Habitat diversification associated with urban development has a little effect on genetic structure in the annual native plant Commelina communis in an East Asian megacity

Urban development greatly alters the natural and semi-natural habitats of native plants. Urbanisation results in a range of diverse habitats including remnant agricultural lands, urban parks, and roadside habitats. This habitat diversity often promotes trait divergence within urban areas. However, the mechanisms by which diverse urban habitats influence the population genetic structure of individual plant species remain poorly understood. We investigated the effects of urbanisation on genetic diversity and structure within 24 Commelina communis populations across diverse habitat types (rural agricultural land, urban agricultural land, urban park land, and urban roadsides) within the Kyoto-Osaka-Kobe megacity in Japan. We conducted multiplexed inter-simple sequence repeat genotyping to compare genetic diversity among populations in different habitats. We also examined the correlation between Nei's genetic distance and geographic and environmental distances and performed principal coordinate analysis (PCoA) to evaluate genetic differentiation among urban habitats. There were no significant differences in genetic diversity indices between urban and rural populations and among urban habitat types. Although we detected no isolation-by-distance structure in population pairs of the same habitat type and in those of different habitats, the difference in surrounding landscape facilitated genetic differentiation not only between urban and rural habitats but also between different urban habitats. PCoA revealed no clear genetic differentiation among rural and urban habitat populations. Our findings indicate that the establishment of diverse habitat types through urbanisation has no and little impact on genetic diversity and structure, respectively, in C. communis, likely due to its high selfing rate and ability to adapt to urban conditions.

The genetic structure and demographic history of Zabelia tyaihyonii, endemic to Korean limestone karst forests, based on genome-wide SNP markers

Similar to the global phenomenon, many plant species endemic to Korean limestone karst forests are at risk of extinction due to human intervention. Zabelia tyaihyonii is a familiar shrub, called "Hardy abelia" and "Fragrant abelia" growing in the karst forests of Korea, where it is one of the most threatened species. We investigated the genetic structure and demographic history of Z. tyaihyonii, which allow us to develop appropriate conservation and management strategies. The genetic structure was evaluated using a total of 187 samples from 14 populations, covering the entire distribution of Z. tyaihyonii in South Korea. We utilized 254 and 1753 SNP loci obtained via MIG-seq (Multiplexed ISSR Genotyping by sequencing) for structure and demographic analyses, respectively. The population demographic modeling was performed with site frequency spectrum. To gain further historical insights, we also employed ENM (Ecological Niche Modeling). We found two distinct clusters (CLI and CLII) of ancient origin (ca. 490 ka). Despite CLII experiencing a more severe bottleneck, both clusters showed similar levels of genetic diversity, indicating mutual historical gene flow. Their historical distribution range seems to have changed very little. We proposed a historical distribution scenario for Z. tyaihyonii, taking into account its intrinsic factors, and emphasized a more complex response to Quaternary climate change beyond simple allopatric speciation models. These findings provide valuable insights for conservation and management strategies for Z. tyaihyonii.

Population genetic structure and evolution of Batesian mimicry in Papilio polytes from the Ryukyu Islands, Japan, analyzed by genotyping-by-sequencing

Batesian mimicry is a striking example of Darwinian evolution, in which a mimetic species resembles toxic or unpalatable model species, thereby receiving protection from predators. In some species exhibiting Batesian mimicry, nonmimetic individuals coexist as polymorphism in the same population despite the benefits of mimicry. In a previous study, we proposed that the abundance of mimics is limited by that of the models, leading to polymorphic Batesian mimicry in the swallowtail butterfly, Papilio polytes, on the Ryukyu Islands in Japan. We found that their mimic ratios (MRs), which varied among the Islands, were explained by the model abundance of each habitat, rather than isolation by distance or phylogenetic constraint based on the mitochondrial DNA (mtDNA) analysis. In the present study, this possibility was reexamined based on hundreds of nuclear single nucleotide polymorphisms (SNPs) of 93 P. polytes individuals from five Islands of the Ryukyus. We found that the population genetic and phylogenetic structures of P. polytes largely corresponded to the geographic arrangement of the habitat Islands, and the genetic distances among island populations show significant correlation with the geographic distances, which was not evident by the mtDNA-based analysis. A partial Mantel test controlling for the present SNP-based genetic distances revealed that the MRs of P. polytes were strongly correlated with the model abundance of each island, implying that negative frequency-dependent selection interacting with model species shaped and maintained the mimetic polymorphism. Taken together, our results support the possibility that predation pressure, not isolation by distance or other neutral factors, is a major driving force of evolution of the Batesian mimicry in P. polytes from the Ryukyus.