When

speciation Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within ...

is not driven by (or strongly correlated with) divergent natural selection, it can be said to be nonecological, so as to distinguish it from the typical definition of

ecological speciation Ecological speciation is a form of speciation arising from reproductive isolation that occurs due to an ecological factor that reduces or eliminates gene flow between two populations of a species. Ecological factors can include changes in the envir ...

: "It is useful to consider ecological speciation as its own form of species formation because it focuses on an explicit mechanism of speciation: namely divergent natural selection. There are numerous ways other than via divergent natural selection in which populations might become genetically differentiated and reproductively isolated." It is likely that many instances of nonecological speciation are

allopatric Allopatric speciation () – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from ...

, especially when the organisms in question are poor dispersers (e.g.,

land snail A land snail is any of the numerous species of snail that live on land, as opposed to the sea snails and freshwater snails. ''Land snail'' is the common name for terrestrial gastropod mollusks that have shells (those without shells are known as ...

salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten ...

s), however

sympatric In biology, two related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter one another. An initially interbreeding population that splits into two or more distinct species sh ...

nonecological speciation may also be possible, especially when accompanied by an "instant" (at least in evolutionary time) loss of reproductive compatibility, as when

polyploidization Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within ...

happens. Other potential mechanisms for nonecological speciation include mutation-order speciation and changes in chirality in

gastropods The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. Ther ...

. Nonecological speciation might not be accompanied by strong morphological differentiation, so might give rise to

cryptic species In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

, however there are some species that are difficult for humans to differentiate that are strongly differentiated with respect to their resource use, and so are likely a result of ecological speciation (e.g., host shifts in parasites or phytophagous insects). When species recognition/sexual selection plays a strong role in maintaining species boundaries, the species generated by nonecological speciation might be straightforward for humans to differentiate, as in some odonates.

References

{{evolution Ecology Evolutionary biology *

See also

References