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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 5 March 2013