Common garden experimental data on temperature effects in offspring of four Odontesthes regia populations collected along the Chilean coast from Sep 2023 to Dec 2025

To study patterns of local adaptation to latitudinal temperature gradients in the ocean, we conducted two common garden experiments on the Chilean silverside (Odontesthes regia). Wild adult spawners from four locations (20 – 42°S) along the Chilean coast were used to produce offspring that was then reared in triplicates from fertilization to approximately 35 mm total lengths (TL) under a set of four common temperatures in the laboratory (11-23°C) and ad libitum feeding conditions. Larval and juvenile TL were measured via calibrated digital pictures (intermediate samples) or via calipers (final samples). Subsequently, the data will allow calculating population, temperature, and life-stage-specific growth capacities (i.e., TL growth rates at excess feeding conditions). This will reveal whether higher latitude populations have evolved genetically faster growth capacities than lower latitude populations – as has so far been shown only for northern hemisphere fishes. In addition, adults collected from each location were x-rayed to count the vertebrae of each specimen and subsequently test whether lower latitude populations have fewer vertebrae on average than their higher latitude conspecifics – a phenomenon known as Jordan’s Rule.

This dataset includes measurements of total length (TL) and wet weight (wW), developmental stage (Stage), individual ID, and key dates including fertilization, main hatching, and sampling. It also contains population information (Species, Population, Fert_num), collection site metadata (Longitude, Latitude), and specific conditions of the common garden experiment, such as temperature treatment (Temp_treat), replicate number, and bucket ID.

The supplemental tables provide additional data including adult total length and collection metadata (Table 1), vertebral counts from x-ray images and associated metadata (Table 2), and high-resolution temperature records from each experimental treatment tank throughout the common garden experiment (Table 3).