Inter- and intra-sexual patterns of fluctuating asymmetry in the red-billed streamertail: should symmetry always increase with ornament size?
✍ Scribed by Matthew R. Evans; Thais L. F. Martins; Michael P. Haley
- Book ID
- 104651541
- Publisher
- Springer
- Year
- 1995
- Tongue
- English
- Weight
- 962 KB
- Volume
- 37
- Category
- Article
- ISSN
- 0340-5443
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✦ Synopsis
Recent work on fluctuating asymmetry has suggested that ornaments should have higher levels of fluctuating asymmetry than (1) non-ornaments and (2) homologous structures in the non-ornamented sex. In addition, as both ornament size and symmetry should increase with individual quality there should be a tendency for ornament symmetry to increase with ornament size. In non-ornaments, a U-shaped relationship between symmetry and size is expected, with the individuals at the extremes being more asymmetrical than individuals around the optimum. We tested these predictions in the red-billed streamertail (Trochilus polytmus), a sexually dimorphic endemic Jamaican hummingbird. The lengths of four bilaterally symmetrical traits (first and second outermost tail feathers, tarsi and wings) in 43 adult males and 42 females were measured. The second outermost tail feathers of adult males (which are elongated into streamers) were absolutely but not relatively more asymmetrical than non-ornaments (including the homologous feathers in females). When character size was controlled for, wings were shown to be relatively more symmetrical than other traits. Symmetry did not increase with increasing trait size in any of the morphological traits measured. There was a U-shaped relationship between asymmetry and trait size for four traits (adult male streamers, adult male wings and female outer tail feathers). These results do not support any of the predic-