Speciation is intensive in most favorable areas (I, II, III, for instance in tropical mountains) but size of areals of species is limited, presumably by ecological conditions and competition. Some more enterprising species penetrate into less favorable zones and, meeting less competition, expand over larger areas. Single most enterprising species, capable to endure unfavorable condditions, or entering land free of competitors, spread over very large areas of continental dimensions. The example of the latter may be Euro-Siberian areals of Evarcha arcuata, E. falcata and E. latebunda.

Source: Proszynski J. 1986a. Remarques sur la composition de la faune europeenne, sa repartition et son origine basees sur les etudes des Salticidae. Mem. Soc. r. belge Ent., Bruxelles, 33: 165-170, 4 tt. With Author's and Editor's permission.