International Journal of Molecular Evolution and Biodiversity 2024, Vol.14, No.4, 197-207 http://ecoevopublisher.com/index.php/ijmeb 201 Figure 1 Map (Mercator projection) showing estimated locations of arctic terns from the Baltic Sea during their annual migration cycle (Adopted from Alerstam et al., 2019) Daily locations based on geolocator data for 12 annual journeys by eight individuals are shown for all journeys combined to illustrate the overall global migration pattern for the study population. Locations are missing due to uncertain and invalid latitude data during periods around the autumn and spring equinoxes. Arrows indicate the most likely movement patterns based on longitude data during the equinox periods, eastward into the Indian Ocean around the autumn equinox and toward northeast (first) and northwest (later) from the Weddell Sea up the southern Atlantic Ocean around the spring equinox. Small arrows indicate southeastward crossing of the Antarctic Convergence in the longitudinal sector from 80E and eastward. Locations have been provisionally plotted during the terns’ wintering period in the Antarctic in spite of the fact that latitude could not be properly estimated but only inferred to be south of 60S during the southern polar summer. The Mercator projection is conformal and true to compass direction. However, it is not true to distance and area, with polar regions greatly exaggerated in size (Adopted from Alerstam et al., 2019) 5 Phenotypic Plasticity vs. Genetic Adaptation 5.1 Definition and examples of phenotypic plasticity in avian species Phenotypic plasticity refers to the ability of a single genotype to produce different phenotypes in response to varying environmental conditions. This adaptive mechanism allows organisms to cope with environmental changes without genetic alterations. In avian species, phenotypic plasticity can manifest in various ways. For instance, zebra finch mothers exposed to heat stress can induce changes in their offspring, such as altered heart rates and increased eggshell pore density, which are positively correlated with survival under high temperatures (Hoffman et al., 2021). Another example is the great tit (Parus major), which adjusts its reproductive timing in response to environmental changes, allowing the population to closely track rapid climate changes. 5.2 Comparison between phenotypic plasticity and genetic adaptation Phenotypic plasticity and genetic adaptation are two distinct mechanisms through which organisms can respond to environmental changes. Phenotypic plasticity involves immediate, reversible changes in phenotype without altering the underlying genetic code. In contrast, genetic adaptation involves changes in allele frequencies within a population over generations, leading to permanent alterations in phenotype. Phenotypic plasticity acts as a rapid-response mechanism, enabling individuals to survive sudden environmental changes. For example, plastic responses in avian species can include behavioral adjustments to human disturbances, such as reduced flushing distances and changes in social behavior (Jimenez et al., 2013). On the other hand, genetic adaptation is a slower process that involves the selection of advantageous traits over multiple
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