Kleber Del-Claro

Conditional outcomes in a neotropical treehopper-ant association: temporal and species-specific variation in ant protection and homopteran fecundity

Abstract We studied the association between the honeydew-producing membracid Guayaquila xiphias and its tending ants in the cerrado savanna of Brazil, during 1992 and 1993. Results showed that ants attack potential enemies of G. xiphias, and that increased ant density near the treehoppers affects the spatial distribution of parasitoid wasps on the host plant, keeping them away from brood-guarding G. xiphias females. Controlled ant-exclusion experiments revealed that ant presence (seven species) reduces the abundance of G. xiphias’ natural enemies (salticid spiders, syrphid flies, and parasitoid wasps) on the host plant. The data further showed that ant-tending not only increased homopteran survival, but also conferred a direct reproductive benefit to G. xiphias females, which may abandon the first brood to ants and lay an additional clutch next to the original brood. Two years of experimental manipulations, however, showed that the degree of protection conferred by tending ants varies yearly, and that at initially high abundance of natural enemies the ant species differ in their effects on treehopper survival. Ant effects on treehopper fecundity also varied with time, and with shifts in the abundance of natural enemies. This is the first study to simultaneously demonstrate conditionality in ant-derived benefits related to both protection and fecundity in an ant-tended Membracidae, and the first to show the combined action of these effects in the same system.

Ant-Homoptera interaction: do alternative sugar sources distract tending ants?

aggregations probably explains why ant tending levels remained unchanged in the presence of an alternate sugar source. The current experimental study and available field evidence from cerrado vegetation do not support the prediction that ants would neglect honeydew-producing homopterans in the presence of extrafloral nectaries.

The outcomes of an ant-treehopper association on Solanum lycocarpum St. Hill: increased membracid fecundity and reduced damage by chewing herbivores

Interacoes entre formigas e hemipteros (Auchenorryncha e Sternorryncha) sao importantes ferramentas para o estudo do impacto de relacoes multitroficas sobre a diversidade de artropodes na vegetacao. No presente estudo, atraves de manipulacao experimental no campo, investigou-se no cerrado o impacto de uma dessas relacoes multitroficas para quatro membros da interacao: formigas, o hemiptero (Enchenopa brasiliensis Strumpel, a planta hospedeira (Solanum lycocarpum St. Hill) e herbivoros. A variacao nos efeitos da relacao ao longo do tempo tambem foi avaliada. Os resultados permitiram verificar que formigas se beneficiam de uma fonte alimentar rica e previsivel no tempo e espaco, enquanto que os membracideos atendidos por formigas sobreviveram melhor. Os resultados mostram tambem que o beneficio da relacao pode se estender sobre a fecundidade dos membracideos. A presenca da associacao formiga-hemiptero teve um impacto significativo sobre a reducao da herbivoria por mastigadores na planta hospedeira.

Nectar- and pollen-gathering Cephalotes ants provide no protection against herbivory: a new manipulative experiment to test ant protective capabilities

The question if ant behaviour and biological limitations should be considered before generalisations about the ant’s defensive capabilities in ant–plant relationships was explored through a new experimental manipulation. In the Brazilian tropical savanna, we tested the protective action of Cephalotes pusillus Klug on the extrafloral nectar-bearing plant Ouratea spectabilis Engl. (Ochnaceae). Three treatments were performed: control (free ant access), Cephalotes-treatment (access permitted only to C. pusillus), and ant free treatment (no ants). No difference was found in the levels of leaf herbivory among experimental stems. Visitation by different ant species to control stems translated into significantly greater fruit and seed production by this stem category than by ant-free and Cephalotes-treated stems. Thus, results showed that an investigation of system’s natural history, ant’s morphological traits, defensive capabilities and behaviour are needed before a protective role is inferred to each associated ant species.

Influence of extrafloral nectary phenology on ant–plant mutualistic networks in a neotropical savanna

Temporal variation has been one remarkable feature of ecological interactions. In ant–plant mutualism, this variation is widely known, although little is understood about the mechanisms that shape these variations. This study tested whether or not the phenology of extrafloral nectaries (EFNs) influences the temporal variation of two properties of an ant–plant interaction network. The network under investigation exhibited a nested pattern and low specialisation over most months. Monthly nestedness and specialisation in the network were negatively correlated, both being influenced by temporal variations in extrafloral nectar production of the plant community. The months of highest activity in the nectaries (August–November) were those when the level of generalisation in the network was at its highest. Although there were temporal variations in the properties of the network, the generalist core of the species remained the same over time. The stable core enhances the coevolutionary importance of ant–plant interactions for the community. Thus, it can be concluded that the phenology of EFNs is one effective mechanism shaping the temporal variation in ant–plant interaction.

Ant-plant interaction in a tropical savanna: may the network structure vary over time and influence on the outcomes of associations?

Plant-animal interactions occur in a community context of dynamic and complex ecological interactive networks. The understanding of who interacts with whom is a basic information, but the outcomes of interactions among associates are fundamental to draw valid conclusions about the functional structure of the network. Ecological networks studies in general gave little importance to know the true outcomes of interactions and how they may change over time. We evaluate the dynamic of an interaction network between ants and plants with extrafloral nectaries, by verifying the temporal variation in structure and outcomes of mutualism for the plant community (leaf herbivory). To reach this goal, we used two tools: bipartite network analysis and experimental manipulation. The networks exhibited the same general pattern as other mutualistic networks: nestedness, asymmetry and low specialization and this pattern was maintained over time, but with internal changes (species degree, connectance and ant abundance). These changes influenced the protection effectiveness of plants by ants, which varied over time. Our study shows that interaction networks between ants and plants are dynamic over time, and that these alterations affect the outcomes of mutualisms. In addition, our study proposes that the set of single systems that shape ecological networks can be manipulated for a greater understanding of the entire system.

Natural history and biology of Chlamisus minax Lacordaire (Chrysomelidae: Chlamisinae)

Although very abundant in the Neotropics, there is little information about the biology, ecology and natural history of Brazilian Chlamisinae beetles. In the present study we investigated directly in the Cerrado vegetation the aspects of natural history and biology of Chlamisus minax Lacordaire. The results showed that the species has annual cycle and the adults are present in the field during the spring and summer when the reproduction occurs. The females cover their eggs with a mantle, and later on the rests of the egg and faeces are added by the larva to the mantle to produce a protective case. The six larval morpho-stages are herbivorous and feed on floral buds of Heteropterys pteropetala A. Juss. (Malpighiaceae). The larvae pupate in the host plants and after that they fall on the ground remaining in diapause between April and October. This is the first study to investigate the biology and natural history of a Brazilian Chlamisinae beetle directly in the field.

Individual-based ant-plant networks: diurnal-nocturnal structure and species-area relationship.

Despite the importance and increasing knowledge of ecological networks, sampling effort and intrapopulation variation has been widely overlooked. Using continuous daily sampling of ants visiting three plant species in the Brazilian Neotropical savanna, we evaluated for the first time the topological structure over 24 h and species-area relationships (based on the number of extrafloral nectaries available) in individual-based ant-plant networks. We observed that diurnal and nocturnal ant-plant networks exhibited the same pattern of interactions: a nested and non-modular pattern and an average level of network specialization. Despite the high similarity in the ants’ composition between the two collection periods, ant species found in the central core of highly interacting species totally changed between diurnal and nocturnal sampling for all plant species. In other words, this “night-turnover” suggests that the ecological dynamics of these ant-plant interactions can be temporally partitioned (day and night) at a small spatial scale. Thus, it is possible that in some cases processes shaping mutualistic networks formed by protective ants and plants may be underestimated by diurnal sampling alone. Moreover, we did not observe any effect of the number of extrafloral nectaries on ant richness and their foraging on such plants in any of the studied ant-plant networks. We hypothesize that competitively superior ants could monopolize individual plants and allow the coexistence of only a few other ant species, however, other alternative hypotheses are also discussed. Thus, sampling period and species-area relationship produces basic information that increases our confidence in how individual-based ant-plant networks are structured, and the need to consider nocturnal records in ant-plant network sampling design so as to decrease inappropriate inferences.

Loss and gains in ant–plant interactions mediated by extrafloral nectar: fidelity, cheats, and lies

All mutualistic plant–animal interactions are mediated by costs and benefits in relationships where resources (from plants) are exchanged by services (from animals). The most common trading coin that plants offer to pay for animal services is nectar; the main servers are hymenopterans. Extrafloral nectar (EFN) is produced in almost all aboveground plant parts not directly related with pollination, and their true function has long been an issue of discussion among naturalists and will be our main subject. The protective function of extrafloral nectaries (EFNs) is reviewed and considered with an alternative hypothesis, presenting not only ants, but also spiders and wasps as potential and effective agents in these protective interactions. Despite their likely relevance, the phenological variation (mainly sequential flowering and resprouting) of host plants mediating these interactions have been generally ignored. We discuss how the outcomes of each ant–EFN bearing plant interaction vary depending on physical and biotic changes in interacting organisms (internal factors such as phenology and species identity) as well as in their environments (external factors such as climatic variation), all of which may modify the character of each interaction. We propose that ant–EFN bearing plant interactions serve an excellent and unique model to test the “Geographic Mosaic Theory” of coevolution providing us a more clear view of how evolution has structured these plant–animal ecological networks.

Cooperation in the neotropical pseudoscorpion, Paratemnoides nidificator (Balzan, 1888): feeding and dispersal behavior

Abstract.Social behavior is rare among arachnids, and “permanent-sociality” is a strategy documented only in a few spider species. Here we describe the feeding and dispersal behavior of Paratemnoides nidificator, a Neotropical pseudoscorpion presenting “non-territorial permanent-sociality”. Field and laboratory observations (100 hours and 200 sessions over four years) and manipulative experiments revealed that P. nidificator is a generalist predator that lives in rough bark of trees, in groups of 2 to 175 individuals (42.62 ± 28.27; N=35 colonies; solitary individuals were never found), including reproductive adults and nymphs. Individuals in groups cooperatively capture prey four times larger than solitary individuals. Adult hunters share food with siblings. Reproduction in natural conditions occurs during the hot/wet season, when food availability is high. Prey diversity and abundance seem to be the main factor limiting reproduction in this species. Phoresy (attachment to a transporter animal) is the basic mode of dispersion in P. nidificator. Grouped individuals use large animals as vectors for dispersal, and once established they use the vector as the first food item of the new colony. However, they can also disperse by colony fission, newly documented herein for this taxon. The elaborate, cooperative behavior in P. nidificator is unique among pseudoscorpions and represents an excellent model for studies on the evolution of sociality in invertebrates.