Mid-Holocene presence of water chestnut (Trapa natans L.) in the meres of Holderness, East Yorkshire, UK

Palaeoenvironmental and radiocarbon data are presented from an infilled freshwater basin (Lambwath Mere) in Holderness, East Yorkshire (UK). The site contains a rare and detailed c. 4000 cal. yr mid-Holocene pollen record for the floating-leaved aquatic plant Trapa natans (L.) (water chestnut). Competing hypotheses (natural and anthropogenic) to explain the earlier presence of this 'exotic' species in Holderness are evaluated. Maximum Trapa frequencies date to the interval 6200-4200 cal. BP and are shown to occur during shallow open water conditions just prior to overgrowth of the basin by semi-terrestrial vegetation communities. There is no clear palynological or archaeological evidence from the site to suggest settlement or significant human activity around the mere during this episode. It appears more likely that the occurrence of water chestnut at this site can be explained through natural factors (a combination of a favourable climate and the availability of a suitable habitat) rather than as a prehistoric human introduction.