Endemic Daisybushes, endemic hybrids?

Hybridization as a means of making new species is not an uncommon concept and hence it must be applicable to other species. I present a case using a Tasmanian example – the Olearia daisybushes.

Olearia is a large and conspicuous genus of shrubs in the sunflower or daisy family (Asteraceae) with some 23 species in Tasmania of which 8 are endemic to Tasmania (not counting subspecies).

Left: Geebung Daisybush (Olearia persoonioides); Right: Prickly Daisybush (Olearia pinifolia); Centre: Possible hybrid

Two of the endemic species are of interest in this post: Olearia persoonioides (Geebung Daisybush) and Olearia pinifolia (Prickly Daisybush). Both are common and largish daisybushes that grow in subalpine woodlands.

Whilst botanizing at various spots around the Central Highlands I stumbled upon the two species of daisybushes growing in close proximity in the understorey of a eucalypt woodland. They were both in full flower. At the same time I also noticed numerous specimens that looked like intermediates between the two.

While this intermediate specimen deserves much more detailed study, I have prepared a set of photographs and made a table of the characters comparing the two daisybush species with the intermediate specimen.

Geebung Daisybush Possible Hybrid Prickly Daisybush
Leaf shape Elliptic to obovate,
c7mm at widest
Narrowly elliptic,
4.5mm at widest
Narrowly linear, c2.5mm at widest
Leaf margins Entire, occassionally
mildly recurved
Recurved margins Strongly revolute,
leaves becoming cylindrical
Leaf apex Pointed but not pungent Mildly pungent Strongly pungent
Inflorescence 3-5 flowers sharing
a common stalk
Flowers mostly borne
singly in leaf axils but
occassionally 2 flowers sharing a common stalk
Flowers borne singly
in leaf axils
Flowers Disc c2-2.5mm at widest,
pappus white colored
Disc c3.5mm at widest,
pappus white colored
Disc c4.5mm at widest,
pappus purple tinted,
particularly at tips

Many additional aspects of the morphology of the intermediate specimen deserves study. For example, the morphology of the flowers and fruits (achenes) needs to be examined in greater detail. Other studies like chromosome counts might also be helpful in determining the hybrid status of the intermediate specimen.

A trip to the herbarium is in the works!

About David Tng

I am David Tng, a hedonistic botanizer who pursues plants with a fervour. I chase the opportunity to delve into various aspects of the study of plants. I have spent untold hours staring at mosses and allied plants, taking picture of pollen, culturing orchids in clean cabinets, counting tree rings, monitoring plant flowering times, etc. I am currently engrossed in the study of plant ecology (a grand excuse to see 'anything I can). Sometimes I think of myself as a shadow taxonomist, a sentimental ecologist, and a spiritual environmentalist - but at the very root of it all, a "plant whisperer"!
This entry was posted in Asteraceae, Botany, Common and Unappreciated, Hypotheses, Key Characters, Plant Morphology, Shrubs, Tasmanian Endemics and tagged , , , , , , , , , , . Bookmark the permalink.

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