Ant pollination of Paepalanthus lundii (Eriocaulaceae) in Brazilian savanna.

BACKGROUND AND AIMS: Ant-plant associations are widely diverse and distributed throughout the world, leading to complex ecological networks. Regarding ant-plant mutualism, ant pollination is a very rare interaction and few studies have shown the role of ants as pollinators. Therefore, we aimed to evaluate the role of ants as effective pollinators of Paepalanthus lundii (Eriocaulaceae) in a Brazilian savanna. METHODS: Fieldwork with experimental manipulation was conducted to evaluate the fitness of P. lundii, considering potential pollinators. For this, we mainly observed the number of seeds produced in different conditions: control, ant exclusion, exclusion of flying insects, and exclusion (entomophily test) of both ants and flying insects. Furthermore, we evaluated all floral visitors throughout the day, stigma receptivity, the numbers of male and female flowers, and patterns of species co-occurrence, which can indicate the presence of different pollinators in the plants at the same time. KEY RESULTS: We observed a relation between seed production and ant visits; Camponotus crassus was the most frequent floral visitor and the most effective pollinator. Also, we observed a statistical difference between the numbers of male and female flowers produced, with a greater number of male flowers. Furthermore, P. lundii presented flowering asynchrony, with 12 different types of maturation sequence, which indicates a cross-pollination system. Lastly, we observed an overlap of the greatest abundance of C. crassus and the time of plant stigmatic receptivity, and a pattern of non co-occurrence of ants, which shows the pollinator role of this ant. CONCLUSIONS: Our data provide evidence that previous generalizations neglecting the importance of ants as pollinators are wrong. Brazilian savanna can reveal a lot about the ant-pollination syndrome, since this environment presents peculiar characteristics related to this association. Thus, this study has great significance for the understanding of the ant-pollination syndrome, and for the understanding of the complex ecological networks present in these dry arid systems.

Variation in the outcomes of an ant-plant system: fire and leaf fungus infection reduce benefits to plants with extrafloral nectaries.

Interactions between species are evolutionary malleable and may suffer changes in small timescales. Environmental disturbances, such as fire, can deeply affect species interactions, but how they influence the outcome of a mutualistic interaction has yet to be studied. In order to test the hypothesis that an environmental disturbance, in this case fire, may produce differences in the outcome of the association of ants with the extrafloral-nectaries-bearing plant Qualea multiflora Mart. (Myrtales: Vochysiaceae), a previous study was replicated, but this time after fire incidence, at the same study site and with the same plant species. Eight ant species visited Q. multiflora, and the most abundant genera were Crematogaster, Cephalotes, and Camponotus. Herbivores were found in branches with and without ants with no statistical difference, but foliar herbivory was always higher in branchs where ants were absent. Leaves were infested by fungi, and fungi spots were higher in branches where ants were present. Compared to the previous study, it was clearly observed that ant benefits to Q. multiflora varied over time. The most common ant species still protected leaves against chewing herbivores, but a new kind of leaf damage appeared, namely fungi spots. Data also support that ants may be acting as vectors of fungi spores on plants, as ant visited branches had higher fungus incidence than non-visited branches. Fire is a major source of disturbance in tropical savannas, and we suggest that it can cause strong variation in the outcomes of interactions between ants and plants with extrafloral nectaries in the Brazilian tropical savanna.

Capybaras and ticks in the urban areas of Uberlândia, Minas Gerais, Brazil: ecological aspects for the epidemiology of tick-borne diseases.

In Brazil capybara, the biggest existing rodent species, and associated tick species, Amblyomma cajennense and Amblyomma dubitatum, are undergoing an unplanned host and parasite population expansion in both urban and rural areas. However, scientific information about such issue, particularly in urban areas, is scanty. Such rodent and ticks are associated in some municipalities, particularly in southeastern Brazil, with the transmission of the highly lethal Rickettsia rickettsia caused spotted-fever. In this study ecological aspects related to the establishment and expansion of capybaras and ticks in urban areas of Uberlândia, Minas Gerais State, Brazil were evaluated. For this purpose, capybara and tick abundance in four urban areas and an ecological reserve was determined. Abundance of capybaras varied between areas and over the sampling period and these differences were related to human activities. A positive correlation was found between capybara and tick abundance, however, the tick species had an uneven distribution within the municipality and environmental factors rather than host availability were blamed for such. On the whole these observations show that capybara populations in urban areas are associated to high environmental infestation of ticks and the increased risk of bites and of pathogen transmission to humans. At the same time the uneven distribution of tick species might implicate in an unequal risk of tick-borne diseases within the same urban area.

Resource defense polygyny by Hetaerina rosea Selys (Odonata: Calopterygidae): influence of age and wing pigmentation.

Current evidence suggests that in Hetaerina damselflies males exhibit lek mating system. In this study, in order to answer if the same occurs in Hetaerina rosea Selys, we manipulated vegetation substrates used as territories and quantified the number of visiting females, males defending territories and fight intensity. We also examined whether body size and wing pigmentation are selectable traits in male-male competition, and if age affects male territorial behavior. Our results showed that males with larger pigmented areas won more contests, independently of body size. Old males changed from territoriality to sneaking strategy. Contrary to other Hetaerina species, males of H. rosea do not display lek behavior, but defend resources according to the resource defense polygyny strategy.

Resource Defense Polygyny by Hetaerina rosea Selys (Odonata: Calopterygidae): Influence of Age and Wing Pigmentation

Current evidence suggests that in Hetaerina damselflies males exhibit lek mating system. In this study, in order to answer if the same occurs in Hetaerina rosea Selys, we manipulated vegetation substrates used as territories and quantified the number of visiting females, males defending territories and fight intensity. We also examined whether body size and wing pigmentation are selectable traits in male-male competition, and if age affects male territorial behavior. Our results showed that males with larger pigmented areas won more contests, independently of body size. Old males changed from territoriality to sneaking strategy. Contrary to other Hetaerina species, males of H. rosea do not display lek behavior, but defend resources according to the resource defense polygyny strategy.

Seasonal variation of ground spiders in a Brazilian Savanna

The Brazilian Savanna Ecoregion (Cerrado) is one of the richest biomes in the world, with a characteristic highly seasonal climate a dry season between May and September and a rainy season from October through April. Ground-dwelling spiders from three Cerrado phytophysiognomies, "campo cerrado", "cerrado" and "cerradão", were sampled using pitfall traps during two years, totaling 111 species and 3,529 individuals. The abundance of individuals and species richness was higher during the wet season. Fifty-eight species were captured exclusively during that period, whereas only nineteen were restricted to the dry season. Only two species were found in all samples. The number of juveniles was higher than the number of adults in all phytophysiognomies and in all species during both seasons. The highest abundance was registered in October and the lowest in April. Overall sex ratio was male-biased in all vegetation types sampled. Distinct climate variables affected the abundance of spiders depending on sex, age and vegetal physiognomy where they were sampled. This study involved the longest sampling of spider abundance and diversity on the ground of a Brazilian Savanna. (

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

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.