Papel de aves e morcegos na germinação das sementes e remoção dos frutos de solanum granulosoleprosum (solanaceae)

Abstract

Fifty to 90% of the trees and shrubs depend on vertebrates to disperse their seeds in tropical regions, where zoochory is important for the regeneration of disturbed forested areas. In these areas, birds and bats are considered efficient seed dispersers in relation to the quantity and quality of seed dispersal. The aim of this work is to evaluate and contrast the roles of birds and bats in promoting the germination of seeds and fruit removal of Solanum granulosoleprosum (Solanaceae), a pioneer species typical of forest edges, in forest fragments located in south Brazil. The fruiting phenology was monitored, and the frugivores eating the fruits of S. granulosoleprosum were recorded during focal observations and with the aid of mist nets. Seeds ingested by birds and bats were contrasted with seeds extracted from mature fruits (control seeds) in germination trials carried out in laboratory under natural conditions. Fruits from five individuals were marked and monitored at dusk and dawn during a 30-day period to assess the fruit removal by birds and bats. Plants produce mature fruits from Autumn to Winter (April to August), with a peak in late Autumn. Thirteen bird species and fur bat species were recorded eating the fruits. Germination success were higher for bird- (40% of germinated seeds) than batingested seeds (16.7%) or control seeds (17.5%; n = 120 seeds for treatments and control). Similarly, the velocity of seed germination was higher for birds. Bat-ingested seeds did not differ from control seeds neither in germination success nor in the velocity of seed germination. Fungi infestation was noted in 41.7% of the batingested seeds, whereas only 6.7% of the bird-ingested and 1.7% of the control seeds were attacked by fungi which precluded germination. A total of 85% of the 667 marked fruits were removed, mainly by bats (n = 64.5%). The present work illustrates a case where birds and bats have contrasting effects upon seed dispersal: while birds are more efficient than bats in a qualitative way, enhancing the germination of seeds, the opposite is true in the quantitative side of efficiency framework, with bats removing a greater quantity of seeds than birds.