The Microflora 261 



large groups such as families or orders commonly dominant in other 

 Biomes. For example, the soils show a great preponderance of sterile 

 forms combined with the absence or low incidence of common soil fungi 

 such as Aspergillus, Fusarium, Alternaria and Botrytis in the Fungi Im- 

 perfect!, and Rhizopus in the Zygomycetes. On the other hand Clado- 

 sporium herbarum, a dominant phyllosphere fungus of the coastal tun- 

 dra at Barrow, is common in other Biomes and is a circumpolar fungus 

 as well (Flanagan and Scarborough 1974). The preponderance of sterile 

 forms agrees well with data from Macquarie Island (Bunt 1965), Mac- 

 kenzie Valley (Ivarsen 1965), British Moorlands (Latter et al. 1967), 

 northern Sweden (Hayes and Rheinberg 1975) and Truelove Lowland 

 (Widden 1977), The low incidence of species of Penicillium, Fusarium 

 and Aspergillus relative to the mycoflorae of temperate regions also has 

 been reported for the Canadian High Arctic (Widden et al. 1972) and 

 northern Sweden (Hayes and Rheinberg 1975) in drier years. Data from 

 the same sites in relatively wet years suggest that Hudson's (1968) asser- 

 tion that Penicillia are rare and Trichoderma typically absent from tun- 

 dra soil mycoflorae is not universally applicable. 



Among the Zygomycetes, members of the Mucorales that are nor- 

 mally dominant in temperate soils (Pugh 1974) are poorly represented at 

 Barrow and in other arctic areas (Widden et al. 1972). The species that do 

 occur appear to have adapted to cold (see Chapter 9) and are often en- 

 countered in the early spring or under near-winter conditions. The cold 

 tolerance of some Mucorales has also been observed and reported by 

 Latter and Heal (1971) for the Antarctic. 



The most important segment of the aquatic fungi are the algal para- 

 sites, and relatively few free-living species have been isolated from the 

 soils and waters. Nearly 85% of the algae examined contained at least 

 one fungal parasite, with Lagenidium oedogonii the most abundant par- 

 asitic form (Seymour, pers. comm.). Populations of Chytridiales and 

 Saprolegniales are, however, common in polygon troughs, basins of low- 

 centered polygons and slough areas. Members of the genera Achlya, 

 Apodachlya, Saprolegnia and Pythium are the most commonly occur- 

 ring water molds; Nowakoskiella elegans and Rhizophylctis hyalina are 

 the most frequently encountered chytrid species. Allomyces arbuscula 

 has been isolated at Barrow. 



Yeasts, including Endomycetales and some sterile forms (Fungi Im- 

 perfecti), are relatively abundant (10" to 10' gdw"' soil). Only three yeast 

 isolates have been identified, each as Cryptococcus laurentii var. magnus 

 (Shadomy, pers. comm.). Populations tend to be low in polygon troughs 

 and basins of low-centered polygons but in wet meadows and rims of low- 

 centered polygons, irregular, rapid increases and declines in populations 

 have been observed. Similar observations of fluctuating yeast abundance 

 have been made on Devon Island in the Canadian Arctic (Widden et al. 

 1972). 



