Theories and Major Hypotheses in Ethnobotany

,1,2,3,4 1 1 1 OROU G. GAOUE* ,MICHAEL A. COE ,MATTHEW BOND ,GEORGIA HART , 1 1,5 BARNABAS C. SEYLER , AND HEATHER MCMILLEN

1Department of , University of Hawai‘iatMānoa, Honolulu, HI 96822, USA 2Faculty of , University of Parakou, Parakou, Benin 3Department of Geography, Environmental Management and Studies, University of Johannesburg, APK Campus, Johannesburg, South Africa 4Department of Ecology and Evolutionary , University of Tennessee, Knoxville, TN 37996, USA 5U.S. Forest Service, Northern Research Station, New York City Urban Field Station, Bayside, NY, USA *Corresponding author; e-mail: [email protected]

Ethnobotany has evolved from a discipline that largely documented the diversity of use by local people to one focused on understanding how and why people select for a wide range of uses. This progress has been in response to a repeated call for theory-inspired and hypothesis- driven research to improve the rigor of the discipline. Despite improvements, recent ethnobo- tanical research has overemphasized the use of quantitative ethnobotany indices and statistical methods borrowed from ecology, yet underemphasized the development and integration of a strong theoretical foundation. To advance the field of ethnobotany as a hypothesis-driven, theoretically inspired discipline, it is important to first synthesize the existing theoretical lines of research. We review and discuss 17 major theories and hypotheses in ethnobotany that can be used as a starting point for developing research questions that advance our understanding of people–plant interactions. For each theory or major hypothesis, we identify its primary predictions and testable hypotheses and then discuss how these predictions have been tested. Developing research to test these predictions will make significant contributions to the field of ethnobotany and create the critical mass of primary literature necessary to develop meta-analyses and to advance new theories in ethnobotany. Key Words: Hypothesis-driven research, medicinal plant selection, optimal defense theory, utilitarian redundancy model, taboo as luxury, theory in ethnobotany..

Introduction 1996). Exceptions include the theoretically ground- ed, extensive body of research in cognitive ethno- Ethnobotany, the science of survival (Prance botany (e.g., Atran 1998; Alexiades 1996: xii; et al. 2007), has long been concerned with its Brown 1977;Conklin1954;Hunn1975;Medin relationship to theory. In its early stages, ethnobo- and Atran 2004;Turner2000)whichledtogeneral tanical research largely consisted of acontextual lists principles of folk biological classification (Berlin of plants with their associated preparations and uses et al. 1973; Berlin 1973;Brown2000). Of partic- in remote areas (Balick 1996;Etkin1988). This ular interest are the principles of ranked work, and by extension the discipline, has been and biological essentialism. Fundamentally, people criticized as Bweak^ or Bpseudoscience^ tend to think/rank/classify plants and animals in (Albuquerque and Hanazaki 2009; Alexiades the same way across culture (folk biology), and this contrasts with the way they think/rank/classify oth- er elements of the world. Furthermore, there is a 1 Received 23 November 2016; accepted 22 August cross-cultural convergence in the way people realize 2017; published online 7 September 2017 that species appearance, behavior, and ecological niche are not randomly established but guided by

Economic Botany, 71(3), 2017, pp. 269–287 © 2017, by The New York Botanical Garden Press, Bronx, NY 10458-5126 U.S.A. 270 ECONOMIC BOTANY [VOL 71 lawful underlying internal processes (Medin and addition, Bennett (2005) noted that ethnobotanical Atran 2004). In contrast to cognitive ethnobotany, education also needs a major shift to meet the needs research in ecological ethnobotany has lacked clear of the discipline’s evolution. The challenges faced theoretical frameworks. Notable exceptions include by ethnobotany are similar to those of other sister biocultural research which focuses on an in-depth disciplines. For example, in the 1990s, several analysis of the biochemical basis and pharmacologic prominent ecologists questioned if the discipline of implications of food, psychoactive, and medicinal ecology had general laws or a unifying theory plant uses by local people (Etkin 1988;Johns (Aarssen 1997;Lawton1999; Marquet et al. 1986). As the discipline has continued to evolve, 2014;Weiner1995). As a result of this self-reflec- there has been a repeated call for a paradigm shift tion, ecology progressed as a discipline, moving and more theory-inspired research mainly in eco- from simply documenting patterns to understand- logical ethnobotany. ing the underpinning processes that generate eco- Nearly 40 years ago, Ford (1978) questioned wheth- logical patterns across time and spatial scales. Eth- er or not ethnobotany had a unifying theory, while nobotany, drawing inspiration from sister disci- Phillips and Gentry (1993a) criticized the predom- plines (ecology, evolution, , archeolo- inant use of descriptive studies in ethnobotany as gy, etc.), can do the same (Salick and Alcorn 2003). well as the lack of theoretical frameworks and/or The most promising hypothesis-driven ap- methodological rigor. This self-criticism successfully proaches to date have come from testing whether prompted more recent ethnobotanical studies to patterns of human use of align with follow the lead of Begossi (1996) by incorporating the predictions of the theoretical frameworks from ecological methods in ethnobotany but without a ecology (e.g., Albuquerque 2006; Albuquerque and clear theoretical framework. As a result, an increas- de Oliveira 2007; Alencar et al. 2010; Bennett ing number of studies, in an effort to include quan- 2007; Bennett and Husby 2008;Vandebroekand titative rigor, utilized species-area curves to estimate Balick 2012; Reyes-García et al. 2013b;Quirozand the diversity of species used by cultural groups, and van Andel 2015: Voeks and Leony 2004;Voeks ethnobotanical indices (see Hoffman and Gallaher 2007). However, for such efforts to expand beyond 2007). International and locally meaningful proto- individual research groups and sites, it is important cols and procedures for conducting ethical research for ethnobotanists to recognize the breadth of cur- are now considered essential components of the rent ethnobotanical theories and understand how research process. Recent efforts have focused on these theories can be used to develop testable hy- advancing ethnobotanical education based on inter- potheses. Further, it is critical for emerging ethno- disciplinary training, core concepts, and competen- botanists to be exposed to these theories in a sys- cies that bridge the natural and social sciences tematic way. We postulate that providing a synthesis (McClatchey et al. 2013). Though important, these that clearly identifies theories and major hypotheses approaches have not addressed Phillips and Gentry’s about people–plant interactions will focus future eth- (1993a,b) call for formulating a theoretical frame- nobotanical research toward delineating the theoretical work, emphasizing instead methodological rigor bases for plant selection and use by people. These (Albuquerque 2009) and a generalized use of eth- theoretical frameworks are resources for designing nobotanical indices (Hoffman and Gallaher 2007). research questions and developing testable hypoth- Acknowledging the persistent lack of theory- eses to advance our understanding of the dynamic inspired research in ethnobotany, Martin (2007,pp. relationships between plants and people. 23–25) detailed precisely how this progress could be For simplicity, we have adopted a less-rigid use of achieved using a hypothetico-deductive approach. the terms Btheory^ and Bhypothesis^ in this paper. This approach includes developing testable hypoth- However, readers should be aware of existing discus- eses (from theory or general principles) on the sions on theory and how it differs from a hypothesis, drivers of the patterns in people’s knowledge and a prediction, a model, or a universal law (Krebs use of their environment, collecting data collected 2000; Quinn and Dunham 1983). Hypotheses are using ethnographic methods, and using statistical proposed explanations of observed natural phenom- analyses to test if these data lend support (or not) to ena or patterns, whereas a theory is an Bintegrated these hypotheses. Recently, Bennett (2005) and and hierarchical set of empirical hypotheses that Albuquerque and Hanazaki (2009) repeated the call together explain a significant fraction of a scientific for Bless quantification^ and more theory-inspired observation^ (Krebs 2000). As such, theories are and hypothesis-driven research in ethnobotany. In hypotheses which have been rigorously tested and 2017] GAOUE ET AL.: THEORIES AND MAJOR HYPOTHESES IN ETHNOBOTANY 271 for which we found support for the generalization. disproportionately large number of exotic plants Most of the theories or hypotheses we present are utilized in . They acknowledge adapted from ecology or related disciplines and traditional medicine as dynamic systems and sug- serve as possible explanations of ethnobotanical pat- gest possible drivers of this phenomenon. terns. Some of these theories have not yet been The versatility hypothesis suggests that introduced formally presented as major theoretical frameworks plants are incorporated as medicine by way of ex- among ethnobotanists. For this reason, we refer perimentation with introduced food and ornamen- mostly to Bhypotheses^ with the understanding that tal plants (Alencar et al. 2010; Bennett and Prance they represent part of the nascent theoretical body 2000). This hypothesis has been supported by sev- of ethnobotany. In cases where a given hypothesis eral studies that found a high proportion of non- has been widely tested and accepted in ethnobota- native medicinal plants were first introduced as food ny, or where the name is carried directly from a and ornamental plants (Bennett and Prance 2000) theory in ecology, we use the term Btheory.^ or for other non-medical uses (Ceuterick et al. In this paper, we review 17 theories and major 2008; Jernigan 2012). Documenting the chronolo- hypotheses used in ethnobotany with a strong focus gy of the incorporation of different plant uses would on economic ethnobotany. This review is selective be important for futures tests of this hypothesis. and representative, but not exhaustive. Scholarly The versatility hypothesis has also been expanded works were selected to cover the diversity of to suggest versatility is a positive selection factor for question-oriented research in ethnobotany based on plant use in general (Alencar et al. 2010). Thus, this the lead author’s teaching and research experience. hypothesis predicts that people are more likely to We group the theories/hypotheses into two main retain knowledge, use, and access to a plant that has categories that relate to the overarching questions that a greater number of applications for humans. It also each set seeks to address (Table 1). The first set of predicts that the most cosmopolitan plants (those hypotheses addresses how and why people select used in the largest number of regions) are the most plants for ethnobotanical use. The second set ad- versatile since versatile plants would be more likely dresses the implications of plant selection by people to be shared or carried by emigrants to new areas. and addresses how people mitigate the potential This has been tested by comparing the number of negative effects of plant use. For these theories and uses reported for introduced and native medicinal hypotheses, we clearly identify their central predic- plants, but it has found mixed support (Alencar tion(s). In addition, we discuss refinements to these et al. 2010). The versatility hypothesis, in this theories and hypotheses based on how they have broader sense, overlaps with the plant use value been tested in the literature. For related hypotheses, hypothesis (see below), as use value indices are we provide a discussion on how they interrelate and largely versatility indices, and therefore, these two why some of them should be tested separately, theories could benefit from further integration. despite similarity. In cases where we do not identify The availability hypothesis states that plants are rigorous tests of a given theory or hypothesis from used for medicine because they are more accessible the literature, we suggest methodological ap- or locally abundant (Albuquerque 2006;Voeks proaches and statistical analyses to test their predic- 2004). This hypothesis was born, in part, out of tions. Finally, we call for a shift in ethnobotanical studies revealing the importance of anthropogenic educational approaches to increase the awareness habitats or disturbed areas in provisioning weedy and application of these theories/hypotheses, and and introduced species for medicine (Gavin 2009; train ethnobotanists to develop and implement the- Stepp and Moerman 2001;Voeks2004). Availabil- ory-inspired, hypothesis-driven research. ity is often conceptualized as a physical distance from a home or community to the location where a plant grows in the wild, but could also be consid- How and Why Do People Select Plants ered in terms of seasonality, abundance, price, as for Ethnobotanical Uses? well as access to markets, gardens, or natural areas where plants are found (Albuquerque 2006; THE VERSATILITY,AVAILABILITY, AND Estomba et al. 2006). The availability hypothesis DIVERSIFICATION HYPOTHESES has been tested by examining the location where people indicate they collect medicinal plants and, The versatility, availability, and diversification more broadly, by correlating the local abundance or hypotheses attempt to explain the increasing or dominance of plants with use-values. The 272 ECONOMIC BOTANY [VOL 71

TABLE 1. OVERARCHING QUESTIONS IN ETHNOBOTANY contexts. A multi-dimensional index incorporating AND THE ASSOCIATED THEORIES OR HYPOTHESES.REF- ecological, socio-cultural, economic, and political ERENCES REPRESENT AUTHORS WHO PROPOSED OR FOR- aspects and drivers of availability could be used to MALIZED THE THEORY/HYPOTHESIS, OR KNOWN TO test the availability hypothesis in different contexts. HAVE TESTED IT THE FIRST TIME. The diversification hypothesis explains the incor- Questions, theories, or major hypotheses poration of exotic plants in traditional medicine as enriching culture, rather than being a response to 1. How and why do local people select plants for use? cultural erosion or environmental degradation 1.1. Is plant selection directly related to the demographic (Albuquerque 2006). The diversification hypothesis traits of the plant? suggests that exotic plant species are selected to fill A. Versatility hypothesis (Alencar et al. 2010; Bennett and Prance 2000) therapeutic vacancies in an ethnopharmacopoeia, B. Availability hypothesis (Albuquerque 2006; Voeks perhaps due to novel bioactivity, thereby diversify- 2004) ing the set of treatment options (Albuquerque C. Plant use value hypothesis (Phillips and Gentry 1993a, b) 2006; Alencar et al. 2010, 2014). This hypothesis D. Theory of non-random plant selection (Moerman has been supported by studies which found that 1979, 1991) exotic medicinal plants provide medicinal treatment E. Optimal foraging theory (Sih and Christensen 2001) not available from native plants (Albuquerque F. Doctrine of signatures (Bennett 2007;Etkin1988) 2006; Alencar et al. 2014;Santosetal.2014)and 1.2. Is plant selection directly linked to its ? that exotic medicinal plants provide different bioac- A. Diversification hypothesis (Albuquerque 2006;Alencar tive compounds than native medicinal plants et al. 2010) B. Optimal defense theory (Mckey 1974; Zangerl and (Alencar et al. 2010). Rutledge 1996) C. Ecological apparency hypothesis (Albuquerque and PLANT USE VALUE HYPOTHESIS Lucena 2005; Feeny 1976) D. Resource availability hypothesis (Coley et al. 1985; The plant use value hypothesis proposes that the Stepp 2004) usefulness of a plant (e.g., for medicine, food, con- 1.3. How social dynamics and human traits affect plant struction, technology, or trade) in a given commu- selection? nity is directly related to its botanical family, life A. Age, gender, and dynamics of knowledge (Voeks 2004, form, local abundance (density), and/or maximum 2007) size (Phillips and Gentry 1993a,b). This work was B. Urbanization and knowledge loss (Voeks and Leony 2004) highly influential in providing a pathway to apply C. Social network and knowledge dynamics (Hopkins statistical analyses to ethnobotanical data through a 2011) use value index. The statistical approach could be 2. What are the conservation and livelihood implications of improved further by testing the additive effects of plant use? plant traits in the same statistical model, rather than 2.1. What are the implications of plant selection to the testing the individual effects of these traits in sepa- people and the plant? rate models. This would help account for the fact A. Cultural keystone species (Garibaldi and Turner 2004) that people often select plants for use based on B. Utilitarian redundancy model (Albuquerque and de multiple traits at the same time. The multiple pre- Oliveira 2007) dictors approach (additive model of family, life 2.2. How do local people mitigate the negative effect of plant use? form, abundance, and maximum size) is what sep- A. Taboo as luxury (Rea 1981; Quiroz and van Andel arates the plant use value hypothesis from the avail- 2015) ability hypothesis (Albuquerque 2006)orthetheory B. Taboo as conservation strategy (Colding and Folke of non-random plant selection (Moerman 1979)and 1997, 2001) the apparency hypothesis (Gonçalves et al. 2016), each of which propose single predictors (e.g., num- ber of species per family or species abundance). hypothesis has received mixed support Although the plant use value hypothesis suggests (Albuquerque 2006; Gonçalves et al. 2016;de that the utilitarian value local people associate with a Oliveira Trindade et al. 2015), with native species given plant species is solely a function of the traits of sometimes preferred, despite their lower abundance the plant species, several other factors related to the or accessibility. Further investigations should focus individual collector can also influence estimates of on defining what availability means in different use value. For example, Lawrence et al. (2005) 2017] GAOUE ET AL.: THEORIES AND MAJOR HYPOTHESES IN ETHNOBOTANY 273 found that gender, ethnicity, age, and proximity to Phillips and Gentry (1993b) found family to be a markets all had an influence on the perceived im- strong determinant of plant use value. Moerman portance of wild harvested plants for local people. In (1991) explains that species in the same family, due that study, women tended to place more impor- to their evolutionary relatedness, share some char- tance on , whereas men placed more impor- acteristics of plant defense, inherited from common tance on timber. Studies that have entirely or pri- ancestors, which influence their physiology and ef- marily focused on male participants (Galeano 2000; fectiveness as medicines. Certain plant families have Phillips and Gentry 1993a) may bias conclusions chemical compounds more useful or effective as toward plants considered important by men. The medicines (e.g., Asteraceae), while other families socio-cultural and demographic backgrounds of the are much less useful as medicines (e.g., Poaceae researchers themselves can also influence the out- because they often depend on resprouting and phys- come. Pfeiffer and Butz (2005) described how ical defenses rather than chemical defenses). Sup- gender-imbalanced field research has biased ethno- port for this hypothesis requires linking chemical biological data collection, hypothesis testing, and activity with plant selection and disentangling the application of theory. Contrary to Phillips and Gen- impacts of other factors as drivers of this over- and try (1993a), who calculated plant use value indices under-representation of particular families. Further, from interviews, Lawrence et al. (2005) asked par- if non-random plant selection is driven primarily by ticipants to list and rank the ten most important bioactivity, we would expect that species within a plants they had harvested from the forest over the family used for a particular illness would have the last 10 years. They also interviewed participants to highest bioactivity relevant to that illness (under the contextualize their findings and allowed use catego- over-simplifying assumption of single plant recipes). ries to emerge from interviews. This emic approach This could be tested by comparing the medicinal may provide more reliable data, as results could be uses of a set of related species with their respective cross-checked with interviews, and factors such as concentrations of bioactive compounds. Finally, the efficacy, frequency, palatability, and availability theory predicts that plant families which are closely could be integrated by the participant themselves related are more likely to have similar medicinal uses in determining which plants are important. than those that are phylogenetically distant (Saslis- Lagoudakis et al. 2014; Yessoufou et al. 2015). THEORY OF NON-RANDOM PLANT SELECTION THE DOCTRINE OF SIGNATURES The theory of non-random plant selection was de- veloped by Daniel Moerman (Moerman 1979, 1991, The doctrine of signatures has been used as a 1996). It was intended, in part, to counter the belief framework to understand the medicinal plant selec- at the time that Native American medicine was only tion process in traditional cultures. As early as 40– placebo (Moerman 1979). If traditional medicines 90 AD, Dioscorides wrote of a plant species that were only placebo, he contends, plants would be resembled a scorpion’s tail, which coincidentally selected at random with respect to plant family. The was used to treat scorpion attack (Bennett 2007). theory of non-random selection predicts that me- The Doctrine of Signatures suggests a plant’sform dicinal plant selection is not random. The number recapitulates its function—where physical or senso- of medicinal species in a given plant family in a ry characteristics of plants (shape, color, taste, and given region would be a linear (on a log scale) smell) reveal their potential therapeutic value and function of the total number of plant species in that use (Bennett 2007; Leonti et al. 2002). In this family. However, particular plant families tend to be context, specific plant characteristics are used in over- or under-represented in a given pharmacopeia the identification of species’ potential medicinal (Moerman 1979, 1991; Moerman and Estabrook qualities. For example, the presence of antimicrobial 2003) and as food (Moerman 1996). and hemostatic red quinones found in some species This theory is one of the most widely tested in of red plants potentially reflect their common use ethnobotany. For example, non-random plant se- and ethnomedical application for healing a variety lection by family has been confirmed with the of epidermal disorders (Etkin 1988). Although the ethnopharmacopoeia in Amazonian Ecuador doctrine of signatures is primarily concerned with (Bennett and Husby 2008), in Belize (Amiguet plant’s form, in a wider sense, it can include organ- et al. 2006), in Kashmir (Kapur et al. 1992), and oleptic . For example, pungent odors or in Hawai’i (Ford and Gaoue 2017). Additionally, bitter tastes may reflect the presence of 274 ECONOMIC BOTANY [VOL 71 monoterpenes or corresponding not only OPTIMAL DEFENSE THEORY to a given plant’s physiological properties but also its potential medicinal/therapeutic application Several plant defense theories, borrowed from (Bennett 2007; Leonti et al. 2002). ecology, have been adapted to ethnobotany to ex- Thedoctrineofsignaturesisavaluable plain why local people select medicinal plants from mnemonic aid for traditional cultures that fa- a given life form, habitat, or plant part cilitates the transmission of knowledge about (Albuquerque et al. 2012; Almeida et al. 2005; its uses (Bennett 2007; Leonti et al. 2002). How- Coley et al. 2003; de Lucena et al. 2012). These ever, most scholars dismiss the doctrine of signa- plant defense theories are based on the premise that tures as Bprimitive^ or Bprescientific^ (Bennett plants produce chemicals to protect themselves 2007) even though its major predictions have been from herbivory and that this defense comes at a cost rarely tested. Most existing work on the doctrine of to the fitness of the plant, which is proportional to signatures lists different signatures that correspond the of herbivore attack, and the abiotic resource with a given plant and the therapeutic functions the available for the plant’sgrowth(EndaraandColey plant provides (Dafni and Lev 2002). In one of the 2011; Feeny 1976;Mckey1974; Rhoades and rare direct tests of the doctrine of signatures, Ben- Cates 1976). nett (2007) tested if plants with heart-shaped Plant chemical defense is classified into two were used in cardiac medicine. Out of the 80 species broad categories: quantitative and qualitative de- randomly selected from a literature review, 21 were fense. Quantitative defense obligately uses digest- used as medicine and only 3 were used in cardiac ibility reducers such as lignins that are immobile, are medicine, indicating no support for the doctrine of difficult for herbivores to adapt to, and have low signatures. However, people in the selected studies rates of turnover but require a large energy invest- may not associate the human heart with the form ment to produce. Qualitative defense uses highly resembling a BValentine’sheart,^ so failure to find a active molecules such as alkaloids that are toxic to significant proportion of species with cordate leaves herbivores at low concentrations, have high turn- being used to treat cardiac disease does not provide a over rates, are often facultative and mobile, and rigorous test of the doctrine of signatures. Further require low energy investments, but can be adapted work through and semi- to by specialist herbivores (Feeny 1976;Rhoades structured interviews could explore the types of and Cates 1976). clues (potentially signatures) that healers use to The optimal defense theory predicts that plant identify plant species to test for medicinal uses. tissues that are unlikely to be attacked by herbivores Another approach would be to use a binomial re- or which have low fitness value have low amounts of gression with the presence or absence of a given quantitative defense but high inducibility of quali- signature as the predictor and the indicated thera- tative defense compounds, while tissues that are peutic function as the response variable. For exam- likely to be attacked or have high fitness value ple, one could test if a given plant is more likely to should have high levels of quantitative defense and be a galactagogue, based on the presence or absence low inducibility of qualitative compounds (Mckey of white . 1974; Zangerl and Rutledge 1996). Therefore, It is important to note that the meanings of from an ethnobotanical perspective, if humans se- medicines are subjective but not trivial. These lect medicinal plants to optimize secondary chem- meanings affect their efficacy in all cultures. For istry, they would more likely select plant organs that example, the color of a pill can be a Bsignature^ or are subject to less frequent herbivory because these signal of its therapeutic value to its consumer. organs would have more qualitative than quantita- Moerman (2002) reported how the same pharma- tive defenses which are more useful for medicinal ceutical had different effects based on its color. Pills purposes. Furthermore, young leaves/plants are colored blue were reported to promote sleep among more likely to have qualitative defenses such as that associate blue with tranquility, but alkaloids (with more medicinal use) than quantita- in Italy, where blue is the color of a popular football tive defenses that take time to develop, so they will team, the pills colored red had more of a soporific be selected more often for medicinal purposes than effect than the blue ones. old leaves/plants (Coley et al. 2003). 2017] GAOUE ET AL.: THEORIES AND MAJOR HYPOTHESES IN ETHNOBOTANY 275

THE ECOLOGICAL APPARENCY AND RESOURCE antimicrobial activity than plants from a high re- AVAILABILITY HYPOTHESES source environment (especially herbs), which often had qualitative defense compounds but with lower The ecological apparency hypothesis is directly re- antimicrobial activity. lated to the optimal defense theory. The primary Testing many of these ethnobotanical hypotheses prediction of this hypothesis is that species with is challenging because of difficulties in quantitative- short lifespans (non-apparent) face lower herbivore ly assessing the chemistry of plants and accounting pressure and are more likely to use Binexpensive^ for how compounds may interact. For example, qualitative defenses whereas species with long using dried plant material can potentially reduce lifespans (apparent) face higher herbivore pressure actual bioactivity (Kursar and Capson 1999), and and invest in more Bexpensive^ quantitative de- failing to compare the plant part used medicinally fenses (Feeny 1976). Qualitative defense com- with other plant parts not used medicinally can bias pounds (e.g., alkaloids) have more medicinal bioac- results (but see McCune and Johns 2007). The tivity than quantitative defense compounds (e.g., synergistic effects of combining multiple species in lignins). Thus, from an ethnobotanical perspective, one medicine is also difficult to understand (see Coe Bnon-apparent^ plants (short lived, herbaceous, ear- and McKenna 2017). Future studies could explore ly successional) are more likely to be used for med- the widespread practice of using certain plant parts, icine than Bapparent^ plants (perennial, woody, harvest times, and harvest places in relation to the dominant plants) (Albuquerque and Lucena 2005). genetic and phenotypic chemical variation of plants The resource availability hypothesis shares the pre- as predicted by these two theories and if the dispro- dictions of the ecological apparency hypothesis. portionate use of exotic plants as medicine in some However, it suggests that plant defense investment contexts is primarily due to their high intrinsic is not primarily related to the risk of herbivory but growth rate rather than for diversification purposes. to the resource level of the habitat to which the plant is adapted (Endara and Coley 2011). The OPTIMAL FORAGING THEORY resource availability hypothesis predicts that species adapted to high resource environments (e.g., high- The optimal foraging theory is also borrowed from light, nutrient-rich habitats) are more likely to grow ecology. The theory predicts that foraging organ- quickly and use qualitative defense, while species isms will balance the benefit received from a food adapted to low resource environments (e.g., low- with the effort it took to search for and eat that food. light, nutrient-poor habitats) are more likely to grow BGeneralists^ will consume a wide variety of avail- slowly and have high levels of defense—primarily able resources, regardless of their energy content, quantitative but also qualitative (Coley et al. 1985; because they are readily available, while Bspecialists^ Endara and Coley 2011;Stamp2003). Fast-grow- will use energy to seek out only a few kinds of ing/short-lived species that can tolerate higher rates resources that provide high energy content (Perry of herbivory and invest more in qualitative defense and Pianka 1997). This theory stems from the (e.g., alkaloids) will have more medicinal uses and will optimality model—a mathematical model from be more sought after than long-lived/slow-growing ecology applied to animals foraging for food species which invest more in quantitative defenses. (Charnov 1976). This might explain why some weeds and plants in When applied to ethnobotany, the optimal for- disturbed areas or secondary vegetation are sometimes aging theory predicts that (1) individuals will place more highly sought after locally for medicinal purposes higher value that yield more benefit per than non-weedy plants and those in primary forests unit of foraging/processing time; (2) as the abun- (Stepp and Moerman 2001;Voeks2004). dance of plants with higher value increases, plants Few studies have tested the above theories in with lower value will no longer be used; and (3) ethnobotany. Of those that have, most found no individuals should have a quantitative threshold to support for the ecological apparency hypothesis, decide when specific plants should be included or but they did provide support for the resource avail- excluded (Sih and Christensen 2001). These hy- ability hypothesis (Alencar et al. 2009; Almeida et al. potheses have been adapted in ethnobotany to un- 2005, 2012). Almeida et al. (2012) found that derstand how people select plants for use for food, plants from a low resource environment (especially medicine, or construction and are related to the ) tended to have high levels of quantitative and diversification or availability hypotheses and the qualitative defense compounds and have higher taboo as luxury hypothesis. 276 ECONOMIC BOTANY [VOL 71

Tests of the optimal foraging theory that quantify there are various arguments put forward to explain the distance or time spent acquiring the resource these patterns. For example, accumulating medici- and the benefit of the resource are rare, but they nal plant knowledge is a life-long process, so elderly suggest that generalist and specialist strategies for people have simply had more time to acquire it harvesting food plants exist simultaneously. For (Brandt et al. 2013;Hanazakietal.2013), while, food, most harvesting takes place around dwellings, in many traditional cultures, women serve as the but people will travel long distances to collect large primary healthcare providers in their families, so it is amounts of highly nutritious resources (Ladio understandable their medicinal plant knowledge is 2001). Energy use is also optimized by collecting greater than that of men (Albuquerque et al. 2011). larger amounts of resources that require longer However, the context in which knowledge trans- preparation time (Nascimento et al. 2013). Al- mission occurs can influence results. For example, though individuals have high knowledge of the use in a medicinal plant market context, patterns found of plants around their dwellings with low nutrition- in other studies on the effects of level of formal al value, foraging is more selective in farther ecosys- education, age, and years of experience did not hold tems where there are plants with higher nutritional true (McMillen 2012). value (Ladio 2001). In the only current test of this Difficulties in testing this hypothesis relate to hypothesis for the collection of medicinal plants, how the variables are defined and measured. For Soldati and Albuquerque (2012) show that people example, men and women may possess different preferred to collect plants from closer sites regardless kinds of knowledge due to their different culturally of the quantity or quality of products they can defined gender roles (e.g., agroforestry versus me- collect from these sites. dicinal plant knowledge), so the type of knowledge Although limited in number, these ethnobotan- investigated matters (Albuquerque et al. 2011; ical tests support the predictions of the optimal Brandt et al. 2013; Souto and Ticktin 2012). Sim- foraging theory, which are also generally well sup- ilarly, which plants are chosen to test ethnobotanical ported within ecological research (Perry and Pianka knowledge can be a proxy for knowledge type. 1997;SihandChristensen2001). Limitations to Clearly, selection of plants primarily used by one ethnobotanical tests of the optimal foraging theory gender would bias the study if gender roles are not include lack of geographic diversity, difficulty quan- properly taken into account (Brandt et al. 2013; tifying nutritional value, lack of consideration for Hanazaki et al. 2013;SoutoandTicktin2012). cultural value, and lack of accounting for the poten- Comparing different studies based on age can also tial confounding effects of age and gender. be difficult since the intervals for age classes used are arbitrary (Hanazaki et al. 2013), and the length of AGE,GENDER, AND DYNAMICS OF KNOWLEDGE residency in a community can be a stronger predic- HYPOTHESIS tor of local plant knowledge than age (Gandolfo and Hanazaki 2014). Finally, socio-cultural variables This hypothesis suggests that various individual interact with each other, in that the effect of one socio-cultural and demographic traits such as gen- variable depends on the level of another (Souto and der, age, and literacy/formal educational level are all Ticktin 2012). Thus, to test this hypothesis, studies correlated with an individual’s level of plant knowl- should be designed carefully to measure each vari- edge (Albuquerque et al. 2011; Hanazaki et al. able in the local context and account for the inter- 2013; McCarter and Gavin 2015; Souto and active effect of these predictors of local knowledge Ticktin 2012; Voeks and Leony 2004;Voeks dynamics. In addition, while most studies simply 2007). Age and gender are the most commonly tested if there was any significant difference in examined variables (Albuquerque et al. 2011), with knowledge between gender or age group, it is im- women and older people tending to have greater portant to directly test hypotheses related to the knowledge of the local medicinal (Albuquer- mechanisms/processes that generate such age- or que et al. 2011; Torres-Avilez et al. 2016;Voeks gender-based knowledge patterns. and Leony 2004). Higher literacy and greater access to formal education are often negatively correlated URBANIZATION AND KNOWLEDGE LOSS with medicinal plant knowledge (Voeks and Leony HYPOTHESIS 2004;Voeks2007). Although most studies rarely provide mechanistic explanation for why age or This hypothesis explores the effect that urbaniza- gender and literacy can drive knowledge dynamics, tion has on . The general 2017] GAOUE ET AL.: THEORIES AND MAJOR HYPOTHESES IN ETHNOBOTANY 277 prediction is that urbanization (and commercializa- adoption of lingua francas, and Western healthcare tion of plant products) decreases traditional and/or services (Furusawa 2009; Gandolfo and Hanazaki local ecological knowledge. Drawing from the fields 2014; Reyes-García et al. 2007; Voeks and Leony of anthropology and economics, multiple authors 2004; Zarger and Stepp 2004); or various combi- report a negative impact of various measures of of these factors (Gandolfo and Hanazaki urbanization on the preservation/retention of local 2014;ZargerandStepp2004). Carefully defining ecological knowledge (Brandt et al. 2013; Gandolfo which type of knowledge is being tested and what and Hanazaki 2014; Reyes-García et al. 2013a; measure of urbanization is being used will provide Sogbohossou et al. 2015; Voeks and Leony 2004). more accurate tests of this hypothesis and facilitate In many regions of the world with rapid economic future meta-analyses. development, pressures for rural communities and minority ethnicities to assimilate, abandon tradi- SOCIAL NETWORK AS DRIVER OF KNOWLEDGE tional practices in favor of modern conveniences, DYNAMICS and economic necessities have significantly contrib- uted to acculturation and the increased endanger- Social network theory is increasingly used in ment of traditional knowledge systems. However, various disciplines to document the interplay be- scholarship has yielded conflicting results, with tween natural systems and human knowledge sys- some authors finding that the link between urban- tems, including the distribution and dissemination/ ization and knowledge loss is not straightforward preservation of ethnobotanical knowledge within (Furusawa 2009), that knowledge is not lost but societies (Crona and Bodin 2006;Hopkins2011; rather transformed (Mathez-Stiefel et al. 2012; Wasserman and Faust 1994). This theory states that Poot-Pool et al. 2015), that knowledge survives the nature and structure of relationships shape the (selectively) or remains constant (McMillen 2012; flow of information in social networks (Granovetter Müller-Schwarze 2006; Zarger and Stepp 2004), or 1973). In ethnobotany, the derived hypothesis pre- that knowledge actually increases with urbanization dicts that the knowledge of an individual is (Vandebroek and Balick 2012). influenced/shaped by the individual’spositionin These mixed results in testing the link between their social network and the collective knowledge urbanization and loss of knowledge may be due to of that network. The primary predictions of this several factors. First, the various studies may be hypothesis are that individuals who are more con- looking at different kinds of knowledge (Müller- nected will have greater knowledge, that more con- Schwarze 2006; Reyes-García et al. 2007; Souto nected networks will have a more uniform distribu- and Ticktin 2012). Some knowledge types may tion of knowledge, and that the uniform distribu- benefit from urbanization to the detriment of other tion is more robust/resilient to being lost. types. Secondly, what may be called Burbanization^ Boster (1986) was one of the first to show that is not directly comparable from study to study, due women’s agricultural knowledge was more influ- to differing geographic or cultural scales (Müller- enced by an individual’s number of relationships Schwarze 2006;VandebroekandBalick2012). Ad- (analogous to degree centrality) than by . ditionally, studies do not always clearly define ur- Hopkins (2011) showed a weak positive correlation banization and use different measures of urbaniza- between in-degree centrality (how many people tion, such as size, e.g., towns/cities in refer to an individual as a knowledge source) and contrast to rural areas and increases in population medicinal plant knowledge. Similarly, Kawa et al. over time (Zarger and Stepp 2004); rapid develop- (2013) found that individuals perceived as knowl- ment of previously rural areas (Gandolfo and edgeable by their community tend to have higher Hanazaki 2014; Mathez-Stiefel et al. 2012;Reyes- in-degree centrality, although this result may be García et al. 2013a); isolation versus proximity to confounded by other variables. Reyes-García et al. roads and market towns (Reyes-García et al. 2007, 2013a found a significant correlation between agro- 2013a); migration from rural to urban areas ecological knowledge and betweenness centrality (a (Gandolfo and Hanazaki 2014;Mathez-Stiefel measure of how one’s position within the social et al. 2012; Srithi et al. 2009; Vandebroek and network enables one to influence it). Díaz- Balick 2012); economic development and introduc- Reviriego et al. (2016) also showed a significant tion of new industries, e.g., tourism, logging, and correlation between degree centrality (the number coffee production and various measures of of contacts an individual has in a network) and Bmodernization,^ such as public education, medicinal plant cultivation (as a proxy for medicinal 278 ECONOMIC BOTANY [VOL 71 plant knowledge), suggesting that social interaction to be used in trade and/or resource acquisition increases medicinal plant knowledge. (Garibaldi and Turner 2004). Prior studies often The characteristics of a social network are only infer species’ cultural keystone status by using spe- some of many factors that can affect the dynamics of cies cultural importance indices (Platten and ethnobotanical knowledge. While observed varia- Henfrey 2009;Francoetal.2014), which are ex- tion of ethnobotanical knowledge in the studies pected to measure Bthe importance of the role it discussed above may be due to the social network, plays within a particular culture^ (Turner 1988). when conducting social network analyses, it is im- These approaches have been criticized (Tardío and portant to simultaneously investigate the confound- Pardo-De-Santayana 2008; Thomas et al. 2009) ing influence of individual attributes such as age, and it is unclear whether indices commonly used gender, religion, education level, and ethnicity. to measure cultural importance also capture the fundamental components of the cultural keystone species theory. In addition, measuring cultural irre- The Implications of Local People’s Plant placeability is challenging. Because cultures are dy- Selection on Both Plants and Culture namic and resilient, they can adapt to new condi- tions by replacing a critically important species with CULTURAL KEYSTONE SPECIES another one once the original becomes scarce. Beginning in the 1970s, several hypotheses were The cultural keystone species concept stems from developed to link species ethnotaxonomic diversity the ecological keystone species concept first coined with their cultural importance (Berlin 1973;Turner by Paine (1969) when referring to certain species 1973). Ethnotaxonomic diversity refers to the rich- that are essential to the stability of ecological sys- ness and relative abundance of vernacular names tems. Similarly, the cultural keystone species theory used for a given species of plant included within a suggests that certain species of plants or animals are folk taxonomy of a particular cultural group. The fundamental to socio-cultural systems and that the theory of ethnotaxonomic diversity predicts that loss of these species would result in negative impacts species identified by several traditional names with- on and stability (Cristancho and in a native language are likely to be culturally im- Vining 2004; Garibaldi and Turner 2004). Cultural portant (Berlin 1973;Turner1973), possibly be- keystone species are Bculturally salient species that cause the names employed may capture varietal or shape in a major way the cultural identity of a utilitarian diversity (Berlin 1973; Martin 2007). particular cultural group^ (Garibaldi and Turner Further, it has been predicted that plants employed 2004). The cultural keystone species theory, as for food, medicine, technology, ritual, and/or reli- proposed by Garibaldi and Turner (2004), was gion are likely to have nomenclatural recognition (at not meant to be tested but rather as a framework a generic level) which reveals their cultural impor- to underscore the importance of particular species tance (Turner 1973). Direct tests of these predic- that underpin cultural identity and wellbeing. How- tions are currently lacking, but would further our ever, this framework provides the opportunity to understanding of cognitive ethnobotany. test hypotheses related to biocultural diversity dy- namics. One hypothesis that can be tested from this UTILITARIAN REDUNDANCY MODEL HYPOTHESIS theory is that a decline in biological diversity will be coupled with a loss of plant knowledge. One way to The utilitarian redundancy model (Albuquerque test this hypothesis would be to select a set of plant and de Oliveira 2007; Ferreira et al. 2012)isan species with different degree of rarity (common, ethnobotanical hypothesis analogous to the ecolog- rare, extinct). Then one could test if local people ical redundancy hypothesis (Walker 1992). Unlike have lower knowledge score of extinct or rare species the ecological redundancy model, which is used in compared to common species. evaluating the functional redundancy of ecosystem Similar to the ecological keystone species, identi- components from a biological perspective, the util- fying cultural keystone species has proven challeng- itarian redundancy model seeks to evaluate natural ing. Cultural keystone species are expected (a) to resource use by human populations and aid in have high use values, (b) to have functions within defining conservation priorities for culturally impor- the psycho-socio-cultural structure of a particular tant species of medicinal plants and animals cultural community, (c) to have ethnotaxonomic (Albuquerque and de Oliveira 2007;Nascimento diversity, (d) to be culturally irreplaceable, and (e) et al. 2015). Here, utilitarian redundancy refers to 2017] GAOUE ET AL.: THEORIES AND MAJOR HYPOTHESES IN ETHNOBOTANY 279 the idea that several species can be used for the same the nature–culture nexus (McDonald 1977). In purpose and/or share the same therapeutic function. seeking to understand how The utilitarian redundancy model proposes that might live in harmony or balance with the natural species that share the same therapeutic function world, the idea of taboo as a conservation strategy (i.e., functional redundancy) are redundant and are was popularized. Cultural taboos are informal insti- predicted to experience reduced use-impact as the tutions that determine human behavior (Colding use pressure is diffused across a greater number of and Folke 2001). They involve restrictions by cer- species (Albuquerque and de Oliveira 2007). Addi- tain sectors of society on the use of particular re- tionally, the loss of redundant species is predicted to sources and habitats, sometimes only at particular have no overall effect on the ethnomedicinal prac- times or in particular places (Colding and Folke tices of a particular cultural group regardless of the 2001). Cultural taboos are an important aspect of reduction of the number of species used to treat a medicinal plant selection by traditional societies given therapeutic function (Nascimento et al. throughout the world. 2015). The main challenge in testing the utilitarian The taboo as a conservation strategy hypothesis redundancy model is related to the difficulty in suggests that certain plant and animal species are accurately measuring realized utilitarian redundan- made taboo to protect them from overexploitation cy. Three main factors make such measures com- and extinction. This hypothesis has been tested by plex. First, for medicinal plant species that are ver- comparing a list of taboo species for a given region satile and used for multiple purposes, therapeutic with their International Union for Conservation of redundancy does not necessary guarantee lower use Nature (IUCN) red list status (Colding and Folke pressure. Second, it is critical to consider the local 1997). This study showed that 30% of the identi- preference of particular species within a given ther- fied taboos prohibited any use of species listed as apeutic function. Preferred species employed by a threatened by IUCN. However, using a global particular group may be under greater use pressure threat status such as the IUCN red list to measure despite therapeutic redundancy with multiple other local threat status may be misleading. Such tests species (Ferreira et al. 2012). Third, the disease could be improved by using an emic approach to profile of the study region defines which diseases estimate the local threat level of species listed as are more common and which ones are rarer. A taboo from local people’s perception of species vul- species that has unique therapeutic function may nerability. One could then use a binomial regression still be under lower use pressure if the disease it to test if a species is likely to be endangered from an treats is rare in the region. emic perspective, if it is already taboo. Accurately measuring therapeutic redundancy re- Except for Colding and Folke (1997) who provide quires that one not only estimate the number of other a direct test of the theory, most studies have ex- species with similar therapeutic functions but also rank plored taboo as conservation through literature re- redundant species by preference from an emic per- views. Evidence includes the correlation of stronger spective, as well as weight redundancy by the frequen- taboos with either habitats or animals that have cy of the disease groups considered in the study region. greater need for conservation (Colding and Folke Even with an accurate measure of therapeutic redun- 1997; McDonald 1977). The similarity of some dancy, high use pressure at a local level does not resource and habitat taboos with Western conserva- necessarily suggest that these species are under threat tion management approaches has also been used as as this depends on the harvesting rate, part harvested, evidence to support this hypothesis (Colding and species life form, and the ecological conditions in Folke 2001). However, there are non-conservation which harvesting takes place (Ticktin 2004). reasons for taboos, such as teaching and enforcing cultural norms, toxicity of particular organisms, the maintenance of certain animals or pets, as a custom How Local People Mitigate the Negative following the death of a high-ranking individual, or Effects of Plant Use because of the spiritual meaning or significance of a species or place (Bhagwat and Rutte 2006). Taboos TABOO AS A CONSERVATION STRATEGY are common in traditional societies across the world HYPOTHESIS and they have been found to sometimes, but not always, align with conservation actions (Bhagwat During the 1970s, attention toward environ- and Rutte 2006; Colding and Folke 1997). For mental conservation sparked a renewed interest in taboos to qualify as conservation strategies, they 280 ECONOMIC BOTANY [VOL 71 must not only prevent species decline and habitat theories, from ethnobotany and related fields, were degradation but also be deliberate (Smith and grouped into two main categories which correspond Wishnie 2000). The authors found weak evidence to two central questions of interest in ethnobotany of such deliberate conservation actions. It would be (Table 1). useful for future tests of this hypothesis to distin- The first set of theories covers three main facets of guish between the objectives of a given culture or the central question: what drives medicinal and food community in enforcing a taboo and the outcomes plant selection by local people? The first subset of or consequences of that choice (potentially of con- these theories/hypotheses tests if plant selection is servation value). directly related to the demographic characteristics of the plants themselves, including abundance and TABOO AS LUXURY HYPOTHESIS availability (Table 1; 1.1). Each of these theories/ hypotheses suggests, directly or indirectly, that the The taboo as luxury hypothesis predicts that the probability a given plant species is selected is a proportion of taboo plants in a given culture will be function of how many individuals of the species greater in communities where natural resources are are available (e.g., abundance, distance to collection abundant such that some can be spared from gen- sites) for selection, how visible (e.g., height, life eral use (Quiroz and van Andel 2015;Rea1981). It form, appearance) these individuals are, and how also predicts that traditional societies in resource- well the populations are functioning (e.g., growth rich areas will be more likely to employ taboos than rate). A second subset of this group asks if plant societies in resource poor areas. selection by local people is directly linked to their In one of the rare direct tests of the taboo as phytochemistry (Table 1; 1.2). For example, the luxury hypothesis, Quiroz and van Andel (2015) diversification hypothesis (Alencar et al. 2010)asks compared the number of ritual plant species be- if local people are introducing some plant species to tween Gabon, a forested country with 4700 plant improve the diversity of botanicals available to treat species, and Benin, a country dominated by savanna the range of diseases in their communities. The with 2800 plant species. The authors showed that optimal defense theory (Mckey 1974;Stamp2003), ritual plant species in Benin were more likely to be which is also related to both the ecological apparency scarce and officially threatened than in Gabon. This and the resource availability hypotheses, suggests that provides evidence of less reliance on taboos in the the distribution of secondary chemistry within a resource-rich region of Gabon than in Benin. How- given plant drives the selection of plant organs for ever, the scale of analysis may limit the reproduc- medicinal purposes. While the optimal defense the- ibility of these conclusions. Country-level plant spe- ory provides the framework to understand why cies richness may not accurately account for species people would select instead of leaves from availability to a given community where a taboo is the same plant for medicinal purposes, the resource actually enforced, species preference by a local com- availability hypothesis (Endara and Coley 2011)ex- munity, and/or the total number of useful species plains why some plant species in some habitats are employed within a given ethnopharmacopeia. In used more than others. Together with the theory of short, this approach may not capture the non-random medicinal plant selection and its ex- Bluxurious^ status of resources at the local commu- tension from a phylogenetic perspective (Saslis- nity level where species are listed as taboo or not. A Lagoudakis et al. 2014; Yessoufou et al. 2015), more robust test of this theory would compare the these theories explain how phylogenetic relatedness proportion of taboo species between villages with (e.g., belonging to the same family, genus, or bo- different levels of species richness and availability. tanical groups) explain medicinal plant selection. Previous work interpreted the apparency hypothe- sis in a broader ecological sense (Albuquerque and Discussion Lucena 2005; Gonçalves et al. 2016). These authors suggest that because Bapparency^ can be interpreted SYNTHESIS OF THE DIFFERENT THEORIES AND as Babundance^ (herbivores attack the most HYPOTHESES apparent/abundant species), it ought to be consid- ered within other hypotheses developed above such We reviewed 17 major hypotheses and theories as the plant value use hypothesis, the availability which have been used to investigate the relationship hypothesis, and the theory of non-random medici- between people and plants. These hypotheses and nal plant selection. However, we choose to separate 2017] GAOUE ET AL.: THEORIES AND MAJOR HYPOTHESES IN ETHNOBOTANY 281 these hypotheses because this allows for the devel- of richness in the options that local people have to opment of predictions to better understand the use their resources. The taboo as conservation hy- thought process leading to plant selection by local pothesis suggests resource and habitat taboos serve a people rather than the pattern of plant selection. conservation purpose for communities. The ecological apparency hypothesis, as proposed by Culture and human behavior are complex. Many Feeny (1976), was more interested in explaining the of the theories/hypotheses presented here assume differential chemical response to herbivory of groups humans are rational and efficient in their choices, of plants (apparent versus non-apparent) than though we know human behavior is actually more apparency itself. From that perspective, we argue that complex and often culturally determined. For ex- the ecological apparency hypothesis should be tested ample, local explanatory models of health and illness separately from these other hypotheses. as well as local understandings of kincentric rela- The third subset of this group of theories/ tionships with other non-human organisms critical- hypotheses explores how social dynamics and peo- ly influence how, when, where, and why people ple’s demographic characteristics (e.g., local people’s collect one plant over another. Therefore, the age or gender) or environment (e.g., urban, rural) theories/hypotheses we presented could be enriched drive plant selection (Table 1; 1.3). For example, through further integration with relevant anthropo- the social network as driver of knowledge dynamics logical theories related to culture and human behav- hypothesis (Hopkins 2011; Reyes-García et al. ior and should be tested with a strong awareness of 2013b) provides the framework to investigate why cultural context. Furthermore, the amount of time a and how who an individual knows defines what the researcher spends in a community and the re- individual knows and how s/he selects plants for searcher ’s level of cultural competency can directly local uses. Such peer influence and how this influ- influence data reliability, interpretations, and one’s ences transmission of knowledge will also depend ability to account for such cultural context. This is on the age and gender of people within a given particularly true for studies that rely upon interview network. Additionally, the characteristics of the so- data where the level of trust, the characteristics of cial network are likely to depend on whether a given the person asking the question, and other contextual community is rural or urban. The age, gender, and factors will influence the way a participant responds dynamics of knowledge hypothesis predicts how cer- (Hofisi et al. 2014). Finally, although these tain traits of local people, including ethnicity or theories/hypotheses have been presented separately, socio-linguistic diversity, drive their choices. they are not always mutually exclusive and, in many The second set of theories/hypotheses investi- cases, are complementary. For example, the avail- gates the conservation and livelihood implications ability and versatility and diversification hypotheses of plant use (Table 1; 2). The first subset of this are complementary. It is quite possible that some group of theories/hypotheses focused on the impli- species are selected as medicinal plants not only cations of plant selection on a given plant and/or because they are available but also because they have cultural community (Table 1; 2.1). For example, been used for multiple purposes already. Similarly, the utilitarian redundancy model (Alencar et al. there is synergism between selection of plants for 2014;Nascimentoetal.2015) provides the frame- their ecological traits and the socio-demographic work to ask if plants with unique therapeutic func- traits of the local people using these plants. For tions are under greater harvesting pressure. The example, some plant species that are abundant cultural keystone species theory (Garibaldi and may not be relevant for women’s health. As a result, Turner 2004) adds to the uniqueness criteria, with availability will not be a strong predictor of plant several other criteria (ethnotaxonomic diversity, use selection and use for women in that case. We pre- value, psycho-sociological functions) providing a sented these theories/hypotheses separately for sim- novel framework to identify and understand the plicity purpose. However, we encourage ethnobot- unique cultural importance of particular species. anists to explore further the synergisms, comple- The second subset of hypotheses provides the mentarity, and contradictions between them. framework to investigate the direct or indirect ef- fects of traditional resource management strategies IMPLICATIONS FOR FUTURE RESEARCH AND on plant conservation (Table 1;2.2).Thetaboo as TEACHING IN ETHNOBOTANY luxury hypothesis (Rea 1981; Quiroz and van Andel 2015) provides the basis to ask if creating taboo is Ethnobotanical education has rightly focused on motivated by the need to conserve or an indication training emerging ethnobotanists in key concepts 282 ECONOMIC BOTANY [VOL 71 and methods such as interviews, participant obser- grant from the College of Natural Sciences at vation, free-listing, livelihood analysis, and emic the University of Hawai‘iatMānoa. versus etic approaches (Martin 2007). The potential to learn about medicine, psychoactive plants, or the natural connection to land and organisms can Author Contributions OGG conceived of the idea for the paper, outlined and structured its content, drafted the intro- draw students into the discipline of ethnobotany. duction and discussion, and coordinated the overall process. However, our ability to keep them in this discipline MAC, MB, GH, and BCS drafted the sections on specific is directly linked to the level of mastery they have in theories or major hypotheses. HM contributed primarily to developing research frameworks and methods that the introduction and discussion with an emphasis on anthro- are consistent with the scientific methods used in pological perspectives and contributions. All authors contrib- other disciplines. Learning the fundamental theories uted to the final revision of the paper. of a discipline is one of the first steps in understand- ing that discipline, generating new knowledge, and furthering the discipline’s understanding of patterns Literature Cited and processes. We suggest that ethnobotanical edu- Aarssen, L. W. 1997. On the progress of ecology. cation follow this strategy. While ethnobotanical Oikos 80:177–178. courses should continue introducing concepts and Albuquerque, U. P. 2006. Re-examining hypothe- methods while also providing inspirational historical ses concerning the use and knowledge of medic- accounts of the discipline, it must also clearly and inal plants a study in the Caatinga vegetation of deliberately expose students to the breadth of theo- NE Brazil. Journal of and Ethno- ries and major hypotheses in this field. We should medicine 2:(30): 1-10 further focus on the ability of students to identify ———. 2009. Quantitative ethnobotany or quan- the central predictions of these theories, and we tification in ethnobotany? Ethnobotany Re- should discuss how related hypotheses have been search and Applications 7:1–3. tested, which ones are yet to be tested, and why ———., and R. F. de Oliveira. 2007. Is the use- testing these new hypotheses will advance our impact on native Caatinga species in Brazil re- knowledge of how and why local people select duced by the high species richness of medicinal plants for medicinal, food, and cultural uses. Given plants? Journal of Ethnopharmacology 113: that ethnobotanical programs are becoming rarer 156–170. (McClatchey et al. 1999;Bennett2005) and most ———., and Hanazaki N.. 2009. Commentary: ethnobotanists encounter just a limited number of Five problems in current ethnobotanical ethnobotany courses, using such approaches to ex- research—And some suggestions for strengthen- pose students to the theories will be instrumental for ing them. 37:653–661. them to choose research topics, develop methodol- ———., and R. F. P. Lucena. 2005. Can ogies, and ultimately add to our collective under- apparency affect the use of plants by local people standing of these important issues impacting all in tropical forests? Interciencia 30:506–511. humans, our environment, and the resources on ———.,G.T.Soldati,S.S.Sieber,M.A.Ramos,J. which we depend. C. De Sá, and L. C. De Souza. 2011. The use of plants in the medical system of the Fulni-ô people Acknowledgements NE Brazil. A perspective on age and gender. This paper is inspired by discussion with Journal of Ethnopharmacology 133: 866–873. two generations of undergraduate students in ———., M. A. Ramos, and J. G. Melo. 2012. New the Theory and Methods in Ethnobotany strategies for drug discovery in tropical forests (BOT 440) course taught by the lead author based on ethnobotanical and chemical ecological at the University of Hawai‘iatMānoa whose studies. Journal of Ethnopharmacology 140: questions and insights shaped this paper. We 197–201. are grateful to Bob Voeks, Ulysses Albuquer- Alencar, N. L., T.A.des Araujo, E. L. C. de que, and Tamara Ticktin for the comments Amorim, U. P. Albuquerque, T. Antonio, D. and insightful discussion on the earlier versions S. Araújo, E. Lúcia, et al. 2009. Can the of this manuscript and to two anonymous apparency hypothesis explain the selection of reviewers for the valuable comments on the medicinalplantsinanareaofCaatinga manuscript. OGG is supported by a startup 2017] GAOUE ET AL.: THEORIES AND MAJOR HYPOTHESES IN ETHNOBOTANY 283

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