<P> As the remaining habitat patches are smaller, they tend to support smaller populations of fewer species . Small populations are at an increased risk of a variety of genetic consequences that influence their long - term survival . Remnant populations often contain only a subset of the genetic diversity found in the previously continuous habitat . Processes that act upon underlying genetic diversity such as adaptation have a smaller pool of fitness - maintaining alleles to survive in the face of environmental change . </P> <P> Gene flow occurs when individuals of the same species exchange genetic information through reproduction . Populations can maintain genetic diversity through migration . When a habitat becomes fragmented and reduced in area, gene flow and migration is typically reduced . Fewer individuals will migrate into the remaining fragments, and small disconnected populations that may have once been part of a single large population will become reproductively isolated . Scientific evidence that gene flow is reduced due to fragmentation depends on the study species . While trees that have long - range pollination and dispersal mechanisms may not experience reduced gene flow following fragmentation, most species are at risk of reduced gene flow following habitat fragmentation . </P> <P> Reduced gene flow, and reproductive isolation can result in inbreeding between related individuals . Inbreeding does not always result in negative fitness consequences, but when inbreeding is associated with fitness reduction it is called inbreeding depression . Inbreeding becomes of increasing concern as the level of homozygosity increases, facilitating the expression of deleterious alleles that reduce the fitness . Habitat fragmentation can lead to inbreeding depression for many species due to reduced gene flow . Inbreeding depression is associated with conservation risks, like local extinction . </P> <P> Small populations are more susceptible to genetic drift . Genetic drift is random changes to the genetic make up of populations and always leads to reductions in genetic diversity . The smaller the population is, the more likely genetic drift will be a driving force of evolution rather than natural selection . Because genetic drift is a random process, it does not allow species to become more adapted to their environment . Habitat fragmentation is associated with increases to genetic drift in small populations which can have negative consequences for the genetic diversity of the populations . </P>

Does habitat fragmentation favor core species or edge species