Experimental evidence that sperm maturation drives protandry in an ectotherm.
Protandry, i.e., the earlier arrival to breeding areas of males than females, has attracted a lot of scientific attention. However, evidence for the evolutionary hypotheses of protandry is surprisingly scarce. Here, we experimentally manipulate the time of emergence from hibernation of males, relative to females, in the common lizard, Zootoca vivipara. We test whether the timing of emergence affects sperm maturation and mating success, to disentangle among proposed selective advantages of protandry. Our results experimentally demonstrate that the timing of emergence affects the date of sperm presence. Moreover, the degree of protandry affected whether males had sperm upon their first encounter with females, but it did not affect the probability of copulating. Mating occurred independent of male fertility and mating during infertility was least common in early emerging males. Early emergence from hibernation by males, relative to females, thus increases the male's chance of fertilising eggs and later emergence from hibernation by females reduces the female's probability of mating with infertile males. These results point to direct reproductive benefits of protandry in males and females, where earlier emergence is predicted to increase the male's opportunities to inseminate mates, and later emergence reduces the female's probability of copulating with infertile males. This suggests that protandry evolved due to the time required for sperm maturation after emergence from hibernation.
Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales (MNCN-CSIC), C/ José Gutiérrez Abascal 2, 28006, Madrid, Spain. merelbreedveld@mncn.csic.es.|Instituto Pirenaico de Ecología (IPE-CSIC), Avda. Nuestra Señora de la Victoria 16, 22700, Jaca, Spain. merelbreedveld@mncn.csic.es.
Merel C
MC
Breedveld
Department of Biodiversity and Evolutionary Biology, Museo Nacional de Ciencias Naturales (MNCN-CSIC), C/ José Gutiérrez Abascal 2, 28006, Madrid, Spain.|Instituto Pirenaico de Ecología (IPE-CSIC), Avda. Nuestra Señora de la Victoria 16, 22700, Jaca, Spain.|Department of Ecology and Evolution, University of Lausanne, Biophore, 1015, Lausanne, Switzerland.|Fundación Araid, Edificio CEEI Aragón, C/ María de Luna 11, 50018, Zaragoza, Spain.
Patrick S
PS
Fitze
D000818:Animals; D005075:Biological Evolution; D008297:Male; D012098:Reproduction; D019849:Sex Determination Processes; D013079:Sperm Maturation; D013094:Spermatozoa
Infertile copulations; Moulting; Sperm maturation; Waiting cost hypothesis; Zootoca vivipara