Seasonal variations of plasma testosterone among colour-morph common wall lizards (Podarcis muralis).
Sexual steroids influence reproductive behaviours and promote secondary sexual traits. In male lizards, increasing levels of testosterone (T) bolster conspicuous colouration, stimulate territoriality, and trigger antagonistic interactions among rivals. Moreover, in colour polymorphic species, reproductive strategy, aggressiveness and T levels can differ between morphs. Therefore, T level is considered as an important mechanism that regulates the expression of colour polymorphism and sexual behaviours of males. But in the polymorphic territorial wall lizard (Podarcis muralis), a lack of relationship between morphs and aggressiveness challenges the notion that T plays such a role. To examine this issue, we compared adult T levels among three colour morphs (white, yellow and red) through repeated sampling during the mating season. High T levels were observed at the onset of the mating season followed by a significant decrease, a pattern documented in other lizard species. Mean T levels did not differ among morphs. However, yellow males maintained significantly higher T levels over time and displayed a stronger subsequent decline. Overall, in this species, seasonal T patterns differ among morphs, not mean values. Previous studies revealed that T suppresses the immune response; suggesting that a strong initial investment promoted by high T levels may trade-off against immunity (maintenance). Further experimental investigations are required to clarify the relationship between T and reproductive effort in polymorphic species that exhibit complex temporal pattern of T levels.
Dipartimento di Scienze della Terra e dell'Ambiente, Università degli Studi di Pavia, I-27100 Pavia, Italy. Electronic address: roberto.sacchi@unipv.it.
Roberto
R
Sacchi
Museo Civico di Storia Naturale di Milano, Corso Venezia 55, I-20121 Milano, Italy.
Stefano
S
Scali
Museo Civico di Storia Naturale di Milano, Corso Venezia 55, I-20121 Milano, Italy.
Marco
M
Mangiacotti
CIBIO-InBIO, Universidade do Porto, Campus Agrário de Vairão, 4485-661 Vairão, Portugal.
Marco
M
Sannolo
Museo di Storia Naturale dell'Università di Pisa, Via Roma 79, I-56011, Calci (PI), Italy.
Marco A L
MAL
Zuffi
MUSE, Museo delle Scienze di Trento, Corso del Lavoro e della Scienza 3, I-38100 Trento, Italy.
Fabio
F
Pupin
Dipartimento di Scienze della Terra e dell'Ambiente, Università degli Studi di Pavia, I-27100 Pavia, Italy.
Augusto
A
Gentilli
CNRS, Centre d'Etudes Biologiques de Chizé, F-79360 Villiers en Bois, France. Electronic address: bonnet@cebc.cnrs.fr.
Xavier
X
Bonnet
D000374:Aggression / Q000502:physiology; D000818:Animals; D049628:Body Size; D003116:Color; D008116:Lizards / Q000097:blood*; D008297:Male; D010858:Pigmentation; D012621:Seasons; D013739:Testosterone / Q000097:blood*
D013739:Testosterone
Androgens; Hormones; Polymorphism; Seasonal variation