| Abstrakt: |
ABSTRACTPhytophthoraspecies are widespread and diverse in forest ecosystems, but little is known about their ecology. We explore ecological attributes of the closely related clade 3 species that occur sympatrically in western North American forests. We address the population structure, pathology, and epidemiology of P. ilicis, P. nemorosa, P. pluvialis, P. pseudosyringae, and P. psychrophila. Phytophthoraspecies were isolated from plant tissues, rainwater falling through the forest canopy, streams, and soils in forests in western Oregon. Species identifications were based on morphology in culture with molecular confirmation using COX spacer and internal transcribed spacer (ITS) sequences. All five clade 3 Phytophthoraspecies are present in western Oregon forests, although P. ilicis(only 1 forest isolate) and P. psychrophila(only 12 isolates) are apparently rare. P. ilicisis known only from holly in horticultural situations and once from a naturalized seedling in an urban forest. The known distribution of P. nemorosain forest settings coincides with the ranges of its principle hosts, tanoak and myrtlewood, in Oregon and California. Although it is regularly identified from streams within the tanoak range, it has not been recovered from streams beyond that range. P. pluvialisis primarily associated with Douglas-fir canopies. It was identified from scattered locations throughout western Oregon in rain traps beneath Douglas-fir plantations and from diseased needles. P. pseudosyringaeis also isolated from tanoak and myrtlewood in southwest Oregon and California, but its distribution, in streams at least, extends throughout much of western Oregon. P. psychrophilain Oregon is known only from rain traps beneath tanoak trees. Little intraspecific variation was detected in the nuclear rDNA ITS of clade 3 species. Variation in the mitochondrial COX spacer region was more frequent, with 2 to 10 haplotypes identified in the clade 3 species, for which we had multiple isolates. |
