![]() ![]() ![]() Conflict between models run using different biogeographic regimes highlights the sensitivity of these reconstructions to biogeographic region delineation. This study suggests equal probability for a Caribbean origin to Darwin's finches as a South American mainland origin. ![]() However, models run using only 5 areas suggest equal probability between a Caribbean and a mainland South America origin to Darwin's finches. Biogeographic models run using 8 regions suggest Darwin's finches arose from a long-distance dispersal event from the Caribbean Islands as opposed to the geographically closer mainland South America. The majority of ancestral ranges within this subfamily were estimated as Caribbean restricted. We used these models to examine 2 different hypotheses regarding the biogeographic origin of Darwin's finches. We test multiple biogeographic models using the R package BioGeoBEARS utilizing a recent multilocus phylogeny. We use this reconstruction to examine the origin of Darwin's finches, and the diversification of this clade of tanagers. In this paper, we reconstruct the ancestral biogeography of Coerebinae, the tanager subfamily that contains Darwin's finches and their 14 closest relatives. Few studies, however, have attempted to investigate the biogeographic origins of Darwin's finches. Natural selection, then, provides a more compelling mechanism for adaptation and evolution than Lamarck's theories.Darwin's finches are considered a classic example of an adaptive radiation, and have been the focus of numerous studies from ecological and evolutionary perspectives. However, it was Darwin’s concept of natural selection, wherein favorable traits like a long neck in giraffes suvived not because of aquired skills, but because only giraffes that had long enough necks to feed themselves survived long enough to reproduce. Lamarck theorized that behaviors aquired in a giraffe's lifetime would affect its offspring. In Lamarck’s thinking, the offspring of a giraffe that stretched its neck would then inherit a slightly longer neck. The example he gave stated the ancestors of giraffes might have adapted to a shortage of food from short trees by stretching their necks to reach higher branches. Another French thinker, Jean Baptiste Lamarck, proposed that animals could adapt, pass on their adaptations to their offspring, and therefore evolve. He was a French mathematician who believed that organisms changed over time by adapting to the environments of their geographical locations. Scientists who studied adaptation prior to the development of evolutionary theory included Georges Louis Leclerc Comte de Buffon. One example of behavioral adaptation is how emperor penguins in Antarctica crowd together to share their warmth in the middle of winter. Organisms can also exhibit behavioral adaptation. Tibetans seemed to have evolved genetic mutations that allow them to use oxygen far more efficently without the need for extra hemoglobin. However, continuously high levels of hemoglobin are dangerous, so increased hemoglobin levels are not a good solution to high-altitude survival in the long term. Most people can survive at high altitudes for a short time because their bodies raise their levels of hemoglobin, a protein that transports oxygen in the blood. Breathing air that thin would cause most people to get sick, but Tibetans’ bodies have evolved changes in their body chemistry. Tibetans thrive at altitudes where oxygen levels are up to 40 percent lower than at sea level. An example of biological adaptation can be seen in the bodies of people living at high altitudes, such as Tibet. They can adapt biologically, meaning they alter body functions. Organisms can adapt to an environment in different ways. This enables better survival and reproduction compared with other members of the species, leading to evolution. The idea of natural selection is that traits that can be passed down allow organisms to adapt to the environment better than other organisms of the same species. In developing the theory of evolution by natural selection, Wallace and Darwin both went beyond simple adaptation by explaining how organisms adapt and evolve. Wallace believed that the evolution of organisms was connected in some way with adaptation of organisms to changing environmental conditions. ![]() Although scientists discussed adaptation prior to the 1800s, it was not until then that Charles Darwin and Alfred Russel Wallace developed the theory of natural selection. In evolutionary theory, adaptation is the biological mechanism by which organisms adjust to new environments or to changes in their current environment. ![]()
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