Evolution and maintenance of pollen-colour dimorphisms in Nigella degenii: habitat-correlated variation and morph-by-environment interactions

Authors: Jorgensen, Tove Hedegaard; Andersson, Stefan

Source: New Phytologist, Volume 168, Number 2, November 2005 , pp. 487-498(12)

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Abstract:

Summary

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Dimorphism in pollen colour is rare among flowering plants, but occurs in two geographically and morphologically distinct subspecies of Nigella degenii (Ranunculaceae). We evaluated the role of genotype-by-environment interactions in the maintenance of two pollen morphs within each of these subspecies.

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Morph frequencies in a number of populations were related to current habitat conditions, and an extensive common-garden experiment involving both optimal and stressful conditions (drought and nutrient deficiency) was carried out.

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The putatively derived (dark) pollen morph of N. degenii ssp. barbro has a higher frequency on slopes facing north or east than on slopes facing south or west. Plants of the dark morph also have a higher mortality under drought stress or nutrient deficiency. Data available for N. degenii ssp. jenny provide little evidence for habitat-correlated variation in morph frequency or morph-specific differences in fitness under optimal and stressful growth conditions.

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Our results suggest that morph-by-environment interactions in mortality could contribute to the maintenance of pollen-colour dimorphisms in N. degenii ssp. barbro.

New Phytologist (2005) doi: 10.1111/j.1469-8137.2005.01525.x

©New Phytologist (2005)

Keywords: Cyclades; genetic correlation; genotype–environment interaction; Nigella degenii; pleiotropy; pollen colour; Ranunculaceae

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1469-8137.2005.01525.x

Publication date: 2005-11-01