3.2 Reproductive isolation
In both hybrid regions, i.e., north-central and north-western Spain, we
detected strong and asymmetric mechanical reproductive isolation.
In north-central Spain, mechanical
and tactile barriers between I. elegans males and I.
graellsii females impeded 65% of the matings, while between I.
graellsii males and I. elegans females 76% of matings were
impeded. When those barriers were estimated in I. elegansbackcrosses, i.e., between I. elegans males and hybrid females,
barriers impeded 33% of the matings, while between hybrid males andI. elegans females, barriers impeded 75% of matings. More
isolation was detected in I. graellsii backcrosses, betweenI. graellsii males with hybrid females 100% of the copulations
were prevented, but we find no isolation between hybrid males andI. graellsii females (0%) (Figure 2A). The strength of
mechanical and tactile barriers in heterospecific crosses and I.
elegans and I. graellsii backcrosses in north-western Spain are
given in Figure 2B [data from (Arce-Valdés, Ballén-Guapacha,
Chávez-Rios, & Sánchez-Guillén, under review; Sánchez-Guillén et al.,
2012)].