Microhabitat use by Peucetia flava (Oxyopidae) on the glandular plant Rhyncanthera dichotoma (Melastomataceae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Natural history of Peucetia flava (Araneae, Oxyopidae): seasonal density fluctuation, phenology and sex ratio on the glandular plant Rhyncanthera dichotoma (Melastomataceae)

The seasonal density fluctuation, phenology and sex ratio of Peucetia flava (Oxyopidae) on Rhyncanthera dichotoma (Melastomataceae) were investigated during a year in a swamp in southeastern Brazil. Peucetia flava displayed an unusual non-seasonal life cycle and the population size varied little over the year. The density of Peucetia spiders increased with the increase in abundance of leaves and number of arthropods adhered to glandular trichomes on R. dichotoma leaves. Our findings suggest that seasonal density fluctuation of Peucetia may be influenced by foraging site availability (i.e. leaves) and prey supply (i.e. arthropods adhering to glandular trichomes). The unusual seasonal stability of P. flava may be related to the type of habitat in which this spider occurs (swamp), because of the constant input of allochthonous resources from the water source, i.e. aquatic insects that migrate to the terrestrial environment.

Association of two new Coryphasia species (Araneae, Salticidae) with tank-bromeliads in southeastern Brazil: Habitats and patterns of host plant use

Two allopatric species of Coryphasia (Araneae: Salticidae), both described for the first time in this study, have been found associated with Bromeliaceae in distinct phytophysiognomies (e.g., inselbergs, highland forests and restingas) from southeastern Brazil. In this study, we investigated whether these salticids were associated specifically with bromeliads, and whether they used bromeliads of different species and sizes in distinct geographic regions. The Coryphasia species were rarely found outside bromeliads, occupied larger bromeliad species among those available, and were generally more frequent on bromeliads in open areas, such as inselbergs on mountain tops. The two Coophasia species were observed submerging in phytotelmata, possibly as an anti-predatory behavior. The patterns of spatial and microspatial distribution and the submergence behavior of these species were similar to those of other bromeliad-dwelling salticids, which suggests a convergence among spiders that live on bromeliads.

The role of multiple partners in a digestive mutualism with a protocarnivorous plant

Background and aimsThe protocarnivorous plant Paepalanthus bromelioides (Eriocaulaceae) is similar to bromeliads in that this plant has a rosette-like structure that allows rainwater to accumulate in leaf axils (i.e. phytotelmata). Although the rosettes of P. bromelioides are commonly inhabited by predators (e.g. spiders), their roots are wrapped by a cylindrical termite mound that grows beneath the rosette. In this study it is predicted that these plants can derive nutrients from recycling processes carried out by termites and from predation events that take place inside the rosette. It is also predicted that bacteria living in phytotelmata can accelerate nutrient cycling derived from predators.MethodsThe predictions were tested by surveying plants and animals, and also by performing field experiments in rocky fields from Serra do Cipó, Brazil, using natural abundance and enriched isotopes of 15N. Laboratory bioassays were also conducted to test proteolytic activities of bacteria from P. bromelioides rosettes.Key ResultsAnalyses of 15N in natural nitrogen abundances showed that the isotopic signature of P. bromelioides is similar to that of carnivorous plants and higher than that of non-carnivorous plants in the study area. Linear mixing models showed that predatory activities on the rosettes (i.e. spider faeces and prey carcass) resulted in overall nitrogen contributions of 26·5 % (a top-down flux). Although nitrogen flux was not detected from termites to plants via decomposition of labelled cardboard, the data on 15N in natural nitrogen abundance indicated that 67 % of nitrogen from P. bromelioides is derived from termites (a bottom-up flux). Bacteria did not affect nutrient cycling or nitrogen uptake from prey carcasses and spider faeces.ConclusionsThe results suggest that P. bromelioides derive nitrogen from associated predators and termites, despite differences in nitrogen cycling velocities, which seem to have been higher in nitrogen derived from predators (leaves) than from termites (roots). This is the first study that demonstrates partitioning effects from multiple partners in a digestion-based mutualism. Despite most of the nitrogen being absorbed through their roots (via termites), P. bromelioides has all the attributes necessary to be considered as a carnivorous plant in the context of digestive mutualism. © 2012 The Author. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved.

Social wasp-flower visiting guild interactions in less structurally complex habitats are more susceptible to local extinction

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

In vitro allelopathic potential of Leonurus sibiricus L. leaves

The chemical interaction between plants is known as allelopathy and it is related to the release of substances into the environment. The present study aimed at the evaluation of the allelopathic activity of the leaves of Leonurus sibiricus against the germination and initial growth of Raphanus sativus, Lactuca sativa, and Lepidium sativum. Chemical analyses showed the presence in the leaves of four major flavonoids (quercetin-3-O-alpha-L-rhamnopyranosyl-(1 > 6)-beta-D-galactopyranoside; rutin; hyperin, and isoquercetrin) and of three minor flavonoidic compounds (genkwanin, 3'-hydroxy genkwanin, and quercetin). Extracts, their chromatographic fractions and pure isolated flavonoids showed different biological activities. A methanol extract of leaves of Leonurus sibiricus caused significant reduction only in the germination of Lactuca sativa, with no effects on the germinative processes of Raphanus sativus and Lepidium sativum. Some chromatographic fractions, containing the flavonoids, showed inhibitory activity on the initial stages of root growth of all tested seeds. The isolated flavonoids, at the higher concentration tested (10(-4) M) seemed to be responsible for the inhibition of the germination, as well as the radical elongation. Among pure compounds, 3'-OH-genkwanin and quercetin showed the stronger antigerminative activity at the concentration of 10(-4) M, whereas the radical elongation was reduced by rutin, isoquercetrin and 3'-OH-genkwanin. All compounds, tested at concentrations ranging between 10(-5) and 10(-7) M, showed stimulatory activities.

In Vitro Phytotoxicity and Antioxidant Activity of Selected Flavonoids

The knowledge of flavonoids involved in plant-plant interactions and their mechanisms of action are poor and, moreover, the structural characteristics required for these biological activities are scarcely known. The objective of this work was to study the possible in vitro phytotoxic effects of 27 flavonoids on the germination and early radical growth of Raphanus sativus L. and Lepidium sativum L., with the aim to evaluate the possible structure/activity relationship. Moreover, the antioxidant activity of the same compounds was also evaluated. Generally, in response to various tested flavonoids, germination was only slightly affected, whereas significant differences were observed in the activity of the various tested flavonoids against radical elongation. DPPH test confirms the antioxidant activity of luteolin, quercetin, catechol, morin, and catechin. The biological activity recorded is discussed in relation to the structure of compounds and their capability to interact with cell structures and physiology. No correlation was found between phytotoxic and antioxidant activities.

Habitat selection and potential antiherbivore effects of Peucetia flava (Oxyopidae) on Solanum thomasiifolium (Solanaceae)

Several spider species use plants as shelter and foraging sites, but the relationships among these organisms are still poorly known. Lynx spiders of the genus Peucetia do not build webs, and many species live strictly in plants bearing glandular trichomes. Peucetia flava Keyserling 1877 inhabits Solanum thomasifolium in southeastern Brazil and usually preys on herbivores and other small insects adhered to the glandular trichomes of its host plant. To evaluate the potential anti-herbivore protection. of this spider species for S. thomasifolium, we glued termites used as herbivore models oil trichomes of S. thomasifolium and on neighboring plants lacking glandular trichomes. leaf miner damage and spider density were recorded for S. thomasifolium plants in July 1997. There was a positive relationship between plant size and spider density. The removal or termites in S. thomasifolium by P. flava was higher than ill plants without glandular trichomes. The leaf miner damage was negatively related to spider density. Our results Suggest that P. flava may be all important plant bodyguard in the defense of S. thomasifolium from its natural herbivores.

Mites and leaf domatia: no evidence of mutualism in Coffea arabica plants

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

In vitro allelopathic effects of extracts and amenthoflavone from Byrsonima crassa (Malpighiaceae)

Extracts and pure amenthoflavone isolated from Byrsonima crassa (Malpighiaceae), a shrub growing in the semi-arid region of Brazil Cerrado, were evaluated in vitro, at different doses, for their effects on tomato seed germination and subsequent growth of seedlings. A hydromethanolic extract showed general stimulatory effects. The EtOAc extract stimulated root elongation and root weight of tomato; shoot elongation was inhibited, while shoot weight was not altered. The pure amenthoflavone isolated from the plant, stimulated shoot elongation at concentrations ranging between 10(-4) M and 10(-6) M.

Geographic range, habitats, and host plants of bromeliad-living jumping spiders (Salticidae)

Although spiders are a very diverse group on vegetation, their associations with plants are poorly known. Some salticid species specifically use Bromeliaceae as host plants in some regions of South America. In this study, I report the geographic range of these spider-bromeliad associations, and whether the spiders inhabit particular bromeliad species and vegetation types, as well as open areas or interior of forests. Nine salticid species were found to be associated with up to 23 bromeliad species in cerrados (savanna-like vegetation), semideciduous and seasonal forests, coastal sand dune vegetation, restingas, inselbergs, highland forests, chacos, and rain forests at 47 localities in Brazil, Paraguay, Bolivia, and Argentina. Some species were typically specialists, inhabiting almost exclusively one bromeliad species over a large geographic range (e.g., Psecas chapoda on Bromelia balansae), whereas others were generalists, occurring on up to 7-8 bromeliad species (e.g., Psecas sp., Eustiromastix nativo, and Coryphasia sp. 1). The regional availability of bromeliad species among habitats may explain this pattern of host plant use. More jumping spiders were found on bromeliads in open areas than on bromeliads in the interior of forests. These results show that several jumping spider species may be strictly associated with the Bromeliaceae in the Neotropics. This is one of the few studies to show host-specific associations for spiders on a particular plant type over a wide geographic range.

Oviposition pattern and within-season spatial and temporal variation of pre-dispersal seed predation in a population of Mimosa bimucronata trees

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Succession and management of tropical dry forests in the Americas: Review and new perspectives

Understanding tropical forest succession is critical for the development of tropical forest conservation strategies worldwide, given that tropical secondary forests can be considered the forests of the future. Tropical dry forests (TDF) are among the most threatened tropical ecosystems, there are more secondary forests and forest restoration efforts that require a better understanding of successional processes. The main goal of this synthesis for this special issue on the ecology and management of tropical dry forests in the Americas is to present a summarized review of the current knowledge of the ecology and management implications associated to TDF succession. We explore specific issues associated to tropical dry forest succession with emphasis on the use of chronosequences, plant diversity and composition, plant phenology and remote sensing, pollination, and animal-plant interactions; all under the integrating umbrella of ecosystem succession. We also emphasize the need to conduct socio-ecological research to understand changes in land-use history and its effects on succession and forest regeneration of TDF. We close this paper with some thoughts and ideas associated with the strong need for an integrating dimension not considered until today: the role of cyberinfrastructure and eco-informatics as a tool to support sound conservation, management and understanding of TDF in the Americas. (C) 2009 Elsevier B.V. All rights reserved.

Ant exclusion and reproduction of Croton sarcopetalus (Euphorbiaceae)

A total of 20 insect species were observed on the extrafloral nectaries (EFNs) of Croton sarcopetalus. The most frequent ant species were Zacryptocerus sp., Crematogaster brevispinosa, C. scelerata, and Linepithema humile. Ants continuously patrolled the plants taking extrafloral nectar. Experimental data showed that there were no significant differences in either the degree of herbivory or in the reproductive output between control stems (with ants) and treated ones (without ants). We found no significant evidence of protection by ants mediated by EFNs in C. sarcopetalus. It is possible that the plant has other mechanisms than ant protection to prevent herbivore damage (e.g., hairs, latex, chemical defense). As this species occupies the southernmost distribution for the genus, the presence of EFNs in this species may be the remnant of a mutualistic interaction with the ants in tropical regions, where the abundance and diversity of ants and herbivores are comparatively higher. To draw accurate patterns in the genus Croton, further investigations in other species from tropical regions of South America are needed.

Contrasting engineering effects of leaf-rolling caterpillars on a tropical mite community

Ecosystem engineers are organisms that change the physical structure of environments and provide habitats for other organisms. Lepidopteran caterpillars may act as ecosystem engineers by rolling leaves as shelters to complete metamorphosis. After being abandoned, these structures may provide shelter for other organisms. In this study, the influence of leaf-rolling caterpillars on tropical mite communities was reported. Expanded leaves and leaves rolled by larvae and also developed field experiments using leaves rolled manually with different shapes and sizes (i.e. different architectures) in different seasons were surveyed (dry and rainy). While the abundance and diversity of predatory mites were higher in rolled leaves, the abundance of phytophages decreased in these leaves. Species composition differed between rolled and expanded leaves. The structure of shelters affected the distribution of predatory mites, with higher abundances found on funnel-shaped leaves. Predatory mites only benefited from the rolled leaves in the dry season. This is the first study showing (i) the contrasting effects of ecosystem engineers on microarthropod communities, favouring some feeding guilds and inhibiting others; (ii) that the shape of rolled leaves has variable effects on mite communities; and (iii) that facilitation was temporally dependent, i.e. occurred only in the dry season. © 2013 The Royal Entomological Society.