Influence of socio-demographic factors on medicinal plant knowledge among three selected ethnic groups in south-central Ethiopia

Background The influence of socio-demographic variables was widely explored to evaluate their impact on indigenous and local ethnobotanical knowledge. However, the studies conducted in Ethiopia mainly focused on rural areas. They were limited to exploring and documenting ethnobotanical knowledge and the associated impacts of socio-demographic variables in rural–urban interface areas among ethnic groups. Hence, this study aimed to document plant-based indigenous and local ethnomedicinal knowledge and the associated impacts of socio-demographic variables among selected three ethnic groups in south-central Ethiopia. Methods Ethnobotanical data were collected using semi-structured interviews with 189 key informants, floristic species inventories, and field observations. Quantitative approaches were used to evaluate the use values (UV) of the most important medicinal plants, the informant consensus factor (ICF), fidelity level (FL), relative popularity level (RPL), and rank-order priority (ROP). Statistical tests were applied to evaluate the influences of socio-demographic factors and associations between variables on local ethnobotanical knowledge across ethnic groups in different informant categories. Results Statistical analysis revealed significant differences (p < 0.05) in the mean number of medicinal plants reported among age categories. There was also a positive association between the respondent's age and plant knowledge acquisition. Croton macrostachyus Hochst. ex Delile, Albizia gummifera C.A.Sm., Zingiber officinale Roscoe, Aloe macrocarpa Tod., Gymnanthemum amygdalinum (Delile) Sch.Bip., Calpurnia aurea (Aiton) Benth, and Allium sativum L. had the highest use values among ethnic groups. The highest informant consensus factor values were recorded for circulatory system disorders (0.68) followed by febrile illness and reproductive organ complications (0.66 each) across the three studied ethnic groups. The highest FL, RPL, and ROP values were noted for Lactuca inermis Forssk., Moringa stenopetala (Baker f.) Cufod., Withania somnifera (L.) Dunal, Allium sativum L., Citrus limon (L.) Osbeck, Ricinus communis L., Schinus molle L., Antiaris toxicaria (J.F.Gmel.) Lesch., Brucea antidysenterica J.F.Mill., Echinops kebericho Mesfin, Ocimum jamesii Sebald, Afrocarpus falcatus (Thunb.) C.N.Page, Searsia natalensis (Bernh. ex Krauss) F.A.Barkley, and Ricinus communis L. across ethnic groups in the study areas, which showed the conformity of knowledge on species curing potential and their prevalent uses. Conclusion The study revealed that the ethnic groups of Gedeo, Oromo, and Sidama have considerable indigenous and local ethnobotanical knowledge practices. Statistical analysis shown high variation in the acquisition of local ethnobotanical knowledge among age groups, which boosted our understanding of the effects of socio-demographic factors on the local ethnobotanical knowledge dynamics. Thus, this finding advocates for efforts to repair the observed generation gap via continued professional support and educating local communities to preserve traditional knowledge and practices through systematic documentation.


Introduction
Long before were scientific inquiry established, humans created, disseminated, and utilized information about the natural world [1].Over millennia, indigenous peoples across the globe have developed, maintained, and evolved knowledge systems through direct interaction with biophysical and biological processes and species [1,2].As a result, knowledge held by people about their environment evolved gradually and accumulated throughout their histories [3].Across the globe, including Ethiopia, this local knowledge was significantly dependent on generations' constant connection with their surroundings and elders [3,4] and regarded as a body of place-based knowledge accumulated and transmitted across generations within specific cultural contexts [1,3,5].According to [5][6][7], indigenous and local knowledge is not only direct observation and contact with the environment but also a wide range of cultural and spiritual knowledge and values that enhance human-environment relationships.Ethnobotanical studies conducted elsewhere explained the associations between socio-demographic factors and knowledge of plant use [4,[8][9][10][11][12].Some of them revealed that age and ethnobotanical knowledge have a direct relationship and that ethnobotanical knowledge accumulation increases with an individual's age [8][9][10]13] and is widely used among communities with poor health facilities [12].Others explained the influences of gender and education level: males and lower-grade attendees were more familiar with the medicinal values of local flora [4,8], and traditional healers possess richer ethnobotanical knowledge than laypeople [10,13].Thus, the cultural variables seem essential in explaining and determining plant use knowledge [5,10,14].
Ethiopia is one of the world's most ethnically and culturally diverse country, with over 70 different languages spoken across and more than 80 distinct ethnicities [16,17].Several ethnobotanical studies have been conducted to document traditional medicinal plant knowledge and the associated factors elsewhere in the country [4, 8-10, 13, 16, 19-25].However, they are insignificant when compared to the 80 diverse ethnolinguistic communities, and most of them are largely unexplored and limited to rural areas.According to CSA [25], south-central Ethiopia is home to diverse ethnic groups, representing more than half of the country's indigenous ethnic communities; but, evidences from [8, 18-20, 23, 24, 26-29] reveal that studies conducted on medicinal plants have so far focused in the south and southwestern parts, covering only a few out of the estimated 45 or more socio-cultural (language) groups.Thus, medicinal plant resources and indigenous knowledge about the use of medicinal plants in south-central Ethiopia, particularly in the current study's peri-urban area, are inadequate.
As a result, the current study was conducted to fill this gap by documenting the abundance of indigenous and local ethnobotanical knowledge and understanding the corresponding socio-demographic drivers among the three ethnic groups in south-central Ethiopia.Specifically, the study aimed at (i) documenting plant-based indigenous and local ethnomedicinal knowledge of the Gedeo, Oromo, and Sidama ethnic groups against human ailments in Dilla, Shashemene, and Hawassa peri-urban areas, respectively; (ii) evaluating the impact of sociodemographic variables on medicinal plant knowledge among the three studied ethnic groups; (iii) determining the use values (UV) of the most important medicinal plants among the three studied ethnic groups; and (iv) identifying potential medicinal plant species among the three ethnic groups for future phytochemical and pharmacological investigations.The hypothesis is that medicinal plant knowledge varies depending on the socio-demographic variables among ethnic groups.The study will contribute scientific information about the medicinal flora and associated ethnobotanical knowledge, as well as understanding the influences of sociodemographic variables on local and indigenous medicinal plant knowledge in the rural-urban interface areas of south-central Ethiopia.

Description of the study area
The study was conducted in three selected sites of neighboring ethnic groups in the south-central part of Ethiopia: Hawassa, Shashemene, and Dilla.Administratively, Hawassa district is part of the Sidama National Regional State, whereas Shashemene and Dilla districts are parts of the Oromia and Southern National Regional States, respectively (Fig. 1).Nine peri-urban kebeles (lowest administrative units; three from each study site) were purposely selected at different distances from the periurban administrative parts of Hawassa, Shashemene, and Dilla (Fig. 1).These areas were chosen because the ethnic groups living in the districts have coexisted and interacted for many years in specific regions of south-central Ethiopia.Additionally, they are geographically close to the town, have similar urbanization pressures, and are facing aggressive degradation of natural resources owing to urbanization [30][31][32][33] Hawassa is situated 273 km south of Addis Ababa [34], at 6°55′-07°06′N and 38°25′-38°33′E, with elevation ranges of 1656 to 2137 m a.s.l.[35].The borders of Hawassa area are defined by Lake Hawassa to the west, Oromia National Regional State to the north, Wondo Genet and Malga districts to the east, and Shebedino and Gorge districts to the south.Hawassa had 15,720 hectares of land within its administrative boundary, while only 6,465 hectares (24.4%) were demarcated within the municipal boundary and planned as urban land, while the rest is rural land [34].Administratively, the city was organized into three tiers of administration: which divided into 8 sub-cities and 32 kebeles (lowest administrative units) (Hawassa City Administration annual unpublished report, 2019).Among the sub-cities, Hawella-Tulla and its 12 kebeles were categorized as rural and rural-urban interface areas, where the current study was conducted (Fig. 1).Residents of the study area are ethnically and religiously diverse.The majority of indigenous and local people living in the area are Sidama (48.68%), followed by Amhara (15.43%),Welaita (13.9%),Oromo (5.21%), Gurage (4.33%) and others (12.45%),CSA [25].The major language spoken in the area belongs to the Sidama ethnic group 'Sidamu afoo' (47.97%), followed by Amharic (31.01%),Welaita (9.58%), Afan Oromo (2.53%), Gurage (1.98%), Kembata (1.82%), and others (5.09%).More than half of the people in the research area practice the Protestant religion (52.71%), followed by Ethiopian Orthodox Christianity (39.99%),Islam (7.3%), and Catholicism (3.78%).According to the CSA [25] population forecasts, the projected population for 2022 was 555,480, of whom 277,032 were males and 278,448 were females.

Informant selection
To ensure a detailed representation of indigenous and local knowledge dynamics and plant uses, traditional healers of the three ethnic groups were selected based on their gender, age, experience, level of education, and religion.For the survey, 189 key informants (133 males and 56 females) with the age range of 35 to 77 were selected using purposive and snowball sampling techniques based on recommendations from local communities, local government heads, and development workers following [16,17].Of the total, 63 were from the Sidama (43 males and 20 females), 63 were from the Oromo (41 males and 22 females), and 63 were from the Gedeo ethnic group (49 males and 14 females).Informed consent has been obtained from all informants who served as informants before the start of the interviews.

Ethnobotanical data collection and specimen identification
Ethnobotanical data were collected from January to May 2023, using semi-structured interviews with local traditional healers and inventories of plant species following an approach of [40][41][42].The first session included information regarding the socio-demographic characteristics of the informants.Secondly, information related to the detailed ethnobotanical application of the local flora.Most of the interviews were carried out in local languages (Sidamu Afoo, Afan Oromo, and Gedeoffa) with the help of local

Table 1 Detailed locations of the study sites
The agro-ecologies are described based on the agro-climatic zone classification of Ethiopia, Tesemma [39] Study translators or a language native to the respective research locations.Each ethnic group studied was an indigenous and local resident of the study area.All floristic voucher specimens were collected with the help of traditional healers and development professionals.Specimens were identified in the field and later confirmed at the National Herbarium of Addis Ababa University and Wondo Genet College of Forestry and Natural Resources, Hawassa University using taxonomic keys and flora [43][44][45][46][47][48].The verified specimens in the National Herbarium were further checked using Plants of the World Online (https:// powo.scien ce.kew.org.) websites to confirm the correctness of the scientific names and author citations.Finally, the plants were dried, pressed, mounted on a herbarium sheet, and placed at Hawassa University's Wondo Genet College of Forestry and Natural Resources Herbarium.

Data analysis
Both qualitative and quantitative data were analyzed using the ethnobotanyR package, Version 0.1.8,2022.Age, gender, education, and religion were used to determine the impacts of socio-demographic variables on ethnobotanical knowledge.The Kruskal-Wallis chi-squared test, a non-parametric approach to the one-way ANOVA, was performed between age, education, religion, and the number of medicinal plants cited, and the Wilcoxon test for gender.The mean and standard deviation of the number of medicinal plants reported concerning the socio-demographic variables were evaluated.Regression analysis was conducted to determine the association between respondent's ethnobotanical knowledge and age.
Quantitative ethnobotanical tools such as the informant consensus factor (ICF), use values (UV), fidelity level (FLs), relative popularity level (RPL), and rank-order priority (ROP) were also used for data analysis.

Use Value index (UVi)
The use value index (UVI) was calculated to find out the relative importance of medicinal plant species following [49].
where 'Ui' is the number of different uses mentioned by each informant i and 'N' is the total number of informants interviewed for the given plant species.

Informant consensus factor (ICF)
The informant consensus factor was calculated to investigate the degree of homogeneity among informants for the plants to be used in each ailment category [50].The ICF values vary from zero to one, with a high ICF achieved when one or a few plant species were reported to treat a certain condition by a large proportion of informants.
where 'Nur' is the number of use reports in each ailment category and 'Nt' is the total number of taxa used in each ailment category by all the informants.The result of this factor ranges from 0 to 1.A high value (close to 1) indicates that relatively few plant species are used by a large proportion of people, and a low value indicates that the informants disagree on the plant species used to treat a category of illness.

Fidelity level (FL)
The fidelity level is applied to determine which species are most frequently employed by the key informants to treat particular conditions.Higher FL values would indicate medicinal plants are more commonly used by the local communities, reveal the proportion of informants who reported using a specific plant species for the same purposes, and highlight the significance of the species for specific conditions.Following [51] and [52], all reported illnesses were arranged into major categories before determining the values using the formula [51].
where Ns is the number of informants that use a particular plant for a specific purpose and FCs is the total number of uses for the species.

Relative popularity level (RPL)
The relative popularity level (RPL) is a ratio of the number of important use reports mentioning a certain plant species to the number of interviewees mentioning that taxon in any use reports.RPL values vary from zero to one, with one representing total popularity and zero representing unpopularity [53].

Rank-order priority (ROP)
Relative popularity level (RPL) value multiplied by fidelity level (FL) value yielded the rank-order priority or accurate value of fidelity level (FL) (ROP = RPL * FL) [51].A high ROP value suggests that the plant has great potential.It might be beneficial for screening plants for bioactive compounds.

Socio-demographic characteristics and knowledge of traditional healers
According to interviews with key informants (Table 2), 189 medicinal plant species were collected and documented (Table 3).Among the 189 informants, the majority of participants were farmers, 155 (82%); others were merchants, 23 (12%); and students, 11 (6%).Male participants were outnumbered female participants (Table 2).About 70% of participants in this study were between the ages of 45 and 65.In comparison, those under 45 (young) and over 65 (elderly) accounted for 30% of the remaining population (Table 2).Illiterate and lower-grade informants were higher compared to high school attendees.Most interviewees were protestant religion followers, followed by Muslims and Orthodox Christians (Table 2).

Influences of socio-demographic variables on medicinal plant knowledge
The average number of medicinal plants reported by each socio-demographic variable was compared.It revealed that older traditional healers reported more medicinal plants (8) than others (Table 4 and Fig. 2A).Medicinal plants reported by followers of the Orthodox religion were higher (9) than Protestants and Muslims (Table 4 and Fig. 2D).The gender groups and education level categories reported a similar number of medicinal plants (7 each) (Table 4 and Fig. 2B).

The correlation between ethnobotanical knowledge and age
The regression analyses across ethnic groups showed that the respondent's age is positively correlated with his/her knowledge of identifying medicinal plants used; however, it showed a curvilinear relationship at the end (Fig. 3).Overall, the influence of age accounted for 37% of the variation in knowledge of medicinal plants across ethnic groups.

The most useful medicinal plant species of the studied ethnic groups
The use value index (UVI) is applied to measure various uses assigned to a specific plant species.Of the total 189 documented medicinal plants (Table 3), 78 medicinal plant species, which were claimed by three or more informants as remedies, were evaluated and revealed significant species use variation among the ethnic groups studied (Table 5).Meanwhile, 24 medicinal plant species scored the lowest use value; others were moderate to highest value (Table 5).

Informant consensus factor
Based on disease characteristics and treatment resemblances, fourteen (14) disease categories were identified from the 100 human ailments reported in the study areas (Table 3).Among these, the categories with the highest average ICF values among ethnic groups were circulatory system disorders (0.68), followed by febrile illness, reproductive organ disorders, and bad/evil spirit-related complications (0.66 each) across the studied ethnic groups (Table 6).In comparison, the highest plant use citation was noted for digestive system disorders, which are 100, 102, and 117 in the Sidama, Oromo, and Gedeo ethnic groups, respectively, followed by febrile illness (115, 94, and 87) in the Sidama, Oromo, and Gedeo ethnic groups (Table 6).

Fidelity level (FLs), relative popularity level (RPL), and rank-order priority (ROP)
The relative healing potential of medicinal plants is calculated for plants at least cited by three or more informants against particular ailments, and the FLs, RPL, and ROP values ranged from 50 to 100%, 0.5 to 1, and 24 to 100%, respectively (Table 7).Twenty-six plant species were identified as the most preferred plants (ROP > 50%) across ethnic groups (Table 7).Lactuca inermis Forssk.,                   in the Sidama ethnic group (Table 7).

Discussion
The medicinal plant resources and their associated indigenous and local ethnobotanical knowledge documented revealed time-honored ethnobotanical knowledge practices of the three ethnic groups studied (Table 3).The plant families Fabaceae, Asteraceae, Lamiaceae, and Poaceae were the most abundant, followed by Solanaceae, Rutaceae, and Euphorbiaceae.The hypothesis by [39][40][41][42] that the dominance of these families in disease treatment may be due to their aromatic properties and abundance of essential oil is supported by our record of a higher number of relevant plant species from Fabaceae, Asteraceae, and Lamiaceae ( In this study, Croton macrostachyus Hochst.ex Delile is reported as curing plants against deep sores and cancer-like ailments, eye infections, abrupt lightning, tetanus, lung infection, gonorrhea, dizziness, febrile illness, wounds, bad/evil spirit, diarrhea, jaundice, amoeba, glandular, giardia, abortion, intestinal worms, malaria, asthma, typhoid, skin infection, placental delay during birth, circumcision wound, stomachache, ear infection, allergy, and menstruation cycle disorder.Similarly, [5,52] reported the efficacy of the species against wounds, blood clotting, tinea versicolor, common wart, nasal congestion, indigestion, abdominal pain, bloating, intestinal parasite, retained placenta, general malaise (Michi), headache, jaundice, malaria, rabies, swelling, allergies, eye infection, and pyoderma in their ethnobotanical investigations in the south-central and southwestern parts of the country.In another study, in the southern parts of Ethiopia [8,10], the medicinal values of this species were revealed against toothache, swelling and forming deep openings, cold disease, gonorrhea, amoeboid, wounds, kidney infection, ringworm, stomachache, hepatitis, shivering, abnormal breathing, tuberculosis, gastritis, and goiter, and against jaundice in the northern parts of Ethiopia [13].Besides, [65] reported the efficacy of this species against typhoid, measles, and skin diseases in Kenya, [59] against headache in Uganda, and [66] against abdominal pain in Tanzania.
This study revealed ethnomedicinal values of Zingiber officinale Roscoe against asthma, blood pressure, passive sexual interest, common cold, tonsillitis, typhoid, headache, malaria, wounds, fever, cough, tung infection, goiter, constipation, febrile illness, amoeba, gastric diseases, and stomachache.Correspondingly, it was also reported against tonsillitis, abdominal pain, toothache, common cold, and coughing in other studies in the south-central and southwestern parts of Ethiopia [5,52].In addition, against eye disease in Hawassa zuria districts [8].Abroad [67] reported the significance of Zingiber officinale Roscoe against abdominal problems, laxative dyspepsia, dysentery and vomiting, coughs, bronchitis, asthma, and tuberculosis in Bangladesh; [68] reported against respiratory, digestive, and sexual disorders in India, and [64] reported against GIT disorders, respiratory disorders, CNS disorders, hematological disorders, endocrine disorders, rheumatic disorders, orthopedic disorders, immunological disorders, and antibacterial activities in Saudi Arabia.Albizia gummifera (J.F.Gmel.)C.A.Sm. is reported against deep sores and cancer-like ailments, goiter, toothache, dizziness, stomachache, jaundice, lung infection, amoeba, malaria, fire accident, skin infection, epilepsy, febrile illness, glandular, gonorrhea, swellings, fever, bad/evil spirit, cough, tuberculosis, menstruation cycle disorder, typhoid, and intestinal worms in this study.Correspondingly, [8] witnessed the significance of this species against swelling of the stomach and evil eye in Hawassa districts, southern Ethiopia, and [13] against febrile illness in northern Ethiopia.Other use reports indicated the novelty of this species against different ailments in the study areas.
Aloe macrocarpa Tod. is a novel for use against malaria, jaundice, typhoid, fever, deep sores and cancer-like ailment, lung infection, gonorrhea, pain relief, urinary organ infection, intestinal worms, wounds, stomachache, and diarrhea, because this is a new report and has not been reported before.However, [13] reported Aloe megalacantha Baker and Aloe camperi Schweinf.against dislocated bone, malaria, hemorrhoid, and eye disease; [14] reported Aloe weloensis Sebsebe against wounds, and malaria in northern Ethiopia, respectively; [28] reported Aloe gilbertii T. Reynolds ex Sebsebe and Brandham against malaria, intestinal parasites, tonsillitis, wounds, stomach pain, sudden disease, constipation, and eye problems in southern Ethiopia; and [21] reported Aloe otallensis Baker against blood clothing, wounds, and tuberculosis in southwestern Ethiopia.Calpurnia aurea (Aiton) Benth. is reported against lung infection, typhoid, intestinal worms, jaundice, bad/evil spirit, amoeba, headache, stomachache, toothache, fever, skin infection, wound, circumcision wound, febrile illness, deep sores and cancer-like ailment, swellings, glandular, and respiratory organ infection in our investigation.In addition, Eshete and Molla [10] reported this medicinal plant species against hepatitis, ear ache, and hypertension in the southern parts of the country.Likewise, [5] reported against toothache in south-central and in addition, [13] reported against eye diseases in the northern parts of the country.Gymnanthemum amygdalinum (Delile) Sch.Bip. is reported against amoeba, malaria, skin infection, stomachache, diarrhea, head skin infection, gonorrhea, rabies, febrile illness, intestinal worms, gastric diseases, lung infection, blood pressure, jaundice, vomiting, and typhoid.Correspondingly, [5,10,13,52] confirmed the efficacy of this species used against intestinal parasites, abdominal pain, malaria, gastritis, fibril illness, and diarrhea in their ethnobotanical investigations in different parts of the country.Likewise, [59] confirmed its great medicinal role against malaria, convulsions, and stomachache in Uganda.
Besides, several ethno-veterinary studies conducted elsewhere in the country identified numerous therapeutic plants against different livestock ailments, demonstrating  In general, comparison of our findings with other researchers' work conducted elsewhere in the country and abroad revealed that the documented medicinal plants have wide and novel uses in the study areas and demonstrated that people from different areas employ the same medicinal plants to treat the same or different types of human ailments.This revealed that the reported medicinal plants have therapeutic and pioneering uses in the research areas and beyond.This makes it easier for further efficacy evaluation and drug synthesis from the documented plants.Their pharmacological activity should be further confirmed for use at the local and worldwide levels.Most (71%) of the identified medicinal plants were harvested from the wild (Table 3).Conservation efforts specifically targeted at medicinal plants are still a challenge in the study areas and elsewhere in the country [8,9,25,47].The well-known natural forest of the Wondo Genet areas, Munessa-Shashemene natural and plantation forest, Adaba-Dodola forest, Bale Mountains National Park, wide agro-forestry practices, and local markets are potential sources for medicinal plants.We have also seen local farmers practicing their indigenous knowledge to protect some important medicinal plants in their home gardens (Table 3).Moreover, healers discussed the challenges of cultivating plant species outside their natural habitats, as well as the need to travel considerable distances for several hours to get the necessary therapeutic plants outside their villages.

The association between ethnobotanical knowledge and socio-demographic variables
The indigenous and local knowledge of medicinal plant uses of the three ethnic groups was not evenly distributed among respondents' age groups (Table 4 and Fig. 2A).The indigenous and local knowledge of medicinal plant use is still higher among the older (age groups > 44) than among the younger (< 45 years old) across ethnic groups.Likewise, Lulekal et al. [9],              at the end in this study.This does not mean that the knowledge of elderly people has declined, but their openness and willingness to disclose their knowledge to outsiders are very weak, and they were too secretive and conservative in our study areas.During our discussion with them, they informed us that if all knowledge of medicinal plants is freely shared, their effectiveness in curing the illness becomes weak, particularly for those in the age group above 64.They showed disinclination to participate in the study and were reluctant to disclose their knowledge.Thus, comparatively, the individuals (age ranges between 45 and 64) mentioned a greater number of ethnomedicinal plant species than elders (Table 4).As a result, informants' disparities in ethnobotanical knowledge sharing, particularly between age groups 55-64 (older) and above 64 (elder), may have had an unintended impact on the outcome of the study.Different ethnobotanical studies conducted elsewhere in the country also reported similar challenges.For instance, Mesfin et al. [20], in their ethnobotanical investigation in Amaro Woreda, southern Ethiopia, mentioned that the majority of participants were hesitant to disclose their knowledge of the medicinal value of the plants.They fear that their societal recognition and reputation, which they have earned due to their knowledge, will be lost, and hence they want to keep them secret.The traditional knowledge acquired from their ancestors is freely transferred within the family, preferably to the eldest son.Transfer of this knowledge to the outside world was deemed acceptable only based on substantial payment.In other studies in southern and central parts of the country, Eshete and Molla [10] and Woldeamanuel et al. [56] mentioned that most traditional healers consider traditional knowledge to be ancestral and divine, and thus, they are reluctant to disclose it to the outside world and keep it extremely secret because they think that the medicine would become ineffective if it were disseminated to others.Agize et al. [21], in their ethnobotanical investigation in southwestern Ethiopia, explained that aged informants were reluctant to disclose their ethnobotanical knowledge early as compared to other age groups, and kept it up to their last life span.Overall, this study revealed a decline in indigenous and local ethnobotanical knowledge among the younger generation across the studied ethnic groups and called for an effort to repair the observed generation gap via ongoing professional support and training of local communities to maintain traditional knowledge and practices through systematic recording.Lack of interest in traditional knowledge among young generations coupled with poor knowledgesharing mechanisms (by word of mouth, secrecy, and only among family members) and weak policy support from concerned bodies are reported challenges for the rapid loss of indigenous and local ethnobotanical knowledge and a threat to the future potential of the country [9,10,59,66,67].Besides, informants claimed that in recent decades, young healers had traveled to urban areas in other conditions in pursuit of work because of a lack of support from the government and a low income from traditional medication.This is important since such activities hurt the sustainability of local ethnomedicinal knowledge across generations.
Gender is another test to determine the distribution of ethnobotanical knowledge across ethnic groups.
However, the difference was not statistically significant (Table 4 and Fig. 2B).Similar results were reported by [9,10,[12][13][14]66] elsewhere in the country and abroad in Nepal and Tunisia, where gender did not influence ethnomedicine claims.Thus, it was indicated that both men and women are knowledgeable about the use of traditional plant remedies, despite the relative dominance of medicinal plant traditions by men in the country, which could relate to the flow of information along the male line in the country [9,14,67].Earlier studies conducted elsewhere in Ethiopia and Ecuador found that traditional medicine practitioners had nearly comparable ethnobotanical knowledge practices between the gender groups [9,45].In contrast, [4,8,59,65,69] elsewhere in the country and abroad in Mexico reported that significant differences were found in ethnobotanical knowledge between male and female practitioners.
Even though illiterate and lower-grade informants of the studied peri-urban districts reported more medicinal plants than higher-grade informants (Table 4 and Fig. 2C), the difference was not statistically significant.This finding revealed that all interviewed informants were knowledgeable about using traditional plant remedies regardless of their education levels, showing that education is not a factor in influencing their local knowledge of plant utilization.A similar result was reported by [12,59] in Mexico and Nepal.In contrast, [8-10, 13, 66, 69, 70] mentioned education has effect on the health-seeking behavior of the local communities in different parts of the country and abroad in Tunisia.Our findings also showed that religion has no effect on the health-seeking behavior of the local communities; despite the fact that the majority of the people in the research areas are Protestants and Muslim religion followers, they still preferred traditional plant medicines (Table 4 and Fig. 2D).This implies that most spiritual beliefs encourage the use of therapeutic plants in the study areas.Thus, in this community, we realized that religion is not a limiting factor that affects the distribution of the local ethnobotanical knowledge system.Correspondingly, other studies conducted in the southeastern parts of Ethiopia [4,71] also indicated that informants believed religion encouraged the use of traditional plant medicine.Contrary to this, a study by [85] revealed that religion is a limiting factor influencing the distribution of medicinal plant knowledge in India.

Useful plants and their use values
The widespread use of plants for health treatment demonstrates an essential element of the culture [15] and is used to determine the relative significance of medicinal plants in the local communities [49].Accordingly, Croton macrostachyus Hochst.ex Delile, Zingiber officinale Roscoe, Albizia gummifera C.A.Sm., and Aloe macrocarpa Tod. had scored the highest use value across the studied ethnic groups as a curative plant against different human ailments (Table 5).Aspects of these findings are consistent with those of other researchers [8,10,14,51,54,55,72,73] who conducted ethnobotanical surveys in different parts of Ethiopia, South Africa, Bangladesh, India, and Saudi Arabia.They revealed that Croton macrostachyus Hochst.exDelile and Zingiber officinale Roscoe had high use values against different ailments, and the in vitro investigations of [86][87][88][89] validated their efficacy on antimicrobial activities.Albizia gummifera C.A.Sm.has a significant use value against different human ailments in the studied communities, and the in vitro investigations of [90] confirmed the efficacy of this medicinal plant species antimicrobial activities in Cameroon.Aloe macrocarpa Tod. has a significant use value against different human ailments, and the in vitro investigations of [91] validated the efficacy of this  medicinal plant species antimicrobial activities.Gymnanthemum amygdalinum (Delile) Sch.Bip., Calpurnia aurea (Aiton) Benth, and Allium sativum L. were also curative plants by all studied ethnic groups with varied use values (Table 5), and the in vitro investigations of [92][93][94][95] validated their antimicrobial activities, respectively.
In general, among the evaluated 78 important medicinal plant species, several studies conducted in Ethiopia and abroad reported different amounts of therapeutic plant use value against human ailments, which confirmed the efficacy of several traditional medicinal plants documented in this study.For instance, Chekole [14] [68], and Al-robai et al. [64] revealed 9, 7, 8, 6, and 14 significant medicinal plants in Pakistan, Bangladesh, India, and Saudi Arabia.Besides, it was also confirmed by Eshete and Molla [10] that repeatedly used plants are more likely to be biologically active and indicate the popularity of the local medicinal flora in the local culture.Therefore, these species should be prioritized for conservation.Their preferred uses may place their populations under threat due to overharvesting.

The general understanding among informants
Consensus analysis is a critical tool for establishing a comparative evaluation of the level of informant's agreement on the use of medicinal plants [50].Beyond that, it would provide dependability for every claim supported by reliable facts in ethnobotanical investigations [98].As a result, the majority of the clusters generated in this study confirmed the unique and shared knowledge of each ethnic group on similar or different plant species against a variety of ailments and the diffusion of information and cultural linkage (Table 6).Most of the clusters had an informant consensus value greater than 50, indicating that they might all be evaluated for validation in support of their traditional use.These demonstrate a high level of agreement among the informants regarding the use of specific plants to treat the similar disorder.Particularly, the four use categories (Circulatory system disorders, febrile illness, reproductive organ disorders, and Bad/evil spirit) scored high ICF values across the studied ethnic groups.Different studies conducted elsewhere in the country also reported high ICF value for the same illness categories [8,10,13,14,52].Lulekal et al. [9] explained that the high informant consensus values obtained indicate reasonably high reliability of informants on the use of traditional medicinal plants, which are thought to have better potency and contain more biologically active ingredients in disease treatment.
In this study, six medicinal plant species gained common consensus among the studied ethnic groups against febrile illnesses, glandular problems, reproductive organ illnesses, respiratory organ illnesses, and bad or evil spirit complication categories (Table 6).Allium sativum L. obtained a common consensus against typhoid and common cold; Croton macrostachyus Hochst.ex Delile against dizziness and gonorrhea; Gymnanthemum amygdalinum (Delile) Sch.Bip.against malaria; Moringa stenopetala (Baker f.) Cufod.against glad-related complications; Ruta chalepensis L. against gonorrhea; and Withania somnifera (L.) Dunal against bad or evil spirits.Ethnobotanical studies conducted elsewhere in the country also revealed similar kinds of findings.For instance, [5] reported the efficacy of Allium sativum L. against cold and febrile illness (general malaise), Croton macrostachyus Hochst.ex Delile against febrile illness (general malaise), Gymnanthemum amygdalinum (Delile) Sch.Bip. against malaria, and Withania somnifera (L.) Dunal against bad or evil spirits.In another study, [14] revealed the significance of Croton macrostachyus Hochst.ex Delile against gonorrhea and febrile illnesses and Withania somnifera (L.) Dunal against bad or evil spirit complications.In the southern parts of the country, Tefera and Kim [8] also reported the medicinal value of Ruta chalepensis L. against gonorrhea.Again, in southern and southwestern parts of Ethiopia, [42,52] confirmed the efficacy of Allium sativum L. against common cold.Similarly, [10,52] reported the ethnomedicinal effectiveness of Croton macrostachyus Hochst.ex Delile against gonorrhea.Also [10,42] reported the significance of Withania somnifera (L.) Dunal against bad or evil spirits in the southern parts of the country.However, Moringa stenopetala (Baker f.) Cufod.was found to be a novel finding in the study areas against gland-related problems.Therefore, further consideration and studies are needed to evaluate the information about the phytochemical and pharmacological potentials of the recorded ethnomedicinal plants for wider utilization.
Contrary to this, different consensuses were also noted among the three ethnic groups on some medicinal plants against circulatory system illness categories (snake venom).Those are Gymnanthemum auriculiferum (Hiern) Isawumi, which got the highest consensus within the Gedeo ethnic group against snake venom, whereas Solanum incanum L. and Searsia natalensis (Bernh.ex Krauss) F.A.Barkley were within the Oromo and Sidama ethnic groups, respectively, (Table 6).Besides, as compared to the Oromo ethnic group, the Sidama ethnic group showed great consensus to treat mental (rabies) disorders using Antiaris toxicaria (J.F.Gmel.)Lesch., and Justicia schimperiana (Hochst.ex Nees) T.Anderson.The Gedeo ethnic group informant has shown a unique agreement on the abruptness lightning complications using Croton macrostachyus Hochst.ex Delile and Ensete ventricosum (Welw.)Cheesman and against musculoskeletal illness using Calpurnia aurea (Aiton) Benth.and Croton macrostachyus Hochst.ex Delile.Informant consensus values near or zero indicate low informant agreement, which could be attributed to the community's use of different species for the same ailments [36,45] (Table 6).Several studies conducted elsewhere also confirmed that conditions such as circulatory system disorders, gastrointestinal diseases, respiratory system disorders, Evil/bad spirits, and febrile illness were disease categories recognized as being efficiently treated by traditional plant medicine [8,9,39,58,60,61].

Species consensus of informants
The fidelity level (FLs), relative popularity level (RPL), and rank-order priority (ROP) values are considered to determine for which illness a particular plant species is more effective in the study areas.In general, a rank-order priority (ROP) of 100% for a specific plant species indicates that all of the use reports mentioned were the same and an excellent choice for treating particular ailments [5,62,63].In contrast, the low fidelity levels and low rank-order priority indicate the plant species will be employed for diverse purposes, according to [59].The reported highest fidelity level values for Lactuca inermis Forssk., Moringa stenopetala (Baker f.) Cufod., Withania somnifera (L.) Dunal., Allium sativum L., Citrus limon (L.) Osbeck, Ricinus communis L., Schinus molle L., Antiaris toxicaria (J.F.Gmel.)Lesch., Brucea antidysenterica J.F.Mill., Echinops kebericho Mesfin, Ocimum jamesii Sebald, Afrocarpus falcatus (Thunb.)C.N.Page and Searsia natalensis (Bernh.ex Krauss) F.A.Barkley could be considered as evidence of the high healing potential of these plants against the corresponding diseases in the study areas (Table 7).In contrast, Ricinus communis L., and Allium sativum L. scored the lowest points against tonsillitis and fever, respectively.The revealed results confirmed that ethnic groups have diverse ethnobotanical knowledge of specific plants and disease conditions.
Different ethnobotanical investigations conducted elsewhere in the country and abroad revealed considerable evidence about the therapeutic potentials of some of the selected medicinal plants in the study areas.Consistently, Tefera and Kim [8] revealed the medicinal potential of Moringa stenopetala (Baker f.) Cufod.against cardiovascular diseases and [5,10,14] reported the efficacy of Withania somnifera (L.) Dunal.against bad or evil spirits in different parts of the country.Similarly, another study [5] confirmed the effectiveness of Allium sativum L. against common cold in the south-central parts of the country.In addition to our findings, [5,9] reported the ethnomedicinal effectiveness of Echinops kebericho Mesfin against evil spirits, general malaise, abdominal pain, diarrhea, and amoebiasis in the central and south-central parts of the country.In other ethnobotanical investigations, [5,9,84] again elucidated the ethnomedicinal role of Allium sativum L. against skin diseases, malaria, toothache, general malaise, and tuberculosis.In Ethiopia and abroad, [5,13,14,85] revealed the ethnomedicinal effectiveness of Withania somnifera (L.) Dunal.against febrile illnesses, general malaise, liver disorders, kidney pain, and blood purification.Thus, the use of the same plant species for related or dissimilar ethnomedicinal applications in different countries is a reliable indication of the recorded plant species' bioactivity potential, and the presence of a certain ailment in the area and the widespread use of traditional plant medicine [9,64].The findings will be used in future research to confirm the bioactivity of certain medicinal plants employed by traditional healers and boost their acceptance in broader healthcare systems in the country and abroad.

Use diversity and cultural roles of some medicinal plants
The medicinal plant species documented in this study are also cited for multiple local uses besides their medicinal role (Table 3).All medicinal plant species, particularly trees, shrubs, and herbs, were believed to be beneficial to the environment.Maintaining ecosystems through erosion regulation, soil enhancement, fodder and shelter for wild animals, and climate regulation were among the major roles.The mentioned environmental services were justified in the sense that each plant species has a role in supporting balanced biophysical systems.Based on the informants in our study, of the 189 identified medicinal plant species, 30 were reported for additional uses as food and 40 as livestock fodder, indicating their supplemental role in supporting the livestock and livelihood wealth of the study areas (Table 3).Additionally, more than 100 medical plant species were utilized as fuel (charcoal and firewood), whereas 16 were noted for timber production, which is the primary source of income for the majority of local communities.About 52 medicinal plant species were also employed for local construction uses, including 22 for social services such as cultural gathering under shade of those trees to resolve local conflict (Table 3).Around ten medicinal plant species were also identified as spices to food in the study areas.These findings demonstrated that the breadth of indigenous and local knowledge practices among local people in using plant resources for different purposes.On the other hand, the medicinal use values of plant species employed across different use categories demonstrated the relative importance of various plant species in people's everyday lives.Different studies conducted elsewhere in the countries also explained the diverse potentials of the documented medicinal plant species beyond their medicinal roles.For instance, Gurebiyaw et al. [102] mentioned the ecological significance of Albizia gummifera (J.F.Gmel.)C.A.Sm., Cordia africana Lam., and Croton macrostachyus Hochst.ex Delile on soil fertility enhancement.Negash [103] explained the promising options of Afrocarpus falcatus (Thunb.)C.N.Page, Cordia africana Lam., Croton macrostachyus Hochst.ex Delile, Ekebergia capensis Sparrm., Millettia ferruginea (Hochst.)Hochst.ex Baker, and Vachellia seyal (Delile) P.J.H.Hurter in maintaining soil fertility, soil regeneration and water conservation, provision of shade or shelter, as well as for windbreak.
In the study areas, it was also noted that farmers valued very much certain medicinal plant species for traditional farming tools and local buildings.Afrocarpus falcatus (Thunb.)C.N.Page and Olea europaea subsp.cuspidata (Wall.& G.Don) Cif. were preferred plant species for making three traditional Ethiopian farming tools, "Wanjoo, Gindii and Maneqoo" in the Oromo ethnic group and "Mofaara, Qanbaraa, and Maneqoo" in the Gedeo and Sidama ethnic groups, which are commonly drawn by a pair of oxen.Additionally, the wood and leaves of Olea europaea subsp.cuspidata (Wall.& G.Don) Cif. are burned to produce a characteristic smoke, which serves as a good flavor for fermenting milk and making local alcohol (e.g., locally known as Tella and Tej).Another intriguing aspect is that the Sidama ethnic group tendency for traditional house construction using bamboo species and Juniperus procera Hochst.Ex Endl.throughout the generations.The Sidama ethnic group is located in the southern Ethiopia and has unique expertise in how to create a stunning beehive-shaped traditional house entirely built of homogeneous woven bamboo.Juniperus procera Hochst.ex Endl.tree poles are used in the foundation because local communities think this species has natural resistance to microbes and termites and is longlived.Dainty strands of bamboo are set around the edge of the house.The walls are made by parting the bamboo into more modest strips.The interior walls include two designs locally known as "Hilo and Himbiro".

Public health and roles of medicinal plants
Traditional medicine and medicinal plants have continued to play an essential role in the public healthcare system, both in the study areas and in elsewhere in the country.Because it is understandable that, in Ethiopia, almost 80% of the population uses traditional medicine, which is primarily based on medicinal plants [104], and more than 95% of folk medicine decoctions are derived from medicinal plants [105].According to Lulekal et al. [9], the documented medicinal plants with high informant consensus (IC) and rank-order priority (ROP) values have promising potential against different pathogens and play a great role in maintaining the general public health of local communities and beyond.For instance, the authors reported high informant consensus and rankorder priority values for Afrocarpus falcatus (Thunb.)C.N.Page, Allium sativum L., Croton macrostachyus Hochst.ex Delile, Echinops kebericho Mesfin, Gymnanthemum amygdalinum (Delile) Sch.Bip., Moringa stenopetala (Baker f.) Cufod., Ruta chalepensis L., Withania somnifera (L.) Dunal, Ricinus communis L., and Zingiber officinale Roscoe (Tables 6 and 7) are indications for their role in maintaining the community's health against different communicable and non-communicable diseases in the study areas.Besides, in vitro, investigations conducted by [79,83,85,[97][98][99][100][101] confirmed their effectiveness against many disease-causing pathogens in the country and abroad.

Conclusion
The medicinal plant resources in the studied ruralurban interface areas are considerably high.The associated knowledge of the local people is deep-rooted in the time-honored practices of traditional plant medicine, which depended heavily on medicinal plant species to cure different ailments.The study revealed a generational gap across ethnic groups in medicinal plant knowledge acquisition.Thus, older generations have continued to play a role as reservoirs for indigenous and local ethnobotanical knowledge practices.The use values of the most important medicinal plant species were evaluated and revealed considerable variability among the ethnic groups studied.Croton macrostachyus Hochst.ex Delile, Albizia gummifera (J.F.Gmel.)C.A.Sm., Zingiber officinale Roscoe, Aloe macrocarpa Tod., Gymnanthemum amygdalinum (Delile) Sch.Bip., Ruta chalepensis L., and Calpurnia aurea (Aiton) Benth.were noted species with high use value.Knowledge dissemination among informants was highest in the categories of circulatory system disorders, febrile illnesses, and reproductive organ complications across ethnic groups.The curative potential of some medicinal plants was evaluated and revealed significant fidelity values across ethnic groups.Lactuca inermis Forssk., Moringa stenopetala (Baker f.) Cufod., Withania somnifera (L.), Allium sativum L., Citrus limon (L.) Osbeck, Ricinus communis L., Schinus molle L., Antiaris toxicaria (J.F.Gmel.)Lesch., Brucea antidysenterica J.F.Mill., Echinops kebericho Mesfin, Ocimum jamesii Sebald, Afrocarpus falcatus (Thunb.)C.N.Page, and Searsia natalensis (Bernh.ex Krauss) F.A.Barkley are among the top ones.Thus, the revealed results will provide relevant information for further research focusing on investigating the bioactive compounds of some selected curative plants, sustaining indigenous and local ethnobotanical knowledge, and the associated most important medicinal flora.Besides, providing professional support to manage the ongoing dynamics and maintain the vast erosion of indigenous and local knowledge is vital.

Fig. 1
Fig. 1 Map of the study sites Dilla, Shashemene, and Hawassa peri-urban areas

Fig. 4
Fig. 4 Correlation between male respondent's knowledge of medicinal plant citation and age

Fig. 5
Fig. 5 Correlation between female respondent's knowledge of medicinal plant citation and age

Table 2
Demographic details of the participants from periurban areas of Dilla, Hawassa, and Shashemene

Table 4
Comparison of the number of medicinal plants cited by different socio-demographic parameters across ethnic groups (Gedeo, Oromo, and Sidama) Significance association (p < 0.05) between the averages of paired parameters *Fig. 2 Average number of medicinal plants reported by each socio-demographic variables

Table 5
The use value index of the most important medicinal plant species among ethnic groups 3,4,5)of knowledge distribution were also witnessed abroad.Beltrán-Rodríguez et al.[77], Sharma et al.[78], Wiryono et al.[63], Amjad et al.[79], Pathy et al.[80], and Khakurel et al.[81]in Mexico, Himalaya (South Asia), Indonesia, Pakistan, DR Congo, and than the younger informants.The regression analysis also confirmed that the respondent's age was positively correlated with his or her ability to recognize and use ethnomedicinal plants across ethnic groups (Figs.3,4,5); however, it showed a slight curvilinear relationship N.B: Broken lines indicate the absence of a citation for the indicated species in the study area

Table 6 A
detailed informant consensus factor of the three ethnic groups (Sidama (S), Gedeo (G), and Oromo (O))

Table 7
The most curative medicinal plant species with their FL, RPL, and ROP values among ethnic groups