Carlos Frankl Sperber

Atropelamentos de vertebrados na Floresta Nacional de Carajás, Pará, Brasil

Several researchers have evaluated impacts of highways. These can involve landscape aspects, soil degradation, air pollution, and impacts upon wildlife, such as roadkills. At the Raimundo Mascarenhas highway, that crosses the Carajas National Forest (ca. 400.000 ha), there is intense traffic of automotive vehicles. The aim of this work was to test if there were differences among higway sections on three spatial scales; if there was alteration along the years; if some taxa suffered more frequently roadkills; and if roadkill frequency increased with monthly precipitation. We analysed roadkill frequency of vertebrates from April/2003 to Octobre/2006 along the first 25 km of the highway. We registered 155 roadkills. The number of roadkills diminished along the years (P=0,01), and with distance from the beginning of the highway (P=0,0002). Snakes (Ophidia) and opossum Didelphis marsupialis presented higher roadkill numbers (7,5/year), followed by birds (Aves), crab-eating fox Cerdocyon thous, coati Nasua nasua, rodents (Rodentia), and non identified (4,9/year); opossum Marmosops sp., brazilian rabbit Sylvilagus brasiliensis, black howler monkey Alouatta sp., tayra Eira barbara, tortoise Geochelone sp., lizards (Lacertilia) e capuchin monkey Cebus apella (1/year). There was no significant relation between monthly roadkill numbers and monthly precipitation.

Ethanol fuel improves arthropod capture in pitfall traps and preserves DNA

Abstract We tested the value of ethanol fuel as a killing solution in terms of sampling efficiency (species richness and accumulated abundance) and DNA preservation of Ensifera ground-dwelling specimens. Sampling efficiency was evaluated comparing abundance and species richness of pitfall sampling using 100% ethanol fuel, with two alternative killing solutions. We evaluated the DNA preservation efficiency of the killing solutions and of alternative storage solutions. Ethanol fuel was the most efficient killing solution, and allowed successful DNA preservation. This solution is cheaper than other preserving liquids, and is easily acquired near field study sites since it is available at every fuel station in Brazil and at an increasing number of fuel stations in the U.S. We recommend the use of ethanol fuel as a killing and storage solution, because it is a cheap and efficient alternative for large-scale arthropod sampling, both logistically and for DNA preservation. For open habitat sampling with high day temperatures, we recommend doubling the solution volume to cope with high evaporation, increasing its efficacy over two days.

Morphometric differences in the grasshopper Cornops aquaticum (Bruner, 1906) from South America and South Africa

Abstract The semi-aquatic grasshopper Cornops aquaticum is native to South America and inhabits lowlands from southern Mexico to Central Argentina and Uruguay. It is host-specific to aquatic plants in the genera Eichhornia and Pontederia. A quarantine population has existed in South Africa for 10 y, and it is planned to release it there as a biological control agent of water hyacinth, E. crassipes. Various studies of C. aquaticum are coordinated under HICWA (www.mpil-ploen.mpg.de). This paper compares the morphometry of the release population and 11 native populations in South America. We tested four hypotheses: 1) South African and South American populations of C. aquaticum differ in morphology; 2) the South African laboratory population is more similar to other isolated populations in South America than to nonisolated populations; 3) morphology differs across sites; 4) morphology differs with host plant. South African populations differed from continental nonisolated populations, but not from continental isolated ones. Isolated populations presented smaller individuals than nonisolated, but there was also a change in male morphology: while in nonisolated populations male wing length was similar to their body length, in isolated populations, male wings were smaller than body length. Females were larger when on Eicchornia azurea than on E. crassipes, while males presented larger wings than their body on E. azurea, and similar lengths on E. crassipes. These morphological changes may have resulted from phenotypic plasticity, selection for small size, or because of a loss of genetic diversity in quantitative traits.

Density-dependent morphological plasticity in Salvinia auriculata aublet

This study examined the effect of crowding on the size of the floating and submerged leaves of Salvinia auriculata. In addition, we examined investment in reproductive structures (sporocarps) in response to the size of ramets. Ramets of S. auriculata growing on the surface of lagoons in the Southern Pantanal were sampled from populations of different densities. Ramets under densely crowded conditions were significantly larger than ramets under uncrowded conditions. There was a tendency for the number of sporocarps to increase with the size of submerged leaves, but not with length or specific area of floating leaves. These results indicate that S. auriculata exhibit density-dependent morphological plasticity, and may be a reflection of an evolved strategy that increases competitive ability of the ramets. It further suggests that the increase in production of sporocarps may not be a simple response to the size of ramets.

Host behavioural manipulation of two orb-weaver spiders by parasitoid wasps

Parasitic infection or tissue consumption by parasitoids typically leads to several phenotypic alterations in hosts, including distinct changes in behavioural, morphological, or life history traits. Some of these changes may not result solely from host responses, but actively induced changes by parasites/parasitoids to manipulate the host to acquire some benefit (e.g. parasite/parasitoid survivorship or dispersal ability). Field experiments investigating the effects of host behavioural alterations on parasite or parasitoid survivorship and the mechanisms involved in these changes are important for confirmation of behavioural manipulation. In the present study, we examined web design modification in the host spider species Cyclosa fililineata and Cyclosa morretes, which are attacked by the polysphinctine ectoparasitoid wasps Polysphincta sp. nr. purcelli and Polysphincta janzeni, respectively. We tested whether changes in orb spider web design (1) result from nutritional restrictions imposed by parasitoids and (2) increase the chances of adult wasp emergence from the cocoon. Furthermore, we describe changes in web design consistent with parasitoid larval development. Results, for both spider species, showed that web design modifications occurred only during the night preceding host spider death, and that modifications involved a reduction in the number of spirals and radii of orb webs. Food restriction did not generate web design modification, suggesting that observed changes in host behaviour resulted from direct actions of parasitoid larvae rather than as a by-product of nutritional deficiencies. Rain events were the major factor causing web rupture and subsequent parasitoid mortality. Modifications in web design reduced the frequency of web ruptures, increasing parasitoid adult emergence, and thus survivorship probability, during the pupal stage. These results confirm that web modifications by spiders are adaptive to parasitoid wasps.

Litter disturbance and trap spatial positioning affects the number of captured individuals and genera of crickets (Orthoptera: Grylloidea)

Abstract There are several factors that may affect sampling with pitfall traps. Here we test the hypothesis that the mere walking of the researcher proximate to the traps could cause an increment in the capture of crickets. This would occur if the walking provoked vibration in the litter, to which crickets showed a jumping response, thus falling into the pitfall traps. We mounted 126 traps in 14 groups of nine. The traps within a group were positioned in three parallel rows of three traps each, one meter apart from each other. Each group of nine traps was separated from the other groups by at least 5 m. Each group of nine traps was submitted to one of seven levels of disturbance frequency. Exposure time was 7 d for all traps. Treatments (disturbance frequencies) were allocated randomly among trap groups. For the data analyses we adjusted mixed-effects polynomial models. We captured 723 cricket individuals, distributed in 10 genera, most in the nymphal stage. As expected, the number of captured individuals, as well as the number of genera, increased with disturbance frequency. However this response was not linear: at higher disturbance frequencies there was a decrease in captures. There was also an effect of trap positioning within each group: central traps were more affected by disturbance than peripheral ones, while peripheral traps captured more individuals and genera in the absence of disturbance. Therefore we recommend areas near pitfall traps not be visited during the trapping period. Alternatively, to enhance sampling efficiency, the researcher may do programmed visiting to the trapping area, but this must be rigorously designed to provoke exactly the same disturbance for all traps. Enhancing the distance among traps will augment efficiency in capturing individuals and capture larger cricket diversity. Further studies of the interaction between methodology and cricket behavior will refine our ability to design and interpret pitfall studies.

Effects of Forest Regeneration on Crickets: Evaluating Environmental Drivers in a 300-Year Chronosequence

We evaluated the relation of cricket species richness and composition with forest regeneration time, evaluating canopy and litter depth as environmental drivers. Effects of forest patch area, nearest distance to the 300-year patch, cricket abundance, sampling sufficiency, and nestedness were also evaluated. We collected 1174 individuals (five families, 19 species). Species richness increased asymptotically with regeneration time and linearly with canopy cover and litter depth. Canopy cover increased linearly, while litter depth increased asymptotically. Richness was not affected by patch area and nearest distance to the 300-year patch. Richness increased with cricket abundance, and this explanation could not be distinguished from regeneration time, evidencing collinearity of these two explanatory variables. Rarefaction curve slopes increased with regeneration time. Species composition differed among patches, with no nested pattern. We suggest that regeneration and consequent increases in canopy and litter promote recovery of cricket biodiversity, abundance, and changes in species composition. We conclude that the recovery of cricket diversity involves an increase along the spatial scale of complementarity, together with a change in species composition.

Tri-trophic level interactions affect host plant development and abundance of insect herbivores

Understanding the interactions among plants, hemipterans, and ants has provided numerous insights into a range of ecological and evolutionary processes. In these systems, however, studies concerning the isolated direct and indirect effects of aphid colonies on host plant and other herbivores remain rare at best. The aphid Uroleucon erigeronensis forms dense colonies on the apical shoots of the host plant Baccharis dracunculilfolia (Asteraceae). The honeydew produced by these aphids attracts several species of ants that might interfere with other herbivores. Four hypotheses were tested in this system: (1) ants tending aphids reduce the abundance of other herbivores; (2) the effects of ants and aphids upon herbivores differ between chewing and fluid-sucking herbivores; (3) aphids alone reduce the abundance of other herbivores; and (4), the aphid presence negatively affects B. dracunculifolia shoot growth. The hypotheses were evaluated with ant and aphid exclusion experiments, on isolated plant shoots, along six consecutive months. We adjusted linear mixed-effects models for longitudinal data (repeated measures), with nested spatial random effect. The results showed that: (1) herbivore abundance was lower on shoots with aphids than on shoots without aphids, and even lower on shoots with aphids and ants; (2) both chewing and fluid-sucking insects responded similarly to the treatment, and (3) aphid presence affected negatively B. dracunculifolia shoot growth. Thus, since aphids alone changed plant growth and the abundance of insect herbivores, we suggest that the ant–aphid association is important to the organization of the system B. dracunculifolia-herbivorous insects.

Aprimoramento da amostragem de grilos de serapilheira (Orthoptera: Gryllidae) por armadilha

Amostram-se grilos de serapilheira com armadilhas enterradas (pitfall). No entanto, algumas especies sao sub-amostradas, por que alguns individuos conseguem fugir da armadilha. Neste trabalho sugerimos a substituicao da solucao aquosa de detergente, por uma solucao de formol-glicerina-alcool, para aumentar a eficiencia da amostragem. Testamos se: (i) formol reduz a fuga de grilos; (ii) formol e repelente para os grilos. Foram instaladas 80 armadilhas, formando pares formol-detergente e detergente-detergente, com 20 cm entre armadilhas dentro do par, e 3 m entre pares. Foram coletados 105 individuos, sendo 29 adultos, de nove especies, em tres grupos taxonomicos: Phalangopsinae, Trigonidiinae e Brachytrupinae. Tanto o numero de adultos quanto de ninfas capturados nas armadilhas com detergente nao foi afetado pela proximidade de armadilha com formol. Nos pares formol-detergente, o numero de adultos em formol foi maior que em detergente, enquanto o numero de ninfas nao foi diferente. Assim, formol nao foi repelente nem para adultos nem para ninfas de grilos. As armadilhas com formol foram mais eficientes, por reterem mais adultos do que as com detergente, devido ao efeito de knock-down. As ninfas nao foram afetadas porque sua fuga do detergente ja e reduzida, devido a seu tamanho reduzido e menor esclerotizacao. Tamanho menor implica saltos menores, insuficientes para o escape. Esclerotizacao menor implica maior permeabilidade, de forma que uma vez que a ninfa cai na armadilha, ela nao consegue mais fugir.

Does the age of the host plant modulate migratory activity of Plutella xylostella

Ephemeral plants and most tropical crops are available to herbivore insects as irregular and unpredictable patches of resources. Insects that exploit patched habitats usually have well‐developed migratory ability, and migration is a fundamental process in the cycle of colonization and extinction of the local populations. We ask here whether Plutella xylostella (Lepidoptera: Yponomeutidae) uses the aging process of the host plant to modulate its migratory activity. The insect was reared in the laboratory on the leaves from the middle estratum (fourth expanded leaves) of cabbage (Brassica oleraceae var. capitata) of various ages, and on leaves from three strata of the mature plant. Females that spent their larval phase in young and tender plants lived for a shorter period of time and laid eggs immediately after metamorphosis. In contrast, mature plants, particularly the new leaves from the superior stratum, favored the development of adult phenotypic traits that occur in migratory forms, such as reduced body size, increased longevity and delayed reproductive activity. We suggest that the lesser nutritional quality and the short temporal persistence of mature plants are selective forces favoring individuals that are better prepared to abandon their habitat soon after emergence. Plutella xylostella may use the predictable ontogenetic changes of the ephemeral host plant to modulate its physiological and behavioral migratory ability.