Figure 5.

Reproduction and sex determination systems in three parthenogenetic lizards with different sex-determining systems. (a) Aspidoscelis with male heterogamety (XX/XY): all-female diploid hybrids (AB, left) normally reproduce parthenogenetically; rare fertilization by gonochoristic parental species' males (right) leads to ploidy elevation to a new XXX-triploid parthenogenetic form (X-sperm) but possibly to rare or inviable XXY-males (right, Y-sperm); inferred from Moritz & Bi [41]. (b) Darevskia with female heterogamety under a recessive w chromosome: occasional fertilization of a diploid parthenogenetic hybrid Zw female by sperm with a dominant male Z factor from a gonochoristic species leads to sterile triploid ZZw intersex genotypes; redrawn from Spangenberg et al. [197]. (c) Heteronotia with female heterogamety under a dominant W chromosome: occasional fertilization of allotriploid parthenogenetic zzW females (left) by sperm with a recessive male z-factor leads to rare tetraploid zzzW genotypes that also develop into females (right); drawn after Moritz [292]. Lizard silhouettes, their gametes and the resulting offspring are shown; arrows indicate occasional fertilization causing ploidy elevation.