The Bark Anole (Anolis distichus ignigularis) from the Río Recodo. Photo from Richard Glor’s Flickr.

The Bark Anole (Anolis distichus) is a highly polymorphic lizard widely distributed in Hispaniola. Anolis distichus is divided into 16 subspecies with dewlap colors ranging from deep wine red to pale yellow (Glor and Laport 2012). In the early days scientists, such as Albert Schwartz, argued that A. distichus is divisible into multiple subspecies according to an analysis of variation in body color and dewlap pigmentation. But, are they really subspecies?

During the 2018 Joint Meeting of Ichthyologists and Herpetologists (JMIH), Richard Glor shared his lab’s advances on the curious case of Bark Anoles. Anolis distichus populations have ecological, phenotypic and genetic differences. Previous studies show a correlation between dewlap phenotype and environmental variation; in drier habitats, lizards have smaller, brighter, yellow dewlaps, while those in wetter habitats have larger, less bright, orange dewlaps (Ng et al. 2012).

Previously, the Glor Lab found strong support for the hypothesis that A. distichus is comprised of numerous genomically distinct populations (MacGuigan et al. 2016). Genetic divergence was associated with a biogeographic barrier, but not with dewlap color. Also, they found evidence for hybridization in contact zones with limited gene flow and intrinsic reproductive isolation between subspecies (MacGuigan et al. 2016; Ng et al. 2016). Overall, these studies suggest that geographic isolation, as well as ecological specialization, contribute to speciation.

The Glor Lab continues putting together the pieces of the puzzle. Most recently, they sequenced and assembled whole genome sequence data for A. distichus to identify the genomic basis for species differences and speciation.

Jessica Pita Aquino
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