Thursday, September 19, 2013

Legless lizards

Legless lizards, represented by more than 200 species worldwide, are well-adapted to life in loose soil. Fascinatingly, lizards on five continents independently lost their limbs in order to burrow more quickly into sand or soil, making them a great textbook example for convergent evolution. Some still have vestigial legs. Though up to 20 cm in length, these reptiles are rarely seen because they live mostly underground, eating insects and larvae, and may spend their lives within an area of one square meter. 

In an earlier genetic study of the California legless lizard (Anniella pulchra) researchers revealed five deep genetic lineages:
These genetic lineages of Anniella are diagnosable with two independently evolving markers (mt and nuDNA), showing that these lineages are, or were historically, independently evolving. Some of the newly discovered lineages are restricted to a few marginal sites in one of the most heavily impacted and degraded regions of California, the San Joaquin Valley. The recognition of several restricted-range lineages of a rare and declining taxon, within a region characterized by intense historical and ongoing habitat destruction, has important conservation implications.

Now, four years later the same researchers describe four new species. Three of the genetic lineages discovered in 2009 can be readily diagnosed through a combination of coloration, scalation, and skeletal characters (trunk vertebra number). A fourth lineage is cryptic, but can be distinguished from the other species by its karyotype, which of course is a bit tedious and makes DNA barcoding more attractive. By the way in the original study a part of COI was also used to determine the lineages. 

The colleagues named the new species after four legendary UC Berkeley scientists: the founder of the  Museum of Vertebrate Zoology at UC Berkeley,  Joseph Grinnell, the paleontologist Charles Camp, philanthropist and amateur scientist Annie Alexander and herpetologist Robert C. Stebbins, at 98 the only one of those still alive.

The former Anniella pulchra, a species of special concern, is now divided into five species. This means A. pulchra has a smaller distribution than previously recognized, thereby enhancing concern about its conservation status. The remaining four species have even smaller ranges, some of which are degraded or threatened by human activities. Whereas much of the range of Anniella stebbinsi is already compromised by urban development, the conservation implications for the other three new species are even more striking because of their very limited distributions. Anniella grinnelli is known from a few sites in the southern San Joaquin Valley, an area that has been greatly modified by urban and agricultural development. Anniella grinnelli persists in small patches within the Bakersfield city limits, but some of the populations we collected were extirpated by development during the course of this study. The type locality at the Sand Ridge Preserve is a secure site that will help ensure the species survival. Anniella alexanderae is known from two sites at the base of the Temblor Mountains, and should be considered rare pending further study. Finally, Anniella campi is known from just three sites. This species may be restricted to the vicinity of potentially fragile springs in canyons that open into the Mojave Desert and so warrants careful monitoring.

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