Ecological and evolutionary influences on body size and shape in the Galápagos marine iguana (Amblyrhynchus cristatus)

Many organisms on islands have morphological differences that occur between populations. This article published in Oecologia in 2016 specifically looked at Galápagos marine iguanas (Amblyrhynchus cristatus) to determine the cause and extent of the morphological variations in this endemic island species. The researchers Chiari, Glaberman, Tarroso, Caccone, and Claude looked at 16 sampling sites across 12 islands of the Galápagos in 1993. They looked at eight morphological characteristics; snout-vent length, tail length, length of the front limb, length of the third digit of the manus, height, length and width of the head, and jaw length.  They also obtained genetic data for each individual (343 in total). They also obtained environmental data from each population area. They measured intertidal productivity and sea surface temperature, as well as average monthly precipitation and air temperature. For their analysis they separated by population and sex. Their data indicated that body size and shape differ among Galapagos populations of marine iguanas. They explained the variation in body shape partially by evolutionary history. The results also showed sexual dimorphism in all populations except one. In the future, research should focus on determining the amount of influence from plasticity or adaptation in reference to body size and shape. This study is important because it lays the groundwork for future studies regarding the cause of significant morphological differences in island species like the marine iguana. It is important to expand our knowledge on how species of herps become diverse and the marine iguana in the Galapagos Islands is a good place to start.




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