Biodiversity and Ecosystem Management

Genetic Diversity and Ecology of Lepidopteran StemBorers in Rwanda

2026-10-19T07:37:52Z

Genetic Diversity and Ecology of Lepidopteran StemBorers in Rwanda Ntirenganya Elie This thesis examines ecology, host interactions, genetic diversity, and evolutionary patterns of Lepidopteran stemborers in the agroecological landscapes of Rwanda. It emphasizes on their impacts on cereal and sugarcane stemborers and wild species, their ecological dependence on wild host vegetation, and their responses to climate and landscape changes. Recent studies reported that stemborers have started to shift from their natural habitats and attacking new host plants that were not used to be hosts before. The research was motivated by high speed increasing landuse change by agriculture intensification and urbanization in changing climate that modify natural habitats of stemborers. In addition to this curiosity, less information on stemborer population in Rwanda is available and do not clearly show how environmental gradients, vegetation mosaics, and and these changes reshape stemborers community structure and genetic composition. The field-based ecological results revealed a substantial species richness, host-plant diversity, and habitat-driven distribution patterns. Surveys yielded 18 stemborer genera recorded from 56 host plant species. The most interesting points is that the highest abundance and diversity of stemborers were concentrated in urban and peri-urban wetlands of Kigali City, highlighting the ecological role of human-modified habitats. Poaceae hosts accounted for over 60% of all larvae collected, and common species exchangeable from wild to crop vis versa for survival, where Napier grass (Pennisetum purpureum) served as the primary refugia during dry. The specific survey conducted in sugarcane plantation shows that sugarcane support mass population of Eldana Saccharina Walker, 1865. The population vary by season and first population start in May, a month of transition between heavy rain season (March-early May) to dry late May to August. The population reached peak in August. The infestation severity varied across sugarcane varieties with the most affected was green and red sugarcane varieties that whitepowdery sugar industrial variety. Sanitation practices of old-leave removal in sugarcane plantation have shown a critical effect in reducing population dynamics of sugarcane stemborers, suggesting this practice as pesticides-free method to control stemborers in sugarcane plantation system. For molecular ecology of key stemborer species through genetic analyses of Sesamia nonagrioides (Lefèbvre, 1827) and E. saccharina, Ethiopian population as earliest studied populations in Africa xxii were used as model to understand Rwandan population’s genetic diversity and diververgence. Mitochondrial COI sequencing showed high genetic diversity in selected model species that were associated with wetland vegetations and these from maize and sugarcane. Among these species, wetland associated species and these associated with crops were standing alone as connected sisters that share common ancester but evolved differently in different time. There were no shared haplotypes between population of Rwanda and model population from Ethiopia. The results suggest that over time, landscape history, wetland degradation, climate gradients, and agricultural expansion are shaping contemporary genetic differentiation, and concludes that region-specific biological control strategies, improved surveillance, and cross-habitat management are essential, as genetically distinct populations may respond differently to control measures. Observed variations in the distribution of pest and non-pest stemborer species, together with differences in genetic structure among key model species, indicate that no single management strategy is suitable across landscapes and that continued habitat fragmentation will likely destabilize ecosystems, leading to host range expansion or local extinctions. These patterns reflect broader environmental change, where habitat fragmentation at the local scale reduces connectivity and gene flow, while climate change at regional and global scales drives shifts in species distribution, community reorganization, and biodiversity loss. Together, these processes highlight the need for multi-scale, integrative research to understand stemborers species responses to these combined effects and to support the development of context-specific, climate-smart integrated pest management strategies for sustainable agriculture. 213

Genetic Diversity and Ecology of Lepidopteran StemBorers in Rwanda

2026-10-16T07:46:10Z

Genetic Diversity and Ecology of Lepidopteran StemBorers in Rwanda Ntirenganya Elie This thesis examines ecology, host interactions, genetic diversity, and evolutionary patterns of Lepidopteran stemborers in the agroecological landscapes of Rwanda. It emphasizes on their impacts on cereal and sugarcane stemborers and wild species, their ecological dependence on wild host vegetation, and their responses to climate and landscape changes. Recent studies reported that stemborers have started to shift from their natural habitats and attacking new host plants that were not used to be hosts before. The research was motivated by high speed increasing landuse change by agriculture intensification and urbanization in changing climate that modify natural habitats of stemborers. In addition to this curiosity, less information on stemborer population in Rwanda is available and do not clearly show how environmental gradients, vegetation mosaics, and and these changes reshape stemborers community structure and genetic composition. The field-based ecological results revealed a substantial species richness, host-plant diversity, and habitat-driven distribution patterns. Surveys yielded 18 stemborer genera recorded from 56 host plant species. The most interesting points is that the highest abundance and diversity of stemborers were concentrated in urban and peri-urban wetlands of Kigali City, highlighting the ecological role of human-modified habitats. Poaceae hosts accounted for over 60% of all larvae collected, and common species exchangeable from wild to crop vis versa for survival, where Napier grass (Pennisetum purpureum) served as the primary refugia during dry. The specific survey conducted in sugarcane plantation shows that sugarcane support mass population of Eldana Saccharina Walker, 1865. The population vary by season and first population start in May, a month of transition between heavy rain season (March-early May) to dry late May to August. The population reached peak in August. The infestation severity varied across sugarcane varieties with the most affected was green and red sugarcane varieties that whitepowdery sugar industrial variety. Sanitation practices of old-leave removal in sugarcane plantation have shown a critical effect in reducing population dynamics of sugarcane stemborers, suggesting this practice as pesticides-free method to control stemborers in sugarcane plantation system. For molecular ecology of key stemborer species through genetic analyses of Sesamia nonagrioides (Lefèbvre, 1827) and E. saccharina, Ethiopian population as earliest studied populations in Africa xxii were used as model to understand Rwandan population’s genetic diversity and diververgence. Mitochondrial COI sequencing showed high genetic diversity in selected model species that were associated with wetland vegetations and these from maize and sugarcane. Among these species, wetland associated species and these associated with crops were standing alone as connected sisters that share common ancester but evolved differently in different time. There were no shared haplotypes between population of Rwanda and model population from Ethiopia. The results suggest that over time, landscape history, wetland degradation, climate gradients, and agricultural expansion are shaping contemporary genetic differentiation, and concludes that region-specific biological control strategies, improved surveillance, and cross-habitat management are essential, as genetically distinct populations may respond differently to control measures. Observed variations in the distribution of pest and non-pest stemborer species, together with differences in genetic structure among key model species, indicate that no single management strategy is suitable across landscapes and that continued habitat fragmentation will likely destabilize ecosystems, leading to host range expansion or local extinctions. These patterns reflect broader environmental change, where habitat fragmentation at the local scale reduces connectivity and gene flow, while climate change at regional and global scales drives shifts in species distribution, community reorganization, and biodiversity loss. Together, these processes highlight the need for multi-scale, integrative research to understand stemborers species responses to thesehh combined effects and to support the development of context-specific, climate-smart integrated pest management strategies for sustainable agriculture 213

Assessment of Woody Species Diversity and Carbon Stock Estimation along Altitudinal Gradient of Kulkal Ber Natural Forest in Maksegnet District, Northwestern Ethiopia

2026-06-05T06:52:31Z

Assessment of Woody Species Diversity and Carbon Stock Estimation along Altitudinal Gradient of Kulkal Ber Natural Forest in Maksegnet District, Northwestern Ethiopia Asmare Belay, Endawok Forest ecosystems play a vital role in mitigating climate change and conserving biodiversity. Assessing their woody species diversity and carbon stocks along altitudinal gradient is essential for informing forest management strategies that enhance carbon sequestration in both vegetation and soil. This study aimed to establish baseline data on woody species diversity, structural attributes, and carbon stock potential along altitudinal gradient of the Kulkal Ber Natural Forest in Maksegnet District, Northwestern Ethiopia. Data collection was conducted using a stratified systematic sampling approach. Six transects, spaced 500 m apart along the altitudinal gradient, were established. A total of 60 plots (20 m × 20 m) were systematically placed at 200 m intervals along the transect lines. Additionally, five 5 m × 5 m subplots (positioned at the corners and center of the main plot) were used for sampling shrubs. Within each 5 m × 5 m subplot, a single 1 m × 1 m nested subplot was used to collect ground herbaceous layer (GHL) and soil samples. Woody species diversity was assessed using the Shannon-Wiener diversity index (H'), while hierarchical cluster analysis was performed to classify plant community types. Above and belowground biomass was estimated using general allometric models, and soil organic carbon (SOC) and grass, herb, and litter (GHL) carbon content were determined through laboratory analysis. A total of 36 woody species belonging to 26 families and 31 genera were identified. The overall Shannon-Wiener diversity index (H') was 1.801, with an evenness value of 0.48. The six most abundant species, in descending order of density, were Dodonaea angustifolia, Combretum molle, Rhus glutinosa, Millettia ferruginea, Rhus vulgaris, and Cordia africana. The forest’s basal area was 6.53 m² ha⁻¹. ANOVA results indicated that altitudinal variation had no significant effect on species diversity. However, species composition, evenness value, and structural attributes highlighted the dominance of few species, with low importance value indices. Hierarchical cluster analysis identified three distinct plant community types, such as Ficus thonningii–Dodonaea viscosa, Olea europaea–Clausena anisata, and Myrsine africana–Euphorbia tirucalli. The total mean carbon stock of the forest was 150.76 t C ha⁻¹, with aboveground carbon (AGC) of 57.29 t C ha⁻¹, belowground carbon (BGC) of 15.47 t C ha⁻¹, grass, herb and litter (GHL) carbon of 3.21 t C ha⁻¹, deadwood carbon (DWC) of 2.86 t C ha⁻¹, and soil organic carbon (SOC) of 71.93 t C ha⁻¹. While AGC, BGC, and SOC showed no significant variation with altitude, GHL carbon was significantly higher at lower altitudes, suggesting that altitude influences ground herbaceous layer carbon accumulation. The forest’s population structure exhibited a reversed J-shaped height class distribution in the two altitudinal gradients, dominated by small trees and shrubs, indicating good regeneration potential. These findings emphasize the importance of conservation measures and sustainable management strategies to safeguard the genetic resources and carbon sequestration capacity of Kulkal Ber Natural Forest. 85

TRADITIONAL MEDICINAL PLANTS IN HADES FOREST, DOBA WEREDA, WEST HARARGHE, ETHIOPIA; LOCAL KNOWLEDGE, CONSERVATION STATUS AND THREATS A

2026-06-03T06:47:33Z

TRADITIONAL MEDICINAL PLANTS IN HADES FOREST, DOBA WEREDA, WEST HARARGHE, ETHIOPIA; LOCAL KNOWLEDGE, CONSERVATION STATUS AND THREATS A Tewodros, Aynyirad Medicinal plants play a vital role in primary healthcare systems in Ethiopia, where access to modern medical services remains limited. This ethnobotanical study was conducted in Hades Forest and the surrounding communities of Doba Woreda, West Hararghe Zone, Ethiopia, to document traditional medicinal plant knowledge, assess patterns of use, and evaluate conservation status and threats. Data were collected from 120 informants, comprising 105 randomly selected general informants and 15 purposively selected key informants, using semi-structured interviews, guided field walks, and direct observations. Quantitative ethnobotanical indices, including preference ranking, Informant Consensus Factor (ICF), Relative Frequency of Citation (RFC), Relative Importance Index (RI), and Cultural Importance Index (CI), were applied to analyze medicinal plant use patterns and cultural significance. A total of 49 medicinal plant species belonging to 32 families were recorded for the treatment of human and livestock ailments. Ocimum lamiifolium and Verbascum sinaiticum were the most preferred species for medicinal use, while Echinops kebericho exhibited the highest RFC (74.1%) for livestock ailments and the highest Cultural Importance Index (0.7). Informant consensus was highest for dermatological disorders in humans and digestive disorders in livestock (ICF = 0.96). Traditional medicinal knowledge was predominantly transmitted orally within families, with elders possessing significantly greater knowledge than younger informants and general community members (P < 0.05). However, no significant differences in medicinal plant knowledge were observed across gender or educational levels (P > 0.05). Several medicinal plant species, including Cissampelos mucronata and Myrtus communis, were identified as increasingly threatened due to anthropogenic pressures such as deforestation and agricultural expansion. The study highlights the rich ethnomedicinal knowledge associated with Hades Forest, alongside the vulnerability of both medicinal plant resources and orally transmitted indigenous knowledge, emphasizing the need for locally tailored conservation and sustainable management strategies. 95