Response to Delibes-Mateos et al. : Pellet size matters

In Rueda et al. [Rueda, M., Rebollo, S., Gálvez-Bravo, L., 2008. Age and season determine European rabbit habitat use in Mediterranean ecosystems. Acta Oecol. 34, 266–273] we used a threshold of 6 mm faecal pellet diameter to differentiate between adult and juvenile European rabbit (Oryctolagus cuniculus) habitat use. Delibes-Mateos et al. designed a housing experiment with 12 adult rabbits and criticised the choice of 6 mm as a threshold to separate adult and juvenile rabbit pellets, claiming that adults can produce pellets both larger and smaller than 6 mm in similar proportions. In response to their criticism we argue the following. The selection of a 6 mm threshold has a bibliographic basis, it is not a new method developed by Rueda et al. and produces consistent results when applied in the field. Assuming that Delibes-Mateos et al. results are accurate, we should have found a greater number of <6 mm pellets than >6 mm, overall and seasonally, which is not the case. We believe that the use of commercial pelleted food, keeping animals isolated in small cages for over a year, and the use of adult rabbits only, makes the experimental design used by these authors not suitable to refute the usefulness of separating rabbit pellets smaller and larger than 6 mm diameter as indicators of changes in the relative abundance of juvenile and adult rabbits in the field. Finally, we agree with the authors that the use of indirect methods of animal aging would require case-specific validation studies; however, we believe these studies should be correctly designed.     

Evidence for epistasis: reply to Trouve et al.

Salathé and Ebert (2003, J. Evol. Biol. 16: 976–985) have shown that the mean logarithmic fitness of Daphnia magna clones declined faster than linearly with increasing inbreeding coefficient F. They interpreted this result as evidence for synergistic epistasis. Trouve et al. (2004, J. Evol. Biol., doi: 10.1111/j.1420‐9101.2004.00755.x) suggested that hybrid vigour could be an alternative explanation for this finding. We use a population genetic model to support the original claim that the marked deviation from linearity cannot be explained without epistasis. We further argue that the relevant reference population is the metapopulation and not the subpopulation. Taken together, we believe that synergistic epistasis between recessive deleterious alleles segregating in the D. magna metapopulation is the most likely explanation for the finding of Salathé and Ebert.     

Book Review: M.K. Razdan; Introduction to Plant Tissue Culture

Plant Cell, Tissue and Organ Culture (PCTOC) -