Pollination ecology of Ecuadorian Asclepiadoideae (Apocynaceae): How generalized are morphologically specialized flowers?

This paper studies phenology and pollination ecology of an assemblage of nine small-flowered species of Asclepiadoideae–Asclepiadeae in a southern Ecuadorian mountain forest. These observations were augmented by laboratory studies of floral traits including scanning electron microscopy. Supported by multidimensional scaling analysis, three distinct pollination systems were identified: (a) pollination by small flies (Orthosia, Scyphostelma), (b) pollination by small bees and flies (Ditassa), and (c) pollination unspecialized (“Cynanchum”, Jobinia, Oxypetalum). Although numerous floral visitors were observed in the field, pollinaria were carried by only seven insect species. The average pollinaria removal rate of all species was low with 0.32±0.13%, and still lower for the pollinia insertion rate with 0.13±0.07%. The ratio of inserted pollinia to removed pollinaria was comparatively high with an average of 42.7±22.3%. If an insect achieved pollinia transfer, it did so very effectively. The complex floral morphology of the Asclepiadoideae has often been interpreted as a general trend toward specialization, but our observations indicate that the flowers are specialized functionally rather than ecologically.     

Observations of the floral biology ofPrasophyllum odoratum (Orchidaceae,Spiranthoideae)

Prasophyllum odoratum is a vernal, nectariferous, terrestrial orchid that flowers profusely six to eight months following cyclical fires that disrupt sclerophyll woodlands. The morphology of the column and pollinarium is indicative of taxa placed within the subfam.Spiranthoideae. The orientation of the pollinaria to the stigma appears to prevent mechanical self-pollination. Both cross- and self-pollination appear to be effected by insects that forage within the brightly-colored, scented, non-resupinate flowers. Ants and drosophilid flies remove nectar, but do not appear to transport pollinaria between flowers. The primary pollinators are polytrophic flies in the fam.Syrphidae and opportunistic male bees in the genusLeioproctus (Colletidae). Approximately 52% of the flowers on a raceme set seed. The comparatively short floral tube ofP. odoratum reflects the dependence of this species on short-tongued insects to effect successful dispersal of pollinaria.     

Moth pollination of Metaplexis japonica (Apocynaceae): pollinaria transfer on the tip of the proboscis

Asclepiad pollinaria (including pollen masses) attach to diverse body parts of flower visitors in many ways. In this paper, we observed nocturnal moths (Lepidoptera: Pyralidae and Noctuidae) transporting the pollinaria of the Japanese species Metaplexis japonica (Thunb.) Makino (Apocynaceae: Asclepiadoideae) on the tip of the proboscis. Flowers of this species may induce nectar-feeding moths to pull out the proboscis along a guide rail (anther slit), thus clipping the pollinaria onto the tip of the proboscis and transferring the pollinaria to the next flower. The transfer of pollinaria on the unique vector of a moth proboscis tip is an interesting pollination mechanism among previously reported entomophiles.     

Scent chemistry and pollinator attraction in the deceptive trap flowers of Ceropegia dolichophylla

Ceropegia species (Apocynaceae, Asclepiadoideae) have pitfall flowers and are pollinated by small flies through deception. It has been suggested that these flies are attracted by floral scent. However, the scent that is emitted from Ceropegia flowers has not been studied using headspace and gas chromatography mass spectrometry methods. It has also been unclear whether or not the flowers are mimics of particular models that attract flies. In the present study, we determined the composition as well as the spatial and temporal patterns of floral scent emitted by C. dolichophylla. Furthermore, we determined the pollinators in the native (China) and non-native (Germany) range of this species, and tested the capability of the floral scent to attract flies in the non-native range. Our data demonstrate that the floral scent, which is emitted from morning until evening, primarily from the tips of the corolla lobes, consists mainly of spiroacetals and aliphatic compounds. Milichiid flies were common visitors/pollinators in the native as well as non-native range, and were attracted by floral scent in bioassays performed in the non-native range. The compounds emitted by C. dolichophylla are unusual for flowers, but are well known from insect pheromones and occur in the glandular secretions of insects. The milichiid flies that visit and pollinate the flowers are kleptoparasites that feed on the prey (haemolymph or other secretions) of predatory arthropods, e.g. spiders, to which they are attracted by scent. Our data thus suggest that the floral scent of C. dolichophylla mimics the feeding sites of kleptoparasitic flies.     

The pollination ofStenorrhynchos lanceolatus (Aublet) L. C. Rich. (Orchidaceae: Spiranthinae) by hummingbirds in southeastern Brazil

Hummingbird pollination is documented for a natural population ofStenorrhynchos lanceolatus Aublet. L. C. Rich. occurring in Rio de Janeiro State, southeastern Brazil. At the study site the plants are pollinated byPhaethornis eurynome (Phaethorninae),Thalurania glaucopis (females only) andLeucochloris albicollis (Trochilinae). The plants offer nectar as a reward and the pollinaria become stuck to the surface of the hummingbird's bill while it is probing the flowers. The orchid population received a few (0–4) hummingbird visits per day, with about 83% of the flowers being pollinated. In spite of the low frequency of visits, the granular structure of the pollinarium plus the behaviour of the most frequent pollinators, which tend to visit all the fresh-looking flowers of each inflorescence, a very high fruiting success was promoted. Experimental evidence suggests that the pollinaria may remain up to 6.30 hours on the hummingbird's bill, enhancing the chances of cross-pollination and long-distance pollen flow.     

Bird pollination in South African species ofSatyrium (Orchidaceae)

Field observations showed that three South African orchid species,Satyrium carneum, S. coriifolium andS. princeps, are pollinated by sunbirds. Foraging sunbirds insert their bills into the labellum chamber of the flowers and suck nectar from the labellum spurs with their tongues. The column overarches the entrance to the labellum and pollinaria become affixed to the upper mandible of the bill. Birds often attempt to remove pollinaria by rubbing their bills against a branch, but are mostly unsuccessful due to the large plate-like viscidia which attach the pollinaria very firmly to the bill. Other modifications for bird pollination in theseSatyrium species may include the red, carmine or orange colour of the flowers, sturdy inflorescence stems used for perching and large amounts of dilute nectar in the spurs. EachSatyrium species was pollinated by several species of sunbird, and despite some differences in flowering time, occasional hybrids occur at a site whereS. carneum andS. coriifolium share the same sunbird pollinators.     

Long-term ecology of euglossine orchid-bees (Apidae: Euglossini) in Panama

Summary Abundance patterns during 6–7 years and orchid visitation were determined for 51 species of the 57 local euglossine bees. Male bees were counted at 3 chemical attractants presented in the same manner each month. Sites were separated by 75 km but included wet Atlantic forest at 500 m elevation, moist forest at 180 m near Barro Colorado Island, and cloud forest at 900 m near the Pacific ocean. 1. From 15 to 30 euglossine species of 4 genera were active in each month and site; monthly species number and general bee abundance were positively correlated. Many species had 3 annual abundance peaks (range 1–4) and were active throughout the year, but peak annual abundances rarely occurred during late wet or early dry seasons. In contrast, Eufriesea generally were present as adults only 1–2 months in a year. 2. Euglossine populations were exceptionally stable. Species at each site were more stable than any known insect population, and stability and abundance were positively associated. However, year-to-year population stability and the degree of seasonality were not correlated. Among the three sites, the more diverse (species rich) bee assemblages displayed lower stability; these were the wetter and upland sites. 3. The most abundant bees visited more orchid species. Eg. and El. each visited and average of 4 orchid species (range 0–13); Ex. and Ef. visited 0–3. Stable populations did not visit more or fewer orchid species than did unstable populations. 4. Less than 68% of species at each site visited orchid flowers; less than a few dozen of the 100–800 bees counted in a day carried orchid pollinaria. Over 20% of the euglossine species never were seen with pollinaria at any site and probably seldom visit orchids in central Panama. 5. Most bee species visited 1 or no fragrance orchids in a given habitat. Orchids tended to utilize common pollinators that seldom included more than 1 species, and they utilized stable or unstable, seasonal or aseasonal bees. However, the most stable and abundant bee, Eg. imperialis, rarely pollinated orchids; fewer than 10 of ca. 20000 bees carried pollinaria. 6. Orchids may interact primarily with discrete seasonal bee population peaks-probably the emerging adults. Although specialized orchid preferences are implicated for species that visit few or no local orchids but pollinate other species and carry pollinaria in other areas, euglossine bees do not need orchids to survive or reproduce.     

Generalized fly-pollination in Ceropegia ampliata (Apocynaceae�CAsclepiadoideae): the role of trapping hairs in pollen export and receipt

Flowers of most species in the genus Ceropegia have elaborate adaptations to trap pollinating flies. Flies are trapped within a bulbous base of the flower after moving through an elongated corolla tube that is frequently lined with stiff hairs. When these hairs wilt after several days, insects held in the bulbous chamber at the base of the corolla tube are released. Despite such complex adaptations for trapping pollinators, key aspects of the pollination ecology including the identity of pollinators, presence or absence of nectar rewards, duration of pollinator trapping, and pollination success remain undescribed for most Ceropegia species. Importantly, no studies have empirically tested the role that trapping hairs may have on pollen export and receipt. We documented the pollination biology of Ceropegia ampliata in two natural populations and found that C. ampliata can be regarded as a generalist, being pollinated by flies from at least four families (Tachinidae, Sarcophagidae, Muscidae, and Lauxaniidae). The duration of the trapping phase lasted 2?C5?days and flowers produce small quantities of nectar. Pollination success was highly variable but generally low with occasional peaks suggesting that flies are likely to visit this species sporadically. Flowers that had already proceeded beyond the trapping phase generally had a significantly greater number of pollinaria removed than flowers that were still in the trapping phase, probably reflecting the longer exposure to pollinators. In contrast we found no differences in pollinarium removal between flowers with trapping hairs present and flowers with hairs experimentally disabled. The role of trapping hairs in the pollination success of C. ampliata therefore remains uncertain although we propose, on the basis of this experiment, that trapping may be an adaptation to enhance female success through pollen deposition rather than pollen export. Given the low rates of natural pollen deposition, an experiment with a large number of replicates is required to test this hypothesis in Ceropegia.     

Non-functional flowers in Cat as e turn orchids (Gatasetinae, Orchidaceae)

ROMERO, G. A., 1992. Non-functional flowers in Catasetum orchids (Catasetinae, Orchidaceae). Plants of the genus Catasetum generally produce unisexual, dimorphic flowers but occasionally bear intermediate, polymorphic flowers. Staminate (male) flowers are commonly produced both in cultivation and in nature. Within the genus, the morphology, texture, resupination, and colour of male flowers are extremely variable. Pistillate (female) flowers, in contrast, are rarely produced in cultivation and in nature and have relatively constant morphology, texture, resupination and colour. Intermediate, polymorphic flowers are extremely rare, ranging in morphology from male-like to female-like, often combining characters of both. Some are bilaterally half male and half female. Intermediate flowers have previously been regarded as functionally hermaphroditic but evidence presented here shows that in Catasetum male and female functions appear to be mutually exclusive. Intermediate flowers that approach the morphology of female flowers may bear seeds but do not have functional pollinaria; those that approach male flower morphology do not have functional stigmas and seldom have functional pollinaria. The vast majority of Catasetum intermediate flowers are sterile. The absence of truly hermaphroditic flowers in Catasetum is important in the interpretation of evidence for gender choice in this genus, as flowers and/or plants can be unequivocally scored as either functionally male or female.     

Pollination biology of four sympatric species of Habenaria (Orchidaceae: Orchidinae) from southern Brazil

The pollination process and breeding system of the sympatric Habenaria johannensis, H. macronectar, H. megapotamensis and H. montevidensis was documented for native populations from Rio Grande do Sul, Brazil. All species investigated offer a nectar reward (mean values of total sugars ranging from 18 to 26%) concealed in a spur. Habenaria montevidensis is pollinated by butterflies (Hesperiidae, especially of the genus Urbanus) that carry pollinaria on their eyes; the other three species are pollinated by Sphingidae. Habenaria johannensis is pollinated by the moths Manduca rustica and M. sexta that carry the pollinaria at the base of the proboscis. Habenaria macronectar is pollinated by the moths Eumorpha labrusca and M. cf. lucetius, and these bear pollinaria between the palpi. Habenaria megapotamensis is pollinated by moths of M. cf. lucetius that bear the pollinaria on the proboscis. All species studied are self‐compatible, but pollinator dependent. They also displayed high reproductive success (ranging from 69.48 to 97.40%) and male efficiency factors slightly higher than 1, suggesting that at least one flower was pollinated for each flower acting as pollen donor. At the study sites, the investigated Habenaria spp. are isolated (in terms of pollination) by a set of factors that includes differing floral morphologies, different pollinators and/or different pollinarium placement on the pollinator. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, ??, ??–??.     

Fly pollination in Ceropegia (Apocynaceae: Asclepiadoideae): biogeographic and phylogenetic perspectives

Background and Aims

Ceropegia (Apocynaceae subfamily Asclepiadoideae) is a large, Old World genus of >180 species, all of which possess distinctive flask-shaped flowers that temporarily trap pollinators. The taxonomic diversity of pollinators, biogeographic and phylogenetic patterns of pollinator exploitation, and the level of specificity of interactions were assessed in order to begin to understand the role of pollinators in promoting diversification within the genus.

Methods

Flower visitor and pollinator data for approx. 60 Ceropegia taxa were analysed with reference to the main centres of diversity of the genus and to a cpDNA–nrDNA molecular phylogeny of the genus.

Key Results

Ceropegia spp. interact with flower-visiting Diptera from at least 26 genera in 20 families, of which 11 genera and 11 families are pollinators. Size range of flies was 0·5–4·0 mm and approx. 94 % were females. Ceropegia from particular regions do not use specific fly genera or families, though Arabian Peninsula species are pollinated by a wider range of Diptera families than those in other regions. The basal-most clade interacts with the highest diversity of Diptera families and genera, largely due to one hyper-generalist taxon, C. aristolochioides subsp. deflersiana. Species in the more-derived clades interact with a smaller diversity of Diptera. Approximately 60 % of taxa are so far recorded as interacting with only a single genus of pollinators, the remaining 40 % being less conservative in their interactions. Ceropegia spp. can therefore be ecological specialists or generalists.

Conclusions

The genus Ceropegia has largely radiated without evolutionary shifts in pollinator functional specialization, maintaining its interactions with small Diptera. Intriguing biogeographic and phylogenetic patterns may reflect processes of regional dispersal, diversification and subsequent specialization onto a narrower range of pollinators, though some of the findings may be caused by inconsistent sampling. Comparisons are made with other plant genera in the Aristolochiaceae and Araceae that have evolved flask-shaped flowers that trap female flies seeking oviposition sites.Key words: Apocynaceae, Asclepiadoideae, Brachystelma, Ceropegia, Diptera, flower evolution, generalization, mutualism, pollination, Riocreuxia, specialization, Stapeliinae     

Pollination, Flower Longevity, and Reproductive Biology of Gongora quinquenervis Ruíz and Pavón (Orchidaceae) in an Atlantic Forest Fragment of Pernambuco, Brazil

Abstract: The pollinators, flower longevity, and reproductive success of Gongora quinquenervis were studied in Refúgio Ecológico Charles Darwin, a preserved fragment of Atlantic Forest in Pernambuco. G. quinquenervis is epiphytic, and its flowers have osmophores, glands that produce aromatic volatiles, that are collected by males of Euglossini (Hymenoptera, Apidae). Every flower of an inflorescence opened simultaneously, however, overlaps in floral phases between individuals were low. Pollinaria deposition on the stigma caused immediate wilting of the perianth, while pollinaria removal had no influence on flower longevity. The reproductive system experiments showed that the species is self-compatible. The characteristics of floral morphology and its highly specialized pollination mechanism are efficient in limiting autogamy and geitonogamy and favouring cross-pollination. Three species of Euglossa were found ( E. cordata, E. perpulchra and an undescribed species) visiting the flowers of G. quinquenervis. All these efficiently removed the pollinaria of the flowers, which adhered to the posterior margin of the scutellum. Even though there was a high pollinaria removal rate by pollinators, the reproductive success in the field was extraordinarily low. We suggest that low fruit set, despite high pollinator frequency, is a result of a combination of the particular phonological characteristics of G. quinquenervis, such as short flower longevity and low overlap of flowering phases between individuals, leading to the reduced population of this orchid in the degraded Atlantic Forest. Conservation measures are necessary to guarantee the survival of G. quinquenervis in the northern part of the Atlantic Forest of Brazil.     

Telipogon peruvianus (Orchidaceae) Flowers Elicit Pre-Mating Behaviour in Eudejeania (Tachinidae) Males for Pollination

Several neotropical orchid genera have been proposed as being sexually deceptive; however, this has been carefully tested in only a few cases. The genus Telipogon has long been assumed to be pollinated by male tachinid flies during pseudocopulatory events but no detailed confirmatory reports are available. Here, we have used an array of methods to elucidate the pollination mechanism in Telipogon peruvianus. The species presents flowers that have a mean floral longevity of 33 days and that are self-compatible, although spontaneous self-pollination does not occur. The flowers attract males of four tachinid species but only the males of an undescribed Eudejeania (Eudejeania aff. browni; Tachinidae) species are specific pollinators. Males visit the flowers during the first few hours of the day and the pollination success is very high (42% in one patch) compared with other sexually deceptive species. Female-seeking males are attracted to the flowers but do not attempt copulation with the flowers, as is usually described in sexually deceptive species. Nevertheless, morphological analysis and behavioural tests have shown an imperfect mimicry between flowers and females suggesting that the attractant stimulus is not based only on visual cues, as long thought. Challenging previous conclusions, our chemical analysis has confirmed that flowers of Telipogon release volatile compounds; however, the role of these volatiles in pollinator behaviour remains to be established. Pollinator behaviour and histological analyses indicate that Telipogon flowers possess scent-producing structures throughout the corolla. Our study provides the first confirmed case of (i) a sexually deceptive species in the Onciidinae, (ii) pollination by pre-copulatory behaviour and (iii) pollination by sexual deception involving tachinid flies.     

POLLINATION OF RAFFLESIA (RAFFLESIACEAE)

The genus Rqfflesia includes about 13 species of parasitic flowering plants, among which are the largest known flowers. The flower with subtending scales is the only part of the plant external to the host and is produced solitary on roots (rarely stems) of the genus Tetrastigma (Vitaceae). Field studies were made of the pollination process in R. pricei, a species endemic to the Crocker Range in the Malaysian state of Sabah (northern Borneo). Pollination is mediated by carrion (bluebottle) flies of the genera Lucilla and Chrysomya. Experimental data indicate that both visual and olfactory cues are important in attracting flies to flowers. Flies (mostly female L. papuensis) obtain loads of the viscous liquid pollen matrix by visiting male flowers and entering anther grooves on the central column of the flower, precisely guided by ridges armed with hairs that force the fly into a position in which the pollen is positioned on the dorsal part of the thorax. “Windows” on the inside of the perigone diaphragm apparently help orient their flight inside flowers. Pollen-loaded flies visiting female flowers may enter the infradiscoidal sulcus formed by a broad ring of stigmatic tissue above and the expanded base of the column below. On entering the sulcus the fly is wedged in so tightly that pollen is rubbed off the thorax onto the stigma. Only large flies could be effective in picking up pollen from male flowers and transferring it to female flowers. The pollination syndrome is sapromyophily, in which the flower closely parallels trap flowers of several other plant families, although it is not a trap. The flower provides no reward for pollinators but deceives them by an apparent offering of food and possibly brood place. Rafflesia plants are extremely rare, perhaps in part because of infrequency of pollination, which requires neighboring male and female flowers simultaneously in bloom.     

Functional morphology and wasp pollination of two South American asclepiads (Asclepiadoideae-Apocynaceae)

Background and Aims

The extreme complexity of asclepiad flowers (Asclepiadoideae–Apocynaceae) has generated particular interest in the pollination biology of this group of plants especially in the mechanisms involved in the pollination processes. This study compares two South American species, Morrenia odorata and Morrenia brachystephana, with respect to morphology and anatomy of flower structures, dynamic aspects of the pollination mechanism, diversity of visitors and effectiveness of pollinators.

Methods

Floral structure was studied with fresh and fixed flowers following classical techniques. The pollination mechanism was studied by visiting fresh flowers in the laboratory with artificial pollinator body parts created with an eyelash. Morphometric and nectar measurements were also taken. Pollen transfer efficiency in the flowers was calculated by recording the frequency of removed and inserted pollinia. Visitor activity was recorded in the field, and floral visitors were captured for subsequent analysis of pollen loads. Finally, pollinator effectiveness was calculated with an index.

Key Results

The detailed structure of the flowers revealed a complex system of guide rails and chambers precisely arranged in order to achieve effective pollinaria transport. Morrenia odorata is functionally specialized for wasp pollination, and M. brachystephana for wasp and bee pollination. Pollinators transport chains of pollinaria adhered to their mouthparts.

Conclusions

Morrenia odorata and M. brachystephana present differences in the morphology and size of their corona, gynostegium and pollinaria, which explain the differences in details of the functioning of the general pollination mechanism. Pollination is performed by different groups of highly effective pollinators. Morrenia species are specialized for pollination mainly by several species of wasps, a specialized pollination which has been poorly studied. In particular, pompilid wasps are reported as important pollinators in other regions outside South Africa. A putative new function of nectar in asclepiads is presented, as it would be contributing to the pollination mechanism.     

Pollination biology of Cymbidium goeringii (Orchidaceae) in China

The genus Cymbidium comprises three subgenera with ca. 50 species. Interactions between pollinators and plants have been studied in the two subgenera Cymbidium and Cyperorchis, but only a few studies in the subgenus Jensoa have been reported. Here we report on the reproductive characteristics of C. goeringii (in sub-genus Jensoa) in three populations in the southwest of Hunan Province, China, during the winter from December 2005 to March 2006. Floral phenological and morphological features, behavior of visitors, the breeding system, and fruit sets under natural conditions were studied. The flowers of C. goeringii were strongly fragrant, but did not present any rewards to the visitors. The flowering period of C. goeringii in the studied populations lasted about 40 days, and most flowers (about 60%) opened within 30 days. Flowers opened immediately when temperature increased obviously and reached to about 16 ℃. The flowering time of the pollinated flowers, unpollinated flow-ers and the flowers with pollinarium removed were similar. Two bees of Apidae, Apis cerana cerana (honeybee) and Anthophora melanognatha, were observed visiting flowers of C. goeringii, but only the honeybees performed as pollinators. The honeybees mostly visited the orchid flowers at 10:00–17:00 on sunny days with temperature above 10 ℃. A total of only thirteen visits were observed during 20 days of observation, indicating pollinators were rare. Honeybees directly landed on the upper surface of the labellum and inserted their heads into the flowers between column and labellum, while the hind legs trod on the surface of the curved downward mid-lobe of label-lum. When a honeybee landed on the labellum of a flower, the labellum moved up and down slightly. After the honeybee entered the flower further, its head might touch the foot of the column. At this time, the body of the honeybee was parallel with the upper surface of the labellum. Then the honeybee used its front legs to scratch on the callus ridges on the upper surface of the labellum, and its hind legs hooked the edges of the side lobe of label-lum, trying to exit forcibly from the flower. During exiting process, sometimes the honeybee’s body was arched owing to tension. In this case, the surface of the scutellum came into close contact with the viscidium and then pollinaria, together with the anther cap, were removed. When this honeybee visited next flower, the pollinaria would be adhered to the stigma when it arched its body during the exiting process. Three plant species flowered synchronously with C. goeringii in the studied areas, but their flowers were different with C. goeringii in color or shape. Because C. goeringii is rewardless to pollinators, the flowers probably attract visitors by olfactory stimu-lus. Breeding system experiments showed no spontaneous autogamy and pollination success relying on pollinators in C. goeringii. Artificial pollination resulted in 90% fruit set by induced autogamy, 100% by pollinating within clone, and 100% by xenogamous pollination, respectively. These results indicate that C. goeringii is highly self-compatible and the fruit production is pollen limited. Because pollinators are essential for fruit set of C. goeringii in natural habitats, protection of wild honeybee populations or apiculture is likely a simple but effective strategy to maintain the orchid populations.     

Two new species of <Emphasis Type="Italic">Marsdenia</Emphasis> R. Br. (Apocynaceae: Asclepiadoideae) from the semi-arid region of Brazil

Two endangered new species of Marsdenia R. Br. (Asclepiadoideae, Apocynaceae) from the semi-arid region of Brazil are described and illustrated: M. breviramosa (south-western Bahia) and M. nana (northern Minas Gerais). They are shrubs closely related to M. zehntneri and, like that species, are also associated with calcareous outcrops. The former can be recognised by linear leaves arranged in small, compact shoots and the latter is a subshrub less than 50 cm high whose flowers are unique because of the adaxially villous corolla and long-rostrate gynostegium.     

Chrysophyllum marginatum (Sapotaceae): Generalist pollination and cryptic gynomonoecious

Chrysophyllum (Chrysophylloideae, Chrysophylleae) is the second largest genus in the Sapotaceae. Studies of pollination ecology in this genus are non-existent, although there are records of entomophily for this family. Considering the lack of detailed studies on pollination ecology and sexual systems in Chrysophyllum species, we investigate the floral morphology and biology and floral visitors of Chrysophyllum marginatum to verify which sexual system is present in the studied population and whether flowers of this species are visited and pollinated by different insect groups. The population of C. marginatum has weak and cryptic gynomonoecy because the plants produce a low percentage of functionally pistillate flowers (4.2%) and these flowers appear to be perfect flowers (hermaphrode). Flowers of C. marginatum are phenotypically, ecologically and functionally generalist because: (a) they are actinomorphic, open and not restrictive in terms of access to floral resources; (b) they are visited by 26 species of insects that are potential pollinators; and (c) among these species several groups can be effective pollinators, mainly bees and flies, according to the most effective pollinator principle. We consider bees and flies to be the main pollinator group of C. marginatum, due to their high visitation rate, richness and intrafloral visiting behavior, and because they especially forage among plant individuals and are able to promote xenogamy. Nectaries were found in the ovary base and osmophores in the petal margins, as floral attractants. For Chrysophyllum, this is the first record of gynomonoecy and for the family this is considered the second record. Chrysophyllum marginatum has generalist and entomophilous pollination, as recorded in other Sapotaceae Neotropical species.     

Genetic differentiation associated with host plants and geography among six widespread species of South American Blepharoneura fruit flies (Tephritidae)

Tropical herbivorous insects are astonishingly diverse, and many are highly host‐specific. Much evidence suggests that herbivorous insect diversity is a function of host plant diversity; yet, the diversity of some lineages exceeds the diversity of plants. Although most species of herbivorous fruit flies in the Neotropical genus Blepharoneura are strongly host‐specific (they deposit their eggs in a single host plant species and flower sex), some species are collected from multiple hosts or flowers and these may represent examples of lineages that are diversifying via changes in host use. Here, we investigate patterns of diversification within six geographically widespread Blepharoneura species that have been collected and reared from at least two host plant species or host plant parts. We use microsatellites to (1) test for evidence of local genetic differentiation associated with different sympatric hosts (different plant species or flower sexes) and (2) examine geographic patterns of genetic differentiation across multiple South American collection sites. In four of the six fly species, we find evidence of local genetic differences between flies collected from different hosts. All six species show evidence of geographic structure, with consistent differences between flies collected in the Guiana Shield and flies collected in Amazonia. Continent‐wide analyses reveal – in all but one instance – that genetically differentiated flies collected in sympatry from different host species or different sex flowers are not one another's closest relatives, indicating that genetic differences often arise in allopatry before, or at least coincident with, the evolution of novel host use.