ACKNOWLEDGMENTS
We thank Natural England for permits and landowners for access to populations; Lindsey and Derek Cullen for accommodation and assistance during fieldwork; Markus Meierhofer and Rayko Jonas for help in the greenhouse; Francesco Rivetti for assistance in the laboratory; Members of the Conti group for fruitful discussions. We thank Kathryn Hodgins and three anonymous reviewers for their comments that greatly improved this manuscript.