We review the pollination ecology of acacias worldwide, discussing (1) the rewards provided to flower visitors, (2) the temporal patterns of flowering and reward provision and (3) the taxonomic composition of flower visitor assemblages. The flowers of most acacias (including all members of the subgenus Phyllodineae) offer only pollen to flower visitors and floral nectar is limited to a minority of species in the subgenera Acacia and Aculeiferum. The most important pollinators of acacias are social and solitary bees, although other insects and nectar-feeding birds are important in specific cases. Acacias that secrete nectar attract far more species-rich assemblages of flower visitors, although many of these are probably not important as pollinators. Most acacias in the subgenus Phyllodineae have long-lived protogynous flowers, without clear daily patterns in reward provision and visitation. In contrast, most members of the other two subgenera have flowers that last for a single day, appear to be protandrous and have clear daily patterning in reward provision and visitation. The generality of these patterns should not be assumed until the pollination ecology of many more phyllodinous acacias has been studied, particularly in arid environments. The accessibility of the floral rewards in acacia flowers makes them important examples of two general issues in plant communities—the partitioning of shared pollinators and the evolution of floral ant repellents. SBogy as G. N.

https://pure.royalholloway.ac.uk/portal/files/4375516/stone_20etal_202003_1_.pdf

Pollination ecology of acacias (Fabaceae, Mimosoideae)

Pollination biology and breeding system of Acacia senegal

Some of the published work on the reproductive biology of acacias is reviewed. The material selected refers to a few members of each of the three subgenera: Acacia, Aculieferum and Phyllodineae. Particular reference is made to anatomy, floral development and pollen–stigma interactions. Factors relevant to reproduction, including pollinators, self-incompatibility and fruit set are discussed.

Review of pollen–pistil interactions and their relevance to the reproductive biology of Acacia

Detailed descriptions, habitat preferences, geographic range, and representative specimens are given for the 13 native and two introduced taxa of Acacia subgenus Acacia (approximately the same as Acacia series Gummiferae) that are found in the South American flora. Some of these taxa are wide ranging. Acacia macracantha, A. tortuosa, and A. farnesiana are extremely common in northern South America, whereas A. caven and A. aroma occur throughout much of the southern half of the continent. The remaining species have restricted ranges, being found in relatively small areas. Principal components analysis (PCA) of vegetative and floral features shows that these species form discrete groups in plots of the first three principal components. From these data, most of the species were found to be relatively homogeneous, as indicated by the tight clusters formed in the PCA plots. In contrast, A. macracantha, a species ranging from Florida, south through the Caribbean, into South America, and in Mexico, is h...

Taxonomic Revision of South American Species of the Genus Acacia Subgenus Acacia (Fabaceae: Mimosoideae)

Acacia aroma and A. macracantha are closely related species that inhabit northern and central Argentina. The reproductive barriers between them seem to be weak. They exhibit low genetic differentiation, high levels of interspecific gene flow, and extensive areas of sympatry. Isoenzymatic approaches were used to evaluate the population structure and mating system parameters in natural Argentine populations of A. aroma and A. macracantha and to provide new tools for the analysis of relationships between these two species. All studied populations had high levels of genetic variability and no significant departures from Hardy-Weinberg expectations, but the two species did not differ from each other. Most variability occured within populations. Mating system analysis showed high levels of outcrossing, no biparental inbreeding, and a high probability that individuals within progeny arrays are full rather than half sibs. In all A. aroma and A. macracantha populations, polymorphic loci had the same allelic variants, and no geographic or genetic isolation between species was found. The results favor the hypothesis that these two entities represent a single polymorphic species rather than two distinct species.

Jose Luis Baranelli

Papers

Reproductive biology in Acacia caven (Mol.) Mol. (Leguminosae) in the central region of Argentina

Regular articleReproductive biology inAcacia caven(Mol.) Mol. (Leguminosae) in the central region of Argentina