Reproductive Biology of two Florida Pawpaws: Asimina obovata and A. pygmaea (Annonaceae)

Abstract

NORMAN, E. M. AND D. CLAYTON (Dept. Biology, Stetson University, DeLand, FL 32720). Reproductive biology of two Florida pawpaws: Asimina obovata and A. pygmaea (Annonaceae). Bull. Torrey Bot. Club 1 3:16-22. 1986.-Field observations and experiments in central Florida determined phenology, pollination, breeding system, and crossability of Asimina obovata (Willd.) Nash and A. pygmaea (Bartr.) Dunal. Both species are strongly protogynous and similar in floral morphology, but differ in color and scent. Their flowering periods overlap, but flowering in A. obovata begins at least two weeks before that of A. pygmaea. Pollinators include large beetles, Trichotinus rufobrunneus, T. lunulatus and Euphoria sepulchralis (Scarabaeidae), which are common to both plant species, and Typocerus zebra (Cerambycidae), which is limited to A. obovata. The beetles prefer flowers in the male phase and consume pollen and corrugated tissue of the inner petals. This tissue is high in carbohydrates with lesser amounts of lipids and proteins. Bagged flowers of A. obovata occasionally self-pollinate (4% in 1981) but no selfing occurred in A. pygmaea. In open-pollinated flowers of A. obovata, 16% set fruits in 1981 and 5.5% in 1982, while 32% set fruits in hand-pollinated flowers. Open-pollinated flowers of A. pygmaea yielded fruit-set of 8% in 1981, 8.2% in 1982, and 60% when hand-pollinated. Reciprocal crosses between the two taxa produced fruits in 16% of flowers when A. obovata was the seed parent and 30% when it was the pollen parent.