Thursday, August 16, 2012

A Cheeky Monkey Invader Makes a New Species

Monkeyflower, Mimulus guttatus
Although invasive alien species do threaten native species through competition, one which provides a little compensation in terms of colour is the Monkeyflower, Mimulus guttatus. A pretty, yellow flowered member of the Scrophulariaceae it was introduced to Britain from North America c. 1812, becoming established in the wild by 1824 (1) and making its way across to Ireland soon after. It was first recorded in Co. Cork on the River Bandon prior to 1866 and is now widespread on many of the major waterways within the county (2). As such, it is a paludal species that is quite at home in such wet places that mimic its native north western American home. It has even its home along the river walls of Cork city, with populations visible next to South Gate Bridge and Clarke's Bridge. Growing no more than 20 cm tall (3) it is a perennial, fully seed fertile species, but local colonies are formed by stolon growth. Thus, once established, colonies can grow quite easily. Such ability to colonise has made M. guttatus quite a successful alien and it is now established in New Zealand and 16 European countries (4).
M. guttatus
easily hybridises with other Mimulus species, and while this has been put to use in the development of new garden varieties (some, such as Mimulus × robertsii, have escaped and are now themselves invasives), it is incredible to hear that a hybrid of M. guttatus and a South American relative M. luteus found in the wilds of Scotland has been deemed a new species (4). M. peregrinus, as it has been named by its discoverer Mario Vallejo-Marín of the University of Stirling, Scotland, is fully pollen and seed fertile unlike many other hybrids which are sterile on both accounts. This is seemingly a result of the polyploid nature of M. peregrinus (2n = 6x = 92): previous sterile hybrids have all been triploid . The evolution of this species gives an intriguing glimpse at the possible future for some of our naturalised aliens.

  1. Truscott et al., 2006. Journal of Ecology 94 pp. 1080-1091
  2. Phillips, 1977. Wild Flowers of Britain p. 106
  3. O'Mahony, 2009. Wildflowers of Cork City and County pp. 205-206
  4. Marín, 2012. PhytoKeys 14 pp.  1-14

1 comment:

  1. The sudden origin of a new species by hybridization and polyploidy always fascinated me.