Richness of hymenopteRous galls fRom south ameRica

An overview of hymenopterous galls from South America is presented here based on literature as well as on data from the insect gall collection of the Museu Nacional/UFRJ. Seventy-three galls have been recorded on 71 host plants. Myrtaceae and Fabaceae are the plant families with the greatest number of galled species and gall morphotypes. Gall richness per plant species varied from one to two. The stem and bud were the most galled plant organs. The gallers comprise eight hymenopteran families, the best-represented being Eulophidae, Eurytomidae, and Cynipidae. Geographic records are restricted to six countries, and the majority is from Brazil. Key-Words: Diversity; Geographical distribution; Insect plant interaction.


IntroductIon
Galls are predictable and consistent plant deformations that occur in response to feeding or other stimuli by foreign organisms (Gagné, 1994).The gall formation is characterized by abnormal growth of plant tissues by cell hypertrophy and hyperplasia (Price, 2005).Insect galls are considered the most sophisticated herbivore interactions of nature (Shorthouse et al., 2005).Galling insects have the ability to manipulate the development of plant tissue and promote its growth (Stone & Schönrogge, 2003).The development of these structures has resulted from an adaptive strategy of many insects to obtain food and even protection against predators (Stone & Schönrogge, 2003).Among the insects, Diptera, Lepidoptera, Hemiptera, Coleoptera, Hymenoptera and Thysanoptera include galling species (Mani, 1964).
Nevertheless, little is known about the diversity of hymenopterous galls in South America, as data are scattered in several insect gall inventories.There is a single previous compilatory study, published by Houard in 1933, which includes Hymenopterous galls.This author organized a catalog of galls induced by arthropods and nematodes.But even in Houard, 1933, the information about Hymenopteran gallers is pulverized.The present work is the first attempt to gather and upgrade this information.This paper aims to answer the following questions: (1) How many hymenopterous galls have been recorded in South America?(2) How many plant families are galled by Hymenoptera?(3) Which plant families are the most galled?(4) Is there a preference for any plant organ?(5) What is known about the taxonomy of these gallers?(6) Which hymenopteran families induce galls in this region?(7) Among them, which are the most common?and (8) What is known about the geographic distribution of these gallers?
The Hymenopteran species names were checked in the Universal Chalcidoidea Database (Noyes, 2011).The botanical names and authors were checked in the websites Tropicos® (Tropicos.org)and Angiosperm Phylogeny Group III.

results And dIscussIon
Seventy-three hymenopterous galls have been recorded in South America.These galls occurred on 71 plant species distributed among 21 plant families of angiosperms.No galls were recorded on gymnosperms.The great majority of the host plants (about 90%) belong to dycotiledons.Only two families of monocotyledons were galled: Araceae and Orchidaceae.Myrtaceae and Fabaceae are the plant families with the greatest number of host plant (18 and 16, respectively) and gall morphotypes (18 and 19, respectively).These two families comprise about 50% of the recoded galls (Table 1).
The South American fauna of hymenopteran gallers differ from Holarctic fauna, mainly by the absence of gall forming sawflies (Tenthredinidae) and by the higher diversity of gall-forming Eulophidae, Eurytomidae and Cynipidae.The geographic records are restricted to six countries, and the majority is from Brazil (around 68%; Figure 2), where most of the surveys have been developed.

FIgure 1 :
FIgure 1: Distribution of Hymenopteran gallers from South America per plant organ.

tAble 1 :
Distribution of hymenopterous galls from South America per host plant families and species.

tAble 2 :
Distribution of Hymenopteran gallers from South America per plant, plant organ and country.

tAble 3 :
Distribution of the records of Hymenopteran gallers from South America per country.Distribution of Hymenopteran gallers (records at order category) from South America per plant, plant organ and country.