#40 Tansy Beetle by Geoff Oxford
Meet Dr Geoff Oxford, Honorary Fellow at the University of York!
Geoff Oxford (geoff.oxford@york.ac.uk) is currently an Honorary Fellow in the Department of Biology, University of York, where he taught genetics and evolution for nearly 40 years. Although his main interest is in spiders (you can read his previous blog here), he became fascinated by the Tansy beetle some 30 years ago when his wife, Roma, started to breed them … and began to ask questions. This led to two Ph.D. research studentships and a number of Masters projects studying the biology and conservation of the beetle. In 2008 he, Roma and representatives from relevant statutory authorities formed the embryo Tansy Beetle Action Group (TBAG) to coordinate the species’ conservation. He continues to engage with Tansy beetle research and TBAG’s activities.
A Tansy Beetle Chrysolina graminis is the size of a little-finger nail (about 10 mm) and in appearance quite stunning, with an iridescent, green body that glints red, bronze and blue depending on the angle of view. The beetle is IUCN Red Listed as Endangered in terms of extinction risk in England. The natural history information in this blog refers to the populations on the Yorkshire Ouse, the subject of most research.
Female Tansy Beetle on one penny coin © Geoff Oxford
The ‘Jewel of York’ is no longer an entirely accurate name for this beetle! When Geoff started working on the Tansy Beetle, the banks of the river Ouse either side of York housed what was thought to be the only population in Britain and someone (we know not who) came up with the brilliant epithet ‘The Jewel of York’. Populations of the species were also known, in historical times, from the East Anglian Fens but they had disappeared from there, one by one; the last recorded, as far as records knew, was from Wicken Fen, Cambridgeshire, in the latter half of the 1980s. To the utmost surprise and delight of Geoff and his colleagues, the beetle was rediscovered at Woodwalton Fen in 2014, after an apparent absence of over 40 years. In 2018, a second, new population was found at the WWT Reserve at Welney on the Ouse Washes, West Norfolk. With two known populations in the Fens, the conservation status of the beetle is more assured, but that leaves the popular ‘Jewel of York’ name something of a misnomer.
As the common name suggests, the Tansy Beetle in Yorkshire eats predominantly Tansy Tanacetum vulgare, a tall aromatic plant with yellow, button-like flowers, which grows in large, adjacent patches along the banks of the river Ouse. Beetles overwinter as adults, deep amongst the roots of Tansy clumps, emerging above ground in March. They feed on young Tansy leaves, mate and lay small batches of usually pale-yellow eggs on the underside of Tansy leaflets but also, counterintuitively, on adjacent non-food plants such as grasses. The eggs hatch into beige, slug-like larvae, which also feed on Tansy. In late June, the larvae head underground to pupate within an earth cell. A month later, the new generation of adults appears, by which time the old, overwintering generation has largely died. The new adults feed, and occasionally mate, before disappearing underground again in late September to hibernate.
The new (August) generation of beetles is surveyed by TBAG each year and the total numbers on the river Ouse estimated (see Monitoring below). Mapping the distributions of Tansy and Tansy Beetles are critical for understanding the ecology of the beetle and its principal food plant, and for informing conservation strategies. For example, the beetle exists as a meta-population – sub-populations on individual clumps disappear for various reasons but are then re-colonised by dispersing individuals. Because beetles mainly walk between Tansy patches, stretches with little or no Tansy or with clumps more than 150 m apart act as impediments to this dynamic process. Identifying these food-plant poor regions during surveys allows targeted planting of new Tansy clumps and the re-establishment of connectivity.
Female Tansy Beetle on Tansy flowerhead.
Threats to local Tansy Beetle populations include flooding (especially during the spring and summer), overgrazing, invasive plants (such as Himalayan Balsam Impatiens glandulifera, which can outcompete Tansy) and mismanagement of banks. TBAG (via the Species Recovery Trust) is now working more closely with riparian landowners and managers to provide bespoke feedback from annual surveys and tailored advice on making their banks more beetle friendly. To consider a couple of the threats, the establishment of Tansy clumps, and beetles, within post and rail, stock-proof enclosures in areas with serious overgrazing has proved extremely successful on some stretches. Flooding is a problem that is likely to exacerbate in the future. To prevent a major summer flood from destroying the entire beetle population on the Ouse, several ‘ark’ sites have been established, providing sub-populations as close to the river as possible but beyond the limits of flooding. Some are flourishing – one has an estimated several thousand individuals.
The Tansy Beetle in York has long been known to certain sections of the community, for example Victorian (and almost certainly some present-day) beetle collectors and generations of pupils of St Peter’s School, York. As one of the latter, Michael Shannon later recalled: “I remember going to Clifton Ings during the summer term in the 1950s to collect Tansy Beetles. We never had any problems finding them – some plants could have twenty or thirty. We would put them in a shoebox with some leaves and take them home or to school. We held Tansy Beetle races along two pieces of taut string although I do not recall any champions, or any big bets being wagered.”
From the start, TBAG tried to promote the Tansy Beetle more widely as a beautiful, inspiring and locally occurring invertebrate, of which York should be proud. In addition, the species serves as an iconic figurehead, representing perhaps less immediately attractive British invertebrates that are also of conservation concern. An ‘educational’ population sited in the Yorkshire Museum Gardens attracts much attention and interest from locals and visitors alike. The beetle’s profile was further enhanced in 2019 by a giant, Crowdfunded image painted by ATM Street Art on the gable end of a house near York’s railway station, and the naming of a cocktail bar ‘The Tansy Beetle’ in a York restaurant.
Clumps of Tansy along the river Ouse © Geoff Oxford.
Recording and monitoring
The Tansy Beetle was recognized as a UK Biodiversity Action Plan Priority Species in 2007 and is currently listed in Section 41 of the Natural Environment and Rural Communities Act of 2006. In 2014, the UK Red List of Britain’s seed and leaf beetles was reviewed. The Tansy beetle was heading for a Critically Endangered (CE) designation – we successfully argued that the array of sub-populations on the Yorkshire Ouse were, from the point of view of a catastrophic summer flood, essentially a single entity. Before designations were set in stone, the Woodwalton Fen population was rediscovered, necessitating moving the beetle to the Endangered (E) category.
One of the first actions of the newly formed TBAG in 2008 was to initiate annual surveys of Tansy Beetles and their food plant on the Yorkshire Ouse. Volunteers adopt specific stretches and on warm days in August systematically walk the bank, noting the location and size of Tansy clumps and the numbers (if any) of beetles seen. In this way, information is gathered along some 45 km of river (90 km of bank) stretching from Linton Lock in the north to Selby in the south and covering the entire range of the Yorkshire beetle population. These surveys allow an estimate of beetle numbers and comparisons over time. Although calculating total beetle numbers is not an exact science by any means, to date the minimum estimate was for 2012 (4,000) and the maximum for 2016 (35,000). Although we still do not fully understand the reasons for such marked fluctuations in numbers between years, summer flooding does seem to be a significant factor – 2012 was claimed by one source to have the wettest summer since 1766.
Although rough and ready, quantitative data such as these are extremely unusual for an endangered species and were influential in determining the species IUCN Red List designation (see Conservation status above). Full survey results are submitted to NEYEDC and an annual report compiled each year.
Further information and acknowledgements
NEYEDC would like to thank Geoff for his time and expertise in helping to create this blog. For further information: https://www.speciesrecoverytrust.org.uk/tansy-beetle.
Tansy Beetle mural on Queen Street, York © Geoff Oxford.