Carlos Roberto Fonseca

ABIOTIC FACTORS AND THE CONDITIONAL OUTCOME OF AN ANT–PLANT MUTUALISM

Mutualisms are inserted in a network of direct and indirect biotic interactions built within the framework imposed by the abiotic setting. We carried out an experiment to test how the availability of light and nutrients modulates the interaction strength between Inga vera (Mimosoideae), a Neotropical extrafloral-nectary-bearing plant, and its associated ants. From July 2001 to July 2003, 48 plants were grown in an old-field site following a three-factor randomized blocked design where treatments were: ant (ants present and absent), nutrient (without and with nutrient addition), and light (sun and shade). During the experiment, in the absence of ants, plants growing in sunlight were shorter, developed fewer leaves and leaflets, were more damaged by herbivores, had half the total dry biomass, and died more frequently than plants visited by ants. In contrast, ants had no effect on the growth, survival, and total biomass of shaded plants. Therefore small-scale heterogeneity in the light environment turned mutualism (+,+) into commensalism (+,0). This study demonstrates experimentally that the outcome of mutualistic interactions can be conditional upon the abiotic setting.

Amazonian ant-plant interactions and the nesting space limitation hypothesis

Throughout the tropics there are a few hundred ant species that nest exclusively inside myrmecophytes (i.e. ant-domatia bearing plants). For these ants, nesting space is an essential resource that must be shared among them, therefore opening the possibility for strong intraspecific and interspecific competition. Sev- eral ant-myrmecophyte systems from Central Amazonia were investigated to test the relevance and generality of the nesting space limitation hypothesis for plant- ants. Empirical patterns were drawn at four organizational levels: (a) individual level-ant species with small-bodied queens were the most frequent partners of myrmecophyte species offering small-sized domatia, while ants with large-bodied queens dominated host species with large-sized domatia, suggesting that host choice by inseminated queens and interspecific conflicts over host dominance seem to be influenced by space limitation; (b) colony level-in eight independent ant- myrmecophyte systems, ant colony size was positively correlated to the number of domatia provided by the host, and the mean occupancy level of the domatia by ants was 92%, suggesting that space can be limiting to colony growth; (c) popula- tion level-ant colony number and distribution was determined by the local avail- ability and distribution of its plant partners; and (d) community level-across ant-myrmecophyte systems, the commonness of ant species were largely deter- mined by the commonness of their specialized host partners. Within ant- myrmecophyte systems, rarity of ants seems to be defined by interspecific conflicts over host dominance. The ecological and evolutionary consequences of those pat- terns are discussed. RESUMO. Nos tropicos existem algumas poucas centenas de especies de formigas que nidificam exclusivamente dentro de mirmecofitas (i.e. plantas possuidoras de domaicias). Para estas formigas, o espaSo de nidificaSao e um recurso essencial que precisa ser dividido entre elas, abrindo assim a possibilidade de competitao

Hung out to dry: choice of priority ecoregions for conserving threatened neotropical anurans depends on life-history traits.

Background In the Neotropics, nearly 35% of amphibian species are threatened by habitat loss, habitat fragmentation, and habitat split; anuran species with different developmental modes respond to habitat disturbance in different ways. This entails broad-scale strategies for conserving biodiversity and advocates for the identification of high conservation-value regions that are significant in a global or continental context and that could underpin more detailed conservation assessments towards such areas. Methodology/Principal Findings We identified key ecoregion sets for anuran conservation using an algorithm that favors complementarity (beta-diversity) among ecoregions. Using the WWFs Wildfinder database, which encompasses 700 threatened anuran species in 119 Neotropical ecoregions, we separated species into those with aquatic larvae (AL) or terrestrial development (TD), as this life-history trait affects their response to habitat disturbance. The conservation target of 100% of species representation was attained with a set of 66 ecoregions. Among these, 30 were classified as priority both for species with AL and TD, 26 were priority exclusively for species with AL, and 10 for species with TD only. Priority ecoregions for both developmental modes are concentrated in the Andes and in Mesoamerica. Ecoregions important for conserving species with AL are widely distributed across the Neotropics. When anuran life histories were ignored, species with AL were always underrepresented in priority sets. Conclusions/Significance The inclusion of anuran developmental modes in prioritization analyses resulted in more comprehensive coverage of priority ecoregions–especially those essential for species that require an aquatic habitat for their reproduction–when compared to usual analyses that do not consider this life-history trait. This is the first appraisal of the most important regions for conservation of threatened Neotropical anurans. It is also a first endeavor including anuran life-history traits in priority area-selection for conservation, with a clear gain in comprehensiveness of the selection process.

Flower-heads, herbivores, and their parasitoids: food web structure along a fertility gradient

Abstract.u2002 1. The ways in which a soil fertility gradient affects three trophic level food webs defined by plants of the family Asteraceae, flower‐head herbivores, and their parasitoids was investigated. It was tested how the fertility gradient alters: (i) the abundance and richness of plants, herbivores, and their parasitoids, (ii) the herbivore–plant ratio, and (iii) the connectance of the plant–herbivore community matrix.

Diversidade e ocorrência de Asteraceae em cerrados de São Paulo

De abril a maio de 2000 a 2002 oito localidades com remanescentes de cerrados sensu stricto no estado de Sao Paulo foram amostradas para o levantamento das especies de asteraceas, uma das familias mais representativas da flora herbaceo-arbustiva nestas formacoes. Foram feitas 23 amostragens e cada area de estudo foi amostrada em media uma vez por ano durante o pico de floracao das plantas. Ao todo foram obtidas 399 amostras, nas quais foram reconhecidas 89 morfoespecies (74 foram identificadas como especies conhecidas). Quarenta por cento das especies foram registradas uma unica vez (unicatas), indicando um grande numero de especies raras. Apenas 10% das especies que ocorreram em mais de uma amostra foram obtidas de uma mesma area (sobreposicao espacial) ou de um mesmo ano de estudo (sobreposicao temporal). A riqueza de especies em cada area foi estimada por meio de transecoes e depois comparada a riqueza total observada em cada area de estudo, sendo esta na maioria das vezes mais alta que a estimada com base nas transecoes. A lista de especies obtida para os cerrados amostrados foi comparada a outras 24 listas publicadas para cerrados no Brasil. Embora a maioria das especies mais comuns tenha coincidido, oito especies (11% das especies identificadas) nao constam das listas publicadas. Concluimos que as areas de cerrado sensu stricto estudadas no estado de Sao Paulo encontram-se isoladas, com uma grande parte da flora herbaceo-arbustiva composta por varias especies raras e exclusivas. Diante deste quadro, sugerimos que a manutencao da biodiversidade de Asteraceae depende da conservacao de todo o conjunto de remanescentes de cerrado do estado de Sao Paulo.

Assemblages of endophagous insects on Asteraceae in São Paulo Cerrados

A survey of the endophagous insects fauna associated to Asteraceae capitula was carried out from 2000 to 2002 in eight cerrado sensu stricto sites located in the Brazilian state of Sdo Paulo. Sixty-four endophagous species of Diptera and Lepidoptera were recorded from 49 asteracean host plants. Approximately half of the species were obtained from a single locality, with a large proportion emerging from a single sample (unicates). Thirty percent of the species were singletons (i.e. only one individual was recorded). The large proportion of rare species suggests a high species turnover among localities. Lepidopteran species were recorded on more host species than dipterans, confirming their more polyphagous food habit, also observed in other Brazilian biomes and in Europe. We conclude that the studied cerrado localities, all within São Paulo State, are isolated with its invertebrate fauna composed of many rare and exclusive species. We suggest that the maintenance of Asteraceae biodiversity and their endophagous insects depend on the conservation of all cerrado remnants in the state.

Hypotheses for the richness of gall insects: a review considering the intraespecific, interespecific and community levels

In the literature there are several hypotheses that try to explain the patterns of global, regional and local richness of insects associated to plants. These hypotheses can be recognized in different ecological levels, explaining variations in the number of insects associated to individuals or populations of same host species, to different host species, and to different communities. However, the patterns of richness found in each of these levels are result of distinct ecological processes, thus each hypothesis has particularities related to its application depending on the processes considered and on the characteristics of the insect taxa. The objective of this review is to expose the hypotheses that have been used to explain the richness patterns of insects associated to plants, identifying the validity and the use status of each hypothesis in the intraespecific, interespecific, and community levels to gall insect – plant systems. In this review are explicitly enunciated 13 hypotheses considering the levels of ecological organization. This way of view represents a progress because it makes possible an objective analysis of what has been made in the field and a clear visualization of the gaps in the literature. Few hypotheses were enough tested in all levels, mostly in the intraespecific and interespecific levels. Thus it is evident that it is early to reach a general synthesis that explains the patterns of gall insects’ richness in all levels. This review expects, when enunciating the hypotheses in the different levels, to collaborate to the development of the field pointing directions to future studies. Key words: gall insect, richness patters, hypothesis.

Araucaria Forest conservation: mechanisms providing resistance to invasion by exotic timber trees

Since only 12.6% of the Brazilian Araucaria Forest remains and timber tree monocultures are expanding, biological invasion is a potential threat to the conservation of natural forest remnants. Here, we test (1) the susceptibility of Araucaria Forest to invasion by Pinus taeda and Eucalyptus saligna, (2) the efficiency of different mechanisms controlling the early establishment of these two exotic timber tree species, and (3) the potential of the native timber tree Araucaria angustifolia to establish successfully in ecologically-managed monocultures of Araucaria, Pinus and Eucalyptus. In Araucaria Forest, more than a thousand Pinus seeds landed annually in a hectare; however, experimentally exposed seeds were 100% removed in only 6xa0days. Furthermore, all experimentally transplanted seedlings of Pinus taeda and Eucalyptus saligna died in less than a year in Araucaria Forest, but not in the monocultures. Correlative evidence suggests that this mortality was associated to plant community richness, plant abundance, and soil fertility. Araucaria angustifolia, in contrast, showed an establishment success in ecologically-managed tree monocultures as high as that exhibited in its natural habitat. The current resistance of Araucaria Forest to invasion by exotic timber trees is good news for the conservation of Araucaria Forest remnants and for its keystone species. The understanding of the mechanisms providing such resistance against invasion points towards management tools for minimizing future threats.

Ecologically‐sustainable tree monocultures contribute to conservation of an Araucaria Forest endemic frog

Tree monocultures frequently have a negative impact on biodiversity; however, the adoption of ecologically‐sustainable management practices can produce a different outcome. In this study we evaluate how the replacement of Araucaria Forest by ecologically‐sustainable monocultures affects the abundance, age structure, sex ratio, and diet of the endemic frog Physalaemus lisei Braun andBraun(1977) (Leiuperidae). From October 2003 to April 2005, population samples were taken with pit‐fall traps in three 1 ha sites for each of the following habitats: Araucaria Forest, and old monocultures of Araucaria angustifolia, Pinus, and Eucalyptus. The number of individuals captured in Araucaria Forest was similar to that of the monocultures. Population recruitment was higher in the exotic monocultures. Captured individuals were female‐biased, the sex ratio being similar for all habitats. Physalaemus lisei was slightly more generalist on the monocultures. These results suggest that the forestry industry, by adopting ecologically‐sustainable management practices, can contribute to the conservation of threatened and endemic species.