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Absence of pollinators and apomictic fruit production in an Atlantic rainforest population of Cymbopetalum brasiliense (Annonaceae)

Braun, Marcus, Dötterl, Stefan, Gottsberger, Gerhard
Plant systematics and evolution 2011 v.296 no.3-4 pp. 265-273
Annona, Coleoptera, Cymbopetalum, Lycaenidae, air temperature, apomixis, buds, field experimentation, flowering, flowers, fruit set, heat treatment, larvae, odors, pollinators, rain forests, self-pollination, trees
Breeding system and pollination biology of an isolated population of Cymbopetalum brasiliense (Annonaceae), a large-flowered understory tree, was studied during two consecutive flowering seasons in October/November 2007 and September/October 2008. Flowers were morphologically comparable to other Cymbopetalum species and generally to other Annonaceae taxa adapted to pollination by large beetles, such as Annona spp. Flowers were thermogenic and emitted a strong scent during the pistillate and staminate flowering phases. Heating of the floral chamber was most intense during the pistillate phase between 1800 and 1900 h (up to 6°C difference to air temperature). Floral scent consisted almost entirely of p-methylanisole. None of the 133 flowers examined during two seasons received any visitation by dynastid beetles or other potential pollinators. Lycaenid larvae (Oenomaus ortygnus) attacked buds and flowers in both flowering seasons and destroyed about 20% of all buds in the 2007 season. Fruit set was high (72% of nonpredated flowers in 2007), despite the absence of pollinators. Field experiments showed that agamospermic reproduction rather than self-pollination was most likely responsible for fruit production. The study reports a probable case of apomixis, which would be the first in the Annonaceae family.