Insect galls of the Reserva Biológica União, Rio de Janeiro, Brazil

Abstract

Abstract: Several inventories of insect galls have been performed in the Atlantic Forest of Rio de Janeiro, mostly in restingas, whereas the other phytophysiognomies remain poorly sampled. The present study inventoried the insect galls of Reserva Biológica União (RJ), a protected area comprising mainly Ombrophilous Forest. Field work was performed every two months from January to October, 2013. Insect galls were collected, photographed, characterized and transported to the laboratory. Adults were obtained by rearing and immature stages by gall dissection. The insects were deposited in the Cecidomyiidae Collection of the Museu Nacional. A total of 153 gall morphotypes were found on plants representing 37 plant families, 69 genera, 55 species and 53 morphospecies. Among them, two plant genera and five species were reported for the first time as host plants in Ombrophilous Forest. REBIO União showed little similarlity of host plant species and insect gall morphotypes when compared with other investigated Ombrophilous Forest areas. The leaf was the most attacked plant organ as expected. Asteraceae, Bignoniaceae, Fabaceae and Myrtaceae, and Mikania (Asteraceae) and Myrcia (Myrtaceae) were the richest host families and genera, respectivey, in number of gall morphotypes, all previously indicated as superhosts by other Brazilian Ombrophilous Forest inventories, except Bignoniaceae. Their great species richness may be related to their great gall richness, adding evidence in support of the taxon size hypothesis. Fusiform and globose galls were the most frequent, green was the predominant color, and most morphotypes did not present an indumentum. The highest gall richness was recorded in June and August. The gallers were distributed among Diptera (Cecidomyiidae), Lepidoptera, Hymenoptera, Hemiptera and Thysanoptera, with the first being predominant, following a global pattern. Eight gall-inducing species are recorded for the first time in REBIO União and four in Ombrophilous Forest. About 25% of the gall morphotypes were occupied by dwellers other than those that created the gall. They comprised parasitoids (Hymenoptera), inquilines (Diptera: Sciaridae and Muscomorpha, Hemiptera, and Lepidoptera) and successors (Psocoptera, mites, and Hymenoptera: Formicidae). Although these taxa were previously reported by Brazilian inventories of insect galls, 12 new association with plants are recorded. The amount of new records reinforces the importance of inventories.