Biologia reprodutiva de Canistrum aurantiacume. Morren (Bromeliaceae) em remanescente da floresta Atlântica, Nordeste do Brasil

Abstract

Canistrum aurantiacum, a shade-tolerant species, is either an epiphyte or a terrestrial plant, endemic of the coastal Atlantic forest understory from Pernambuco and Alagoas. The species forms dense terrestrial populations, flowering from November to mid-February with the peak of flowering in the last half of January, when 12 flowers per plant may open during one day. The flowers are tubular and vary from 4-5 cm in length within the same inflorescence. The flowers begin to open from the centre of the inflorescence and progress towards the periphery. C. aurantiacum is an ornithophilous species, whose syndrome is characterised by odourless flowers, vivid-red involucral and scape bracts, and golden-yellow corolla. Nectar volume varies from 22,6 to 40,5 ml, with concentration of 26-33 %. Anthesis begins at dawn, around 5:20 a.m. and the flowers close around 4:00 p.m. Pollen and stigma are functional during the whole anthesis. Hummingbirds Chlorostilbon aureoventris and Thalurania watertonii (Trochilinae), Glaucis hirsuta, Phaethornis pretrei and P. ruber (Phaethornitinae) visited the flowers. The last one could be considered as the main pollinator, and was seen at regular intervals of 10 to 30 minutes, typical of the trap-lining visiting pattern. C. aurantiacum is a self-compatible species, nevertheless it produces low number of seeds per fruit in self-pollination treatments compared to the natural pollinations promoted by hummingbirds. Pipra rubrocapilla (Pipridae) and Tangara faustuosa (Thraupinae) were observed dispersing the fruits of C. aurantiacum. Ornithophily predominates in the Bromeliaceae, and has been characterised as a parallel evolution mechanism between bromeliads and hummingbirds. Canistrum aurantiacum is a typical example of this close relationship.