Sex Roles Are Not Always Reversed When the Potential Reproductive Rate Is Higher in Females

1999 ◽  
Vol 153 (5) ◽  
pp. 540-548 ◽  
Author(s):  
Noboru Okuda
Keyword(s):  
Sex Roles ◽  
Reproductive Rate ◽  
Potential Reproductive Rate

Reproduction of Euastacus bispinosus Clark (Decapoda:Parastacidae), and trends in the reproductive characteristics of freshwater crayfish

1995 ◽  
Vol 46 (2) ◽  
pp. 485 ◽  
Author(s):  
JA Honan ◽  
BD Mitchell
Keyword(s):  
Breeding Season ◽  
Generation Time ◽  
Carapace Length ◽  
South Australia ◽  
River System ◽  
Reproductive Rate ◽  
Freshwater Crayfish ◽  
Size At Sexual Maturity ◽  
Western Victoria ◽  
Potential Reproductive Rate

The reproductive biology of Euastacus bispinosus populations was studied in a river and a creek of the Glenelg River system in south-western Victoria, and a small coastal creek in south-eastern South Australia. Females produced eggs in the first breeding season after maturation of their gonopores. At the Victorian sites, E. bispinosus spawned in early May, carrying eggs for about seven months before hatching and juvenile release in October-December. At least 95% of mature females at each Victorian site carried eggs during the breeding season. Mature females had relatively broader abdomens than did males and carried between 63 and 812 eggs. The number of eggs carried was linearly related to both occipital carapace length and abdomen width. The South Australian population differed from the Victorian populations in having a smaller mean size at sexual maturity for females (occipital carapace length 58 mm compared with 85-86 mm in Victoria), a higher proportion (17%) of gonopore abnormalities (< 1% in Victoria), and relatively wider abdomens (which continued to broaden after maturity). Euastacus bispinosus is a winter brooder and has a long generation time and low potential reproductive rate, characteristics it shares with Astacopsis and Parastacoides species, and members of the Astacidae. Other crayfish species (e.g. Cherax species and members of the Cambaridae) are summer brooders and tend to have a high potential reproductive rate and short generation time.

scholarly journals Polyandry as a mediator of sexual selection before and after mating

2013 ◽  
Vol 368 (1613) ◽  
pp. 20120042 ◽  
Author(s):  
Charlotta Kvarnemo ◽  
Leigh W. Simmons
Keyword(s):  
Sexual Selection ◽  
Mating Success ◽  
Multiple Mating ◽  
Reproductive Rate ◽  
Male Mating ◽  
Before And After ◽  
Main Driver ◽  
Future Work ◽  
Potential Reproductive Rate

The Darwin–Bateman paradigm recognizes competition among males for access to multiple mates as the main driver of sexual selection. Increasingly, however, females are also being found to benefit from multiple mating so that polyandry can generate competition among females for access to multiple males, and impose sexual selection on female traits that influence their mating success. Polyandry can reduce a male's ability to monopolize females, and thus weaken male focused sexual selection. Perhaps the most important effect of polyandry on males arises because of sperm competition and cryptic female choice. Polyandry favours increased male ejaculate expenditure that can affect sexual selection on males by reducing their potential reproductive rate. Moreover, sexual selection after mating can ameliorate or exaggerate sexual selection before mating. Currently, estimates of sexual selection intensity rely heavily on measures of male mating success, but polyandry now raises serious questions over the validity of such approaches. Future work must take into account both pre- and post-copulatory episodes of selection. A change in focus from the products of sexual selection expected in males, to less obvious traits in females, such as sensory perception, is likely to reveal a greater role of sexual selection in female evolution.

Potential reproductive rate of a sex-role reversed pipefish over several bouts of mating

2009 ◽  
Vol 78 (3) ◽  
pp. 747-753 ◽  
Author(s):  
Sunny K. Scobell ◽  
Adam M. Fudickar ◽  
Rosemary Knapp
Keyword(s):  
Sex Role ◽  
Reproductive Rate ◽  
Potential Reproductive Rate

The population dynamics of a tropical possum, Trichosurus vulpecula arnhemensis Collett

1998 ◽  
Vol 25 (2) ◽  
pp. 171 ◽  
Author(s):  
J. A. Kerle
Keyword(s):  
Home Range Size ◽  
Reproductive Rate ◽  
Food Sources ◽  
Brushtail Possum ◽  
Trichosurus Vulpecula ◽  
The Core ◽  
Eucalypt Forest ◽  
Dry Tropics ◽  
Ready Availability ◽  
Potential Reproductive Rate

The population ecology of Trichosurus vulpecula has been studied extensively in temperate Australia and in New Zealand. This paper provides the results of a trapping study of a population of the northern brushtail possum (T. vulpecula arnhemensis Collett 1897) in the wet–dry tropics of Australia’s Northern Territory. Possums were readily trapped and the population had a comparatively high density for Australian brushtails of around 3 per hectare. The core home-range size and range length for males was 1.12 ha and 165 m; this was a little larger than for females (0.89 ha and 155 m). The possums were not very agressive when handled and were apparently quite socially tolerant. The ready availability of nutritious food sources throughout the year enables them to breed continuously, producing 1.7 young per year per adult female. If environmental conditions become unfavourable with a series of poor wet seasons or frequent fires, the habitat will resemble the less-productive eucalypt forest not occupied by possums. Mortality of pouch young and immatures will increase under these conditions but with a potential reproductive rate of nearly two per year, populations of the northern brushtail can readily recover from short periods of unfavourable conditions.

Male potential reproductive rate influences mate choice in a bushcricket

1998 ◽  
Vol 55 (6) ◽  
pp. 1499-1506 ◽  
Author(s):  
CHARLOTTA KVARNEMO ◽  
LEIGH W SIMMONS
Keyword(s):  
Mate Choice ◽  
Reproductive Rate ◽  
Potential Reproductive Rate

Female territoriality in a paternal mouthbrooding cardinalfish to avoid predation against spawned eggs

2009 ◽  
Vol 87 (6) ◽  
pp. 508-514 ◽  
Author(s):  
Kayoko Fukumori ◽  
Noboru Okuda ◽  
Yasunobu Yanagisawa
Keyword(s):  
Sex Role ◽  
General Rule ◽  
Reproductive Rate ◽  
Operational Sex Ratio ◽  
Territorial Defense ◽  
Egg Predation ◽  
Breeding Territory ◽  
Female Territoriality ◽  
Mating Opportunities ◽  
Potential Reproductive Rate

Generally, paternal mouthbrooding cardinalfishes are characteristic of sex-role-reversed animals: females have a higher potential reproductive rate and are more active in mating competition than males, and the operational sex ratio (OSR) is female-biased. However, one species of cardinalfish, Apogon notatus (Houttuyn, 1782), shows unusual sex roles: females alone defend their breeding territories to form pairs, even though the OSR is male-biased. This is inconsistent with the general rule that breeding territoriality is shown by the more abundant sex. We examined the function of female breeding territory in this fish using field observations. Prior to the breeding season, large females established their territories earlier than small females. Earlier settlers occupied deeper areas with larger boulders where conspecifics were less likely to aggregate. As the level of conspecific aggregation increased, spawning females suffered from frequent intraspecific interference and subsequent egg predation, leading to increased time or energy spent on territorial defense. For the females, territories that have more boulders and fewer conspecifics might be of higher quality because such places are safe from egg predation and less costly to defend. We conclude that females defend their breeding territories to avoid predation of spawned eggs rather than to guard high-quality mates or to increase mating opportunities.

Temporal and spatial opportunities for polygamy in a monogamous seahorse, Hippocampus whitei

Behaviour ◽  
2004 ◽  
Vol 141 (2) ◽  
pp. 141-156 ◽  
Author(s):  
Karl Evans ◽  
Laila Sadler ◽  
Amanda Vincent ◽  
A. Dale Marsden
Keyword(s):  
Reproductive Rate ◽  
Home Ranges ◽  
Mating Pattern ◽  
Familiarity Effect ◽  
Spatial Constraints ◽  
Males And Females ◽  
Per Se ◽  
Temporal And Spatial ◽  
Reproductive Rates ◽  
Potential Reproductive Rate

AbstractThe sex with the higher potential reproductive rate is expected to mate polygamously unless there are temporal or spatial constraints on mate availability. We investigated whether such constraints were evident in a population of the monogamous seahorse Hippocampus whitei (family Syngnathidae). Across the whole study site, breeding was more asynchronous than expected by chance. Our findings are thus compatible with the hypothesis that asynchronous breeding may promote and/or maintain monogamy. Asynchrony per se was unlikely to explain monogamy entirely, however, as temporal opportunities for polygamy remained and the males that were nearest one another had the lowest level of asynchrony. Moreover, each animal's home range overlapped with home ranges of potential mates other than their partner, implying a lack of spatial constraints on polygamy. We suggest that H. whitei mated monogamously because the benefits of polygamy were reduced by (1) only small differences in the potential reproductive rates of males and females and/or (2) a mate familiarity effect that increased reproductive success in successive matings. Further research could investigate relationships between mating pattern and varying intersexual differences in potential reproductive rates across syngnathid species.

Sign in / Sign up

Export Citation Format

Share Document