Occurrence pattern of the parasitic fungus Rhytisma polare (Ascomycota) on the polar willow (Salix polaris) under limited water conditions in a high-Arctic semi-desert
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The parasitic fungus Rhytisma polare is a common parasite on leaves of the polar willow (Salix polaris) in the high-Arctic polar semi-desert of Spitsbergen, Norway. Because Rhytisma spp. generally requires saturation with free water to develop ascospores, it is unclear how R. polare has ecologically adapted to the Arctic desert, where such water is very limited. In this study, the response of R. polare to different water conditions on Spitsbergen was investigated during the summer months of June–August in 2012. Field and laboratory experiments demonstrated that free water availability from rainfall or snowmelt is essential to facilitate ascostromal maturation and ascospore dispersal in R. polare. The field experiments also revealed that the dispersal of ascospores produced on fallen leaves did not extend beyond a few meters. These results suggest that the free water requirement combined with the short spore-dispersal distance constrains the local occurrence of R. polare in the Arctic desert to locations where free water from rainfall and snowmelt is present.
KeywordsHigh-Arctic Free water Plant pathogen Ascostromal maturation Spore dispersal
We are grateful to Dr. Naoyuki Matsumoto for critical reviewing the manuscript. This work was supported by a Grant from SOKENDAI (The Graduate University for Advanced Studies), the National Institute of Polar Research (Research Project KP‒11), and the Green Network of Excellence (GRENE) Program to SM, SI, and MU and by a JSPS Grant-in-aid for scientific research (no. 15K00626) to MT. This work was also supported by the Arctic Challenge for Sustainability Project (ArCS) Grant provided by the Ministry of Education, Culture, Sports, Science, and Technology, Japan. We thank Barbara Goodson, PhD, from Edanz Group (www.edanzediting.com/ac) for editing an earlier version of this manuscript.
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Conflict of interest
The authors declare that they have no conflict of interest.
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