Occurrence and characterization of entomogenic galls in an area of Cerrado sensu stricto and Gallery forest of the state of Bahia , Brazil

We surveyed insect galls in an area of Cerrado sensu stricto and Gallery forest in the municipality of Caetité (BA) to contribute to current knowledge of the local flora and its associated gall-inducing insects. Monthly collections were made between February/2015 and January/2016, totaling 12 field campaigns (involving two or three people and lasting four hours) that followed an established path through the countryside. A total of 63 gall morphotypes were identified on 47 host plant species belonging to 22 families; 17 morphotypes were found in the Gallery forest and 46 in Cerrado vegetation. The plant families showing the greatest gall richness were Leguminosae (n=15), Myrtaceae (n=9), and Asteraceae (n=7). The species with the greatest number of galls was Mimosa gemmulata Barneby (Leguminosae) (n=3). Most galls were observed on leaves (66%) and stems (24%); they were mostly green (49.3%) or brown (26%), with globoid shapes (39.7%) or marginal roll (17.4%), and were unilocular (87%), glabrous (62%) and isolated (89%). Cecidomyiidae (Diptera) were the principal gall-inducing insects. The associated fauna was principally composed of Hymenoptera. Eight plant taxa were recorded for the first time as hosts of galling fauna.


INTRODUCTION
Many insect species associate with plants to increase their chances of survival.Those interactions between insect and their host plants can be mutualistic, benefiting both of the associated individuals, or they may benefit only one of the organisms involved -as is the case of parasitism (Price 1991).Insect parasites generally do not kill their host plant, although they may harm them by feeding on vital organs (Begon et al. 2007).
Gall-inducing insects are excellent examples of parasites that induce morphological and anatomical alterations in plant tissues or organs APARECIDA RAVENE F. DA SILVA et al. through processes of hyperplasia and hypertrophy (Mani 1964).These processes are stimulated by mechanical or chemical factors originated from the insects (Hori 1992), and can interfere with the flux of the photosynthates and nutrients produced by those plants (Schoonhoven et al. 2005).
Galls, also known as cecidia, provide protection for the immature stages of the inducing insects against abiotic environmental factors such as sunlight excess and water stress as well against natural enemies (Stone and Schönrogge 2003).Galls can occur on essentially all plant organs, from the extremities of their roots to their apical buds, and both on vegetative and reproductive parts -although they are more numerous and diversified on the aerial portions of the plants, especially on leaves (Mani 1964, Maia 2013).
Studies on galls have increased expressively in recent years in Brazil.Most of them regards inventories of gall diversity in different ecosystems (e.g., Araújo et al. 2012, Costa et al. 2014a, b, Nogueira et al. 2016), while others have investigated ecological aspects of gall-inducing insects or described new species (e.g., Maia and Souza 2007, Maia et al. 2010, Maia 2014), as well as the structural and ultrastructural natures of gall tissues (e.g., Arduin and Kraus 2001, Moura et al. 2009, Oliveira and Isaias 2010, Isaias et al. 2011, Suzuki et al. 2015).Additional studies have focused on the importance of galls as bioindicators (Moreira et al. 2007, Oliveira 2009).
In spite of recent progress, the knowledge on the diversity and distribution of galls in Bahia State is still relatively limited.Most sampling efforts have been concentrated in the southwestern region of the state, with studies in the Gallery forests (Costa 2016), Cerrado (Costa 2016, Nogueira et al. 2016), Caatinga (Santos et al. 2011, Carvalho-Fernandes et al. 2012, Costa 2016), and Caatinga-Cerrado transition zones (Costa et al. 2014a, b, Nogueira et al. 2016) This situation is worrisome as the biodiversity of Bahia is increasingly threatened by deforestation for pasture formation, agriculture, civil construction, and the illegal extraction of wood products (Ministério do Meio Ambiente 2002).The conversion of natural environments into urban and agricultural areas leads to the loss and fragmentation of habitats and consequent biodiversity reductions and disruptions of plantinsect interactions (Tabarelli 1998).Previous studies have demonstrated that the richness of entomogenous galls in the interior of forest fragments responds negatively to anthropogenic disturbances, diminishing sharply as biodiversity losses and increasing plant mortality rates impoverish those fragments (Urso-Guimarães et al. 2003, Moreira et al. 2007).
Within that context, we undertook a survey of insect galls and their host plants in an area -DCH/Campus VI to allow eclosion of the inducing insects.The remaining galls were examined under a stereomicroscope and any immature forms of the insects were removed for identification and the numbers of chambers in the galls were counted.Any immature or adult insects were stored in 70% ethanol.The identifications of immature forms (without corresponding adult insects) were made by comparisons with insect morphotypes and host plants previously identified in Cerrado vegetation and in Gallery forests.All the examined material was deposited in the Entomological Collection of the Museu Nacional (MNRJ /UFRJ).

RESULTS
We recorded 63 gall morphotypes on 47 host plant species belonging to 22 families in the vegetation along the Jacaraci trail (Table I).Of the total number of galls (63), 17 were observed in the Gallery forest (on 14 plant species of 9 families) and 46 in Cerrado vegetation (on 33 plant species of 16 families).The plant families with the greatest gall richness were Leguminosae (Fabaceae) (n=15), Myrtaceae (n=9), and Asteraceae (n=7).The Leguminosae had the largest number of host species (nine), followed by Myrtaceae and Malpighiaceae (seven and five species, respectively).Bauhinia L. (Leguminosae-Cercidoideae), Mimosa L. (Leguminosae-Caesalpinioideae), Guarea F.Allam.ex L. (Meliaceae), and Eugenia L. (Myrtaceae) were the genera that hosted the greatest number of galls (6, 3, 3, and 3, respectively).The species showing the greatest gall richness was Mimosa gemmulata Barneby, with three associated morphotypes.
Most of the gall morphotypes were encountered on a single plant organ (81%) of a single host plant; five plant species had galls on both their leaves and stems (11%) (Bauhinia sp., Bauhinia acaruana Moric., Celtis iguanaea (Jacq.)Sarg., Mimosa gemmulata, and Moraceae Indet); two species have galls on their buds and stems (6%) of Cerrado and Gallery forest vegetation in the municipality of Caetité, Bahia State, Brazil.

MATERIALS AND METHODS
Current study was undertaken along the Jacaraci trail (14°05'18"S, 42°29'56"W, at 1,110 meters a.s.l.) located along the urban border of the municipality of Caetité (BA).The trail is approximately 3 kilometers long and passes through areas of Cerrado sensu stricto vegetation growing on sandy soils with exposed rock outcrops, as well as a Gallery forest along the Riacho Alegre Creek.
Collections were undertaken on a monthly basis between February/2015 and January/2016, totalling 12 field campaigns along the entire extension of the trail.All plant architectures (herbs, shrubs, trees, and vines) visible up to 3 m above the ground were searched for galls involving two or three people and lasting approximately 4 hours each.When encountered, the galls were photographed and classified into morphotypes following Isaias et al. (2013).
Plant voucher specimens were collected in the field and subsequently prepared for herbarium storage at the Laboratório de Botânica of the Departamento de Ciências Humanas, Campus VI at the Universidade do Estado da Bahia.The plants were identified using analytical keys from the specialized literature, as well as by comparisons with herbarium specimens previously identified by specialists and held in the herbaria of the Universidade do Estado da Bahia (HUNEB/Caetité Collection) and Universidade Estadual de Feira de Santana (HUEFS).One voucher of each species was deposited in the HUNEB/Caetité Collection herbarium.The taxon list is organized alphabetically according to family, genus, and species, following the APG IV classification system (2016).

DISCUSSION
Leguminosae, Myrtaceae, and Asteraceae served as hosts for the largest variety of gall morphotypes along the Jacaraci trail; they are also among the principal families bearing galls in different Brazilian ecosystems, especially the Cerrado (Gonçalves-Alvim and Fernandes 2001, Urso-Guimarães and Scareli- Santos 2006, Araújo et al. 2012) (Table II).
The Leguminosae hosted the greatest diversity of gall morphotypes in Cerrado areas (Gonçalves-Alvim and Fernandes 2001, Araújo et al. 2011, Luz et al. 2012).This gall richness may reflect the high number of species of Leguminosae in that vegetation type (approximately 879), but also the high numbers of their species associated with gallinducing insects (Mendonça 2007).Asteraceae is the second largest family in terms of the number of species in that biome (Mendonça et al. 2008), with approximately 1,251 species belonging to 190 genera (Asteraceae in Lista de Espécie da Flora do Brasil 2020 em construção).These families are also representative with the greatest richness of galls in Gallery forest (Urso- Guimarães et al. 2003, Bergamini et al. 2017).
Mimosa gemmulata had the largest number of galls.Studies undertaken by Costa (2016) in the Parque Estadual Serra dos Montes Altos, Bahia, showed that same species as a super-host, with five     and six distinct gall morphotypes in Cerrado and Gallery forest sites, respectively.Galls were previously surveyed in the municipality of Caetité in areas of Cerrado and in Caatinga-Cerrado transition zones in the Serra Geral Mountains (Costa et al. 2014a, b, Nogueira et al. 2016).The current study, however, represents the first inventory undertaken in an area of Gallery forest in that municipality.The inventory undertaken by Costa (2014b)   The galls recorded had been induced on leaves, stems, buds, and fruits, with leaves being the organs most affected, whether in the Cerrado or Gallery forest; no galls were observed on flowers.These results are similar to other studies undertaken in different vegetation types in Brazil, where galls have been observed predominately on leaves (Julião et al. 2005, Maia et al. 2008, Nogueira et al. 2016, Santos et al. 2010, Araújo et al. 2012), a fact that is probably related to the nutrient reserves present in these organs (Mani 1964).
Most of the galls were isolated and contained only a single larval chamber, a result similar to those of Costa et al. (2014a, b) and Gonçalves-Alvim and Fernandes (2001).Only 37% had some pilosity, with being the other glabrous (63%).The presence of trichomes on the galls may help defend against natural enemies, reduce water losses, and help maintain mild internal temperatures (Moura et al. 2009).
In terms of their shapes, most galls were globoid, marginal roll or lenticular in both of the environments surveyed.Globoid galls have been the predominant morphotype described in all of the inventories undertaken in the Neotropical region (Isaias et al. 2013).Similar results were found in Restinga areas in Rio de Janeiro State (Maia 2013), Caatinga-Cerrado sites in Bahia (Costa et al. 2014b) and Gallery forest in Minas Gerais (Urso- Guimarães et al. 2003).
The identification of 48 gall-inducing insects were quite difficult due to the small number of samples (with most galls showing incomplete development of the gall-inducing insects) -and they remained undetermined.The gall-inducing insects that could be identified belonged to the orders Diptera, Lepidoptera, and Thysanoptera; most were Diptera (Cecidomyiidae) (53% of the total).Cecidomyiidae constitute the largest family of that order, comprising 6,590 species belonging to 812 globally distributed genera (Gagné and Jaschhof 2017).The galls of the Lepidoptera are usually encountered on the stems and buds (Maia 2006), but we recorded their induction on the leaves of Bauhinia pulchella Benth.and Bauhinia sp. and on the buds of Plinia peruviana they were also recorded as associated fauna in cecidomyiid galls on Qualea parviflora Mart.
We recorded two gall morphotypes induced by Thysanoptera in an unidentified species of Malpighiaceae and on Eugenia sp.(Myrtaceae), both on their leaves.These results confirm the plant preferences of those organisms for inducing leaf galls (Maia 2006).
In addition to the gall-inducing insects, there is also a distinct insect fauna associated with the galls themselves.Those arthropods vary in terms of their feeding habits and can be classified as: parasitoids, predators, inquilines, and successors (Maia 2001).The microfauna associated with the galls in the present study was composed of Hymenoptera, Hemiptera, Lepidoptera, Thysanoptera, Coleoptera, Collembola, Araneae, and Pseudoscorpionida.The order Hymenoptera had the greatest number of records, occurring on galls observed on Asteraceae Indet., Moquiniastrum sp., Combretum leprosum Mart., Caliandra macrocalyx Harms, Myrtaceae Indet., Solanaceae Indet., and Turneraceae Indet.This order stands out for its parasitoids, as reported in various studies, being considered the principal taxon responsible for the deaths of gall-inducing insects.Species of Hymenoptera have been reported as parasitoids in areas of Cerrado (Maia andFernandes 2004, Maia et al. 2008) and Gallery forest (Costa 2016), corroborating the current results.
Inquilines are organisms that simultaneously inhabit the galls and feed on the plant tissues within it -thus competing with the gall-inducing insects (Naredran et al. 2007).The inquilines encountered in the present study belonged to the Hemiptera, Lepidoptera, Thysanoptera, and Coleoptera.These same orders have also been recorded in Cerrado (Maia and Fernandes 2004) and Gallery forest sites (Costa 2016).
The fauna of successors was composed of ants, spiders, pseudoscorpions, arachnids, and Collembola -representing organisms that occupy the galls after they have been abandoned by the inducing-species.While pseudoscorpions have only infrequently been reported in galls (Maia 2001, 2011, Carvalho-Fernandes et al. 2012, Maia and Souza 2013, Costa et al. 2014a, Nogueira et  Even though the study area was not extensive (a trail approximately 3 Km long), a considerable diversity of galls was observed.Of the 47 host plant taxa identified, eight were identified for the first time as gall hosts for Brazil.These results reinforce the importance of undertaking inventories of galls and their host plants in unsampled areas throughout that country, since it will contribute to the knowledge about plant species, galling insects and their interactions among different environments.

TABLE I (
continuation) APARECIDA RAVENE F. DA SILVA et al.

TABLE II Richness of gall morphotypes in host plants of Cerrado sensu stricto and Gallery forest in Brazil.
recorded 35 gall