Editing Asarum (section)

== Taxonomy ==
Traditionally, the genus ''Asarum'' was considered as a single genus with about 85 species. However, a trend exists among some botanists to segregate the genus into separate genera, based on considerations of chromosome number and floral morphology:
* ''Asarum'' [[Sensu#Common qualifiers|''sensu stricto'']] (about 17 species), distributed in Asia (mainly China), North America, and Europe
* ''[[Heterotropa (plant)|Heterotropa]]'' (about 50 species), distributed in Asia
* ''[[Asiasarum]]'' (three or four species), distributed in Asia
* ''[[Geotaenium]]'' (three or four species), distributed in Asia
* ''[[Hexastylis]]''  (ten species), distributed in North America

Study of the [[internal transcribed spacer]] region (ITS) of nuclear [[ribosomal DNA]], combined with morphological data, has yielded a better-resolved phylogenetic hypothesis,  supporting a recognition of two subgenera, ''Asarum'' and ''Heterotropa'' each containing two sections, rather than the segregated genera above.<ref>{{cite journal | author=Lawrence M. Kelley| title=Phylogenetic relationships in ''Asarum'' (Aristolochiaceae) based on morphology and ITS sequences| journal=American Journal of Botany| year=1998| volume=85| pages=1454–67 | issue=10 | doi=10.2307/2446402 | pmid=21684897| jstor=2446402}}</ref>

*'''''Asarum''''' ''sensu stricto'' (''s.s.'') : the North American species are [[monophyletic]] and are derived from within the [[paraphyletic]] Asian species group.
* '''''Geotaenium''''' is a sister to ''Asarum'' ''s.s.'', showing its close relationship to ''Asarum'' ''s.s.''.
* '''''Asiasarum''''' is a sister to the ''Hexastylis'' + ''Heterotropa'' clade, showing several [[Synapomorphy|synapomorphies]] with this clade.
* '''''Hexastylis''''': this genus has been recognized solely on the study by H.L. Blomquist.<ref name="Blomquist">{{cite journal | author=H.L. Blomquist| title=A revision of Hexastylis of North America| journal=Brittonia| year=1957| volume=8| pages=255–281|jstor=2804978 | issue=4 | doi=10.2307/2804978| bibcode=1957Britt...8..255B| s2cid=34632340}}</ref> However, the above-mentioned DNA study provided indications that ''Hexastylis'' is not monophyletic and that some species of ''Hexastylis'' are more closely related to Asiatic species of  ''Heterotropa'' than they are to other species of ''Hexastylis''. The recognition of ''Hexastylis'' has likely persisted due to regional botanists' contrasting the morphology of that section with the regionally co-occurring ''Asarum canadense'', which is the sole species of Asarum subgenus Asarum in the southeastern United States. However, the morphological character states used to support the recognition of section Hexastylis at the generic level are plesiomorphic. For example, Blomquist <ref>Blomquist</ref> provides an enumeration of character states supporting ''Hexastylis'', all of are plesiomorphic with respect to one or another ''Asarum'' lineage. The presence of persistent, variegated leaves is often invoked by amateur botanists as a characteristic unique to section Hexastylis amongst North American ''Asarum'' species, however ''[[Asarum marmoratum]]'', an ''Asarum'' Subgenus Asarum species found in the western United States also has persistent and variegated leaves ([https://www.calflora.org/app/taxon?crn=736 see Calflora page for detailed photographs])
* '''''Heterotropa''''': this is a complex monophyletic group, well nested within the ''Asiasarum'' + ''Hexastylis'' + ''Heterotropa'' clade.

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