Figure 3. Molecular phylogeny and lineage trough time plot of dytiscid diving beetles.

(a): Molecular phylogeny with sympatric sister pairs (blue boxes) shown. Red lines indicate terminal branches leading to a subterranean species. It is assumed that somewhere on the branch the colonization of the subterranean environment took place (see also Leys et al 2003). Black lines indicate surface lineages. Green lines indicate subterranean lineages from aquifers outside of the Yilgarn region. These were not used in the analyses. The numbers at the tips of the branches refer to the Yilgarn calcrete aquifer localities as indicated in Figure 1. Posterior probabilities >0.7 of the Bayesian analyses are indicated near the branches. (b): Lineage-through-time (LTT) plot for surface (black) and subterranean (red) lineages demonstrating the presence of twenty or more ancestral surface species during the major radiation of subterranean beetles 3–7 Mya.