Euphorbia marlothiana: a closer look

Throughout my blogs I have referred to this plant as Euphorbia marlothiana…however  E. marlothiana has been merged into the species Euphorbia caput-medusae, so for future reference it will be referred to as the latter.

Euphorbia caput-medusae

In the previous euphorbia blog (http://uwcnaturereserve.blogspot.com/2014/06/euphorbia-marlothiana-theory-continues.html), it was stated that E. caput-medusae was data deficient (IUCN Red Data List 2009), however, the latest status (IUCN Red Data List 20/05/2014) have indicated that this species is currently of Least Concern.   According to R.H. Archer, L. von Staden, J.E. Victor & D. Raimondo, this species is widespread and no longer in danger of extinction with a stable population.

So why continue studying this plant that no longer seems ‘important’ you ask…

…because the Cape Flats Nature Reserve only has eight very small stands of E. caput-medusae situated in the Dune Strandveld section.  They have shown slow growth in population size since the observations began in February 2013.  The growth form of the euphorbia is being observed but what about other methods of reproduction…  The cages mentioned in the previous blog have been removed because of my theory that they need some form of disturbance to maintain their natural growth form.  This was also to allow some form of animal disturbance in the hope that pieces of the plant would break off and grow a new stand where it fell.   Due to its succulent nature, this is thought to be the most obvious form of reproduction. Another form of plant reproduction is seed production (image 1). 

Image 1

However, it was observed that the seeds were always missing from the seed pods.  Each seed pod examined had a tiny hole in it (image 2)

Image 2

Upon further investigation, we discovered a larva in each seed pod (image 3).  Could this be from a parasitic insect?  This larval activity was seen during February 2014.  The seed pods found during July had holes in but were empty.

Image 3

Pollinators of the euphorbia are being observed but of particular interest is the one parasitizing the seed pods.  More importantly…could this possibly be a reason that E. caput-medusae may not reproduce via seeds and potentially have a long term negative impact on the expansion of the population in the Cape Flats Nature Reserve? (A very interesting research topic indeed)

Follow the next Euphorbia blog for more info on how the UWC Nature Reserve Unit is trying to prevent this species from becoming locally extinct within this reserve.