Insects, birds and lizards as pollinators of the largest-flowered Scrophularia of Europe and Macaronesia

Background and Aims

It has traditionally been considered that the flowers of Scrophularia are mainly pollinated by wasps. We studied the pollination system of four species which stand out for their large and showy flowers: S. sambucifolia and S. grandiflora (endemics of the western Mediterranean region), S. trifoliata (an endemic of the Tyrrhenian islands) and S. calliantha (an endemic of the Canary Islands). Our principal aim was to test whether these species were pollinated by birds or showed a mixed pollination system between insects and birds.

Methods

Censuses and captures of insects and birds were performed to obtain pollen load transported and deposited on the stigmas. Also, a qualitative and quantitative analysis of the flowers and inflorescences was carried out.

Key Results

Flowers were visited by Hymenoptera and by passerine birds. The Canarian species was the most visited by birds, especially by Phylloscopus canariensis, and its flowers were also accessed by juveniles of the lizard Gallotia stehlini. The most important birds in the other three species were Sylvia melanocephala and S. atricapilla. The most important insect-functional groups in the mixed pollination system were: honey-bees and wasps in S. sambucifolia; bumble-bees and wasps in S. grandiflora; wasps in S. trifoliata; and a small bee in S. calliantha.

Conclusions

The species studied show a mixed pollination system between insects and passerine birds. In S. calliantha there is, in addition, a third agent (juveniles of Gallotia stehlini). The participation of birds in this mixed pollination system presents varying degrees of importance because, while in S. calliantha they are the main pollinators, in the other species they interact to complement the insects which are the main pollinators. A review of different florae showed that the large showy floral morphotypes of Scrophularia are concentrated in the western and central Mediterranean region, Macaronesia and USA (New Mexico).     

Adaptation for rodent pollination in Leucospermum arenarium (Proteaceae) despite rapid pollen loss during grooming

Background and Aims

Plants are adapted for rodent pollination in diverse and intricate ways. This study explores an extraordinary example of these adaptations in the pincushion Leucospermum arenarium (Proteaceae) from South Africa.

Methods

Live trapping and differential exclusion experiments were used to test the role of rodents versus birds and insects as pollinators. To explore the adaptive significance of geoflory, inflorescences were raised above ground level and seed production was compared. Captive rodents and flowers with artificial stigmas were used to test the effect of grooming on the rate of pollen loss. Microscopy, nectar composition analysis and manipulative experiments were used to investigate the bizarre nectar production and transport system.

Key Results

Differential exclusion of rodents, birds and insects demonstrated the importance of rodents in promoting seed production. Live trapping revealed that hairy-footed gerbils, Gerbillurus paeba, and striped field mice, Rhabdomys pumilio, both carried L. arenarium pollen on their forehead and rostrum, but much larger quantities ended up in faeces as a result of grooming. Terrarium experiments showed that grooming exponentially diminished the pollen loads that they carried. The nectar of L. arenarium was found to be unusually viscous and to be presented in a novel location on the petal tips, where rodents could access it without destroying the flowers. Nectar was produced inside the perianth, but was translocated to the petal tips via capillary ducts. In common with many other rodent-pollinated plants, the flowers are presented at ground level, but when raised to higher positions seed production was not reduced, indicating that selection through female function does not drive the evolution of geoflory.

Conclusions

Despite the apparent cost of pollen lost to grooming, L. arenarium has evolved remarkable adaptations for rodent pollination and provides the first case of this pollination system in the genus.     

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.     

Generalist passerine pollination of a winter-flowering fruit tree in central China

Background and Aims

Winter-flowering plants outside the tropics may experience a shortage of pollinator service, given that insect activity is largely limited by low temperature. Birds can be alternative pollinators for these plants, but experimental evidence for the pollination role of birds in winter-flowering plants is scarce.

Methods

Pollinator visitation to the loquat, Eriobotrya japonica (Rosaceae), was observed across the flowering season from November to January for two years in central China. Self- and cross-hand pollination was conducted in the field to investigate self-compatibility and pollen limitation. In addition, inflorescences were covered by bird cages and nylon mesh nets to exclude birds and all animal pollinators, respectively, to investigate the pollination role of birds in seed production.

Results

Self-fertilization in the loquat yielded few seeds. In early winter insect visit frequency was relatively higher, while in late winter insect pollinators were absent and two passerine birds (Pycnonotus sinensis and Zosterops japonicus) became the major floral visitors. However, seed-set of open-pollinated flowers did not differ between early and late winter. Exclusion of bird visitation greatly reduced seed-set, indicating that passerine birds were important pollinators for the loquat in late winter. The whitish perigynous flowers reward passerines with relatively large volumes of dilute nectar. Our observation on the loquat and other Rosaceae species suggested that perigyny might be related to bird pollination but the association needs further study.

Conclusions

These findings suggest that floral traits and phenology would be favoured to attract bird pollinators in cold weather, in which insect activity is limited.     

Bird pollination in South African Salvia species

Approximately one-fourth of the more than 900 world-wide distributed Salvia species (Lamiaceae) is ornithophilous. With few exceptions they occur in the New World, being predominantly pollinated by hummingbirds. In the Old World only Salvia africana-lutea and the recently described Salvia thermarum, both from the Cape Province of South Africa, were observed to be pollinated by sunbirds and white-eyes. Among the 23 South African Salvia species Salvia lanceolata is a further candidate for being bird pollinated. For the first time we describe and illustrate its pollination by Nectarinia chalybea and Zosterops pallidus. We compare the ornithophilous syndrome of the three mentioned Salvia species and relate them to the morphological fitting of the most common nectarivorous birds of the Southwestern Cape (Cape peninsula to Worcester). We conclude that each of the birds could act as a pollinator and that the three co-occurring Salvia species are not mechanically isolated from each other. The degree of specialisation towards bird pollination, possible hybridisation events and evolution of bird pollination in South African Salvia species are discussed.     

Asymmetrical conspecific seed-siring advantage between Silene latifolia and S. dioica

Background and Aims

Silene dioica and S. latifolia experience only limited introgression despite overlapping flowering phenologies, geographical distributions, and some pollinator sharing. Conspecific pollen precedence and other reproductive barriers operating between pollination and seed germination may limit hybridization. This study investigates whether barriers at this stage contribute to reproductive isolation between these species and, if so, which mechanisms are responsible.

Methods

Pollen-tube lengths for pollen of both species in styles of both species were compared. Additionally, both species were pollinated with majority S. latifolia and majority S. dioica pollen mixes; then seed set, seed germination rates and hybridity of the resulting seedlings were determined using species-specific molecular markers.

Key Results

The longest pollen tubes were significantly longer for conspecific than heterospecific pollen in both species, indicating conspecific pollen precedence. Seed set but not seed germination was lower for flowers pollinated with pure heterospecific versus pure conspecific pollen. Mixed-species pollinations resulted in disproportionately high representation of nonhybrid offspring for pollinations of S. latifolia but not S. dioica flowers.

Conclusions

The finding of conspecific pollen precedence for pollen-tube growth but not seed siring in S. dioica flowers may be explained by variation in pollen-tube growth rates, either at different locations in the style or between leading and trailing pollen tubes. Additionally, this study finds a barrier to hybridization operating between pollination and seed germination against S. dioica but not S. latifolia pollen. The results are consistent with the underlying cause of this barrier being attrition of S. dioica pollen tubes or reduced success of heterospecifically fertilized ovules, rather than time-variant mechanisms. Post-pollination, pre-germination barriers to hybridization thus play a partial role in limiting introgression between these species.     

Pollination systems of Colchicum (Colchicaceae) in southern Africa: evidence for rodent pollination

Background and Aims

Plants adapted for pollination by rodents tend to exhibit a distinct floral syndrome that includes dull coloured and geoflorous inflorescences and nocturnal anthesis and nectar production. On the basis of their floral traits, it was predicted that two African Colchicum species (C. scabromarginatum and C. coloratum) are rodent-pollinated.

Methods

Field studies were carried out in the semi-arid Succulent Karoo region of South Africa. Live trapping of rodents was conducted and pollen loads on the rodents were quantified. The daily periodicity of nectar production was determined. Selective exclusion and controlled pollination experiments were also conducted.

Key Results

Live-trapped rodents were found to carry large amounts of Colchicum pollen on the fur of their snouts, and in their faeces. Birds were occasional pollinators of flowers of C. coloratum. During the evening, nectar volume and concentration increased for both species. When vertebrates were excluded from C. scabromarginatum and C. coloratum plants, there was a significant decrease in seed set compared with open control plants. By contrast, vertebrate exclusion did not significantly affect seed production of a congener, C. hantamense, which has floral traits associated with insect pollination. Breeding system experiments revealed that both C. scabromarginatum and C. coloratum require pollinators for seed production. Colchicum scabromarginatum is strictly self-incompatible, whereas C. coloratum is partially self-compatible.

Conclusions

Pollination by rodents occurs in two African Colchicum species. C. scabromarginatum appears to depend exclusively on rodents for seed production, while birds and autonomous selfing may contribute to seed production in C. coloratum. These are the first records of rodent pollination in the Colchicaceae.Key words: Convergent evolution, floral syndrome, pollination, rodents, birds, insects, Colchicum scabromarginatum, Colchicum coloratum, Succulent Karoo, southern Africa     

The importance of bees as pollinators in the short corolla bromeliad Aechmea caudata in southern Brazil

The majority of bromeliad species are pollinated by vertebrates, mainly hummingbirds and bats. However, bees are among the most frequent visitors in some short-corolla species with ornithophilous features, but only few studies identified insects as pollinators of these bromeliads. The importance of visitors for pollination success in Aechmea caudata (Bromeliaceae) was determined through the frequency and pollination effectiveness (measured as seed set/single visit) of its visitors in a secondary Atlantic forest area in southern Brazil. Aechmea caudata is self-incompatible and therefore pollinator-dependent. A total of 16 species were recorded visiting their flowers. Bees were the most rich and frequent taxon (91% of 647 visits). Bombus morio was the most frequent species (41%). Although the floral features of A. caudata, such as scentless, tubular corollas, yellow and red flowers, and nectar secretion during the whole diurnal anthesis, are related to ornithophily, the single hummingbird species Thalurania glaucopis failed to pollinate the flowers. Its low frequency (2.5%) apparently did not promote the pollen flux between conspecific bromeliads. Pollination tests showed that no seeds developed after hummingbird visits. Seeds were formed only at flowers visited by B. morio. We discuss our findings by contrasting them with the results on the similar and sympatric A. lindenii and by emphasizing the importance of bees for pollination of bromeliads with short corolla. Our results show that pollination effectiveness together with frequency data are necessary to analyze the complex interactions between plants and their flower visitors.     

Escape from extreme specialization: passionflowers,bats and the sword-billed hummingbird

A striking example of plant/pollinator trait matching is found between Andean species of Passiflora with 6–14-cm-long nectar tubes and the sword-billed hummingbird, Ensifera ensifera, with up to 11-cm-long bills. Because of the position of their anthers and stigmas, and self-incompatibility, these passionflower species depend on E. ensifera for pollination. Field observations show that the bird and plant distribution match completely and that scarcity of Ensifera results in reduced passionflower seed set. We here use nuclear and plastid DNA sequences to investigate how often and when these mutualisms evolved and under which conditions, if ever, they were lost. The phylogeny includes 26 (70%) of the 37 extremely long-tubed species, 13 (68%) of the 19 species with tubes too short for Ensifera and four of the seven bat-pollinated species for a total of 43 (69%) of all species in Passiflora supersection Tacsonia (plus 11 outgroups). We time-calibrated the phylogeny to infer the speed of any pollinator switching. Results show that Tacsonia is monophyletic and that its stem group dates to 10.7 Ma, matching the divergence at 11.6 Ma of E. ensifera from its short-billed sister species. Whether pollination by short-billed hummingbirds or by Ensifera is the ancestral condition cannot be securely inferred, but extremely long-tubed flowers exclusively pollinated by Ensifera evolved early during the radiation of the Tacsonia clade. There is also evidence of several losses of Ensifera dependence, involving shifts to bat pollination and shorter billed birds. Besides being extremely asymmetric—a single bird species coevolving with a speciose plant clade—the Ensifera/Passiflora system is a prime example of a specialized pollinator not driving plant speciation, but instead being the precondition for the maintenance of isolated populations (through reliable seed set) that then underwent allopatric speciation.     

Pollination of Specklinia by nectar-feeding Drosophila: the first reported case of a deceptive syndrome employing aggregation pheromones in Orchidaceae

Background and Aims The first documented observation of pollination in Pleurothallidinae was that of Endrés, who noticed that the ‘viscid sepals’ of Specklinia endotrachys were visited by a ‘small fly’. Chase would later identify the visiting flies as being members of the genus Drosophila. This study documents and describes how species of the S. endotrachys complex are pollinated by different Drosophila species.Methods Specimens of Specklinia and Drosophila were collected in the field in Costa Rica and preserved in the JBL and L herbaria. Flies were photographed, filmed and observed for several days during a 2-year period and were identified by a combination of non-invasive DNA barcoding and anatomical surveys. Tissue samples of the sepals, petals and labellum of Specklinia species were observed and documented by SEM, LM and TEM. Electroantennogram experiments were carried out on Drosophila hydei using the known aggregation pheromones ethyl tiglate, methyl tiglate and isopropyl tiglate. Floral compounds were analysed by gas chromatography–mass spectometry using those same pheromones as standards.Key Results Flowers of S. endotrachys, S. pfavii, S. remotiflora and S. spectabilis are visited and pollinated by several different but closely related Drosophila species. The flies are arrested by aggregation pheromones, including ethyl tiglate, methyl tiglate and isopropyl tiglate, released by the flowers, and to which at least D. hydei is very sensitive. Visible nectar drops on the adaxial surface of sepals are secreted by nectar-secreting stomata, encouraging male and female Drosophila to linger on the flowers for several hours at a time. The flies frequently show courtship behaviour, occasionally copulating. Several different Drosophila species can be found on a single Specklinia species.Conclusions Species of the S. endotrachys group share a similar pollination syndrome. There seem to be no species-specific relationships between the orchids and the flies. It is not expected that Specklinia species will hybridize naturally as their populations do not overlap geographically. The combination of pheromone attraction and nectar feeding is likely to be a generalized pollination syndrome in Pleurothallidinae.     

Variations of floral traits among different life forms illustrate the evolution of pollination systems in Potamogeton species from China

Four leaf morpha groups (floating-leaved, submerged broad-leaved, submerged linear-leaved and filiform-leaved) and three inflorescences type groups (erect, facultative floating and floating) can be found in the genus Potamogeton. Life forms in the genus correlate with pollination types (anemophily, epihydrophily and hydroautogamy). Floral traits vary greatly among different life forms and pollination types. Both floating and submerged broad-leaved species produce erect inflorescences that are suited for anemophilous pollination. These flowers also have the highest pollen/ovule (P/O) ratio (25,013) and the smallest pollen grain volume (6046 μm³). On the contrary, submerged filiform-leaved species produce only floating inflorescences and their flowers produce the largest pollen grains (17,567 μm³) and have the lowest P/O ratio (6752), which is typical of the syndromes of hydroautogamy and epihydrophily. The relatively prolific seed production (about 70%) and wide dispersal in the floating and submerged broad-leaved species and the submerged filliform-leaved species indicate that these two groups are well adapted to the aquatic environment. This is in contrast with the less well-adapted complex and unstable pollination system found in linear-leaved species. We propose that the pollination systems and life forms in the Potamogeton, have undergone modification in response to the demands imposed by the aquatic environment during the evolutionary process in the genus.     

A pioneer survey and DNA barcoding of some commonly found gastropod molluscs on Robben Island

Nineteen species of abundant gastropods were collected at Robben Island, including introduced dune snails and European brown garden snails. They were identified using morphology and DNA barcoding. It was expected that the species recorded would be similar to those from the Cape peninsula, South Africa, but we were surprised to find some exceptions: the very abundant invasive mussel species in South Africa, the South American bisexual mussel (Semimytilus algosus), and the beaded topshells (Oxystele impervia) were not found on Robben Island. Possible explanations are presented for these differences.     

First record of bat-pollination in the species-rich genus Tillandsia (Bromeliaceae)

Background and Aims

Bromeliaceae is a species-rich neotropical plant family that uses a variety of pollinators, principally vertebrates. Tillandsia is the most diverse genus, and includes more than one-third of all bromeliad species. Within this genus, the majority of species rely on diurnal pollination by hummingbirds; however, the flowers of some Tillandsia species show some characteristics typical for pollination by nocturnal animals, particularly bats and moths. In this study an examination is made of the floral and reproductive biology of the epiphytic bromeliad Tillandsia macropetala in a fragment of humid montane forest in central Veracruz, Mexico.

Methods

The reproductive system of the species, duration of anthesis, production of nectar and floral scent, as well as diurnal and nocturnal floral visitors and their effectiveness in pollination were determined.

Key Results

Tillandsia macropetala is a self-compatible species that achieves a higher fruit production through outcrossing. Nectar production is restricted to the night, and only nocturnal visits result in the development of fruits. The most frequent visitor (75 % of visits) and the only pollinator of this bromeliad (in 96 % of visits) was the nectarivorous bat Anoura geoffroyi (Phyllostomidae: Glossophaginae).

Conclusions

This is the first report of chiropterophily within the genus Tillandsia. The results on the pollination biology of this bromeliad suggest an ongoing evolutionary switch from pollination by birds or moths to bats.     

Reproductive biology of the andromonoecious Cucumis melo subsp. agrestis (Cucurbitaceae)

Background and Aims

Cucumis melo subsp. agrestis (Cucurbitaceae) is cultivated in many African regions for its edible kernels used as a soup thickener. The plant, an annual, andromonoecious, trailing-vine species, is of high social, cultural and economic value for local communities. In order to improve the yield of this crop, the first step and our aim were to elucidate its breeding system.

Methods

Eight experimental pollination treatments were performed during three growing seasons to assess spontaneous selfing, self-compatibility and effects of pollen source (hermaphroditic vs. male flowers). Pollination success was determined by pollen tube growth and reproductive success was assessed by fruit, seed and seedling numbers and characteristics. The pollinator guild was surveyed and the pollination distance determined both by direct observations and by indirect fluorescent dye dispersal.

Key Results

The species is probably pollinated by several Hymenoptera, principally by Hypotrigona para. Pollinator flight distances varied from 25 to 69 cm. No evidence for apomixis or spontaneous self-pollination in the absence of insect visitors was found. The self-fertility index (SFI = 0) indicated a total dependence on pollinators for reproductive success. The effects of hand pollination on fruit set, seed number and seedling fitness differed among years. Pollen tube growth and reproductive success did not differ between self- and cross-pollinations. Accordingly, a high self-compatibility index for the fruit set (SCI = 1·00) and the seed number (SCI = 0·98) and a low inbreeding depression at all developmental stages (cumulative δ = 0·126) suggest a high selfing ability. Finally, pollen origin had no effect on fruit and seed sets.

Conclusions

This andromonoecious species has the potential for a mixed mating system with high dependence on insect-mediated pollination. The selfing rate through geitonogamy should be important.     

The ancient tropical rainforest tree Symphonia globulifera L. f. (Clusiaceae) was not restricted to postulated Pleistocene refugia in Atlantic Equatorial Africa

Understanding the history of forests and their species'' demographic responses to past disturbances is important for predicting impacts of future environmental changes. Tropical rainforests of the Guineo-Congolian region in Central Africa are believed to have survived the Pleistocene glacial periods in a few major refugia, essentially centred on mountainous regions close to the Atlantic Ocean. We tested this hypothesis by investigating the phylogeographic structure of a widespread, ancient rainforest tree species, Symphonia globulifera L. f. (Clusiaceae), using plastid DNA sequences (chloroplast DNA [cpDNA], psbA-trnH intergenic spacer) and nuclear microsatellites (simple sequence repeats, SSRs). SSRs identified four gene pools located in Benin, West Cameroon, South Cameroon and Gabon, and São Tomé. This structure was also apparent at cpDNA. Approximate Bayesian Computation detected recent bottlenecks approximately dated to the last glacial maximum in Benin, West Cameroon and São Tomé, and an older bottleneck in South Cameroon and Gabon, suggesting a genetic effect of Pleistocene cycles of forest contraction. CpDNA haplotype distribution indicated wide-ranging long-term persistence of S. globulifera both inside and outside of postulated forest refugia. Pollen flow was four times greater than that of seed in South Cameroon and Gabon, which probably enabled rapid population recovery after bottlenecks. Furthermore, our study suggested ecotypic differentiation—coastal or swamp vs terra firme—in S. globulifera. Comparison with other tree phylogeographic studies in Central Africa highlighted the relevance of species-specific responses to environmental change in forest trees.     

Volatiles associated with different flower stages and leaves of Acacia cyclops and their potential role as host attractants for Dasineura dielsi (Diptera: Cecidomyiidae)

Acacia cyclops (Fabaceae) is an Australian species which was introduced into South Africa in the nineteenth century. Because of its invasive status in South Africa, a gall midge, Dasineura dielsi (Diptera: Cecidomyiidae), was released in 2001 in order to impact its reproduction by inducing galls on the flowers and thereby preventing seed set. Nothing is known about the cues used by D. dielsi for locating its host flowers. As part of an initial investigation into whether or not chemical cues might play a role in host finding, we analysed headspace samples of Acacia cyclops volatiles from leaves and reproductive parts at different stages (early bud, late bud, early flowering, and senescing flowering stages) using gas chromatography–mass spectrometry (GC–MS). In total, 72 different compounds were detected of which 62 were identified. The analyses showed that open flowers, the stage used by D. dielsi for oviposition, and yellow buds had similar odour compositions with (Z)-3-hexen-1-ol acetate, 4-oxoisophorone, (Z)-β-ocimene, an unknown aliphatic compound, heptadecane, and nonadecane dominating in open flowers. Leaf volatiles were distinct from those in the reproductive plant parts by their high relative amount of (Z)-β-ocimene. (Z)-3-Hexen-1-ol acetate had its maximum relative amount in the green bud samples and was much lower in the later floral stages. In contrast, 4-oxoisophorone peaked in yellow buds and open flowers with little or none of it found in younger or older stages. The volatile compounds of the different flower stages and leaves are discussed in relation to their potential role as attractants used by the biocontrol agent D. dielsi to locate its host plant.     

Vigna unguiculata is nodulated in Spain by endosymbionts of Genisteae legumes and by a new symbiovar (vignae) of the genus Bradyrhizobium

Vigna unguiculata was introduced into Europe from its distribution centre in Africa, and it is currently being cultivated in Mediterranean regions with adequate edapho-climatic conditions where the slow growing rhizobia nodulating this legume have not yet been studied. Previous studies based on rrs gene and ITS region analyses have shown that Bradyrhizobium yuanmingense and B. elkanii nodulated V. unguiculata in Africa, but these two species were not found in this study. Using the same phylogenetic markers it was shown that V. unguiculata, a legume from the tribe Phaseolae, was nodulated in Spain by two species of group I, B. cytisi and B. canariense, which are common endosymbionts of Genisteae in both Europe and Africa. These species have not been found to date in V. unguiculata nodules in its African distribution centres. All strains from Bradyrhizobium group I isolated in Spain belonged to the symbiovar genistearum, which is found at present only in Genisteae legumes in both Africa and Europe. V. unguiculata was also nodulated in Spain by a strain from Bradyrhizobium group II that belonged to a novel symbiovar (vignae). Some African V. unguiculata-nodulating strains also belonged to this proposed new symbiovar.     

Why Africa matters: evolution of Old World Salvia (Lamiaceae) in Africa

Background and Aims

Salvia is the largest genus in Lamiaceae and it has recently been found to be non-monophyletic. Molecular data on Old World Salvia are largely lacking. In this study, we present data concerning Salvia in Africa. The focus is on the colonization of the continent, character evolution and the switch of pollination systems in the genus.

Methods

Maximum likelihood and Bayesian inference were used for phylogenetic reconstruction. Analyses were based on two nuclear markers [internal transcribed spacer (ITS) and external transcribed spacer (ETS)] and one plastid marker (rpl32-trnL). Sequence data were generated for 41 of the 62 African taxa (66 %). Mesquite was used to reconstruct ancestral character states for distribution, life form, calyx shape, stamen type and pollination syndrome.

Key Results

Salvia in Africa is non-monophyletic. Each of the five major regions in Africa, except Madagascar, was colonized at least twice, and floristic links between North African, south-west Asian and European species are strongly supported. The large radiation in Sub-Saharan Africa (23 species) can be traced back to dispersal from North Africa via East Africa to the Cape Region. Adaptation to bird pollination in southern Africa and Madagascar reflects parallel evolution.

Conclusions

The phenotypic diversity in African Salvia is associated with repeated introductions to the continent. Many important evolutionary processes, such as colonization, adaptation, parallelism and character transformation, are reflected in this comparatively small group. The data presented in this study can help to understand the evolution of Salvia sensu lato and other large genera.     

Floral and macroecological evolution within Cyrtanthus (Amaryllidaceae): Inferences from combined analyses of plastid ndhF and nrDNA ITS sequences

One of the most diverse members of Amaryllidaceae is Cyrtanthus Aiton, a large, sub-Saharan Africa genus of approximately 55 species found mostly in South Africa. To investigate phylogenetic and biogeographic relationships within Cyrtanthus, sequence data from the plastid ndhF gene and the ITS nrDNA region for 41 species were analyzed with parsimony, maximum likelihood, and Bayesian-inference approaches. Various recombination detection algorithms were used to test for interspecific hybridization in the ITS alignment. The genus resolved as monophyletic, comprising three poorly to well-supported major lineages: a predominantly Afrotemperate lineage, largely restricted to seasonally moist sites in summer rainfall southern Africa, a subtropical lineage found mostly in nonseasonal rainfall regions, often in dry habitats, and a Cape Floristic Region-centered lineage in which most species are concentrated in the summer-dry to nonseasonal rainfall southwest. The ITS sequence alignment shows no evidence for reticulation between any of the species. Relationships inferred by the molecular data disagree with those derived from morphological data, but agree with previously published groupings based on karyotype morphology. Fitch optimization of selected floral characters on the combined gene tree reveals recurrent patterns of convergence. Ornithophilous floral forms occur in parallel among the three primary clades, putatively sphingophilous species are concentrated in the Afrotemperate lineage in seasonally moist upland grasslands; the brush-type Aeropetes tulbaghia butterfly and inferred long-proboscid fly pollination syndromes are unique in the Cape lineage. Macroecological factors inferred to have influenced the evolution of Cyrtanthus are changes in rainfall seasonality, the advent of fire, and the availability of new habitats at high and low altitudes and in rock-free soils or rock crevices. This study gives greater clarity on relationships within the genus and enables its division into three informal infrageneric groups.     

A new species of Combretum section Ciliatipetala (Combretaceae) from southern Africa, with a key to the regional members of the section

Combretum stylesii O.Maurin, Jordaan & A.E.van Wyk, a liana or slender tree with scrambling branches from the Tugela River Valley (KwaZulu-Natal), South Africa, is described. Molecular data supports its placement in subgenus Combretum section Ciliatipetala with its closest relative Combretum edwardsii. The new species differs from C. edwardsii in having, amongst others, a single mature leaf form, leaves softly textured, with whitish hairs, often with drooping habit, shorter leaf petioles (less than 5 mm), and less complex 8-celled leaf scales. A key to the species and infraspecific taxa of section Ciliatipetala in the Flora of southern Africa region is provided.