This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
Once again, I have squamate guilt. For a while now I’ve been planning to discuss the lacertid lizard fauna of Europe (or, the European Field Guide Region, or Western Palaearctic, or whatever). European people tend to think of our lacertids as small, boring brown things (bar the few big green species). That might be true but, even so, there are loads of neat species here that have fascinating evolutionary interactions, exhibit surprising and often mostly overlooked behaviour and ecological specialisations, and possess anatomical details that might be surprising if you don’t know lizards in details (like tridentate teeth and a paedomorphic skull shape). I don’t have time for the sort of grand, over-arching review that I’d like to produce (sigh) so I’ll try and deal with them in piecemeal fashion. Today: Psammodromus!
Psammodromus is a strictly terrestrial lacertid that frequents flat, typically stony or sandy areas and hillsides in Spain, Portugal and northern Africa (there are also small populations in France, Italy, and elsewhere).
Between 6 and 12 Psammodromus species are recognised depending on which source you consult, but the only ones ever discussed in books are the Large psammodromus Psammodromus algirus [adjacent image by Jack ma] and Spanish psammodromus or sand racer P. hispanicus. The former reaches 27 cm in total (though SVL is only 7 cm) and hence is not small for a European lacertid. Males have bright blue, dark-edge shoulder spots and red or orange throats and cheeks during the breeding season.
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Small, widely spaced, dense, bushy plants that are frequently twiggy or spiny (so-called garigue-type vegetation) form the dominant flora in the areas inhabited by these lizards (Arnold 1987). Perhaps because selection pressures have improved their ability to frequently take refuge in such dense, spiny vegetation, Psammodromus lizards have a streamlined head and large, overlapping cephalic scales. Indeed, Arnold (2004) noted that Psammodromus possesses several features – including a reduced collar and enlarged, overlapping, keeled dorsal and lateral body scales – indicating that it belongs to a ‘dense vegetation’ ecomorph that has evolved several times within Lacertidae. Psammodromus shares its habitat with Lacerta and Acanthodactylus species but they are often larger and take bigger prey (Arnold 1987). The colubrid snake Coronella girondica is a documented predator of Psammodromus (Pérez-Mellado et al. 1997).
Where does Psammodromus fit within the lacertid radiation? Molecular analyses recover it as the sister-taxon to the large Gallotia lizards (Fu 2000, Carranza et al. 2004), in which case it’s outside of Lacertinae and belongs to Gallotiinae. Psammodromus and Gallotia also share detailed anatomical features (including hemipenial characters) and both reportedly make squeaking noises (Arnold 1989) that have even been described as “shrill whistles” (Laňka & Vít 1986).
Several authors have argued that some of the more recently evolved lacertine lacertid clades (Podarcis being the ultimate example) have replaced or displaced the members of older lacertid lineages across Europe, pushing these older lineages into refugia or causing their wholesale extinction. As a member of Gallotiinae, Psammodromus has been hypothesised to be one of these older lineages: you might argue that its current range (southwestern Europe and northwestern Africa) indicates restriction to the peripheries (Carranza et al. 2004). Was it previously more widespread prior to the diversification and spread of Podarcis and other new-fangled lacertines?
Today, Psammodromus species are threatened by habitat loss - sadly, they are proving harder and harder to find...
So much more to say about European lacertids… until next time! For previous Tet Zoo articles on lacertids, see…
Refs - -
Arnold, E. N. 1987. Resource partition among lacertid lizards in southern Europe. Journal of Zoology 1, 739-782.
- . 1989. Towards a phylogeny and biogeography of the Lacertidae: relationships within an Old-World family of lizards derived from morphology. Bulletin of BritishMuseum of Natural History (Zoology) 55, 209-257
- . 2004. Overview of morphological evolution and radiation in the Lacertidae. In Pérez-Mellado, V., Riera, N. & Perera, A. (eds) The Biology of Lacertid Lizards. Evolutionary and Ecological Perspectives. Institut Menorquí d’Estudis. Recerca 8, 11-36.
Carranza, S., Arnold, E. N. & Amat, F. 2004. DNA phylogeny of Lacerta (Iberolacerta) and other lacertine lizards (Reptilia: Lacertidae): did competition cause long-term mountain restriction? Systematics and Biodiversity 2, 57-77.
Fu, J. 2000. Toward the phylogeny of the family Lacertidae – why 4708 base pairs of mtDNA sequences cannot draw the picture. Biological Journal of Linnean Society 71, 203-217.
Laňka, V. & Vít, Z. 1986. Amphibians and Reptiles. Hamlyn, Twickenham.
Pérez-Mellado, V., Corti, C. & Cascio, P. L. 1997. Tail autotomy and extinction in Mediterranean lizards. A preliminary study of continental and insular populations. Journal of Zoology 243, 533-541.