Maternal reproductive output and F1 hybrid fitness may influence contact zone dynamics

The outcome of secondary contact between divergent lineages or species may be influenced by both the reproductive traits of parental species and the fitness of offspring; however, their relative contributions have rarely been evaluated, particularly in longer lived vertebrate species. We performed pure and reciprocal laboratory crosses between Ctenophorus decresii (tawny dragon) and C. modestus (swift dragon) to examine how parental reproductive traits and ecologically-relevant offspring fitness traits may explain contact zone dynamics in the wild. The two species meet in a contact zone of post-F1 hybrids with asymmetric backcrossing and predominantly C. modestus mtDNA haplotypes. We found no evidence for reduced parental fecundity or offspring fitness for F1 hybrid crosses. However, maternal reproductive strategy differed between species, irrespective of the species of their mate. Ctenophorus modestus females had higher fecundity and produced more and larger clutches with lower embryon...