Differences in Incubation Length and Hatchling Morphology among Five Species of Oviparous Phrynocephalus Lizards (Agamidae) from China

We incubated eggs of five Phrynocephalus species (P. albolineatus, P. axillaries, P. grumgrzimailoi, helioscopus and P. przewalskii) at three constant temperatures (24 degrees C, 28 degrees C and 32 degrees C) to examine differences in incubation length and hatchling morphology among species and among temperature treatments. We combined data from this study with those reported previously for P frontalis and P versicolor to examine whether embryonic stage at laying is a causal factor for interspecific variation in incubation length, and whether the phylogenetic relationship inferred from hatchling morphology is consistent with the relationship based on mitochondrial DNA data. Mean values for incubation length differed among the five species studied herein and, in all these five species, incubation length decreased at a decreasing rate as temperature increased. In none of the five species did hatchling size (snout-vent length and body mass) and other morphological variables differ among the three temperature treatments. The seven oviparous Phrynocephalus lizards found in China differ from each other in hatchling morphology, and embryonic stage at laying is a causal factor of inter- and intra-specific variation in incubation length. The phylogenetic relationship inferred from hatchling morphology is not always consistent with the currently known relationship based on mitochondrial DNA data. Data from this study and those reported previously allow the conclusion that any Phrynocephalus species may have its unique position along the axis defined by hatchling morphology.