Ecologia floral de duas especies invasoras de Ipomoea (convolvulaceae)

AUTOR(ES)
DATA DE PUBLICAÇÃO

1997

RESUMO

The reproductive system, floral biology, morphology and herbivory of Ipomoea cairica and Ipomoea carnea ssp. fistulosa were studied in the city of Campinas, São Paulo state, Brazil from July 1995 to July 1996. Ipomoea cairica is a herbaceous weed with long climbing shoots, having sexual and vegetative reproduction. The flower are odourless, tubular, with lilac limb and violet tube. Ipomoea carnea ssp. fistulosa is a semi-aquatic herbaceous weed reproducting by seeds and stems. The flowers are odourless, tubular, with pink limb and purple tube. The anthese of both species is diurnal, and the flowers open at sunrise and fade around 2 p.m. The most frequent and effective pollinators of Ipomoea cairica are Anthophoridae (Melitoma segmentaria and Exomalopsis fulvopilosa) and Apidae (Eulaema nigrita and Apis mellifera) bees. Hesperiidae skippers (Lepidoptera) were frequent as nectar robbers or as occasional pollinators. Promiscuous pollination was a marked characteristc in this species. The pollinators of Ipomoea carnea ssp. fistulosa were two Anthophoridae bees; Melitoma segmentaria was the most frequent and effective pollinator followed by Cera tina (Crewella) gossypii. Other insects visiting obsePled were nectar robbers belowing to the Lepidoptera and Coleoptera. The extrafloral nectaries of Ipomoea carnea ssp. fistulosa were visited by ants, bees, flies and many others insects. Ipomoea cairica and Ipomoea carnea ssp. fistulosa are xenogamous, with about 80% and 60% of success in cross pollination, respectively. The populations of both species presented homomorphic, sporophytic self-incompatibility. About 15% of Ipomoea cairica flowers suffer some kind of injury (slits and holes), while none of Ipomoea carnea ssp. fistu/osa flowers was attacked. From July 1996 to December 1996 assays were made to test fresh flowers samples of both species for protection against of Spodoptera frugiperda (Lepidoptera: Noctuidae). Protection (resistence) was determined by relative amounts of consumed experimental and control material (consumption index 4 IC). In assays using fresh flowers samples (Experimental) versus Control (samples of Ricinus communis (Euphorbiaceae) leaves) only Ipomoea camea ssp. Fistulosa showed to be protected (IC=O, n=12). The gross, water and chlorophormic extracts of the flowers from the protected species were tested to verify chemical protection. The gross and water extracts of this species showed deterrent effect when applied in leaf samples of Ricinus communis at 0.1 g/50ul. diluition (reducing the IC in 26% and 31 % respectively). Ipomoea cairica was not protected by chemical resistence against herbivory. However it was not attacked during visitation by pollinators, by assuring the fruit production before the occurence of flower herbivory. Apparently, Ipomoea camea ssp. fistulosa avoids floral herbivory through chemical resistence, but fruit production could be affected by the attack of Chelimorpha informes (Chrysomelidae: Cassidinae) bettles on leaves and imature buds

ASSUNTO(S)

polinização erva daninha

ACESSO AO ARTIGO

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