Figure 4.

Covariation of traits in a guild of plants pollinated by the tanglewing fly Prosoeca ganglbaueri in the Drakensberg mountains (table 1). (a) Coevolution probably accounts for the strong relationship across 16 sites between the proboscis length of P. ganglbaueri and the flower depth of Z. microsiphon (Scrophulariaceae) which is pollinated almost exclusively by this fly and also its main source of nectar. (b) On the other hand, a similar relationship involving the orchid Disa nivea must be due to trait-tracking as this species is non-rewarding and thus unlikely to influence the evolution of the fly proboscis. Modified from Anderson et al. (2005) and Anderson & Johnson (2008, 2009).