Sex with a stranger: two Pyrola species at Disko

 

 
Sex with a stranger: Pyrola plants at Qeqertarsuaq caught in the act

By Thure P. Hauser, Ph.D., Associate Professor, Department of Agriculture and Ecology, Faculty of Life Sciences, University of Copenhagen
Dorthe Nygaard Christensen, Marietta Bohr

Two species of Pyrola (Danish: vintergrøn) grow in Greenland. One of the species, Pyrola grandiflora, grows in northern North America and most of Greenland. The other species, P. minor, has a more southern distribution including Europe, and has its northern distribution limit at Disko Island on the west coast of Greenland. Here the two species have been reported to reproduce, hybridize, with each other.

In a research project financed by the Carlsberg Foundation, we study the consequences of this hybridization: Do the hybrids reproduce with each other and the parental species?
If not, formation of hybrids may hinder, or slow down, the spread of one species into the range of the other.
If hybrids reproduce and form more advanced generations of hybrids, this may eventually move genes, and with them adaptations to the environment, from one species to the other, by a process called introgression. This may lead to a faster spread of one species into the range of the other.

Last summer (2009) we collected material for genetic analysis to test if hybrids have reproduced with each other or the parents. This seems not to be the case. This is consistent with our analyses of morphology: hybrids are distinct as would be expected if they were only first-generation hybrids.
Interestingly, hybrids are only produced when pollen from P. grandiflora fertilizes seeds on P. minor.

In the summer of 2010, we will focus more on why hybrids are not reproductively active, by testing how well pollen from hybrids germinate and grow in the stigmas and style of parental  plants and other hybrid plants (and vice versa), and whether hybrids in natural  habitats produce seeds.

Participants

The study is a collaboration between Marianne Philipp (project leader), Department of Biology, University of Copenhagen, Thure Hauser, Department of Agriculture and Ecology, University of Copenhagen, and Dr. Jim Provan, School of Biological Sciences, Queen’s University Belfast.

Three BSc students are, or have been, attached to the project.

Litterature

Böcher, T. W. (1961). “Studies in Pyrolaceae – Two interesting wintergreens from West Greenland.” Botanisk Tidsskrift 57: 28-37.

Stebbins, G. L. (1984). “Polyploidy  and the distribution of the arctic-alpine flora: new evidence and a new approach.” Botanica Helvetica 94(1-13).

Beatty GE, Philipp M, Provan J. 2010.  Unidirectional hybridization at a species’ range boundary: implications for habitat tracking. Diversity distrib. 16: 1-9.

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