Favio Gerardo Vossler

Floral resources foraged by Geotrigona argentina (Apidae, Meliponini) in the Argentine Dry Chaco forest

Abstract This study is the first contribution to knowledge of the relationships between Geotrigona argentina and the plants of the Argentine Dry Chaco forest. A total of 1260 g of honey (corresponding to 146 pots) and 763 g of pollen (63 pots) stored in four underground nests was studied. The honey pots from each nest were homogenised and the four honey samples were analysed by melissopalynological methods, whereas the pollen pots were studied individually. Both classical counts and counts affected by the volume of the pollen types were carried out. Pollen data were statistically analysed. Additional data on both protein and lipid content is also provided. A total of 39 pollen taxa were identified. Pollen collection was focused on a few pollen taxa: Prosopis, Castela coccinea, Maytenus and Capparis; these taxa, together with Ziziphus mistol and Pisonia zapallo, were also important nectar sources. The preliminary results show that pollen collection varied seasonally, being most diverse in the summer when G. argentina incorporates herbaceous plants into its diet. The pollen collection spectrum of G. argentina is similar to that of other Trigonina bees in that the main plant species collected are a few large shrubs or trees, whose flowering consists of small and clustered flowers. Pots with large amounts of monofloral loads with pollen from only a few species suggests an organised foraging behaviour that includes the recruitment of foragers, such as that observed in other eusocial bees.

Stingless Bees in Argentina

This contribution compiles current knowledge of stingless bees in Argentina. There are 33 species in 18 genera distributed in three areas. The highest diversity is found in the northeast, in the Paranaense forest, with 22 species, followed by the Yungas in the northwest, with ten species. The Chaco, a xeromorphic central region, has the lowest diversity, with eight species. The most species-rich genera are Melipona and Plebeia. The traditional knowledge of stingless bees in Argentina is reflected in the many and accurate names by which different species have been known by diverse ethnic groups, such as the Guarani, Guaycuru, Toba, Wichi, and Quichua people, as well as the criollos. Several species are harvested in the field, but mainly those of the genera Tetragonisca and Scaptotrigona are kept in rational hives. A review of the contributions on different aspects of the biology and ecology of meliponines in Argentina is presented. Further research is needed to elucidate the real number of species present in Argentina. Several aspects of the biology, multiplication and management of colonies, and handling of their products merit also further studies. A better knowledge of the fauna will help decide which species can be selected for meliponiculture in specific areas.

Flower visits, nesting and nest defence behaviour of stingless bees (Apidae: Meliponini): suitability of the bee species for meliponiculture in the Argentinean Chaco region

Four bionomical features are here described for the seven stingless bees that inhabit a new meliponine beekeeping area: the Argentinean Chaco region. The most commonly visited plants were of herbaceous habits, predominantly had flowers of white/creamy to yellowish colour, with small-sized flowers and were of moderate mass-flowering degree. Lestrimelitta chacoana was the only robber species. The most commonly found nesting substrate was large living tree trunks, and most nests were found at the base of the trunks. Sometimes, nesting substrates and floral resources were provided by the same woody plant. Cryptic small- to medium-sized cerumen tube-like unornamented nest entrances were the most commonly found. Nest defence included aggressive (Scaptotrigona jujuyensis) and docile behaviour; the latter was classified into timid and non-timid. A key to identify the Meliponini fauna of this region is provided. The regional pattern of bionomical features seems to be associated with subtropical climate conditions. The majority of these bee species are suitable for Meliponiculture in the Chaco region.

Small pollen grain volumes and sizes dominate the diet composition of three South American subtropical stingless bees

Abstract The pollen preferences of three Meliponini species (Geotrigona argentina, Scaptotrigona jujuyensis and Tetragonisca fiebrigi) were studied in the Chaco forest of South America. Surprisingly, a large number of pollen types with small volumes and size were found in pollen masses stored in the 18 nests studied. Small pollen grains are commonly found in small flowers with short pistils, a flower morphology adapted to the pollination by these small- to medium-sized bees. The prevalence of grains with small volumes may be due to the preference of Meliponini bees for small flowers with short pistils, supporting a previously suggested hypothesis of diffuse co-evolution between mass-flowering trees and these tiny bees in Neotropical habitats. However, the opportunistic foraging habit of these generalist bees would suggest that the large number of grains with small size is due to their greater availability in the Chaco forest nearby the nests. This study also provides measurements and descriptions of pollen cytoplasmic shapes as well as a new classification of pollen volumes based from measurements of the five pollen size categories using non-acetolyzed grains.

The oligolecty status of a specialist bee of South American Prosopis (Fabaceae) supported by pollen analysis and floral visitation methods

Despite the nest pollen provisions in Western Argentina are composed only of Prosopis, the fact that the ground-nesting bee Eremapis parvula visits several floral hosts suggested that it is a generalist bee species. In the South American Dry Chaco forest, seven nest aggregations of E. parvula were found during three different spring periods. From 34 to 73 species of floral hosts were recorded around each nest aggregation. However, all nest pollen samples were composed of Prosopis pollen alone, as previously found in nests from Western Argentina. Thus, pollen analysis proved that E. parvula is a specialist bee of Prosopis. The “monolecty” and “narrow oligolecty” pollen specialization categories cannot be differentiated using pollen analysis alone. For this reason, a complementary floral visitation method was used. As several Prosopis species have been reported in floral records, the narrow oligolecty category for E. parvula is supported here. Considering that this exomalopsine is a multivoltine bee, and that flowers of some of the more than seven Prosopis species are always available during spring, synchronization between them in rainy periods is highly probable. Thus, it is unlikely that E. parvula has to forage on alternative pollen hosts.

Are Stingless Bees a Broadly Polylectic Group? An Empirical Study of the Adjustments Required for an Improved Assessment of Pollen Diet in Bees

This research describes simple calculations for pollen diet studies to improve the understanding of bee natural history. The stingless bees (tribe Meliponini) have been classified as broadly polylectic as they utilize more than 10% of the pollen host species of the entire melittophilous flora at a site or more than 25% of the available plant families. However, when considering pollen types, it was not possible to classify three bee species in this manner. For this reason, different calculation adjustments on foraged and available items were applied. For the former, two threshold values (10% and 5%), to identify abundant and discard minor and contaminant pollen resources, were used. For each threshold value, the number of pollen types and the number of pollen species ascribed to each pollen type were calculated. For the available items, spatial and temporal adjustments were estimated. When these adjustments were applied, in some cases bees were identified at higher specialization categories; broad polylectic was recorded only in six cases for Melipona orbignyi and Tetragonisca fiebrigi. As previously suggested for the other categories, contaminant and minor pollen types should also be excluded in polylectic bees. The threshold values of 10% for species and 25% for families are too high to reach broad polylecty. In addition, no direct comparisons between pollen types and pollen species could be made when working with the palynological data. Thus, simple values were proposed to assess pollen diet of generalist bees: the maximum number of foraged items per nest (contaminants not considered) and the maximum percentage value of foraged versus available items (adjusted). These belong to a wider range of values that can be recognized as degrees of polylecty, allowing for a more precise identification.

Stingless Bees as Potential Pollinators in Agroecosystems in Argentina: Inferences from Pot-Pollen Studies in Natural Environments

Stingless bees have proven to be effective pollinators of many crops both in open-field and greenhouse conditions around the world. However, because their sensibility of both individuals and colonies to low temperatures, the subtropical and part of the temperate area of Argentina present favorable climate conditions for open-field pollination. A total of 65 crops that require or benefit from animal pollination (highly autogamous and allogamous, with entomophilous pollination) were found suitable for meliponine pollination in Argentina, but this should be corroborated by means of field studies. Spatial and temporal availability of flowers from crops and wild vegetation was also described. Recommendations of best practice management of beneficial vegetation for the maintenance of permanent stingless bee colonies are given. A case study on strawberry crops in the temperate area of Argentina was also analyzed. A high diversity of native meliponine species from many genera in northern Argentina is suitable for numerous trials on a large number of crops.