Large-scale occurrence patterns of red-listed lichens and fungi on old oaks are influenced both by current and historical habitat density |
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Authors: | Thomas Ranius Per Eliasson Per Johansson |
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Institution: | 1. Department of Ecology, Swedish University of Agricultural Sciences, P.O. Box?7044, 750 07, Uppsala, Sweden 2. Malm? University, 205 06, Malm?, Sweden 3. Swedish Environmental Protection Agency, 106 48, Stockholm, Sweden
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Abstract: | Current occurrence patterns of species associated with ancient trees may reflect higher historical habitat densities, because
the dynamics of the habitat and the colonisation-extinction processes for many inhabiting species are expected to be slow.
We tested this hypothesis in southeast Sweden by analysing species occurrence per parish for twelve redlisted lichen species
and nine redlisted fungus species in relation with current density of big oaks, the density of oaks in the 1830s and connectivity
with parishes with the species present. For most species, the occurrence was positively related with current density of habitat
(for 18 species out of 21) and parish area (for 16 species). Historical habitat density was positively related with occurrence
for 11 species, while connectivity with current occurrences in the surroundings was positive for the occurrence of 12 species
and negative for the occurrence of two. For lichen species the connectivity measure that best explained the variation was
at a larger spatial scale as compared to fungus species. Even if the density of old oaks remains in the future, inhabiting
species will most likely decline because their distribution patterns are not in equilibrium with the current habitat density.
Therefore, to allow long-term persistence of inhabiting species the number of old oaks should be increased. Areas where such
an increase is most urgent could be identified based on species occurrence data and current habitat density, but because species
data will always be incomplete data on the historical habitat distribution is valuable. |
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Keywords: | Connectivity Epiphytic lichens Extinction debt Habitat history Habitat loss Quercus robur Saproxylic fungi |
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