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Table 1 Phenotypic traits shifts expected to occur in insular populations as compared to their mainland relatives according to the Island Syndrome and to the RIS.

From: The blue lizard spandrel and the island syndrome

trait

Island syndrome

Reversed Island syndrome (RIS)

Trait changes mediated by increased POMC activity (the involved MCR is indicated)

Population density

high

Low or inconstant

-

Aggressiveness

low

high

high, MC5R

Body size

usually large

small in endotherms, either small or large in ectotherms

small, MC3-4Rs

Energy expenditure

low

high

high, MC3,4R

Sexual dimorphism

small

high

-

Development

-

faster, or anticipated

-

Voracity*

low

high

Either low or high, depending on the balance between MC3R and 4R

Pigmentation*

irrelevant

darker, but may occur in non-melanistic species as well

darker, MC1R

  1. Shifts in food intake rate and pigmentation (indicated with an asterisk) are not directly predicted by the RIS hypothesis and are only true if RIS is triggered by changes in melanocortin receptors activity, and these are not polymorphic. In the last column we report the trait shifts mediated by increase in POMC expression and their relationship with RIS.