Biotic homogenization
[3] Biotic homogenization has become recognized as a significant component of the biodiversity crisis, and as such has become of increasing importance to conservation ecologists.
Just as biotic homogenization has genetic, taxonomic, and functional components, differentiation can occur at any of these levels of organization.
There would also be greater overlap in species composition between the two communities, indicating lost β diversity and increased homogenization.
[1] Genetic homogenization can be analyzed in terms of allelic frequencies, which is accomplished through a comparison of how common specific genotypes are.
It is most strictly defined as a loss in β diversity, meaning that multiple communities are increasing in taxonomic similarity over time.
A common misconception with taxonomic homogenization is that it represents a loss in α diversity, or that it leads to decreased species richness.
[2] However, assemblages under taxonomic homogenization may actually display an increase in α diversity, a phenomenon that has been observed in plant, animal, and microbial groups.
Taxonomic homogenization is typically studied by comparing two species pools that may be separated spatially, temporally, or both.
For example, the Panamanian land bridge between North and South America allowed previously isolated assemblages to homogenize.
Interestingly, in other French studies, it has been noted that there is not a temporal relationship between functional and taxonomic homogenization, a trend that had been observed in freshwater fishes.
[10] There have been predictions that avian taxonomic homogenization is occurring on the global scale, which could lead to future mass extinctions of avifauna.
[7] Freshwater fishes were among the first taxonomic groups to be used in homogenization studies, and trends have been observed on several continents.
[1] In a more specific example, there was a 2015 study in Chile, where freshwater systems support diverse assemblages of endemic fishes.
[6] While there have been fewer studies of biotic homogenization in insects compared to other taxonomic groups, there is evidence that it exists in multiple taxa.
[1] According to a 2015 study that examined bees, hoverflies, and butterflies, the extent to which taxonomic homogenization occurs varies with taxa, country, and spatial scale.
[14] Anthropomorphic impacts on plants have been complex, with overall species richness of flora increasing over the course of human history.
Additionally, there have been significantly more introductions on the continental scale than there have been extinction of endemics, increasing overall species richness and α diversity.
[4] However, as ecosystems become increasingly similar and simplified, there is concern that the resilience of the assemblages against stressful events will be limited.
Because these are largely rooted in human activity, if conservation is to be successful, it is necessary to reduce the degree to which people cause invasions and extinctions.
Since biotic homogenization is still a relatively new area of study, increased education about both its mechanism and impact could potentially be effective as well.
[1] If we are to improve our understanding of the field, it is necessary to increase the scale of our knowledge of its spatial, temporal, geographic, and taxonomic components.
