Maria Rosângela Sigrist

Fenologia reprodutiva, polinização e reprodução de Dipteryx alata Vogel (Leguminosae-Papilionoideae) em Mato Grosso do Sul, Brasil

The reproductive biology of Dipteryx alata was studied from September/2004 through August/2006. Dipteryx alata is a tree that blooms during the rainy season (4-6 months) and fructification peak occurs in the dry season. There are annual variations in the intensity of flowering and fructification. The flowers are zygomorphic, papilionaceous, hermaphrodite, relatively small, odoriferous, diurnal and last up to 10 hours. The calyx has two petaloid lobules and the corolla is formed by the standard, wings and the petals of the keel. Pollen viability is 94.4%. The stigma is covered by a pelicule that prevents pollen adherence and limits the spontaneous self-pollination. Nectar is produced in a chamber, in small quantity (1.45 µL) and with concentration of 25%. Dipteryx alata has keel flowers and the mechanism of pollination is intermediate between the explosive and valvular types. This species is alogamous, has late acting self-incompatibility and high rate of abortion (ER = 0.45). The main pollinator is Xylocopa suspecta (16.6% of visits), which visits legitimately the flowers and presents trap lining behavior, that promotes pollen flow between plants. Although the visitation rate of Pseudaugochlora graminea (15.3%) and Apis mellifera (39.5%) bees are relatively high, they are not good pollinators (pollination efficiency = 3.5 and 0, respectively), because they generally did not accomplish movement between plants. Apis mellifera robbed nectar in 45.5% of visits. The increasing of seed production in natural populations of D. alata depends on the maintenance of effective pollinators (solitary bees), and it is recommended the management of A. mellifera.

Flora of Brazilian humid Chaco: composition and reproductive phenology

We present the floristic composition and reproductive phenological data for a remnant of Arborized Stepic Savanna, vegetation type of humid Chaco, Porto Murtinho, Mato Grosso do Sul State, Brazil. We recorded 87 species of 31 families; Leguminosae presented the highest richness (14 species), followed by Malvaceae (9), Cactaceae (7) and Asteraceae (7). The herbaceous layer is relevant in the seasonal studied community (53.5% of the species) and there is predominance of non-perennial species (hemicryptophytes and therophytes), which demonstrate the importance of underground structures or seed banks in the vegetation. The community has continual flowering and fruiting with highest intensity in the rainy season, the most favorable period for plant growth and reproduction. The predominance of autochoric species in relation to anemochoric and zoochoric ones suggests partial independence of seed/fruit dispersal agents. Zoochorous species predominated in the rainy season, whereas anemochorous and autochorous species were more representative in the dry season.

Phenology, reproductive biology and diversity of buzzing bees of sympatric Dichorisandra species (Commelinaceae): breeding system and performance of pollinators

This paper reports on phenology, breeding system and dependence on pollinators of two sympatric Dichorisandra species. Dichorisandra incurva is a chamaephyte with continuous growth and precocious flowering, whereas D. hexandra is a geophyte with seasonal growth and delayed flowering. Flowering and fruiting occur mainly in the wet season; thus moisture can be important for both species. Besides moisture, photoperiod seems also to be related to the flowering only of D. incurva. Flowers of both species are poricidal, oligandrous, zygomorphic and buzz-pollinated by Apidae and/or Halictidae bees. Dichorisandra incurva is self-compatible, while D. hexandra shows a late-acting self-incompatible system. Moreover, herkogamy and poricidal anthers prevent spontaneous self-pollination in D. incurva. Therefore, medium- to large-sized Apidae are the most suitable pollinators as they make regular contact with anthers and stigmas and are further known to perform trapline foraging. This behaviour is particularly important for D. hexandra where Halictidae are considered pollen robbers, thus wasting pollen which, consequently, causes low reproductive efficacy in this species. Nevertheless, bee diversity is probably advantageous for the reproductive success of both Dichorisandra species. While the efficiency of each bee species is not known, further studies will show whether additional benefits are gained from the maintenance of these interactions.

Diurnal anthophilous fauna in Brazilian Chaco vegetation: phenology and interaction with flora

Phenology is the basis for understanding the life cycle of plants or animals throughout the year. Thus, we surveyed diurnal anthophilous fauna on plant species in the Brazilian Chaco to determine (1) groups of floral visitors and occurrence; (2) richness and abundance of fauna in relation to flowering flora and meteorological variables; (3) groups of visitors that pollinate or thieving flora; (4) distribution of herbaceous and woody strata throughout the year of flowering; (5) variation in flowering as a whole community, in the context of abiotic factors; and (6) the predominant plant families and species. We sampled eight groups of floral visitors, totalling 105 sampled species and 644 specimens. The flies and bees were the richest groups, with bees forming the most abundant group. The phenology of the fauna and flora was not clustered and exhibited a continuous and bimodal flowering. The abundance and richness of floral visitors were positively related to the quantity of plant species and flowering, as well as rainfall. Herbaceous and woody strata are important for the maintenance of anthophilous fauna throughout the year. Plant species with the highest abundance and the longest flowering period presented the highest richness and/or abundance of floral visitors. The percentage of pollination was higher than that of resource theft. Bees and flies were the main groups of pollinators, whereas flies were the main thieves. The present survey is only a starting point for future studies on the networks of interactions between plants and their floral visitors in the Brazilian Chaco.

Phenology and pollination ecology of Prosopis rubriflora (Leguminosae, Mimosoideae), a species from the semi-arid Brazilian Chaco

Prosopis L. is particularly rich and important in the Chaco region where forest vegetation currently persists as fragments. Its species are very important for the conservation and management of Chaco vegetation, and understanding their phenology and reproductive biology is essential. Here, we studied the phenology and pollination biology of P. rubriflora Hassl. in the Brazilian Chaco compared to other species of the genus. Differing from other Prosopis species, P. rubriflora is evergreen, and most phenophases are nonseasonal and bimodal (except fruiting), with a continuous pattern. Prosopis rubriflora is andromonoecious, but only weakly, since plants produce relatively few staminate flowers. Flowers showed three floral stylar phenotypes: short, medium and long style. Short-style flowers are functionally staminate because the stigma is nonreceptive. To compensate for the small size of P. rubriflora red brush flowers, attraction is compressed and transferred to the spike, which functions as a collective pollination unit. This compression may favour self- and intraplant pollination, which may reduce and/or prevent the occurrence of protogyny and partial, i.e. temporal, herkogamy in hermaphrodite flowers. Prosopis rubriflora has generalist pollination, but differs from the other Prosopis species because it is also pollinated by hummingbird, most likely due to its “ornithophilous” characteristics. This species is the first of the genus recorded as pollinated by hummingbirds. Although the exotic bee Apis mellifera L. presents high frequency of visit, this bee is not effective pollinator, due to its foraging style that does not favour cross-pollen flow. Native insects and hummingbird species are main pollinators because they present trapline foraging.

Floral traits as potential indicators of pollination vs. theft

Floral visitation does not necessarily mean pollination, as several animals utilize floral resources without transferring pollen. Since pollinators and thieves can affect the reproduction, morphology and diversification of flowering plants, we here investigated if attributes of flowers and flowering of plant species collected in the central Brazilian vereda would predict the pollination (pollen seeking) or theft (pollen/nectar theft) during the visits. It was hypothesized that non specialized flowers would have a higher incidence of thievery, where as specialization, for example, the presence of large and medium flowers with long corolla, making it difficult to access nectar, would lead to increased pollination. As a result, four attributes were mainly associated with illegitimate visits, and in order of importance, they are size (small), quantity of flowers per plant (large), flowering time (< 10 months) and floral type (inconspicuous). The richest and most abundant visitor groups, including bees, flies and wasps, acted mainly as potential pollinators, while cockroaches, butterflies, beetles, ants and hemipterans acted as thieves. However, further studies are required to confirm that this pattern is repeated in other larger and more diverse communities, thus confirming the possible preference for floral thieves.