Restoration demography: a 10-year demographic comparison between introduced and natural populations of endemic Centaurea corymbosa (Asteraceae)

Published source details Colas B., Kirchner F., Riba M., Olivieri I., Mignot A., Imbert E., Beltrame C., Carbonell D., & #233;ville H. (2008) Restoration demography: a 10-year demographic comparison between introduced and natural populations of endemic Centaurea corymbosa (Asteraceae). Journal of Applied Ecology, 45, 1468-1476.
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Summary

Centaurea corymbosa is a self-incompatible (i.e. incapable of self-fertilization), cliff-dwelling plant endemic to a 3 kmÂ² area of Massif de la Clape, a small limestone massif (15,000 ha) sitiuated in southeast France. Many nearby unoccupied and apparently suitable cliffs are present, but the species very restricted area of occupancy appears limited by low colonization ability. It occurs in six natural populations ranging from about 18 to 200 flowering plants. An introduction was undertaken in 1994 on two nearby unoccupied cliffs and the demography over 10 years of all populations (these and the six natural ones) followed.

Centaurea introduction: Two cliff-top sites (each about 2 m²) which appeared similar to habitat occupied by natural populations (i.e. medium-sized rock clefts with little soil or vegetation) were selected for seed introduction. In November 1994, seed from three natural populations was placed into rock clefts in both introduction areas; in October 1995, additional seed (from four natural populations) was sown into one of the introduction areas. A total of 50 seeds were added to each introduction site.

Monitoring: Seedling emergence, survival and leaf-rosette diameter size were recorded every 3 months (September, December, March and June) at the introduction sites and within permanent quadrats in the six natural populations, over 10 years (to 2004).

Over the 10 years, the proportion of individuals that survived to flowering was slightly higher in the introduced (8.2%) than in the natural populations (6.7%). This is attributed to better habitat conditions at the cliff scale and/or to the better microsites selected for sowing (i.e. seed placed in suitable-looking rock clefts) compared to those reached by naturally dispersed seed.

However, the introduced populations had lower fecundity than natural ones, probably due to the introduction using too few seeds collected from too few sites within natural populations, resulting in reduced cross-pollination opportunity; higher survival compensated for this lower fecundity.

The authors consider that establishment of new C.corymbosa populations seems straightforward provided that the seed sown is derived from several sources at high density and in several consecutive years, which should increase ‘mate’ availability for this self-incompatible species.

Note: The compilation and addition of this summary was funded by the Journal of Applied Ecology (BES). If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://www3.interscience.wiley.com/cgi-bin/fulltext/121391862/PDFSTART