Editing Gene flow (section)

=== Sympatric speciation ===

Barriers to gene flow need not always be physical. Sympatric speciation happens when new species from the same ancestral species arise along the same range. This is often a result of a reproductive barrier. For example, two palm species of ''Howea'' found on Lord Howe Island were found to have substantially different flowering times correlated with soil preference, resulting in a reproductive barrier inhibiting gene flow.<ref>{{cite journal | vauthors = Savolainen V, Anstett MC, Lexer C, Hutton I, Clarkson JJ, Norup MV, Powell MP, Springate D, Salamin N, Baker WJ |author1-link=Vincent Savolainen| display-authors = 6 | title = Sympatric speciation in palms on an oceanic island | journal = Nature | volume = 441 | issue = 7090 | pages = 210–3 | date = May 2006 | pmid = 16467788 | doi = 10.1038/nature04566 | s2cid = 867216 | bibcode = 2006Natur.441..210S }}</ref> Species can live in the same environment, yet show very limited gene flow due to reproductive barriers, fragmentation, specialist pollinators, or limited hybridization or hybridization yielding unfit hybrids. A cryptic species is a species that humans cannot tell is different without the use of genetics. Moreover, gene flow between hybrid and wild populations can result in loss of genetic diversity via [[genetic pollution]], [[assortative mating]] and [[outbreeding]]. In human populations, genetic differentiation can also result from [[endogamy]], due to differences in caste, ethnicity, customs and religion.