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Master Thesis

Distribution et reproduction de Dichaea pendula (Orchidaceae) le long d'un gradient altitudinal dans la Mata Atlântica de montagne

Abstract : Gradients of altitude translate into important environmental variations and in the distribution of plants and their ecological interactions. In the present work we study the distribution of an orchid population, Dichaea pendula (Aubl) Cogn. along a small gradient of altitude in montane coastline forest. Flowering and fruiting were analysed to evaluate the potential effects of plant-pollinator interactions on the distribution of the species along this altitude gradient, taking account that this species is pollinated by males of Euglossini bees which are constrained by altitude. Plant individuals were inventoried in the National Park of Serra dos ôrgâos, between 940 m and 1290 m. We used model selection using Akaike method to identify the variables influencing the distribution of the population along the altitude. In the area of study, Dichea pendula had a patchy distribution and its frequency decreased along the gradient, moreover, it did not occur above 1150 m. Increase of altitude had no effect on flowering but a negative effect on fruiting rate, and no plants bearing fruits were observed above 1060 m. Other study in the same site have found that the abundance of Euglossini decreases in higher altitudes, and these bees are not found above 1100 m. Those results suggest that rarefaction of pollinator bees along this altitude gradient affects reproduction of D. pendula. The presence of the species above 1100 m can be explained by dispersion of its seeds through anemochory and its growth capacity under the environmental conditions in higher altitudes. Patchy distribution of the individuals in the area suggests that seed dispersion is mainly close to the mother plant. Reproductive failure due to pollinator rarefaction seems to be a major limiting factor for the presence of D. pendula in higher altitudes.
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Master Thesis
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Submitted on : Friday, December 11, 2015 - 11:41:25 AM
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  • HAL Id : dumas-01241988, version 1



Baptiste Benoit-Lizon. Distribution et reproduction de Dichaea pendula (Orchidaceae) le long d'un gradient altitudinal dans la Mata Atlântica de montagne. Sciences agricoles. 2015. ⟨dumas-01241988⟩



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