Floral resource partitioning between native bees and the introduced Africanized bee in the Brazilian Atlantic rain forest W Wilms, B Wiechers

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W Wilms, B Wiechers. Floral resource partitioning between native Melipona bees and the introduced Africanized in the Brazilian Atlantic rain forest. Apidologie, Springer Verlag, 1997, 28 (6), pp.339-355. ￿hal-00891466￿

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Floral resource partitioning between native Melipona bees and the introduced Africanized honey bee in the Brazilian Atlantic rain forest

W Wilms B Wiechers

1 Departamento de Ecologia Geral, Universidade de São Paulo, 05508-900 Sâo Paulo, SP, ; 2 Zoologisches Institut der Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany

(Received 4 April 1997; accepted 19 August 1997)

Summary — and nectar harvested by colonies of two species (Melipona bicolor and M quadrifasciata) and the Africanized honey bee (Apis mellifera) were monitored over a year in the Brazilian Atlantic rain forest. The spectrum of plants used for pollen by the Melipona species was rather restricted. Only five pollen types contributed more than 1% to the total harvest over the year. The most important plant families were and , which also provided most of the nectar. The Africanized honey bee mainly used plants of Myrtaceae, Asteraceae, Euphor- biaceae and Arecaceae for pollen and Cunoniaceae, Rubiaceae and Myrtaceae for nectar. Measures of trophic niche overlap indicate the importance of common resource utilization for all three species of eusocial bees. Niche overlap between Melipona bees and A mellifera was more evident for nectar than for pollen. However, the peak in pollen harvest by the colonies of stingless bees as revealed by the number of newly filled storage pots coincided with a low level of presumed competitive pressure of Africanized honey bees, which was calculated as a product of niche overlap and amount of resources harvested. This can be interpreted as indirect evidence of actual competition for food. stingless bees / Africanized honey bee / Brazilian Atlantic rain forest / pollen analysis / resource exploitation / trophic niche overlap

INTRODUCTION the similarly abundant Africanized honey bee (Wilms, 1996). Records of flower visits In the Atlantic rain forest of tropical Brazil, indicate a considerable trophic niche over- stingless bees are nowadays the most abun- lap between the various highly eusocial bee dant native flower visitors to forage with species in this location (Wilms et al, 1996).

* Correspondence and reprints Fax: (49) 7071 296950; e-mail: [email protected] However, the actual resource use of these Bee colonies bees can only be monitored by direct anal- ysis of the pollen and nectar carried by for- Two colonies per species of the stingless bees agers returning to their colony or stored Melipona bicolor Lepeletier and Melipona anthidioides and of the inside the nest. As yet such studies have quadrifasciata Lepeletier introduced Africanized honey bee (Apis mellif- rarely been carried out in Brazil, and then era L), all originating from natural nest sites in the Amazon lowland forest mainly (Absy (Melipona) or swarms (Apis) from the region, et al, 1980, 1984) and in semi-natural envi- were hived in Melipona boxes (Nogueira-Neto, ronments such as the campus of the Uni- 1970) and Langstroth boxes (Apis). In the versity of Sao Paulo (Kleinert-Giovannini Boracéia rain forest these species represent abun- and Imperatriz-Fonseca, 1987; Guibu et al, dant members of the bee community (Wilms et al, 1996). The colonies were placed at least 6 1988; Imperatriz-Fonseca et al, 1989; weeks prior to the start of the observations in Ramalho, The Atlantic rain forest, 1990). primary forest in a circle of 50 m in diameter, or Mata Atlântica, has been the subject of the entrances all pointing east. The Africanized only a short survey (Ramalho et al, 1989). colonies casted a few swarms. Filial nest foun- the of the dation by the Melipona colonies was not Regarding possible impact observed. Africanized honey bee on this unique and endangered ecosystem, it is of special inter- est to know the nutritional basis of this intro- Pollen and honey duced species in the Mata Atlântica and to sampling compare it with that of native euso- highly Pollen and were from March cial bees. In the honey sampled present study, experimental 1993 through March 1994. Foragers returning colonies of two indigenous Melipona species to the stingless bee colonies were captured and and of the Africanized honey bee were used. one pollen load per bee was collected. To raise All species are of similar worker body size. the efficiency of bee capture the entrance of a Colonies of each species were placed side by colony was closed for 5 min. The foragers then accumulated in front of the hive or moved on side in a primary forest. Pollen and nectar the box and pollen carrying bees could easily be flow were recorded over a year. The bees’ captured. This procedure was repeated every half use of resources was reconstructed from the an hour throughout the day. Different colonies data on pollen and nectar collected and were handled in turn. Pollen from Africanized allowed us to determine species- and colony- honey bees was sampled in parallel using pollen specific trophic niches and to discuss pos- traps with round-holed screens. Pollen sampling started after 0600 hours sible competition among species. just daybreak (around in summer and 0700 hours in winter) and lasted until dusk or beginning of bad weather. Depend- ing on pollen flow, this sampling was continued MATERIALS AND METHODS for up to 3 days and performed at least twice per month. In addition, pollen and honey were col- lected from built site monthly newly storage pots Study inside Melipona nests. Honey from the African- ized colonies was sampled in parallel by remov- The was at Boracéia study conducted Biologi- ing two newly built combs per hive containing cal a nature reserve of the Station, Zoological honey every month, and which were replaced by Museum of the University of São Paulo, situ- empty frames. ated 90 km east of the city of São Paulo in the Serra do Mar at about 850 m above sea level at 23°38’ S and 45°52’ W. The study area is cov- ered with primary Atlantic rain forest except for Pollen analysis a few patches of secondary growth and small man-made clearings. It is surrounded by a pro- Individual pollen loads collected from Melipona tected forest of more than 16000 ha. foragers and from pollen trap samples (Apis) were colour-sorted, and the resulting fractions of the daily harvest were weighed. Mixed sam- ples were obtained from the pollen contents of the storage pots. Slides for microscopic analysis were prepared according to Vorwohl (1977), but where pik is the relative amount of pollen type k of i and is the relative ethanol instead of propanol was used to wash in the harvest species phk the pollen. The pollen content of honey samples amount of pollen type k in the harvest of species h. Calculations are based on the total harvest of was assayed according to Louveaux et al ( 1970). For all preparations, unstained and the colonies of one species. If harvest of one was NO was not fuchsin-coloured glycerine gelatin was used in species to be compared scarce, an in the parallel. For determination, a reference collec- calculated (indicated by asterisk (*) tion of local pollen types collected from flow- respective figures). ers of 244 was angiosperm species, mainly trees, This index is a widely used measure in eco- established. Quantitative evaluation of mixed logical work. As it considers quantitative simi- was made 300 preparations by counting pollen larities in the use of particular food sources, it slide. grains per has an advantage over more simple niche overlap measures. NOp and NOn are used to indicate niche overlap regarding pollen or nectar harvest, respectively. Pollen weight and volume proportions

The relative importance of particular pollen types Forage competition in the pollen samples was estimated by calculat- or volume (VP) ing weight (WP) proportions. Regarding the possible impact of the African- of loads according to pollen Separation pollen ized bee on native bees, an index load colour and treatment of these frac- honey stingless separate of the potential competition by Africanized honey tions results, in in relative pro- theory, weight bees was calculated as: portions of the particular pollen types (Vorwohl, (PCAm) 1977). However, frequently more than one pollen type can be found in one pollen load colour frac- tion. In these cases, the relative volume propor- where NOAm-i is the niche overlap between the tion of a pollen type was estimated (Biesmeijer et Africanized honey bee and the Melipona al, 1992). The results, however, are given in rel- species i, and RAm is the amount of resources ative weight proportions assuming equal specific harvested by the Africanized honey bee. RAm weights of the different pollen types. Due to the was calculated in grams (per day and colony) for combination of weighing colour fractions and the pollen harvested and as a percentage for the estimating relative volume proportions the pos- honey stored in the new frames. Thus, PCAm is a sible error in this assumption is restricted to par- relative index expressing the potential competi- ticular colour fractions comprising more than tive load of the Africanized honey bee in terms of one pollen type. This procedure takes into shared food sources. account that biomass rather than volume of the pollen is of importance for bee nutrition. How- ever, a method that allows a direct estimate of RESULTS the biomass of pollen grains is not available. Pollen from storage pots characteristically forms a yellow mass. In this case, solely the volume proportions of the pollen types were calculated as Temporal pattern of pollen described above. and nectar harvest

In the rain forest of Boracéia pollen and nec- Trophic niche overlap tar were harvested throughout the year. In all four Melipona colonies, storage pots were built in seasonal The number of The overlap of trophic niches was calculated synchrony. according to Colwell and Futuyama (1971) as: newly filled storage pots with pollen was highest in November (figs 1 and 2), whereas resented the main pollen sources, resulting new nectar pots were most numerous in July in over 90% of the pollen pot contents by and December (fig 3). The honey bee volume. Although many of the pollen loads colonies showed a peak in pollen harvest in collected from returning foragers contained August and in nectar harvest in December Solanum pollen, these were detected only (fig 4). in minor proportions in the pollen pots. In pollen trap samples of the Africanized colonies, 53 pollen types were found, of Use of and sources pollen nectar which 16 contributed more than 1% to the total pollen harvest over the year (table I). In the pollen samples of the Melipona The main pollen sources by family with 10% colonies, 20-25 pollen types were found, or more representation were Myrtaceae, of which only five contributed more than Asteraceae, Euphorbiaceae and Arecaceae I % to the total harvest over the year (table I). (fig 5), which together comprised over 65% Myrtaceae and Melastomataceae (fig 5) rep- of the total pollen forage. The spectrum of important nectar sources Most of the pollen was derived from was more diverse than that of pollen in all mass-flowering trees, indicating the great three bee species (table I). However, in the attractiveness of these dominating sources of stingless bees the most important pollen forage. sources, Myrtaceae and Melastomataceae, also supplied most of the nectar (fig 5). In addition, about one third of the nectar was Annual schedule of major pollen collected from flowers of other taxa, espe- and nectar sources cially Asteraceae, Cunoniaceae and Rubi- aceae. The latter two families, in addition The annual pattern of sources of pollen and to Myrtaceae, were also the main nectar nectar was quite different for the Melipona sources for the Africanized honey bees, species and the Africanized honey bees which also used some of their main pollen (tables II and III). The stingless bee colonies plants for the collection of nectar. preferentially collected Myrtaceae and

Melastomataceae pollen of many different the most profitable resources. Nectar har- species flowering in sequence over the year. vest by the stingless bees was more diverse In contrast, the Africanized honey bees than that of pollen, but plants of families changed their main pollen sources practi- other than Myrtaceae and Melastomataceae cally every month. This indicates a contin- were important as nectar sources only for uous search by workers of this species for short periods.

niche Trophic overlap The annual patterns in NOp and NOn depended mainly on the flowering periods of Average NOp across the 1-year period Myrtaceae which provided much pollen and between the Melipona species calculated nectar. This Angiosperm family represented from the daily (pollen from worker bees) or 60 and 30% of the annual niche overlap monthly (pollen from storage pots) resource between the Melipona species and the harvest was 0.66 for pollen loads of return- Africanized honey bee for pollen and nectar ing foragers and 0.82 for pollen from storage harvest, respectively. Other important Between A and pots. mellifera Melipona sources shared by Africanized honey bees bees NOp was and 0.23 average 0.27 regard- and Melipona bees were species of the gen- M bicolor and M ing quadrifasciata, respec- era Miconia (about 10% of NOp and 15% tively. However, over the year, NOp of NOn), Machaerium, Bathysa and Wein- between the honey bee and Melipona mannia (each contributing about 10% of species varied from 0 to 0.76 (fig 6) indi- NOn). cating temporal specialization of resource collection and fluctuations across the year in the Nectar harvest potential competition. Potential niche was Aver- competition overlap generally larger. Africanized bees age NOn between M bicolor and M quadri- by honey fasciata was 0.68 and between these species and A mellifera 0.44 and 0.5. However, as It is remarkable that in the colonies of both the honey bees stored nectar or honey only Melipona species the peak in the number of during certain periods of the year on newly newly filled pots with pollen coincides with built combs (fig 4) the respective NOn could a low index of the potential competition by only be calculated for these particular Africanized honey bees (figs 1 and 2). Such months. concurrence was not observed in honey pots. DISCUSSION were collected with nets while visit- ing flowers, plants of the families Myrtaceae and Melastomataceae were less important Different foraging strategies and plants of the families Asteraceae, in native and introduced social bees? and Rubiaceae were more important as food sources for Melipona bees relative to the present results. Both Myr- Honey bees are opportunistic foragers that taceae and Melastomataceae almost always try to exploit the most prof- comprise many with a itable food resources (Visscher and Seeley, species conspicuous mass-flowering syndrome. in blossom are char- 1982). Evidently this strategy was also fol- Single plants acteristically visited by many bees, which lowed by our Africanized honey bee results in a of the resources. colonies in the Boracéia tropical rain for- rapid depletion As a consequence, flower visiting bees were est, as can be seen from their continuously often observed there for a few of sources. In only hours, changing spectrum pollen in the for 75 contrast to this diverse flower use mainly early morning; example, sharp by and 51% of all bees flowers of A mellifera, colonies of M bicolor and visiting Myr- taceae and M quadrifasciata concentrated their forag- Melastomataceae, respectively, were collected before 1000 hours and 95 ing activities on flowering plants of only and 92% before noon. In contrast, the num- two families, Myrtaceae and Melastomat- ber of bees collected on flowers of aceae. Similar preferences of Melipona bees Solanaceae and especially of Asteraceae were reported by Engel and Dingemans- and Rubiaceae is more distributed Bakels (1980), Sommeijer et al (1983), equally over the Members of these families Kleinert-Giovannini and Imperatriz-Fon- day. resources over a seca (1987), Guibu et al (1988) and Ramalho provided longer daytime, which enhanced the chances of et al (1989). Most of these data, however, collecting bees upon them. From our were not obtained in undisturbed ecosys- flower-visiting observations, this, in general, concerns the tems, and are not the result of long-term as well as the level field studies. Our Boracéia data show that in plant specimen family with different having dif- a neotropical primary rain forest, members species slightly ferent over the of the Angiosperm families Myrtaceae and flowering peaks day. Melastomataceae flower across almost the Palynological analysis of honey only has entire year. By coevolution the abundant limited value for determining the origin of Melipona bees may have acquired the cor- the nectar, since the amount of particular responding flower preferences. pollen types which ends up in honey is influ- enced by flower type, harvesting behavior of Foraging workers of honey bees and the the bee, etc. For Brazil, a comparative data Melipona bees could frequently be observed base of pollen types known to be normally the same of visiting flowering patches Myr- over- or the taceae trees and also and Mikania. underrepresented regarding Bathysa actual of the nectar has not been estab- Resource selection the bees was origin by stingless lished. In this regard Myrtaceae, whose therefore probably not grossly altered owing flowers provide very abundant and small to pressure caused the intro- competitive by are less as duced Africanized honey bee. pollen grains probably important nectar sources than is suggested by the pure In general, our analyses of the pollen and pollen spectra. However, as this affects the nectar harvests confirm the records of a honey of Melipona and of Apis, the calcu- 3-year survey of flower-visiting bees in the lations of trophic niche overlap between the Boracéia forest (Wilms et al, 1996). How- various species probably are not biased sig- ever, in the latter study, in which the bees nificantly. Are pollen loads or pollen stores be consumed directly after being brought better indicators of forage use? in. The true proportion of a particular pollen type in the pollen harvest probably lies Our technique of removing pollen from for- somewhere between that obtained by anal- agers returning to their colony gives a good yses of storage pot contents and that of record of the actual pollen influx and allows pollen loads removed from forager bees. us to calculate trophic niche overlap. How- Differences in the pollen spectra between ever, during periods of very intense foraging samples from storage pots and samples from activity it was not possible to collect pollen forager bees mainly concerned the plant loads quantitatively from all pollen carry- families Melastomataceae and Solanaceae bees. We did not extend time ing sampling in a reciprocal way. Neither family provided of hive as it the (closure entrance) hampers important pollen resources for honey bees. information flux between the bees inside For the calculations of trophic niche overlap and outside the colony. Therefore, and between Melipona bees and the Africanized because pollen income on particular days honey bee differences due to sampling was much influenced weather con- very by method of the pollen are therefore negligible. ditions, we think that permanently accumu- lating pollen in storage pots yields better quantitative results over the year. Is the Africanized honey bee The general preference of the Melipona competing with native social bees? bees for Myrtaceae and Melastomataceae was indicated by both methods of pollen It is surely true that harvest of Melipona as sampling. The percentage of Myrtaceae well as Apis colonies depends strongly on pollen was essentially the same for both flower abundance and therefore may be trig- methods. However, there was more pollen of gered by seasonal influences. However, Melastomataceae and less pollen of flowers can be found throughout the year Solanaceae in samples from storage pots and harvesting of eusocial bee colonies does than in samples taken from returning for- not stop during winter. When suitable food agers. These discrepancies could result from sources explored by Melipona as well as the mentioned difficulties in collecting all Apis foragers are available one can assume returning pollen-carrying bees in periods of that colonies of both species benefit, show- very intense foraging activity. As a conse- ing a positive correlation in resource har- quence, pollen of short lasting but mass- vest. However, intra- and interspecific com- flowering resources could have been under- petition between colonies of both species sampled by the method of taking pollen would prevent maximal exploitation of that from returning foragers, whereas pollen of resource by any colony. As bees of many longer lasting resources could have been highly eusocial species rely on mass-flow- oversampled. In addition to this methodi- ering trees (Wilms et al, 1996), which can be cal reason, Sommeijer and De Bruijn (1994) explored efficiently by recruitment of nest state that Melipona house bees have a very mates, the occurrence of short harvest peaks strong tendency to close storage pots. After in colony dynamics is a common feature a continuing strong pollen flow, they may (Roubik et al, 1986). A maximal resource subsequently eat the pollen of other types, harvest is, however, probably only possible that comes in after the earlier strong flow if competition is limited. Therefore, one has finished. As a consequence pollen that is could expect that a competitional impact of available for short periods and in smaller Africanized honey bees, rather than lead- quantities will hardly be stored, although ing to a general negative correlation, will over time large amounts of these types may be most evident in reducing or preventing harvest peaks in colonies of stingless bees. Boracéia. WW obtained financial support from This is what Roubik et al (1986) found in a the Landesgraduierten-Förderung Baden-Würt- 2-week experiment studying the influence of temberg and the Deutscher Akademischer Aus- tauschdienst (DAAD). honey bees on various colonies of stingless bees in Panama.

In our a small index of study potential Résumé — Partage des ressources flo- competition by Africanized honey bees does rales entre les abeilles mélipones indi- not automatically mean abundant food avail- gènes et l’abeille africanisée introduite, ability for the Melipona bees. In fact, in peri- dans la forêt ombrophile cotière du Bré- ods of low resource a small index supply, sil. Dans une zone protégée de la forêt result from low of the may foraging activity ombrophile cotière près de São Paulo, on a bees. On the other a honey hand, high PCAm prélevé sur une année des échantillons de suggests the flowering of many suitable food pollen et de miel dans deux colonies de plants, and therefore, an optimal condition Melipona bicolor et deux de M quadrifas- for resource collection for the Melipona ciata (abeilles sans aiguillon) et dans deux bees. However, the peak in the number of colonies d’abeilles africanisées, Apis mel- filled newly storage pots containing pollen lifera, et on a fait des analyses polliniques de in all colonies coincided with a Melipona ces échantillons. Des pelotes de pollen ont low index of The main influx PCAm. pollen été récoltées au moins deux fois par mois such times came from Melastomat- during i) sur des ouvrières capturées devant le trou aceae trees, which were not used very de vol (Melipona), ii) dans des trappes à intensely by the honey bees. Despite a poten- pollen (Apis). En outre des échantillons de tially good food supply, a comparable peak pollen et de miel ont été prélevés chaque in the number of pollen pots in periods with mois dans les pots de réserve nouvellement high indices of PCAm was not observed. On remplis des colonies de Melipona et dans the other we found that the hand, Melipona les nouveaux rayons des colonies d’Apis colonies were able to collect large quantities (dans deux cadrons suspendus le mois pré- of nectar in spite of high indices of PCAm. cédent). Therefore, competition by this intruder may Les échantillons ont été traités et les be more important in exploitation of pollen pré- réalisées selon Vor- rather than nectar resources. parations polliniques wohl (1977) et Louveaux et al (1970). Pour Our do not findings, although they prove les échantillons de pollen, on a estimé les a causal can nevertheless be correlation, pourcentages relatifs en poids et en volume interpreted as a result of competition. How- des types polliniques (Vorwohl, 1977; Bies- ever, the generality and strength of the meijer et al, 1992). Le recouvrement des assumed correlation between the negative niches alimentaires (NO) a été calculé occurrence of harvest peaks for pollen in d’après Colwell et Futuyama (1971). Pour colonies of stingless bees and the PCAm mesurer l’impact potentiel de l’abeille afri- index have to be future investi- proved by canisée on a défini un indice de compéti- gations. tion (PCAm), qui est le produit du recouvre- ment des niches et de la récolte globale des abeilles africanisées. ACKNOWLEDGEMENTS Dans la forêt ombrophile de Boracéia les colonies de ont récolté du We would like to thank Dr Vera L Imperatriz- mélipones pollen et du nectar tout au de l’année. La Fonseca, all the members of her group, and the long board of the Museu de Zoologia (USP) for sup- récolte de pollen (nombre de pots à pollen porting our work at the Estação Biológica de nouvellement remplis) a été maximale en novembre (figs 1 et 2), tandis que la récolte pots à pollen et 0,68 pour les échantillons de miel (nouveaux pots à miel) a présenté de miel) qu’entre les mélipones et l’abeille deux maximums, l’un en juillet et l’autre en mellifère (0,27 et 0,44 pour M bicolor, 0,23 décembre (fig 3). Août et décembre ont été et 0,5 pour M quadrifasciata, respective- les mois où les colonies d’abeilles africani- ment pour les échantillons de pollen et de sées ont engrangé le plus de pollen et de miel). Le recouvrement, en fonction de la miel, respectivement (fig 4). Dans les échan- saison, des niches alimentaires des méli- tillons de pollen et de miel des colonies de pones et de l’abeille africanisée dépend en Melipona, les Myrtacées et les Mélastoma- premier lieu des différentes périodes de flo- tacées ont dominé presque toute l’année raison des Myrtacées. Les plantes de cette (tableau II et III; fig 5); cela confirme les famille fournissent 60 et 30 % respective- études d’autres auteurs réalisées dans des ment de la récolte annuelle en pollen et en habitats principalement influencés par nectar. l’homme. L’abeille africanisée a utilisé un En ce qui concerne la concurrence pos- de nourricières large spectre plantes (tableau I), sible d’A mellifera, il est frappant de voir caractérisé un renouvellement par presque que, dans les colonies des deux espèces de mensuel des ressources principales (tableaux II mélipones, on trouve la plupart des nou- et Les différences entre les échantillons III). veaux pots à pollen à des périodes où des ouvrières et ceux issus des provenant l’indice est le plus bas (figs 1 et 2). à les faits sui- PCAm pots pollen s’expliquent par Cela peut être d’autant plus interprété vants : intense, toutes les i) par butinage comme un signe d’une concurrence réelle ouvrières rentrant à la colonie avec des de l’abeille mellifère qu’un indice PCAm ne être devant pelotes peuvent pas capturées élevé indique un bon potentiel de ressources le trou de vol, c’est dans ces pourquoi, pour les mélipones. Contrairement au pollen, les fleurissent en échantillons, plantes qui le nectar des colonies de mélipones est masse et sont peu longtemps sous-repré- engrangé en grandes quantités même lorsque sentées; ii) selon et De Sommeijer Bruijn l’indice PCAm est élevé (fig 3). La concur- les abeilles ont une forte (1994), Melipona rence alimentaire entre les abeilles africa- tendance à fermer les à pots pollen ; après nisées et les mélipones de la forêt ombro- une forte rentrée de il est pollen possible phile cotière du Brésil existe plus pour le soit traité sans que pollen rapporté pas- l’approvisionnement en pollen que pour ser les à si bien les par pots pollen, que pol- celui en nectar. lens qui ne sont disponibles que peu de temps et en petites quantités sont à peine Melipona / abeille africanisée / butinage / présents dans les pots à pollen. La quantité compétition alimentaire / niche trophique absolue du pollen prélevé sur les butineuses / recouvrement / forêt ombrophile / ne dépend pas seulement de l’offre polli- Brésil nique mais aussi des conditions météorolo- giques les jours où les prélèvements sont faits. Le nombre de pots à pollen nouvelle- Zusammenfassung — Aufteilung flora- ment remplis nous semble plus approprié ler Ressourcen zwischen Melipona-Bie- évaluer la de à pour quantité pollen rapporté nen und der Afrikanisierten Honigbiene la colonie. im Brasilianischen Küstenregenwald. In Le recouvrement des niches est plus einem Waldschutzgebiet des brasilianischen important pour les deux espèces de méli- Küstenregenwaldes bei Säo Paulo wurden pones entre elles (moyenne annuelle 0,66 über ein Jahr hinweg Pollen- und Honig- et 0,82 pour les échantillons de pollen pro- proben von jeweils zwei Völkern der Sta- venant respectivement des butineuses et des chellosen Bienen Melipona bicolor und M quadrifasciata sowie der Afrikanisierten Unterschiede zwischen den von Arbeiterin- Honigbiene (Apis mellifera) genommen und nen und aus Pollentöpfen gewonnenen Pro- pollenanalytisch untersucht. Pollenhöschen ben sind dadurch zu erklären, daß bei star- wurden mindestens zweimal pro Monat von kem Sammelflug nicht alle pollentragenden vor dem Flugloch abgefangenen Arbeite- Arbeiterinnen vor dem Flugloch abgefan- rinnen (Melipona) bzw in Pollenfallen (Apis) gen werden konnten; daher sind in diesen gesammelt. Zusätzlich wurden monatlich Proben nur kurzzeitig blühende, massen- von den Melipona-Völkern Pollen- und blütige Ressourcen offensichtlich unterre- Honigproben aus neu gefüllten Vorratstöp- präsentiert. Auch haben nach Sommeijer fen und von den Apis-Völkern Honig aus und De Bruijn (1994) Melipona Bienen eine neuen Waben (in zwei im Vormonat neu starke Tendenz, Pollentöpfe zu schließen. eingehängten Rähmchen) gewonnen. Die Nach einem starken Polleninflux ist es mög- Aufbereitung der Proben und die Herstel- lich, daß anschließend eingebrachter Pollen lung von Pollenpräparaten erfolgte nach ohne den Umweg über Pollentöpfe verar- Vorwohl (1977) und Louveaux et al (1970). beitet wird, so daß nur kurzzeitig und in Für Pollenproben wurden die relativen geringer Menge angebotener Pollen kaum Gewichts- bzw Volumenanteile der einzel- in Pollentöpfen gefunden werden kann. Die nen Pollentypen bestimmt (Vorwohl, 1977; absolute Menge des von den Sammelbie- Biesmeijer et al, 1992). Die Überschnei- nen abgenommenen war nicht nur dung der Nahrungsnischen (NO) wurde nach vom Pollenangebot, sondern auch von Wit- Colwell und Futuyama (1971) berechnet. terungseinflüssen an den einzelnen Unter- Als Maß für den potentiellen Konkurrenz- suchungstagen abhängig. Zur Abschätzung druck, der von der Afrikanisierten Honig- des quantitativen Polleneintrags erscheint biene ausgeht, wurde ein Index (PCAm) als uns daher die Anzahl neu gefüllter Pol- Produkt von Nischenüberschneidung und lentöpfe geeigneter. dem der Gesamteintrag Honigbienenvölker Die beiden Arten Stachelloser Bienen definiert. zeigten untereinander eine größere Im Regenwald von Boracéia wurden Pol- Nischenüberschneidung (im Jahresdurch- len und Nektar das ganze Jahr hindurch von schnitt 0,66 bzw. 0,82 für Pollenproben von den Völkern der eusozialen Bienen gesam- Sammelbienen und aus Vorratstöpfen und melt. Die Anzahl neugefüllter Vorratstöpfe 0,68 für Honigproben) als mit der Honig- mit Pollen war im November am höchsten biene (für Pollenproben 0,27 und 0,23 (Abb 1 und 2), wogegen neue Honigtöpfe bezüglich M bicolor und M quadrifasciata im Juli und Dezember am zahlreichsten und für Honigproben 0,44 und 0,5). Für das waren (Abb 3). Die Völker der Afrikani- zeitliche Muster der Nischenüberschnei- sierten Honigbiene brachten den meisten dung von Melipona- und Honigbienen Pollen im August und den meisten Nektar (Abb 6) waren in erster Linie die verschie- im Dezember ein (Abb 4). In den Pollen- denen Blühperioden von Myrtaceen ver- und Honigproben der Melipona-Völker antwortlich. Pflanzen dieser Familie mach- dominierten praktisch das ganze Jahr über ten 60% bzw 30% der jährlichen NO für Myrtaceen und Melastomataceen Pollen und Nektar aus. (Tab II, III; Abb 5), wodurch Untersuchun- Unter dem einer Kon- gen anderer Autoren in zumeist anthropo- Aspekt möglichen kurrenz von fiel daß in gen beeinflußten Habitaten bestätigt wer- Apis mellifera auf, den. Die Afrikanisierte Honigbiene nutzte den Völkern beider Melipona-Arten die mei- sten neuen in solchen Zeiten ein breiteres Spektrum an Nahrungspflan- Pollentöpfe für die ein zen (Tab I), wobei die Hauptressourcen gefunden wurden, niedriger nahezu jeden Monat wechselten (Tab II, III). PCAm-Index berechnet wurde (Abb 1 und 2). Dies kann umsomehr als Hinweis auf Imperatriz-Fonseca VL, Kleinert-Giovannini A, eine tatsächlich bestehende Konkurrenz der Ramalho M (1989) Pollen harvest by eusocial bees in a non-natural community in Brazil. J Trop Ecol Honigbiene interpretiert werden, als ein 5, 239-242 hoher PCAm-Index auch eine gute potentielle Kleinert-Giovannini A, Imperatriz-Fonseca VL (1987) Ressourcensituation für die Stachellosen Aspects of the trophic niche of Melipona marginata Bienen bedeutet. Im Gegensatz zu Pollen marginata Lepeletier (, Meliponinae). Api- 18, 69-100 wurde Nektar von den Stachellosen-Völ- dologie kern auch bei hohem in Louveaux J, Maurizio A, Vorwohl G (1970) Interna- PCAm-Index größe- tionale Kommission für Bienenbotanik der I.U.B.S. rer Menge eingebracht (Abb 3). Nahrungs- Methodik der Melissopalynologie. Apidologie 1, konkurrenz zwischen der Afrikanisierten 193-209 Honigbiene und den Stachellosen Bienen Nogueira-Neto P (1970) A Criação de Abelhas Indí- besteht im brasilianischen genas Sem Ferrão (Meliponinae). 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