Some of us, like myself may be having difficulty in correctly identifying hirpicium bechuanense and hirpicium gorterioides. I have taken the liberty of collecting together some pertinant comments and messages on this problem.
1 First however a name change for the hirpicium of Botswana is being considered and a decision by Kew and Plants of the World Online POWO is being awaited.
The proposed genus name change for Botswana's hirpicium to roessleria is found in this paper.
South African Journal of Botany 2018 118 216-231
Intergeneric relationships in the Gorteria clade of Arctotideae-Gorteriinae
(Asteraceae), with description of a new genus, Roessleria
F. Stångberg a,b P.O. Karis a, , A. Anderberg b
This paper has a map for the various sp of hirpicium and only has h bechuanense in Eastern and SE Botswana and former Transvaal up to Bulawayo and then h. gorterioides from Bulawayo, N and NW Botswana and Namibia SW Angola so quite different distributions with no sign of overlap except in Zim !,
2 Useful comments on the two species from @Bartwursten
a) It is very important to know whether this was a perennial herb (H. bechuanense) or an annual (H. gorteroides). Both occur in Southeastern Botswana and are similar.
b) What we need to know is if your plant is a perennial or not. If it is pulled up easily with the roots and has a small and weak root system it is likely annual. If it has a strong and solid or deep root system and can not be pulled up roots and all it is likely a perennial.
c) GBIF should not be used for comprehensive distribution as it only shows the records they have in their database for a species which is not comprehensive. As you can see it does not have it at all for Zimbabwe where it is in fact the more common of the two. Literature such as Flora Zambesiaca does cite H. gorteroides for SE Botswana as well as H. bechuanense based on existing and referenced specimens.
- Extract from a private message from @robert_mck
'I have asked Frida if there are reliable features to distinguish Hirpicium bechuanense and H. gorterioides other than annual/perennial habit. Unfortunately, she didn't publish a key to the species. I have followed Flora Zambesiaca, which indicates the following differences in the outermost bracts surrounding the flower head:
bechuanense: outer bracts 4–7 mm long with 2–5 lateral spines;
gorterioides: outer bracts 8–12 mm long, with 10-20 lateral bristles.
In the photos I've seen of plants IDed as gorterioides, the difference in density of bristles on the outer bracts is very clear. Also, the upper leaf surface might be more bristly than spiny in gorterioides, but I don't know if that is a universally reliable difference. You are perhaps in the best situation to test whether these characters are reliable in SE Botswana. My only firsthand experience in Botswana is of what fitted the description of bechuanense in the Mochudi area, based on the outer bracts. I noted the leaf form varied markedly - some plants had lobed leaves, others had only simple (unlobed) leaves. Based on Frida's distribution map, gorterioides may be predicted to be very rare in the SE and most common to the north and bechuanense is by far the dominant species in SE Botswana. Maybe rainfall is lower or more strongly seasonal in the north?
If the two species co-exist, then hybridisation is a very real possibility, which would cause local occurrence of intermediate forms, but then spatially isolated populations would remain pure and be readily distinguishable.
More in a private message from robert_mck on 21.6.20
I also located an article from 1975 in the journal Kirkia, which included an identification key to the seven Hirpicium species that occur in the Flora Zambesiaca area. In addition to the outer bract length and number of marginal spines/bristles that I mentioned yesterday, it also used the relative length of the uppermost leaves, which conspicuously extend beyond the flower head in gorterioides but not in bechuanense. A quick survey of the photos I have on hand suggests this seems to be useful for identification in combination with the other features.
With all that in mind, the observations https://www.inaturalist.org/observations/44492218 and https://www.inaturalist.org/observations/12732425 seem consistent with bechuanense.
It is wonderful that you are taking an interest in the plants. Botswanan plants are generally neglected, so I really do encourage you to continue and hope you have a core group that can explore regularly. Often the amateur botanists, who are on the ground and have the time and means to explore, know far more than the professionals and can make a huge contribution to botanical knowledge. And there are still many botanical problems to resolve, and no doubt problems still to be discovered.
The important features for identification vary among and within families and cannot always be easily photographed. With daisies I would try to photograph a whole plant to show the growth habit, in my group the basal leaves often differ from the upper leaves on the stems, a view of the stem to show the leaf arrangement and hairs on the stem, leaves (the upper and lower surfaces to show hairs etc., and the leaf tip and base are sometimes important), the bracts around the flower head are extremely important in the family, a face view of the flower head which provides information on floret types, colour, and the style form, and if there is an old head with mature fruit a close-up can be crucial to show the fruit shape, size, hairs, and the pappus (the crown of hairs or scales at the top of the fruit). The more you can show in one photo, the simpler and quicker, of course.
I have been working on genetic studies of the species I mentioned yesterday, Arctotis venusta, A. arctotoides and Haplocarpha scaposa, because they are widespread and each may have an interesting biogeographical history. The outlying populations in southern Botswana are interesting. Peripheral or outlying populations might represent refugial populations that have become isolated and are diverging or have already diverged, or they might be recent range extensions. I think it would be extremely interesting to look at the differences in plant species distribution patterns in Botswana from a biogeographic perspective, I'm not aware of anyone having done so previously. The Kalahari and Okavango regions are obviously specialised ecosystems, but why the difference in species between the north and south?
Thanks so much Bart Wursten and Robert McKenzie for all this invaluable info to help us Budding Botanists of Botswana get to know the tricky genus hirpicium ( or Roessleria as it may soon be).
Looking forward to more updates and comments on this often seen genus !
Tony Benn (aka Botswanabugs)
