Sign up for EduLifeDesks
Lilford's Wall Lizard is endemic to the Balearic Islands off the coast of Spain, where it is found only on small islands with no human inhabitants. There are 27 subspecies of this lizard (see "Distribution" for a full listing). Podarcis lilfordi is a diurnal medium sized lacertid lizard with active foraging behavior. It is omnivorous and is known to be both a pollinator and seed disperser, as well as an insectivore.
Seed dispersal: As a fruit eater, Podarcis lilfordi consumes and disperses the seeds of of many plants on the islands it inhabits via defecation. Podarcis lilfordi is thought to be a seed disperser of 16 plant species, and is the only known seed disperser of Daphne rodriguezii on Colom Islet. The lizard prefers bigger fruits of this species and its movement of the seeds to the shade of non-Daphne shrubs is very important for the plant's propagation. It is also thought to be an important seed disperser of the rare Withania frutescens and the olive relative Phillyrea media. Lilford's Wall Lizard has a particularly interesting association with Dracunculus muscivorus, an aroid found on Aire Islet in the Balearics that emits a fetid smell to attract carrion flies for pollination: the lizard will perch on these plants to eat the carrion flies that visit the flower. This is the only lacertid lizard that is known to take advantage of a plant-pollinator interaction in this way. When this plant fruits, the fruits constitute a large portion (53%) of Podarcis lilfordi's diet. The lizard's feces contain intact seeds, suggesting that the lizard may be a legitimate seed disperser for this aroid.
Pollination: Podarcis lilfordi is a known legitimate pollinator for a few plant species, including the spurge shrub Euphorbia dendroides. The lizard moves large quantities of pollen within and among plants, effectively cross-pollinating flowers in the process. Spurges are normally pollinated by insects, but this species flowers when insects are not abundant in the Balearic Islands, and its flowers are visited three times more frequently by this lizard than by insects. However, there is no evidence that flower traits are under pollinator-mediated selection in this system. Lilford's Wall Lizard also drinks the nectar of Chrithmum martitimum in the late summer and incidentally transfers pollen between Dracunculus flowers.
Parasites: Podarcis lilfordi is associated with at least eleven helminths, including two digenea (Paradistomum mutabile and Barachylaima), eight nematodes (Skjabinodon, Spauligodon, Parapharynogodon, Skrajabinelazia, Abbreviata, Acuaria, and Spirurida), and one acanthocephalan (Centrorhynchus).
Podarcis lilfordi is not a territorial lizard and is an active forager. It basks in sunlight to increase its body temperature. Kleptoparasitism (stealing of food) is known to occur between individuals in this species. This is observed most frequently at high lizard densities.
Escape Behavior: When an approaching predator is detected, these lizards adopt an alert stance by extending their legs just prior to fleeing. Typically, they do not attempt to flee until a potential predator is within 3 m. Lilford's Wall Lizard has the ability to drop its tail (a process called autotomy) to evade predation, and the tail may later be regenerated. Studies have shown that lizards with regenerated tails wait until a potential predator is significantly closer before fleeing than lizards that have not previously lost their tails. The escape behavior of Lilford's Wall Lizard is dependent on whether or not it is eating. It waits longer, flees further, and returns faster when feeding, and these responses are further dependent on the size of the food source.
Podarcis lilfordi is an endangered species that has disappeared from the larger islands in the Balearics due to predation. It is now restricted to smaller islands in this archipelago. Because of the high population densities and energy requirements of this species (see "Physiology"), it is particularly susceptible to declines as a result of increased competition from introduced herbivores and insectivores.
Podarcis lilfordi is listed on Annex II of the Bern Convention, Appendix II of CITES, and as Endangered by the IUCN. These conservation listings are due to increased habitat fragmentation and declining quality and size of suitable habitat. The total area of extent is less than 5,000km2 and its area of occupancy is less than 500km2. Podarcis lilfordi occurs in protected areas, including Parque Nacional de Cabrera and the Parques Naturales de Dragonera and Albufera des Grau. Public education programs focusing on the importance of protecting this species are ongoing.
Podarcis lilfordi is listed as Endangered on the IUCN Red List of Threatened Species for reasons related to the small and declining size of its habitat. Populations are declining.
Podarcis lilfordi was originally found throughout the Balearic Islands off the coast of Spain. After substantial declines associated with human activity on the major islands, this species can only be found on small islands that lack human inhabitants. There is substantial morphological differentiation, particularly in body size, among island populations. This has resulted in the description of the following 27 subspecies, many of which are restricted to a single island.
Podarcis lilfordi can be found in densities above 12,000 individuals per hectare. This is one of the highest reported densities for a lizard species.
Lilford's Wall Lizard used to be widespread in the Balearic Islands, but is now restricted to smaller satellite islands without human development. Morphologically unique subspecies have emerged on many of these isolated islands.
As shown by a phylogeograhic analysis (Terrasa et al., 2009), this species can be broken down into four major evolutionary lineages. One is comprised of populations from 16 islets off the coast of Menorca and another is comprised of populations from four islands off the coast of western Mallorca. The other two lineages overlap in distribution. The four lineages are estimated to be at least 2.8 million years old and there is currently no (or very little) gene flow between them. There is also genetic differentiation below this level, with many isolated populations representing unique haplotypes. This information can be used to guide the designation of evolutionarily significant units (ESUs) for conservation purposes.
A phylogeny of Podarcis and related genera (Brown et al., 2008) shows that the genus is a natural (i.e., monophyletic) group and that P. lilfordi's closest relative is P. pityusensis, another Balearic endemic. These species are allied to species from Sardinia and Corsica, rather than northern Africa, suggesting a northern ancestry. Their radiation is probably tied to paleogeography of the Mediterranean. There are fossils of the P. lilfordi/pityusensis complex that date to the Pliocene/Pleistocene. Divergence between these two species occurred before the end of the Pliocene (2.6 million years ago). The evolution of these two species was shaped by geologic events, as well as climatic and sea level changes. Following speciation, these two species came back into contact.
Lilford's Wall Lizard lives in an area of Mediterranean climate with shrubby vegetation and a rocky landscape. The species used to be widespread, but it is now restricted to the smaller islands of the Balearics where there are no human inhabitants. Here they live at tremendous population densities. These islands range in size from 0.1 to 1155 hectares. Many of these islands are host to their own morphologically unique subspecies of Podarcis lilfordi.
Podarcis lilfordi is a medium-sized lizard that reaches a maximum of 80 mm in snout-to-vent length (range: 50 - 80 mm). Body mass ranges between 4.2 and 9.5 g. The body shape of P. lilfordi is characteristic of lacertids in general. Color is variable among subspecies, and variation exists between juveniles and adults and and among sexes within a subspecies. The color variation across the Balearic archipelago may be the result of founder effects on each of the islands where the wall lizard is now found (i.e., genetic drift). Dorsal color ranges from uniformly brown or green, to green with dark spots, to entirely black. Adult males are often blue to deep blue ventrally. Juveniles are always brown dorsally and pale ventrally, and often change their coloration in adulthood.
Autotomy: Many lizards can "self-amputate" the tail as a defense mechanism (i.e., against a predator), a process called autotomy. The movement of a dropped tail is controlled by the conversion of glycogen into lactate. The concentration of glycogen and lactate in Lilford's Wall Lizard is similar to concentrations in other lizards with this trait, and is not related to the amount of time the tail spends moving after autotomy. The duration of this movement, however, is related to the degree of predation pressure on each island.
Field Metabolic Rates: Field metabolic rates of Podarcis lilfordi are higher than for comparable lizard populations due to higher population densities and high individual energy expenditures owing to an active foraging lifestyle. In one study, 77% of total respiratory metabolism was from activity: this species spends approximately 12 hours a day of foraging due to the low availability of food.
Podarcis lilfordi females produce 2-4 eggs per clutch with an average egg mass of 0.63 g. This corresponds to many fewer, but much larger eggs than other European lacertid lizards, consistent with a trade-off in life history traits often seen in island lizards. The size of the clutch produced by a given female is independent of her body size. The egg size of a given clutch is related to the number of eggs laid. Females can lay multiple clutches in one season. Hatchlings average 32 mm and 0.77 g, which is also larger than in other European lacertids.
Lilford's Wall Lizard is classified as Endangered by the IUCN. Its range has been greatly diminished by the presence of an introduced lizard to the larger islands of the Balearics. It is sensitive to further invasions of predators to the satellite islands on which it now occurs, including domestic cats and non-native lizards. It is also threatened by habitat loss and habitat-use change, including overgrazing by goats. In addition, illegal capture for the pet trade threatens this species. Because of the small population sizes and restricted ranges of this species, it is inherently at risk.
Populations are declining.
Podarcis lilfordi, a true omnivore, alters its trophic strategy according to the availability of food sources, eating vegetative plant material, nectar or fruits when they are available and insects when they are abundant. It is thus both a primary and secondary consumer.
Encyclopedia of Life Learning + Education Group | Museum of Comparative Zoology | Harvard University
26 Oxford Street, Cambridge, MA 02318 USA | 617-496-6764 | education [at] eol.org
© 2009 Encyclopedia of Life - Except where otherwise noted, content on this site is licensed under
a Creative Commons Attribution 3.0 United States License.