Population fragmentation is a form of population segregation. It is often caused by habitat fragmentation. Population fragmentation causes inbreeding depression, which leads to a decrease in genetic variability in the species involved. This decreases the fitness of the population for several reasons. First, inbreeding forces competition with relatives, which decreases the evolutionary fitness of the species. Secondly, the decrease in genetic variability causes an increased possibility a lethal homozygous recessive trait may be expressed; this decreases the average litter size reproduced, indirectly decreasing the population.
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