Saturday, November 18, 2023

Microchromosome fusions underpin convergent evolution of chameleon karyotypes


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Convergent evolution is defined as the independent development of specific similar traits and structures, among species. Typically, a characteristic is considered to be convergent if the previous ancestor in the lineage did not possess the same traits. In this study, the hypothesis explores the wide variety of karyotypes in chameleons. Species in the Chamaeleonidae family can have anywhere  between 20 and 62 chromosomes, which, given their similar phenotype, prompted researchers to investigate what was driving the convergent evolution. The study explored microchromosome fusions, and found this to be the predominant cause for reduced evolutionary change.

Research was gathered from 57 species of chameleons, and PCR was utilized to amplify markers in the specimens. Chromosome samples were analyzed and separated into separate categories: haploid, diploid, arm number, macrochromosome, microchromosome and position of NOR loci. Sex chromosomes were not researched, due to their independence from autosomal chromosomes and different arrangements in various species.  Loss and gain of chromosomes was tracked on ChromEvol system. Estimates of chromosome numbers were generated for the chameleon genuses, as shown below, with the color and number indicating the number of chromosome pairs (haploid value). It is extremely interesting to see the convergence of traits, given the diversity of the Chamaeleonidae family.  Many of these species have had little to none research, so there is a significant amount of information we have yet to learn from these beautiful creatures.

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