We examined the degree of reproductive isolation in four populations of Triatoma mexicana Herrich-Schaeffer from Mexico along with fertility and the segregation of morphological characteristics in two generations of offspring from crosses between these populations. The percentage of couples with (fertile) offspring was high among all sets of crosses between cohorts from Peñamiller, Meztitlán, and Orizabita. It was low in crosses involving a cohort from Tierra Blanca, mainly in crosses with Meztitlán. Among sets of crosses involving Tierra Blanca specimens, whole first-generation (F1) individuals were morphologically similar to the specimens from other locations. All F1 individuals of crosses involving Peñamiller looked like Peñamiller. However, in crosses between F1 and F1 progeny of parental crosses, alleles for size, overall color, length of head, ante and post ocular distance, and humeral angle apparently had Mendelian dominant/recessive relationships. The cohorts from Peñamiller and Meztitlán seemed to be dominant with respect to Orizabita and Tierra Blanca. Results indicated that cohorts from Peñamiller, Meztitlán, and Orizabita were not reproductively isolated. In contrast, Tierra Blanca was reproductively isolated from the other three populations of T. mexicana and is apparently undergoing an early divergence process of speciation for allopatry.

Graphical Abstract