Diverse pollination systems of the twin-spurred orchid genus Satyrium in African grasslands

The large terrestrial orchid genus Satyrium underwent evolutionary radiations in the Cape floral region and the grasslands of southern and eastern Africa. These radiations were accompanied by tremendous diversification of the unusual twin-spurred flowers that characterize the genus, but pollination data required to interpret these patterns of floral evolution have been lacking for grassland species in the genus. Here we document pollinators, nectar properties, and levels of pollination success for 11 grassland Satyrium species in southern and south-central Africa. Pollinators of these species include bees, beetles, butterflies, hawkmoths, noctuid moths, long-proboscid flies, and sunbirds. Most species appear to be specialized for pollination by one functional pollinator group. Long-proboscid fly pollination systems are reported for the first time in Satyrium (in S. macrophyllum and a high-altitude form of S. neglectum). Floral morphology, especially spur length and rostellum structure, differs markedly among plants with different pollinators, while nectar volume, concentration, and sugar composition are fairly uniform across species. Most taxa exhibited high levels of pollination success (>50% of flowers pollinated), a trend that can be attributed to the presence of nectar in the twin spurs.     

Intrafloral patterns of color and scent in Capparis spinosa L. and the ghosts of its selection past

Premise

Capparis spinosa is a widespread charismatic plant, in which the nocturnal floral habit contrasts with the high visitation by diurnal bees and the pronounced scarcity of hawkmoths. To resolve this discrepancy and elucidate floral evolution of C. spinosa, we analyzed the intrafloral patterns of visual and olfactory cues in relation to the known sensory biases of the different visitor guilds (bees, butterflies, and hawkmoths).

Methods

We measured the intrafloral variation of scent, reflectance spectra, and colorimetric properties according to three guilds of known visitors of C. spinosa. Additionally, we sampled visitation rates using a motion-activated camera.

Results

Carpenter bees visited the flowers eight times more frequently than nocturnal hawkmoths, at dusk and in the following morning. Yet, the floral headspace of C. spinosa contained a typical sphingophilous scent with high emission rates of certain monoterpenes and amino-acid derived compounds. Visual cues included a special case of multisensory nectar guide and color patterns conspicuous to the visual systems of both hawkmoths and bees.

Conclusions

The intrafloral patterns of sensory stimuli suggest that hawkmoths have exerted strong historical selection on C. spinosa. Our study revealed two interesting paradoxes: (a) the flowers phenotypically biased towards the more inconsistent pollinator; and (b) floral display demands an abundance of resources that seems maladaptive in the habitats of C. spinosa. The transition to a binary pollination system accommodating large bees has not required phenotypic changes, owing to specific eco-physiological adaptations, unrelated to pollination, which make this plant an unusual case in pollination ecology.     

Observations of hawkmoth pollination in the South African orchid Disa cooperi

Johnson, S. D. 1995. Observations of hawkmoth pollination in the South African orchid Disa cooperi . - Nord. J. Bot. 15: 121–125. Copenhagen. ISSN 0107–055X.
Disa cooperi is a robust grassland orchid with long-spud white flowers which are strongly scented in the evening. Observations at a site in Natal province, South Africa showed that hawkmoths are frequent visitors to the orchid at dusk. The hawkmoth Basiothia schenki was an effective pollinator of D. cooperi; this hawk-moth has a medium length proboscis (x = 4.3 cm) which can be fully inserted into the nectar-containing spur of the orchid. Pollinaria are attached ventrally to the basal portion of the proboscis where it joins the head. Another hawkmoth, Agrius convolvuli , commonly foraged on nectar from D. cooperi , but did not carry pollinaria, probably because its proboscis is too long (x = 10 cm) to allow contact between the thick basal portion of the proboscis and the orchid column. Lips in Disa are typically linear and do not produce scent, thus the autapomorphic spathulate and scent-producing lip of D. cooperi indicates that hawkmoth pollination is derived in this species, probably from a long-proboscid fly pollinated ancestor.     

Radiation in the Cape flora and the phylogeny of peacock irises Moraea (Iridaceae) based on four plastid DNA regions

Phylogenetic analyses of four plastid DNA regions, the rbcL exon, trnL intron, trnL-trnF intergenic spacer, and rps16 intron from each of 73 species in the African genus Moraea (Iridaceae: Irideae) including accessions of all major species clusters in the genus, show Moraea to be paraphyletic when Barnardiella, Galaxia, Hexaglottis, Homeria (all southern African), and Gynandriris (Eurasian as well) were recognized as separate genera. There are several small, isolated species clusters at the basal nodes of the tree that are all restricted to the winter-rainfall zone of southern Africa (the Greater Cape floral kingdom) and a few, highly derived, large species groups that have radiated extensively within the winter-rainfall zone. Mapping of floral traits shows that an Iris-type flower is ancestral in Moraea. Floral changes are associated with shifts in pollination systems, either from passive pollen deposition on long-tongued bees foraging for nectar to active pollen collection by female bees foraging for pollen, fly, or hopliine scarab beetle pollination. Dating the nodes of the phylogenetic tree using non-parametric rate smoothing with a calibration point derived from broad dating of the angiosperms indicates that the divergence between Moraea and its sister genus Ferraria occurred about 25 mya in the early Miocene. The early radiation of Moraea took place against a background of aridification and the spread of open habitats, such as desert, shrubland, and fynbos.     

The evolution of Cayaponia (Cucurbitaceae): Repeated shifts from bat to bee pollination and long-distance dispersal to Africa 2-5 million years ago

? Premise of the study: The Cucurbitaceae genus Cayaponia comprises ～60 species that occur from Uruguay to the southern United States and the Caribbean; C. africana occurs in West Africa and on Madagascar. Pollination is by bees or bats, raising the question of the evolutionary direction and frequency of pollinator shifts. Studies that investigated such shifts in other clades have suggested that bat pollination might be an evolutionary end point. ? Methods: Plastid and nuclear DNA sequences were obtained for 50 accessions representing 30 species of Cayaponia and close relatives, and analyses were carried out to test monophyly, infer divergence times, and reconstruct ancestral states for habitat preferences and pollination modes. ? Key results: The phylogeny shows that Cayaponia is monophyletic as long as Selysia (a genus with four species from Central and South America) is included. The required nomenclatural transfers are made in this paper. African and Madagascan accessions of C. africana form a clade that is part of a polytomy with Caribbean and South American species, and the inferred divergence time of 2-5 Ma implies a transoceanic dispersal event from the New World to Africa. The ancestral state reconstructions suggest that Cayaponia originated in tropical forests from where open savannas were reached several times and that bee pollination arose from bat pollination, roughly concomitant with the shifts from forests to savanna habitats. ? Conclusions: Cayaponia provides the first example of evolutionary transitions from bat to bee pollination as well as another instance of transoceanic dispersal from the New World to Africa.     

Middle and late Pleistocene faunas of Pinnacle Point and their paleoecological implications

The Western Cape region of South Africa is home to a unique type of mediterranean vegetation called fynbos, as well as some of the earliest sites of modern human occupation in southern Africa. Reconstructing the paleohabitats during occupations of these early anatomically modern Homo sapiens is important for understanding the availability of resources to the humans during the development of behaviors that are often considered advanced. These reconstructions are critical to understanding the nature of the changes in the environment and resources over time. Here we analyze the craniodental fossils of the larger mammals recovered from two Pleistocene assemblages in the Pinnacle Point complex, Mossel Bay, Western Cape Region, South Africa. We reconstruct the paleohabitats as revealed by multivariate analyses of the mammalian community structures. Pinnacle Point 30 is a carnivore assemblage and Pinnacle Point 13B includes early evidence of a suite of modern human behavior; together they present an opportunity to identify environmental change over time at a localized geographic scale. Further, this is the first such study to include dated Western Cape localities from Marine Isotope Stage 6, a time of environmental pressure that may have marginalized human populations. Results indicate that environmental change in the Western Cape was more complex than generalized C(4) grassland expansions replacing fynbos habitats during glacial lowered sea levels, and thus, resources available to early modern humans in the region may not have been entirely predictable.     

Insect diversity in Cape fynbos and neighbouring South African vegetation

Aim  It has often been suggested that South Africa's Cape fynbos shrublands, although extremely rich in plant species, are poor in insects, thus representing a notable exception from the broad plant–insect diversity relationship. The aims of this study were to compare the diversity patterns of plant-inhabiting insects in fynbos and the vegetation of three neighbouring biomes (grassland, subtropical thicket, and Nama-karoo), and to test for a general relationship between plant diversity and insect diversity across these biomes.
Location  South-western to south-eastern South Africa.
Methods  We conducted seasonal plant surveys and sweep insect sampling in 10 × 10 m plots in the Baviaanskloof Conservation Area (Eastern Cape), where all four biomes occur. We also conducted once-only collections in the core area of each biome.
Results  Fynbos plots had insect diversity values similar to those of grassland and subtropical thicket (a dense, evergreen and spinescent shrubland with a high abundance of succulents and climbers), and significantly higher than Nama-karoo (an open, semiarid shrubland). A remarkably strong positive relationship was found between plant and insect species richness.
Main conclusions  Previous generalizations were based on a few insect groups (e.g. butterflies, under-represented in fynbos), but ignored published results on other groups (e.g. galling insects, which are in fact over-represented in this vegetation). We show that, overall, insect diversity in fynbos is comparable to that of neighbouring biomes. Fynbos vegetation does not represent a significant exception from the broad positive relationship between plant diversity and insect diversity.     

EVOLUTION OF PLANT POLLINATION SYSTEMS: HYPOTHESES AND TESTS WITH THE NEOTROPICAL VINE DALECHAMPIA

The results of pollination and mating-system studies were integrated with a phylogenetic study of 40 Neotropical species of Dalechampia L. (Euphorbiaceae) to reconstruct the history of evolutionary change in pollination systems. The results of this analysis were treated as a hypothesis and tested for circularity problems and robustness in the face of changes in the data set. The historical hypothesis was used to make specific predictions about details of pollination ecology and reward biochemistry; the predictions were supported by independent observations. I conclude that pollination systems in Dalechampia have been evolutionarily labile, relative to most morphological features, with repeated parallelisms and reversals. Transitions among the three pollination systems evolved by Dalechampia (pollination by resin-collecting bees, fragrance-collecting male euglossine bees, and pollen-collecting bees) have been facilitated by biochemical exaptation (preadaptation). Pollination by male euglossine bees is relatively rare in the genus but has originated independently three to four times. In contrast, pollination by resin-collecting female bees is very common, but has originated only once. Eighty-six to 97% of transitions between pollination systems involved an intermediate phase during which both old and new pollinators were effective, but 3 to 14% of transitions may have been “instantaneous,” lacking the intermediate phase. Clades of species secreting resin rewards are about 10 times as species rich as clades of species secreting fragrance rewards; circumstantial evidence suggests that different extinction rates may be responsible for this difference. Relatively allogamous (cross-pollinating) species have evolved from more autogamous (self-pollinating) species up to 13 times, and autogamous species have evolved from more allogamous ones up to 11 times. Species occurring in disturbed habitats are facultatively autogamous, whereas species of undisturbed habitats are often highly allogamous.     

Flower visitors and pollination in the Oriental (Indomalayan) Region

Current knowledge of flower visitors and pollination in the Oriental Region is summarised. Much less is known about pollination than seed dispersal and the coverage of habitats and taxa in the region is very uneven. The available evidence suggests that pollination in lowland forests is dominated by highly social bees (mainly Trigona and Apis species), with beetles probably the next most important group, followed by other bees and flies. In comparison with the better-studied Neotropics, large solitary bees, moths, Lepidoptera and vertebrates are relatively less important. These differences are greatest in the canopy of the lowland dipterocarp forests of Southeast Asia, where they probably reflect the unique temporal pattern of floral resource availability resulting from 'general flowering' at supra-annual intervals. Apis bees (but not Trigona species) are also important in most montane, subtropical and non-forest habitats. Apart from the figs (Ficus spp.), there are few well-documented examples of plant species visited by a single potential pollinator and most plant-pollinator relationships in the region appear to be relatively generalised. The small sizes of most pollinators and the absence of direct human exploitation probably make pollination mutualisms less vulnerable to failure as a result of human impacts than dispersal mutualisms, but more subtle impacts, as a result of altered gene flows, are likely to be widespread. On current evidence, pollination systems in the Oriental Region do not require any specific conservation action, but this review reinforces arguments for making the preservation (or restoration) of habitat connectivity the major focus of Oriental conservation.     

Estimating the age of fire in the Cape flora of South Africa from an orchid phylogeny

Fire may have been a crucial component in the evolution of the Cape flora of South Africa, a region characterized by outstanding levels of species richness and endemism. However, there is, to date, no critical assessment of the age of the modern fire regime in this biome. Here, we exploit the presence of two obligate post-fire flowering clades in the orchid genus Disa, in conjunction with a robust, well-sampled and dated molecular phylogeny, to estimate the age by which fire must have been present. Our results indicate that summer drought (winter rainfall), the fire regime and the fynbos vegetation are several million years older than currently suggested. Summer drought and the fynbos vegetation are estimated to date back to at least the Early Miocene (ca 19.5 Ma). The current fire regime may have been established during a period of global cooling that followed the mid-Miocene Climatic Optimum (ca 15 Ma), which led to the expansion of open habitats and increased aridification. The first appearance of Disa species in the grassland biome, as well as in the subalpine habitat, is in striking agreement with reliable geological and palaeontological evidence of the age of these ecosystems, thus corroborating the efficacy of our methods. These results change our understanding of the historical mechanisms underlying botanical evolution in southern Africa, and confirm the potential of using molecular phylogenies to date events for which other information is lacking or inconclusive.     

Pollination in Lilium sargentiae (Liliaceae) and the first confirmation of long‐tongued hawkmoths as a pollinator niche in Asia

The geographical distribution of pollinators is an important factor determining the biogeographical pattern of floral evolution and diversification. In Africa, a guild of plant species has converged in a floral syndrome for pollination by long‐tongued hawkmoths (predominantly Agrius convolvuli). It is hypothesized that such floral convergence could track the geographical distribution of long‐tongued hawkmoths, so it may not be confined to Africa. We investigated the pollination biology of Lilium sargentiae E. H. Wilson, which is endemic to China and exhibits traits suggestive of long‐tongued hawkmoth pollination. Lilium sargentiae was visited by A. convolvuli as well as small beetles (Nitidulidae) but pollination was mostly or totally effected by the moth. It was consistent with other hawkmoth‐pollinated plants in terms of floral tube length, nectar traits, tepal reflectance, and scent composition. We present the first experimental evidence for the hypothesis proposed above and for hawkmoth pollination in the widespread and ornamentally and economically important genus Lilium L. in a natural habitat. Our findings imply that long‐tongued hawkmoths (especially the extremely widespread A. convolvuli) as a distinctive pollinator niche may have underlain the evolution of long‐tubed (>8 cm) flowers across different continents.     

Radiation of pollination systems in the Iridaceae of sub-Saharan Africa

BACKGROUND: Seventeen distinct pollination systems are known for genera of sub-Saharan African Iridaceae and recurrent shifts in pollination system have evolved in those with ten or more species. Pollination by long-tongued anthophorine bees foraging for nectar and coincidentally acquiring pollen on some part of their bodies is the inferred ancestral pollination strategy for most genera of the large subfamilies Iridoideae and Crocoideae and may be ancestral for the latter. Derived strategies include pollination by long-proboscid flies, large butterflies, night-flying hovering and settling moths, hopliine beetles and sunbirds. Bee pollination is diverse, with active pollen collection by female bees occurring in several genera, vibratile systems in a few and non-volatile oil as a reward in one species. Long-proboscid fly pollination, which is apparently restricted to southern Africa, includes four separate syndromes using different sets of flies and plant species in different parts of the subcontinent. Small numbers of species use bibionid flies, short-proboscid flies or wasps for their pollination; only about 2 % of species use multiple pollinators and can be described as generalists. SCOPE: Using pollination observations for 375 species and based on repeated patterns of floral attractants and rewards, we infer pollination mechanisms for an additional 610 species. Matching pollination system to phylogeny or what is known about species relationships based on shared derived features, we infer repeated shifts in pollination system in some genera, as frequently as one shift for every five or six species of southern African Babiana or Gladiolus. Specialized systems using pollinators of one pollination group, or even a single pollinator species are the rule in the family. Shifts in pollination system are more frequent in genera of Crocoideae that have bilaterally symmetric flowers and a perianth tube, features that promote adaptive radiation by facilitating precise shifts in pollen placement, in conjunction with changes in flower colour, scent and tube length. CONCLUSIONS: Diversity of pollination systems explains in part the huge species diversity of Iridaceae in sub-Saharan Africa, and permits species packing locally. Pollination shifts are, however, seen as playing a secondary role in speciation by promoting reproductive isolation in peripheral, ecologically distinct populations in areas of diverse topography, climate and soils. Pollination of Iridaceae in Eurasia and the New World, where the family is also well represented, is poorly studied but appears less diverse, although pollination by both pollen- and oil-collecting bees is frequent and bird pollination rare.     

Deceptive pollination in two subspecies of Disa spathulata (Orchidaceae) differing in morphology and floral fragrance

The non-rewarding flowers of Disa spathulata (L.f) Sw. have a highly elongated scent-producing lip that varies in size and form between the two subspecies of this orchid. We investigated whether this unusual morphology is associated with the evolution of a specialized scent-based pollination system. Field observations carried out in South Africa showed that flowers of D. spathulata are pollinated solely by bees belonging to the genus Tetraloniella (Anthophoridae). Flowers of D. spathulata subsp. spathulata were visited by Tetraloniella brevikeraia, while flowers of D. spathulata subsp. tripartita (Lindl.). H. P. Linder were visited by Tetraloniella junodi. The floral fragrance of D. spathulata is emitted by the lip blade and differs markedly between the two subspecies (only 24 [42.1] of the 57 compounds identified were shared). Fragrance of D. spathulata subsp spathulata is dominated by the fatty acid derivatives decyl actetate, octanol, and decanol, while that of D. spathulata subsp. tripartita is dominated by the terpenoids (E) - ocimene, caryophyllene, and (E) nerolidol. Both male and female Tetraloniella bees were strongly attracted to cut flowers of D. spathulata subsp spathulata, even at sites where the orchid does not naturally occur. Bees visit the orchids repeatedly despite the lack of rewards in their flowers. Sexual deception in D. spathulata can be excluded by the attraction of both male and female bees, and yet the manner in which bees are attracted seems too intense and species-specific to be characterized as food-deception. This implies the existence in D. spathulata of a system of scent-based deception of insects that has not been described previously in plants.     

Floral syndromes accurately predict pollination by a specialized oil-collecting bee (Rediviva peringueyi, Melittidae) in a guild of South African orchids (Coryciinae)

The long-standing notion of pollination syndromes, which postulates that plants form recognizable groups according to pollinator type, has been challenged recently on the basis of apparent widespread generalization in pollination systems. As a test of the pollination syndrome concept, I examined the pollination biology of a group of 15 orchids that share a recognizable syndrome of floral features that includes yellow-green coloration, oil secretion, pungent scent, shallow flowers, and a September peak in flowering. The orchids occur in sympatry in the Cape Floral Region of South Africa. According to the pollination syndrome concept, the similar floral features of this group indicate a shared pollinator. To test this prediction, I observed pollinators on Pterygodium alatum, P. caffrum, P. catholicum, P. volucris, Corycium orobanchoides, and Disperis bolusiana subsp. bolusiana. They shared a single species of pollinator, the oil-collecting bee, Rediviva peringueyi. Female bees collected oil from the lip appendage using modified front tarsi. The orchids reduce interspecific reproductive interference through differences in pollinarium length or the use of mutually exclusive pollinarium attachment sites on the body of the bee. The results are contrary to the expectation of generalization in pollination systems and suggest that pollinators play an important role in mediating selection on floral traits.     

Farmland in U.S. Conservation Reserve Program has unique floral composition that promotes bee summer foraging

Bee conservation is a topic of global concern, particularly in agroecosystems where their contribution to crop pollination is highly valued. Over a decade ago, bees and other pollinators were made a priority of the Conservation Reserve Program (CRP), a U.S. federal program that pays land owners to establish a conservation cover, typically grassland, on environmentally sensitive farmland. Despite large financial investment in this program, few studies have measured the benefit of CRP to bees, particularly in complex agroecosystems with abundant alternative forage. To determine if CRP land seeded with pollinator-attractive native flowers and/or introduced legumes provides distinct floral composition that attracts more foraging bees than non-CRP habitats, we compared CRP land to paired non-CRP fields and roadsides at 31 sites in Michigan, U.S.A.. We found CRP land had unique floral species community composition, higher floral abundance, greater species richness, more native floral species, and greater inflorescence coverage. Greater inflorescence coverage on CRP land was associated with a greater abundance of both honey bees and wild bees than either non-CRP fields or roadsides, as was native flower abundance for wild bees. Showy native plant species were important forage resources on CRP land: Monarda fistulosa was the most foraged upon species by both honey bees and wild bees, and goldenrod species were important late-summer forage resources for honey bees. These findings demonstrate the benefit of managing CRP land with herbaceous seed mixes to create dense, showy, native plant communities that provide summer-long resources to both bee groups. Insights from this study could be used to enhance the composition of future conservation program investments and management of non-CRP land to benefit pollinators.     

THE INFLUENCE OF HABITAT ON THE DISTRIBUTION AND ABUNDANCE OF PEREGRINE AND LANNER FALCONS IN SOUTH AFRICA

Jenkins, A.R. 1994. The influence of habitat on the distribution and abundance of Peregrine and Lanner Falcons in South Africa. Ostrich 65: 281–290.

The distribution and abundance of Peregrine and Lanner Falcons in South Africa was compared using recorded sightings from various sources, including the Southern African Bird Atlas Project. Falcon distributions were compared with the distribution of cliffs and vegetation, to quantify differences in the habitat preferences of the two species in the breeding and the non-breeding seasons. Lanner Falcons outnumbered Peregrine Falcons in most areas by at least 10:1. Peregrine Falcons were more habitat specific than Lanner Falcons, in terms of topographic and biotic requirements. Peregrine Falcons were largely restricted to high cliff areas throughout the year and there probably were no large-scale seasonal movements within the population. The bulk of the resident Peregrine Falcon population was found in the fynbos biome, in the southwestern Cape. Outside of this area, Peregrine Falcons were concentrated in woodlands. Lanner Falcons were less dependent on high cliffs, although cliff availability was important in defining the ranges of both species. Lanner Falcons were most common in the sour grasslands in the east of the country in the breeding season, with apparent movements in the non-breeding season into the fynbos, the Nama Karoo and the southern Kalahari. Overall, Peregrine Falcons favoured relatively closed habitats and Lanner Falcons favoured relatively open habitats. The differences in the two species' habitat preferences are proximate factors influencing distribution and abundance.     

The influence of distinct pollinators on female and male reproductive success in the Rocky Mountain columbine

Although there are many reasons to expect distinct pollinator types to differentially affect a plant's reproductive success, few studies have directly examined this question. Here, we contrast the impact of two kinds of pollinators on reproductive success via male and female functions in the Rocky Mountain columbine, Aquilegia coerulea . We set up pollinator exclusion treatments in each of three patches where Aquilegia plants were visited by either day pollinators (majority bumble bees), by evening pollinators (hawkmoths), or by both (control). Day pollinators collected pollen and groomed, whereas evening pollinators collected nectar but did not groom. Maternal parents, potential fathers and progeny arrays were genotyped at five microsatellite loci. We estimated female outcrossing rate and counted seeds to measure female reproductive success and used paternity analysis to determine male reproductive success. Our results document that bumble bees frequently moved pollen among patches of plants and that, unlike hawkmoths, pollen moved by bumble bees sired more outcrossed seeds when it remained within a patch as opposed to moving between patches. Pollinator type differentially affected the outcrossing rate but not seed set, the number of outcrossed seeds or overall male reproductive success. Multiple visits to a plant and more frequent visits by bumble bees could help to explain the lack of impact of pollinator type on overall reproductive success. The increase in selfing rate with hawkmoths likely resulted from the abundant pollen available in experimental flowers. Our findings highlighted a new type of pollinator interactions that can benefit a plant species.     

Three new species of <Emphasis Type="Italic">Sarcocornia</Emphasis> (Chenopodiaceae) from South Africa

Sarcocornia decussata, S. freitagii and S. tegetaria from South Africa are described as new taxa. Sarcocornia decussata and S. freitagii are narrow endemics of the West Coast of South Africa where they are found in inland saline habitats (quartz patches, salt pans and saline alluvia) while S. tegetaria is an endemic of southern African coasts (spanning Namibia, South Africa and Mozambique) where it is confined to low-lying intertidal habitats of estuaries.     

Character displacement in style length between pollinator-sharing Clerodendrum trichotomum and C. izuinsulare (Verbenaceae)

Competition for pollination may occur between pollinator-sharing sympatric plants and this may cause character displacement of their floral traits. We examined this possibility by comparing flower morphology of the sympatric population of Clerodendrum trichotomum and its co-flowering congener, C. izuinsulare, with that of the allopatric populations. The two species were visited in common by such insects as diurnal hawkmoths, bees, swallowtails and nocturnal hawkmoths, and were pollinated nocturnally as well as diurnally. Interspecific pollen transfer can occur by sharing pollinators; however, they did not hybridize when artificially pollinated. Flower size, including stamen and style lengths, is larger in C. trichotomum with an overlap in range. The style of C. izuinsulare in the sympatric population was significantly shorter than that in the allopatric population, while there was no significant difference in style length between the allopatric and the sympatric C. trichotomum. This seems to facilitate avoidance of interspecific pollen transfer in the sympatric population.Ken Inoue was killed in an accident on July 28, 2003, during his research trip in Sakhalin.