Thursday, 31 May 2012

Veronica colostylis

Veronica colostylis from near Arrowtown, New Zealand.
In autumn 2011 I wrote about Lammas flowering, when spring- or summer-flowering plants get fooled by a mild autumn into a second flowering.  This Veronica colostylis is doing just that in a pot at home today, but probably because it was transplanted in February from its home in the Arrow Valley near Queenstown, and it's a bit confused, poor thing.
Veronica colostylis flower (it's about 10 mm diameter).
Veronica colostylis is little more than a small-flowered form of V. linifolia, and in fact when I first described it it was as a subspecies, then under the genus ParahebeParahebe linifolia subsp. brevistylis.  Another botanist, Michael Heads, raised it to species rank later (as Parahebe brevistylis), and David Lloyd and I followed that when we published a monograph on Parahebe (Garnock-Jones & Lloyd 2004), and later (Garnock-Jones et al. 2007) when I transferred it to Veronica (it needed a new name because there was already a Veronica brevistylis).
Veronica colostylis in the Arrow Valley, New Zealand
When compared with V. linifolia, it's clear that the differences are quantitative only.  The flowers are a bit smaller, and the stamen filaments and the style are noticeably shorter.  The flowers have a lot less colour, and the short stamens hold the anthers very close to the stigma.  All these are adaptations to self-pollination, and it's no surprise that in the absence of insects, V. colostylis sets seed, while V. linifolia doesn't.
Veronica linifolia from Arthur's Pass, New Zealand.
So what does this mean about the appropriate rank for this plant?  If the differences are only quantitative (smaller parts with just the same structures), then they don't really provide evidence of any breeding barriers between V. linifolia and V. colostylis.  However, I never had much luck trying to cross them.  The only hybrid I managed to raise looked very like V. linifolia, so much so that I wouldn't have trusted it really was a hybrid except that its female parent was V. colostylis.  That hybrid had 37% of its pollen malformed, suggesting that there are genetic differences that lower fertility in crosses between them.  Additionally, the ranges of the two species overlap slightly in Canterbury, without any suggestion that they hybridize or intergrade there, so I'll stick with species status for now.
I saw V. colostylis again last summer, just downstream from the terminal face of the Franz Josef Glacier, New Zealand.

Garnock-Jones, P.J.; Lloyd, D.G. 2004: A taxonomic revision of Parahebe (Plantaginaceae) in New Zealand.  New Zealand Journal of Botany 42: 181–232.

Garnock-Jones, P.J.; Albach, D.; Briggs, B.G. 2007: Botanical names in Southern Hemisphere Veronica (Plantaginaceae): sect. Detzneria, sect. Hebe, and sect. Labiatoides. Taxon 56: 571–582

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