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#island colonization

3 public questions tagged with this topic.

Biogeography

Which factor increases colonization rates significantly?

“Larger mainland species pool” for which factor increases colonization rates significantly. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Larger islands usually support more habitats and larger populations, lowering extinction risk; less isolated islands receive colonists more readily and may experience rescue effects. These mechanisms also apply to habitat fragments that function as ecological islands. The remaining alternatives—“Smaller mainland species pool”, “Greater distance from mainland”, “Smaller island size”—refer to different states, processes, or scales and therefore do not express the same causal relationship. At equilibrium, species identities can continue to turn over even when richness is approximately stable. The model predicts a balance of rates, not an absence of colonization or extinction. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation.

Ref: Biogeography, Lomolino et al., 5th Ed., Ch. 1-4

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Biogeography

Why is the initial extinction rate low in newly colonized islands?

“Low competition and abundant resources” for why is the initial extinction rate low in newly colonized islands. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Larger islands usually support more habitats and larger populations, lowering extinction risk; less isolated islands receive colonists more readily and may experience rescue effects. These mechanisms also apply to habitat fragments that function as ecological islands. The remaining alternatives—“High competition”, “Limited resources”, “High predation risk”—refer to different states, processes, or scales and therefore do not express the same causal relationship. At equilibrium, species identities can continue to turn over even when richness is approximately stable. The model predicts a balance of rates, not an absence of colonization or extinction. Field observations could test this account by measuring the proposed driver and the demographic or ecosystem response while controlling plausible confounding factors.

Ref: Biogeography, Lomolino et al., 5th Ed., Ch. 1-4

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Island

Islands with higher colonization rates are:

“Large and near” for islands with higher colonization rates are. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Island biogeography explains species richness as a dynamic balance between immigration and extinction. Immigration generally declines as an island fills with species, whereas extinction rises as more species divide finite area and maintain smaller populations. The remaining alternatives—“Small and distant”, “Small and near”, “Large and distant”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Larger islands usually support more habitats and larger populations, lowering extinction risk; less isolated islands receive colonists more readily and may experience rescue effects. These mechanisms also apply to habitat fragments that function as ecological islands. Linking the wording to measurable consequences for fitness, abundance, or flux gives the conclusion its scientific meaning and prevents a purely mnemonic interpretation.

Ref: The Theory of Island Biogeography, MacArthur & Wilson, Ch. 2-4

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