Unexpected high diversity of galling insects in the Amazonian upper canopy: The savanna out there

A relatively large number of studies reassert the strong relationship between galling insect diversity and extreme hydric and thermal status in some habitats, and an overall pattern of a greater number of galling species in the understory of scleromorphic vegetation. We compared galling insect diversity in the forest canopy and its relationship with tree richness among upland terra firme, várzea, and igapó floodplains in Amazonia, Brazil. The soils of these forest types have highly different hydric and nutritional status. Overall, we examined the upper layer of 1,091 tree crowns. Galling species richness and abundance were higher in terra firme forests compared to várzea and igapó forests. GLM-ANCOVA models revealed that the number of tree species sampled in each forest type was determinant in the gall-forming insect diversity. The ratio between galling insect richness and number of tree species sampled (GIR/TSS ratio) was higher in the terra firme forest and in seasonally flooded igapó, while the várzea presented the lowest GIR/TSS ratio. In this study, we recorded unprecedented values of galling species diversity and abundance per sampling point. The GIR/TSS ratio from várzea was approximately 2.5 times higher than the highest value of this ratio ever reported in the literature. Based on this fact, we ascertained that várzea and igapó floodplain forests (with lower GIA and GIR), together with the speciose terra firme galling community emerge as the gall diversity apex landscape among all biogeographic regions already investigated. Contrary to expectation, our results also support the "harsh environment hypothesis", and unveil the Amazonian upper canopy as similar to vegetation habitats, hygrothermically stressed environments with temperature at lethal limits and high levels of leaf sclerophylly. © 2014 Julião et al

Phytoplasmas and disease symptoms of crops and weeds in the semi-arid tropics of the Northern Territory, Australia

This study used molecular techniques to investigate the little-known characteristics of phytoplasmas in the semi-arid tropics of northern Australia in sesame, mung bean and peanut crops, and in adjacent non-crop species. Five new records of plant species associated with phytoplasma diseases are reported. No phytoplasmas were associated with fasciation but four phytoplasma strains were linked with other symptoms. Sweet potato little leaf variant Vinca 4, the most prevalent phytoplasma, was associated with symptoms of little leaf, or little leaf and phyllody, in all hosts (crop and non-crop species) except sesame, where it was most often associated with floral dieback. Tomato big bud was found only in sesame showing phyllody. Pigeon pea little leaf occurred in one mung bean and one peanut plant with little leaf and phyllody, and one non-crop species with yellowing and rosette formation. Waltheria little leaf was found in a single non-crop individual with little leaf and bunching symptoms. The findings show that adjacent non-crop species have the potential to function as reservoirs of phytoplasma disease for crop species but symptoms alone are not sufficient to diagnose specific phytoplasma strains