Figure legends
Figure 1. Map of sampling sites located in Singapore and Malaysia.
Figure 2. A schematic diagram highlighting the precopulatory (horn length and maximum pronotum width) and postcopulatory traits (sperm length and testes weight) that were measured in male O.  babirussa .
Figure 3. Comparison of the average body size (pronotum width) of female and male O. babirussa  across populations from Malaysia (MY: Langkawi: n=318, Central Peninsular : n=97) and Singapore (SG: Pulau Ubin: n=121, CCNR: n=96) to determine the presence of sexual size dimorphism (SSD). SSD varied across populations (**=P <0.01, ***=P <0.001, ns=not significant).
Figure 4. log-log scatterplots to determine allometric relationship between body size and (a) horn length (CCNR: n=45, Pulau Ubin: n=61, Central Peninsular MY: n=48, Langkawi: n=138) (b) testes weight (CCNR: n=31, Pulau Ubin: n=37, Central Peninsular MY: n=21, Langkawi: n=122) and (c) sperm length (CCNR: n=22, Pulau Ubin: n=21, Central Peninsular MY: n=8, Langkawi: n=39).