Can mere mistletoe presence increase biodiversity on the ground below? That seems an odd concept but, actually, studies over several years on mistletoes in warmer countries, and particularly on Australian mistletoes, have shown this to be the case. The impacts are mainly to do with nutrient-enriched leaf litter under the infected host tree, which alter local vegetation on the ground and increase faunal diversity within that litter. It can be so significant that such mistletoes are seen as ‘keystone’ species in the local ecosystem.
But, until recently, there have been few studies of this phenomenon for ‘our’ mistletoe, the European Viscum album. Does this have similar benefits? Is this also a ‘keystone’ species of the open woodland ecosystem? Or is it just a parasite of the trees with a few dedicated species (a handful of unusual insects that feed directly on it, plus berries as food for some birds)?
Well, a recent study in Spain seems to have the answer, looking specifically at Viscum album, though not quite ‘our’ version. It was the subspecies of ours (ssp austriacum) that lives on pines in southern Europe – specifically, in this case, in the Sierra de Baza Natural Park in SE Spain.
And the good news is that yes, mistletoe presence does increase diversity on the ground. Not quite the exotic species recorded under some of the mistletoes down under, but definitely an increase. The ground under mistletoe-infested trees had differing vegetation, better soil cover and increased general biodiversity including, most obviously, larger numbers of rabbits. Because better ground vegetation = better rabbit food.
This may seem more modest than the increased diversities seen in Australia, but it is very good for bunnies.
What we need now is a similar study in Britain using our subspecies, Viscum album ssp album which grows on deciduous trees. And see if it helps more than bunnies. It would be tricky to carry out though, as we don’t have the uniform mistletoe habitats – scattered trees of uniform species, some with, and some without, mistletoe – comparable to that sampled in Spain. The closest we might have is orchard habitat, but orchards are agricultural land where there are many other factors to consider.
Read all about the Spanish study here: https://link.springer.com/article/10.1007/s13595-018-0761-3