LAUSR

Insular biodiversity has aroused the curiosity of biologists in assessing ecological and evolutionary hypotheses concerning their mainland counterparts. Comparisons of particular life history traits between island and mainland populations have provided a broader view of phenotypic and behavioral plasticity at both intraspecific and interspecific levels (Meiri 2007). Body size has been one of the most important biological traits used to measure phenotypic features, as it correlates with all aspects of life history and is influenced by many abiotic and biotic factors (Peters 1983). There are some studies that explore body size variation as a measure of sexual size dimorphism (Shine 1989); this measure can be maleor femalebiased and is more evident in the larger species (Abouheif and Fairbairn 1997). Conversely, some investigations have shown the effects of the island rule hypothesis on body size variation, which suggests gigantism in small animals and dwarfism in large animals as a response to competition, predation, and food availability in insular environments (Van Valen 1973; Meiri et al. 2008). Lizards of the genus Anolis (Squamata: Dactyloidae) have been used as excellent models in attempting to understand ecological and physiological processes between and within species, as well as across environmental conditions (Losos 2009). Body size comparisons between island and mainland populations have been recorded in the Clouded Anole Anolis nebulosus (Hernández-Salinas et al. 2014; Senczuk et al. 2014; Siliceo-Cantero et al. 2016). These studies have shown that sexual dimorphism is higher on the island than on the mainland; however, such comparisons were conducted in a single study area per environment, and the continental and insular sites have been the same in some of the above-referenced studies. Therefore, whether similar body size patterns are different between insular and mainland populations remains somewhat unknown. The goal of this study is to assess the effect of the island rule hypothesis on sexual size dimorphism (SSD) in A. nebulosus. First, we compared the body size (SVL: snout-vent length) between males and females from 3 island populations. If insular populations exhibit sexual dimorphism, in concordance with previous works (e.g., Hernández-Salinas et al. 2014), initially we expected a male-biased body size. Scharf and Meiri (2013), however, observed that analyzing body size alone could lead to different conclusions and misleading hypotheses on sexual dimorphism, and so for this reason, we also compared 4 morphological traits between the sexes among the island populations. Second, we evaluated the body size of island populations and some mainland populations across most of the geographic range of A. nebulosus. The island rule could not only favor a large body size, but also the ornamentation related to sexual selection; thus, we also compared the male ornament (i.e., dewlap length and size) between the island and mainland populations. Third and finally, we calculated the SSD index to illustrate the direction of sexual dimorphism among island and mainland populations. The methods and statistical analyses are described in the Supplementary Material. Briefly, we measured 6 morphological traits in 305 museum specimens, which represent 4 insular populations and 32 mainland populations of A. nebulosus (Figure 1A, Appendix 1). The number of specimens measured from each population ranged from 2 to 61. The measurements were taken with a caliper scale 150 mm to 6 0.1 mm precision. To avoid potential miscalculations, the same person measured all the museum specimens. We identified their sex by using external sex-specific characteristics. We also estimated the dewlap area of males from island and mainland populations. All of the measurements were log10 transformed before the data analysis. To calculate the SSD index, additional data on island and mainland populations were obtained from the literature. In total, we measured 37 males and 14 females from Isla Marı́a Cleofas, 25 males and 4 females from Isla Marı́a Madre, 43 males