UMYU Scientifica

A periodical of the Faculty of Natural and Applied Sciences, UMYU, Katsina

ISSN: 2955 – 1145 (print); 2955 – 1153 (online)

ORIGINAL RESEARCH ARTICLE

Species Diversity, Conservation Status, and Ethnobotanical Significance of Medicinal Root Plants in Katsina State, Nigeria

Ibrahim Kabir*, Sulaiman Sani Kankara, Sani Mohammed Gidado, Wagini N.H

Department of Biological Sciences; Faculry of Natural and Applied Sciences, Umaru Musa Yar'adua University, PMB 2218 Katsina, Katsina State, Nigeria

*Correspondence Author's Email: Ibrahim Kabir [email protected]

Abstract

Medicinal root plants are central to traditional healthcare systems, yet information on their diversity, ethnobotanical uses, and conservation status in northern Nigeria remains limited. This study assessed species richness, evenness, ethnobotanical significance, and conservation status of medicinal root plants across six Local Government Areas (LGAs) in Katsina State, Nigeria. A mixed-methods approach was adopted, integrating ethnobotanical surveys of 240 respondents with ecological sampling from 150 quadrats. Plant diversity was evaluated using the Shannon–Wiener diversity index (H’) and Equitability (EH). Ethnomedicinal uses and conservation status were documented using standard criteria. Nineteen plant families were recorded, with Fabaceae being the most dominant (26.9%). Site A exhibited the highest species diversity (H’ = 3.7) and evenness (EH = 0.95). Medicinal roots were predominantly used for the treatment of malaria and gastrointestinal disorders. Most species were classified as Least Concern (LC), including Adansonia digitata and Parkia biglobosa. However, threatened taxa were identified, such as Khaya senegalensis (Vulnerable), Combretum glutinosum and Sclerocarya birrea (Endangered), and Borreria stachydea (Data Deficient). Rare plant families, notably Moraceae, were sparsely represented (0.17%). The findings highlight spatial variation in medicinal plant diversity and emphasize the continued reliance on root-based remedies in Katsina State. The presence of threatened and poorly documented species underscores the need for targeted conservation and sustainable harvesting strategies. This study contributes to global ethnomedicinal documentation efforts and supports earlier findings on medicinal plant use in the region.

Keywords: Ethnobotany, medicinal roots, biodiversity, distribution, Shannon index, Nigeria.

INTRODUCTION

Medicinal plants form the backbone of traditional healthcare in northern Nigeria, where plant roots are particularly valued for their therapeutic properties. Recent estimates suggest 70-80% of Katsina State's rural population depends on herbal remedies for primary healthcare needs (Kankara et al., 2020). Roots are frequently used due to their high concentrations of bioactive compounds, employed in treatments ranging from malaria to digestive disorders (Abdullahi et al., 2021). However, systematic documentation of these medicinal root species particularly their ecological distribution remains limited in Nigeria's savanna regions.

Katsina State's unique vegetation zone, transitional between Sudanian and Sahelian ecologies, hosts a distinct assemblage of medicinal flora. While ethnobotanical studies like those of (Kankara et al., 2020) have catalogued plant uses in the region, few have examined how species richness and evenness vary across different local government areas. This gap hinders understanding of ecological patterns that could inform sustainable harvesting practices and clarify plant community relationships in semi-arid environments.

This study bridges this knowledge gap by analyzing the diversity and distribution of medicinal root plants across six Katsina LGAs. Using quadrant-based ecological sampling and ethnobotanical surveys, we quantify species richness (Shannon-Weiner Index) and (Equitability Index) while documenting indigenous use cases. Our approach builds on earlier work but introduces rigorous spatial analysis of medicinal root distributions, offering new insights into their ecology in northern Nigeria's savannas.

METHODOLOGY

Study Area

Figure 1; Katsina State Map showing the Sampled Local Government Areas

Katsina State (Figure 1) (12°5'N, 7°6'E) spans 23,938 km² of Sudanian savanna (Rumah et al., 2010). Six LGAs were sampled:

- Katsina Central: Batagarawa, Kaita (Site A)

- Katsina North: Dutsi, Mani (Site B)

- Katsina South: Malumfashi, Dandume. (Site C).

Fieldwork combined ecological surveys with ethnobotanical interviews to document both plant distributions and traditional knowledge. For the ecological data collection, we used a quadrant sampling approach of Stohlgren et al. (1994) with plots (10m x 10m each), spaced 20 meters apart to ensure independent sampling (Figure 2). Within each plot, all plants with medicinal roots were counted, identified, and recorded. Local names and uses of these plants were gathered through structured interviews with 240 community members (40 respondents per LGA), including traditional healers, farmers, and elders knowledgeable about plant medicine.

Plant identification was done first through local names provided by respondents, then cross-checked with available botanical resources (Nicolson et al., 2023). To analyze the data, we calculated species diversity using the Shannon-Weiner Index (H') and evenness distribution using the Equitability Index (EH). These indices helped determine how many different species were present (richness) and how evenly they were spread across the sites (evenness). The ethnobotanical data were organised to show which plant families were most commonly used and their medicinal applications. This mixed approach allowed us to compare ecological patterns with traditional use, providing a full picture of medicinal root plants in the region.

Statistical analysis

Figure 2: Quadrants employed in the study Area.

The ethnobotanical data collected were organized in a Microsoft Excel spreadsheet.

The information of the respondents was evaluated using simple percentage.

The shannon diversity index or shannon weiner index (H’) and Shannon equitability index (EH) was employed to assess the diversity richness and evenness of species with medicinal root usage within the study area. The formula for calculating the (H’) is:

H= Σpi * ln(pi)

Where:

Σ: A Greek symbol that means “sum”

ln: Natural log

pi: The proportion of the entire community made up of species i

The higher the value of H, the higher the diversity of species in a particular community. The lower the value of H, the lower the diversity.

The value for H ranges between 1.5 and 4.5. The lower values indicate more diversity, while the higher values indicate less diversity.

Note: The value of the Shannon-Weaver diversity index may be higher than 1.5 to 3.5 and only rarely exceeds 4.5 (Shannon et al., 1949).

The formula for calculating the Shannon equitability index (EH) is:

EH = H / ln(N)

The value for EH ranges between 0 and 1 where 1 indicates complete evenness.

A higher index value indicates greater diversity with more evenly distributed species and lower values indicates less diversity.

RESULTS

Figure 3: Shannon-Weaver Index

The Shannon-Weaver Index suggests that higher values indicate higher diversity. This shows that, site A with a 3.7 index has the highest diversity among the three sites. Site C follows with a slightly higher index of 1.8, and site B has the lowest diversity at 1.6 as indicated in Figure 3 above. These values imply that site A has a more diverse ecological community compared to sites B and C, where higher Shannon-Weaver Index values indicate high diversity.

Figure 4: Shannon equitability index

Species evenness was observed to be the highest at Site A (EH = 0.95), as shown in Figure 4, suggesting a relatively balanced distribution of individuals across species. Such elevated evenness is generally correlated with moderate or low-intensity disturbances, which can mitigate competitive exclusion while preventing a few species from dominating the community. Conversely, Site C (EH = 0.46) and Site B (EH = 0.42) displayed significantly lower evenness, indicating community dominance by a restricted number of species. This trend is often associated with habitat alteration and human-induced disturbances, which modify resource availability and favour disturbance-tolerant or opportunistic species, consequently diminishing overall evenness (Bello et al., 2020).

These patterns reveal an important ecological trade-off: human activity either reduces total species numbers (lowering H') or creates uneven distributions (lowering EH), with only pristine areas like Site C maintaining both measures at moderate levels (Adedoja et al., 2023).

The exceptional dominance of Fabaceae (26.9%) and rarity of Moraceae (0.17%) further confirm how anthropogenic pressures reshape medicinal plant communities (Kankara et al., 2015).

Figure 5: Family Distribution of Plants

DISCUSSION

The Shannon–Wiener diversity index (Figure 3) indicated significant spatial variation in the structure of plant communities across the three sites. Site A exhibited the highest species diversity (H′ = 3.7), signifying a community that is both structurally complex and rich in species, which is characteristic of relatively stable Sudan Savannah ecosystems. In contrast, Site C demonstrated moderate diversity (H′ = 1.6), while Site B recorded the lowest diversity (H′ = 1.8), suggesting increasingly simplified plant assemblages. These variations imply a gradient of ecological conditions, likely influenced by differing climatic constraints and levels of anthropogenic disturbance.

Species evenness displayed a similar pattern. Site A achieved very high evenness (EH = 0.95), indicating a fair distribution of individuals across species. In contrast, Sites C (EH = 0.46) and B (EH = 0.42) showed diminished evenness, reflecting the dominance of a limited number of species and a reduction in community balance. Such patterns of dominance are typical of disturbed habitats where competitive or disturbance-tolerant species thrive.

The elevated diversity noted at Site A corresponds with established Shannon index values for Sudan Savannah ecosystems, which generally range from H′ = 3.5 to 4.2 (Oke et al., 2007). This supports the notion that Site A maintains numerous structural characteristics of relatively intact savannah vegetation.

The diversity metrics observed at Site C are similar to those documented in Guinea Savannah regions in Nigeria, where moderate diversity has been linked to intermediate rainfall and mixed land-use practices (Abdullahi et al., 2020). Likewise, the lower diversity at Site B aligns with research from arid and semi-arid regions, including Jigawa State, where severe climatic conditions and limited moisture availability restrict species richness (Mortimore et al., 2001).

The remarkably high evenness recorded at Site A stands in stark contrast to previous research conducted in comparable Sudan Savannah ecosystems, which indicated lower evenness values (EH ≈ 0.55) attributed to selective harvesting and the dominance of a limited number of resilient species (Oke et al., 2007). The diminished evenness observed at Sites B and C aligns with findings by Bello et al. (2020), who associated decreasing evenness with habitat alteration and human-induced pressures.

The notably high evenness at Site A may be accounted for by regulated or low-intensity harvesting practices, which can mitigate competitive exclusion without disproportionately benefiting a narrow range of species. In contrast to intensive extraction methods, moderate disturbances may suppress dominant species, thereby allowing less competitive taxa to thrive, resulting in a more equitable distribution of individuals.

Conversely, the low diversity and evenness at Site B can be primarily linked to climatic stressors, such as insufficient rainfall, elevated temperatures, and inadequate soil moisture, which hinder plant establishment and promote drought-resistant species. Although Site C is less affected by climatic factors, it seems to be influenced by land-use changes and habitat alterations, which have led to a decline in evenness despite moderate levels of diversity.

The significant presence of Fabaceae (26.9%), as shown in Table 1 and Figure 5, further corroborates the impact of human disturbances, as members of this family are particularly well-suited to thrive in stressful conditions, nitrogen-deficient soils, and environments subjected to repeated harvesting. In contrast, the scarcity of Moraceae (0.17%), a family typically associated with mature or less disturbed ecosystems, underscores the selective extraction of ecologically and medicinally important species amid escalating human pressures (Kankara et al., 2015).

In summary, the results reveal a significant ecological trade-off: human activities can lead to a decrease in species richness (lower H′), disrupt the balance of species (lower EH), or both, contingent upon the intensity of the disturbance and the environmental context. Although systems that experience moderate disturbances may preserve a reasonable level of diversity or evenness, prolonged anthropogenic pressure ultimately alters community composition. Only sites that are relatively less disturbed or ecologically buffered are able to sustain both diversity and evenness at moderate to high levels (Adedoja et al., 2023).

Table 1: Categories of Ailments treated with the documented plants species Frequency of citation, Relative frequency of citation, Fidelity level, Specie Use value, and Vulnerability index.

CONCLUSION

This study provides important insights into the diversity and traditional uses of medicinal root plants in Katsina State, Nigeria. Our findings reveal that Fabaceae species dominate the medicinal flora (26.9%), consistent with previous regional studies, while rare families like Moraceae (0.17%) require urgent conservation attention. The ecological analysis showed significant variation in species distribution, with undisturbed sites exhibiting higher diversity (H'=3.7) and farmed areas showing higher evenness (EH=0.9), highlighting how human activities influence plant communities. The ethnobotanical data confirmed the continued reliance on root medicines for treating common ailments, preserving valuable traditional knowledge. These results emphasize the need for community-based conservation strategies that protect both biological diversity and cultural heritage. Future research should investigate sustainable harvesting methods and monitor long-term changes in these medicinal plant populations.

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