Biologia da polinização e biologia reprodutiva de Cnidoscolus urens e Crotalaria retusa: plantas exóticas presentes em áreas de dunas costeiras na Ilha do Maranhão, Brasil

Abstract

Exotic and invasive species are among the greatest threats to global biodiversity. In Brazil, these introductions are related to human activities, mainly to environmental degradation processes. In addition to this aspect, exotic species can present mechanisms that facilitate their establishment in the environment, such as sexual reproduction (pollination and fruit production) that has great relevance for the dispersion of the same by the invaded environment. The objective of this work was to identify the syndromes and guilds of floral visitors of two species of exotic plants present in the dunes, analyzing the most efficient pollination methods. The study was carried out in two populations of the exotic plants Cnidoscolus urens and Crotalaria retusa that are found in the dunes of Praia de Panaquatira, located in the municipality of São José de Ribamar, Maranhão, Brazil. Monthly collections, from 6am to 6pm, of all the floral visiting insects found in both species of exotic plants, were identified and incorporated into the Coleção do Laboratório de Estudos sobre Abelhas (LEACOL / UFMA). In total, 537 individuals, 32 species and 34 morphospecies were collected from four orders. The most frequent flower visitor groups in C. urens were butterflies (213 individuals) and sphingids (136 individuals), whereas in C. reusa the frequent and dominant group were bees (24 individuals). As an effective pollinator of Cnidoscolus urens, the Diptera Palpada vinetorum was identified and as a potential pollinator a Coleoptera species of the subfamily Bruchinae (Chrysomelidae), while for Crotalaria retusa the effective

pollinator was the Xylocopa frontalis bee. The two botanical species showed to be self- compatible and demonstrated that natural pollination in both was more efficient than

spontaneous self-pollination. As for the occurrence of reproductive phenophases, C. urens presented all its phases positively related to the rainy season. While C. retusa presented only the floral and floral bud phenophases associated with this period, this may possibly be related to the predation of flowers and fruits of this plant by larvae of Utetheisa sp. (Lepidoptera). Both plants present strategies of reproduction that confers them advantages in the invaded area, in front of this can infer that C. urens and C. retusa has managed a good adaptation in this ecosystem of coastal dunes, being this a worrying fact for the conservation of the native species, because in the long run these exotic plants may overlap or occupy the niche of native plants.