Cecidomyiidae (Diptera, Insecta): richness of species and distribution in Brazil

Most Neotropical species of Cecidomyiidae (Diptera) have been described from Brazil, but a list of species with occurrence in the country has never been published. Little is known about their distribution and richness in the Brazilian phytogeographic domains. Additionally, a list of host plant species has never been gathered. The present study aims to fill these knowledge gaps and provides an overview of this family in Brazil. For this, data were obtained mainly from the literature, but also from the Cecidomyiidae collection of Museu Nacional and two herbaria (RB and R). Based on the site “Flora do Brasil 2020”, botanical names were updated and plant species origin and distribution were verified. A total of 265 gall midge species have been recorded in Brazil, most from the Atlantic Forest (183), followed by Cerrado (60), and Amazon Forest (29). The other phytogeographic domains shelter from five to ten species. Phytophagous gall midges occur on 128 plant species of 52 families, almost all native, being 43 endemic to Brazil (21 endemic to Atlantic Forest, five to Cerrado, and one to Amazon). Although, the taxonomical knowledge is focused on the Atlantic Forest, each domain has its own fauna composition and these informations can be useful for environmental conservational purposes. About 58% of the Brazilian fauna are known only from the type-locality. In order to fill these gaps, it is necessary and important to collect in uninvestigated areas.


Introduction
Cecidomyiidae are one of the most speciose families of Diptera, with more than 6,500 species. They are cosmopolitan and known mainly as gall-inducers (Gagné & Jaschoff 2017). Most species have been described from the Holarctic Region, while the Neotropical fauna comprises less than 10% of the known species. This low richness reflects the scarcity of taxonomic studies in this region. Most species have been described from Brazil. Nevertheless, a list of Brazilian species has never been published.
Brazil comprises six phytogeographic domains: Amazon Forest, Atlantic Forest, Caatinga, Cerrado, Pampa, and Pantanal, which greatly differ from each other in flora composition, and consequently they shelter different assemblages of gall-inducing species. The richness of cecidomyiid species by domain is still unknown, as well as the number of gall-inducing, predaceous, inquilinous, fungivorous, and freeliving phytophagous species. Most of them appear to have a restricted distribution, but there are several locality records scattered in the literature.
Additionally, a list of host plant species has never been elaborated and many botanical names need to be updated. The main goals of the this study are: 1) to present a general overview of the richness of this family in Brazil,2) to provide for the first time a list of gall midges species with occurrence in Brazil as well as in each phytogeographic domain, 3) to fill a knowledge gap about the distribution of this group, and 4) to provide for the first time a list of host plant species in Brazil.

Materials and Methods
The last version of the world catalog of Cecidomyiidae written by Gagné & Jaschhof 2017 was used as starting point. Using the find tool, all species with records in Brazil were retrieved. Papers with the original description of each species were consulted to obtain more detailed data on its occurrence localities. Furthermore, a literature survey was performed on the database "Web of Science" using "Cecidomyiidae" and "Brazil/Brasil" as key words in order to verify the gall midge species described after 2017. Based on the site "Flora do Brasil 2020", botanical names were updated and plant species origin and distribution were verified. Synonyms were provided in brackets after the correct names to allow linking of retrieved data to the original publications. Additionally, all insect gall inventories of Brazil were also consulted to recover information about locality records of the gall midge species, based on host plant species and gall morphology, whenever possible, or on gall-inducer identification. Data on phytogeographic domains were obtained using maps of IBGE 2004 or directly from the literature. In some cases, domains were not determined because data on localities were insufficient. When gall midge species were recorded in localities occupied by two different domains, both were considered as part of their distributional area.
Besides, the Collection of Cecidomyiidae (Diptera) of Museu Nacional, Universidade Federal do Rio de Janeiro (MNRJ) was examined to aggregate unpublished data of species occurrence. Simultaneously, the Jardim Botânico do Rio de Janeiro herbarium (RB) and the Museu Nacional herbarium (R) were consulted in a search of galled exsiccates. This procedure was adopted since galls are extended phenotypes of the gall-inducing insects (Stone & Schönrogge 2003), so their presence on the host plants indicates the gall-inducing species' presence. Data on localities were retrieved from labels and new records were established by comparison with the literature. The geographic distribution of all gall-inducing species was updated. Data on Brazilian localities were detailed, including states and municipalities. To discriminating Rio de Janeiro and São Paulo states from Rio de Janeiro and São Paulo municipalities, the word "state" was used whenever necessary.
Most gall-inducing species are monophagous (about 90%), but oligophagous and polyphagous species have been reported. Oligophagous species are represented by at least 15 gall midge species, 11 of them occur on two or three plant species of the same genus and four on two or three genera of the same family. The number of hosts of some gall midge species could not be determined, since the level of plant identification does not allow it. This is the case of five gall midge species, four of them have been associated with an identified plant species plus a non identified congeneric host, and the other with an identified species plus a morphospecies of the same plant family. A single cecidomyiid species is polyphagous, occurring in plants of different families.
Fabaceae, Asteraceae, and Myrtaceae are the plant families with the greatest richness of gall midge species (28, 26 and 25), followed by Nyctaginaceae (16). They together host about 36% of the Brazilian fauna richness. Among these families, Myrtaceae exhibit the highest average of gall midge species by host plant species, 1.8, while Fabaceae have a similar value to Asteraceae (1.2 and 1.3, respectively). The average number in Nyctaginaceae was not stablished, because most plants were not identified in species (Table 2). All other families shelter from nine to one gall midge species, but most of them (23) (about 44%) shelter a single gall-inducer. The average of gall midge species by host plant species was 1.0 in 33 families. This is the most frequent value (  Rübsaamen, 1909, Asphondylia Loew, 1850, and Clinodiplosis Kieffer 1895 are the most speciose, with 25, 23 and 20 species, respectively (Table 3). Predators are represented by four genera, Aphidoletes Kieffer, 1904, Diadiplosis Felt 1911, Feltiella Rübsaamen, 1910, and Lestodiplosis Kieffer, 1894, being Diadiplosis the most speciose, with ten species, while the others comprise three (Lestodiplosis) or one species (Aphidoletes and Feltiella). The first genus feeds on aphids, the second on scale insects (Coccoidea), the third on mites and the fourth mostly on other cecidomyiids, but also on mites. They have been used as biological control agents of some plant pests. Fungivorous species are represented by five genera, Dichodiplosis Rübsaamen, 1910, Haplusia Karsch, 1877, Mycodiplosis Rübsaamen, 1895, Stomatosema Kieffer, 1904, and Termitomastus Silvestri, 1901 Three of them comprise a single species, while Haplusia comprises two and Stomatosema six. Inquilines are represented by six genera, Clinodiplosis Kieffer, 1894, Contarinia Rondani, 1860, Dialeria Tavares 1918, Meunieriella Kieffer, 1909, Neolasioptera Felt, 1908and Trotteria Kieffer, 1902. Among them, Dialeria and Trotteria include exclusively inquilinous species. Five of them comprise a single inquilinous species in Brazil, while Meunieriella comprises four. All were recorded in galls of other Cecidomyiidae. Although these cecidomyiids have been reported as inquilines, they are probably kleptoparasites, according to Luz and Mendonça-Júnior (2019). Free-living species are less common, being represented by three genera, Clinodiplosis, Lopesia, and Prodiplosis Felt, 1908, each with a single species. Their larvae feed on plant reproductive organs. And only one species, Didactylomyia longimana (Felt, 1908), is reported as the kleptoparasite in literature.
Most species of gall midges (about 90%) have been recorded exclusively in Brazil, while only 26 (about 10%) occur in other countries. The Atlantic Forest is the phytogeographic domain with the greatest richness of species, 183, followed by Cerrado (60 species), Amazon (29 species), Pampa (10 species), Caatinga (8 species), and Pantanal (5 species) ( Table 3). These values correspond to about 69%, 23%, 11%, 4%, 3%, and 2% of the Brazilian fauna of Cecidomyiidae. Fourty-one cecidomyiid species are associated with 43 endemic Brazilian plant species. Among them, 21 hosts are endemic to Atlantic Forest, five to Cerrado, and one to Amazon. No hosts were endemic to Caatinga, Pampa and Pantanal (Table 4). Two-hundred thirty five gall midge species (235) are known from a single domain: 157 from Atlantic Forest, 35 from Cerrado, 17 from Amazon Forest, 8 from Pampa, 4 from Caatinga, and 3 from Pantanal. The others have been reported in two (23 species) or three domains (seven species). Onehundred and thirty-seven species (about 52% of the Brazilian fauna) are known only from the type-locality.
A list of gall midge species with occurrence in Brazil is presented below in alphabetical order. Data on their food habit, geographic distribution and host plant are added. Botanical names were updated (synomyms found in publications are given in brackets). The origin of each host plant and its occurrence in Brazilian phytogeographic domains are also provided. These last two informations are restricted to hosts identified at specific level. References are added in chronological order.     Table 5. Richness of gall midge species (Diptera, Cecidomyiidae) by vegetable family in Brazilian phytogeographic domains.

Family Number of gall midge species Amazon Forest
Atlantic Sixteen gall-inducing species are oligophagous, while the others are monophagous. Phytophagous species have been recorded on 38 plant families, 73 genera and 82 determined species. Myrtaceae, Asteraceae, Nyctaginaceae, and Fabaceae are the superhost families, which together shelter 69 of the gall midge species (22, 19, 14, and 14, respectively). This value corresponds to about 39% of the gall-inducing species richness (Table 5). Thirty-eight gall midge species, when described, were recorded on 21 host plants identified only in genus. Later, two of them, Asphondylia stachytarpheta Barnes, 1932 and Machaeriobia machaerii (Kieffer, 1913) were obtained from identified plant species.
Eleven gall midge species have been recorded on five host plants identified only in family (Asteraceae: 2, Fabaceae: 3, Malvaceae: 1, Myrtaceae: 2, and Rubiaceae: 3). Fourty-eight gall midge species induce galls on endemic plants to Brazil,36 of them on endemic plants to the Atlantic Forest ( Table 4). The remainders are associated with native plants, except Schismatodiplosis lantanae, Asphondylia sennae, and Clinodiplosis melissae, inducers of galls on Lantana camara (a naturalized plant), Senna bicapsularis and Melissa officinalis, both exotic.

PAMPA
Only ten species of gall midges of nine genera have been recorded in the Pampa (List 5), nine of them are gall-inducers and one was caught in flight. One species is oligophagous, Asphondylia moehni, the other inducers are monophagous. They are associated with eight plant families distributed in eigth genera and six determined species. All families shelter a single gall midge species, and there are two doubtful records on Smilacaceae (Table 4). Three gall midge species occur on host plants identified only in genus, totaling three plant genera. All host plants are with 8, 515, 767. 049 km 2 of extension (IBGE, 2012), has a peculiar and diverse flora, with 46, 4922 species (Flora do Brasil, 2020), and also its Cecidomyiidae fauna is the most taxonomically studied. These facts together explained this high percentage. Most species induce galls, since this is the predominant habit in this family   salicifolia, and E. strigosus are also exotic, but those associated with M. officinalis and S. bicapsularis were described from Brazil and they have never been reported in other countries, suggesting that these hosts were colonized by Brazilian gall midges.
Lantana camara is naturalized and its gall-inducing species was described from Brazil, but it occurs in several Latin American countries. Probably the midge was introduced together with its host.
Incongruities between the host plant and gall-inducing species distributions were observed, suggesting a plant misidentification. In this case, plant vouchers should be examined, but unfortunately the number of vouchers are rare in the literature.
Twenty-seven botanical names were uptaded, but synonyms were cited in brackets to allow their association with the original references. This procedure is important to gather data on the same species, even if under different names.
Most gall-inducing species are monophagous (about 90%), what was expected, as most gall-inducing insects exhibit a high degree of Biota Neotrop., 21 (2) The best represented gall midge genera are Lopesia, Asphondylia, and Clinodiplosis. The first is predominantly Neotropical while the others are cosmopolitan, but well represented in the Neotropics (Gagné & Jaschhof 2017). Species of Clinodiplosis, Contarinia, Dialeria, Meunieriella, Neolasioptera and Trotteria have been reported as inquilinous species in galls. But in fact, according to the ecological concept, they should be considered kleptoparasites, since they do not promote the production of new tissues, as inquilines do (Luz & Mendonça-Júnior 2019).
Several gall midge species are associated with endemic hosts. This information is very important, because it shows the peculiarities of the Brazilian fauna, revealing species with exclusive occurrence in the country. The high number of species known only from the type-locality indicates how the geographic distribution of Brazilian fauna is still poor. This scarcity of data is reinforced by the high number of species which have never been collected again since their description.
Concerning phytogeographic domains, Atlantic Forest shelters the highest richness of gall midge species, followed by Cerrado, Amazon Forest, Pampa, Caatinga, and Pampa. Amazon Forest and Cerrado are the largest, with an area of 2,196,943 and 2,036, 448 Km 2 , respectively, followed by Atlantic Forest with 1,110,182 Km 2 and Caatinga with 844.453 Km 2 . The two others are the smallest, Pampa with 176,469 and Pantanal with 150,355 Km 2 . They also differ in richness of flora. Amazon Forest shelters about 50,000 plant species of Angiospermae, Atlantic Forest 20,000, Cerrado 11,600,Caatinga 3,500,Pampa 3,000 and Pantanal only 900 (MMA, 2020). Considering these data, we should expect the highest richness of gall midge species in the Amazon Forest, according to the plant richness hypothesis (Southwood 1960(Southwood , 1961, since this domain offers quantitatively and qualitatively the greatest amount of resources for the gall-inducers. Nevertheless, the highest richness is reported in the Atlantic Forest, the most investigated domain. This result is an effect of the strong sampling efforts in Atlantic Forest areas, the poor knowledge of the Cecidomyiidae fauna of other Brazilian biomes and the lack of taxonomists in our country.
Most gall midge species occur in a single domain, differing from their host plants which can be found in more than one domain. This suggests that the distribution of gall-inducing species can be wider than that which we known today. Arriola et al. 2016 argued that the distribution of the galling-insects is similar to that of the host plant. So, collections in uninvestigated ou poorly investigated localities are necessary to fill these geographic distribution gaps.
Nevertheless, several gall midge species are associated with plants endemic of a specific phytogeographic domain, as Amazon Forest, Atlantic Forest, and Cerrado. These data reveal the peculiarities of each one and can be useful for the establishement of environmental preservation areas.

Conclusion
This study is the first dataset of gall midge species with occurrence in Brazil. It totalize 265 species (43% of the Neotropical fauna); 85.6% are gall-inducers. Phytophagous gall midges are associated with at least 128 host plant species. Fabaceae, Asteraceae and Myrtaceae shelter the greatest richness of gall-inducing species. Lopesia, Asphondylia and Clinodiplosis are the best represented cecidomyiid genera. Most species (about 90%) are known only from Brazil. The Atlantic Forest as the most investigated domain comprises the highest species richness. Several gall midge species induce galls on plants endemic to Brazil. Each Brazilian phytogeographic domain has its own species composition. There is a high number of cecidomyiid species which are known only from the type-locality. Data indicate that the Brazilian fauna is the most studied in the Neotropical Region, confirm the greatest richness of gall midges on plant families which are well represented in Brazil, reveal the most diverse genera in the country, show the peculiarities of each domain and highlight how the geographic distribution of most species is still poor.