Data from: Increasing temperature weakens the positive effect of genetic diversity on population growth
Singleton, Alexandra et al. (2022), Data from: Increasing temperature weakens the positive effect of genetic diversity on population growth, Dryad, Dataset, https://doi.org/10.5061/dryad.sqv9s4n52
We sourced five clonal lines (B2086.2, A*III, CU438.1, A*V, and CU427.4) of the protist Tetrahymena thermophila from the Cornell University Tetrahymena Stock Center from across three putatively different genetic backgrounds (A*III and A*V have genetic background A, B2086.2 has background B, while CU438.1 and CU427.4, have background C). The lines were reared in Carolina Biological protist medium® (Burlington, NC) in 200mL autoclaved borosilicate jars, and a 16-8 day/night cycle at 22ºC within Percival growth chambers (Perry, IA).
To determine whether temperature alters the effects of genetic diversity on population growth, we manipulated the temperature and initial genetic diversity of microcosm populations. To manipulate genetic diversity, we started populations with a varying number of clonal lines (1, 2, 3, 4 or 5 lines). Monoclonal cultures were initialized with 50 individual protists. For all other treatments, the initial abundance of each clone depended on the total number of clones present, to control for possible effects of initial density: 2-clone populations started with 25 individuals/clone, 3-clone populations started with ~16 individuals/clone, 4-clone populations started with ~12 individuals/clone, and 5-clone populations started with 10 individuals/clone. Each monoclonal population, and each combination of four and five clones, was replicated 4 times. Each combination of two and three clones was replicated twice, for a total of 84 experimental populations per temperature. All experimental microcosms were reared in 3mL of growth media in 35 mm petri dishes.
We crossed the five genetic diversity treatments with four temperature treatments (19, 22, 25, 28 ºC) along the rising portion of the thermal performance curve (TPC) of the organism (Fig 1c), for a total 336 experimental microcosms. The TPC was itself was estimated as the intrinsic growth rate, r, of a well-mixed population (i.e., comprising the same number of initial individuals per clone, all starting at 3 ind/mL in 3mL petri dishes), at seven different temperatures (13, 19, 22, 27, 30, 32, 35 and 37 ºC). Experimental microcosms were grown in Percival growth chambers with all other environmental variables mimicking rearing conditions.
After a 24-hr incubation period, we estimated final population size by sub-sampling each microcosm and counting individual cells under a stereomicroscope (Leica, M205 C). Assuming exponential growth, the intrinsic growth rate (r, which has units of t-1) of each microcosm population was calculated as [log(Nf)-log(Ni)]/time, with time=1 day, Nf being the final abundance, and Ni the initial density (=50 ind for all experimental microcosms).
U.S. Department of Energy, Award: DE-SC0020362