Sexual size dimorphism in the evolutionary context of facultative paedomorphosis: insights from European newts.
BACKGROUND
Sexual size dimorphism (SSD) is a key evolutionary feature that has been studied in many organisms. In a wide range of species, this pattern is more complex because of polymorphism within each sex. However, it is not known whether the magnitude and direction of SSD could be affected by alternative developmental trajectories within sexes. Our aim was to test whether an intrasexual polymorphism, facultative paedomorphosis (a process in which the development of somatic and gonadal tissues differs in alternative morphs), could affect SSD variation patterns in European newts.


RESULTS
We report here the first evidence that SSD varies depending on the paedomorphic or metamorphic ontogenetic pathway. In species with a consistent female-biased SSD, paedomorphosis decreased the SSD level, but did not affect its direction. In species with moderate female-biased SSD or variable SSD patterns, paedomorphosis changed the magnitude, or both the magnitude and the direction, of SSD.


CONCLUSIONS
Our study highlights the importance of developmental processes for shaping SSD patterns in populations in which contrasting life-history pathways evolved. European newts express different SSD patterns depending on their developmental pathway (i.e., metamorphosis versus paedomorphosis), as well as their species and population. These findings emphasize the importance of studying alternative morphotypes, which are found in a wide range of animal groups, to understand the evolution of SSD.
Denoël
Mathieu
M
Laboratory of Fish and Amphibian Ethology, Behavioural Biology Unit, University of Liège, 22 Quai van Beneden, 4020 Liège, Belgium. Mathieu.Denoel@ulg.ac.be
Ivanović
Ana
A
Dzukić
Georg
G
Kalezić
Milos L
ML
D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D005260:Female; D008297:Male; D012455:Salamandridae / Q000196:embryology / Q000235:genetics* / Q000502:physiology; D012727:Sex Characteristics; D013045:Species Specificity