Figure 1.

Sampling locations and crossing schematic used for this study. (a) Collection sites of M. nasutus are represented by open circles, M. guttatus by black circles, and sympatric sites by grey circles. (b) Table of allopatric crosses: cells containing an ‘X’ indicate that reciprocal F₁ and F₂ hybrids were generated between the two populations (or that pure-species experimental populations were created), while a blank cell indicates that no cross was performed. (Sympatric populations were only crossed with each other.)