Gall-inducing insect inventories in Brazil: update, perspectives, and challenges

Galls and gall-inducing insect inventories have allowed us to understand patterns of species richness and differential distribution, and to map interactions between gall-inducing insects and host plants in different Brazilian biomes. Since the first formal inventory of gall-inducing insects, conducted in 1988 by Fernandes and collaborators in the Cerrado biome in Minas Gerais, studies on this topic have continued to increase. Over the past 35 years, there have been 64 inventories in over 185 locations, spanning 114 municipalities in 18 states across the five regions of Brazil, and involving 97 researchers. Despite the advances in recent decades, between 1988 and 2023, there has not been a significant increase in the number of publications. This is mainly due to the decrease in the number of papers published in the last years (2014–2023). We constructed a co-authorship network that shows some authors as important hubs in collaborations between researchers and institutions; however, some still exhibit low penetration and integration in the research network. The results showed that (i) there is a predominance of studies in southeast Brazil, in which predominates the Atlantic Forest and Cerrado; (ii) gall-inducing insects are abundant in any environment but dominant in sclerophyll conditions; (iii) gall-inducing insect richness is positively associated with host plant species richness; (iv) Fabaceae is the richest host family; and (v) Cecidomyiidae (Diptera) are the main gall inducers. In Brazil, 284 species of cecidomyiids, most of which induce gall formation, have been recorded. The majority of species have been described in the Atlantic Forest (184), followed by the Cerrado (70) and the Amazon Forest (31). However, it is important to note that there may be bias in the distribution of knowledge and a significant taxonomic gap that needs to be addressed. These results provide valuable insights for future research.