at Sun Aug 29 15:33:28 2010 [ Report Abuse ] [ Email Message ] [ Show All Posts by CKing ]
>>So, after checking out the californiaherps.com site, it appears that there has been unconfirmed sightings of L.z.zonata in Marin County (north of San Francisco...20 minutes across the Golden Gate bridge). Anyone have anymore information about the accuracy of this notion? I've herped the area before a few times and find some awesome stuff-getula, contia, pitophis, etc.... .
Of course we all know that only actual specimens can be proof that zonata occurs in Marin County. There is however valid arguments against their presence here and in the Mt. Diablo in Contra Costa County (also unconfirmed report there). The argument is based on mtDNA phylogeography. From the mtDNA data, the snakes of the North Bay came orginally from Oregon, but the zonata from San Mateo County came from Santa Cruz/Santa Clara County. Therefore they are opposite ends of a horse shoe shaped distribution for this species and the gap is perhaps as real as a real horse shoe. There is no proof of San Mateo snakes having crossed over to the North Bay and absolutely no proof of North Bay zonata migrating south of the Golden Gate.
Zweifel considered the Mt. Hamiltion specimen as a multifasciata x zonata intergrade based on color pattern, but mtDNA evidence suggests that its closest relative is from the Sierra Nevada foothills. That means the Mt. Hamiltion and adjacent Alamdea County populations are recent migrants, a cross Valley leak. The Mt. Hamilton/Alameda County population is instead L. z. multicincta, not an intergrade animal. It has apparently converged upon multifasciata and zonata on color pattern because of a similar habitat. Since it is a recent migrant, it may not have time to cross the divide between Mt. Hamilton and Mt. Diablo.
Of course, I can be proven wrong if actual specimens are collected from Marin and Contra Costa Counties. Until they are, it is very unlikely they exist in either area on the basis of mtDNA phylogeography.
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