Editing Hypericum perforatum (section)

=== Phylogeny ===
''Hypericum perforatum'' has a [[Ploidy|chromosome count]] of 2n = 32. The likely reason for this is that the species is a [[Hybrid (biology)|hybrid]] between the very closely related ''H. maculatum subsp. immaculatum'' and ''[[Hypericum attenuatum|H. attenuatum]],'' which means it inherited sets of chromosomes from both parents and is [[allopolyploid]]. The two species almost certainly hybridized within [[Siberia|Siberia, Russia]]. The equation for this hybridization is:<ref name="Ernst-2003" />
{{Blockquote|text=''H. maculatum'' subsp. ''immaculatum'' (16) × ''H. attenuatum'' (16)×2 = ''H. perforatum'' (32)}}[[File:Hypericum × desetangsii 112458176.jpg|thumb|[[Hypericum × desetangsii|''Hypericum'' × ''desetangsii'']] is a hybrid between ''H. perforatum'' and ''H. maculatum''. It displays intermediate traits of the two species.]]Because of its hybrid origins, ''Hypericum perforatum'' is one of the few species within its genus that is able to further hybridize with other species, specifically those within [[Hypericum ser. Hypericum|''H.'' ser. ''Hypericum'']]. The hybrids that are descended from ''H. perforatum'' can be triploid (3 sets of chromosomes) to hexaploid (6 sets), depending on the chromosome count of the second parent species and the ploidy of the specific ''H. perforatum'' [[gamete]] that is fertilized or is fertilizing. The triploid offspring exhibit and a mix of traits from the two parents and pass them on to their offspring; the tetraploids also have a mix of traits, but often do not pass on the traits of both parents; the pentaploids are rarely distinguishable from ''H. perforatum''. Because of this, after many generations of hybridization a wide range of traits on a spectrum between the two hybridizing species can be observed in the wild.<ref name="Robson-2002">
{{Cite journal |last=Robson |first=Norman |author-link=Norman Robson (botanist) |date=2002 |title=Studies in the genus ''Hypericum'' {{small|L.}} (Guttiferae) 4(2). Section 9. ''Hypericum'' sensu lato (part 2): subsection 1. ''Hypericum'' series 1. ''Hypericum''. |url=https://www.biodiversitylibrary.org/page/2277196#page/2/mode/1up |journal=Bulletin of the British Museum (Natural History) Botany |volume=32 |pages=61–123 |via=[[Biodiversity Heritage Library]]}}</ref>{{rp|64}}

{| class="wikitable"
|+Hybrids involving ''H. perforatum<ref name="Robson-2002" />''
!Crossed with
!Hybrid name
!Chromosome number<ref group="a">Uncertainty in chromosome number notated by "?"</ref>
|-
|''[[Hypericum elegans|H. elegans]]''
|''H. perforatum × elegans''
|2n = 32?
|-
|''[[Hypericum tetrapterum|H. tetrapterum]]''
|''[[Hypericum × medium|''H.'' × ''medium'']]''
|2n = 24?
|-
|''[[Hypericum maculatum|H. maculatum]]'' [[Subspecies|ssp.]] ''maculatum''
|[[Hypericum × desetangsii|''H.'' × ''desetangsii'']] [[Hybrid name#Forms of hybrid names|nssp.]] ''carinthiacum''
|2n = 24/40
|-
|''H. maculatum'' ssp. ''immaculatum''
|''H.'' × ''desetangsii'' nssp. ''balcanicum''
|2n = 24/40?
|-
|''H. maculatum'' ssp. ''obtusiusculum''
|''H.'' × ''desetangsii'' nssp. ''desetangsii'' 
|2n = 40
|-
| colspan="3" |{{Reflist|group=a}}
|}