The island syndrome in lizards
Article first published online: 22 AUG 2012
© 2012 Blackwell Publishing Ltd
Global Ecology and Biogeography
Volume 22, Issue 2, pages 184–191, February 2013
How to Cite
Novosolov, M., Raia, P., Meiri, S. (2013), The island syndrome in lizards. Global Ecology and Biogeography, 22: 184–191. doi: 10.1111/j.1466-8238.2012.00791.x
- Issue published online: 7 JAN 2013
- Article first published online: 22 AUG 2012
- Alon Fellowship
- Clutch size;
- island biogeography;
- island syndrome;
- life history;
- population density;
- reversed island syndrome
Islands are thought to promote correlated ecological and life-history shifts in species, including increased population density, and an infrequent production of few, large, offspring. These patterns are collectively termed ‘the island syndrome’. We present here the first, phylogenetically informed, global test of the ‘island syndrome’ hypothesis, using lizards as our model organisms.
We assembled a database containing 641 lizard species, their phylogenetic relationships, geographic ranges and the following life-history traits: female mass, clutch size, brood frequency, hatchling body mass and population density. We tested for life-history differences between insular and mainland forms in light of the island syndrome, controlling for mass and latitude, and for phylogenetic non-independence. We also examined the effects of population density and, in insular endemics, of island area, on lizard reproductive traits.
We found that insular endemic lizards lay smaller clutches of larger hatchlings than closely related mainland lizards of similar size, as was expected by the island syndrome. In general, however, insular endemics lay more frequently than mainland ones. Species endemic to small islands lay as frequently as mainland species. Continental and insular lizards have similar productivity rates overall. Island area had little effect on lizard reproductive traits. No trait showed association with population density.
Island endemic lizards mainly follow the island syndrome. We hypothesize that large offspring are favoured on islands because of increased intra-specific aggression and cannibalism by adults. Stable populations on islands lacking predators may likewise lead to increased intra-specific competition, and hence select for larger hatchlings that will quickly grow to adult size. This view is supported by the fact that lizard populations are denser on islands – although population density per se was uncorrelated with any of the traits we examined.