2017 September Winning Picture

1709 sm JF Thelymitra x truncata

 

Natural hybrids are both fascinating and challenging. Fascinating because they don’t occur readily, (although of all the plant families, orchids have one of the greatest propensity for hybridising). Challenging because of the difficulty in determining the parents unlike the manmade hybrids where we can track which parents are being used to make the hybrid.

Obviously, the hybrid will share characteristics of both parents and this is the case of this month’s winning photograph, John Fennell’s Thelymitra x truncata. In the South Australian setting, a spotted orchid hybrid suggests that one of the parents will always be T. ixiodes/juncifolia and because it is blue it is most likely that the other parent will also be blue, from either the T. pauciflora or T. nuda complexes. This is true also for T. x merraniae. This is because there is no naturally occurring blue pigment. Whereas a pink or yellow parent and a blue parent will not produce a blue hybrid. Consider T. x chasmogama, T. x irregularis, T. x macmillanii are never blue.

Finally, it is fitting that this should be the winning photograph as this is the centenary month (September 2017) of its presentation to the Royal Society of South Australia, by Dr R S Rogers who also named this hybrid. The other hybrids entered were Jane Higgs Caladenia Harlequin and Diuris Earwig, both cultivated plants; Pauline Meyers Caladenia falcata X Drakonorchis barbarossa; John Fennell’s Caladenia x idiastes, T. x irregularis; Rickey Egels T. x macmillanii along with Lorraine Badger’s Caladenia roei hybrid and Caladenia x ericsoniae.

Reference

https://www.biodiversitylibrary.org/item/109628#page/353/mode/1up

https://nossa.org.au/2017/07/28/2017-june-winning-picture/

https://nossa.org.au/2014/09/26/thelymitra-x-irregularis-beautiful-but-only-a-hybrid/

Bates, R. J., ed. (2011). South Australian Native Orchids. Electronic version, 2011. NOSSA

Rules of entry:

The subject matter must have something to do with Australian orchids.  Any format is acceptable including Photo shopped images, artwork, etc

 

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Spotted Pink Sun Orchid – Beautiful, but Only a Hybrid

This week, a local radio station introduced a segment with the phrase “our rarest sun orchid” and that it was called Thelymitra irregularis or Spotted Pink Sun Orchid.  However it certainly is not our rarest sun orchid.

Thelymitra x irregularis is typically a hybrid pink spotted sun orchid

Thelymitra x irregularis,  Peter Watton, 2009

True, it is not common, but that is partly because it is a hybrid and, correctly speaking, the name should be written as Thelymitra x irregularis (the “x” indicates that it is a hybrid).

For a hybrid to occur, the two parent species need to grow in close proximity, the flowers need to open at the same time that the pollinator is visiting flowers, either to collect or to deposit the pollen and, in the case of self pollinating species, before the individual flower has pollinated itself.

The majority of hybrids are sterile, but occasionally some are fertile.  When hybrids occur the majority will only last a few years before disappearing although sometimes colonies are formed which may last for decades.  Hence, it is not usual to name hybrids, but the more common and recurring ones have been named formally.  T. x irregularis is one of them.

Several species of Thelymitra have been proposed as parent species of Thelymitra x irregularis.  Jeanes & Backhouse (2006) give T. ixioides and T. carnea as parents; Weber & Entwisle (1996) and Jones (2006) suggest T. ixioides and T. carnea and/or T. rubra; Bates & Weber (1990) state that in South Australia the parents are T. ixioides and T. rubra, but T. ixioides and T. carnea in the Eastern states; in contrast, Bates (2011) states that in South Australia it is a hybrid between T. juncifolia and T. rubra.  However, without detailed genetic studies or breeding experiments these all remain suggestions.

Due to the transient nature of hybrids and the conditions needed to produce them, the named hybrids are not common, but since the 1890s specimens of Thelymitra x irregularis have been collected in every decade, which suggest that this hybrid readily occurs.  The 71 specimens held in the Australian herbaria have been collected from four states – which gives a good indication of the distribution but not necessarily the frequency of occurrence.  See Australia’s Virtual Herbarium (AVH) for details.  The AVH lists 12 herbarium records for South Australia with specimens collected from the Adelaide Hills, the Barossa Valley, Kangaroo Island and near Naracoorte.

Thelymitra x irregularis

This Thelymitra x irregularis or Pink Spotted Sun Orchid was photographed by Peter Watton in 2009 near Macclesfield, South Australia

The botanical name “irregularis” refers to the description of the column.  With many sun orchids, it is often necessary to observe the column to distinguish one species from another.  In this instance the top of the column is irregularly toothed.  Retired Aussie has some very good photographs with one in particular showing the column detail.

 

Thanks to Juergan Kellermann, State Herbarium of South Australia for his help with this post.

References

Bates (2011). South Australia’s Native Orchids. DVD-ROM

Bates & Weber (1990). Orchids of South Australia.

Jeanes & Backhouse. Wild Orchids of Victoria, Australia

Jones (2006), Native Orchids of Australia, 2nd edn.

Weber & Entwisle (1996). Thelymitra. In: Flora of Victoria, Vol 3.

Australia’s Virtual Herbarium accessed 24th September 2014