3.1 The relationships between male body size, ornamental traits, and temperature
Our analysis revealed that male body mass decreased with increasing ambient temperature (Table 1). Furthermore, we discovered a significant interaction effect between male ornament coloration and ambient temperature, as evident from both Table 1 and Figure 2a. Our findings indicate that the relationship between male body mass and ornament coloration was temperature dependent. Specifically, at higher ambient temperatures, there was a positive association between male body mass and ornament coloration, while in colder environments, this relationship became negative (Figure 2b, S2).
3.2 The relationships between male ornamental traits, female body size, and temperature
We investigated the relationship between female body size and ambient temperature, and found no significant correlation (Table 2, Table S4). Moreover, we did not observe any consistent correlation between female body size and male body size (Table 2, Table S4). However, we did find an interesting interaction between ambient temperature and male ornament color (MPC1) in relation to female tarsus length (Table 2, Figure 2a, c, Figure S3). Our results suggest that larger females tend to mate with males possessing more colorful ornaments in warmer environments (Figure 2c).
Furthermore, our analysis revealed a positive correlation between female ornament coloration (FPC1) and size (FPC2) with male ornamentation (Table S4). Additionally, we observed that ambient temperature acted as a modulator in the assortative mating based on male and female ornamentation (Table S4, Figure 2a). Specifically, we found a positive relationship between male and female ornamentation in warmer environments (Figure S4a, b).