Unwelcome biting turns Holly prickly

Holly and Berries

European Holly (ilex aqui­fo­lium). Photo: Jacinta Lluch Valero/Flickr

He might be endear­ing with his cheeky smile and sea­son­ally inap­pro­pri­ate antlers, but Rudolph and his more nasally-challenged cous­ins could be the reason why holly scratches you. It doesn’t have to hap­pen as, if you look closely, you’ll see not all holly leaves are prickly. What causes the spiky leaves? New research in the Botanical Journal of the Linnean Society blames a com­bin­a­tion of herb­i­vore activ­ity and epi­gen­et­ics for Holly’s spikes.

Heterophylly is often wit­nessed in holly trees, where some leaves are prickly, a defense against herb­i­vores, while oth­ers are non-prickly, with smooth mar­gins and no defense,” said author Dr Herrera. “We wanted to find out if this vari­ation was a response to envir­on­mental changes and if this took place without wider genetic change, that is, without alter­a­tion of the organism’s DNA sequence.”

They stud­ied the graz­ing by goats and deer and the reac­tion of European holly Ilex aqui­fo­lium. The res­ult was that there were many more prickly leaves between 0 and 2.5 metres, the range of a hungry red deer. The study showed that the res­ults cor­rel­ated with epi­gen­etic driv­ing the growth of prickly leaves.

An increas­ing num­ber of stud­ies sup­port the idea that the pres­ence of spines and prickles in plants is a response to herb­i­vore activ­ity, and our research sug­gests this is the case with holly,” con­cluded Dr Herrera. “The abil­ity of plants to respond to envir­on­mental changes through quick epi­gen­etic modi­fic­a­tions makes also one to feel a bit more optim­istic about plant sur­vival in a quickly chan­ging world.”

You can read more at the Linnean Society’s site or read the paper, pos­sibly for free, at Wiley.

Herrera C.M. & Bazaga P. (2013). Epigenetic cor­rel­ates of plant phen­o­typic plas­ti­city: DNA methyl­a­tion dif­fers between prickly and non­prickly leaves in het­ero­phyl­lous (Aquifoliaceae) trees, Botanical Journal of the Linnean Society, n/a-n/a. DOI:

Photo: Acebo “Jardin Botanico” de Madrid by Jacinta Lluch Valero. This image licensed under a Creative Commons by-sa licence.

Alun Salt. ORCID 0000-0002-1261-4283

When he's not the web developer for AoB Blog, Alun Salt researches something that could be mistaken for the archaeology of science. His current research is about whether there's such a thing as scientific heritage and if there is how would you recognise it?

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