Beschreibung:
<p>A recent publication (de Fraipont, Clobert, and Barbault-Evolution 50:391-400, 1996) reached two heterodox conclusions concerning the evolution of reproductive modes in squamate reptiles. Firstly, "reversals" from viviparity back to oviparity have been almost as frequent as "forward transitions" of oviparity to viviparity. Secondly, maternal egg-guarding has not facilitated the evolution of viviparity. However, methodological problems in the analysis make these conclusions tenuous. In particular, the analysis (1) relied upon poorly supported (as well as strongly supported) transitions, (2) counted particular transitions more than once, (3) placed too much emphasis on differences between very distantly related higher taxa, and (4) contained consistent biases in the raw data, so that many egg-guarding taxa must have been incorrectly scored as lacking egg-guarding. A reanalysis of the (family-level) data reveals little support for reversals from viviparity back to oviparity while the relationship (if any) between egg-guarding and viviparity cannot be ascertained without additional data.</p>