Emmanuel D. Almada

Are gall midge species (Diptera, Cecidomyiidae) host-plant specialists?

Despite the speciose fauna of gall-inducing insects in the Neotropical region, little is known about their taxonomy. On the other hand, gall morphotypes associated with host species have been extensively used as a surrogate of the inducer species worldwide. This study reviewed the described gall midges and their galls to test the generalization on the use of gall morphotypes as surrogates of gall midge species in the Brazilian fauna. We compiled taxonomic and biological data for 196 gall midge species recorded on 128 host plant species. Ninety two percent of those species were monophagous, inducing galls on a single host plant species, whereas only 5.6% species were oligophagous, inducing galls on more than one congeneric host plant species. Only four species induced galls on more than one host plant genus. We conclude that gall morphotypes associated with information on the host plant species and attacked organs are reliable surrogates of the gall-inducing species.

Gall inducing arthropods from a seasonally dry tropical forest in Serra do Cipó, Brazil

Highly diverse forms of galling arthropods can be identified in much of southeastern Brazils vegetation. Three fragments of a Seasonally Dry Tropical Forest (SDTF) located in the southern range of the Espinhaco Mountains were selected for study in the first survey of galling organisms in such tropical vegetation. Investigators found 92 distinct gall morphotypes on several organs of 51 host plant species of 19 families. Cecidomyiidae (Diptera) was the most prolific gall-inducing species, responsible for the largest proportion of galls (77%) observed. Leaves were the most frequently galled plant organ (63%), while the most common gall morphotype was of a spherical shape (30%). The two plant species, Baccharis dracunculifolia (Asteraceae) and Celtis brasiliensis (Cannabaceae), presented the highest number of gall morphtypes, displaying an average of 5 gall morphotypes each. This is the first study of gall-inducing arthropods and their host plant species ever undertaken in a Brazilian SDTF ecosystem. Given the intense human pressure on SDTFs, the high richness of galling arthropods, and implied floral host diversity found in this study indicates the need for an increased effort to catalogue the corresponding flora and fauna, observe their intricate associations and further understand the implications of such rich diversity in these stressed and vulnerable ecosystems.

Gall-inducing insect species richness as indicators of forest age and health.

ABSTRACT The changes in the plant community that occur during the process of succession affect the availability of resources for the community of herbivores. In this study, the richness of galling insects was evaluated in restored stands of Amazonian tropical rain forest of several ages (0–21 yr), as well as in areas of primary forest in Brazil. The richness of gallers increased with the age of the restored stands. Fifty-eight percent of the variation in the richness of galling insects was explained by forest stand age, but an increase in richness was observed at intermediate stages of succession. The greatest similarity among groups was found between the initial successional stages and intermediate ones. The results indicate a recovery of both host plants and insect community and that succession directly affects the richness and composition of these herbivores.

Galling Insects in the Pantanal Wetland and Amazonian Rainforest

It were collected 133 morphospecies of galling insects on 75 host plant species in the Pantanal forest patches while studies compilation pointed the interesting record of 1,549 galling morphospecies in 66 botanical families, 251 genera and 713 species of host plants in the Amazonian forests. No difference was observed in the number of galling species between Pantanal patch edge and interior. However, dissimilarity in galling species composition was verified in the patch habitats. To date, galling insect fauna of Pantanal region have not been properly sampled. In the Amazonian forests and Pantanal wetlands, galling species richness was strongly affected by hygrothermal and nutritional stress, even though mediated by soil fertility, topography, and flooding. Upper canopy of the Amazonian rainforests was the most speciose environment for galling fauna. Their microclimatic conditions, similar to scleromorphic/sclerophyllous vegetations, favor the attack by these herbivores. Besides, the Amazonian super-host and host/non-host plant diversity seems to play an important role on the richness and distribution patterns of galling insects.

Understory host plant and insect gall diversity changes across topographic habitats differing in nutrient and water stress in the Brazilian Amazon rainforest

As variacoes topograficas encontradas nas florestas de terra firme sao acompanhadas por fortes mudancas no conteudo de argila e concentracao de nutrientes do solo, criando, portanto, diferentes condicoes hidricas e nutricionais para plantas e as comunidades de herbivoros associadas. O objetivo do presente estudo foi avaliar a riqueza e composicao de especies de insetos galhadores e suas plantas hospedeiras ao longo de um gradiente topografico com habitats que diferem quanto ao estresse hidrico e nutricional. Dezenove parcelas de 250 x 3 m foram estabelecidos aleatoriamente em habitats de vertente, plato, transicao plato-vertente e baixio, claramente distintos em areas de terra firme. Todas as dicotiledoneas com 1 a 3 metros de altura foram examinadas quanto a presenca de galhas de insetos. As galhas encontradas foram coletadas e insetos galhadores foram classificados em morfoespecies. A riqueza de galhadores e de plantas hospedeiras diferiram significativamente entre os habitats estudados, e como esperado, foi maior no habitat de vertente. As areas mais umidas (baixios) apresentaram menor riqueza de plantas hospedeiras no sub-bosque e, consequentemente, um numero menor de especies de galhadores. Os resultados das analises de PERMANOVA e PERMDISP demonstraram que a composicao da especie de insetos galhadores variou significativamente entre as areas de floresta de terra firme. No entanto, essas diferencas estruturais na composicao das especies podem ser devidas a dispersao desigual da variabilidade entre os habitats. Nossos dados sugerem que a heterogeneidade espacial, tal como o mosaico de status hidrico e nutricional do solo associado as condicoes topograficas, pode afetar plantas hospedeiras e insetos galhadores associados.