According to the model by Case and Taper, gene flow may play a role in limiting
ID: 40015 • Letter: A
Question
According to the model by Case and Taper, gene flow may play a role in limiting species ranges because
A)
alleles moving into the marginal populations are not adaptive for the conditions at the margins of the species range
B)
species in the edges of the range are hybridizing, and hybrids between species have lower fitness
C)
because gene flow reduces genetic variation in marginal populations
D)
gene flow from populations at the margin of a species range to populations in the center reduces the size of populations in the margins, thus reducing genetic variation and limiting adaptive evolution of populations near the edge of the range
alleles moving into the marginal populations are not adaptive for the conditions at the margins of the species range
B)
species in the edges of the range are hybridizing, and hybrids between species have lower fitness
C)
because gene flow reduces genetic variation in marginal populations
D)
gene flow from populations at the margin of a species range to populations in the center reduces the size of populations in the margins, thus reducing genetic variation and limiting adaptive evolution of populations near the edge of the range
Explanation / Answer
According to the model by Case and Taper, gene flow may play a role in limiting species are ranging due to the absence of environmental gradients and physical barriers to dispersal, interspecific competition will not limit species ranges at evolutionary equilibrium. However, interspecific competition can interact with environmental gradients and gene flow to generate limited ranges with much low gradient and dispersal parameters than in the single-species. Species may display character displacement in sympatry and yet the reduction in competition that results from this displacement does not allow the two species to be sympatric everywhere. When species are in competition it reduces population densities in the region of overlap, which, in turn, results in the asymmetry of gene flow from center to margin.
Therefore, the option d is correct.
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