Patrolling the Scottish Border – plant migration history

Michael E Braithwaite

doi:10.33928/bib.2020.02.335

Abstract

There have been successive waves of plant migration north across the Scottish Border since the end of the Ice Age. For those species that never penetrated far into Scotland and which lack specialised means of long-distance dispersal, the distinctive distribution patterns shown by BSBI’s tetrad mapping provide evidence of the likely dates and dispersal mechanisms of the migrations, separating out migration relating to man’s activities. Twelve distribution maps have been prepared for native or archaeophyte species that illustrate contrasting histories. Conclusions are drawn as to whether or not species which lack specialised means of long-distance dispersal are able to migrate north over fragmented natural habitats in response to climate change.

Highlights

My botanising in the Scottish Borders spans fifty years and I have had the privilege of witnessing many changes in the flora at first hand
It has occurred to me to investigate whether the distinctive patterns of the tetrad distributions, available online at the BSBI’s Distribution Database (DDb), throw light on the migrations of other species that have crossed the Scottish Border over the centuries
The discussion of Lysimachia vulgaris, which has been spreading along riversides, suggests that two ecotypes are involved, a declining native ecotype of fens and a recently-arrived robust ecotype whose history is unclear, though it may have colonised the River Tweed from the River Tyne in Northumberland from seed ingested by birds and, if that is so, it does not strictly qualify for selection here, but is retained because of the issues that have come to light concerning its history

Summary

Introduction

My botanising in the Scottish Borders spans fifty years and I have had the privilege of witnessing many changes in the flora at first hand. I have searched in vain for native species that appear to have migrated north to Scotland more recently than the Neolithic period without assistance from man’s activities, unless they have specialised means of long-distance dispersal.

Results

Conclusion