Protein Fingerprinting: A New Technique Reveals Extensive Conspecific Brood Parasitism

Abstract

Conspecific brood parasitism occurs in many birds and some insects, fishes, and amphibians. Here, we develop and test a novel molecular technique for ecological analysis, protein fingerprinting (PF), based on isoelectric focusing electrophoresis (IEF) in immobilized pH gradients. It is applied here to albumen from birds' eggs and permits accurate identification of eggs laid by different females. This technique greatly clarifies female alternative reproductive tactics and laying patterns in brood‐parasitic Common Goldeneye ducks Bucephala clangula. A small, nondestructive sample of albumen is taken through a hole drilled through the eggshell, which is then sealed with superglue, preserving egg hatchability. IEF yields a rich pattern of albumen bands with extensive variation among females. Observation and video recording of egg‐laying by 21 color‐marked females showed that they had unique band patterns, which were fully repeatable within and between years. Brood parasitism occurred in two‐thirds (13 of 19) of the video‐recorded nests of color‐ringed females, with up to five parasitic females per nest. Of 234 eggs, 36% were laid by females other than the incubating host. These results suggest that intraspecific brood parasitism is more common and important than suggested by earlier studies using traditional methods. Protein fingerprinting yields individual resolution similar to that of a DNA multilocus fingerprinting probe, and has several advantages. The albumen band pattern represents only the laying female, not her mate(s), making it easy to determine the maternity of eggs, and to identify a parasite that spreads her eggs among a number of nests. Albumen can be sampled as soon as the egg is laid, before predation or other losses occur, maximizing sample size and minimizing bias. Protein fingerprinting is relatively inexpensive and easy. It is also useful for several purposes other than maternity determination, such as relatedness estimation for categories of individuals.

Analysis of extra‐pair paternity and conspecific brood parasitism in mallards Anas platyrhynchos using non‐invasive techniques

“…Nevertheless, despite this limitation, non‐invasive sampling is suitable for estimating individual reproductive success. The combination of non‐invasive sampling and other methods, such as protein fingerprinting (Andersson and Åhlund 2001) and estimation of CBP based on egg morphology (Pöysä et al 2009), might in part overcome these drawbacks.…”

Family living among birds

“…Conspecific brood parasitism can be the result of joint laying by related females in a kin‐structured population of females formed as the result of limited dispersal, like among ducks. When the parasite is a relative, the cost to the host is mitigated by inclusive fitness gains from being related to offspring hatched from parasite eggs (Andersson and Åhlund 2000, 2001). Thus, the parasitism will produce related offspring, and hence select for within‐brood cooperation.…”

Molecular identification of brood-parasitic females reveals an opportunistic reproductive tactic in ruddy ducks

“…We also collected egg albumen from 126 eggs from 20 nests found during laying or early incubation (1–3 days). To collect albumen, we punctured a small hole through the egg shell, removed approximately 200–300 μL of egg albumen with a syringe (Andersson & Åhlund 2001), and then sealed the hole with Aron Alpha Instant Krazy Glue ® (ethyl cyanoacrylate). Albumen samples were immediately stored on ice, and placed at −20 °C until protein fingerprint analysis.…”

“…Egg albumen is of maternal origin, and exclusively represents the genotype of the female that laid the egg rather than that of the developing embryo. Andersson & Åhlund (2001) demonstrated that protein bands are both reproducible and genetically polymorphic across females, providing resolution sufficient to detect parasitic eggs and sometimes the females who laid them.…”

“…All gels were run on an Amersham Biosciences Multiphor II System with electrophoresis power supply EPS 3501 and a cooling temperature of 10 °C. Dehydrated gels were stored at −20 °C and rehydrated in a solution containing reagents to maximize number and sharpness of the bands according to Andersson & Åhlund (2001). The pH ranges used were 4–7 (type C) and 4.5–5.4 (type B + D) (Andersson & Åhlund 2001).…”