Diversity of insect galls from Mato Grosso State, Brazil: North Pantanal

The Pantanal Biome occupies 20% of the Brazilian territory extending its distribution over two Brazilian States, Mato Grosso and Mato Grosso do Sul. This Biome is one of Brazil’s poorly known regions concerning insect gall and their interactions with host plants. In this study, we characterized for the first time the gall morphology, identified host plants and the gall makers from an area of Brazilian wetlands from Mato Grosso State, known as Pantanal Matogrossense. We sampled Pantanal Biome areas in Poconé municipality, along the Transpantaneira Road, Mato Grosso State, Brazil, in two expeditions, July 2012 and January 2013, with a total effort of 2 hours. We characterized 91 morphotypes of insect galls in 54 host plant species; 28 gall makers in 24 host plant species; the richest host plant families are Fabaceae, Myrtaceae, and Sapindaceae. Psidium guineense Sw. is the super host species. This area in Pantanal Matogrossense is the second in the richness of gall morphotypes (N=91) and average morphotypes/plant species (1.7), comparing phytophysiognomies. Additionally, 15 plant species are new record as host in galler-host plant interaction in the world. This number represents 30% of the total of host plant species sampled in Poconé. This inventory is new knowledge to the Pantanal Matogrossense and representing a unique testimony of insect-plant interactions consumed by the unprecedented fire that occurred in Pantanal Biome in the dry season of 2020.


Introduction
The Pantanal biome occupies 20% of the Brazilian territory (Junk et al. 2013), extending its distribution over two Brazilian States, Mato Grosso and Mato Grosso do Sul. The Brazilian wetlands, called Pantanal popularly, are considered a hyper-seasonal savannah under contrasting stresses due to alternation between periods of drought and prolonged flooding (Eiten 1982, Marengo et al. 2021). Pantanal harbors deciduous or semi-deciduous forests shedding leaves during the dry season, deciduous forest and Cerrado vegetation in inselbergs and evergreen floodplain forests in the lower areas along rivers and channels (Nunes da Cunha et al. 2007). Its vegetation is highly influenced by Chaco Biome (Pott et al. 2011). It is considered a hotspot of biodiversity, with more than 2,000 species of vascular plants (Pott et al. 2011) and more than 2,000 species of animals, except terrestrial invertebrates (Junk et al. 2006), with the seasonal flood-pulsing harboring habitat specialization (e.g., morphological, anatomical and physiological adaptations) (Junk et al. 2013).
The interaction between plants and insects is still unexplored in North Pantanal, South-western of the State of Mato Grosso, in the Midwest region of Brazil. About 15% of the insect galls inventories made in Brazil were carried out in the Midwest region (Araújo et al. 2019). Despite that, only two have been carried out in the Pantanal biome (Julião et al. 2002, Urso-Guimarães et al. 2017. Both in the State of Mato Grosso do Sul, which is strongly influenced by the Cerrado biome. Julião et al. (2002) and Urso-Guimarães et al. (2017) found 182 morphotypes of galls in 104 host plants, of which only nine plant species and three morphotypes were common. The richest plant family in Abobral was Bignoniaceae, and the super host species was Hippocratea volubilis L. (Julião et al. 2002). In Corumbá/Porto Murtinho, Fabaceae was the richest plant family and Serjania sp. the super host species (Urso-Guimarães et al. 2017).
In this study, we present the first survey of gall-inducing insects for the North Pantanal, including the characterization of gall morphology and the identification of host plants. Our study represents the first step to understanding the richness of the history of host plants' interaction and gall-inducing insects in this biodiverse and unique biome.
In the last three months of 2020, the region of Pantanal Sul Matogrossense and Matogrossense (including Poconé) was devastated by an unprecedented fire. These months correspond to the Pantanal winter, in which the waters of the Paraguay River Basin should overflow the river channels and flood the plains around them. In this period, leaves fall, fruits, and branches accumulated in the litter, generating a formidable amount of food, all consumed by the primary consumers that occupy the food chain base and sustain the unique Pantanal biodiversity. But, in the winter of 2020, the flooding did not occur. All available dry matter functioned as fuel and burned large extensions of the Pantanal, destroying much this biome's rich fauna and flora due to deforestation, cleaning, and reforming pastures using improper management practice without control techniques endanger the conservation (Marengo et al. 2021). In this terrible scenario, our inventory represents a unique testimony of insect-plant interactions consumed by the fire.

Study site
We conducted this study in two areas: Pousada Rio Clarinho and Transpantaneira Road Km 40, in Poconé Municipality (16°36'03.5" S, 56°43'46.1" W), State of Mato Grosso, Brazil (Fig. 1). This region is localized in the North Pantanal, also called Pantanal Matogrossense (Fig. 1). Its vegetation is considered a Pantanal mosaic because it is influenced by distinct biomes, with the Amazonia to the North, the Cerrado to the East, the Meridional Forests to the South, and the Chaco to the West (Pott et al. 2011). The Cerrado vegetation occupies 36% of the study area region, corresponding to 10% in the sub-region of Poconé (South-western of the State of Mato Grosso) (Silva et al. 2000). The region's climate is the Tropical Climate of Savannah (Aw), with two well-defined seasons (hot and rainy in summer and dry and cold in winter). The seasonal flooding process is divided into four phases: flooding, flood, reflux, and dry (Costa et al. 2010).

Sampling
We performed two expeditions in a North Pantanal area in Poconé, State of Mato Grosso, Brazil, one in July 2012 and the other in January 2013. We selected two points to the collection, a floodable gallery forest along the Clarinho river (16° 36' 15.6" S/ 56° 43' 18.8" W), and a dry forest (Chaco edge) near the Transpantaneira Road (16° 35' 14.7" S/ 56° 44' 04.5" W), 3 kilometers apart from each other. We sampled along the trails' edges, with a 30-minute effort was made at each sampling point on each expedition, totaling 2 hours of effort following Price et al. (1998). We measured each route's length to quantify the sampled area (Urso-Guimarães et al. 2017), covering 52 meters in floodable gallery forest trail and 129 meters in the dry forest trail. All gall sighted was collected, without limitation of habitus, stem diameter, or plant height. The collection method, labeling, processing samples, identification of plants, and insects followed Urso-Guimarães et al. (2017) and Araújo et al. (2021). The voucher specimens were deposited in the Universidade Federal de São Carlos: plants in the Herbarium SORO, and the insect material in the Laboratório de Sistemática de Diptera.
In   From the insect galls, 28 (30.8%) of the gall inducers were obtained and identified in 24 host plant species. Among the insect inducers, 60.7% belong to Diptera (N=17) and 21.4% to Hymenoptera (N=7), 7.1% to Hemiptera, and Thysanoptera (N=2 each), and 3.6% to Coleoptera (N=1). Associated fauna and other details are in Table  3. The gall inducers of 63 morphotypes are undetermined because the galls were collected empty, the specimens obtained were damaged or the morphological information in the instars obtained was insufficient to the identification. As in all surveys, the species of Cecidomyiidae were the predominant gall inducer species (Table 3).

Discussion
The morphotype richness found in the gallery forests was significantly higher (N=83) when compared with the dry forest (N=8).
The leaves are the organ most attacked by the gall makers in all environments (Araújo et al. 2019), except for few studies with stems as the most affected organ always associated with dry environments (Veldtman & McGeoch 2003, Carneiro et al. 2009, Coelho et al. 2013, Toma & Mendonça 2013, Kuzmanich et al. 2018. Thus, the host plant species' leaves loss during the dry season must have influenced the low number of galls found in the dry forest. Fabaceae and Myrtaceae are two of the richest plant families in Pantanal (Pott et al. 2011). Pattern recovered in our study corroborating the hypothesis that families with the highest number of plant species also have the highest number of gall-forming species associated with them in all Brazilian biomes (Araújo et al. 2019, Santos-Silva & Araújo 2020). Sapindaceae appears as the third richest family, because of Serjania Mill. It is a super host genus, with eight gall morphotypes in only three species, the same situation found by Urso-Guimarães et al. (2017) in Corumbá. These results show the super host species' contribution to increasing the local richness of the insect-plant interactions, independently of plant species richness (Veldtman & McGeoch 2003).
Comparing with other studies in South Pantanal, our average (1.7) is similar to the other areas, Abobral region (1.7, Julião et al. 2002) Table 2). For the first time, P. guineense and C. laxum are reported as super hosts of gall morphotypes in the world. The predominance of galls in leaves and stems with the globoid and lenticular shapes, the green and brown colors and glabrous is a pattern also found in Pantanal Sul-matogrossense (Julião et al. 2002, Urso-Guimarães et al. 2017) and in other biomes (Araújo et al. 2019).
We found 91 morphotypes of galls in 54 host plants, of which 87 are new registers. Only four morphotypes are common to the studies of Julião et al. (2002) and Urso-Guimarães et al. (2017): the lenticular, brown, and glabrous on leaves of Bauhinia mollis, the fusiform in stems of Psidium guineense, the globoid, green, and glabrous on leaves of Magonia pubescens A.St.-Hil., and the globoid, green, and glabrous on leaves of Serjania caracasana. Thus, Brazilian Pantanal has 269 morphotypes of galls in 157 plant species, of which only two species are common of the three studies, Eugenia florida DC. and S. caracasana.The fifteen new records of host plants found in this inventory represent 30% of the total host plant species sampled in the Poconé survey (Table 2).
We also found that only three plant species, Coccoloba cujabensis, Symmeria paniculata, and Triplaris gardneriana, occur in Pantanal and Cerrado areas. These species occur exclusively in Mato Grosso and Mato Grosso do Sul States, which means the insect's interactions and these species are endemic. The low endemicity was expected because the plant species distributed in North Pantanal undergoes other biomes' influence in its composition (Pott et al. 2011).
The interactions among plants and associated entomofauna are still unknown and threatened with extinction due to deforestation. Mato Grosso State is currently one of the agricultural frontiers in Brazil. The maintenance and encouragement of taxonomic studies, such as the SISBIOTA -Diptera Brazil Program (2010-2015, are necessary to understand gall inducers' richness. Before studies funded by the SISBIOTA, only of gall inducers (Termitomastus leptoproctus Silvestri, 1901 and Schizomyia tuiuiu Urso-Guimarães & Amorim, 2002 -Diptera, Cecidomyiidae) were registered in Mato Grosso State. Three new species of cecidomyiids found in this survey are under the process of description, one species of each of the genera Bruggmanniella Tavares, Schizomyia Kieffer, and Youngomyia Felt.
This inventory became a unique testimony of insect-plant interactions in Pantanal Biome in Brazil that may have been completely devastated by fire in the dry season of 2020. We hope that with its enormous resilience, the Pantanal biome will recover the unique biodiversity lost by fire. We also expected that international organizations help Brazilian institutions to pressure the Federal Government to adopt measures for the conservation of Pantanal, a biome from South America, but is essential for humanity.