0000000000540084
AUTHOR
Eduardo Aparici
Sex Allocation in Haplodiploid Cyclical Parthenogens with Density‐Dependent Proportion of Males
Departament de Microbiologia i Ecologia, Universitat de Birky and Gilbert 1971; Wallace and Snell 1991), which Valencia, E46100-Burjassot (Valencia), Spain includes an asexual (amictic) and a sexual (mictic) phase, the diapausing form being the sexually produced resting Submitted September 22, 1997; Accepted April 21, 1998 egg. Habitat colonization begins when the resting eggs hatch and emerge from the sediments. With these hatchlings, the amictic phase starts, which is a repeated sequence of amictic females parthenogenetically produc
Variability for mixis initiation in Brachionus plicatilis
Deductions from both evolutionary models and inductive argumentation from empirical data support the notion of intraspecific variability for the initiation of sexual reproduction (mixis) within rotifer populations. In this study, we focus on the time and density at which mixis is initiated in a growing population. Cyclical parthenogenetic clones of Brachionus plicatilis established by hatching of resting eggs, isolated from a natural habitat, have been tested at the start of their sexual phase. Clones exhibited great variation for this trait, their time of switching to sexual reproduction being correlated with population density. Most of the variation for mixis initiation has either low or …
When to be sexual: sex allocation theory and population density-dependent induction of sex in cyclical parthenogens
The timing of sex is a critical fitness component in the cyclically parthenogenetic life-cycle of rotifers. It has been hypothesized that sex in rotifers is optimally timed to high population density because male‐female encounters are more probable. Because sexual females produce either males or, if inseminated, diapausing eggs, the advantage of a higher male‐female encounter rate is that allocation to male production can be lower. This is paradoxical in the context of the sex allocation theory developed for rotifers, as the theory predicts equal numbers of male-producing and diapausing-egg producing females. We investigated this paradox using both empirical data and theoretical analysis. L…
Evidence for an even sex allocation in haplodiploid cyclical parthenogens
Recent theoretical work has shown that haplodiploid cyclical parthenogens, such as rotifers, are expected to have an equal frequency of male-producing and resting-egg producing females during their sexual phase. We tested this prediction by following sexual reproduction dynamics in two laboratory populations and one field population of the rotifer Brachionus plicatilis through two growing seasons. We recorded population density, proportion of sexual females, and sex allocation (the proportion of male-producing sexual females as a fraction of total sexual females). We found this sex allocation ratio to vary from 0.3 to 1.0 in single sampling events. However, when we computed sex allocation b…