Bee Pollination Syndrome Research Articles

Phylogeny, diversity, and distribution inExostema (Rubiaceae): Implications of morphological and molecular analyses

The neotropical genusExostema comprises 25 species of trees and shrubs, ranging in distribution from Bolivia to Mexico and throughout the West Indies, with most species endemic to the Greater Antilles. Infrageneric relationships and species-level patterns of evolution were investigated in phylogenetic analyses using morphological, molecular, and combined data sets. All data sets resolved three main species groups which correspond to the three sections recognized byMcDowell (1996). However, the analyses of ITS sequence data placed the two South American species basal to the three main clades. Otherwise, the morphological and molecular data are highly compatible, and produce a more robust yet consistent phylogeny in the combined data analysis. Morphological evolution inExostema involves many specializations for xeric habitats, reflecting repeated ecological shifts from moist forest to exposed, seasonally dry environments during the diversification of the genus. Both moth and bee pollination syndromes are found inExostema, and shifts in pollination ecology appear pivotal to the differentiation of the three sections. Biogeographically,Exostema likely originated in South America and migrated via Central America to the Greater Antilles, where the morphological diversification and speciation are most extensive.

Floral divergence and convergence in the genusPelargonium (Geraniaceae) in southern Africa: Ecological and evolutionary considerations

Based on field observations and a survey of the available literature, the functional and evolutionary significance of floral characters ofPelargonium is investigated in relation to a recent infrageneric re-classification. Most of the 208Pelargonium taxa (recognized as species, subspecies or varieties) involved show bee and long-proboscid hovering fly pollination syndromes (about 60% and 25%, respectively), only 7% of the taxa are pollinated by butterflies, some 2 to 4% by hawkmoths and presumably 1% by birds. The heterogeneity ofPelargonium in terms of structural blossom types and pollination syndromes indicates an independent and repeated evolution of convergent flower morphs in the genus and even in sections.

Pollination in Australian Orchids: a Critical-Assessment of the Literature 1882-1992

A century of pollination studies of Australian orchids is reviewed. Descriptions of pollination events and conclusions about pollination status are inadequate in many reports. In this review criteria for establishing 'confirmed', 'probable' and 'suggested' pollinator status are defined and recommended. When applied to 153 published pollination reports there are 24 terrestrial species with 'confirmed' pollinators and a further 47 species with 'probable' pollinators. The major syndromes confirmed are wasp pollination by pseudocopulation (15 species) and the bee pollination syndrome of food mimicry (5 species). Nectar and pollen reward systems operate in a small number of species. Eleven epiphytic species have 'confirmed' pollinators, and four have 'probable' pollinators. Thirteen of the fourteen confirmed reports of epiphyte pollination describe social or solitary bees, mainly of the genus Trigona, apparently attracted by floral display and intense fragrance, which may constitute a chemical reward system. Dendrobium is the main epiphytic genus with confirmed pollinators.

Pollination efficiency and effectiveness or bumble bees and hummingbirds visiting <i>Delphinium nelsonii</i>

Delphinium nelsonii Greene is a spring-flowering perennial of the Rocky Mountains of North America. Its blue flowers conform to a classical «bee pollination syndrome», but in western Colorado they are visited by hummingbirds (mostly in the first half of the flowering season) as well as bumble bee queens (mostly in the second half of the season). Experiments with potted plants showed that a bee deposits about 10 times as much pollen while visiting a flower as does a bird, and causes about la times as many seeds to be set. In contrast, bees and birds appear similar in the «quality» of pollen they deliver, e. g., in its outcrossing distance. At the level of entire pollinator populations, hummingbird visitation rates may be over 10 times as great as those or bumble bees, in part because birds visit flowers more quickly. Thus the two visitor classes should deliver similar pollen quantities overall, which is confirmed by similar pollen loads of flowers early and late in the season, and should contribute about equally to seed set, which is confirmed by several experiments and observations. Exact relative contributions probably depend on pollinator population sizes, which in the case of hummingbirds appear to have varied 2.5 fold across 14 years. The similar contributions or birds and bees lo seed set shows that individual pollination efficiency must be distinguished from population-level effectiveness. and that the «pollination syndrome» of a flower may not indicate present-day effectiveness of its visitors.

FLOWERING BEHAVIOR OF THE NEOTROPICAL GENUS ANTHURIUM (ARACEAE)

The genus Anthurium (Araceae) is one of the most taxonomically complex genera in the neotropics. Studies of living material have shown modes of behavior which probably have a direct influence on pollination biology and evolution. Separation of the sexes is generally accomplished by marked protogyny. Considerable differences also exist in the rate of development of flowers, the presence, source and amount of stigmatic nectar, as well as the method of pollen presentation. The genus exhibits an unusual pattern of staminal emergence. In all species studied, the lateral pair of stamens are first to emerge, usually one at a time, followed by the anterior, then the posterior stamens of the alternate pair. There are also differences in the degree of exsertion, the disposition with respect to the stigma, degree of retraction and changes in pollen color. Some species have stamens which are retracted completely after opening: others have stamens which scarcely emerge but instead force the pollen out in long ribbons. Important differences also exist in flower aromas with both fly and bee pollination syndromes exhibited. All of these aspects of flowering behavior are natural phenomena believed to be important in pollination biology.

Flowering Behavior of the Neotropical Genus Anthurium (Araceae)

The genus Anthurium (Araceae) is one of the most taxonomically complex genera in the neotropics. Studies of living material have shown modes of behavior which probably have a direct influence on pollination biology and evolution. Separation of the sexes is generally accomplished by marked protogyny. Considerable differences also exist in the rate of development of flowers, the presence, source and amount of stigmatic nectar, as well as the method of pollen presentation. The genus exhibits an unusual pattern of staminal emergence. In all species studied, the lateral pair of stamens are first to emerge, usually one at a time, followed by the anterior, then the posterior stamens of the alternate pair. There are also differences in the degree of exsertion, the disposition with respect to the stigma, degree of retraction and changes in pollen color. Some species have stamens which are retracted completely after opening: others have stamens which scarcely emerge but instead force the pollen out in long ribbons. Important differences also exist in flower aromas with both fly and bee pollination syndromes exhibited. All of these aspects of flowering behavior are natural phenomena believed to be important in pollination biology.