Ácaros e domácias foliares: sem evidências de mutualismo em plantas de Coffea arabica

We conducted experiments by blocking off pit-like domatia from old and new leaves of Coffea arabica L., using tiny resin drops, to investigate the role of domatia on i) mite abundance at the community level and on ii) leaf damages. More than 77% of the mites collected were predators, whereas 19 and 3.3% were omnivores and phytophages, respectively. Domatia blockage treatment had no influence either on mite abundances or leaf damages. However, predatory and omnivorous mites were more abundant on new than on the old leaves; phytophagous mites occurred at very low density and occupied only plants having open domatia. The absence of mutualism between mites and C. arabica probably occurred because the entrances of domatia were too small and did not enable the entry of fitoseid predators in these structures.Domácias são pequenas estruturas presentes na junção entre as nervuras principal e secundárias das folhas de muitas espécies de plantas, que podem mediar interações mutualísticas entre ácaros e plantas. Em experimento, nós bloqueamos as domácias em formato de covas de folhas novas e velhas de Coffea arabica L. com gotas de resina, a fim de investigar o seu papel i) na abundância de ácaros na comunidade e ii) nos danos foliares. Mais de 77% dos ácaros coletados são predadores, enquanto 19 e 3,3% são onívoros e fitófagos, respectivamente. Não houve influência do bloqueio das domácias tanto na abundância quanto nos danos foliares. Entretanto, os ácaros predadores e micófagos foram mais abundantes nas folhas novas do que nas velhas; os ácaros fitófagos ocorreram em pequena densidade e ocuparam somente as plantas com domácias abertas. A ausência de mutualismo entre os ácaros e plantas de C. arabica pode ter ocorrido porque as entradas das domácias analisadas eram muito pequenas, não permitindo a entrada dos predadores fitoseídeos nessas estruturas.2734Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Ontogenetic succession in Amazonian ant trees

In the tropical rain forest of the Central Amazon, a small guild of specialized plant-ants nest exclusively inside the leaf domatia of Tachigali (Caesalpinaceae). Since normally each plant houses a single ant colony, the number of unoccupied plants in the environment is quite low and the number of potential colonizer queens is high, the conditions for intense intra and interspecific competion for nesting site are set. This study describes an intriguing ecological pattern that explains how this ant guild can coexist using exclusively Tachigali plants as nesting site. We found that each of the eight different ant species occurs in plants of different heights (Kruskal-Wallis test statistics = 148.6, d.f. = 7, P < 0.001). This spatial pattern emerges due to interspecific ant colony replacements along the ontogeny of the tree. We discuss that this pattern can be seen as an ontogenetic succession since an organism's ontogeny is defining a non-seasonal, directional and continuous pattern of colonization and extinction of interacting populations. Ontogenetic succession can be classified at the same level of another class of succession that has been termed degradative succession. The ontogenetic succession view highlights chains of indirect interactions that are mediated by the focal organism and has the potential to produce unexpected outcomes in population interactions and community structure. We suggest that ontogenetic succession should be widespread in nature and that the concept can contribute to our understanding of the temporal and spatial organization of the world biodiversity

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

We conducted experiments by blocking off pit-like domatia from old and new leaves of Coffea arabica L., using tiny resin drops, to investigate the role of domatia on i) mite abundance at the community level and on ii) leaf damages. More than 77% of the mites collected were predators, whereas 19 and 3.3% were omnivores and phytophages, respectively. Domatia blockage treatment had no influence either on mite abundances or leaf damages. However, predatory and omnivorous mites were more abundant on new than on the old leaves; phytophagous mites occurred at very low density and occupied only plants having open domatia. The absence of mutualism between mites and C. arabica probably occurred because the entrances of domatia were too small and did not enable the entry of fitoseid predators in these structures