Linking intronic polymorphism on the CHD1‐Z gene with fitness correlates in Black‐tailed Godwits Limosa l. limosa

Abstract

We show that variation in an intronic length polymorphism in the CHD1‐Z gene in Black‐tailed Godwits Limosa l. limosa is associated with fitness correlates. This is the second example of the CHDZ‐1 gene being correlated with fitness, a previous study having established that Moorhens Gallinula chloropus carrying the rare Z* allele have reduced survival. In Godwits, however, carriers of the Z* allele (374 bp) fared better than those with the more frequent Z allele (378 bp) with respect to body mass, plumage ornamentation, reproductive parameters and habitat quality. The Z* allele was found in 14% of 251 adult birds from nature reserves, but was absent from 33 birds breeding in intensively managed agricultural lands. Males and females with the Z* allele had less extensive breeding plumage, and females had a higher body mass, bred earlier and had larger eggs. There were no significant differences in annual survival between birds with and without the Z* allele. DNA isolated from museum skins demonstrated that this polymorphism was present at low frequency in 1929. We speculate that strong asymmetrical overdominance may explain the low frequency of the Z* allele and that genetic linkage to causal genes might be an explanation for the phenotypic correlations. Our findings suggest a degree of cryptic genetic population structuring in the Dutch Godwit population.

Mortality within the annual cycle: seasonal survival patterns in Afro-Siberian Red Knots Calidris canutus canutus

“…Red Knots captured during 2002-2006 were sexed with primers P2/P8 (Griffiths et al 1998; verified for Red Knots by Baker et al 1999). To avoid potential sexing errors due to length polymorphisms in the Z-introns of the CHD-gene (Casey et al 2009;Schroeder et al 2010), Red Observation effort was greatest during the winter expeditions and lower but comparable between late summer and spring (Table 1). Late summer/early autumn expeditions were timed to coincide with the Red Knots' return period from the breeding grounds (Piersma et al 1992), but an unknown percentage of Red Knots might not yet have returned when we concluded our observations in late September.…”

Repeatable timing of northward departure, arrival and breeding in Black-tailed Godwits Limosa l. limosa, but no domino effects

“…The few cases of re-nesting detected (n = 3) were excluded from the present analysis. Adults were sexed on the basis of plumage and body size , later verified by molecular assays using blood samples collected when they were caught (Schroeder et al 2010a). …”

Small-scale demographic structure suggests preemptive behavior in a flocking shorebird

“…Red knots captured in 2002-2006 were sexed with primers P2/P8 (Griffiths et al 1998), which were verified for red knots by Baker et al (1999). To avoid sexing errors due to potential length polymorphisms in the Z-intron of the CHD gene (Casey et al 2009;Schroeder et al 2010), primers 2602F/2669R (Fridolfsson and Ellegren [1999], modified for shorebirds by O. Haddrath, unpublished data) were used from 2007 onwards.…”