The role of individual variation in flowering and pollination in the reproductive success of a crepuscular buzz-pollinated plant

Background and AimsPlant individuals within a population differ in their phenology and interactions with pollinators. However, it is still unknown how individual differences affect the reproductive success of plants that have functionally specialized pollination systems. Here, we evaluated whether plant individual specialization in phenology (temporal specialization) and in pollination (pollinator specialization) affect the reproductive success of the crepuscular-bee-pollinated plant Trembleya laniflora (Melastomataceae).MethodsWe quantified flowering activity (amplitude, duration and overlap), plant–pollinator interactions (number of flowers visited by pollinators) and reproductive success (fruit set) of T. laniflora individuals from three distinct locations in rupestrian grasslands of southeastern Brazil. We estimated the degree of individual temporal specialization in flowering phenology and of individual specialization in plant–pollinator interactions, and tested their relationship with plant reproductive success.Key Results Trembleya laniflora presented overlapping flowering, a temporal generalization and specialized pollinator interactions. Flowering overlap among individuals and populations was higher than expected by chance but did not affect the individual interactions with pollinators and nor their reproductive success. In contrast, higher individual generalization in the interactions with pollinators was related to higher individual reproductive success.ConclusionsOur findings suggest that individual generalization in plant–pollinator interaction reduces the potential costs of specialization at the species level, ensuring reproductive success. Altogether, our results highlight the complexity of specialization/generalization of plant–pollinator interactions at distinct levels of organization, from individuals to populations, to species.     

Taxonomic studies in the Miconieae (Melastomataceae). IX. Calycogonium formonense, a new species from the Massif de la Hotte, Haiti

Calycogonium formonense, a new species, is here described from the floristically diverse Massif de la Hotte of southern Haiti. It is compared to C. hispidulum, to which it is likely related. Although the genus Calycogonium is not monophyletic, C. formonense and C. hispidulum are probably related to other species, e.g., C. calycopteris, C. heterophyllum, and C. reticulatum, that exhibit reduced inflorescences and 4-merous flowers having hypanthia with four conspicuous lobes separated by longitudinal grooves and external calyx lobes that are flattened parallel to the floral radii. These distinctive species may form a clade. Calycogonium formonense is distinguished from C. hispidulum by its smaller leaves with the tertiary veins not raised on the abaxial surface, with entire margins (i.e., margin without elongate multicellular hairs), and usually solitary flowers.     

Observations on the Reproductive Biology of Miconia calvescens DC (Melastomataceae), an Alien Invasive Tree on the Island of Tahiti (South Pacific Ocean)1

Miconia calvescens DC (Melastomataceae) is a dominant invasive species in the tropical oceanic island of Tahiti (French Polynesia, South Pacific Ocean), where it was introduced as an ornamental plant. Whereas this small tree is sparse in its native range of Central America, it has spread in Tahiti into a wide variety of habitats including native wet forests. The remarkable success of this invasion is due in great part to prolific reproduction: a mature tree can bear up to 220 inflorescences with an average of 1330 flowers/inflorescence, 208 fruits/infructescence and 195 seeds/fruit. Two and a half years of phenological observations in a highly invaded site indicated that three major peaks of flowering occur/year over brief periods: flower anthesis lasted a few days and pollen grain germination suggested a short stigmatic receptivity of only a few hours; no pollinators were observed foraging on flowers during our survey; the production of fruits containing viable seeds in bagged inflorescences showed that self-fertilization can occur; pollen-ovule ratio (log P/O = 2.68) suggested facultative xenogamy; bagged isolated flowers to test for autogamy and style cutting to learn whether apomixis occured or not were not conclusive. The flowering phenology and the breeding system of M. calvescens enable this plant to build up rapidly successful populations from even a single propagule on the island of Tahiti and on other sites of introduction. The vegetation structure of Polynesian native forests compared to Neotropical rain forests probably plays an important role in determining the reproductive success of M. calvescens and could provide a complementary explanation of the biological invasion processes in tropical oceanic islands.     

Using geometric morphometrics to determine the “fittest” floral shape: A case study in large-flowered,buzz-pollinated Meriania hernandoi

Premise

Floral shape (relative arrangement and position of floral organs) is critical in mediating fit with pollinators and maximizing conspecific pollen transfer particularly in functionally specialized systems. To date, however, few studies have attempted to quantify flowers as the inherently three-dimensional (3D) structures they are and determine the effect of intraspecific shape variation on pollen transfer. We here addressed this research gap using a functionally specialized system, buzz pollination, in which bees extract pollen through vibrations, as a model. Our study species, Meriania hernandoi (Melastomataceae), undergoes a floral shape change from pseudocampanulate corollas with more actinomorphically arranged stamens (first day) to open corollas with a more zygomorphic androecium (second day) over anthesis, providing a natural experiment to test how variation in floral shape affects pollination performance.

Methods

In one population of M. hernandoi, we bagged 51 pre-anthetic flowers and exposed half of them to bee pollinators when they were in either stage of their shape transition. We then collected flowers, obtained 3D flower models through x-ray computed tomography for 3D geometric morphometric analyses, and counted the pollen grains remaining per stamen (male pollination performance) and stigmatic pollen loads (female pollination performance).

Results

Male pollination performance was significantly higher in open flowers with zygomorphic androecia than in pseudo-campanulate flowers. Female pollination performance did not differ among floral shapes.

Conclusions

These results suggest that there is an “optimal” shape for male pollination performance, while the movement of bees around the flower when buzzing the spread-out stamens results in sufficient pollen deposition regardless of floral shape.

     

Phylogeny and systematics of the tribe Sonerileae (Melastomataceae) in Africa: A revised taxonomic classification

The tribe Sonerileae in tropical Africa and Madagascar is a morphologically diverse lineage that consists of 239 species in 10 genera. In this study, we present the first in-depth phylogenetic analysis of African Sonerileae to test monophyly of the currently recognized genera. Phylogenetic analyses were performed using sequence data from two nuclear (nrITS and nrETS) and three plastid loci (accD-psaI, ndhF and psbK-psbL). Sampling consisted of 140 accessions including 64 African, 27 Malagasy, 46 Asian, and three neotropical Sonerileae together with a broad outgroup sampling (105 spp.). Phylogenetic relationships were inferred using maximum likelihood and Bayesian inference approaches, and a careful reassessment of morphological characters was carried out. Our results neither support the monophyly of the Old World nor African Sonerileae. The monospecific African genus Benna is partially supported as sister to Phainantha, one of the basal neotropical lineages, while African and Malagasy Medinilla are nested among the SE Asian genera. Gravesia (116 spp.), the most species-rich and morphologically diverse genus in Madagascar, is recovered as monophyletic. The African genera of Sonerileae Calvoa, Dicellandra, and Preussiella form well-supported clades. In contrast, Amphiblemma (including Amphiblemma molle) and Cincinnobotrys s.l. (including Cincinnobotrys felicis) are not monophyletic. To accommodate the caulescent C. felicis we propose reinstatement of the monospecific genus Bourdaria. For the distinctive A. molle a new genus Mendelia is described. Calvoa hirsuta is designated here as the type of genus Calvoa, lectotypes are designated for Medinilla engleri and Veprecella lutea, and a neotype is designated for Preussiella kamerunensis.     

Frugivory and seed dispersal in a hyperdiverse plant clade and its role as a keystone resource for the Neotropical fauna

Background and AimsMuch of our understanding of the ecology and evolution of seed dispersal in the Neotropics is founded on studies involving the animal-dispersed, hyperdiverse plant clade Miconia (Melastomataceae). Nonetheless, no formal attempt has been made to establish its relevance as a model system or indeed provide evidence of the role of frugivores as Miconia seed dispersers.MethodsWe built three Miconia databases (fruit phenology/diaspore traits, fruit–frugivore interactions and effects on seed germination after gut passage) to determine how Miconia fruiting phenology and fruit traits for >350 species interact with and shape patterns of frugivore selection. In addition, we conducted a meta-analysis evaluating the effects of animal gut passage/seed handling on Miconia germination.Key Results Miconia produce numerous small berries that enclose numerous tiny seeds within water- and sugar-rich pulps. In addition, coexisting species provide sequential, year long availability of fruits within communities, with many species producing fruits in periods of resource scarcity. From 2396 pairwise interactions, we identified 646 animal frugivore species in five classes, 22 orders and 60 families, including birds, mammals, reptiles, fish and ants that consume Miconia fruits. Endozoochory is the main dispersal mechanism, but gut passage effects on germination were specific to animal clades; birds, monkeys and ants reduced seed germination percentages, while opossums increased it.ConclusionsThe sequential fruiting phenologies and wide taxonomic and functional diversity of animal vectors associated with Miconia fruits underscore the likely keystone role that this plant clade plays in the Neotropics. By producing fruits morphologically and chemically accessible to a variety of animals, Miconia species ensure short- and long-distance seed dispersal and constitute reliable resources that sustain entire frugivore assemblages.     

A new species of Henriettea (Melastomataceae) from the Sierra de Baoruco, the Dominican Republic

Henriettea uniflora, which is known only from a diverse moist montane forest in the vicinity of Loma Trocha de Pey (or “Monteada Nueva”), Loma Pie de Palo, and Loma Remigio, the easternmost peaks of the Sierra de Baoruco, is described and illustrated. It is compared to species of the Henriettea squamulosa complex, especially H. squamulosa and H. ciliata. The species of this complex are characterized by an indumentum of ferruginous, stellate-lepidote hairs.