Low reproductive skew despite high male-biased operational sex ratio in a glass frog with paternal care.
BACKGROUND
Reproductive skew, the uneven distribution of reproductive success among individuals, is a common feature of many animal populations. Several scenarios have been proposed to favour either high or low levels of reproductive skew. Particularly a male-biased operational sex ratio and the asynchronous arrival of females is expected to cause high variation in reproductive success among males. Recently it has been suggested that the type of benefits provided by males (fixed vs. dilutable) could also strongly impact individual mating patterns, and thereby affecting reproductive skew. We tested this hypothesis in Hyalinobatrachium valerioi, a Neotropical glass frog with prolonged breeding and paternal care.


RESULTS
We monitored and genetically sampled a natural population in southwestern Costa Rica during the breeding season in 2012 and performed parentage analysis of adult frogs and tadpoles to investigate individual mating frequencies, possible mating preferences, and estimate reproductive skew in males and females. We identified a polygamous mating system, where high proportions of males (69 %) and females (94 %) reproduced successfully. The variance in male mating success could largely be attributed to differences in time spent calling at the reproductive site, but not to body size or relatedness. Female H. valerioi were not choosy and mated indiscriminately with available males.


CONCLUSIONS
Our findings support the hypothesis that dilutable male benefits - such as parental care - can favour female polyandry and maintain low levels of reproductive skew among males within a population, even in the presence of direct male-male competition and a highly male-biased operational sex ratio. We hypothesize that low male reproductive skew might be a general characteristic in prolonged breeders with paternal care.
Department of Integrative Zoology, University of Vienna, Althanstrasse 14, A-1090, Vienna, Austria. alexandra.mangold@faktornatur.com.
Alexandra
A
Mangold
Department of Integrative Zoology, University of Vienna, Althanstrasse 14, A-1090, Vienna, Austria. katharina.trenkwalder@gmx.de.
Katharina
K
Trenkwalder
Department of Integrative Zoology, University of Vienna, Althanstrasse 14, A-1090, Vienna, Austria. max.ringler@univie.ac.at.
Max
M
Ringler
Department of Integrative Zoology, University of Vienna, Althanstrasse 14, A-1090, Vienna, Austria. walter.hoedl@univie.ac.at.
Walter
W
Hödl
Messerli Research Institute, University of Veterinary Medicine Vienna, Veterinärplatz 1, A- 1210, Vienna, Austria. eva.ringler@univie.ac.at.
Eva
E
Ringler
D000818:Animals; D049628:Body Size; D003364:Costa Rica; D005260:Female; D008297:Male; D052586:Mating Preference, Animal; D011898:Ranidae / Q000235:genetics / Q000502:physiology*; D012098:Reproduction; D012726:Sexual Behavior, Animal