Efeitos da degradação do habitat na biologia reprodutiva de Caryocar brasiliense (Caryocaraceae) no Norte de Minas Gerais

Abstract

Caryocar brasiliense is a tree species considered being of great environmental, social and economic importance, and its fruits generate employment and income for numerous families living in the Cerrado areas. Although cutting this species is prohibited in the State of Minas Gerais, its natural habitats undergo constant changes for the implantation of pastures, agriculture and forestry. This degradation of habitats can influence, among other aspects, the interactions between animals and plants, and may affect important ecosystem services such as pollination. The objective of this study was to test the hypotheses: i) there is a difference in the pollen deposition between the sampling areas, with a higher deposition in the preserved area; and ii) there is a difference in the quality of the fruits between the areas, being of better quality in the preserved area and producing more viable seeds. In total, 2.004 flowers (753 in the degraded area and 1.251 in the preserved area) were sampled in 54 individuals of C. brasiliense, grouped in four treatments to investigate the plant’s reproductive system. In general, fruit production was extremely low, which may be related to factors such as high energy expenditure in fruit production and low annual precipitation. The pollen deposition was higher in the preserved area but varied between individuals and, as expected, was higher in the nocturnal period, despite the large deposition of day time pollen. Larger deposition in the preserved area was expected, due to greater habitat heterogeneity, which provides more refuges and more food resources for species of pollinators. The high deposition of diurnal pollen evidences the importance of a generalist system of pollination, which favors the species in the absence of its main pollinators. 269 fruits were collected (140 in the degraded area and 129 in the preserved area). Fruits and seeds of the degraded area were heavier than in the preserved area, but the total number of seeds and the number of viable seeds per fruit did not differ between areas. It is possible that the absence of interspecific competition has favored the development of fruits and seeds in the degraded area. The deposition of individual pollen varied significantly, as well as the number of viable seeds, which may indicate a foraging preference of the pollinators in certain individuals of the C. brasiliense species.