Forensic botany collection

Image: Wikimedia Commons.
Image: Wikimedia Commons.

I don’t know what the rest of the world’s TV is like but the USA and the UK– and Denmark– seem obsessed with crime dramas, especially those that explore the role of forensics in catching wrong-doers. To that end there is an almost daily avalanche of CSI (Crime Scene Investigation)-themed programmes, most of which emphasise animal dimensions to the science. Well, by way of redressing the balance and extending it to other evidence-gathering areas, here is the first of an eclectic series of episodes for an unlikely-to-be-commissioned-because-most-people-don’t-think-plants-are-interesting-enough-but-what-the-heck-let’s-pitch-it-anyway series, whose rather catchy working title is ‘CSI Evidential Botanicals’.

CSI Herbaria

Leaf miners are so-called because they tunnel through the mesophyll of leaves as they consume the cholorenchymatous tissues, i.e. they mine the leaf. Their feeding activities reduce the photosynthetic area of the plants they attack and may open the plant to other invading organisms and ailments. Rightly, therefore, the herbivores are generally regarded as pests that need to be controlled. One such invasive insect inmate, the horse chestnut leaf miner (Cameraria ohridella), is currently causing major infestations of Aesculus hippocastanum (the aforesaid horse chestnut) in Europe. However, although first noted in Europe in 1986, nobody was sure where the miners had originally come from, which ignorance hampers attempts to identify their natural predators, which could be exploited as bio-control agents. Help in tracking down the miners’ ancestral home came from a very unusual sourceherbarium samples collected as long ago as 1879. Not only did those samples contain preserved leaf-miner larvae, but those incarcerated insects yielded sufficient nuclear and mitochondrial DNA barcode fragments to reveal that their ultimate geographic origin was the Balkans (to discover how this was deduced you’ll have to read the paper!). As David Lees et al. (Frontiers in Ecology and the Environment) conclude: ‘this case history demonstrates that herbaria are greatly underutilized in studies of insect–plant interactions, herbivore biodiversity, and invasive species’ origins’. Underlining the importance of herbaria in providing an important temporal dimension to current studies is the case of Australian protista (and if MS Word in its finite wisdom autocorrects that to ‘protests’ I’ll be mightily irked!). Thomas Wenberg and colleagues (Current Biology) are interested in any effects that global warming might have on the distribution of macroscopic photoautotrophic protists (that’s seaweeds to the rest of us). Even though seaweeds are reasonably large there are probably no large-scale satellite records of their distribution now and several years ago. But there are herbarium records, which can be examined to assess historic distribution and abundance, which can be compared to present-day biogeographic data. Interrogating >20,000 herbarium records of macroalgae collected in Australia since the 1940s, the team identified changes in communities and geographical distribution in both the Indian and Pacific Oceans, consistent with rapid warming over the intervening 50 years. Interestingly, the team actually used records from Australia’s Virtual Herbarium (AVH), ‘an online resource that provides immediate access to the wealth of plant specimen data held by Australian herbaria’ for their study. The AVH is a publicly available database containing the location and year of collection for a substantial part of the 6 million algae, fungi and plant specimens inAustralia’s nine major state herbaria. On a less serious note, herbaria can also have a human temporal enlightenment and sociological role. Students at Canada’s University of Alberta learnt as much about botany as they did about recent North American human history when they unwrapped newspaper-swaddled plant specimens that had been donated to the university. Some of the pages of newsprint dated back to the 1950s and 1970s with stories about the Korean War, the Vietnam War, and a certain Mr Richard Nixon (whatever happened to him? Hmmm, tricky one…). Which all goes to show that botany really does broaden your mind, sometimes in unexpected ways.

Episode 2 – and more – of ‘CSI Evidential Botanicals’ to follow…