Searsia pterota - what to look for

In a previous Journal post 'The hunt for Searsia longispina', reference was made to a journal paper by R.O. Moffatt in which he deals with the confusion between Searsia longispina and Searsia pterota, two species which I had mixed up for a long time. The paper by Moffatt can be found in the link below:

https://www.sciencedirect.com/science/article/pii/S0254629916306597

My hunt for S. longispina is ongoing at present, and my journal post detailing that hunt can be found in the link below:

https://www.inaturalist.org/journal/galpinmd/85712-the-hunt-for-searsia-longispina

For years I had referred to Searsia pterota (hereafter referred to as Pterota) as Searisa longispina but once I was made aware that the two species were not at all related, it became much easier to identify Pterota. It is a species that is quite common in the areas that I explore (the south eastern cape - the area between Gqheberha(Port Elizabeth), Buffalo City(East London) and Makhanda(Grahamstown) and I have found it to be one of the easier Searsia species to identify in the field. That being said, identifying specimens in photographs can be challenging as photos don't often show all the features that would set Pterota apart from other species.
Just a note: Some of the plants pictured in the links that follow are plants photographed beyond the borders of the area I explore.

In the next part I'll go into some detail with regards to descriptive terms, relying on R.O. Moffatts work on the Searsia genus. This is useful as a reference for identifying Pterota but if you're just wanting the basics, or the most useful features that I tend to rely on, you can skip to the summary section and always refer back to the 'technical' section for the features described.

Just a note: Where links are provided, the photo or photo's that best depict the feature being referred to will be numbered e.g. 'Photos 2, 3 & 4 in the link'. I have found this process to be a little cumbersome as I often forget what the number of the photograph was that I needed to look at, and then end up going backwards and forwards between the Journal post and the observations in the link! My advice is to go slowly and open one link at a time - and have a cup of coffee and a rusk on standby next to you!

THE LEAVES

• Leaves are trifoliate (the leaf is made up of three leaflets, a terminal leaflet-in the middle, and two lateral leaflets-one on each side of the terminal leaflet)
  Photos 7, 8 & 9 in the link
  Trifoliate leaf

• Fasciculate (a bundle or cluster of leaves crowded together)
  Photos 2 & 8 in the link
  Fasciculate leaves 1
  Photo 3 in the link
  Fasciculate leaves 2

• Petiolate (leaflets are connected to the stem by a petiole)

• Petiole winged (from the Greek word 'pteron' meaning 'winged' - this is how Pterota got it's name)
  Photo 1 in the link
  Winged petiole 1
  Photo 6 in the link
  Winged petiole 2
  Photos 3 & 5 in the link
  Winged petiole 3
  ** Some plants can have markedly winged petioles, but the plants in the links above give a good idea of what one will usually find in my opinion

• Rigidly coriaceous (rigidly leathery - the species has quite a tough leaf)
• Slightly discolorous (darkish green on the upper surface, slightly lighter on the underside - no big difference in colour btw the upper and underside)
• Glabrous (smooth i.e. no hairs)
• Lamina elliptic to obovate (Lamina = leaf blade; elliptic = an ellipse, widest in the middle and tapering toward each end; Obovate = teardrop shaped, with widest part near the tip, tapering toward the base)
• Apex rounded (tip of the leaf isn't pointy)
• Base cuneate (base is wedge shaped where it meets the petiole)
• Margin entire and revolute (Entire = smooth edge i.e. no serrations, teeth etc; Revolute = margin folds downward along its edge)

• Venation kladodromous (a very useful feature - basically means that the veins divide or branch toward the margins; 'klados' from ancient Greek meaning 'branch' and 'dromos' an adjective from Greek meaning 'a running' Think of the Hippodrome of ancient Rome - a horse racing track)
  Photo 7 in the link
  Kladodromous leaf venation 1
  Photo 7 in the link
  Kladodromous leaf venation 2

• Veins dull yellow in colour (a useful feature)
  Photo 1 in the link gives a good overall impression of venation colour
  Leaf vein colour

• Secondary veins often reversed (in other words some veins often reverse direction, away from the margin, back towards the midrib)
  Photo 7 in the link
  Reversed leaf venation

• Secondary veins 2-3 per cm (worthwhile keeping in the back of your mind when it comes to comparing between Searsia species)

• Leaflet size in mm (Terminal leaflets average 25 x 10; lateral leaflets average 19 x 9 - length/width - there is quite a big variation in size, even on the same tree!)
  Photo 6 in the link
  Leaf sizes

THE DRUPE (fruit)

The drupe is not always seen in the field especially if a person is only visiting an area for a short time, as one has to be around when the plant is in fruit. Drupe features can be critical in identifying Searsia species, especially when a **key is used. Moffatt used two words to describe Searsia drupe shape, the first word used describes the shape as viewed on its widest face and the other, its thickness, or the shape perpendicular to the widest face.
**A key is a tool used to identify an organism and is made up of a sequence of choices between two or more statements

So here goes for drupe features

• Elliptic (widest in the middle and tapering toward each end- remember this description refers to its widest face)
• Ellipsoid (according to Wikipedia this is a 'three dimensional shape that is elliptical in all sections through the long axis'. I would imagine that if you had to cut the drupe in half while viewing it's thickness, the flat surface that you would see would be elliptic in shape)
• Slightly asymmetric (so not quite an evenly shaped ellipse)
• Glabrous (Smooth)
• Shiny
• Fleshy
• Colour: dark reddish brown drying black

• Pungent and unpalatable (other Searsia drupes can taste quite pleasant - a bit tart, but refreshing. In the case of Pterota however, I'd suggest you draw straws to see who gets to try!)
  See photos of fruit in links
  Pterota drupe 1
  Pterota drupe 2
  Pterota drupe 3

GROWTH HABIT (architecture)

The descriptions given in Moffatts work are as follows:

• A much branched, armed shrub (it has spines) , branching squarrose (bending outward or downward at the tip), short shoots ending in sharp spines.

• Young growth russet coloured
  See photo in link
  Russet coloured growth

• Bark: grey, granular and often lichen covered

DISTRIBUTION
The following description of Pterota's distribution is a direct quote from Moffatts work:
"Ranges along the coast and adjacent interior from East London to the De Hoop Nature Reserve near Bredasdorp in the southern Cape with a disjunct population 250 km further west in the Postberg Nature Reserve near Saldanha Bay"

The distribution of Pterota observations on iNaturalist can be found in the link below
Distribution map

SUMMARY

The two most useful characteristics that I use to identify Pterota are its leaf characteristics (shape, venation and petiole features) and habit (the architecture of the plant).
This species tends mostly to grow in amongst other shrubs, as opposed to out in the open by itself, and its presence is most often given away by spiny branches (sometimes quite long) protruding from a clump of shrubs usually at, or close to, the edge of the clump. This is the one species of Searsia in my area which will poke a hole in you and draw blood if a branch whips back and hits you!
Photo 1 in the link for growth habit
Growth habit 1
Photo 2 in the link for growth habit
Growth habit 2
Photos 2 & 4 for spines
Spines

The ability to identify species based on what is termed 'GISS' (General Impression of Shape and Size) takes time and, if you don't know this species well, will require one to get 'up close and personal' as opposed to being able to identify it from a distance. The most useful features for an 'up close and personal' investigation of the shrub are listed below (in order of importance to me)

• Leaf venation - untidy venation, yellowish veins that branch (kladodromous) - they get squiggly toward the margins
  Photo 7
  Leaf venation

• Long, winged petiole (watch out for this one - if it's there, it's easy to identify this species, if not, go back to venation
  Photos 2, 6, 8 & 9 in the link (notice in photo 1 that the petioles are not very obvious, but the venation gives the species away)
  Winged petiole 1
  Photos 3, 5 & 6 (notice in photo 6 the variation in leaf petiole length)
  Winged petiole 2

• Fasciculate leaf growth (a bundle or cluster of leaves crowded together)
  Photos 2 & 8 in the link
  Fasciculate leaves 1
  Photo 3 in the link
  Fasciculate leaves 2

• Leaf shape (elliptic = widest in the middle and tapering toward each end, to obovate = shaped like an upside-down tear drop)
  See photo's of leaves in the two links for an idea of leaf shape in this species
  Leaf shape 1
  Photo 6, second leaf from the left, the terminal leaflet is a good example of an 'elliptic' shape
  Leaf shape 2

• Sharp spines
  Photos 2 & 4
  Spines

• Main stem with lichen covered bark and some nasty spines
  Photo 2 in the link
  Main stem and spines

The post above is not meant to be taken as an authoritative post on Pterota. It includes details from the work of R.O. Moffatt, a man I consider as the authority on Searsia, and input from people with far more experience and knowledge than I have, but it still includes my own limited, local knowledge and understanding of the species. I'm sure I'll be amending this post as time goes by but for now that should be enough to get anyone started on identifying Pterota. Enjoy the journey - and don't give up too soon!

Publicado el octubre 26, 2023 10:25 MAÑANA por galpinmd