RESUMO
The rainfall regime has a significant impact on the microclimate and mass emergence of the coffee berry borer, Hypothenemus hampei (Coleoptera: Curculionidae) (CBB). Little is known, however, about the shade tree-microclimate-CBB mass emergence interaction. The objective of the present study was to compare the effect of microclimate on the mass emergence of CBB in a full sun-exposed plot with a plot shaded by trees. The experiment was conducted on a Robusta coffee farm in southern Chiapas, Mexico. In each plot, 18 traps baited with an alcohol mixture were installed to capture flying females, collecting caught individuals every hour from 8:00 to 18:00 h. A meteorological station recorded several microclimatic variables on 13 weekly sampling dates from February to May 2022. Significantly more CBB females were captured in the shaded plot. The largest number of CBB captures was recorded between 14:00 and 16:00 h for the shade plot and between 15:00 and 17:00 h for the sun-exposed plot. The mass emergence of CBB showed a positive association with precipitation, dew point, and wind speed samples and a negative association with maximum air temperature, average relative humidity, ultraviolet radiation, wind speed, and equilibrium moisture content. Our observations show that the relationship between shade trees, microclimate, and mass emergence of CBB is complex and that its study helps us to gain deeper insight into CBB bioecology and advance control techniques against this important pest.
RESUMO
Stylosanthes viscosa is a common 'herb' in the tropical sand dunes of the Brazilian coast with clumped distribution in urban sand dunes of Salvador, BA. Its tiny keel flower with a very small amount of nectar hidden inside the corolla tube, a single open flower/inflorescence/day and the low floral density altogether should not be attractive to large bees. This should be true mainly upon the high-demanded energy for thermoregulation within the tropical sand dunes. Contrary to this expectation, most of the bee species sampled on S. viscosa flowers were medium to large sized bees and harvested nectar in legitimate visits by activating the keel's pollination mechanism of flowers. However, the keel was always inactivated after being visited by the enormous and frequent (78 percent) Xylocopa bees. All the flowers visited by these bees (including those with inactivated keels), and those experimentally protected from bee visiting produced fruits (100 percent). The specialized embolus mechanism of the anthers assures self-pollination. Because of this autonomous self-pollination and self-compatibility it was not possible to discriminate the relative importance of both facilitated self-pollination and cross-pollination by bees. Nevertheless, the large Xylocopa bees didn't limit self-pollination. Xylocopa cearensis was the most abundant bee (63 percent) and it visited several flowers (13.0 ± 4.27) in each flight route in the same clump, in spite of the low floral density therein (5 to 20 flowers.m-2). Flight distances between successive flowers varied between one and two meters (49 percent), and so they were higher than would be possible (15 to 70 cm) given the floral density in the clumps. The flight routes were directional, and most of shifting direction between successive flowers was below 90° with high frequency of small angles (<30°). This general pattern is explained by foraging optimization with adjustments to critical resource level thresholds. Paradoxically, floral biology and flowering pattern of S. viscosa should discourage the largest dune dweller bees, but this strategy works just temporarily. In this melittophilous species, the autonomous self-pollination (assured by the embolus) can be better explained by the automatic selection hypothesis rather than by reproductive assurance hypothesis, considering the availability of large bee pollinators in the tropical dunes.
Stylosanthes viscosa é uma herbácea comum nas dunas tropicais da costa brasileira, com distribuição agregada nas dunas urbanas de Salvador, BA. Suas flores de quilha diminutas, com uma pequena quantidade de néctar escondido no tubo da corola, a abertura de uma única flor/inflorescência/dia e a baixa densidade floral, juntos, não deveriam ser atrativos para as abelhas de grande porte. Isso deve ser verdadeiro, principalmente, sob a alta demanda energética para termorregulação em dunas tropicais. Ao contrário do esperado, a grande maioria das espécies de abelhas amostradas nas flores de S. viscosa tem tamanho médio a grande e coletou néctar em visitas legítimas, acionando o mecanismo de polinização da quilha. Entretanto, a quilha sempre ficava inutilizada após as visitas das grandes e frequentes (78 por cento) abelhas Xylocopa. Todas as flores visitadas por essas abelhas (inclusive aquelas com a quilha inutilizada) e as protegidas experimentalmente das visitas das abelhas produziram frutos regularmente (100 por cento). O mecanismo de êmbolo das anteras assegura a autopolinização. Como há autopolinização autônoma e o sistema é autocompatível ainda não foi possível discriminar a importância relativa da autopolinização facilitada e da polinização cruzada por abelhas. Entretanto, as grandes abelhas Xylocopa não limitam a autopolinização. Xylocopa cearensis foi a abelha mais abundante (63 por cento) e visitou várias flores (13,0 ± 4,27) em cada rota de vôo, numa mesma mancha, apesar da baixa densidade floral (5 a 20 flores.m-2). A distância de vôo entre flores sucessivas variou entre um e dois metros (49 por cento), acima do que seria possível (15 a 70 cm) dada a densidade floral nas manchas. As rotas de vôo foram direcionais, isto é, a maioria dos ângulos de mudança de direção entre flores sucessivas foram abaixo de 90°, com alta frequência de ângulos pequenos (<30°). Este padrão geral é explicado com a otimização de forrageio, com ajuste a limiares críticos de oferta de recursos. Paradoxalmente, a biologia floral e o padrão de florescimento de S. viscosa deveriam desestimular a visita dessas grandes abelhas, mas esta estratégia funciona apenas temporariamente. Nesta espécie melitófila, a autopolinização autônoma (assegurada pelo êmbolo) pode ser melhor explicada pela hipótese de seleção automática do que pela hipótese de segurança, considerando a disponibilidade de abelhas grandes como polinizadores nas dunas tropicais.