Excerpts from Jim Conrad's
from the April 11 2010 Newsletter issued from Hacienda Chichen Resort beside Chichén Itzá Ruins, central Yucatán, MÉXICO
Also during my banana hike back from Pisté I heard rustling among dry leaves beside the road and was tickled to see a lizard about eight inches long (20 cm), with his narrow, longitudinal lines slightly resembling our racerunners and skinks up North, seen above.
Again in Campbell's book it was easily identifiable as the Yucatán Whiptail, CNEMIDOPHORUS ANGUSTICEPS. Yucatán Whiptails are endemic to the Yucatán Peninsula, northern Guatemala and east-central Belize, so it a petty good find, even though the species is considered common in the northern Yucatán.
Yucatán Whiptails, I learn from Campbell, do some tricky things with their genes. It happens that sometimes female Yucatan Whiptails mate with a completely different species, the Deppe's Whiptail Cnemidophorus deppei. Offspring of these pairings produce populations that may or may not constitute yet a third species, depending on how you define "species." Whether the populations represent a third species or not, the individuals are "parthenogenetic." By parthenogenetic is meant that the populations consist of nothing but females who give birth to only females without the benefit of males. Offspring are genetic clones of their mothers.
Parthenogenesis is relatively common in invertebrates but rare among vertebrates. Most experts assume that parthenogenetic species have arisen fairly recently in evolutionary time, and won't last long now that they're here. One reason for that is that populations with very little genetic diversity can't evolve the usual ways to adapt to changing environments.
Sex exists for a reason, the geneticists say.