Analysing threshold effects in the sexual dynamics of cyclically parthenogenetic rotifer populations
|Title||Analysing threshold effects in the sexual dynamics of cyclically parthenogenetic rotifer populations|
|Publication Type||Journal Article|
|Year of Publication||2011|
|Authors||Serra M, Smith HA, Weitz JS, Snell TW|
Sex in some cyclically parthenogenetic rotifers is triggered when a threshold population density is achieved. In Brachionus, accumulation of a mixis-inducing protein (MIP) that the rotifers excrete into the medium is the proximal signal. Models explicitly accounting for MIP dynamics suggest that either (1) a positive feedback of MIP concentration on MIP production or (2) a switching relationship between the proportion of sexual females and MIP concentration is needed to produce a threshold response of mixis to population density. In order to examine both possibilities, experiments were conducted to estimate the sexual response to a dilution series of medium containing the MIP. The resulting sexual response patterns are consistent with the existence of a threshold response of mixis, but are insufficient to reject one hypothesized mechanism for the threshold response in favor of the other. However, the observed smooth increase of sexual offspring with MIP concentration is consistent with the hypothesis of positive feedback on MIP production, and deserves further investigation.