DOI: 10.5281/zenodo.4048074
title: Data from Koch et al. 2020 Evolution: Genetic variance in fitness and its cross-sex covariance predict adaptation during experimental evolution.

description: <strong>Abstract</strong> In presence of rapid environmental changes, it is of particular importance to assess the adaptive potential of populations, which is mostly determined by the additive genetic variation (V<sub>A</sub>) in fitness. In this study we used <em>Tribolium castaneum </em>(red flour beetles) to investigate its adaptive potential in three new environmental conditions (Dry, Hot, Hot-Dry). We tested for potential constraints that might limit adaptation, including negative genetic covariance between female and male fitness. Based on V<sub>A</sub> estimates for fitness, we expected the highest relative fitness increase in the most stressful condition Hot-Dry and similar increases in single stress conditions Dry and Hot. High adaptive potential in females in Hot was reduced by a negative covariance with male fitness. We tested adaptation to the three conditions after 20 generations of experimental evolution and found that observed adaptation mainly matched our predictions. Given that body size is commonly used as a proxy for fitness, we also tested how this trait and its genetic variance (including non-additive genetic variance) were impacted by environmental stress. In both traits, variances were sex and condition dependent, but they differed in their variance composition, cross-sex and cross-environment genetic covariances, as well as in the environmental impact on V<sub>A</sub>. <strong>Method</strong> <em>Strain and environmental conditions</em> We used the <em>Tribolium castaneum</em> Cro1 strain collected from a wild population in 2010 and adapted to lab standard conditions (33°C, 70% relative humidity) for more than 20 generations. Beetles were kept in 24h darkness on organic wheat flour mixed with 10% organic baker's yeast. We sterilized flour and yeast by heating them for 12h at 80°C before use. To test for adaptation to new environmental conditions we used replicate lines and exposed them to three treatments and Control conditions. The conditions in the treatments were: Dry: 33°C and 30% relative humidity; Hot: 37°C and 70% r. h.; Hot-Dry: 37°C and 30% r. h. <em>Crossing, fitness assay and measurement of body size</em> In order to be able to estimate genetic variances, we applied a split-brood paternal half-sib breeding design. We produced 147 half-sib families by mating virgin males to three virgin females. Half- as well as full-sib families were split across all conditions. Male and female offspring (four females and two males per full-sib family and condition) were separated at the pupal stage and transferred to 10 mL tubes with 1 g of medium and remained there until they were used for the fitness assay eight weeks later. To estimate fitness, we mated each virgin male with two unrelated virgin females from the same condition in 15mL tube with 1g medium. The male was removed after 24h and females transferred into two separate tubes. Females were removed from the tubes after one week of egg laying, and 9g medium was added to provide food for the developing offspring. After five weeks the number of adult offspring was counted. While we conducted the matings for the fitness assay, we followed a specific crossing design and always crossed two pairs of full-sib families. Individuals resulting from these crosses (the F2 genaration) were double first cousins. Body size was measured in the F2, i.e. in the offspring of beetles that were used for the fitness assay. To estimate body size, we used the centroid size of the abdominal segment IV as proxy for total size since it can be measured more accurately than dry weight in very small insects and shows a high correlation with body mass. <em>Experimental evolution</em> We used ten replicate lines per condition originating from the same ancestral population (Cro1) and let them adapt for 20 generations. Each new generation was set up by randomly selecting 120 pupae and placing them into a new vial with 70g medium. One selection line in Dry became extinct. Adult beetles of generation 20 from all selection lines were transferred to control conditions, in which they stayed for one week to mate and lay eggs. After removal of the adults, we waited until their offspring had reached the pupal stage and separated males and females. These individuals (generation 21) developed completely in control conditions. When they had reached the adult stage, each virgin male was mated with a virgin female of the same selection line and their offspring was transferred to all four conditions in the egg stage, resulting in full-sib families split across all conditions . As soon as these offspring (generation 22) had reached the pupal stage, males and females were separated. To compare fitness of different selection lines and test for adaptation, a virgin male and a virgin female of the same selection line in the same condition, but from different families were mated and the number of adult offspring produced within four days of mating and egg laying was used as a fitness estimate. <strong>Files</strong> This data publication contains the following files: Fitness_data.txt: Fitness data (offspring number) of the first generation in new environmental conditions. ANIMAL: ID of female individuals; male: ID of mating partner, father of the offspring; fitness: number of adult offspring per female produced within one week of egg laying; condition: condition under which the individuals grew up, mated, reproduced (CTL: control, D: dry, H: hot, HD: hot-dry, see Methods for details); MOTHER: mother of the female; Batch: samples where fitness assay was started on the same day Size_data.txt: Centroid size of abdominal segment IV. ANIMAL: ID of measured individuals; condition: condition under which the individuals grew up (CT: control, D: dry, H: hot, HD: hot-dry, see Methods for details); sex: sex of individuals (f: female, m: male); AS: centroid size [Pixel] of abdominal segment IV; Mother: ID of their mother; batch: Batches represent individuals that grew up at the same time, and thus accounts for variations in the medium or lab temperature Pedigree.txt: Pedigree of measured individuals. ANIMAL: individual ID ; MOTHER: mother ID; FATHER: father ID Transplant_data.txt: Offspring number of different selection lines under different conditions after 20 generations of experimental evolution. Line: Selection-line ID; Selection: condition, in which the selection-line spent 20 generations (CT: Control; D: Dry; Hot; HD: Hot-Dry); Fam: each selection line consisted of several families; Treatment: condition, in which offspring number was measured; offspring: number of adult offspring that a female produced within four days of egg-laying