| dc.description.abstract | Arctic and alpine zones are low productivity systems characterized by extreme conditions such as low temperatures, heavy snow loads, and short growing seasons. Plants in these ecosystems have evolved specific adaptations, including compact forms, genetic freeze resistance, and reproductive strategies. However, human-induced climate change has dramatically increased global annual average temperatures over the last century, leading to cascading effects on the primary environmental stressors of Arctic and alpine ecosystems. Such widespread changes to the fundamental abiotic conditions can lead to a mismatch between plant evolutionary adaptations and altered environmental conditions. For instance, earlier snowmelt can alter the timing of water availability causing water stress, while changes in temperature can disrupt the synchronization between flower time and pollinator activity.
Silene acaulis, a cushion plant common in alpine and Arctic habitats, commonly exhibits a gynodioecy breeding system, consisting of females and hermaphrodites. Interestingly, this study also identified gynomonoecious, or mixed, individuals within the population. This thesis investigates how Silene acaulis responds to temperature by examining plant sex distribution, soil moisture levels, and their effect on plant health and reproductive outputs. The study used a natural elevational gradient and a long-term warming experiment with open top chambers (OTCs) at Finse, Norway. The warmest conditions were at the mid elevation. While there was no significant difference in plant sex distribution across groups, there was a non-significant 32% increase in female frequency from the low to high elevation, and a significantly higher proportion of females at the highest elevation. Surprisingly, higher soil moisture levels led to lower plant health, whereas plants inside the OTCs showed greater plant health, suggesting an initial positive response to increased temperatures.
The study revealed a complex relationship between environmental stress and reproductive strategies. Hermaphrodites had minimal pollination success, potentially due to an evolutionary shift towards male function. In contrast, females exhibited greater pollination success, possibly benefitting from outcrossing. A trade-off was observed between seed quantity and quality: the plants at the coldest site had the most seeds per capsule, while those at the warmest sites had the largest seeds. These findings suggest that S. acaulis demonstrates genotype x environment interactions and possible evolutionary shifts in response to climate change. The presence of mixed individuals may indicate an adaptive strategy to optimize reproduction under shifting environmental conditions, underscoring a dynamic relationship between the variation in climate and reproductive outcomes.
Understanding plant responses to shifts in environmental stress, particularly long-term effects on reproduction, is crucial for predicting how alpine species may adapt to ongoing changes to climate. | |
