Reversed island syndrome Edit
The term "reversed island syndrome" (RIS) was first used by Pasquale Raia in 2010 to describe the differences in morphology, ecology, physiology and behaviour observed in insular species when population density is either low or fluctuating.[24] This results in stronger natural selection and weaker intraspecific selection, leading to different phenotypes compared to the standard island syndrome.

RIS was first described in a population of Italian wall lizard endemic to the Licosa Islet where the unpredictable environmental conditions and highly fluctuating population density have selected for aggressive behaviour and increased reproductive effort.[25] The male lizards exhibit elevated α-MSH levels relative to mainland populations, which increases the basal metabolic rate, strengthens immune responses, produces darker blue coloration and raises 5α-dihydrotestosterone levels.[25] The latter improves male reproductive success by increasing the likelihood of winning sexual conflicts over females and augmenting sperm quality.[25] Females produce similar numbers of eggs compared to mainland populations but the eggs of insular females are significantly heavier, reflecting increased reproductive effort. The unpredictable conditions produce high mortality rates so adults invest more effort into current broods since they are less likely to survive to produce subsequent broods i.e. there is low interbrood conflict.