A phylogenetic approach to the study of sexual size dimorphism in Felidae and an assessment of Rensch´s rule.

Cats and dogs cross the line: domestic breeds follow Rensch’s rule, their wild relatives do not

“…Our results have shown that two emblematic domesticated species, the dog and the cat follow a sexual dimorphism trend in size that conforms to the empirical pattern known as Rensch's rule which is not present at the interspecific level in their respective families (Martínez et al, 2014;Bidau, Martínez, 2016). We have also demonstrated that in dogs, body size variation and SSD between breeds vary more than in the Canidae as a whole, while cats show a much lower size variation than that of the Felidae but SSD variation between breeds is comparable to that of the whole family.…”

“…SSD tends to have low or no phylogenetic signal (Martínez et al, 2014;Stevens, Platt, 2015;Bidau, Martínez, 2016;Martínez, Bidau, 2016), and as said above there is no convincing mechanism to explain Rensch's rule or its frequent inversion. The possible reason is that so many mechanisms are involved in the production of SSD that a single trend in scaling of SSD with body size does not exist.…”

“…In fact, other more constant ecogeographic/evolutionary rules -which are in principle, empirical patterns -such as Bergmann's rule may also be explained in terms of very different ecological factors (Bidau, 2014). It is however noteworthy that very clear cases of Rensch's pattern have been uncovered within species of wide geographic distribution suggesting a relationship between ecogeographic body size variation and the degree of SSD (Blanckenhorn et al, 2006;Bidau, Martí, 2008a;Martínez, Bidau, 2014;Werner et al, 2016).…”

“…SSD is not a species trait comparable to body size which can be measured in kilograms or milligrams or in units of length: it is an unitless statistical parameter that varies according to the measurement used to estimate size (e. g. body mass and length in canids; Bidau, Martínez, 2016). Measurements of SSD using two different proxies for body size (e. g. mass and length) may or may not be not statistically correlated (e. g. correlation in felids, lack of correlation in canids; Martínez et al, 2014;Martínez, Bidau, 2016). It is not surprising that, differently from body size, SSD frequently does not show phylogenetic signal.…”

“…The study of body size and SSD evolution through domestication in dogs and cats is highly relevant for four important reasons: (i) our previous comparative studies have demonstrated that canids and felids do not follow Rensch's rule at the crossspecies level and that the two families greatly differ from each other in their levels of SSD in relation with their different reproductive strategies and social systems. Felids are polygynic and show high levels of male-male competition to access females, thus sexual selection favours large male size and increased SSD while canids are essentially monogamous, sexual male-male contests are rare and sexual selection does not favor exaggerated body size of males, hence lower SSD (Martínez et al, 2014;Bidau, Martínez, 2016); (ii) because in domestic breeds size and SSD are not only a consequence of natural or sexual selection in their wild ancestors but also of self-domestication, artificial and unconscious selection along their domestication pathways, changes in both traits could be expected since body size (thus, SSD) is extremely sensible to an enormous set of ecological and evolutionary factors. Changes in SSD could also be reflected in the presence or absence of Rensch's rule; (iii) it has been shown for dog and cat breeds that body size is negatively associated with lifehistory traits such as longevity (Galis et al, 2007;Greer et al, 2007;OʼNeill et al, 2015) and, in cats SSD is correlated with retroviral infections and age at maturity (Pontier et al, 1998); and (iv) both domestic species include many breeds with large variation in body size and the data are easily accessible.…”