Photo by: Yu Zeng, Oct 2009, Berkeley
Yu Zeng, is an IB Grad student who works on wing evolution and flight biomechanics in stick insects in the Wake and Dudley Labs.
On a hill to the north of Berkeley, a young Yellow-eyed Ensatina (Ensatina eschscholtzii xanthoptica) just woken up after the first rain of another rainy season. As a member of the lungless salamander family Plethodontidae, they only use the skin for respiration, having have lost their lungs during evolution. Connecting their nostrils and upper lips are a pair of shallow grooves (nasolabial grooves), which allow them to sample chemical signals from wet substrate. The ancestors of Ensatina were from Oregon and Washington. When they gradually migrated towards south, different subpopulations evolved unique morphological features associated with local adaptation.
This particular example, with orange skin and bright yellow eyes, is a mimic of the Western Newt (Taricha sp.), a very poisonous species that lives in the same habitat with Ensatina around the Bay Area. Subpopulations of Ensatina continued towards the south and formed a ring around the Central Valley in California. The continuous pattern in morphological and genetic variation around the ring-like geographic distribution clearly demonstrates an incipient species formation event.