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Karl Duffy

Karl Duffy

PhD: Reproductive biology and conservation of rare orchid species in Ireland (2004-2008, NPWS funding)

PhD Thesis Abstract:

This thesis investigates the factors that affect the conservation and reproductive biology of rare Irish orchids. Research focused on various aspects of the ecology of six species that occur throughout Ireland. Four endangered, red-listed species were examined: Cephalanthera longifolia, Hammarbya paludosa, Pseudorchis albida, and Spiranthes romanzoffiana. In addition, one rare species Neotinea maculata and one relatively abundant species Spiranthes spiralis were also examined. I employed probabilistic models to infer threat of four species (C. longifolia, H. paludosa, N. maculata, and P. albida). These models have various assumptions regarding the sighting process, however little is known about how sighting records were generated, therefore it is imperative to use different models. Using five models, a optimal linear estimate to infer extinction time, and a rarefaction analysis, I found that there have been declines in the three endangered species (C. longifolia, H. paludosa, and P. albida). However the models erroneously inferred that N. maculata was threatened. Populations of all four species flowered in low numbers at all populations examined. To test for the effects of rarity on pollination of an endangered orchid, I examined the pollination of S. romanzoffiana. I found that bees visited S. romanzoffiana and observations made in replicate patches of varying density showed that S. romanzoffiana competes for pollinator attention at high densities. In addition, I found that S. romanzoffiana offers a nectar reward that varies over the flowering season, with more nectar produced at the middle of the season. Morphologically similar, nectar rewarding co-flowering species may also facilitate visitation to inflorescences of S. romanzoffiana. To compare the differences between the endangered S. romanzoffiana and the more common S. spiralis, I measured different components of pollination success (pollen export, pollen import, fruit and seed set) at different spatial scales (population size and varying densities within populations), as well as interactions with co-flowering species. I found that population size only affected pollinator visitation in very small populations of S. romanzoffiana. However, the proportion of pollen export and import did not vary with population size in either species. The density of coflowering species had a positive effect on pollen export in S. romanzoffiana, while S. romanzoffiana density and visitation rate positively affected pollen import. Although coflowering species had no effect on S. spiralis pollination, its own intraspecific density increased fruit set and decreased pollen loss from patches. In addition, I found that visitation rate to S. spiralis increased its pollen export. Both species are self-compatible but rely on pollinators for fruit set. Fruit set was found to be abundant in S. spiralis, however, despite evidence for pollination, fruit does not mature in S. romanzoffiana, yet some seeds are present in the immature fruits. To examine the effects of rarity across a species range, I compared the ecology and population genetics of N. maculata at the centre (Italy) and edge (Ireland) of its European range. For this I used vegetation analysis, breeding system experiments, and a DNA fingerprinting technique, AFLP. I found that N. maculata occurs in a wide variety of habitats and is highly self-compatible in both Ireland and Italy, yet has high levels of genetic polymorphism, according to AFLP markers. It also has high levels of population genetic differentiation, with Irish populations significantly different from Italy populations. I examined the effects of rarity on the population genetic structure of two endangered Irish orchid species: C. longifolia and P. albida. Three plastid microsatellite markers showed low genetic diversity in Irish populations of C. longifolia. However one unique cytotype was present in the smallest population. I used four microsatellite marker and AFLP markers to examine P. albida. No genetic variation was found at the microsatellite loci, however the AFLP markers showed P. albida had high levels of polymorphism and significant population genetic differentiation, indicating population isolation through distance. The findings are discussed in the broader context of conservation biology and the effects of rarity on reproductive biology, with reference to effective population management to prevent the extinction of these species in Ireland.

Contact details

Current position: postdoc with Prof Steve Johnson, University of KwaZulu Natal, South Africa (

photo of neotinia maculata

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Last updated 4 April 2013