Fig. 1

Geographic variation in fig wall thickness and wasp oviposition. a A Ficus hirta fig from Guangzhou in the south-western part of the study region. A pollinating wasp has entered the fig cavity and is ovipositing into the flowers that line the fig cavity. b A Ficus hirta fig from Fujian province, in the north-eastern part of the range of the species. Note the larger size of the fig and the thicker fig wall. c An ovipositing Philotrypesis. The wasp inserts its ovipositor through the fig wall and will only lay an egg if it reaches an ovule colonised by a pollinator larva. d An ovipositing Sycoscapter hirticola. The wasp inserts its ovipositor through the fig wall and will only lay an egg if it reaches an ovule colonised by a pollinator larva. The thick fig walls in the northern eastern part of the range of Ficus hirta represent an evolutionary challenge for the parasitic wasp species which oviposit through the fig wall but not for the pollinator which enters the fig