International Journal of Molecular Evolution and Biodiversity 2024, Vol.14, No.4, 197-207 http://ecoevopublisher.com/index.php/ijmeb 199 Figure 1 Study sites and species (Adopted from McNew et al., 2017) (A) The Galápagos Archipelago. (B) Santa Cruz Island; Roads are indicated by narrow grey lines and study sites by red Xs. (C) Geospiza fortis; photo by J.A.H.K. (D) Geospiza fuliginosa; photo by S.A.K. Maps in (A) and (B) are modified from © 2016 Google (Adopted from McNew et al., 2017) 3 Environmental Stressors Affecting Avian Species 3.1 Climate change: temperature fluctuations and altered precipitation patterns Climate change is a significant environmental stressor that affects avian species through temperature fluctuations and altered precipitation patterns. These changes can influence various aspects of avian life, including growth, development, and survival. For instance, weather conditions such as air temperature, rainfall, wind speed, and solar radiation have been shown to impact nestling growth and development, which can have long-lasting effects on adult phenotypes and fitness (Sauve et al., 2021). Additionally, climate warming has been correlated with body size reductions in North American migratory birds, although species with larger relative brain sizes exhibit weaker phenotypic responses, suggesting that cognitive abilities may buffer some species from the impacts of warming temperatures (Baldwin et al., 2022). 3.2 Habitat destruction and fragmentation Habitat destruction and fragmentation pose severe threats to avian species by reducing available habitats and isolating populations. This can lead to inbreeding, loss of genetic variation, and increased extinction rates, particularly under stressful conditions (Frankham, 2005). Fragmented populations may also experience reduced adaptive evolutionary potential, making it challenging for them to cope with environmental changes. The persistence of avian species in fragmented habitats often depends on their ability to adapt to local conditions, which can be facilitated by standing genetic variation (Yang et al., 2019). 3.3 Pollution and its genetic implications Pollution, particularly from industrial sources, can act as a selective pressure on avian populations, leading to genetic adaptations. Such rapid evolutionary rescue is less likely in species with smaller population sizes due to the complexity of adaptive phenotypes and potential fitness costs. The genetic architecture underlying these adaptations often involves multiple regions under selection, reflecting complex responses to diverse stressors.
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