Sexual and asexual reproductive strategies of submerged plant, Potamogeton crispus L., under simulated warming

The cosmopolitan submerged plant, Potamogeton crispus L., was used as a model species to study the effects of climate warming on reproduction. Turions from four different geographic temperate regions in China were used for the mesocosm experiment. A glasshouse experiment was used to mimic climate warming of 2.0 ℃–5.8 ℃. Number and biomass of turions and fruits were selected as proxies for asexual and sexual reproduction, respectively. Based on the potential correlation between scale leaf number of the turions and fitness of asexual propagules, the turions were classified into two categories: oligophyllous (scale leaf number ≤ 4) and pleiophyllous turions (scale leaf number > 4). Geographic sources and warming conditions significantly affected asexual and sexual reproduction in P. crispus. Although simulated warming had different effects on turion number in different clonal populations, total turion biomass did not decrease. Simulated warming led to a decrease in the percentage of oligophyllous turions and an increase in the percentage of pleiophyllous turions. Moreover, simulated warming led to total loss of sexual reproduction in three clonal populations. As P. crispus is mainly hydrophilous, we speculate that warming destroyed pollen viability, resulting in the total loss of sexual reproduction. The scale leaves were capable of nutrient storage and photosynthesis. Additionally, a positive correlation was found between scale leaf number and axillary bud number. We speculate that P. crispus maintains fitness via the production of larger-size asexual propagules under warming conditions as a reproductive life-history strategy to cope with climate warming.