The most prominent pollination mode in neotropical Annonaceae is pollination by beetles. Flowers are protogynous and have fruity, spicy or unpleasant odors. The floral chambers, formed by the petals closing over the flower center, emit these specific odors which entice the beetles to enter the flowers. There, the beetles are sheltered from daylight and predators and encounter food (tissues and pollen) as well as opportunities for mating. The amount of food offered, the thickness of the petal tissue and the dimension of the flowers increases with size, number and voraciousness of the attracted beetles. Three main groups of beetle-pollinated Annonaceae can be distinguished. Two of them have relatively small floral chambers, exhibit diurnal and/or nocturnal anthesis and are visited and pollinated by relatively small beetles (Nitidulidae, Curculionidae, Chrysomelidae). Large flowers with a large pollination chamber and very thick petals are associated with nocturnally active, large and voracious dynastid scarab beetles, which are attracted by strong odors promoted principally by thermogenetic processes of the flowers during the time of the beetles' main activity. The dynastid beetle-pollinated species appear to have the most adapted and most specialized flower characteristics in the Annonaceae. Some small-flowered Annonaceae are pollinated by thrips and, for a few species, pollination by flies is suspected. Some genera, such as Guatteria, are uniform with respect to flower biology and seem to have adapted principally to nitidulids as pollinators. In contrast, the genus Annona, basically a group pollinated by dynastid beetles, is diversified with respect to flower morphology and pollination. The neotropical Annonaceae as a whole may have started as a group pollinated by sucking and polleneating Thysanoptera and non-destructive beetle groups. Species pollinated by such Thysanoptera and/or rove beetles (Staphylinidae) still show the laminar, plesiomorphic stamen type of Annonaceae with a tongue-shaped connective prolongation. The disc-like sclerified connective shield of the majority of Annonaceae is apparently a secondary and modified structure, especially prominent in the beetle-pollinated species. The densely aggregated stamens with their connective shield appear to be a kind of antipredator structure in Annonaceae adapted to pollination by beetles.

Ants (Hymenoptera: Formicidae) consume a broad spectrum of liquid food sources including nectar and honeydew, which play a key role in their diet especially in tropical forests. This study compares carbohydrates and amino acids from a representative spectrum of liquid sources used by ants in the canopy and understorey of a tropical rainforest in northern Queensland, Australia. Eighteen floral nectars, 16 extrafloral nectars, two wound sap and four homopteran honeydew sources were analysed using high performance liquid chromatography. Wounds comprised flower abscission scars on Normanbya normanbyi L. H. Bailey and bitemarks on Cardwellia sublimis F. Muell. where ants were actively involved in wounding. Discriminant analysis was performed to model differences between food sources in sugar and amino acid concentration and composition. All characteristics varied significantly among plant species. Honeydew contained a broader spectrum of sugars (including melezitose, raffinose, melibiose, lactose and maltose) than nectar (sucrose, glucose, fructose), but certain extrafloral nectars had similar amino acid profiles and, like honeydew sources, were often monopolized by ants. Most common amino acids across the sources were proline, alanine and threonine among 17 ␣ -amino acids identified. Interspecific variability concealed characteristic differences in sugar and amino acid parameters between nectar, honeydew and wound sap across all plants, but these types differed significantly when found on the same plant. Among all sources studied, only a few flower nectars were naturally not consumed by ants and they were significantly less attended than sugar controls in feeding trials. These nectars did not differ in sugars and amino acids from ant-attended flower nectars, suggesting the activity of repellents. Apart from these exceptions, variability in amino acids and carbohydrates is proposed to play a key role in ant preferences and nutrition.

The Annonaceae show a broader flower biological radiation than originally thought, with flowers being pollinated not only by beetles, but also by thrips, flies and even bees. The majority of species have hermaphroditic protogynous flowers. Species with white or yellowish‐white, small, delicate, day‐active flowers, may be pollinated either solely by thrips, or by thrips and small beetles (e.g., species of Bocageopsis, Oxandra, Xylopia). Several of these thrips‐pollinated species have stamens with an elongated, tongue‐like connective. Pollination by flies is not well documented for American species, notwithstanding it appears to be more common in Old World species, e.g., in the genus Pseuduvaria. The mitriform flowers exhale an unpleasant smell, produce nectar in purple‐colored petal glands and have a sapromyiophilous syndrome. Flies enter the flower center through large openings between the inner petals. Beetle‐pollinated Annonaceae have flowers with comparatively thick and, often, fleshy petals, which, during anthesis frequently form a pollination chamber with the petals inclining over the flower center. The stamens usually have peltate connective shields, probably a device for protection against voracious beetles. Some cantharophilous species have flowers which are day‐active while others are night‐active. When they are in their pistillate phase, the beetles are attracted by characteristic odor components. They enter the pollination chamber and usually remain in the interior of the flower until the flower has changed to its staminate phase, when pollen is shed and afterwards petals and stamens detach. Two lines of cantharophilous Annonaceae are recognizable on the basis of present knowledge. Species with smaller and more delicate flowers are pollinated by small beetles (Nitidulidae, Curculionidae, Chrysomelidae and Staphylinidae), whereas species with large, more robust flowers in the Neotropics are pollinated by large beetles of the family Scarabaeidae, subfamily Dynastinae. Some species of the cantharophilous Annonaceae, especially the large‐flowered ones, but also some species with smaller flowers, produce heat during anthesis (thermogenesis). Food bodies, developed on the adaxial surfaces or sides of the petals, provide unique nourishment possibilities for beetles when they stay inside the flowers during the pistillate phase. In the staminate stage of the flower, after pollen is shed, beetles also feed on pollen. Apparently, no dynastid‐flower relationship has evolved in Asia and Australia. Pollination by bees was discovered recently in Unonopsis guatterioides in Amazonia and Uvaria concava in North Queensland: the first by scent‐collecting euglossine males and the second by pollen‐collecting Meliponinae. The general trends in morphological/functional floral characteristics in the family are discussed in a presumptive phylogenetic context.

No abstract

No abstract

No abstract

No abstract

No abstract