Redistributing marine biodiversity – guest post from Jamie Hudson

I’m Jamie Hudson, a Marine Biology PhD student at the National Oceanography Centre in Southampton, UK. My research looks at the role different factors have in redistributing marine biodiversity around our coasts, notably climate change and hybridisation.

The ranges occupied by species are by no mean static- species are moving areas due to multiple reasons. There is a plethora of data that show our oceans are warming. Changing temperatures means species may have to move along the coast to more favourable environments. The outcome of this is that species are generally moving towards the north pole in the northern hemisphere, and the south pole in the southern hemisphere. When these species move to a new location, they can interfere with the current ecosystem and can lead to ecological or economic challenges- especially if these species are associated with aquaculture or other marine resources.

Additionally, species can also hitch a ride through human-mediated transport. Globalisation has meant we have never been so interconnected, and there are shipping routes connecting all parts of the world! Sometimes species stowaway on these ships, such as barnacles which attach to the underside of hulls, or crabs which may get sucked up in ships ballast water (water added into the hull of ships to improve stability). It’s thought that at any one time there could be up to 10,000 organisms being transported around the world by ships!

 

Now, when these species get transported to new locations and come into contact with similar species, something amazing can happen – hybridisation! Whilst this may conjure up images of mythical beasts such as Pegasus the winged horse, hybridisation between species is very much real (and quite common). For example, grapefruit is actually a hybrid of a sweet orange and pomelo (a southeast Asian citrus fruit). “But when two different species breed aren’t the hybrids are sterile?” you may ask. Indeed, sometimes hybrids are sterile, as is the case with mules (the offspring between a male donkey and female horse), but sometimes hybrids are able to reproduce and sustain a population. Indeed, it was recently shown that a species of dolphin in the Atlantic (the Clymene dolphin) is actually a hybrid formed from two other distinct species!

 

So, what makes hybrids interesting to study? Well, sometimes these hybrids can exhibit features or traits which are extreme to either parent! In the 1800s a species of cordgrass (grass found around salt marshes) was accidently introduced to Southampton from North America (through ballast water), where it interbred with a native species. This led to the formation of a new species – Spartina anglica. This hybrid species can tolerate a much wider range of environmental conditions than either parent species, and has since spread its range around the coast of Great Britain- it is now the most commonly found species of cordgrass along our coasts!

 

Studying how these hybrids may be able to survive changing conditions associated with climate change is an important step in exploring what may be driving the shuffling of biodiversity we currently see.