The species inhabiting oceanic islands have been fundamental in the study of evolution. Due to their isolation, these populations tend to have smaller sizes and lower genetic diversity compared to their mainland relatives. This can lead to negative effects such as the accumulation of harmful mutations and inbreeding (mating between genetically related individuals), which threatens their survival. The Galápagos mockingbirds (Mimus spp.) represent an ideal case to analyze the relationship between the size of the island they inhabit and genetic variations in their populations.
This study analyzed eight mockingbird populations on islands of different sizes through DNA studies and the reconstruction of their demographic history. It was observed that on smaller islands, where populations are smaller and more isolated, inbreeding levels are higher due to the lack of genetic exchange with other populations. In contrast, on larger islands, the greater number of individuals promotes higher genetic diversity and a lower harmful genetic load.
The study combined advanced methods, such as genome sequencing and bioinformatics analysis, to understand the relationship between island size and mockingbird genetics. Evolutionary trees and statistical models were constructed to analyze their population history, allowing the detection of historical changes in population size and genetic differentiation between them.
One of the most significant findings was the possible existence of a “genetic purging” mechanism in some small populations, where natural selection has eliminated harmful mutations. However, in critically endangered species like Mimus trifasciatus, a high genetic load was detected due to its recent population decline. Overall, this study confirms that island size is a key factor in the genetic diversity and health of these birds, providing essential information for their conservation.
Read the article here: https://onlinelibrary.wiley.com/doi/10.1111/mec.17665
