Plant Exchange Networks and their Importance in Mbyá-Guarani Medicine in Southern Brazil

Background: Experts in the Atlantic Forest, the Guarani people have the habit of transporting and exchanging plants due to their mobility throughout the territory. Historically, this habit contributed to the species composition and diversication among different phytophysiognomies that comprise the Atlantic Forest. Medicine and spirituality are traits that stand out within the Guarani culture, which is based on a holistic understanding of physical and spiritual well-being for the person’s health. To achieve this balance, they use a range of native and adapted plant species. Our goal is to understand some of the Guarani contributions to the cultural landscape in the Atlantic Forest. We also investigate whether kinship relations can facilite plant exchanges used in medicinal or mystical contexts between Guarani people. Methods: We conducted semi-structured interviews with key persons asking about the importance of forest environments for Guarani health and about visits to other Guarani villages and plants exchanged. Results: We visited seven Guarani Indigenous Territories in south Brazil, and with the participation of 12 respondents, we registered 27 species that were exchanged through different phytophysiognomies in the Atlantic Forest. These results show an intense movement of plants currently occurring between villages and the importance of these movements for both individual health and the integrity of the environments in which the Guarani villages are inserted. Conclusions: We observed a search for the recomposition of traditional species in the Guarani medical system, and we highlight the fundamental role of Guarani management in the conservation of the southern Atlantic Forest in indigenous territories.

ecological knowledge related to characteristics such as age, gender, kinship, education, place of residence, level of acculturation, social position and level of integration in the economic market. For example, in two Tsimane villages in the Bolivian Amazon, Díaz-Reviriego et al. (34) found high rates of diversity in exchange networks of home-grown crops, in uenced by women and kinship ties. Similarly, Lope-Alzina (37) observed that among members of a Yucatec-Maya community in Mexico, home gardens are the main source of exchanged plants. Despite strong market share, gifts remain the predominant form of exchange, with most gifts coming from home gardens and with most exchanges taking place among women in kinship networks (37). Routes of knowledge transmission about medicinal plants among the Yucatec-Maya in Mexico showed that the individual knowledge of medicinal plants is positively associated with the position in the network of exchanges of knowledge about herbal medicines (36). In Africa, Europe, Latin America and Oceania, Coomes et al. (38) showed that farmers with leading social positions and strong ethnobotanical knowledge were expected to be the main seed suppliers in seed networks.
The aim of this study was to investigate the current exchanges of plants between Guarani villages, contributing to the formation of cultural landscapes (13,18,29,31), which may have occurred since pre-Columbian times (30). Our main hypothesis is that villages with stronger family ties exchange more propagules than others. The speci c objectives were (1) to describe the exchange networks of plant propagules of medicinal and mystical or religious importance between Guarani villages in southern Brazil and (2) to discuss the importance of plants and environments for eco-cultural Guarani health. We focus on seeking plants used and interchanged for medicinal or mystical/religious purposes (as medicine and spirituality are intertwined in Guarani worldview) and chose to use the term mystical/religious to refer to plants used in the treatment of illnesses of the spirit or in magical contexts, such as spells and magic (ka'avo), according to the traditional healing practices, also supported by Guarani bibliography (27).

Study area
Seven Mbyá Guarani Indigenous Lands in the Atlantic Forest of southern Brazil were included in this research. They were chosen by convenience due to pre-existing contacts of the rst author and the indication of propagule exchanges among them. The Atlantic Forest is a hotspot for biodiversity conservation (39), and the Guarani villages included in this study are in different phytophysiognomies (sensu of Instituto Brasileiro de Geogra a e Estatística (IBGE) (40)): Dense Ombrophylous Forest, Seasonal Semideciduous Forest, and one village is located in an ecotone (transition zone) between the Dense Ombrophylous Forest and the Mixed Ombrophylous Forest.
The Indigenous Lands and their Tekoá (villages) are: 1) Nhuu Porã (also known as Campo Molhado, with 2268 ha, created in 2001) is located in the municipalities of Riozinho, Maquiné, and Caraá (Rio Grande do Sul state). Altitude ranges from 850 to 900 m, and the village is in an ecotone area between Dense Ombrophylous Forest and Mixed Ombrophylous Forest in medium to advanced stages of regeneration due to the former logging exploration. The village is approximately 30 km from the urban environment, and the population is 25-30 people, distributed in ve to six families. 2) Ka'aguy Porã (Retomada Indigenous Land, with 367 ha) is a territory occupied in 2017 located in the municipality of Maquiné (for details of this process, see Printes and Benites (24)). The region is of Dense Ombrophylous Forest, and the population is approximately 12 families (3). Yvy Poty (Flor da Terra Indigenous Land, acquired in 2014, with 100 ha) is located in the municipality of Barra do Ribeiro, near the city of Porto Alegre, and is within an area of Seasonal Semideciduous Forest. There are approximately 40

Data collection
Data were collected between October 2017 and November 2018. The maximum length of stay in one village was one week, but in two villages, the visit was only one day; however, the arrangements to visit each village took longer times. The length of stay in each village depended on the availability of the people to be interviewed. All interviews and moments of participant observation were preceded by obtaining prior consent from village leaders through agreement with a Prior Informed Consent Form, in compliance with the ethical precepts of ethnobiological research of the International Society for Ethnobiology Code of Ethics (42). The research was registered in the Ethics Committee of Universidade Federal de Santa Catarina -UFSC (73329517.0.0000.0121), the application for authorization to enter Indigenous Land was registered in the National Indian Foundation (FUNAI) (08620.000440/2018-17), and the register for associated traditional knowledge access in the National System for the Management of Genetic Heritage and Associated Traditional Knowledge (SISGEN) is under number A315C86. The authorization for collection of botanical material is registered by the number 6120635 in the Brazilian Biodiversity Authorization and Information System (SISBIO).
Data were collected through participant observation (43), semi-structured interviews (44) with key participants from each indigenous land, botanical collection and identi cation of the plants mentioned in the interviews. We used a non-probabilistic sampling for the interviews, including adults (over 18 years) who were the most involved with medicinal and mystical or religious use of plants, teachers, political or spiritual leaders, and those who usually participate in plant exchanges. We also respected social status within the villages, and we interviewed a maximum of ve people in each village, also considering the optimization of time and resources available for the study (45). The semi-structured interviews had two parts: the rst referred to the cultural and social characteristics that encourage or do not encourage the exchange of plants and to the person's perception of the environment, including the use of plants in traditional ceremonies, if she/he often visits other villages, if he/she was kinship related to people from the visited villages, and how important the forest environments are (full interview protocols are available upon request). The second part of the interview addressed the plants used for medicinal, mystical or religious purposes, whether they are native or exotic in the village, as well as which plants were exchanged and with which villages these exchanges occurred.
Plant collection was conducted according to Ming (46), and we had the support of botanical experts for the identi cation of vegetative material. Fertile vouchers were deposited in the UFSC FLOR Herbarium under numbers 66299 to 66319 and 67486 to 67487. For plants whose collection was not possible, we made photographic records to check the possible botanical identi cation.

Data organization and analysis
Data were analyzed qualitatively and by calculating percentages of responses. Parts of the responses of the interviewees were transcribed, and those speeches inserted in the results were identi ed by the interviewee number, followed by the name of the Tekoá and Indigenous Land. Due to the different number of interviewees per village, the analysis of plant exchanges considered each village as a sampling unit. The exchanges made between the villages were analyzed through a bipartite network, in which we relate the visited villages with the villages that were mentioned in the plant exchanges. We used the package bipartite of the R platform Rx64 3.4.1 (47). We analyzed the origins and destinations of the interchanged plants to observe the movements between phytophysiognomies and the Guarani contributions to the ecological con gurations of the vegetation and the selection of species.
We analyzed the in uence of kinship on plant exchanges through four pre-established kinship categories: (1) absent (no kinship with anyone who exchanged plants, whether brought to the village or taken to another village), (2) very close (plants were exchanged with close relatives living in other villages: mother, father, children, grandparents, siblings), (3) close (plants were exchanged with uncles, cousins, or nephews of other villages), and (4) distant (plant exchanges with brother-in-law, sister-in-law, mother-inlaw, father-in-law, living in other villages).
Reported medicinal plant applications were separated into use categories according to the worldwide standard for disease classi cation of World Health Organization (WHO) (48). The idea of using this classi cation is not to standardize the traditional uses of plants, which go far beyond the WHO (48) classi cation, but to show the medicinal contexts in which plants are being applied and exchanged (49). We also considered that due to the context of use, some plants do not have a discrete distinction between medicinal and mystical or ritualistic.

Results
Twelve key interviewees participated in the research: four women and eight men ( ve people at Cantagalo, two at Morro dos Cavalos, and one person in each of the other Indigenous Lands). Five interviewees needed the help of a Portuguese-Guarani translator. The other interviews were conducted in Portuguese because the interviewees were both Guarani and Portuguese speakers. Their ages varied from 30 to 69 years. The interviewees were chiefs, leaders, teachers, and people who said that they did not have a speci c social position within the villages but who were indicated by the leaderships to participate in the research. Often, during the conversations, other people were present, sharing their knowledge about plant uses. Respecting the social context, we did not exclude them at these moments.
These key interviewees reported the use of 49 plant species of 27 botanical families (Table 1), and more than 87% of these species are native. The most representative family was Asteraceae with 6 species, followed by Myrtaceae and Fabaceae with 5 species each. The highest number of citations was for Jacaranda micrantha and Tabernaemontana catharinensis, each mentioned in three different villages. Four species were cited in two different villages: Schinus terebinthifolius, Luehea divaricata, Cabralea canjerana, and Petiveria alliacea. The other species were mentioned in only one village. Thus, there were 58 total citations of the 49 plants. indicated in other villages as suppliers or recipients of propagules. For this reason, these two villages were not included in the column of visited villages of the bipartite network (Fig. 2).
The reasons for the visits include the search for seeds and medicines, visiting relatives, political articulations, knowledge exchange, the strengthening of themselves and of the Guarani culture, helping each other, and the well-being associated with travels and visits.
We found a greater number of exchanges between villages whose interviewees have close relatives, corresponding to 17 exchanges. In contrast, there were 10 exchanges between villages in which the interviewees were not kinship related. Four exchanges occurred between villages with very close kinship, and two exchanges occurred between villages with distant kinship (Fig. 3). Therefore, villages where kinship was considered close or very close made 64% of the reported exchanges.
According to interviewee #1 (Tekoá Ka'aguy Porã, Retomada), "when visiting relatives, the place is always observed, if it is good for children, if it is healthy". During these visits, seedlings of medicinal plants and medicine knowledge are also exchanged. Interviewee #2 (Tekoá Jatai'ty, Cantagalo) said that most exchanges take place with plants ready to use, such as the barks or leaves; when the seeds or seedlings are available, they are exchanged, but this does not guarantee that the propagule will be established in The role and strength of ceremonies and prayers in healing and plant use procedures are highlighted by interviewee #7 (Tekoá Jatai'ty, Cantagalo): "Learning comes through praying, getting to know medicine and culture, listening to spirituality"; and M.B., from the same village: "When a patient is going to be treated at the opy, the karai feel the necessary medicines that will be strengthened along with praying to improve the patient, especially spiritual illnesses". The disappearance of the forests and the demarcation of territories were also mentioned, since every indigenous person keeps the ancestral territory in their memory, and for some of them, the idea of limiting a space to live becomes almost incomprehensible. For interviewee #3, "The native forest no longer exists, it was cut too much to feed ships, trains and other things that juruá invented for his work, and that today is the very death of many people [...] The Indian's pharmacy is the forest, but many medicines were cut. Today, if an Indian wants to take some medicine, or sh, he often cannot because the land or the river now has an "owner"." Many poã (remedies from the forest) are no longer found within the limited indigenous land, and searching for certain plants that are outside the demarcated territories incurs a risk of being mistaken for a criminal act. According to Interviewee #9 (Tekoá Yyn Moroti Vherá, MBiguaçu), "The territory is not restricted to the demarcated area, now many plants are found outside the area".
At Campo Molhado indigenous land, which is located in an ecotone, the chief reported the presence of a total of 24 plant species brought to the village that can be currently found only in the forests of Misiones in Argentina. In other villages, the lack or rarity of some important species in traditional medicine include plants such as Ipe (Handroanthus sp.) trees in Lomba do Pinheiro and Mbiguaçu, and katiguá (Trichilia sp.) and cipó-guembé (probably Philodendron bipinnati dum) at Retomada. Up to the time of this study, three of the seven villages had seedling nurseries for reforestation of native species of traditional importance.

Discussion
The in uence of Guarani plant exchange networks on Atlantic Forest composition In the Guarani cosmology, the natural world is closely connected with the supernatural world, which often occupies the same spaces (27,50). Within this cosmology, the maintenance of botanical knowledge with therapeutic functions is also important (51) Almost half of the plants exchanged were trees, followed by herbs. Heineberg and Hanazaki (35) observed similar results among the Laklãnõ-Xokleng (from Jê linguistic group), reinforcing the importance of knowledge about forest tree species of indigenous peoples. In the present study, these plants associated with exchanges have the potential to be incorporated in environments and phytophysionogmies different than those of the place of origin.
For example, among the Myrtaceae family -one of the most important in the Atlantic Forest, with several edible fruit species (28) (53,54), but for the interviewees, it is rare, and the individuals present in the studied villages come from the exchanges. In M'Biguaçu, all individuals of T. catharinensis were planted, brought in the 1980s, but of unknown origin.
Yerba mate, or ka'a, Ilex paraguariensis, is a species exchanged with cultural and medicinal value for Guarani (55,56). A variety of yerba mate with a lighter shade on the leaves were brought from Misiones to Campo Molhado indigenous land, and it is different from the one already found there, showing the potential of exchanges to increase the local variability of the species. Individuals of this species are also present in Morro dos Cavalos indigenous land, at Ombrophyllous Dense forest, which is not the attributed distribution for this species (usually occurring above 400 m of altitude (57)). This is another example of the transport of plants of cultural value to phytophysiognomies other than those of original occurrence. The historical relationship of yerba mate with indigenous peoples is not restricted to the Guarani: the species was also consumed among peoples of the Chaco and the Andes, where it does not occur spontaneously (56). The name "mate" is even derived from the Quechua word "mati", which means the gourd or porongo where the drink is traditionally consumed. This leads us to an interethnic network of relationships in which people probably exchanged and cultivated the plant (56). Oliveira and Esselin (56), based on Posey (58), t the plant in the category of semidomesticated because they are intentionally managed. If this management had not already taken place by the natives, it would have been more di cult to expand the herbs for economic exploitation, as occurred in the 19th century (56).
Another highly esteemed species is Cedrela ssilis, yary, which is considered a medicine of sacred value (1,16,51). It is a well-distributed species in South America and is one of the most threatened tree species, with a vulnerable status (54) due to the selective cutting and suppression of the Atlantic Forest. Given its cultural importance, it is likely that the Guarani historically contributed to the dispersion of this species through their exchanges. also from the Tupi group (60). The origin of this species is probably the Amazon rainforest (57).
Solanum mauritianum and Urera baccifera have a wide distribution both in the Atlantic Forest and in other Brazilian biomes, respectively (54). Both species were brought from the deciduous to semideciduous forest at Cantagalo and are mentioned in other studies with the Guarani (1, 16, 27), showing once again that the Guarani exchanges may have contributed historically to the composition of different phytophysiognomies.
Some species are naturally occurring in the phytophysiognomies of indigenous lands; however, they can be locally rare or absent. For example, Philodendron bipinnati dum is one of the plants that are named at Opy, so that their ja (owner) authorizes their use (1). It is native to all forest formations in southeastern Brazil (57). However, in Morro dos Cavalos, there was only one known individual, a fact that also motivated the exchanges. The whip horse, Luehea divaricata, is another important species in Guarani medicine (27). The species is present in the cerrado and in all formations of the Atlantic forest (53). Despite this, in Campo Molhado, it was reported as not available spontaneously, which motivated the exchange. Oliveira (27) reported the absence of the plant in Mbiguaçu and the request of people from this village to purchase seedlings for planting.
Guarani exchanges can also contribute to the distribution of non-native plants. Three species exchanged were probably introduced in Brazil in the colonial period (57). These plants were also recorded in studies by Oliveira (27) for Plectranthus barbatus among the Guarani of Mbiguaçu, Noelli (18) for Matricaria chamomilla and Cossio (16) for Cajanus indicus.
Additionally, the exchanges of parts of plants with no propagative potential, such as for Inga virescens taken from Campo Molhado to a village in the Pampa biome, re ect the distribution of knowledge and the broad spectrum that the relationship Guarani-plants reach. This species is related to altitude forests, being better distributed in the Mixed Rain Forest (61) and absent in Pampa.
Oliveira (27) discussed possible migratory routes that contributed to the transport of species of ora from seasonal forests from the interior of the South American continent to the Atlantic coast. Klein (62) elaborated a list with species that would be characteristic of these routes, some of them mentioned in our study: Para paray -Jacaranda micrantha, Yxonguy -Luehea divaricata and Pipi -Petiveria aliacea (27). According to Reitz and Klein (63), factors such as climatic uctuations could have favored seasonal forests so that certain species could reach the Atlantic coast, but Oliveira (27) states that the routes proposed by Klein overlap with the archeological sites of Guarani presence in southern Brazil, where many villages are also present today (27).
Guarani family, extended family We found that more than half of the plant exchanges occurred between villages whose interviewees had close relatives, but there were also exchanges between villages with no close kinship ties. The caveat here is that our categorization of kinship relations oversimpli es the Guarani concept of extended family. The concept of extended family is "the most widespread sociological model" in Amerindian social organizations (22,64). For Guarani, this organization is composed of several nuclear families (women and men who live together and their children) united by kinship and a nity relationships. Thus, an extended Guarani family can be made up of the wife (or a group of sisters) and her husband, the daughters married to their sons-in-law, unmarried children, and their daughters' children. In these bonds, the "blood" relatives are called retarã, a nity relatives are the towadjá, and the aggregates also recognized as relatives by the bonds with the host family are the guapepó. The extended family can include many domestic groups spread over several villages (20,22).
The Guarani understand the non-indigenous concepts of kinship (e.g., brothers, cousins, uncles, grandparents), and thus, we chose to maintain these distinctions in data collection without disregarding the existence of a context in which the family is extended. Thus, the relations between the relatives considered to be close and very close keep the exchanges active, although the nature of the non-related by kinship needs to be broadened under the perspective of extended families.
Being on the move is a way for the individual to maintain health and happiness (25). In this sphere, the sense of being in the Guarani world is added, such as the search for Yvy Marã'ey, the Land without Evils, and the mborayu, or reciprocity (20,50). These elements favor the exchange of plants between people and villages, which end up circulating in different phytophysiognomies while strengthening social bonds, kinship, and a nity relationships (22).
Teko porã, well-being, and eco-cultural health Within their extended territory, all tekoá (Guarani villages) are connected and, through their geographical distribution, represent the support and structure of the Mbyá world (65). Religiosity permeates the Guarani daily life, and Opy holds the position of the social, political, religious and educational center of the village (21,22,25). Ceremonies are usually mediated by karaí or opygua (spiritual leaders, shamans, prayers), who know how to receive and interpret divine words and have knowledge about healing and traditional remedies (5,21,22,27,66).
For the well-being and maintenance of Guarani customary practices, forest environments are essential, which permeate the reasons for migration in search of a good place to settle. Forest environments provide the essentials for health and happiness, good water and land, a source of food and medicines and direct contact with deities. Taking care of rivers, land, and forests is part of the individual and collective health that involves not only humans but also those who share these spaces in the natural and supernatural worlds, and these environments must be maintained for those that will come later because so did the ancestors (50, 67).
Although historically the Guarani have occupied the lower lands of the Atlantic Forest (68), in the archaeological record, there are Guarani sites in the three southern states of Brazil in the area of mixed rain forest and forest transition areas (10). Villages present in transition areas of phytophysiognomies (as shown in Fig. 1) can contribute to the Guarani interaction with a diversity of species and emphasize the effects of indigenous management of the Atlantic Forest landscape (see also Pereira Cruz et al. (30)).
For Guarani people, dreams and visions of older people often guide decisions when considering places to live, relating the natural environments to the cosmology of the Guarani way of life (27,67), highlighting their understanding of an intrinsic relationship between well-being and forests.
There are essential plants used in rituals that the Guarani seek to maintain. The small spaces in which indigenous lands are located, especially in southern Brazil, impose challenges to access and collect plants, such as orchids at indigenous lands near Porto Alegre and at Morro dos Cavalos (69), and medicinal plants (66). The interest in the presence of plants intended for women's health demonstrates, for example, the concern of communities to take care of everything that involves women's cycles and is also a way of maintaining traditional practices amidst social and environmental changes, without relying on medical assistance from juruá kuery (70,71). Noelli (18) emphasizes in this sense the exibility and structure of the Guarani medical system, which over the past centuries has sought the e cacy of both native and introduced plants to combat the entire arsenal of previously unknown diseases to which they were subjected, such as in uenza, smallpox, measles, malaria, typhus, yellow fever, venereal diseases, and tuberculosis.
Historically, the Guarani have demonstrated their exibility in dealing with the natural resources they have, in parallel with their sociocultural unity. The search for the necessary conditions for well-being and the understanding of eco-cultural health with an intrinsic link between health and forest also support the process of domestication of the landscape (72,73). Historical and continuous interactions with forests maintain important elements in the environment for cultural continuity in a healthy and safe way. Plant exchanges and the management of certain species can also provide information about possible domestication processes that may occur at different levels (27,28,30) and contribute to the continuous genesis of cultural landscapes of Atlantic forests.

Conclusions
Almost half of the plants reported were involved in some exchange between villages, which marks an intense movement of plants in the Atlantic Forest to strengthen health and culture and enrich the forest environments. In this sense, the Guarani are enriching their territories with species related to their traditional pharmacopoeia, both for physical and spiritual health. This process is related to the traditional mobility inherent to the Guarani people, also with contributions of the partnerships that have been established between the villages and educational institutions, the civil community, and the creation and maintenance of nurseries in the villages. We observed through this ow of plants and knowledge the real capacity of species to be incorporated in phytophysiognomies different from those in which they are usually described, such as, for example, the species characteristic of the Seasonal Semideciduous and Mixed Ombrophyllous forests taken to Ombrophyllous Dense forest. For Pereira, Noelli, Campos, Santos, Zocche (28), the Guarani contribution to the ecological con gurations of these environments, such as favoring some species, is still an open topic for study, which brings us to millennia of human in uence in the Neotropics. Currently, indigeneity in landscapes (72) is being registered and mapped, as territorial management plans have been developed in indigenous lands, adapting traditional botanical and ecological knowledge to contemporary reality.
The presence of indigenous communities, through the conscious management of the territory, helps to maintain species of ecological and cultural importance (29), sometimes threatened, being extremely important for the conservation of the biodiversity of the Atlantic Forest. This also opens the debate about what is native and exotic in the Guarani conception, especially when considering the scope of the original Guarani territory and the historical human interaction with the environments. Many species have been managed and transported in the past, and as we have seen, it is a process that is constantly ongoing. The plants that are migrating among very different phytophysiognomies, associated with human action, are related to the historical management and selection of important species that characterize landscape transformations, in addition to the natural adaptation processes that plants develop. The various purposes in which biodiversity is used re ect Mbyá's own mobility, whose expression of their way of being also happens through territoriality (24).
Recognizing and valuing Guarani knowledge and practices can help restore and conserve natural environments, as well as collaborate for health in a broader way of understanding, as well as develop more sustainable economic and management practices, in addition to providing a better understanding of occupation of the Atlantic Forest in its southern portion. These ideas have been developed in places such as Colombia and Suriname by the Amazon Conservation Team (ACT) (74) and among the peoples of the Rio Negro in the northwestern Amazon, for example (75). Encouraging public policies related to biodiversity and traditional peoples is instituted in the Convention on Biological Diversity (76), as well as in the Global Strategy for the Conservation of Plants (76), even though we are far from effectively achieving this goal (77).
The Atlantic Forest is a sacred and ancestral territory of immense cultural and environmental value to the world. It is essential to implement public policies that contemplate the safeguarding of these spaces, with the real participation of the people who live in it for longer timespans, such as the Guarani people.

Declarations
Ethics approval and consent to participate