Is climate warming advantageous for plants with untoothed leaves?

Abstract

The percentage of dicotyledonous species with untoothed leaf margins is positively correlated with mean annual temperature across different continents and biomes. Paleobotanists commonly use this relationship as an index for inferring temperature in the past. However, leaf margin analysis often estimates cooler temperatures than alternative methods. Therefore, the following research hypothesis was stated: due to the observed climate warming, species with untoothed leaves are in better ecological status than species with toothed leaves. Responses of flora to global warming were studied for species with toothed vs. untoothed leaf margins after assigning species to the following categories based on data in the literature: (1) frequency; (2) population trends; (3) degree of endangerment; and (4) protected plants. A total of 2388 dicotyledonous woody and herbaceous plant species of Central Europe (separately from Germany and Poland) were analysed. The results were very similar in both analysed countries and for herbaceous and woody species. Contrary to assumptions, it was found that untoothed species clearly dominate in rare, disappearing, endangered, and protected plant groups. In contrast, plants with toothed leaf margins dominate in frequent and widespread species. The possible explanation is a delay in the response of local flora to climate change. This suggests a post-glacial relict nature of many species with untoothed leaves exists, persisting in local flora from the time of warmer periods. The constant error of underestimating past temperatures using the leaf margin method may explain the impact of today's flora in the models used because modern flora have more species with toothed leaves than expected. Taking into account the delayed reaction of flora to climate change may increase the accuracy of models predicting the climate in the past and in the future.