Latitudinal patterns in a reproductive trait driven by sexual selection

Many organisms with broad distributions show latitudinal variations in morphological phenotypes and life history traits, such as body size and phenology, in relation to environmental changes such as temperature along latitude. Such variations have usually been considered the result of natural selection, but sexual selection may also lead to these latitudinal patterns. Although a recent study has shown the latitudinal pattern in the strength of male‒male competition in medaka fish, such a latitudinal pattern related to sexual selection is rarely known in other organisms. Here, we show the latitudinal pattern of a reproductive trait driven by sexual selection in the Japanese black salamander (Hynobius nigrescens), where snout-vent length (SVL) in males predicts the outcome of male‒male competition over egg sacs. First, we conducted phylogenetic analyses to examine the phylogenetic pattern along latitude. From the constructed phylogenetic tree, this species was split into five lineages tha..., , , # Latitudinal patterns in a reproductive trait driven by sexual selection

#### **Description of the data and file structure**

Sample information.xlsx: Sheet 1 contains the details of all samples used in this study. Collection site numbers and collection site names are the same as those in “morphological analysis data.xlsx” and “Phylogenetic analysis data.xlsx”. Experiment numbers are the same as those in the text. In the column named \"Egg acquisition\", \"1\" indicates a winning male, and \"0\" indicates a background male. Experimental data for latitudinal patterns of SVLs in larvae and juveniles are indicated as Experiment S10 (corresponding to Appendix S1: Fig. S10). Sheet 2 contains the details of the data in the experiment for “breeding period of male individuals” and “overall breeding period of females” in Experiment 2-1. Sheet 3 contains the details of the data in the experiment for the operational sex ratio in Experiment 2-2. The operational sex ratio was calculated as the number of...,