Fenologia, sucesso reprodutivo e mirmecofilia de Epidendrum cinnabarinum (Salzm. ex Lindl) (Orchidaceae) em fragmento de floresta atlântica no nordeste do Brasil

Abstract

In Epidendrum L. nectar is the main reward offered to pollinators, however, some species may not offer. Extrafloral nectaries serve as food for ants that protect the plant against herbivory. In this sense, this study has as main objective to investigate the phenology, reproductive biology and reproductive success of Epidendrum cinnabarinum. The study was carried out in the Guaribas Biological Reserve (Rebio Guaribas), located in the rural zone between the municipalities of Mamanguape and Rio Tinto in the years of 2015, 2016, 2017 and 2018. With the marking of individuals to evaluate several parameters. The period of flowering and fruiting begins in the month of September, however the production of flowers extends until April, while the fruit period occurs until March. Rainfall exerts a positive influence on fruiting (r = -0.6094; p = 0.0026). The individuals present a pattern in anthesis and floral morphometry. It is a self-compatible species, however, it is unable to spontaneously produce fruit by requiring a pollinator to perform fecundation. The reproductive success of the population (N = 3431 flowers) was low (1.51%), there was no significant difference between fruits formed by self-pollination and cross fecundation (p = 0,8014), as well as for seed viability (p = 0 , 2105). Epidendrum cinnabarinum secretes nectar inside the cuniculum where the pollinator has access, but also secretes externally, at the base of the petiole of buds, flowers, fruits and the scars of the bracts attracting ants to their inflorescence. In contrast, these ants present defensive behavior, as observed when attacking Nasutitermes sp belonging to the Isoptera group, reducing the rate of herbivory, which in the population corresponded to only 2.6%. Energetic investment in nectar production in E. cinnabarinum is greater for defense than for pollination. Lepidoptera Phoebis sennae was the only visitor able to remove the polinia, but there was no deposition, since fruits were not formed after the visits.