OCCURRENCE AND CHARACTERIZATION OF ENTOMOGEN GALLS IN PLANTS FROM NATURAL VEGETATION AREAS IN DELFINÓPOLIS , MG ,

In the present work we aimed to register the occurrence of galls, inductors, inquilines, and parasitoids in plants of three natural vegetation areas in Delfinópolis, MG, Brazil. Results obtained showed 22 types of galls collected from leaf, vein leaf, petioles, stem, and inflorescence of nineteen species belonging to fifteen distinct families. Concerning gall morphology, the following were collected: globoid, conicle, discoidal, fusiform, shell-shape, indefinite, and one substituition of an ovary by an immature. As principal inducers were found insects of the families Cecidomyiidae (Diptera), Psyllidae, and Diaspididae (Sternorrhyncha/ Hemiptera). As parasitoids the most common are of the Chalcidoidea superfamily (Hymenoptera) and, as occasional inquilines, Polyxenidae (Diplopoda) and Psocodea (Psocoptera). The results of this study contribute to existing of knowledge host-plant diversity and gall-associated insects in rocky fields, cerrado, and gallery forests.


INTRODUCTION
A galls is a pathologically developed vegetal tissue originating mechanically or chemically in stimulation of inductor agents.The process can be classified as hypertrophic or hyperplastic depending on the case.According to Mani (1964), these types develop through interaction of host plant and inducer, a hypothesis defended also by Abrahamson & McCrea (1986), who proposed that gall phenotype is a result of interaction between two genotypes.The first is of the inducer, for the stimulus, the second is of the host plant, for the reaction.In this way, it is expected that different gall makers produce different gall types in the same host.Gullan & Cranston (1994), and Hartley (1998), among other authors, defended this hypothesis, highlighting a complex specificity in the interacting gall makerhost plant.The high level of specificity of the gallmaker and host-plant association have been commented on by many authors (Mani, 1964;Abrahamson et al., 1998) and is regarded as one of the better systems for critically evaluating coevolution of involved organisms (Abrahamson & McCrea, 1986).
Other authors have performed studies involving occurrence and characterization of galls in diverse environments.Occhioni (1979Occhioni ( , 1981) ) obtained 35 types of galls in 34 families of plants in the restinga environment; Fernandes et al. (1988Fernandes et al. ( , 1997) ) related the occurrence of galls and their characterization in Brazilian cerrado and rocky field plants, and Scarelli-Santos & Urso-Guimarães (submitted) found 37 galls in 16 families of plants in cerrado vegetation.In Brazil, the principal host plants of insect galls belong to the Asteraceae, Fabaceae, Myrtaceae, and Anonnaceae families.
The present work aimed to morphologically describe galls, with mention of the inducers, so as to increase the knowledge about the diversity of galls and gall makers in three distinct areas of natural vegetation in Delfinópolis, MG, Brazil.

Physical characterization of the region
The Delfinópolis region is located in Minas Gerais State,, in the area surrounding Represa de Peixoto of the Rio Grande River.It is situated geomorphologically in Patamares da Canastra (the Canastra mountain range area), with altitudes varying from 600 to 1200 m (EMBRAPA, 1999).The climate is Cwa type, being temperate rainy and hot (C) with summer rains (w), the average temperature in the hottest month reaching more than 22ºC (a) (Köppen classification).The average annual rainfall is higher than 1630 mm, mainly between December and January with average rainfall indices of 100 mm; the driest period is from May to August with average precipitation of less than 40 mm (Nimer, 1989).

Studied vegetation
Minas Gerais presents a complex mosaic composed of forest areas, cerrado, high grassland, and rocky fields.These latter two are associated with the shallow soil of the highest points of the local mountains, whereas occur cerrado and forest in the deepest soils which is fertile, with abundant ground water (Eiten, 1982, apud Oliveira-Filho et al., 1994).
The cerrado (Brazilian savannah) is a type of vegetation varying in physiognomy, ranging from fields with a cover of sparse brush and low trees to forest formations, with trees of heights from 12 to 15 m (Fig. 1).The herbaceous stratum is mostly composed of grasses which are bushy and and dicotyledonous, but present neither rose-like plants, nor succulent or spiny ones.Only a few lianas and epiphytes are present (Rizzini, 1979).The cerrado occurs on reddish-yellow, dark red, and purple latosol which is strongly or moderately acid, with pH varying between 4.5-5.5 (Ribeiro & Walter, 1998).The families Fabaceae, Asteraceae, Myrtaceae, Melastomataceae, and Rubiaceae are the most common in this region (Batalha & Mantovani, 2000).
Gallery forests (Fig. 2) accompany small rivers, forming a closed corridor in watercourses above the water stream, and usually occur on valley bottoms or in drainage areas.They may also be present in transitions between initial formations of cerrados and fields.Concerning floristic composition, both types commonly belong to the following families: Myrtaceae, Leguminosae, Vochysiaceae, Rutaceae, Meliaceae, and Rubiaceae (van den Berg & Oliveira-Filho, 2000;Bertani et al., 2001).
The rocky fields (Fig. 3) are characterized by a continuous herbaceous stratum, made up mainly of Graminae, Eriocaulaceae, Xyridaceae, and Cyperaceae, as well as areas where some bushy forms also appear, specially representatives of the families Velloziaceae, Asteraceae, Melastomataceae, Malpighiaceae, Myrtaceae, Fagaceae, and Vochysiaceae (Giulietti et al., 1987).These occur in regions where the altitude may vary from 700 to 1000 m and the plants are subject to constant wind, hot daylight, and cool nights; they are usually found in latosol in condition of low water availability.What water is present is quickly drained into the surrounding rivers, due to shallow depth and reduced water-retention capability of local soil (Ribeiro & Walter, 1998).

Treatment of samples
The host plant samples were collected following the Fernandes et al. (1988) methodology, photographed, stored, and labeled in plastic bags.In the laboratory, morphological descriptions and specimen identification were made.Part of the material was immersed in plastic pots filled with water and closed with a net in order to obtain inductors, parasitoids, and inquilines.All material was conserved in 70% alcohol.Slide mounting of gall maker specimens for identification followed the Gagné (1994) technique.Samples were collected from March to September of 2000 in rocky field, cerrado, and gallery forest areas.
The vouchers of host plants were deposited in the Botanical Sector, and the gall and insect collection is located in the Laboratory of Invertebrates, both in the Biology Department, Faculdade de Filosofia Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Brazil.

RESULTS AND DISCUSSION
Results are presented in Table 1 which gives the morphological description of galls per host plant, gall makers, and parasitoids.Galls were observed in nineteen plant species, listed in Table 1 and shown in Figs. 4 to 24. Results are also presented in Appendix 1 which shows all the information about collection points and collected material.
In our collections, 79% of galls were found on leaves, 8% on stems, 8% on petioles, 4% on inflorescences, and 4% on bud leaf.The morphological types of galls found were globoid, conicle, discoidal, fusiform, shell-shape, and indefinite, with color varying from green to reddish-brown.Concerning the surface where galls were located on leaf, 64.58% of galls are found on the adaxial and 7.14% on the abaxial surfaces, with 28.58% on both sides.The majority of the sampled galls are hairy and the spherical gall of T. guianensis (Anacardiaceae) is glabrous on its adaxial surface and pubescent on its abaxial surface (Fig. 4).Fernandes et al. (1997) state that the hair and spine protect the inducer inside the gall against parasitoids, although all hairy galls found in Delfinópolis had an associated parasitoid.
The majority of plant species presented only one morphological type of gall.The exceptions were B. ungulata (Fabaceae) with a leaf (Fig. 13) and a stem gall (Fig. 14); C. pohliana (Rubiaceae) with one hairy gall in the leaf and another the in stem (Fig. 21); and Q. parviflora (Vochysiaceae) with two different types of galls on its leaves: one discoidal, occurring along the main leaf vein (Fig. 23), and the other fusiform with spines (Fig. 24).The occurrence of distinct morphological types of galls in the same plant species is rather common.For example, Fernandes et al. (1996) found 17 distinct kinds of galls in Baccharis dracunculifolia, and Gonçalves-Alvin & Fernandes ( 2001) described four types of galls in Byrsonima coccolobifolia (Malpighiaceae) and three on Eriotheca gracilipes (Bombacaceae).
Comparing the three vegetation physiognomies studied so far, the gallery forest and Brazilian cerrado showed more plant species with galls than did the rocky field.These results can be explained by fact that plant diversity is higher in the cerrado and gallery forest than in rocky fields.Most articles about the incidence of galls associate their occurrence with hygrothermic stress (Fernandes & Price, 1991).According to the latter authors, in hygrothermically stressed environments such as cerrado and rocky field, the appearance of galls tends to be much more common.Our results neither confirm nor corroborate this hypothesis because the collections were not made for purposes of comparison.
According to Rohfritsch & Shorthouse (1982), approximately 15,000 gall inductor insects are listed worldwide; they belong to the Thysanoptera, Lepidoptera, Coleoptera, Hymenoptera, Hemiptera (Sternorrhyncha), and Diptera Orders.Of these, the Diptera, especially the Cecidomyiidae family, is the most representative numerically.In Delfinópolis, we were able to confirm this fact, with Diptera inducing 59% of galls, 54% of which were of the Cecidomyiidae family; 9%, of the Sternorrhyncha (Hemiptera); and 27%, of unidentified inducers.The Cecidomyiidae are a large family of Diptera with around 15.000 described species.About 95% of this total belongs to the Cecidomyiinae subfamily, composed exclusively of gall makers.As in many natural environments in the neotropical region, almost all insects collected as gall inducers are new to science.In the three types of natural vegetation sampled in Delfinópolis, we collected 12 new species of Cecidomyiidae, two of which are also new genera (see Table 1).All new species and genera are described in other works, such as the description of Asphondylia canastrae, collected in ovaries of Leonotis nepetifolia (Lamiaceae) (Urso-Guimarães & Amorim, in press).Fernandes et al. (1988) related the presence of galls of Tomoplagia rudolphi (Tephritidae) in Vernonia polyanthes (Asteraceae), as well as a species of Psyllidae in Lonchocarpus guilleminianus (Fabaceae), also found in Delfinópolis.This fact shows that gall makers are very specific to a given ecological niche, and such specificity might be related to one genus or even to a single species.Most parasitoids found in Delfinópolis belong to the Chalcidoidea superfamily (Hymenoptera): Eulophinae (Eulophidae), Spalangiinae (Pteromalidae), Toryminae (Torymidae), and Rileynae (Eurytomidae).The others are from Helconinae and Microgastrinae (Braconidae).The Chalcidoidea includes the most common wasp parasitoids known and are largely found in galls of cecidomiids.As an inquiline, one new species of Meunieriella (Diptera: Cecidomyiidae) was obtained from Inga edulis galls.Meunieriella is an inquiline in ex-galls of other cecidomiids (Gagné, 1994).Other occasional inquilines obtained were a s pecies of Polyxenus (Diplopoda: Polyxenidae) and a species of Psocodea (Psocoptera) both in Smilax coriifolia (Smilacaceae).Some immatures of Aphididae and Lygaeidae (Hemiptera) were also found.The presence of new species in the sampled areas indicates the importance of this kind of study to inventory the diversity present in open environments.Taxonomic novelties can help in elucidating biodiversity patterns, so essential for identifying and conserving endemism and hotspot areas.