Winter temperature effects in a cold-adapted northern population of a range-expanding spider: survival, energy stores, and differential gene expression
Abstract
Species expand their spatial distribution when environmental conditions are favorable or when mutations arise that allow them to live in previously unfavorable conditions. The European wasp spider, Argiope bruennichi, is known to have expanded its range poleward faster than climate change would predict. Northern edge populations show higher cold tolerance and are genetically differentiated from core populations, suggesting local adaptation to colder winter conditions. To investigate the degree and limits of plasticity in a cold-adapted population, we exposed overwintering juveniles (spiderlings) from Estonia - the northern edge of the distribution - to three winter regimes: two with a strong difference in day/night temperatures and an overall 10 degrees difference (warm and cold treatment) and one with moderate temperatures and less difference between day and night (moderate). We investigated if survival, lipid content, metabolites, and gene expression patterns differ depending on these temperature regimes. The survival probability of the spiderlings and their overall lipid content decreased over winter, with no difference between treatments, suggesting high resilience of the spiderlings towards very different temperature regimes at the edge of the distribution. At the end of winter, the content of saturated and monounsaturated fatty acids per spiderling also did not differ between treatments. However, omega-3 polyunsaturated fatty acids (PUFAs) levels were significantly lower in spiders exposed to the warm winter, suggesting increased metabolic activity. We identified 4096 significant differentially expressed genes (DEGs) across the treatments, of which 1389 were specific for the moderate treatment, and 832 specific for the warm treatment, while 69 were unique for the cold treatment, showing a stronger temperature stress response to the moderate and warmer than to the cold treatment. Taken together, our results show that A. bruennichi has physiological plasticity and the ability to cope with very different winter temperature regimes despite being cold-adapted. However, warmer winters might come with metabolic costs that could impact the spiderlings' survival and foraging success when they emerge from the egg sac in spring.
Winter temperature effects in a cold-adapted northern population of a range-expanding spider: survival, energy stores, and differential gene expression. Carolina Ortiz Movliav, Marina Wolz, Michael Klockmann, Andreas Kuss, Lars Jensen, Corinna Jensen, Alexander Wacker, Gabriele Uhl
