivity

Stingless bees (Meliponini) construct their own species‐specific nest entrance. The size of this entrance is under conflicting selective pressures. Smaller entrances are easier to defend; however, a larger entrance accommodates heavier forager traffic. Using a comparative approach with 26 species of stingless bees, we show that species with greater foraging traffic have significantly larger entrances. Such a strong correlation between relative entrance area and traffic across the different species strongly suggests a trade‐off between traffic and security. Additionally, we report on a significant trend for higher forager traffic to be associated with more guards and for those guards to be more aggressive. Finally, we discuss the nest entrance of Partamona, known in Brazil as boca de sapo, or toad mouth, which has a wide outer entrance but a narrow inner entrance. This extraordinary design allows these bees to finesse the defensivity/traffic trade‐off.

Notas sobre a bionomia de Tetragonisca weyrauchi schwarz, 1943 (Apidae, MeliponinI)

No Brasil, a abelha sem ferrao, Tetragonisca weyrauchi tem sua distribuicao restrita a regiao Amazonica. Constroi ninhos aereos frequentemente em forquilhas inclinadas de arvores. Os ninhos, cilindroides e verticais, medem cerca de 60cm de circunferencia na parte mais larga e 35cm de altura. A cobertura e de uma pelicula fina e maleavel com diferentes consistencias. A maioria dos ninhos apresenta, na parte superior, um prolongamento com varias protuberâncias e aberturas, ou so aberturas, com diâmetros milimetricos variaveis ao longo do dia, denominado aqui de respiraculo. A morfologia do ninho, com a porta na parte inferior e o respiraculo na parte superior, parece estar bem adaptado ao ambiente tropical em que se encontra. As medias das temperaturas internas de um ninho habitado e outro vazio acompanharam as flutuacoes ambientais com alto valor de correlacao (r=0,98). Os resultados sugerem que a estrutura fisica do ninho seria responsavel por uma pequena parcela na retencao da energia calorifera. Se existe termorregulacao, ela deve ser mais evidente acima dos 33oC ambientais, temperatura onde ocorreu tendencia de estabilidade. A grande quantidade de lamelas de cerume ao redor dos favos de cria horizontais, o tamanho dos potes ovoides de alimento ao redor de 1-2 cm de altura, a porcentagem de agua no mel ao redor de 27.6%, o aspecto do tubo de entrada com pequenos orificios, os valores de temperatura em que ocorre a abertura desse tubo pela manha, entre 21-23oC, e as coletas de nectar, predominantemente em Myrtacea, fazem com que seja atribuida grande semelhanca fisica e comportamental entre T.weyrauchi e T. angustula. Os ninhos se adaptam bem em colonias tipo Paulo Nogueira-Neto. Sao abelhas agressivas quando manuseadas. Estima-se que seus ninhos tenham uma populacao de 2000-3000 individuos.

Inbreeding and building up small populations of stingless bees (Hymenoptera, Apidae)

A study of the viability of small populations of Hymenoptera is a matter of importance to gain a better zoological, ethological, genetical and ecological knowledge of these insects, and for conservation purposes, mainly because of the consequences to the survival of colonies of many species of bees, wasps, and ants. Based on the Whiting (1943) principle, Kerr & Vencovski (1982) presented a hypothesis that states that viable populations of stingless bees (Meliponini) should have at least 40 colonies to survive. This number was later extended to 44 colonies by Kerr (1985). This would be necessary to avoid any substantial amount of homozygosis in the pair of chromosomic sexual loci, by keeping at least six different sexual gene alleles in a reproductive population. In most cases this would prevent the production of useless diploid males. However, several facts weigh against considering this as a general rule. From 1990 to 2001, 287 colony divisions were made, starting with 28 foundation colonies, in the inbreeding and population experiments with the Meliponini reported here. These experiments constitute the most extensive and longest scientific research ever made with Meliponini bees. In ten different experiments presented here, seven species (one with two subspecies) of Meliponini bees were inbred in five localities inside their wide-reaching native habitats, and in two localities far away from these habitats. This was done for several years. On the whole, the number of colonies increased and the loss of colonies over the years was small. In two of these experiments, although these populations were far (1,000 km and 1,200 km) from their native habitat, their foundation colonies were multiplied successfuly. It was possible to build up seven strong and three expanding medium populations, starting with one, two, three or even five colonies. However, in six other cases examined here, the Whiting (1943) principle and the hypothesis of Kerr & Vencovski (1982) and Kerr (1985), possibly hold up. In two other cases, the results are still unclear. Outside native habitats, most inbreeding experiments failed, possibly because of conditions that cause ecological stress. Although much more data are still needed, a new working hypothesis on the molecular level was presented to explain the results of the experiments described here. In the absence of any considerable stress, and in the eventuality of a good nutritive situation, even individual bees that are homozygous in the pair of chromosomic sexual locus would produce a sufficient amount of a sex determining substance. Therefore, the female genes of all the diploid individuals of a colony, both homozygous and heterozygous, would be activated. However, situations of considerable stress would cause a poor physiological and nutritive condition. This, together with homozygosis in the pair of chromosomic sexual locus, would lead to a smaller production of the sex determining substance. When this happens in the diploid homozygous individuals of a colony, in relation to sex, only male genes are activated. As a result, all such homozygous diploid bees of the colony become useless males. However, when there is a heterozygous situation in the chromosomic sexual locus of all bees of a colony, all diploid individuals would produce a high amount of the sex determining substance. Consequently, all diploid individuals of such a colony would become females (queens and workers). Stresses, including ecological stress, as well as the nutritive condition and the genetic situation in the chromosomic sexual loci, will have a key influence in the life and behavior of the Meliponini, including sex determination. In relation to genetic factors, hybrid vigour may often cause a greater production of biological substances. This may be due to the presence of a greater number of copies of allelic genes when there is heterozygosis. This is a hypothesis requiring further research. However, in the experiments presented here, this hypothesis seems to apply well to the production of a sex determining substance in bees (Apoidea) and other Hymenoptera.

Bourgeois Behavior and Freeloading in the Colonial Orb Web Spider Parawixia bistriata (Araneae, Araneidae)

Spiders of the tropical American colonial orb weaver Parawixia bistriata form a communal bivouac in daytime. At sunset, they leave the bivouac and construct individual, defended webs within a large, communally built scaffolding of permanent, thick silk lines between trees and bushes. Once spiders started building a web, they repelled other spiders walking on nearby scaffolding with a “bounce” behavior. In nearly all cases (93%), this resulted in the intruder leaving without a fight, akin to the “bourgeois strategy,” in which residents win and intruders retreat without escalated contests. However, a few spiders (6.5%) did not build a web due to lack of available space. Webless spiders were less likely to leave when bounced (only 42% left) and instead attempted to “freeload,” awaiting the capture of prey items in nearby webs. Our simple model shows that webless spiders should change their strategy from bourgeois to freeloading satellite as potential web sites become increasingly occupied.