In mammals, clutch size generally decreases with increasing body size [21], thus gigantism is likely to be associated with lower reproductive effort/fewer offspring. In reptiles, on the other hand, large size is associated with larger clutch and litter sizes [39]. Moreover, large insular reptiles may have simply lived for longer [40]. Consequently, we predict RIS applies may apply to dwarf insular mammals and to large insular reptiles.
Finally, we investigated head shape ontogeny in Licosa and mainland P. sicula to test for differences in developmental and growth rates. Ontogeny is particularly relevant here because life history theory predicts a tradeoff between growth and reproduction [21]. Changes in ontogeny may be reflected in adult shape differences because individuals that mature earlier may appear paedomorphic [48]. Paedomorphosis is linked to increased reproductive investment in ephemeral habitats in amphibians [49], and was proposed to drive gigantism in Canary Island lizards Gallotia stehlini and G. simonyi [50] and dwarfism in sauropod dinosaurs [51] and dwarf elephants [52]. On the other hand, positive selection for sexually-selected traits may produce peramorphosis, since sexually selected traits usually appear later in ontogeny [53]. Under RIS, we predicted that the insular lizard (1) develops faster in order to mature early, (2) is more sexually dimorphic as a consequence of strong sexual selection, and (3) has slower growth rate as a consequence of re-allocation of resources from growth into reproduction [21].
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Island Syndrome and RIS describe a number of phenotypic traits that often, but by no means always, change together in insular species. We think one should not expect that all these traits co-occur. For instance, the most obvious trait shift linked to the Island Syndrome (and we argue, to RIS as well) is change in body size. Taking into account possible changes in ontogeny (in the insular species), the relationship between body size and the Island Syndrome may in fact appear weak. Ontogenetic shifts may produce early-maturing, fast-growing small individuals via paedomorphosis. This is suggested to occur in the extinct dwarf elephant Elephas falconeri [52] and in dwarf dinosaurs (e.g. Europasaurus holgeri [79]). Slow growth was found to occur in New Zealand's gigantic moas [80, 81], extinct giant lemurs of Madagascar [82], females of the Licosa Island lizard (this study), and extinct dwarf Balearic goats [[83], but see ref. [84]]. Bunce et al. [85], however, showed that Dinornis Moas were exceptionally dimorphic, and suggested that these birds invested a great deal of energy into egg production. This goes against the Island Syndrome predictions, despite Dinornis being huge even by moa standards.
Spencer et al. [88] emphasized that although growth is expected to be slow when population density is high, rapid growth beyond a critical size reduces predation risk and could be favored (see [22] on Sauromalus). Roth [89, 90] argued that density compensation might explain dwarfism in insular pigmy elephants. Bonaire whiptails live at huge population density, yet the blue morph males allocate a great deal of resources to reproduction, which is consistent with RIS hypothesis [69]. Bonaire whiptails are herbivorous, and so food is not a limiting factor on Bonaire [91]. We remark once more that it is not density (or body size) per se, but the set of ecological conditions favoring either small or large allocation of available resources toward reproduction that produces the Island Syndrome or the RIS, respectively.
Podarcis sicula klemmeri is bright blue (Figure 1c and 1d). Melanism is common in Mediterranean island lizards [95]. Our mainland populations, just opposite the island on Punta Licosa (4015'06.15"N 1454'19.68"E) are invariably normally-colored with the usual green back with white undersides and little blue dots running along the trunk sides that appear brighter during the breeding season. We sampled lizards from Punta Licosa as the reference (mainland) population to compare with the insular population (Figure 1). All experiments described below were performed in accordance with local and national guidelines governing animal experiments (86/609/CEE and its modifications).
The ranges of the plasma parameters for astrophysical compact objects like white dwarfs and neutron stars are very wide. The plasma parameters for white dwarfs and neutron stars are shown in Table 1. The plasma parameters used in our present theoretical analysis correspond to white dwarfs. However, our present theoretical analysis can applied to neutron stars. Therefore, our present results may be useful for understanding the localised electrostatic disturbance in astrophysical compact objects, particularly, in white dwarf and neutron stars.
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