Agouticarpa, a new neotropical genus of Tribe Gardenieae (Rubiaceae)

Agouticarpa, a new genus of the informalAlibertia group (Rubiaceae), is described and illustrated. It comprises six species, and occurs from Costa Rica to Bolivia. Three species are here described as new:Agouticarpa grandistipula, A. hirsuta, andA. velutina. Additionally, three new combinations are made:A. curvifolia andA. williamsii (previously inGenipa) andA. isernii (previously inAlibertia). Agouticarpa is characterized by being dioecious, having elliptic to abovate, membranaceous stipules, male flowers in a branched dichasial or thyrse-like inflorescence, a poorly developed cup-shaped calyx, pollen grains with 3–7 apertures, and large globose fruits.     

Hybrid speciation and radiation in the neotropical woody genusTocoyena (Rubiaceae)

The variation pattern of a large population ofTocoyena formosa in Botucatu, state of São Paulo, Brazil, and of other samples throughout the species area was analysed by morphometrical, statistical, ecological, and phytogeographical methods. Excessive variation and the remarkable coherence of two different character syndromes within this species strongly suggest that it has originated as a homogamic (diploid) hybrid complex. Possible parental species areT. brasiliensis, mainly from the Amazon region, andT. viscidula from the dry caatinga region of NE. Brazil.T. formosa has a much more extensive geographical range and greater ecological plasticity, ranging from the Amazon basin and the Guyanas throughout the Central Brazilian Plateau and from NE. to S. Brazil and Paraguay. Three (partly sympatric) varieties are distinguished withinT. formosa, i.e. var.formosa, var.pseudobrasiliensis (var. nov.), and var.microdon (comb. et stat. nov.). A provisional taxonomic revision, key, and conspectus covers the 12 accepted species ofTocoyena with blunt flower buds and ovate obtuse corolla lobes (group A, includingT. formosa); their distribution is shown in a map.     

Distyly and sequential pollinators of Psychotria nuda (Rubiaceae) in the Atlantic rain forest, Brazil

Reciprocal herkogamy is known to promote intermorph-pollination in distylous species, which are generally self- and intramorph-incompatible. Legitimate crossing rates are also influenced by pollinator foraging strategy, which determines most of the pollen flow in natural populations. This study reports on the floral morphology, compatibility relations and pollination biology of Psychotria nuda (Cham. and Schltdl.) Wawra in the Atlantic rain forest, southeastern Brazil, based on floral measurements, hand-pollination experiments and focal observation of floral visitors. It was found that P. nuda does not present an exactly reciprocal herkogamy, however, this morphological trait in P. nuda is as good as in most of Rubiaceae. Reproductive experiments showed compatibility relations similar to those frequently observed in distylous species. The hummingbirds Ramphodon naevius and females of Thalurania glaucopis were the main pollinators of P. nuda, presenting the traplining foraging strategy, which seems to maximize intermorph crosses in P. nuda flowers. These hummingbirds pollinated P. nuda flowers sequentially throughout the flowering period.     

Correlation between time of flowering and phenotypic plasticity in Arabidopsis thaliana (Brassicaceae)

We observed substantial variation in the time of flowering among 13 populations of Arabidopsis thaliana (Brassicaceae) from an extensive latitudinal range when grown under uniform experimental conditions. The later the onset of flowering, the greater was potential reproduction. Later flowering plants also had greater plasticity in a host of morphological and physiological traits measured in nutrient-rich vs. nutrient-poor test environments. This relationship between flowering time and overall plasticity was only apparent for traits measured at the time of seed production, not at the time of flowering or earlier. At the time of seed production in this short-lived annual, the regression of a multivariate measure of overall plasticity on the time of flowering was linear and highly significant (r² = 0.90, P < 0.0001). These correlations among time of flowering, reproductive fitness, and plasticity support the idea that selection for late-flowering genotypes would select concomitantly for greater plasticity.     

<Emphasis Type="Italic">Pentagonia lanciloba</Emphasis>, a new species of Rubiaceae (Hippotideae) from northwestern Ecuador

Pentagonia lanciloba, a new species of Rubiaceae (Hippotideae) from the wet forests of northwestern Ecuador, is described. This new species is characterized by pinnatifid leaf blades with tapered and long-decurrent subsessile bases, floral bracts with long-acuminate to caudate apices, calyces with narrowly-lanceolate and remarkably long lobes (15–28 mm), and tomentose, orange to red corollas. The new species is illustrated, and its relationship to morphologically similar species is discussed.     

Size-dependent flowering behavior and heat production of a sequential hermaphrodite, Symplocarpus renifolius (Araceae)

We examined the flowering performance in a population of the protogynous perennial herb Symplocarpus renifolius (Araceae), with special consideration of plant size. Flowering of S. renifolius occurred in very early spring, soon after snow melt. The spadices generated heat throughout the pistillate (female) and bisexual phases, but heat production decreased quickly after the beginning of the staminate (male) phase. During the flowering season, the sex ratio within the population dramatically changed from a dominance of females to a dominance of males. The duration of the female phase was negatively correlated with the onset time of flowering, and the duration of the male phase was positively correlated with plant size. Larger plants began blooming earlier, produced more heat, made the transition from female to male phase more rapidly, and lasted longer as males than smaller ones. Such size-dependent flowering performance caused unidirectional pollen flow from large to small plants. The number of seeds produced per spadix was positively correlated with the duration of the female phase, although it was not correlated with plant size. However, the estimated number of seeds sired during the male phase was positively correlated with plant size. Early flowering, rapid gender change, and higher heat production of the spadices by larger plants were factors considered to promote the higher success of the male function without decreasing the success of the female function.     

Ovary,seed and fruit ofRutidea (Rubiaceae,Pavetteae)

The ovary ofRutidea is bicarpellate and incompletely bilocular (septum between locules not continuous). A solitary campylotropous ovule, ascending from a basal placenta, occurs in each locule. Based on their orientation and degree of curving, three ovule types are distinguished. As a consequence of the abortion of one ovule, the drupaceous fruits are one-seeded. The incomplete septum allows the spherical seed to fill out the entire interior of the fruit. The seeds are deeply ruminate (Spigelia type). They grow very fast, producing folds and undulations (ruminations) which invade and totally occupy the second locule, almost enveloping the aborted ovule. Comparisons with otherRubiaceae (especiallyPavetteae), show that hemianatropy and campylotropy occur more often in theRubiaceae than hitherto accepted. The study corroborates the close affinity betweenRutidea andNichallea.     

Ethnobotany, phytochemistry and pharmacology of Uncaria (Rubiaceae)

The Uncaria genus is an important source of medicinal natural products, particularly alkaloids and triterpenes. The collected information is an attempt to cover the more recent developments in the ethnobotany, pharmacology and phytochemistry of this genus. During the past 20 years, alkaloids, terpenes, quinovic acid glycosides, flavonoids and coumarins have been isolated from Uncaria. Fifty-three novel structures are reported in this review. The species in which the largest number of compounds has been identified is the Peruvian Uncaria tomentosa or 'cat's claw.' Pharmacological studies are described according to cytotoxicity, anti-inflammatory, antiviral, immunostimulation, antioxidant, CNS-related response, vascular, hypotensive, mutagenicity and antibacterial properties. The potential for development of leads from Uncaria continues to grow, particularly in the area of immunomodulatory, anti-inflammatory and vascular-related conditions. The information summarized here is intended to serve as a reference tool to practitioners in the fields of ethnopharmacology and natural products chemistry.     

Taxonomic novelties and changes in Philippine Timonius (Rubiaceae,Guettardeae)

The Philippine species of the genus Timonius present numerous taxonomic problems resulting from poorly defined species boundaries, misinterpretation of the origin of type specimens, and historical collections that often bear residual reproductive structures. Based on field observations and examination of herbarium materials, the following taxonomic amendments are proposed: conspecificity of T. philippinensis with T. finlaysonianus, and T. panayensis with T. valetonii, and transfer of T. quadrasii to Ridsdalea. This study also describes six new species from the archipelago: T. alejandroanus, T. dumagat, T. pseudoarboreus, T. ridsdalei, T. spes-vitarum and T. stevendarwinii. Finally, T. nitidus is excluded from the Philippine flora.     

Self-compatibility in distylousHedyotis salzmannii (Rubiaceae)

Hedyotis salzmannii (Rubiaceae) is distylous. Experimental pollination revealed that both morphs are self-compatible. However, the thrum morph proved to be more self-compatible. Hand cross-pollination between different plants of the same floral form produced less seed-sets per pollination than hand cross-pollination between pin and thrum or thrum and pin pollination. Two species ofHymenoptera, oneApidae and oneHalictidae, and two species ofDiptera (Syrphidae) were observed as pollinators.     

Positive density dependence in seedlings of the neotropical tree species Garcinia macrophylla and Xylopia micans

Question: The Janzen‐Connell hypothesis predicts that herbivores and pathogens prevent seedlings from establishing in dense patches near adult conspecifics. Although many studies have investigated the Janzen‐Connell hypothesis, the environmental context – local or regional – in which juveniles establish is often overlooked. The objectives of this study were: (1) to evaluate Janzen‐Connell effects in contrasting environments, and (2) to incorporate microsite variation into the study of this hypothesis. Location: Pacaya‐Samiria Reserve, Peru. Methods: I assessed seedling performance of two tree species, Garcinia macrophylla and Xylopia micans, during one growing season. In an observational study, mortality and growth rates were regressed against distance to the nearest adult conspecific, conspecific seedling density, heterospecific plant density, and several abiotic variables in upland and floodplain forests. Field and shadehouse experiments were used to isolate distance‐ and density‐dependent effects. Results: Contrary to predictions, seedling survivorship increased in the presence of conspecific seedlings (Garcinia) and heterospecific understory plants (Garcinia and Xylopia) in the observational study. Survivorship in the field experiment, however, was unaffected by conspecific seedling density or adult proximity. In the shadehouse, Garcinia growth rates were highest in floodplain soils collected near adult conspecifics, but mortality was unrelated to the soil's habitat or proximity to an adult. Conclusions: The positive density dependence found in this study could have been produced by: (1) environmental factors that increase both density and survivorship, or (2) interspecific facilitation, if heterospecifics reduce herbivore or pathogen pressure on the focal species. Such interactions could help explain species coexistence in tropical forests.     

New species and combinations in Houstonia (Rubiaceae)

Two new species are described:Houstonia butterwickiae from Texas andH. teretifolia from Mexico, and two new combinations are made:H. acerosa subsp.polypremoides andH. mullerae.     

Revision and affinities ofGalium (Rubiaceae) in Madagascar

The only representatives ofRubiaceae-Rubieae in Madagascar are five species ofGalium. G. thunbergianum andG. chloroionanthum are essentially afromontane species, ± widely distributed in both the African mainland and Madagascar. The new speciesG. andringitrense andG. ankaratrense are endemic to Madagascar but show close affinities to two afromontane—afroalpine groups from the African mainland, theG. simense—G. ruwenzoriense andG. glaciale complex respectively.G. polyacanthum (new combination) exhibits certain primitive morphological traits and appears to be an old Madagascan endemic without close allies. New chromosome counts for populations from the African mainland demonstrate thatG. chloroionanthum andG. simense are 4x (x=11). Distribution patterns and origins of theGalium species in Madagascar and their relationships with African taxa are discussed.     

Photochemical efficiency of adult and young leaves of the neotropical understory shrub Psychotria limonensis (Rubiaceae) in response to changes in the light environment

We explored the short-term adjustment in photochemical efficiency (Fv/Fm) in adult and young leaves of the understory neotropical shrub Psychotria limonensis Krause (Rubiaceae) in response to rapid changes in the light environment. Leaves were collected from 20 individual plants growing under sun and shade conditions on Gigante Peninsula, Barro Colorado Natural Monument (Republic of Panama), during the wet season of 1996. Leaves were distributed in four sequences of light treatments (AB leaves were expanded under sun and were transferred to shade, BA leaves experienced the opposite transfer, and the controls AA and BB leaves that were expanded and maintained under sun or shade conditions). Adult and young leaves did not differ in overall photochemical efficiency. Instead, differences were found among light environments, for which leaves transferred from shade to sun showed the lowest Fv/Fm ratios. There was no relationship between photochemical efficiency and leaf temperature. In P. limonensis, understory plants are susceptible of photoinhibition independently of the leaf ontogenetic stage. The approach utilized in this experiment allowed the rapid exploration of this capacity, and could be applied to poorly studied understory species.     

Asperula calabra (Rubiaceae) and allied taxa in southern Apennines,Italy

The present work is aimed at studying several Asperula (Rubiaceae) sect. Cynanchicae populations in southern Apennines, Italy, with particular reference to those referred to A. calabra, by employing biometrical methods on macromorphological data. Among other historical misapplications, A. cynanchica subsp. cynanchica seems to be very rare or missing in southern Italy. The enigmatic Asperula calabra, confirmed to be limited to a single mountain population in Calabria, appears to be strictly related to A. aristata subsp. scabra, so we suggest to treat it as a further subspecies of A. aristata. This latter species is otherwise distributed throughout southern Italy with subsp. scabra and subsp. aristata, characterised by slight morphological differences, which are correlated to altitudinal ranges.