Data from: Mating patterns and postzygotic barriers in a hybrid swarm of two closely related pigeon species

Hybrid zones provide a valuable framework for understanding evolutionary
pathways. We investigated mating patterns and reproductive barriers using
captive individuals derived from a natural hybrid swarm between hill
pigeons (Columba rupestris) and feral pigeons (C. livia), maintained under
controlled conditions. Both parental taxa exhibited significant
assortative mating. The observed mating structure suggests that
morphological similarity, mate availability, social interactions, and
genetic relatedness may jointly shape pairing patterns. Reproductive
performance was assessed at three stages—clutch size, hatching, and
fledging—across four cross types (hill pigeon, feral pigeon,
within-hybrid, and heterotypic cross types). Clutch size did not differ
among cross types. Hatchling and fledgling mortality in within-hybrid
crosses and heterotypic crosses did not differ from that in hill pigeon
conspecific crosses. Within-hybrid crosses and heterotypic crosses had
higher hatchling mortality than feral pigeon conspecific crosses, and only
heterotypic crosses showed higher fledgling mortality. Between parental
taxa, hill pigeon conspecific crosses exhibited higher hatchling mortality
than feral pigeon conspecific crosses. These results suggest asymmetric
postzygotic isolation that is most evident in comparisons involving feral
pigeons, with implications for reinforcement of conspecific mate choice in
feral pigeons and continued directional introgression into hill pigeons.