Bird sex-typing using genetic markers

The team in Sheffield has identified markers for the genetic sexing of over 150 species of birds (Dawson 2005, Dawson et al. 2015, Dawson et al. 2016) and supported multiple studies involving bird sex-typing.

We have assessed the utility of published sex-typing markers (Dawson et al. 2016)  and created a web-based database (see below) of the most suitable methods to sex-type different species.

We have also developed new sex-typing markers:

• Marker Z37B is suitable for sex-typing birds from degraded samples and samples of low quantity (Dawson et al. 2015).
• Marker Z43B is able to sex species that have been problematic to sex with other markers (Dawson et al. 2016).
• Markers Z002A, Z002B, Z002C, Z002D, Z002E (Dawson 2007) - a suite of 5 markers based on the ZSWIM6 gene that are able to sex most birds.

Database

We have assessed the utility of two commonly used published sex-typing markers (Griffiths et al. (1998: P2/P8) and Fridolfsson and Ellegren (1999: 2550F/2718R)).

In addition to the species we have sex-typed here at Sheffield, data was very kindly contributed from many researchers - we added all this data, along with the published original data, to the database.

The Bird sexing database Dawson, 2005 (MS Excel, 124kB) includes a list of ~130 bird species (non-passerines and passerines) which have been sexed and the sexing primer sets which were used. The database and details of the technical methods and protocols used are provided in this document (Word, 32kB).

Potential sources of error when sex-typing birds

We would also like to draw attention to the potential sources of error in misinterpreting molecular sexing data caused by the presence of Z allele polymorphism, such as that identified in auklets (Dawson et al. 2001) and other species (Dawson et al. 2015) leading to real males being misassigned as female. Heteroduplexes are rarer but can also occur, and lead to sexing error (Casey et al. 2009). Also see the review of error in bird sexing by Robertson and Gemmell (2006).

References

Dawson DA, Darby S, Hunter FM, Krupa AP, Jones IL and Burke T (2001) A critique of CHD-based molecular sexing protocols illustrated by a Z-chromosome polymorphism detected in auklets (Aves: Alcidae, Laridae). Molecular Ecology Notes, 1, 201–204.

Dawson DA, Brekke P, dos Remedios N, Horsburgh GJ (2015) A marker suitable for sex-typing birds from degraded samples. Conservation Genetics Resources,  7, 337–343 [Open Access].

Dawson DA, dos Remedios N, Horsburgh GJ (2016) A new marker based on the avian spindlin gene that is able to sex most birds, including species problematic to sex with CHD markers. Zoo Biology, 35, 533–545. [Open Access]

Bruford MW, Hanotte O, Brookfield JFY, Burke T (1998) Multilocus and single-locus DNA fingerprinting. In: Molecular Genetic Analysis of Populations: A Practical Approach, 2nd edition, (ed. Hoelzel AR), pp. 287-336. IRL Press, Oxford.

Dawson DA (2005) Bird sexing database: Identifying suitable sex-typing markers for over 100 bird species. http://www.shef.ac.uk/nbaf-s/databases/birdsexing

Fridolfsson AK and Ellegren H (1999) A simple and universal method for molecular sexing of non-ratite birds. Journal of Avian Biology, 30, 116-121.

Griffiths R, Double MC, Orr K and Dawson RJG (1998) A DNA test to sex most birds. Molecular Ecology, 7, 1071-1075.

Casey AE, Jones KL, Sandercock BK, Wisely SM (2009) Heteroduplex molecules cause sexing errors in a standard molecular protocol for avian sexing. Molecular Ecology Resources, 9, 61-65.

 

Robertson BC & Gemmell NJ (2006) PCR-based sexing in conservation biology: Wrong answers from an accurate methodology? Conservation Genetics 7 (2), 267-271.