Clemens Schlindwein

Stamen movements in flowers ofOpuntia (Cactaceae) favour oligolectic pollinators

Opuntia brunneogemmia andO. viridirubra occur sympatrically in the Serra do Sudeste, Rio Grande do Sul, Brazil. Their flowers have 450–600 thigmonastic stamens and provide large amounts of pollen and nectar for bees. Bees of 41 species were registered at the flowers ofO. brunneogemmia and 30 at the flowers ofO. viridirubra. Females of three oligolectic species are the only effective pollinators:Ptilothrix fructifera (Anthophoridae),Lithurgus rufiventris (Megachilidae), andCephalocolletes rugata (Colletidae). During their visits inOpuntia-flowers, bees touch the filaments and stimulate the movement of the stamens to the centre of the flower. At the end of this movement, the anthers are densely packed around the style. As a consequence the pollen is presented in an easily accessible upper layer of anthers and various, nearly inaccessible lower layers. The lower layers contain about 80% of the pollen reward. Only females of the three oligolectic pollinators exploit the pollen from the lower layers and reach the nectar furrow. Therefore, through their stamen movements,Opuntia flowers hide most of their pollen from flower visitors but favour effectively pollinating, oligolectic bees.

Do euglossine males (Apidae, Euglossini) leave tropical rainforest to collect fragrances in sugarcane monocultures?

Euglossine bees are known to be long-distance pollinators in tropical rainforests. But there is controversy concerning to the flight ranges of these bees between forest fragments. In an isolated fragment of Atlantic Rainforest in Pernambuco, NE Brazil, surrounded by sugarcane monocultures, it was examined if euglossine males leave closed rainforest to collect fragrances. In a straight-line transect leading from forest into a sugarcane plantation, euglossine males were simultaneously captured by scent baits at seven distinct points: inside the forest, forest edge, outside the forest in the sugarcane fields at distances of 10 m, 50 m, 100 m, 250 m and 500 m from the forest edge. A total of 945 euglossine bees of 16 species were recorded. The results demonstrate different relations of the Euglossini species to the closed forest. Males of 11 species did not leave the forest. Such species, together with the plants they are linked to, seem to be the most threatened by habitat fragmentation. Only bees of five species were found at the scent baits in the sugarcane fields. Already the 10 m sampling point outside the forest showed a drastic reduction in species richness, indicating that the forest edge functions as a barrier for most euglossine species.

Pollination of Campanula rapunculus L. (Campanulaceae): How much pollen flows into pollination and into reproduction of oligolectic pollinators?

Abstract.We studied an isolated population of Campanula rapunculus and two oligolectic bee species of Chelostoma (Megachilidae), their main pollinators. The population of C. rapunculus consisted of 2808 plants. Measurements of pollen flow showed that 3.7% of the pollen produced by a flower contribute to pollination, 95.5% was collected by bees for their offspring and 0.8% remained on the styles. Pollen analyses of brood cells of Chelostoma rapunculi revealed that females collected on average 4.9 million Campanula pollen to rear one bee. We calculated that approximately 1588 bees of this species could have been reared at the study site during the studied season. The amount of potentially viable pollen deposited on stigmas was 3.6 to 10.7 times higher than the number of ovules. We discuss morphological features of the flowers which may lower the pollen removal rate per bee visit and consequently cause a high visitation and pollination rate.

Searching for a Manageable Pollinator for Acerola Orchards: The Solitary Oil-Collecting Bee Centris analis (Hymenoptera: Apidae: Centridini)

ABSTRACT Acerola (Malpighia emarginata DC; Malpighiaceae) is an important fruit crop in Brazil. Among its pollinators, Centris (Heterocentris) analis (F.) stands out due to its abundance at flowers and prompt acceptance of trap-nests. For the first time, we propose the commercial use of Centris bees as orchard pollinators. To develop protocols for rearing and management of these bees, we analyzed trap-nest acceptance, brood-cell construction, and larval diet in Acerola orchards. Although Centris species, in general, use numerous pollen host plants, females of C. analis showed remarkable flower fidelity to Acerola for pollen supply when nesting in the orchard. Such fidelity was previously expected only for floral oil collection. The ease of acceptance of trap-nests by females of C. analis, their prolonged yearly activity period, multivoltine life history, and high pollinator efficiency characterize C. analis as an excellent potentially manageable pollinator in Acerola orchards.

Variation in daily flight activity and foraging patterns in colonies of uruçu - Melipona scutellaris Latreille (Apidae, Meliponini)

The flight activities of five colonies of Melipona (Michmelia) scutellaris Latreille, 1811 kept among mixed fruit crop plantations in within fragments of Atlantic Rainforest in Pernambuco, NE-Brazil was examined. The daily deployment of foragers to collect pollen, nectar, resin and mud was observed. The colonies performed between 2,640 and 14,250 flights per day. Variations in the number of total daily flights were similar between colonies on all observation days. Proportional allocation of foragers to the different resources also among colonies showed similar variation. More than 90% of the pollen collection flights were made early in the morning. Nectar was collected in similar proportional frequencies with a reduction in activity at noon. On a single day, was observed atypical intense pollen foraging during the afternoon by all colonies. This indicates a high plasticity in foraging behaviour and efficient recruitment to resources which are presented by mass flowering trees with synchronised big bang or multiple bang flowering. Resource availability of the surrounding vegetation, therefore, seems to be the major factor in defining the forager activities on a given day.

The Key Role of 4-methyl-5-vinylthiazole in the Attraction of Scarab Beetle Pollinators: a Unique Olfactory Floral Signal Shared by Annonaceae and Araceae

Cyclocephaline scarabs are specialised scent-driven pollinators, implicated with the reproductive success of several Neotropical plant taxa. Night-blooming flowers pollinated by these beetles are thermogenic and release intense fragrances synchronized to pollinator activity. However, data on floral scent composition within such mutualistic interactions are scarce, and the identity of behaviorally active compounds involved is largely unknown. We performed GC-MS analyses of floral scents of four species of Annona (magnoliids, Annonaceae) and Caladium bicolor (monocots, Araceae), and demonstrated the chemical basis for the attraction of their effective pollinators. 4-Methyl-5-vinylthiazole, a nitrogen and sulphur-containing heterocyclic compound previously unreported in flowers, was found as a prominent constituent in all studied species. Field biotests confirmed that it is highly attractive to both male and female beetles of three species of the genus Cyclocephala, pollinators of the studied plant taxa. The origin of 4-methyl-5-vinylthiazole in plants might be associated with the metabolism of thiamine (vitamin B1), and we hypothesize that the presence of this compound in unrelated lineages of angiosperms is either linked to selective expression of a plesiomorphic biosynthetic pathway or to parallel evolution.

POLLINATION OF PHILODENDRON ACUTATUM (ARACEAE) IN THE ATLANTIC FOREST OF NORTHEASTERN BRAZIL: A SINGLE SCARAB BEETLE SPECIES GUARANTEES HIGH FRUIT SET

Philodendron acutatum (Araceae) is a hemiepiphyte common to the Atlantic Forest of northeastern Brazil. In two localities, we studied the species’ breeding system and associations with flower‐visiting insects, along with an analysis of its floral scent composition. The fruit set of self‐incompatible P. acutatum was high, more than 90%, and inflorescences were exclusively pollinated by one species of scarab beetle, Cyclocephala celata (Scarabaeidae, Dynastinae). Pollinators are drawn toward the inflorescences at dusk by strong floral fragrances given off during the female phase of anthesis, along with endogenous heating of the spadix, whose temperatures were recorded at more than 11°C above ambient air. Two other species of flower‐visiting Cyclocephala were also consistently recovered in blacklight trappings during the flowering period of P. acutatum. The fact that only C. celata was found in association with P. acutatum suggests a local reproductive dependence of the plant to this scarab beetle species. Dihydro‐β‐ionone and 2‐hydroxy‐5‐methyl‐3‐hexanone, a rare volatile molecule so far unreported as a floral compound, together accounted for more than 97% of the unique scent composition of P. acutatum and might be involved in specific attraction of C. celata.

Specialized solitary bees as effective pollinators of South Brazilian species of Notocactus and Gymnocalycium (Cactaceae)

Summary: The range of flower-visiting bees of *Notocactus polyacanthus, N. sellowii, N. sucineus, and Gymnocalycium denudatum was recorded in the Serra do Sudeste, Rino Grande do Sul, Brazil. 6 out of 22 bee species were noted as frequent visitors to the cactus flowers. For each cactus species we determined the relative frequency of the bees in the flowers, and of stigma contacts during the flower visits. Flower fidelity was determined by analyses of the pollen loads of the females. The effectiveness of the bees as pollinators was recorded for each cactus species. Arhysosage cactorum (Andrenidae), Sarocolletes rugata (Colletidae), and Ancyloscelis fiebrigi (Anthophoridae), specialized solitary bees, are the most effective pollinators of the studied species of Notocactus and Gymnocalycium. Various species of Notocacteae share the same main pollinators. Polylectic and social bees contribute little to the pollination of the cactus species examined in the studied region.

The Chemical Basis of Host-Plant Recognition in a Specialized Bee Pollinator

Many pollinators specialize on a few plants as food sources and rely on flower scents to recognize their hosts. However, the specific compounds mediating this recognition are mostly unknown. We investigated the chemical basis of host location/recognition in the Campanula-specialist bee Chelostoma rapunculi using chemical, electrophysiological, and behavioral approaches. Our findings show that Ca. trachelium flowers emit a weak scent consisting of both widespread and rare (i.e., spiroacetals) volatiles. In electroantennographic analyses, the antennae of bees responded to aliphatics, terpenes, aromatics, and spiroacetals; however, the bioassays revealed a more complex response picture. Spiroacetals attracted host-naive bees, whereas spiroacetals together with aliphatics and terpenes were used for host finding by host-experienced bees. On the intrafloral level, different flower parts of Ca. trachelium showed differences in the absolute and relative amounts of scent, including spiroacetals. Scent from pollen-presenting flower parts elicited more feeding responses in host-naive bees as compared to a scentless control, whereas host-experienced bees responded more to the nectar-presenting parts. Our study demonstrates the occurrence of learning (i.e., change in the bee’s innate chemical search-image) after bees gain foraging experience on host flowers. We conclude that highly specific floral volatiles play a key role in host-flower recognition by this pollen-specialist bee, and discuss our findings into the broader context of host-recognition in oligolectic bees.

Hawkmoths (Lepidoptera, Sphingidae) in the Tabuleiro Paraibano, northeastern Brazil: abundance, richness and relations to sphingophilous plants

Hawkmoths (Sphingidae) are among the major pollinators in tropical communities. Here the first survey of sphingids and related plants in Northeastern Brazil is presented. The sphingids were surveyed from March 1999 through April 2000 at the Reserva Biologica Guaribas, Mamanguape, Paraiba State. On black and mix light traps, 136 hawkmoths from 24 species were captured. Individuais of Erinnyis ello (Linnaeus, 1758), Isognathus menechus (Boisduval, 1875) and Xylophanes tersa (Linnaeus, 1771) represented 58% of the samples. One half of the recorded species show wide distribution in the Neotropics. Three species were registered for more than six months. Most of the species were found only in the dry or wet season. Pollen from 34 plant species were recorded by pollen analysis of sphingid mouth parts. Hancornia speciosa (Apocynaceae) and Guettarda platipoda (Rubiaceae) were the most important food plants. Both are characteristic elements of the Tabuleiro Nordestino and present typically sphingophilous flowers. More than one half of the sphingids presented pollen from only one or two species of plants. By transporting large quantities of pollen of a few species, hawkmoths seem to be the main pollinators of nocturnal flowers in the Tabuleiro Paraibano.