Reconstructing genetic mating systems in the absence of parental information in colonially breeding waterbirds

Abstract

BackgroundDNA-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.ResultsMulti-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.ConclusionsWe 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.

Conspecific Brood Parasitism in the White‐faced Ibis Plegadis chihi (Aves: Pelecaniformes) Revealed by Microsatellites' Based Kinship‐Reconstruction

“…CBP has already been reported in other waterbirds, including some of the same family as the white‐faced ibis (listed by Yom‐Tov, ), and also in seabirds such as the wiskered tern (Paillisson et al, ). The few studies based on genetic data available for waterbirds also reported deviation from monogamy within broods in natural populations of the roseate spoonbill, the wood stork, and the great egret (Miño et al, ). In addition, genetic evidence supported the occurrence of CBP in other birds, such as the northern lapwing (Grønstøl et al, ), the black‐headed gull (Ležalová‐Piálková, ), and the black‐capped chickadee (Otter et al, ).…”

“…CBP has recently been studied using molecular techniques, which allowed researchers to more profoundly explore the role of kin selection in the evolution of this behavior (see references in Eadie and Lyon, ). Colonial waterbirds represent an especially interesting group in which to study reproductive behavior (Miño et al, ) because nesting in colonies is one of the breeding habits proposed to promote CBP (Brown, ; Møller and Birkhead, ; Lyon and Everding, ; Brown and Lawes, ). Although the literature on mating systems in colonially breeding waterbirds is still notably scarce (Miño and Del Lama, ), the few genetic studies available on this group have proposed that both EPP and CBP can occur in natural populations (e.g., Lyon and Everding, ; Miño et al, ).…”

Extra-pair paternity in the socially monogamous white stork (Ciconia ciconia) is fairly common and independent of local density

“…First the program ML-Relate 56 was used to determine the most likely relationship between nestling pairs using a maximum likelihood approach. Then the hypothesis testing tool, based on simulations, was used to determine statistically significant relationships between pairs in a manner similar to that used in Miño et al 19. (see Supplementary Fig.…”

“…Genetic methods allow us to overcome the potential shortcomings of purely observational studies when determining a given species’ mating system81314. Despite the wide-spread occurrence of social monogamy across avian species, recent research has found strict genetic monogamy to be the exception rather than the rule (e.g 2356789151617181920…”

Polymorphic heterologous microsatellite loci for population genetics studies of the white-faced ibis Plegadis chihi (Vieillot, 1817) (Pelecaniformes, Threskiornithidae)

“…1The study by Miño et al (2011) refers to nine microsatellite loci, whereas that by Van Den Bussche et al (1999) refers to four loci, also mentioned in Eo et al (2010).2Original reference: McGuire and Noor (2002).3Original references: Goostrey et al (1998) and Piertney et al (1998).…”