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Phylogeography of invasive exotic plant species is crucial for identifying the source population from which a given invading population has originated. Ardisia crenata Sims, a shade tolerant shrub native to East Asia, is one of the most serious invasive exotic plants in Florida, North America. The objective of this study is to investigate the genetic differentiation and phylogeographical relationships among A. crenata native populations in Japan and invasive populations in Florida. We analyzed DNA from 188 individuals gathered from eight populations in Japan and four subpopulations in Florida using double‐digestion restriction‐associated DNA sequencing (ddRAD‐seq) and estimated a maximum likelihood phylogenetic tree among them. The results revealed four genetic clusters, with a striking dominance of genetically identical clonal individuals within the invading populations in Florida and four Honshu populations in Japan. These groups were genetically close to each other and to one cultivated individual sampled in Japan. In contrast, the individuals from Miyazaki, Yakushima, Kochi, and Iriomote in southwestern Japan were genetically distinct from Honshu and Florida individuals, showing high genetic diversity indicative of outcrossing. Given that A. crenata does not exhibit a vegetative clonal habit and all wild and cultivated plants regenerate from seeds, these results suggest that Honshu and Florida populations exclusively reproduced with seeds produced by apomixis. [ABSTRACT FROM AUTHOR]

The Bonin Islands, comprised of the Mukojima, Chichijima, and Hahajima Islands, are known for their isolated and distinctive habitats, hosting a diverse array of endemic flora and fauna. In these islands, adaptive radiation has played a remarkable role in speciation, particularly evident in the Callicarpa genus that is represented by three species: Callicarpa parvifolia and C. glabra exclusive to the Chichijima Islands, and Callicarpa subpubescens, distributed across the entire Bonin Islands. Notably, C. subpubescens exhibits multiple ecotypes, differing in leaf hair density, flowering time, and tree size. In this study, we aimed to investigate species and ecotype diversification patterns, estimate divergence times, and explore cryptic species within Callicarpa in the Bonin Islands using phenotypic and genetic data (double‐digest restriction site‐associated DNA sequencing). Genetic analysis revealed that C. parvifolia and C. glabra both formed single, distinct genetic groups. Conversely, C. subpubescens consisted of six genetic groups corresponding to different ecotypes and regions, and a hybrid group resulting from the hybridization between two of these genetic groups. Population demography analysis focusing on six Chichijima and Hahajima Islands‐based species/ecotypes indicated that all species and ecotypes except one ecotype diverged simultaneously around 73–77 kya. The star‐shaped neighbor‐net tree also suggests the simultaneous divergence of species and ecotypes. The species and ecotypes that simultaneously diverged adapted to dry environments and understory forests, suggesting that aridification may have contributed to this process of adaptive radiation. Moreover, leaf morphology, flowering time, and genetic analyses suggested the presence of two cryptic species and one hybrid species within C. subpubescens. [ABSTRACT FROM AUTHOR]

Farmlands are becoming more important as waterfowl foraging habitats, while natural wetlands are being lost globally. However, it is unclear how waterfowl coexist in agricultural landscapes by resource partitioning. We evaluated the diets of seven sympatric dabbling ducks foraging in rice paddy and lotus fields around Lake Kasumigaura, the second largest lake in Japan, during two wintering seasons (from November to February) by faecal DNA metabarcoding using chloroplast trnL and mitochondrial CO1 region sequences. We examined 420 faecal samples and found different patterns of dietary diversity and composition among the duck species. The pattern also differed between plant and invertebrate food. Dietary niche partitioning was clear in plant food. Large‐bodied ducks intensively use crop plants, and other ducks might mediate competition by using terrestrial and aquatic plants that are suitable for their foraging behaviours or microhabitats. Dietary segregation among species was the most apparent in February, when the abundance of foraging ducks was the largest. This study illustrated the complex pattern of dietary niche partitioning of dabbling ducks in agricultural landscapes, which might be difficult to evaluate by conventional approaches. The availability of crop plants, as well as other plant food resources in flooted areas and farmland dikes, may enable ducks to coexist by spatial or behavioural resource partitioning. [ABSTRACT FROM AUTHOR]