Phenotypic variation among different populations of Xanthium strumarium L. and modelling its potential future spread areas under changing climate

Phenotypic variation is frequently used in studies investigating the effect of global change on plant species and communities. In this study, 15 populations of Xanthium strumarium were used to determine phenotypic variations among the populations. The vegetative and generative differences between populations arising from different regions (Black Sea, Marmara and Central Anatolia) were experimentally tested. Seeds of these populations were placed in water for 10 days and then planted in pots (3 seeds per pot). After seedling emergence, 1 healthy plant was selected per pot and its development was followed. The experiment was established as randomized complete block design with 3 replications for each harvest period of each population and the plants were harvested in 6 different periods (30, 50, 70, 90, 110 and 130 days after seedling emergence). The data collected from harvested populations were associated with climate data of their origin as early (30-50 days), medium (50-70 days) and late (110-130 days after seedling emergences) periods. Population growth averages were associated with altitude (m), daylength (h), precipitation (mm) and temperature (oC) factors. It was observed that X. strumarium populations gave various vegetative development responses in different periods of data collection, which caused phenotypic variation in the tested populations due to differences in their development. Phenotypic variation studies are conducted in a supportive manner to the studies of species distribution models (SDMs) which contribute to the determination of the spatial distribution of plants. While SDMs have been increasingly used to identify and map current and future distribution areas of species at regional or global scale, their use in predicting potential distribution areas of native/weed species remains limited. Therefore, the potential distribution of X. strumarium, which causes a lot of problems in agriculture and non-agricultural areas, has been investigated in this study. MaxEnt model in a hierarchical fashion was used to map the current and future potential distribution of the species in Turkey. The model was calibrated on global scale and projected for Turkey. The distribution of X. strumarium was predicted for the current and future (2030, 2050, 2070, 2100) climatic conditions. The climatic data generated by two global circulation models (GCM), namely the Commonwealth Scientific and Industrial Research Organization (CSIRO_mk3_6_0) and Interdisciplinary Research on Climate (MIROC_MIROC5) was used in the study. At the same time, the distribution areas were estimated under two different climate change scenarios, i.e., representative concentration pathways (RCP), RCP2.6 (moderate climate change) and RCP8.5 (severe climate change). The results predicted that the X. strumarium will increase its distribution steadily in the country in future. Nevertheless, the results predicted that the range of the species will remain consistent to the current distribution ranges of the species, whereas global warming will increase the distribution areas of the species where it is still absent. KEYWORDS: Climate Change, Phenotypic Variations, Species Distribution Models, Xanthium strumarium