Long Kira M, Braun Michael J, Muñoz Abrego Adolfo, Jaramillo Ovidio, Jones Todd M, Brawn Jeffrey D
Program in Ecology, Evolution and Conservation Biology University of Illinois Urbana-Champaign Urbana Illinois USA.
Center for Conservation Genomics Smithsonian National Zoo and Conservation Biology Institute Washington DC USA.
Ecol Evol. 2025 Sep 11;15(9):e72120. doi: 10.1002/ece3.72120. eCollection 2025 Sep.
Fitness of hybrid individuals can shape the dynamics of hybrid zones and offer insight into speciation processes. Yet, accounts of hybrid fitness in natural hybrid zones are few, especially from tropical regions where species diversity is high and speciation processes could contrast with those at higher latitudes. We investigated a hybrid zone between the white-collared manakin () and the golden-collared manakin (), two lek-breeding species characteristic of lowland forest habitat in Central America. Despite evidence of asymmetrical introgression and selection on male secondary sexual traits, ongoing sampling indicates that this hybrid zone is spatially stable with narrow clines, thus implying selection against hybrids. To evaluate hybrid viability, we estimated two components of hybrid fitness: survival of adults and egg hatching rates, and a possible selective pressure: prevalence of parasitism by vector-borne haemosporidian parasites. Estimated survival was similar between parental and hybrid populations, and the prevalence of infections by spp. or spp. parasites was uniformly low (4 positive cases, = 268). Estimated rates of hatching success, however, were lower in nests from our hybrid population (one or two eggs failed to hatch in 70% of nests ( = 10)) compared to nests of the parental species ( 28.6% ( = 21) and 19.0% ( = 7)). Thus, despite extensive admixture and clear evidence of introgression of male plumage traits under sexual selection, partial infertility or elevated rates of developmental mortality in hybrid offspring may underlie long-term stability in this hybrid zone.
杂交个体的适合度能够塑造杂交带的动态变化，并为物种形成过程提供见解。然而，关于自然杂交带中杂交适合度的研究却很少，尤其是在物种多样性高且物种形成过程可能与高纬度地区不同的热带地区。我们研究了白领侏儒鸟（）和金领侏儒鸟（）之间的一个杂交带，这两种在求偶场交配的物种是中美洲低地森林栖息地的特征物种。尽管有证据表明存在不对称渐渗以及对雄性第二性征的选择，但持续的抽样表明，这个杂交带在空间上是稳定的，具有狭窄的渐变群，因此意味着对杂交个体存在选择作用。为了评估杂交个体的存活力，我们估计了杂交适合度的两个组成部分：成年个体的存活率和卵孵化率，以及一种可能的选择压力：媒介传播的血孢子虫寄生虫的寄生率。亲本种群和杂交种群的估计存活率相似，并且感染疟原虫属或疟原虫属寄生虫的比例一直很低（4例阳性，=268）。然而，与亲本物种的巢相比，我们杂交种群的巢中估计的孵化成功率较低（70%（=10）的巢中有一个或两个卵未能孵化）（分别为28.6%（=21）和19.0%（=7））。因此，尽管存在广泛的混合以及性选择下雄性羽毛性状渐渗的明确证据，但杂交后代的部分不育或发育死亡率升高可能是这个杂交带长期稳定的基础。
