bicanthalis, the lizards from Nopalillo, Hidalgo (OTUs 5-7, locality 5), appear to have reversed from viviparity to oviparity. Among the lizards from Las Vigas, Veracruz, where both parity modes occur, there is no difference in sequence divergence between the single oviparous specimen (OTU 12) and of the viviparous specimens from that location (OTUs 8-11, Table 2).
Another sign test was performed to check if the support for the hypothesis of the reversal of viviparity to oviparity in the S.
jalapae as an outgroup assumed that oviparity was ancestral for the S.
As discussed in the natural history section, the genus Oreina represents the full range of stages in the evolution of viviparity: oviparity, retention of the eggs in the oviducts until hatching with only yolk provided to the embryo, and retention of the eggs in the oviducts combined with matrotrophy by diffusion of nutrients through a reduced chorion (Bontems 1989).
frigida (C) which would have been followed by a reversal to oviparity in the ancestor of O.
frigida combines a condition a priori assumed to be primitive (oviparity) with a seemingly derived one (sequestration) and a third (polymorphism in host family) that suggests the species' placement is between the two major groups of host association in the middle of the genus.
Thus, Fitch (1970) proposed an evolutionary transition from oviparity without egg guarding to viviparity (O[approaches]V) or from oviparity without egg guarding to oviparity with egg guarding (O[approaches]G), whereas Shine and Bull (1979) proposed an alternative scenario implying the evolution sequence from oviparity without egg guarding to oviparity with egg guarding and then to viviparity (O[approaches]G[approaches]V).
We found a maximum of 15 transitions from oviparity without egg guarding (O) to viviparity (V), 10 transitions from oviparity without egg guarding (O) to oviparity with egg guarding (G), 8 transitions from viviparity to oviparity (V[approaches]O), and 5 transitions from viviparity to oviparity with egg guarding (V[approaches]G, Table 2A).