Adaptive convergence and divergence underpin the diversity of Asteraceae in a semi-arid lowland region

Abstract

Asteraceae is the most diverse family primarily found in semi-arid areas and species from the same botanical family have comparable phenotypes, occupy semi-arid habitats, and have adaptive convergences to environmental stress. Such characteristics aid in understanding adaptive radiations of recent groups on a regional scale and their successful establishment in habitats with challenging climatic and edaphic conditions. We investigated the adaptive convergence of the family as well as the fragile balance between fine-scale variation in adaptive traits and general convergence towards stress-tolerance and adaptation to aridity, using thorough field surveys and trait-based ecological approaches. Data was collected between 2020 and 2022 using the quadrat approach encompassed across 60 sites and five habitat types. Multivariate statistical methodologies were applied to analyze plant traits and soil variables. The tribes Cichorieae, Cardueae, and Heliantheae emerged as dominant contributors to the flora, illustrating their adaptability to varied ecological conditions. Microphyll emerged as the dominant leaf type, and therophytes prevailed as the most abundant life form. Urban habitats exhibited heightened sensitivity to Asteraceae species, as reflected in diversity indices. Canonical Correspondence Analysis demonstrated the significant influence of soil moisture, pH, phosphorus, and soil saturation on species distribution, with indicator species analysis highlighting habitat-specific plant-environment relationships. The study further classified species into adaptive strategies using CSR (competitive strategy-stress tolerant strategy-ruderal strategy) categorization. While some species exhibited pronounced R or S strategies, a majority demonstrated mixed strategies, such as R/CR, R/CSR, CS/CSR, emphasizing the versatility of adaptation strategies within the Asteraceae family. The findings underscore the intricate interplay between environmental variables and Asteraceae phylogenetic and functional diversity, highlighting the significance of soil properties in influencing plant distribution in semi-arid ecosystems. This research contributes valuable insights into the ecological dynamics of Asteraceae, shedding light on their responses to diverse environmental conditions and providing a nuanced understanding of the factors influencing their spatial distribution.