Question

Explain why interspecific competition is more likely to lead to convergent evolution and why intraspecific competition is more likely to lead to divergent evolution.

Answer 1

Interaction between population may be:

1. Intraspecific- interaction between individuals in the population of same species or strains.

2. Interspecific- interaction between individuals in the population of different species or strains.

• These interactions between similar individuals, may vary under different factors, like environmental conditions, ecological niche, or limiting resources.
• When individuals interact in such a way, that it limits the existence of the other, creates an adverse effect, or is even detrimental to certain individuals in a population, such interactions are described as competition.
• Competition may be again, interspecific, or intraspecific.

Lotka-Volterra model:

• It compares the population dynamics of species as predator-prey model. It also describes the relation between intraspecific competition (competition among the population of same species) and interspecific competition (competition among the population of different species).
• It thus concludes, that co-existence between two species is possible, if intraspecific competition is greater that interspecific competition.
• It considers the various levels of resources, or different types of resources, and the ability of the species to use these resources.

The assumptions are based on logistic -competition model, based on logistic growth equation.

dN/dt = r_m N (1 - N/K)

Intraspecific competition:

• Usually, competition occurs under the condition of limiting resources, like sharing if ecological niche, food, water, mating conditions, size and health of the individual, etc.
• This leads to adaptation to use an alternative resource or diversification of ecological niche.
• There is adaptive radiation generating homologous structures.
• Divergence leads to sympatric speciation.
• Sympatric speciation occurs from common ancestors.
• The population is not separated.
• All species arise from same ancestral species in the same geographical region.
• In this case gene flow is disrupted. There is specialization of habitat/niche.

Interspecific competition:

• The species compete for similar type of resources.
• Thus, adaptation becomes similar or convergent.
• Convergent may lead to allopatric speciation.
• Geographically separate population experiences a varied or differential selective pressure through natural selection.
• There is reproductive isolation, interbreeding.
• This results in mutations and genetic variations.
• This is indicated as allopatric speciation.
• Common type of speciation.