Significance of the use of medicinal plants within the municipalities
The patterns in traditional knowledge and medicinal plant use described in this study is in accordance with other studies [25–27] in the high number of introduced species mostly herbs. Especially for the more accessible municipality of Zetaquira the use of native species was rarely reported.
Rapid adoption of introduced species in traditional medicine can be understood as a response to new opportunities arising with globalisation. Inefficacy of native species may lead to experimentation with introduced species. Introduced species enrich the arsenal of species used in treatments and are often seen as very powerful [28–30]. Adoption of introduced species may be seen as a way to reshape and re-vitalise traditional practices, which in many places provide an important alternative to the official health care services within developing countries.
The effectiveness of treatments with popular introduced plant species that are used world-wide indicates the need to promote and further the studies on the use and effectiveness of these plant species [23, 24]. In the Colombian pharmacopoeia list of officially accepted plants for medicinal use 44% of the total of 149 species are introduced [23, 31].
The flip-side of the coin is that with the adoption of introduced medicinal plant species peoples’ interest in cultivating native species decreases. In this study most of the popular medicinal plant species (UV >0.5) were introduced with the exception of Verbena littoralis and Ambrosia cumanensis (Table 4 and 7). Furthermore, a number of native species with multiple uses, e.g. timber but also medicinally, are currently endangered or have disappeared from the regions indicating that over- exploitation has taken place [27].
The high similarities between estimated and/or actual UV (> 50%) for introduced and native plant species showed little difference in the lists of medicinal plants between the municipalities. For introduced species, similarity values were the highest (Table 10). These results are comparable to the findings of De Ameida et al. [28] who worked with rural communities in the Northeast Brazil.
Overexploitation of medicinal plant species, including a large number of native species, has been discussed extensively. Njoroge et al. [32] found that Carissa edulis (Forssk.) Vahl, a native wild species of Ethiopia [33], is a priority species used in the treatment of several ailments, especially for stomach pains, a common disorder in the Mwingi District, Kenya. Presently, this species is threatened by overuse. Similarly, other scholars have reported that plant species most popularly used by communities depend on the kind of local diseases that people face [2], which could be a parameter to identify possible species that could become endangered by overexploitation in combination with knowledge on plant parts used, harvest techniques, demand and prices.
The most frequent diseases in the study sites according to local reports from the health centre service [34] were related to the digestive system and infections caused by bacteria, parasites or fungi. The present study shows that the highest valued species were related to exactly these diseases. Of these, the top five were all introduced (Tables 4 and Table 7) confirming that communities make use of specific plant species including introduced ones.
The large number of plant species used in the treatment of complaints of the digestive system, infections and nervous system in both municipalities, is comparable to other findings from studies involving farmer communities in other localities in department of Boyacá. For example, Lagos [9] found that stomach-complaints occupy the category of illnesses which is treated with the highest number of medicinal plant species, followed by complaints of the nervous system. At the same time, these results are comparable to findings from other places. In the municipalities of the city of Imbituba, Santa Catarina, Brazil Zank and Hanazaki [35] found, that digestive complaints were the disease category with the highest therapeutic applications of medicinal plants. Furthermore, Neves et al. [36], who studied various groups of the community of Trás-os-Montes, Portugal, including farmers, reported that illnesses related to the digestive system were most popularly treated with medicinal plants.
Life form, habitat and proximity to cities facilitate popularity of introduced species
It has been demonstrated in several studies [28, 37, 38], that life form and habitat specification determine the use of medicinal plant species. The reason usually mentioned is that herbs, of which a large number are introduced, are easy to cultivate and maintain in small gardens or pots near to or in the houses. Examples of species whose popularity can be related to life form and the ease of cultivation are Ruta graveolens that has a high medicinal value in Zetaquira, and Urtica dioica that is a highly valuable herb in Campo Hermoso. Opposed to the introduction of easily cultivated herbs, a number of ecological factors diminish advantages of cultivation and maintenance of some native plant species.
Among the most popular species of amateur healers (eight species), seven species (87.5%) were introduced, of which six were herbs and only one a shrub (Table 12). In contrast, among healers the tendency to use native species, usually trees or shrubs, is higher: 57% of their most popular species was native and included two herbs and one vine. Since healers are specialised in the use of medicinal plants, they are in most cases willing to cultivate a diversity of species, including trees and shrubs with medicinal values, in their home gardens and on other cultivated lands. Hence, cultivation could explain the popularity of native woody species within the group of healers.
The high significance of introduced plant species according to UV (Table 8) in Zetaquira closer to the capital of the department, Tunja, could be an indication of the influence of distance to modern cities and acculturation upon the adoption of new medicinal plant species. These findings are comparable to results obtained by other studies, e.g. in Brazil, Argentina and Manus Island (Papua New Guinea) [28, 39, 40]. Inhabitants of Campo Hermoso, which is more remote and follows rural traditions, have higher knowledge on medicinal plant use. Furthermore, there are more healers in Campo Hermoso. Hence, the null hypothesis of similarity between plant knowledge and use between municipalities is falsified.
High presence of pharmacologic components in herbs and popularity of genera
The high presence of pharmacologic components in herbs makes them attractive for treatments of different diseases [27]. Specifically the high composition of alkaloids in leaves facilitates medicinal uses as has been indicated by the popularity of these plant parts within several communities [9, 25, 27, 36] and also in the present study. Furthermore, a number of phytochemical studies have proven remarkable alkaloid and oil content in herbal leaves [41–43] which may provide alternatives for the pharmaceutical industry. Taxa with large numbers of useful herbs contribute to the tendency of using leaves and introduced plant species. For example, the genus Mentha, one of the most popular taxa in Campo Hermoso and Zetaquira and, was reported to be used in treatments of digestive complaints, colds, fevers, skin infections, inflammations and headaches (Table 4). Mentha ssp., introduced to the American continent, is widely popular in folk medicine [9, 35, 44] and contribute to the popularity of introduced plant species.
Popularity of plant families
Popularity may also reflect world-wide presence of large plant families, such as the Lamiaceae. Contrary, Schippmann et al. [1], suggest that popularity of plant families is related to the local availability of the species. Studies in diverse localities as for example in Loja province, Ecuador [45], Imbituba, Santa Catarina, Brazil [35], Sierras de Córdoba, Argentina [46], and Banbungo, Cameroon [27] have found Asteraceae and Lamiaceae with high numbers of plant species used locally. These findings are comparatively similar to the results obtained by ethnobotanical studies carried out in the department of Boyacá, e.g. the studies of Lagos [9] in five municipalities in the central part of Boyacá, and a study carried out in the municipality of San José de Paré by Toscano [10]. The results indicate a large availability of species belonging to the Asteraceae and Lamiaceae in this region. At the same time, these results are comparable to the global pattern suggested by Moerman [47] who considered that Asteraceae and Lamiaceae are among the most used plant families in traditional medicine world-wide.
In relation to the popularity of Asteraceae, Garcia Barriga [48] reported that this family is the taxonomic group of plant species with the highest use in traditional medicine in Colombia. Nevertheless, the large range of distribution of this family may explain part of the popularity of this taxonomic group in folk medicine [27].
Furthermore, plant families, such as the Apiaceae, Apocynaceae and Guttiferae, of which there are examples of species with medicinal use in Campo Hermoso and Zetaquira, are part of the list of plant families with high numbers of traditionally used species worldwide [1].
However, 85% of the medicinal species identified in this study have been described and reported as medicinal in Colombia [11, 48–50]. Of these species, 54% are introduced. This indicates that transmission of knowledge on introduced medicinal species has been successful in Colombia and in the studied municipalities. Similar situations have been observed and discussed in other countries as Brazil [28] where it was observed that knowledge of introduced plant species within farmers communities has been well established.
Promotion, conservation and sustainable use of native medicinal plant species may be facilitated by including shrubs and trees into local agroforestry systems. A number of these species, apart from being medicinal, offer also other kind of uses, e.g. as food, source of wood and shade. Such multiuse plants are often valuable to locals [31].
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