Darwin’s Finches Population - Will it Thrive or Dwindle under Climate Change?

Abstract

The Galapagos Islands are famed for their beauty and ecological diversity. They are also known for playing an integral part in the formation of Charles Darwin’s theories of evolution and natural selection. The Galapagos Islands even have their own group of finches known as Darwin’s Finches, whose beak dimensions were foundational to Darwin’s theory of evolution, recorded in The Origin of Species. The Galapagos Islands have a tropical climate, and frequently experience El Nino and La Nina oscillations. This kind of climate comes with high variability on temperature and precipitation, which can affect the reproductivity of the Darwinian Finches. Studies have shown that increased rainfall during El-Nino results in hatching success up to some extent, but after a threshold rainfall, it starts decreasing. A factor that could affect rainfall is climate change, which can also very seriously diminish or increase the reproductivity of Darwin’s Finches depending on the range of projected rainfall. This is because climate change can alter temperature and precipitation in the tropical area and change the frequency of El Nino and La Nina cycles, which in turn will affect the reproductive rates of the Finches. This paper explores the relationship between finch reproductivity and environmental factors to predict the reproductivity of the Darwin Finches in the short and long term under scenarios of climate change. We have acquired some data on the Darwinian Finches in the Galapagos Islands from the book 40 Years of Evolution: Darwin’s Finches on Daphne Major Island by Drs. Peter and Rosemary Grant. The book contains data on various factors such as the climate and rainfall of the islands, as well as the phenotypes and reproductivity rates of different species of Darwinian Finches. Using some of the data from this book we created a quadratic model that relates rainfall to the hatchling rates for the Geospiza fortis species $(\mathrm{R} 2=0.6 \text {and} \mathrm{p} \text {-value}-0.006)$. Using climate data, particularly rainfall, from CMIP6 models, this study predicts finches’ reproductive rates in 2050 and 2100. Based on this, a quantitative assessment of how finches’ population may thrive or dwindle due to climate change will be provided under rainfall projections developed under different emission pathways.