Allometry of sexual size dimorphism in domestic dog.
BACKGROUND
The tendency for male-larger sexual size dimorphism (SSD) to scale with body size - a pattern termed Rensch's rule - has been empirically supported in many animal lineages. Nevertheless, its theoretical elucidation is a subject of debate. Here, we exploited the extreme morphological variability of domestic dog (Canis familiaris) to gain insights into evolutionary causes of this rule.


RESULTS
We studied SSD and its allometry among 74 breeds ranging in height from less than 19 cm in Chihuahua to about 84 cm in Irish wolfhound. In total, the dataset included 6,221 individuals. We demonstrate that most dog breeds are male-larger, and SSD in large breeds is comparable to SSD of their wolf ancestor. Among breeds, SSD becomes smaller with decreasing body size. The smallest breeds are nearly monomorphic.


CONCLUSIONS
SSD among dog breeds follows the pattern consistent with Rensch's rule. The variability of body size and corresponding changes in SSD among breeds of a domestic animal shaped by artificial selection can help to better understand processes leading to emergence of Rensch's rule.
Department of Zoology, Faculty of Science, Charles University in Prague, Prague, Czech Republic.
Daniel
D
Frynta
Jana
J
Baudyšová
Petra
P
Hradcová
Kateřina
K
Faltusová
Lukáš
L
Kratochvíl
D000818:Animals; D049628:Body Size / Q000502:physiology*; D004285:Dogs; D005260:Female; D008297:Male; D012727:Sex Characteristics