Disturbance, Pollinator Predictability, and Pollination Success Among Costa Rican Cloud Forest Plants

Abstract

Abstract. Cloud forest at Monteverde, Costa Rica experiences frequent natural disturbance. To determine whether species interactions vary spatially due to physical heterogeneity produced by disturbance, we examined relationships between 22 plant species and 11 nectar-feeding bird species in 14 study plots distributed among three patch types: large landslide-like gaps (hand-cleared areas along a trail), small gaps (formed by recent treefalls), and understory of closed-canopy forest.Species we describe here flowered in two or three patch types. The aspects of pollination we examined varied little with patch type. Mean frequency of pollinator visits varied with patch type in a few plant species but not in most, and there was no significant trend across species. Pollen loads carried by 314 mist-netted hummingbirds did not vary significantly with patch type, either in total number of grains or number of species represented. Cumulative pollen loads that hummingbirds deposited on stigmas of two species of Acanthaceae (Razisea spicata and Hansteinia blepharorachis) did not vary consistently with patch type, except that Hansteinia flowers in treefall gaps received fewer heterospecific pollen grains than flowers in the other two patch types. Frequency of fruit set varied significantly with patch type in three of the four species examined, but the direction of variation in one of these was opposite to the direction of the other two. The absolute frequency with which flowers were pierced by nectar-robbing hummingbirds did not vary significantly with patch type, although the frequency of piercing relative to legitimate pollinator visits did increase in the large gaps. We attribute the latter result to aggregation of the hummingbird Eupherusa eximia, a chronic nectar robber, at dense clumps of longflowered plant species that occurred in large gaps. Only one feature we examined suggested that patch type might directly affect the nature of species interactions: in two different analyses, the level of variation in frequency of hummingbird visits to flowers dedined from large gaps to small gaps to forest.Results suggest that, unless the disturbance initiating a patch is unusually severe or widespread, interactions between the plants and hummingbirds examined are insensitive to patch type. Such species, existing in naturally dynamic forests throughout their recent evolutionary histories, presumably have become accommodated to frequent small-scale disturbance. Results also suggest that those habitat-related contrasts in plant reproductive traits and plant-pollinator interactions documented in other studies, which compare habitats initiated by anthropogenic disturbances with undisturbed patches, may be artifacts to some extent. Anthropogenically generated disturbance mosaics may promote the spread of species whose reproductive traits evolved under very different circumstances from mosaics generated by natural disturbances. ·

Polinização por beija-flores em uma área de caatinga no Município de Floresta, Pernambuco, Nordeste do Brasil

“…Morfologia e biologia floral -O predomínio de espécies com flores vermelhas e tubulosas (encontrado em todas as espécies) é característico de comunidades de plantas ornitófilas , 1996, Buzato et al 2000, Lopes 2002. A maioria das espécies ornitófilas no local de estudo (cerca de 75%) apresentou flores com corola curta (comprimento do tubo ≤ 25 mm) e foi visitada, principalmente, por beija-flores de bico curto (culmen externo < 25 mm sensu Feinsinger et al 1987), situação semelhante à observada por Linhart et al (1987), Feinsinger et al (1987) e Santos (2005. Dentre as cinco espécies de beija-flores registradas na comunidade estudada, Heliomaster squamosus e Phaethornis gounellei apresentam bicos longos (≥ 28 mm sensu Feinsinger et al 1987) e as demais, bicos curtos (< 25 mm), de maneira que o predomínio de espécies com corolas curtas permite acesso de néctar a todas as espécies.…”

Exploring the boundary between pollination syndromes: bats and hummingbirds as pollinators of Burmeistera cyclostigmata and B. tenuiflora (Campanulaceae)

“…However, pollination studies in Monteverde, Costa Rica, have placed the local Burmeistera (including B. tenuiflora and B. cyclostigmata) in the ornithophilous syndrome corresponding to the short-billed hummingbird guild Murray et al 1987;Stratton 1989). While Feinsinger et al (1987) suggested that B. cyclostigmata may also be bat-pollinated based on its strong odor, they considered hummingbirds to be legitimate pollinators of both B. tenuiflora and B. cyclostigmata.…”

Mixed Support for Spatial Heterogeneity in Species Interactions: Hummingbirds in a Tropical Disturbance Mosaic

“…In a year-long field study, we evaluated joint responses of consumers and the plants they pollinate to a natural disturbance mosaic in the tropics (see also Feinsinger et al 1987;Linhart et al 1987). We chose a particularly well studied consumer group (nectar-feeding birds) whose morphology, behavior, and population ecology are especially closely linked to their food resources and whose use of those resources is easily quantified.…”