A REVIEW OF REPRODUCTIVE RATES IN STICKLEBACKS IN RELATION TO PARENTAL EXPENDITURE AND OPERATIONAL SEX-RATIOS

Citation
Rj. Wootton et al., A REVIEW OF REPRODUCTIVE RATES IN STICKLEBACKS IN RELATION TO PARENTAL EXPENDITURE AND OPERATIONAL SEX-RATIOS, Behaviour, 132, 1995, pp. 915-933
Citations number
36
Categorie Soggetti
Zoology,"Behavioral Sciences
Journal title
ISSN journal
00057959
Volume
132
Year of publication
1995
Part
13-14
Pages
915 - 933
Database
ISI
SICI code
0005-7959(1995)132:<915:ARORRI>2.0.ZU;2-6
Abstract
1. The expenditures of time and energy on parental activities of femal e and male threespine sticklebacks, Gasterosteus aculeatus L., are rev iewed in the context of sex differences in competition for and choice of mates. 2. The female's parental contribution is mainly cytoplasmic in the form of provisioned eggs. In energy units each clutch spawned r epresents about 200% of the daily maintenance ration of a sexually mat ure female. Each egg in a clutch represents about 2% of that ration. T he 'time out', during which the female is sexually unreceptive between spawnings, varies from about 3 to 15 days, and is inversely correlate d with the rate of food consumption. 3. The male's parental contributi on is primarily behavioural. The daily energy expenditure of a parenta l male is equivalent to a daily ration of about 6% of the male's body weight, a value not dissimilar to that of a reproductively active fema le. The pattern of 'time-outs' of males differs from that of females, with the periods of sexual receptivity and unreceptivity both longer. 4. A crude simulation model of the effect of sex differences in the pa ttern and length of 'time outs' suggested that the operational sex rat io (OSR) would usually be male-biased favouring inter-male competition for mates and mate choice by females. 5. However, both environmental factors such as food availability, and demographic factors such as sex differences in mortality rates, together with the sex differences in 'time out' could cause the OSR to vary within breeding seasons, betwee n breeding seasons and between populations. This leads to the predicti on that there will be corresponding variations in the intensities of m ale-male and female-female competition for males and hence in the deve lopment of secondary sexual characteristics.