Laboratório de Genética de Aves, Departamento de Genética e Evolução, Universidade Federal de São Carlos, São Carlos, 13565-905 São Paulo, Brazil.
BMC Evol Biol. 2011 Jul 8;11:196. doi: 10.1186/1471-2148-11-196.
DNA-based studies have demonstrated that avian genetic mating systems vary widely, with many species deviating from long-assumed monogamy by practicing extra-pair paternity and conspecific brood parasitism. Colonially breeding waterbirds provide interesting models in which to investigate this question because they show nesting habits proposed to promote alternative reproductive strategies. However, little is known about the genetic mating systems of this group of birds, mainly due to difficulties in obtaining genetic data from incubating adults at nests that are necessary for conducting conventional parentage studies. Here, we inferred kinship patterns among offspring in broods of three co-distributed waterbird species, Wood Stork (Mycteria americana), Roseate Spoonbill (Platalea ajaja) and Great Egret (Ardea alba egretta), to investigate genetic mating system in the absence of parental data.
Multi-step analyses combining estimates of relatedness coefficients, formulation of relationship-hypotheses, significance testing of alternative hypotheses, and maximum-likelihood sibship reconstruction techniques revealed evidence that alternative reproductive strategies may be present in natural populations of Wood Storks and Roseate Spoonbills, whereas relatedness of co-nestlings diagnosed in the Great Egrets did not deviate from a hypothesis of genetic monogamy. Specifically, under this analytical framework, inferred kinship relationships revealed that Great Egret nests contained full-sibling nestlings (100%), with the Roseate Spoonbill (RS) and Wood Stork (WS) exhibiting proportions of half-siblings (RS: 5%) and/or unrelated nestlings (RS: 24%; WS: 70%), patterns consistent with extra-pair paternity and conspecific brood parasitism, respectively.
We provide evidence that genetic monogamy occurs in Brazilian natural breeding colonies of the Great Egret, but is not the sole reproductive strategy employed by the Wood Stork and the Roseate Spoonbill. In fact, extra-pair paternity and conspecific brood parasitism were common in the latter two species, with a combined frequency of 7.5% and 11.3% in Roseate Spoonbill and Wood Stork, respectively. Although geographically co-distributed, differences among these species may be due to variation in their life histories. From a methodological standpoint, the approach implemented here, although not free from limitations, can have broad application for analyzing systems with limited genealogical information and/or in studying similarly challenging organisms in which obtaining genetic data on complete families is problematic.
基于 DNA 的研究表明，鸟类的遗传交配系统差异很大，许多物种通过实施额外的配对父权和同种巢寄生来偏离长期以来被认为的一夫一妻制。殖民地繁殖的水鸟提供了一个有趣的模型来研究这个问题，因为它们表现出的筑巢习惯被认为可以促进替代的繁殖策略。然而，由于从正在孵化的成鸟身上获取进行传统亲子关系研究所需的遗传数据存在困难，因此人们对这群鸟类的遗传交配系统知之甚少。在这里，我们推断了三种分布在同一地区的水鸟物种（美洲鹫、玫瑰琵鹭和大白鹭）的雏鸟中后代之间的亲缘关系模式，以在没有亲代数据的情况下研究遗传交配系统。
结合相关系数估计、关系假设制定、替代假设的显著性检验以及最大似然同胞关系重建技术的多步骤分析表明，替代繁殖策略可能存在于美洲鹫和玫瑰琵鹭的自然种群中，而大白鹭的同巢雏鸟的亲缘关系并没有偏离遗传一夫一妻制的假设。具体来说，在这个分析框架下，推断出的亲缘关系表明，大白鹭巢中包含全同胞雏鸟（100%），而玫瑰琵鹭（RS）和美洲鹫（WS）的半同胞比例（RS：5%）和/或无亲缘关系的雏鸟比例（RS：24%；WS：70%）分别与额外配对父权和同种巢寄生相对应。
我们提供的证据表明，遗传一夫一妻制发生在巴西自然繁殖的大白鹭群体中，但不是美洲鹫和玫瑰琵鹭所采用的唯一繁殖策略。事实上，额外配对父权和同种巢寄生在后两种物种中很常见，玫瑰琵鹭和美洲鹫的发生率分别为 7.5%和 11.3%。尽管在地理上是分布在一起的，但这些物种之间的差异可能是由于它们的生活史不同。从方法学的角度来看，虽然这里实施的方法并非没有局限性，但可以广泛应用于分析遗传信息有限的系统，或者研究在获取完整家族遗传数据方面存在问题的类似具有挑战性的生物。
