- Flufftails in mainland Asia show high variation in tail colour. However, in the far out Pacific island, the flufftails show very little variation in tail colour. This variation in tail colour can be explained by all of the following EXCEPT
(1) founder effect
(2) homologous evolution
(3) genetic drift
(4) frequency dependent selectionWhy Is Genetic Variation Lower on Islands?
1. Founder Effect
When a small number of individuals colonize a new, isolated habitat—such as a distant island—they carry only a fraction of the genetic diversity present in the original population. This “founder effect” means that the new population starts with limited genetic variation, which can persist for generations. The founder effect is a well-documented explanation for reduced genetic variation in island populations.
2. Genetic Drift
Small, isolated populations are highly susceptible to genetic drift—a random process that can lead to the loss of alleles over time. In the absence of new genetic input from other populations, genetic drift can quickly reduce genetic variation, including traits such as tail colour.
3. Frequency Dependent Selection
This form of natural selection can also influence genetic variation. In some cases, if a particular tail colour becomes rare, it may be favoured or disfavoured by predators or mates, further affecting the distribution of colour variants in the population. However, frequency dependent selection typically maintains or shifts variation based on selective pressures.
Which Explanation Does NOT Fit?
Among the options, homologous evolution does NOT explain the low variation in tail colour observed in island flufftails.
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Homologous evolution refers to similarities in traits due to shared ancestry, not to the reduction of genetic variation within a population. It describes how different species inherit similar structures from a common ancestor, not how populations lose diversity after isolation.
Summary Table
Explanation Explains Low Variation? Why/Why Not? Founder Effect Yes Small founding group limits initial genetic diversity. Genetic Drift Yes Random loss of alleles in small, isolated populations reduces variation. Frequency Dependent Selection Yes Can influence trait frequencies, sometimes reducing variation. Homologous Evolution No Describes shared ancestry, not reduction in genetic diversity. Conclusion
The reduced tail colour variation in Pacific island flufftails can be explained by founder effect, genetic drift, and frequency dependent selection. However, homologous evolution is NOT a valid explanation for this pattern, as it relates to evolutionary ancestry rather than the loss of genetic diversity in isolated populations. Understanding these distinctions is crucial for interpreting patterns of biodiversity on islands and the evolutionary processes that shape them.
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