Figure 2

Histogram distribution of the relative frequency (%) in δ¹³C_{carbon source} values for all taxa in the five SE Asian faunas, following a chronological sequence from the oldest (left) to the youngest (right). Each bin represents a spacing of 1‰. Shaded areas represent δ¹³C_{carbon source} values associated with closed-canopy forests (δ¹³C_{carbon source} < −27.2‰); intermediate rainforests and woodland biomes (δ¹³C_{carbon source} >  − 27.2 ‰ and < − 21.3 ‰; and savannah-like environments (δ¹³C_{carbon source} > − 15.3‰). The white area (δ¹³C_{carbon source} > − 21.3 ‰ and < − 15.3 ‰) consists of values resulting from the combined consumption of both C₃ and C₄ resources, and does not correspond to any specific ecological environment. The dashed red line represents the mean δ¹³C_{carbon source} value in each site.