Reduced Offspring Viability Is Associated With Long-Term Stability of a Narrow Avian Hybrid Zone

Area of Science:

• Evolutionary Biology
• Speciation Research
• Tropical Ecology

Background:

• Hybrid zones offer insights into speciation dynamics.
• Natural hybrid zone studies are scarce, particularly in diverse tropical regions.
• Manakin hybrid zones provide a model for studying speciation processes.

Purpose of the Study:

• Investigate hybrid fitness in a Central American manakin hybrid zone.
• Evaluate adult survival and egg hatching rates in parental and hybrid populations.
• Assess the role of haemosporidian parasites as a selective pressure.

Main Methods:

• Compared adult survival between white-collared (Manacus candei) and golden-collared (M. vitellinus) manakin parental and hybrid populations.
• Estimated egg hatching success rates in nests from hybrid and parental zones.
• Monitored prevalence of Plasmodium and Haemoproteus parasites.

Main Results:

• Adult survival rates were similar across parental and hybrid populations.
• Hatching success was significantly lower in the hybrid population (70% failure) compared to parental species (M. candei 28.6%, M. vitellinus 19.0%).
• Parasite prevalence was uniformly low in all populations.

Conclusions:

• Partial infertility or developmental mortality in hybrid offspring likely contributes to the spatial stability of this manakin hybrid zone.
• Despite introgression of male traits under sexual selection, reduced hybrid viability may limit gene flow.
• Findings highlight unique speciation dynamics in tropical hybrid zones.