Luis Schiesari

Vertebrate predation of Brazil-nuts (Bertholletia excelsa, Lecythidaceae), an agouti-dispersed Amazonian seed crop: a test of the escape hypothesis.

The effects of escape distance to parental trees anid tree clusteis oIn the removal of Biazil-niut seeds (Bertholletia excelsa, Lecythidaceae) by vertebrate seed predators were examined in ani entirely undisturbed stanid of Brazil-nut trees of easter-n Amazoniia. Populationi denisity estimates, based oIn line-trainsect censuses, are also presenited for Bertholletia trees and agoutis (Dasvprocta leporiina), the most important scatterhoarder and seed predator of Biazil-niuts at this site. Seed removal experimenits were conducted withini an-d outside a natural Betltholletia tree cluster (castan/hal) during both the wet and dry seasons. While there were no withiin-cluster effects of escape distance from parent trees on seed removal rates, overall seed removal withini the cluster was signiificantly greater than that well outside the cluster. Moreover, removal rates in the wet season were coisist- ently higlher than those in the dry seasoni both within and outside the tree cluster. Results suggest that the probability of early seed survival for Betitholletia, in ielatioin to distance to seed sources, operates on differeint spatial scales, aind that seed predators allocate greater foraginlg effort to scattered seeds durinig the fruitfall (wet) season, when buried seed stocks are being cached by agoutis.

Anfíbios do Estado de São Paulo, Brasil: conhecimento atual e perspectivas

The last list of species of the state of Sao Paulo State was updated and totaled 236 species of amphibians, 230 of which are anurans and six are caecilians. Bokermannohyla gouveai and Sphaenorhynchus surdus were removed from this list, because they did not occur in the State of Sao Paulo. The number of anuran species recorded comprise 27% of the species richness of the country and an increase by 31% in the number of species recorded for the state since 1998. Thus, despite the State of Sao Paulo be the Brazilian region where the anurans have been most studied, these data show that the number of known species tends to increase in the next years. We have identified two major geographical gaps of inventory: the southwest of the state, especially in the Paranapanema river basin and the northeast region, mainly at the border between the States of Minas Gerais and Sao Paulo. Although both have been sampled recently, information is still lacking. The current state of knowledge and perspectives in the areas such as taxonomy, systematics, ecology and conservation are evaluated.

Pesticides meet megadiversity in the expansion of biofuel crops

Global interest in biofuels is driving a continuous expansion of agroindustrial production in tropical countries, bringing a substantial share of the worlds biodiversity into contact with hundreds of potentially hazardous pesticides. We reviewed the hazards imposed by all 784 pesticides currently registered for use on biofuel crops in Brazil. We detected compounds that have been suspended by international conventions, as well as over 80 compounds included in lists of priority concern for exhibiting environmental persistence and/or having the potential to elicit neurotoxic, reprotoxic, carcinogenic, or endocrine-disrupting effects in humans and wildlife. These chemicals will be used at increased rates, or for the first time, across large expanses of agroin-dustrially converted pastures and native (ie pristine) habitat in the cerrado (tropical savanna) and Amazonian rainforest biomes. If human and environmental health are to be balanced with productivity to achieve a sustainable agriculture, bolder initiatives on pesticide restriction and control must be implemented in tropical countries.

Pesticide use and biodiversity conservation in the Amazonian agricultural frontier

Agricultural frontiers are dynamic environments characterized by the conversion of native habitats to agriculture. Because they are currently concentrated in diverse tropical habitats, agricultural frontiers are areas where the largest number of species is exposed to hazardous land management practices, including pesticide use. Focusing on the Amazonian frontier, we show that producers have varying access to resources, knowledge, control and reward mechanisms to improve land management practices. With poor education and no technical support, pesticide use by smallholders sharply deviated from agronomical recommendations, tending to overutilization of hazardous compounds. By contrast, with higher levels of technical expertise and resources, and aiming at more restrictive markets, large-scale producers adhered more closely to technical recommendations and even voluntarily replaced more hazardous compounds. However, the ecological footprint increased significantly over time because of increased dosage or because formulations that are less toxic to humans may be more toxic to other biodiversity. Frontier regions appear to be unique in terms of the conflicts between production and conservation, and the necessary pesticide risk management and risk reduction can only be achieved through responsibility-sharing by diverse stakeholders, including governmental and intergovernmental organizations, NGOs, financial institutions, pesticide and agricultural industries, producers, academia and consumers.

Macrophyte rafts as dispersal vectors for fishes and amphibians in the Lower Solimoes River, Central Amazon

*Departamento de Zoologia, Instituto de Biocieˆncias, Universidade de Sa˜o Paulo, CP 20520, 01452-990, Sa˜o Paulo-SP, Brazil†Coordenac¸a˜o de Pesquisas em Biologia Aqua´tica, Caixa Postal 478, Instituto Nacional de Pesquisas da Amazoˆnia, 69083–970, Manaus-AM, Brazil‡Nu´cleo de Altos Estudos Amazoˆnicos-NAEA, Universidade Federal do Para´ 67070-100, Bele´m-PA, Brazil§Departamento de Biologia, Universidade do Amazonas, 69970-000, Manaus-AM, Brazil¶UNESP-Rio Claro, PG Zoologia, Avenida 24-A, 1515, C.P. 199, 13506-900, Rio Claro-SP, Brazil#Laborato´rio de Ecologia de Mami´feros, Centro de Cieˆncias da Sau´de, UNISINOS, CP 275, 93022-000, Sa˜o Leopoldo-RS, Brazil(

Mechanisms of nonlethal predator effect on cohort size variation : Ecological and evolutionary implications

Understanding the factors responsible for generating size variation in cohorts of organisms is important for predicting their population and evolutionary dynamics. We group these factors into two broad classes: those due to scaling relationships between growth and size (size-dependent factors), and those due to individual trait differences other than size (size-independent factors; e.g., morphology, behavior, etc.). We develop a framework predicting that the nonlethal presence of predators can have a strong effect on size variation, the magnitude and sign of which depend on the relative influence of both factors. We present experimental results showing that size-independent factors can strongly contribute to size variation in anuran larvae, and that the presence of a larval dragonfly predator reduced expression of these size-independent factors. Further, a review of a number of experiments shows that the effect of this predator on relative size variation of a cohort ranged from negative at low growth rates to positive at high growth rates. At high growth rates, effects of size-dependent factors predominate, and predator presence causes an increase in the scaling of growth rate with size (larger individuals respond less strongly to predator presence than small individuals). Thus predator presence led to an increase in size variation. In contrast, at low growth rates, size-independent factors were relatively more important, and predator presence reduced expression of these size-independent factors. Consequently, predator presence led to a decrease in size variation. Our results therefore indicate a further mechanism whereby nonlethal predator effects can be manifest on prey species performance. These results have strong implications for both ecological and evolutionary processes. Theoretical studies indicate that changes in cohort size variation can have profound effects on population dynamics and stability, and therefore the mere presence of a predator could have important ecological consequences. Further, changes in cohort size variation can have important evolutionary implications through changes in trait heritability.

Scaling-up anti-predator phenotypic responses of prey: impacts over multiple generations in a complex aquatic community.

Non-consumptive effects (NCEs) of predators owing to induced changes in prey traits are predicted to influence the structure of ecological communities. However, evidence of the importance of NCEs is limited primarily to simple systems (e.g. two to four species) over relatively short periods (e.g. less than one generation). We examined the NCEs of a fish predator, arising from phenotypic plasticity in zooplankton prey traits, over multiple generations of a diverse zooplankton community. The presence of fish, caged to remove consumptive effects, strongly influenced zooplankton community structure, through both direct and indirect NCE pathways, altering the abundance of many taxa by magnitudes as large as 3 to 10-fold. Presence of fish affected different species of cladocerans and copepods both positively and negatively. A particularly striking result was the reversal of dominance in copepod taxa: presence of fish reduced the ratio of calanoids to cyclopoids from 6.3 to 0.43. Further, the NCE of fish had a strong negative trophic cascade to zooplankton resources (phytoplankton). To our knowledge, this is the first experiment to show that NCEs can influence the abundance of multiple prey species over time spans of multiple prey generations. Our findings demonstrate that adaptive phenotypic plasticity of individuals can scale-up to affect the structure of ecological communities.

The growth-mortality tradeoff: evidence from anuran larvae and consequences for species distributions

A tradeoff affecting the ability to grow under high versus low resource levels has been commonly hypothesized to influence species distributions across resource gradients in a wide variety of taxa. This influence is dependent on individual growth being proportional to traits that affect demographic processes such as mortality. However, data on how individual growth scales with demographic performance are rare. We conducted a mesocosm experiment, and re-analyzed data from a similarly designed field experiment, to examine the relationship between growth and mortality in two tadpole species that segregate across a resource gradient. Overall, environmental conditions leading to faster growth also lead to lower mortality rates. However, species differed in this relationship. Leopard frogs achieved faster growth than wood frogs, but their absolute mortality was greater and increased steeply as growth decreased. Conversely, absolute mortality of wood frogs was lower and less strongly dependent on growth. These interspecific differences suggest a second tradeoff, that between maximizing growth rates or minimizing mortality, with potentially important demographic consequences. Leopard frogs grow faster than wood frogs in productive ponds, but are excluded from unproductive ponds dominated by wood frogs due to accelerating mortality rates with declining realized growth. A review of the literature suggests that in diverse taxa, including plants, microcrustaceans and drosophilids, patterns in mortality are consistent with this tradeoff indicating that the mechanism we demonstrate could be a link between individual performance and demographic rates influencing species distributions in other systems.

Treeholes as calling, breeding, and developmental sites for the Amazonian canopy frog, Phrynohyas resinifictrix (Hylidae)

Abstract In this paper, we present information on the natural history, reproductive and developmental strategies of the canopy treefrog Phrynohyas resinifictrix. Phrynohyas resinifictrix is a widespread Amazonian species breeding exclusively in water-filled treeholes in terra-firme rain forests. Females laid relatively large, floating egg masses in the treeholes. Gut content analyses indicated that tadpoles are generalists and predominantly macrophageous, basing their diet on detritus and conspecific fertilized eggs of younger cohorts. Tadpole guts were found to contain up to 62 intact eggs. This cannibalistic interaction is presumably of major importance for the completion of the larval stage and may result in depletion of entire egg complements. Strong site fidelity, interference competition for treeholes by territorial males, continuous use of treeholes year after year, repeated oviposition in treeholes, and temporal constancy in density of calling males are consistent with the hypotheses that adequate treeholes are a limiting resource for P. resinifictrix populations, or that location of unoccupied treeholes in the rain-forest canopy involves substantial risk or energetic costs.

Diet of Juvenile Aquatic Caecilians, Typhlonectes compressicauda

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