Editing Oleaceae (section)

== Taxonomy ==
Oleaceae is one of only a few major plant families for which no well-sampled molecular phylogenetic study has ever been conducted. The only [[DNA sequence]] study of the entire family sampled 76 species for two noncoding [[chloroplast]] loci, ''rps16'' and ''trnL–F''. Little was determined in this study, largely because the [[mutation rate]] in the [[chloroplast genome]] of Oleaceae is very low compared to that of most other angiosperm families.<ref name=wallander2000>{{cite journal | last1 = Wallander | first1 = Eva | last2 = Albert | first2 = Victor A. | year = 2000 | title = Phylogeny and classification of Oleaceae based on ''rps16'' and ''trnL-F'' sequence data | journal = American Journal of Botany | volume = 87 | issue = 12| pages = 1827–41 | doi=10.2307/2656836| jstor = 2656836 | pmid = 11118421 }}</ref>

Also, the family is notorious for incongruence between phylogenies based on plastid and [[nuclear DNA]]. The most likely cause of this incongruence is [[reticulate evolution]] resulting from rampant [[hybridisation (biology)|hybridization]].<ref name=hongwa2013>{{cite journal | last1 = Hong-Wa | first1 = Cynthia | last2 = Besnard | first2 = Guillaume | year = 2013 | title = Intricate patterns of phylogenetic relationships in the olive family as inferred from multi-locus plastid and nuclear DNA sequence analyses: a close-up on ''Chionanthus'' and ''Noronhia'' (Oleaceae)". | journal = Molecular Phylogenetics and Evolution | volume = 67 | issue = 2| pages = 367–378 | doi = 10.1016/j.ympev.2013.02.003 | pmid=23415987| bibcode = 2013MolPE..67..367H }}</ref>

The delimitation of genera in Oleaceae has always been especially problematic. Some recent studies of small groups of related genera have shown that some of the genera are not monophyletic. For example, ''Olea'' [[Section (botany)|section]] ''Tetrapilus'' is separate from the rest of ''Olea''. It is a distinct group of 23 species and had been named as a genus, ''Tetrapilus'', by [[João de Loureiro]] in 1790.<ref name=ipnitetrapilus>[http://www.ipni.org/ipni/advPlantNameSearch.do?find_family=&find_genus=Tetrapilus ''Tetrapilus''] in International Plant Names Index.</ref>

The genus ''Ligustrum'' has long been suspected of having originated from within ''Syringa'', and this was confirmed in a cladistic comparison of selected chloroplast genes.<ref name=li2012>{{cite journal | last1 = Li | first1 = Jianhua | last2 = Goldman-Huertas | first2 = Benjamin | last3 = DeYoung | first3 = Jeffrey | last4 = Alexander III | first4 = John | year = 2012 | title = Phylogenetics and Diversification of ''Syringa'' Inferred from Nuclear and Plastid DNA Sequences | journal = Castanea | volume = 77 | issue = 1| pages = 82–88 | doi = 10.2179/11-016 | s2cid = 83590628 }}</ref>

''Osmanthus'' consists of at least three lineages whose closest relatives are not other lineages of ''Osmanthus''.<ref name=guo2011>{{cite journal | last1 = Guo | first1 = Shi-Quan | last2 = Xiong | first2 = Min | last3 = Ji | first3 = Chun-Feng | last4 = Zhang | first4 = Zhi-Rong | last5 = Li | first5 = De-Zhu | last6 = Zhang | first6 = Zhi-Yong | year = 2011 | title = Molecular phylogenetic reconstruction of ''Osmanthus'' Lour. (Oleaceae) and related genera based on three chloroplast intergenic spacers | journal = Plant Systematics and Evolution | volume = 294 | issue = 1–2| pages = 57–64 | doi = 10.1007/s00606-011-0445-z | bibcode = 2011PSyEv.294...57G | s2cid = 21252789 }}</ref>

''Chionanthus'' is highly polyphyletic, with its species scattered across the phylogenetic tree of the subtribe Oleinae. Its African species are closer to ''Noronhia'' than to its [[type species]], the North American ''[[Chionanthus virginicus]]''. Its Madagascan species are phylogenetically within ''Noronhia'' and will be formally transferred to it in a forthcoming paper.<ref name=hongwa2013/>

The monophyly of ''Nestegis'' is in considerable doubt, but few of its closest relatives have been sampled in phylogenetic studies.