Filtered phytoplankton movement data

<ol> <li><span>A prerequisite for the survival and reproduction of organisms is to successfully navigate thermal environmental conditions that unfold over time and space. While effective movement behaviour has been highlighted as a key mechanism by which organisms and populations may persist amidst the backdrop of directional environmental warming, it remains unclear how behavioural plasticity may mediate such effects, particularly across timescales that span multiple generations.</span></li> <li><span>Here, we examine the capacity for transgenerational plasticity to alter the movement behaviour of the motile green algae <em>Chlamydomonas</em> <em>reinhardtii</em> in response to changes in thermal conditions.</span></li> <li> <span>We first acclimated <em>C</em>. <em>reinhardtii</em> populations to thermal environments near (25°C), below (12.5</span><span>°</span><span>C), or above (37.5</span><span>°</span><span>C) the temperature range that maximizes population growth rates. Subsequently, we assayed the micro-spatial scale movement behaviour of these populations in thermally homogeneous environments across a period of two weeks in each respective environment, with the goal of evaluating the influence of thermal history on movement behaviour in a novel thermal environment.</span> </li> <li><span>These results indicate that thermal history can mediate the movement patterns of <em>C</em>. <em>reinhardtii</em> individuals for up to ten generations and that the trajectory by which phenotypes converge on their acclimated values can be highly non-linear.  Subsequently, we demonstrated – using a dispersal assay in spatially variable environments – that thermal acclimation history can additionally alter movement patterns at ecologically relevant scales.</span></li> <li> <span>Collectively these findings indicate the possibility for transgenerational plasticity to modify behaviour across extended timescales and converge on acclimated states via non-linear trajectories. U</span><span>nderstanding the efficacy of behaviour for navigating novel thermal environments, such as environments anticipated amidst environmental warming, may thus require considering past as well as present environmental conditions.</span> </li> </ol>