The insect gall collection of the Museu Nacional / Universidade Federal do Rio de Janeiro : biome cerrado , rupestrian fields

Abstract An inventory of the insect gall from Brazilian savanna (Cerrado) was elaborated based on samples of the collection of the Museu Nacional, Universidade Federal do Rio de Janeiro. Data on localities and host plants were obtained from the labels and information about the gall morphology (plant organ of occurrence, shape, and presence of trichomes) by observing the samples. The galling species was determined based on the literature. The collection includes 131 morphotypes of galls from Cerrado, obtained from 71 host plant species distributed in 50 genera and 30 botanical families (Table 1). All galls were collected in rupestrian fields (a rare vegetation physiognomy of the Brazilian Cerrado) in the state of Minas Gerais. As the collection comprises a great diversity of insect galls, it can be considered representative of this physiognomy.


Introduction
Plant galls are remarkably close associations between arthropods (usually insects) and plants, in which the plant produces an abnormal growth of tissue in response to a specific stimulus from the invading organism.Thus gallformers have the ability to manipulate the growth and development of plant tissues (Shorthouse and Rohfritsch, 1992).
Galling insects are among the most specialised herbivores.From an evolutionary point of view, galls can be seen as adaptations that allowed some insect taxa to feed on high quality tissues, and protect themselves from natural enemies and harsh abiotic factors (Price et al., 1986).
The majority of galling insects are host-plant and plant-organ specific, and gall morphology is specific to each inducer (Floate et al., 1996).In addition, galls may be seen as extended phenotypes of their inducers (Weis et al., 1989).
The insect gall collection of the Museu Nacional, Universidade Federal do Rio de Janeiro began to be organised in 1992, with samples from restinga areas of the state of Rio de Janeiro.Since then, galls from other localities and biomes have been incorporated, increasing the representativeness of the collection.
The main aim of this paper is to elaborate an inventory of the gall collection of the Museu Nacional (MNRJ), focussing exclusively on Cerrado (Brazilian savanna).
The Cerrado covers some 2 million km 2 of Central Brazil, representing about 23% of the land surface of the country.In terms of area, it is exceeded only by the Amazonian forest (with approx.3±5 million km 2 ).The Cerrado region extends from the margin of the Amazonian forest to outlying areas in the southern states of São Paulo and Paraná, occupying more than 20° of latitude and an altitudinal range from sea-level to 1800 m (Ratter et al., 1997).
Rupestrian fields are a unique and rare vegetation physiognomy of the Brazilian Cerrado.They spread over the plateaus and mountain chains of the states of Minas Gerais, Bahia, and Goiás, being exclusively found in the highlands of the Espinhaço mountain range and small disjunctions in southeastern and northeastern Brazil.They occur in areas above 900 m a.s.l., on shallow, Al-rich, waterand nutrient-deficient soils where rocky outcrops prevail (Giulietti et al., 1987;Benites et al., 2007), and include a very high number of endemic species (Giulietti et al., 1987;Giulietti and Pirani, 1988;Safford 1999;Rapini et al., 2002).The plant communities experience high daily thermal amplitudes, strong winds, high sun exposure and constant fires (Ribeiro and Fernandes, 2000;Jacobi et al., 2007).In this speciose physiognomy, plants are mainly sclerophyllous and herbaceous with scattered shrubs and trees comprising a mosaic of habitats (Giulietti et al., 1997).Most of the endangered species of the Brazilian Cerrado are endemic to the rupestrian fields (Menezes  and Giulietti, 2000), making this physiognomy especially important for plant conservation.

Material and Methods
The insect gall collection of the Museu Nacional was surveyed by the authors.Data on localities and host plants were obtained from the labels; the biomes were inferred based on the localities.
The collection comprises dried galls which are organised in small boxes by host plant names in alphabetical order.The boxes are arranged in wooden drawers covered with glass and these drawers are inserted in compactors (Figures 13, 14).

Results
The collection comprises 131 morphotypes of galls from Cerrado, which were obtained from at least 71 host plant species distributed in 50 genera and 30 botanical families (Table 1).All galls were collected in a same physiognomy: rupestrian fields.
The galls were observed on leaves, stems, apical and lateral bud, as well as on flowers (inflorescences, and peduncles), being leaf galls the most frequent galled plant organ (about 60%) (Figure 15).This result corroborates the world pattern pointed out by Houard (1933).
The gallers belong to six orders: Diptera, Coleoptera, Hemiptera, Lepidoptera, Hymenoptera, and Thysanoptera,     being Cecidomyiidae (Diptera) the most frequent galling insect (with 73%) (Figure 16), as in all other zoogeographic areas (Felt, 1940).Most part of the gallers are identified at family level (52%), 16% are not determined, 6% are identified at genus and 13% at species.These data reveal how the taxonomy of the gallers is still little studied.The total of the percentages is higher than 100% because some morphotypes were recorded on two plant organs.

Conclusion
The Cerrado gall collection of the Museu Nacional comprises exclusively samples of rupestrian fields from Minas Gerais, totalling 131 morphotypes.It can be considered representative of this physiognomy in Minas Gerais.As the Cerrado spreads over other Brazilian states (Figure 17), efforts to obtain samples from these areas are necessary in order to increase the representativeness of the gall collection of the Museu Nacional.

Figure 15 .
Figure 15.Distribution of gall morphotypes per plant organ.The total of the percentages is higher than 100% because some morphotypes were recorded on two plant organs.

Figure 16 .
Figure 16.Distribution of gall morphotypes per order of galling insect.

Table 1 .
Insect Galls of the Museu Nacional (MNRJ) collection, Universidade Federal do Rio de Janeiro.

Table 4 .
Distribution of gall morphotypes per shape.

Table 2 .
Distribution of gall morphotypes in the most galled plant families.

Table 3 .
Distribution of gall morphotypes in the most galled plant genera.