Artificial developed habitats can sustain plant communities similar to remnant ecosystems in the Tokyo megacity

Artificially developed habitats in urban ecosystems, known as novel ecosystems, have recently been underscored in terms of increasing urban green cover. However, patterns of changes in species diversity and composition in novel ecosystems over time remain poorly understood, making it unclear whether all novel ecosystems contribute to urban biodiversity. Here, we assessed how plant species diversity and composition in developed habitats changed over the years since the development of habitats (years since development) using a space-for-time substitution approach in the megacity, Tokyo, Japan. We established multiple survey transects at each study site to investigate the plant species diversity and composition. Using the ordination regression-based approach, we found that the plant species composition in developed habitats changed over the years since development and became similar to that in remnant habitats after approximately 130 years. We also found that the diversity of native plant species did not change whereas that of exotic species decreased with the years since development. Our results demonstrate the importance of developing new habitats for conserving urban biodiversity, while highlighting that exotic species can easily establish in newly developed habitats. Given that remnant ecosystems in urban areas are degraded by urbanization, the time required for novel ecosystems to become similar to remnant ecosystems is essential for predicting and conserving future urban ecosystems.