Pocos estudios han considerado la dinámica de poblaciones de abejas en bosques o hábitats no alterados por el hombre. La presencia de abejas silvestres Africanizadas de Apis mellifera (Apidae) fue estudiado por 10-17 años en áreas previamente sin esta especie. Aquí presento e interpreto resultados de tres bosques neotropicales: Guyana Francesa, Panamá y Yucatán, México (5° a 19° N. latitud). La abeja Africanizada exótica no produjo efecto negativo en las abejas nativas, incluyendo especies altamente sociales y solitarias. Diferencias mayores a través del tiempo fueron encontradas en la abundancia de las abejas de miel en flores cerca de hábitat con mayor grado de disturbio, comparado con el bosque espeso. Al nivel poblacional, muestreado en bloques de nidos trampa, en flores o con trampas ultravioletas de insectos, no hubo disminución pronta de abejas, y sí hubo una población relativamente estable o sinusoidal. Sin embargo, las abejas nativas cambiaron su hora de buscar provisiones o su selección de especies florales. Una conclusión principal es que esta competencia por los recursos es ‘silenciosa';, en las áreas florísticamente ricas estudiadas, porque las mismas abejas compensan con su comportamiento. Otros factores rigen sus poblaciones.

Very little effort has been made to investigate bee population dynamics among intact wilderness areas. The presence of newly-arrived feral Africanized honey bee (AHB), Apis mellifera (Apidae), populations was studied for 10-17 years in areas previously with few or no escaped European apiary honey bees. Here I describe and interpret the major results from studies in three neotropical forests: French Guiana, Panama and Yucatan, Mexico (5° to 19° N. latitude). The exotic Africanized honey bees did not produce a negative effect on native bees, including species that were solitary or highly eusocial. Major differences over time were found in honey bee abundance on flowers near habitat experiencing the greatest degree of disturbance, compared to deep forest areas. At the population level, sampled at nest blocks, or at flower patches, or at light traps, there was no sudden decline in bees after AHB arrival, and relatively steady or sinusoidal population dynamics. However, the native bees shifted their foraging time or floral species. A principal conclusion is that such competition is silent, in floristically rich habitats, because bees compensate behaviorally for competition. Other factors limit their populations.

We describe and illustrate three new species from Central America and northern South America, present descriptions for previously unknown males and queens, and explore the internal phylogeny of Oxytrigona. Oxytrigona chocoana sp. nov., the sister species of O. daemoniaca, is from the Chocó biogeographic region; O. huaoranii sp. nov., and O. isthmina sp. nov., from the Eastern Andes of Ecuador and Darién (Panamá), are much smaller than their sister species, O. mellicolor. Oxytrigona huaoranii exhibits unusual characters including a short fore femur with carinate inferior margin, and striated basal propodeum. The male of O. isthmina primarily differs from O. mellicolor in having genitalia with an apically enlarged and strongly bent gonostylus. We also described the males of O. daemoniaca and O. mediorufa, and the male and queen of O. mellicolor. The taxonomic status O. mediorufa is revised; as here understood, this species is distributed only from Mexico to El Salvador. We obtained a single tree for Oxytrigona in a cladistic analysis of 18 morphological and five body coloration characters, which did not support the monophyly of the mulfordi and tataira groups. We also found variation in the gradular and distal margin shapes of the worker sixth sternum, which were useful in the taxonomic analysis. Such characters have not yet been used in the systematics of Meliponini, and we hope to draw more attention to and encourage future phylogenetic studies using these characters. We also present an identification key for the species.

Describimos e ilustramos tres especies nuevas de Oxytrigona de Centroamérica y norte de Suramérica, presentamos descripciones de machos y reinas previamente desconocidos, y exploramos la filogenia interna del género. Oxytrigona chocoana sp. nov., del Chocó biogeográfico, es la especie hermana de O. daemoniaca; O. huaoranii sp. nov. y O. isthmina sp. nov., del oriente de los Andes ecuatorianos y del Darién panameño, son mucho más pequeñas que su especie hermana, O. mellicolor. Oxytrigona huaoranii presenta caracteres inusuales tales como el fémur anterior corto, con el margen inferior fuertemente carenado, y el área basal del propódeo estriada. El macho de O. isthmina se diferencia principalmente de O. mellicolor por el gonostilo de la genitalia mucho más curvo y ensanchado apicalmente. También describimos los machos de O. daemoniaca y O. mediorufa, y el macho y la reina de O. mellicolor. El estatus taxonómico de O. mediorufa es revisado; según como la entendemos en este trabajo, esta especie se encuentra únicamente desde México hasta El Salvador. Un solo árbol fue obtenido para las especies de Oxytrigona, a partir del análisis cladístico de 18 caracteres morfológicos y cinco de coloración del cuerpo, el cual no apoya la monofilia de los grupos mulfordi y tataira. Las variaciones encontradas en la forma del grádulo y del margen distal del sexto esterno de la obrera, fueron útiles en el análisis taxonómico. Estos caracteres no han sido usados en la sistemática de Meliponini, y esperamos llamar la atención y promover su uso en futuros análisis filogenéticos. También presentamos una clave para la identificación de las especies.

Resumo A termodinâmica em 10 ninhos de Molipona rufiventris paraensis e Melipona seminigra merrillae foi registrada através de sensores termoelétricos. Padrões similares foram encontrados para ambas as espécies. Aparentemente não ocorre homeostasis, já que as temperaturas internas registradas da câmara de cría, dos potes de armazenamento de mel e de pólen e a do espaço da cavidade do ninho todos acompanhavam as flutuações da temperatura do meio ambiente. No entanto, as temperaturas registradas no ninho foram consideravelmente mais altas que as do meio ambiente em todas as porções do mesmo fazendo exceção a extremidade superior das colmeias verticais. Perto da cría as flutuações de temperatura acompanhavam as flutuações extranidais (do meio ambiente) com uma defasagem de 1 a 2 horas. A temperatura torácica das operárias pousadas nos favos foi perto de 34°C e a média da cría entre 31° e 32°C. O invólucro ao redor da cría retínha uma porção da radiação térmica dos imaturos e das operárias pousadas entre os favos e a temperatura da cría foi de 2 a 3°C mais alta do que a temperatura do ninho imediatamente fora do invólucro. A câmara de cría continha de 2.000 a 6.000 imaturos e a população de adultos foi menor do que 1.000. A cría do ninho atua como uma fonte térmica na base do ninho dissipando calor para a câmara criando um gradiente térmico. As abelhas imaturas parecem acrescentar mais energia térmica para o ninho.

SUMMARY Thermodynamics within 10 nests of Melipona rufiventris and M. seminigra were recorded during 48 horurs with thermocouple probes. Strikingly similar patterns were found for both species. Homeostasis did not occur; temperatures within the brood area, honey and pollen stored in pots and nest cavity space all followed ambient temperature fluctuations. Nest temperatures were consistently higher than ambient in all portions of the nest except the upper extremith of vertically elongate hives. Near the brood, temperature fluctuations were damped and displayed a time lag of one to two hours in following ambient temperature. The thoracic temperature of resting worker bees was near 34°C, and the average brood temperature was 31 — 32°. The involucrum surrounding the brood retained a portion of radiated heat from immatures and workers resting between combs, and brood temperature was two to three degrees higher than internal nest temperature immediately outside the involucrum. The brood chamber, the largest nest structure, contained from 2000 to 6000 immatures, and adult bee populations were less than 1000. The brood nest acts as a heat source at the base of the nest and dissipates heat upwards, creating a thermal gradient. Immature bees appear to supply most of the heat for the nest, and excess heat is shunted by fanning workers through the nest entrance, usually connected to the brood area. There is no evidence of evaporative cooling from water brought into the nest in these or other species of Meliponinae.