Gallotia - Systematics and Biogeography

Systematics and Biogeography

This genus can be divided into two groups - basal lineages and a western clade - based on mtDNA cytochrome b and 12S rRNA sequence analysis and agreeing with a common pattern of radiation in the Canarian archipelago (Maca-Meyer et al. 2003). Both contain very large and small species.

The basal taxa cannot be resolved in their phylogenetic position to each other and the western clade. Given that G. atlantica is a small and G. stehlini a giant species, and that it is also not known when exactly the later evolved its large size, the ancestral lizards which colonized the central and western islands may have been still small or already large.

As the western clade contains a lineage of small and another one of larger species, size changed drastically at least twice in this genus. Moreover, it is not fully resolved in how far the western islands' giant species are related to each other either, as only limited material of G. auaritae has been available for phylogenetic analyses (Maca-Meyer et al. 2003). Thus, there presently exists no satisfying, parsimonious model for evolution of giant size in this genus. In the western clade alone, giant size may be a plesiomorphy (and lost again in caesaris and galloti), a synapomorphy (and lost again in intermedia), or several autapomorphies (evolving independently in goliath and the simonyi group) in regard to the ancestral lizards which colonized the western Canaries.

In any case, in historic and late prehistoric times the three westernmost islands (La Palma, La Gomera, and El Hierro) and Gran Canaria held one large and one small species. Tenerife, largest of the islands, additionally has the appropriately-named intermedius, whereas before the modern introductions no large species were known to occur on the two easternmost islands (Lanzarote and Fuerteventura). It is well possible however that remains of extinct giant forms will eventually be discovered there too, given that the successful introduction of G. stehlini to Fuerteventura suggests a vacant ecological niche was present there.

Prehistoric remains were assigned to the taxa G. goliath and G. maxima, the former supposedly occurring on several islands, the latter only on Tenerife. It was eventually determined, however, that G. maxima is a junior synonym of G. goliath, and that the latter was very close to G. simonyi; supposed goliath specimens from El Hierro, La Gomera, and La Palma are probably just extremely large individuals of, respectively, G. simonyi, G. bravoana, and G. auaritae (Barahona et al. 2000). However, a mummified giant specimen from Tenerife yielded ancient DNA remains, and by analysis of this, it was concluded that G. goliath is a valid species that probably was restricted to Tenerife, and apparently was closer to G. intermedia than to G. simonyi (Maca-Meyer et al. 2003).

Basal group

• Gallotia atlantica - Atlantic Lizard
  • Gallotia atlantica atlantica
  • Gallotia atlantica delibesi
  • Gallotia atlantica ibagnezi
  • Gallotia atlantica laurae
  • Gallotia atlantica mahoratae
• Gallotia stehlini - Gran Canaria Giant Lizard

Western clade
Large species

• Gallotia simonyi
  • Gallotia simonyi simonyi - Roque Chico de Salmor Giant Lizard, extinct (c.1930s)
  • Gallotia simonyi machadoi - El Hierro Giant Lizard
• Gallotia bravoana - La Gomera Giant Lizard, formerly G. (simonyi) gomerana and G. simonyi bravoana (Miras & Pérez-Mellado 2005a)
• Gallotia auaritae - La Palma Giant Lizard
• Gallotia goliath - Tenerife Giant Lizard, subfossil; includes G. maxima
• Gallotia intermedia - Tenerife Speckled Lizard

Small species

• Gallotia caesaris - Boettger's Lizard
  • Gallotia caesaris caesaris
  • Gallotia caesaris gomerae
• Gallotia galloti - Tenerife Lizard or Western Canaries Lizard
  • Gallotia galloti eisentrauti
  • Gallotia galloti galloti
  • Gallotia galloti insulanagae
  • Gallotia galloti palmae