Q.6 In ecotone, some species become abundant and they are called
The correct answer is (D) edge species.
Ecotones represent transition zones between two ecosystems where certain species thrive abundantly due to diverse resources and conditions, known as the edge effect. This phenomenon leads to higher species density and diversity compared to adjacent habitats.
Option Analysis
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(A) Sibling species: These are morphologically nearly identical species that remain reproductively isolated and do not interbreed, such as Drosophila pseudoobscura and D. persimilis; they relate to speciation, not ecotone abundance.
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(B) Endemic species: These species occur exclusively in a specific geographic area, like certain island plants, and face risks from limited ranges rather than proliferating in transition zones.
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(C) Rare species: These have small global populations or narrow distributions, often below 10,000 individuals, making them scarce rather than abundant anywhere, including ecotones.
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(D) Edge species: Correct—these species dominate ecotones, benefiting from edge effects like increased niches and resources at boundaries, such as birds in forest-grassland zones.
Edge species in ecotone areas thrive as transition zones between ecosystems create ideal conditions for abundance. This edge effect boosts biodiversity, making ecotones hotspots for species density.
Ecotone Basics
Ecotones form where ecosystems meet, like forest-grassland or estuary boundaries, featuring intermediate conditions that support mixed communities. Species richness peaks here from overlapping habitats.
Edge Effect Explained
The edge effect causes population booms in ecotones due to broader niches, more light, and resources. Edge species, such as certain birds or amphibians, exploit this for higher densities than in core habitats.
Why Not Other Species?
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Sibling species focus on reproductive isolation despite similar looks, irrelevant to ecotone dynamics.
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Endemic species stay confined to one region, not expanding in transitions.
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Rare species maintain low numbers globally, contrasting ecotone abundance.
Examples include mangrove edge species blending marine and terrestrial life or grassland-forest birds.
