-
Views
-
Cite
Cite
C. J. Nagelkerke, M. W. Sabelis, Precise control of sex allocation in pseudo‐arrhenotokous phytoseiid mites, Journal of Evolutionary Biology, Volume 11, Issue 6, 1 November 1998, Pages 649–684, https://doi.org/10.1046/j.1420-9101.1998.11060649.x
Close - Share Icon Share
Abstract
Can sex allocation be controlled by haplo‐diploid organisms where both males and females arise from fertilised eggs but males become effectively haploid by paternal genome loss (pseudo‐arrhenotoky)? If so, how does the control of mean and variance of sex allocation compare with haplo‐diploids where males arise from unfertilised eggs (arrhenotoky)? These questions are addressed by experiments with two species of pseudo‐arrhenotokous plant‐inhabiting predatory mites: Typhlodromus occidentalis Nesbitt and Phytoseiulus persimilis Athias‐Henriot (Acari: Phytoseiidae).
It is shown that females conditionally adjust offspring sex ratio in response to the presence of conspecifics or their cues. The sex ratios are precise in that their variance is less than expected from a binomial distribution. Because eggs are produced one‐by‐one at regular intervals, it is not possible to designate separate clutches, thus rendering conventional clutch‐based estimates of precision inadequate. To remedy this a range of time scales was investigated and this showed an increase in precision with time scale (and hence “clutch” size). Markovian analysis of son‐daughter sequences showed that this increase arises only if the predator “memorizes” the mean sex ratio of all eggs laid before.
Control of mean and variance of sex allocation is selectively advantageous when local mating groups vary in size and are usually small, as is the case for the phytoseiid mites under study. Predictions of the optimal sex ratio from local mate competition models were in agreement for T. occidentalis. However, P. persimilis, exhibited a stronger female bias than predicted. We suggest that this may be due to selection levels operating at a larger spatial scale than the local mating group.
Control of sex allocation seems as good as in arrhenotokous arthropods, suggesting that — in this respect — pseudo‐arrhenotoky is not at a disadvantage compared to arrhenotoky.
