Ecological and Evolutionary Study of Korean Siderostictae Group of Carex (Cyperaceae)

다국어 초록 (Multilingual Abstract)

Carex sect. Siderostictae, an early-diverging lineage within Carex (Cyperaceae), is of particular interest due to its restricted distribution in East Asia. Of the 13 recognized species, four occur in South Korea: C. siderosticta, C. ciliatomarginata, C. okamotoi, and the endemic C. splendentissima. While C. siderosticta and C. ciliatomarginata are widespread across East Asia, C. okamotoi and C. splendentissima are narrowly distributed only in Korea. Phylogenetic analyses of rITS sequences question the distinctiveness of C. okamotoi: although most of its sequences form a single clade, some appear paraphyletic with respect to C. siderosticta, whereas C. siderosticta itself comprises multiple divergent rITS clades. Occurrence data further indicate that the four species are largely sympatric distributed. To assess ecological differentiation and potential drivers of divergence, species distribution models (SDMs) were constructed and niche similarity metrics (D and I) were calculated. The results revealed distinct distributional and ecological patterns among species. Niche equivalency tests showed that niches are significantly non-identical, and both symmetric and asymmetric background tests indicated strong niche differentiation. Ecospat analyses demonstrated that the niche envelope of C. splendentissima is consistently nested within those of its congeners, consistent with its narrow geographic range, while significant rangebreak blob tests further support non-random environmental partitioning. Together, these results suggest that niche divergence is shaped primarily by ecological filtering and local adaptation, rather than by geographic isolation, and may reflect parapatric or sympatric speciation processes within the group. Paleodistribution models indicate substantial range shifts and expansion from the Last Glacial Maximum to the present, whereas future projections predict species-specific expansion or contraction under climate change scenarios. Overall, this study demonstrates the power of integrating phylogenetic evidence with SDMs to refine species boundaries and to elucidate the evolutionary dynamics of Carex sect. Siderostictae.

목차 (Table of Contents)

• 1. Introduction 1
• 2. Materials and Methods 7
• 2.1. Molecular study and phylogeny 7
• 2.1.1. Preliminary phylogenetic analysis using database sequences 7
• 2.1.2. Molecular work to confirm phylogenetic relationship 7
• 2.2. Ecological niche modelling study 9
• 2.2.1. Data acquisition and cleaning 9
• 2.2.2. Environmental data processing 10
• 2.2.3. Optimization of ecological niche modeling in maxent 11
• 2.2.4. Maxent modelling 14
• 2.2.5. Model evaluation 14
• 2.2.6. Future and paleo ecological niche projections 15
• 2.2.7. Identification of species refugia 17
• 2.2.8. Ecological niche equivalency testing 17
• 2.2.9. Ecological niche comparison among native Carex populations
• in South Korea and Japan 18
• 3. Results 20
• 3.1. Evolution of of nrITS sequences in Carex, Siderostictae group 20
• 3.1.1. Phylogenetic relationships based on nrITS sequences 20
• 3.2. Species distribution modelling of Carex, Siderostictae
• group in South Korea 25
• 3.2.1. Performance of current species distribution models 25
• 3.2.2. Current niche models and refugial area of species 30
• 3.2.3. Ecological niche breadth proves they are not the same species 36
• 3.2.4. Paleo-distribution models reveal the past of existence while
• future projections show the stability of habitat-suitability 40
• 3.2.5. Ecological niche overlap analysis: identity tests reveal
• significant niche differences, while background tests suggest
• ecological divergence, and range-break blob test keeps
• sympatric distribution niches might be more similar than
• expected 45
• 4. Discussion 56
• 4.1. Intragenomic ITS variation and its impact on Phylogeny 56
• 4.2. The reliability and good capture of the models 59
• 4.3. Niche conservatism: an integrated evolution, ecology of Carex,
• Siderostictae Group 62
• 5. References 69
• 6. Appendices 87
• Appendix A 87
• Appendix B 88
• Appendix C 90
• Appendix D 94
• Appendix E 95
• Appendix F 97
• Appendix G 99
• Appendix H 101