Peter E. Gibbs

Patterns of species distributions in the dry seasonal forests of South America

Studies of the distributions of species of seasonal woodland habitats in South America by means of dot-mappung and phytosociological analyses indicate the presence of three nodal areas: the Caatingas nucleus of arid northeastern Brazil; the Misiones nucleus, comprising a roughly right-angled triangular area enclosed by lines connecting Corumba-Puerto Suarez (Brazil/Bolivia) southward to Resistencia-Corrientes in northern Argentina, and eastward to the upper Uruguay River valley system in Argentinian Misiones and Brazilian Santa Catarina, and thus including most of eastern Paraguay and the west bank of the Paraguay River; and the Piedmont nucleus, which extends from Santa Cruz de la Sierra in Boliva to Tucuman and the sierras of east Catamarca in northwestern Argentina

Reproductive biology of woody plants in a cerrado community of central Brazil.

Summary The flowering phenology, pollination biology and breeding systems of tree and shrub species were studied in a 40 h area of cerrado vegetation in Central Brazil. The cerrados are Neotropical savanna plant formations in Central Brazil. They represent the second most important vegetation province in Brazil and are nowadays the main agricultural frontier which has resulted in deforestation rates much higher than those occurring in lowland tropical forests. Despite the marked winter/dry − summer/wet seasonality, different species were encountered in flower throughout the year, although with a peak at the end of the dry season. Seven pollination guilds were identified, ranging from very small insects (body size less than 5 mm) to bats, but bee pollination was predominant, and overall pollination biology of the cerrado community was similar to that reported for evergreen neotropical forests. Most species were outbreeding in that self-pollinations yielded very few fruits, but heteromorphic and homomorphic self-incompatibility were rare and control of selfing was commonly exercised by ill-defined post-zygotic mechanisms. The results indicated that the reproductive biology of woody cerrado species is not markedly different from other tropical forest communities and suggested the adaptation to seasonal habitats did not always lead to simplification or changes in breeding features of the cerrado species.

Flowering phenology and pollination biology of Ceiba pentandra (Bombacaceae) in Central Amazonia

The flowering and fruiting phenology, floral biology, pollination ecology, and breeding system of the emergent tree Ceiba pentandra were studied in the Brazilian Central Amazon. Of the 21 trees studied, 17 flowered once or twice during the 6-y study period. The mass flowering and relatively high production of nectar per flower (mean of 310 μl) resulted in a high nectar production (over 200 l per tree per season). Flowers were visited by a wide range of nocturnal (bats, marsupials, night monkeys, hawk moths) and diurnal (bees, wasps, hummingbirds) animals, but only phyllostomid bats, especially Phyllostomus hastatus and Phyllostomus discolor , played a relevant role promoting cross-pollination. Pollinations which occurred in the early morning by diurnal floral visitors were ineffective since pollen tubes did not traverse the style and reach the ovary before stylar abscission. Despite the apparently normal growth of the self-pollen tubes, controlled pollinations carried out in one tree revealed no fruit set by selfing and 16.8% fruit set by crossing. Progeny analysis from this ‘self-incompatible’ tree using isozyme markers showed that fruits resulting from mixed-pollination (i.e., 50% self- plus 50% cross-pollen on the stigma) set only 1.6% of selfed seeds. The percentage of outcrossed seeds in fruits resulting from open-pollination in two neighbouring planted trees, which flowered in isolation and concomitantly, was estimated at 91% and 71%. Two isolated trees did not set any fruits despite massive flowering, whereas two others set large quantities of seed, supporting data in the literature stating that variable degrees of self-fertility may occur in this species. RESUMO. A fenologia de floracao e de frutificacao, a biologia floral, a ecologia de polinizacao e o sistema reprodutivo da arvore emergente Ceiba pentandra foram estudados na Amazonia Central Brasileira. Dezessete das 21 arvores estudadas (doze nativas e nove plantadas de sementes de procedencia desconhecida) floriram uma ou duas vezes cada uma durante os seis anos do estudo. A maior parte das arvores nativas floriu massivamente somente em 1993 e 1996, enquanto que algumas das arvores plantadas floriram massivamente somente em 1992 e 1997. A floracao massiva e a relativamente alta producao de nectar por flor (media de 310 μl de nectar secretado por flor por noite) resultaram em uma alta producao de nectar por arvore (mais de 200 l de nectar por arvore por estacao de floracao). As flores de C. pentandra foram visitadas por uma grande variedade de animais noturnos (morcegos, marsupiais, macacos-da-noite, mariposas) e diurnos (abelhas, vespas, beija-flores), mas somente morcegos, especialmente Phyllostomus hastatus e Phyllostomus discolor , parecem exercer papel relevante promovendo a polinizacao cruzada. Nao foram detectadas diferencas na capacidade dos tubos polinicos originados do auto-polem e do polem cruzado de se desenvolverem ate o ovario e penetrarem nos ovulos. Polinizacoes que ocorreram no inicio da manha foram inefetivas, uma vez que os tubos polinicos nao tiveram suficiente tempo para atravessarem o estilete antes da sua abscisao. Apesar do aparente desenvolvimento normal dos tubos polinicos oriundos do auto-polem, polinizacoes controladas executadas em uma arvore resultaram em nenhuma producao de frutos em flores auto-polinizadas e em 16,8% de producao de frutos nas flores que sofreram polinizacao cruzada. A producao natural de frutos (polinizacao aberta) na mesma arvore foi estimada em 0,7%. O uso de marcadores isoenzimaticos na analise genetica da progenie dessa mesma arvore ‘auto-incompativel’ revelou que, em frutos resultantes de polinizacoes mistas (isto e; uma mistura contendo 50% auto-polem e 50% polem cruzado, depositada no estigma), apenas cerca de 1,6% das sementes foram originadas por eventos de auto-fecundacao. A proporcao de sementes originadas por fecundacao cruzada em frutos formados naturalmente em duas arvores plantadas e vizinhas, que floriram isoladamente e concomitantemente em 1992, foi de 91% e 71%, respectivamente. Duas arvores isoladas nao produziram frutos, apesar de intensa floracao, enquanto que outras duas tambem isoladas frutificaram em abundância. Essas observacoes reforcam dados da literatura que indicam a ocorrencia de niveis muito variaveis de auto-fertilidade entre as arvores dessa especie.

Do homomorphic and heteromorphic self-incompatibility systems have the same sporophytic mechanism?

The view put forward by some authors that flowering plant self-incompatibility mechanisms of the homomorphic sporophytic and heteromorphic sporophytic types have a close evolutionary relationship, with one form being evolved from the other, or both forms directly evolved from ancestors with homomorphic gametophytic incompatibility, is challenged. A review is provided of the various facets of each of the three main self-incompatibility systems, including a detailed summary of our current knowledge of the rejection mechanism, to demonstrate that the implicit assumption that these systems have a common S locus, and also evolutionary theories linking the systems, need to be treated with considerable caution.

Reproductive biology ofCistus ladanifer (Cistaceae)

The phenology, major floral characteristics, fruiting levels, and breeding system ofCistus ladanifer L. (Cistaceae), a common western Mediterranean shrub species, were studied in a southern Spanish population. The white, large (64 mm in diameter) flowers of this shrub appear during spring (March–May) and produce abundant pollen and nectar. In the year of study, flowers lasted up to three days, during which they were visited by a diverse array of insects including beetles, flies, and bees. Hand-pollinations revealed that flowers do not set any seed unless cross pollen is applied to the stigma. Microscopical observations indicate that self pollen tubes grow down the stigma but invariably fail to induce fruit maturation. At the plant level, all estimates of fecundity investigated (number of seeds per capsule, proportion of ovules developing into seed, and proportion of flowers setting fruit) were highly dependent on nearest neighbour distance, with isolated plants setting as little as 0% fruit. In contrast, plants within a clump often transformed into fruit as much as 90% of the flowers. At the population level, seed output was estimated to range between 3,000 and 270,000 seeds per plant during 1991.

Contrasting breeding systems in twoEriotheca (Bombacaceae) species of the Brazilian cerrados

The pollination biology and breeding systems ofEriotheca pubescens andE. gracilipes have been studied. These two species occur as trees in cerrado vegetation, the neotropical savannas of Central Brazil, with partially sympatric distributions. They have similar phenology and floral structure, although the flowers ofE. pubescens are larger. Both species have nectar flowers pollinated by largeAnthophoridae bees but the main pollinators of each species differ in size. The species have markedly different breeding systems: late-acting self-incompatibility inE. gracilipes and apomixis stimulated by pollination inE. pubescens.

Postzygotic Control of Selfing in Hymenaea stigonocarpa (Leguminosae‐Caesalpinioideae), a Bat‐Pollinated Tree of the Brazilian Cerrados

The pollination biology and breeding system of Hymenaea stigonocarpa, a common tree of the Brazilian cerrados, were investigated. The flowers have nocturnal anthesis, produce copious nectar, and are visited by at least four species of bats, including the specialized nectivorous Glossophaga soricina and the less specialized frugivores Platyrhinus lineatus and Carollia perspicillata. Controlled hand‐pollination results indicate the species is basically allogamous. Almost all selfed flowers abscised within 7–8 d, but rejection was due to a postzygotic mechanism, since self‐pollen tubes grew to the ovary and penetrated ovules with equal facility to cross tubes, and selfed ovules at 5 d contained a zygote with endosperm nuclei. The causes of selfed pistil abscission were not established, but selfed ovules were smaller than crossed ones at every stage over the first 5 d postpollination, indicating an early recognition or differential development of selfed ovules.

Moth pollination of woody species in the Cerrados of Central Brazil: a case of so much owed to so few?

Abstract.We present a survey of moth pollination in woody species of the Cerrado of Central Brazil. Although with the exception of Roupalamontana (which has simple polysepalous flowers arranged in dense cymes) all moth pollinated species in this community have tubular flowers, or a pseudo-tube formed from a single folded petal in Qualeagrandiflora, settling moth flowers (tube less than 15 mm) vs. hawkmoth flowers (tube more than 50 mm) are markedly different in size. Moths visit some 20 woody Cerrado species, but they are probably effective pollinators of only 13 species or ca.14% of the woody taxa studied, and even in these latter species they are often very sparse visitors. Nevertheless, it is notable that moths are pollinators for 21% of the 38 most commonly distributed woody Cerrado species. Moreover, the reproductive efficacy of the studied moth pollinated species was similar to that of species pollinated by other kind of vectors.

Floristic Composition and Community Structure in an Area of Cerrado in SE Brazil

Summary Cerrado is the generic name for the savanna-like vegetation which occupies the vast area of the central Brazilian plateau and also extends into peripheral, fragmented islands within the Surrounding moist forests. Cerrado occurs as a complex of intergrading structural sub-types which range from more or less closed forest to open grassland with scattercd shrubs, and it also shows phytogeographical shifts in floristic composition although these are as yet poorly studied. This investigation presents for the first time a full list of the woody species from one of the peripheral islands of cerrado in Sao Paulo state. In addition, a principal components analysis of the data from 60 quadrats of 10 × 25 m indicates that the two community subtypes present in this area, cerrado and campo cerrado , distinguished by Goodland on the basis of physiognomic characteristics, can also be defined in terms of species composition. The possible causes for these floristic and physiognomic sub-communities are examined but no single controlling factor can be established.

High Outbreeding as a Consequence of Selfed Ovule Mortality and Single Vector Bat Pollination in the Amazonian Tree Pseudobombax munguba (Bombacaceae)

The pollination biology and breeding system of Pseudobombax munguba, a tree species of the várzea of the Amazonian floodplain, was studied by field observations and hand pollinations using varying proportions of self and cross pollen. Progeny in sample fruits were tested for self or cross paternity using an isozyme genetic marker. Pseudobombax munguba has nocturnal, white, brushlike flowers that, surprisingly, lack nectar, and they are pollinated by a single, large bat species, Phyllostomus hastatus. Although self pollen tubes penetrated ovules with equal facility to cross tubes, fully selfed flowers failed to form fruits. Flowers with mixed ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape