Over the years, we have recorded hundreds of different species of flora, fauna and fungi in the reserve. Among the rare and beautiful things that attract everybody’s attention (the snake’s head fritillaries, the scarce chaser or the visiting roe deer) are many smaller, more commonplace creatures and plants that we pass by without noticing.
The drama of snake’s head fritillaries and a beautiful early-morning roe doe.
This winter, as the reserve folds itself away until the spring, we are going to pick some of these little unnoticed things out of the species hat for a closer look.
Let’s start with Callitriche stagnalis, common water-starwort, a native to both Europe and North Africa that has invaded the slow moving waterways, ponds and lakes of most of the rest of the world. Away from the constraints of its natural habitat, it reproduces rapidly into dense floating masses that can out-compete native water plants and even overwhelm whole native ecosystems.
Like a lot of invasive alien plants, it was originally exported for somebody’s profit. If you google Callitriche stagnalis, half of the first page of results are garden centres trying to sell it to you as an oxygenating plant for your aquarium or ornamental pond. Once common water starwort has escaped from your pond into the wild, it spreads so quickly for two main reasons: firstly, it can grow in fresh or brackish water either below the water’s surface or floating on the top and, and secondly, it has a couple of very successful reproductive strategies.
Common water starwort floating on the surface by Harry Rose (CC BY 2.0)
Common water starwort floatation device by Stefan Lefnaer (CC BY-SA 4.0)
It is monoecious: it has male and female flowers on the same plant. Unlike most monoecious species, which only use self fertilisation as an emergency procedure, common water starwort’s male and female flowers bloom at the same time and are placed very close to each other in order to encourage self-fertilisation. Below each flower there is a bract that acts as a floatation device that keeps the maturing flowers above the water’s surface.
Besides making prolific self-fertilised seed, common water starwort can reproduce by fragmentation: break a piece off, give it the right habitat, and it will make a new plant, a clone of the parent. So, even if you safely remove the bulk of the starwort from your aquarium, every last little piece that remains in the water that you tip into the drain or a nearby stream has the potential to make a new plant.
In the reserve, our common water starwort is in its native habitat. It has to compete for space with other native plants and it is food for native aquatic creatures. It is a welcome member of our complex biodiversity.
Southwick Country Park Nature Reserve 