TY - JOUR
T1 - Digit ratios have poor indicator value in a wild bird population
AU - Ruuskanen, S.
AU - Helle, S.
AU - Ahola, M.
AU - Adamczyk, F.C.A.
AU - Möstl, E.
AU - Laaksonen, T.
N1 - Reporting year: 2011
Metis note: 5046; WAG; AnE
PY - 2011
Y1 - 2011
N2 - Early androgen exposure is known to have longlasting
effects on phenotype, behaviour and even fitness,
but difficulties in measuring the exposure hinders the study
of its importance in evolutionary context. Digit ratios have
been highlighted as a potential easy-to-measure indicator of
early steroid exposure, as they have been suggested to
reflect steroid, mainly testosterone levels during prenatal
development. However, evidence for digit ratios reflecting
early steroid levels is weak, as experimental studies,
especially in wild populations, are scarce. We studied the
association between maternally derived yolk androgens and
digit ratios (2D:4D, 2D:3D and 3D:4D) using both
correlative data and a rather high level of experimental
elevation of yolk androgens in a passerine bird, the pied
flycatcher (Ficedula hypoleuca). We also examined whether
digit ratios have indicator value in an evolutionary
context by studying correlations between digit ratios and
reproductive traits, secondary sexual traits and exploratory
behaviour. We did not find any association between digit
ratios and yolk androgen level either in correlative or
experimental data. Digit ratios were neither related to any
of the reproductive and secondary sexual traits or exploratory
behaviour measured. There was, however, a sex
difference in 2D:3D and 3D:4D of adult birds (due to
second and fourth digits being shorter in females), which
was not apparent in fledglings or captivity-raised juveniles.
This suggests that either the sex difference may develop as
late as during the sexual maturation for breeding. These
results indicate that, in this species, digit ratios are not
reliable markers of maternally derived yolk androgen
exposure and that they bear little relevance as correlates
of the adaptive traits we measured.
AB - Early androgen exposure is known to have longlasting
effects on phenotype, behaviour and even fitness,
but difficulties in measuring the exposure hinders the study
of its importance in evolutionary context. Digit ratios have
been highlighted as a potential easy-to-measure indicator of
early steroid exposure, as they have been suggested to
reflect steroid, mainly testosterone levels during prenatal
development. However, evidence for digit ratios reflecting
early steroid levels is weak, as experimental studies,
especially in wild populations, are scarce. We studied the
association between maternally derived yolk androgens and
digit ratios (2D:4D, 2D:3D and 3D:4D) using both
correlative data and a rather high level of experimental
elevation of yolk androgens in a passerine bird, the pied
flycatcher (Ficedula hypoleuca). We also examined whether
digit ratios have indicator value in an evolutionary
context by studying correlations between digit ratios and
reproductive traits, secondary sexual traits and exploratory
behaviour. We did not find any association between digit
ratios and yolk androgen level either in correlative or
experimental data. Digit ratios were neither related to any
of the reproductive and secondary sexual traits or exploratory
behaviour measured. There was, however, a sex
difference in 2D:3D and 3D:4D of adult birds (due to
second and fourth digits being shorter in females), which
was not apparent in fledglings or captivity-raised juveniles.
This suggests that either the sex difference may develop as
late as during the sexual maturation for breeding. These
results indicate that, in this species, digit ratios are not
reliable markers of maternally derived yolk androgen
exposure and that they bear little relevance as correlates
of the adaptive traits we measured.
U2 - 10.1007/s00265-010-1099-5
DO - 10.1007/s00265-010-1099-5
M3 - Article
SN - 0340-5443
VL - 65
SP - 983
EP - 994
JO - Behavioral Ecology and Sociobiology
JF - Behavioral Ecology and Sociobiology
IS - 5
ER -