Evolutionary Ecology Research, 2012, 14: 353–360
Correlates of genetic diversity in bird nuclear genes
Tangjie Zhang and Qing Liu
College of Veterinary Medicine, Yangzhou University, Yangzhou, China
ABSTRACT
Background: The neutral theory of evolution proposes that diversity is the result of the
accumulation of neutral substitutions. The term ‘neutral’ refers to a gene (or a genomic locus)
that has no or almost no effect on fitness. The main hypotheses that would account for neutral
genetic diversity are related to life-history traits.
Question: Is there a relationship between nuclear neutral diversity in birds (class Aves) and
their life-history traits, including generation time, metabolic rate, longevity, and body mass?
Data: 752 groups of polymorphisms from 104 nuclear genes in 297 species of Aves belonging
to 53 genera and 15 families. Data were taken from the Polymorphix database and the Popset
database of GenBank.
Search method: We used logistic regression analysis and phylogenetic regression of independent variables to analyse the relationship between Watterson’s estimator (θw) of weighted
neutral sites and life-history variables, including generation time, body mass, and maximum
longevity. We performed multiple regression analysis of multiple traits and natural selection
efficiency. We measured natural selection efficiency as θn /θz + i .
Conclusions: Aves nuclear neutral diversity, represented by the mutation parameter, θw, was
significantly negatively correlated with generation time. The other variables – metabolic rate,
longevity, and body mass – did not correlate with nuclear neutral variation.
Keywords: birds, generation time, molecular evolution, mutation, nuclear genes.
INTRODUCTION
Genetic diversity in organisms is variable. Interpreting the degree of genetic diversity from
diverse life and population histories can be difficult, as the mechanisms and processes that
regulate that diversity are complex and poorly understood. Three main hypotheses have
been advanced to explain variation in DNA substitution rate: generation time (Laird et al., 1969;
Wu and Li, 1985; Li, 1997), metabolic rate (Martin et al., 1992; Martin and Palumbi, 1993; Nunn and Stanley, 1998),
and longevity (Denham, 1957; Barja and Herrero, 2000). Researchers have tested these three hypotheses
by correlating diversity with relevant life-history variables.
DNA substitution rate has been widely used for studies of genetic diversity. However, an
accurate estimation of mutation rate is required for complicated molecular data, which
Correspondence: Tangjie Zhang, College of Veterinary Medicine, Yangzhou University, Yangzhou 225009, China.
e-mail: [email protected]
Consult the copyright statement on the inside front cover for non-commercial copying policies.
© 2012 Tangjie Zhang
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