Comparative Analysis of Drought Tolerance in Indigenous and Invasive Plant Species

Thesis Abstract

Drought stress poses a critical challenge to plant survival and ecosystem stability, particularly amidst escalating climate variability and anthropogenic pressures that influence biodiversity and invasive species proliferation. This study aims to conduct a comparative analysis of drought tolerance between selected indigenous and invasive plant species to elucidate their respective adaptive mechanisms and implications for biodiversity conservation and invasive species management. The specific objectives include assessing morphological and physiological responses to drought conditions, identifying key traits associated with drought resilience, and determining the relative tolerance levels of the selected species. The research adopts a mixed-methods approach, combining quantitative experimental design with qualitative analysis, to enhance the robustness of findings. The study population comprises 12 plant species, with six indigenous and six invasive species, selected based on their prevalence in semi-arid regions of the Mediterranean Basin. A factorial design under greenhouse conditions was employed, with each species subjected to three water regimes optimal watering (control), moderate drought, and severe drought, replicated across 10 individual specimens per treatment, resulting in a total sample size of 360 specimens. Data collection involved biochemical assays to measure chlorophyll content, proline accumulation, and antioxidant enzyme activities; morphological assessments including root and shoot biomass measurements; and physiological parameters such as stomatal conductance, transpiration rate, and water use efficiency, utilizing portable photosynthesis systems and spectrophotometry. Data analysis was carried out using analysis of variance (ANOVA) to identify significant differences in responses among species and treatments, followed by Tukey’s HSD test for post hoc comparisons. Principal component analysis (PCA) facilitated the identification of key traits contributing to drought tolerance. Regression analysis modeled the relationships between physiological responses and drought severity, providing insights into resilience levels. Theoretical frameworks underpinning this analysis include the Stress Tolerance and Exotic Species Introduction theories, which inform the interpretation of adaptive traits and invasion success under water-deficit conditions. Expected findings indicate that invasive species demonstrate higher drought tolerance, evidenced by greater proline accumulation, more efficient water use strategies, and sustained biomass under severe drought, compared to indigenous species. Morphological traits such as deeper root systems and physiological responses like enhanced antioxidant activity are anticipated to be key differentiators. These results will contribute novel insights into the mechanisms underpinning drought resilience, particularly how invasive species adapt more effectively to water scarcity, potentially overshadowing indigenous counterparts. The study’s contribution to knowledge lies in elucidating contrasting adaptive strategies between indigenous and invasive species under drought stress, thereby informing conservation strategies and invasion management policies. It underscores the importance of trait-based approaches to understanding plant resilience in the context of climate change. The main conclusion suggests that invasive species generally possess superior drought tolerance mechanisms, which may facilitate their spread and dominance in arid and semi-arid ecosystems. Recommendations include integrating drought resilience traits into native species conservation programs, adopting invasive species management practices considering their adaptive advantages, and encouraging further research into the genetic basis of drought tolerance. The findings highlight the necessity for policymakers and land managers to consider ecological and physiological traits in biodiversity preservation amid increasing drought events driven by climate change.