plasticity and d.re polymorphous, i.e., capable of forming various 

 intraspeci fie (hereditary and nonhereditary) biologic groups, have great 

 evolutionary stability. From the standpoint of the theory of ecologic 

 stability, the eurybiotic species are evol utionarily more stable than 

 the stenobiotic species (Jackson, 1974; Eldredge, 1974). 



The following peculiarities of the intertidal zone can be added to 

 those already discussed. It is characteristic for the intertidal zone 

 that the types of communities (formations) are limited, finding homologs 

 and analogs on all coasts of ttie world ocean. Possible exceptions 

 include the cryocenoses of the Arctic and Antarctic and the mangrove 

 areas of the tropical zone (Golikov, 1975a). These littoral communities 

 consist of a relatively small number of eurybiotic, polymorphous, 

 ecologically plastic but evol utionarily stable species. 



These peculiarities of the intertidal zone have been reflected in 

 the figurative words of L. A. Zenkevitch: "The intertidal zones of the 

 various coastlines of the earth represent a play, with the same parts, 

 which are played in different places by different actors." 



As to degree of similarity (and in many cases of kinship), littoral 

 communities can be divided into four groups. 



1. Identical communities. Groups of organisms occupying similar 

 biotopes within a single biogeographic province or area, less frequently 

 a single climatic zone, the dominant species of which Are the same. We 

 must not forget that in terms of its specific composition, one and the 

 same community is far from identical, not only in its remote regions, 

 but also frequently in neighboring regions. In extreme cases, the 

 composition of a single community in different biotopes of a single 

 region may have almost no common species except for the dominant species 

 itself, plus a few banal species common to the entire intertidal zone. 

 For example, on the northwest coast of Iturup Island, a community of 

 Cystoseira crassipes algae is found, however, of 17 species of 

 macrophytes which make up the community, only two are common to the 

 cliffs and the rocks, including the band- forming species, and of 45 

 macrofaunal species, only four are found on both the cliffs and the 

 rocks (Kussakin et al., 1974). 



2. Parallel or vicariant communities. Groups of organisms 

 occupying similar biotopes within different zones, biogeographic areas 

 or provinces, with closely related dominant species, usually of one 

 genus, less frequently of one family or superfamily (Thorson, 1957). 

 These vicariant communities frequently dominate throughout an entire 

 biogeographic dtveA. As an example, for the boreal zone we can cite the 

 communities of Chthamalus stellatus , Pelvetia canal iculata , Fucus 



di stichus , Li ttori na obtusata , Testudinal ia testudinal is , Gammarus 

 oceanicus + Li ttorina saxatil il s , Halosaccion ramentaceum , Rhodymenia 

 palmata , ~Alaria esculenta + Laminaria digitata on the rocky European 

 coasts and the corresponding communities of Chthamalus dalli , Pelvetia 

 wrighti i , Fucus evanescens , Littorina kurila , Collisella cassis , 

 Anisogammarus locustoides + Littorina sitchana , Halosacc ion glandiforme , 

 Rhodymenia stenogona , Alaria angusta + Laminaria bongardiana in the 

 intertidal zone of the fareastern coast of the USSR. 



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