No abstract

Physical disturbances, such as fire, may affect the relationship between ants and plants. We evaluated the extent to which severe fires alter the protective effect of ants against the herbivores of an extrafloral-nectary bearing tree. We performed an ant removal experiment and sampled the ant fauna from the same trees over 4 years: the pre-fire year, the fire-year, and again 1 and 2 years later. Ants reduced insect herbivory in the pre-fire year and in the fire-year but failed to provide any plant protection in the two years after fire. The magnitude of the ant effect on herbivory did not differ between the pre-fire year and the fire-year. Fire reduced the abundance of ants with strictly arboreal-nesting habits. However, in the fire year (but not in the subsequent ones), this decline was compensated by an increase in the abundance of arboreal generalists and ground-nesting ants foraging in trees. Our results indicate that severe fires can affect the strength and direction of the ant effects on herbivory by altering the structure of the arboreal ant community and the abundance of insect herbivores. Fire disturbance is thus an important factor of conditionality of ant-plant mutualisms in fire-prone habitats, like the Cerrado savannas.

No abstract

Astyanax paranae Eigenmann, 1914 é um pequeno caracídeo conhecido como lambari-do-rabo-vermelho, ocorrendo em vários rios das sub-bacias do alto rio Paraná. Tendo em vista que as características ambientais como disponibilidade de recursos, diversidade de habitats entre outras podem selecionar atributos específicos possibilitando diferenciações morfológicas, testamos a hipótese de que ambientes diferentes podem influenciar características ecomorfológicas distintas entre as populações. Analisamos a ecomorfologia de Astyanax aff. paranae oriundos de três córregos localizados no município de Apucarana pertencentes a diferentes bacias hidrográficas: córregos Jurema (bacia do rio Pirapó), Biguaçú (bacia do rio Ivaí) e Japira (bacia do rio Tibagi). Para testar as diferenças foram utilizados 15 exemplares de A. aff. paranae de cada população, sendo tomadas 26 medidas morfométricas e calculadas seis áreas, de maneira que foram calculados 22 índices ecomorfológicos. Para evidenciar diferenças ecomorfológicas entre os espécimes foram realizados Análises de Variáveis Canônicas (AVC) e um teste "post hoc" de comparações pareadas de Hotelling. Na análise de comparações pareadas entre as populações de A. aff. paranae nos córregos amostrados, o córrego Japira apresentou diferenças estatísticas significantes em relação ao córrego Biguaçú. As diferenças ecomorfológicas entre as populações do córrego Biguaçu e as dos córregos Jurema e Japira podem estar relacionadas com as características biogeográficas de cada bacia. Além disso, as particularidades de cada ambiente, como as interações bióticas e abióticas provida pela qualidade ambiental nos córregos Jurema e Japira podem ser influências, mesmo que de maneira discreta, frente às peculiaridades ecológicas de cada organismo. Palavras-chave: córregos, rio Ivaí, rio Paranapanema, isolamento geográfico, qualidade ambiental. ABSTRATC: Astyanax paranae Eigenmann, 1914 is a small characid known as lambari-do-rabo-vermelho that occurs in several rivers of Upper Paraná River Basin. Considering that environmental characteristics as resource availability, habitat diversity and many others may select specific attributes enabling morphological differentiation, we tested the hypothesis that different environments may influence distinct ecomorphological characteristics between populations. We analyzed Astyanax aff. paranae belonging to three streams from different basins in the Apucarana city: Jurema (Pirapo river basin), Biguaçu (Ivai river basin) and Japira (Tibagi river basin) streams. To test the ecomorphological difference we used 15 individuals of A. aff paranae of each population, to take 26 morphometric measures and calculate six areas, obtaining 22 ecomorphological rates. We used Canonical Variate Analysis (CVA) and a paired Hotelling's test to evidence ecomorphological differences between the specimens. Japira stream's population of A. aff. paranae presented statistical difference when compared with Biguaçu stream by the analysis of paired comparisons. The ecomorphological diferences be...

Carbohydrates and proteins are essential to maintain the basic functions of animals. Over the course of one year we conducted a factorial experiment to determine the influence of carbohydrate (sucrose) and protein supplementation on the thermal tolerance, trophic position, overall abundance, species richness and composition, and on the strength of the protective effects of arboreal ants on their host tree (Caryocar brasiliense). Using Azteca ants as a model we found evidence of dietary and thermal plasticity among arboreal ants as colonies supplied with protein increased their trophic level relative to colonies that received no protein. Colonies that received sucrose increased their thermal tolerance on average by 1.5 °C over a six-month period, whereas those that did not receive sucrose did not change their thermal tolerance. Overall ant abundance was lower in control trees than in those that received any nutrient addition treatment. Species richness was also lower in control trees, but those receiving sucrose presented more species than those receiving only protein. There was greater similarity in species composition between the trees that received sucrose than between these and those receiving only protein or just water as control. Trees whose ant colonies received sucrose presented lower levels of leaf damage than those that did not. Overall, these results indicate that food resources can modulate the population and community ecology of arboreal ants as well as their interaction with the host trees. Interestingly, although arboreal ants are thought to be N-limited, it was the supplementation of sucrose—not protein—that elicited most of the responses.