Predation success by a plant-ant indirectly favours the growth and fitness of its host myrmecophyte.

Mutualisms, or interactions between species that lead to net fitness benefits for each species involved, are stable and ubiquitous in nature mostly due to "byproduct benefits" stemming from the intrinsic traits of one partner that generate an indirect and positive outcome for the other. Here we verify if myrmecotrophy (where plants obtain nutrients from the refuse of their associated ants) can explain the stability of the tripartite association between the myrmecophyte Hirtella physophora, the ant Allomerus decemarticulatus and an Ascomycota fungus. The plant shelters and provides the ants with extrafloral nectar. The ants protect the plant from herbivores and integrate the fungus into the construction of a trap that they use to capture prey; they also provide the fungus and their host plant with nutrients. During a 9-month field study, we over-provisioned experimental ant colonies with insects, enhancing colony fitness (i.e., more winged females were produced). The rate of partial castration of the host plant, previously demonstrated, was not influenced by the experiment. Experimental plants showed higher δ(15)N values (confirming myrmecotrophy), plus enhanced vegetative growth (e.g., more leaves produced increased the possibility of lodging ants in leaf pouches) and fitness (i.e., more fruits produced and more flowers that matured into fruit). This study highlights the importance of myrmecotrophy on host plant fitness and the stability of ant-myrmecophyte mutualisms.

Is Rhodnius nasutus (Hemiptera; Reduviidae) changing its habitat as a consequence of human activity?

Rhodnius nasutus, a triatomine species autochthonous in the Brazilian Northeast, is primarily associated with the Copernicia prunifera palm tree (Carnauba). For the first time, the colonization of this triatomine in another tree species is reported. To investigate the existence of an infected triatomine focus located in a periurban area of the county of Jaguaruana, Ceará, situated in the Brazilian Northeast, where soil is greatly altered and natural vegetation scarce, an entomological survey was performed. During 2 consecutive days in August 2006 and 4 in December 2006, with the aid of live-bait traps, nine C. prunifera palms and seven Licania rigida trees (Oiticica), among other typical trees of the region, were sampled. In April 2007, 13 L. rigida trees and five C. prunifera palm trees were newly sampled. Considering the three investigation periods, a total of 20 R. nasutus specimens in C. prunifera and 52 in L. rigida were captured, in all developmental stages, 12.5 and 20.7%, respectively, harboring T. cruzi-like protozoa. The authors suggest that environmental damages are facilitating the ability of this species to colonize other trees besides palms.