The contribution of climate in shaping microevolutionary patterns of diatoms in Lake Ohrid during the Late Calabrian stage

Climate has strongly influenced species composition and evolution over geological and contemporary timescales. While most attention has been paid to the relationship between macroevolutionary processes and climate along latitudinal gradients, very little is known about how climate changes affect the microevolutionary mechanisms of macroevolutionary processes through time due to the lack of fossils. Here, we use the morphologically variable endemic diatom species, Cyclotella cavitata, and paleoenvironmental data from a sedimentary succession of Lake Ohrid between 1050 ka and 815 ka to investigate the effects of climate on microevolutionary dynamics in diversification processes during the Late Calabrian period. By analyzing morphotype-environment relationships, we found a progressive replacement of morphologies and their abundance in C. cavitata that was mainly related to local environmental changes associated with nutrient availability, lake depth, water column, mixis, and local temperatures. Surprisingly, climate change did not have as great an influence as anticipated, but this cannot be ruled out since this period overlaps with the beginning of the Mid-Pleistocene Transition. This suggests that although the local environment had a greater influence on microevolutionary processes, climate remains an important driver and will also be critical for studies of evolutionary change under future climate change scenarios.