Changes in the life-history strategy of Gammarus lacustris (Crustacea, Amphipoda) in water bodies with different environmental conditions
AbstractLife history features, such as duration of juvenile period, size, and fecundity of individuals, were studied in some Gammarus lacustris populations from water bodies with different temperature regimes. There are two opposite trends in variations of life-history parameters in populations of G.lacustris. namely "gigantism" and "dwarfism". The first trend takes place mainly in warm plain and plateau lakes. The second, in other types of water- bodies such as cold alpine lakes, cold springs, and warm geothermal streams. The "gigantic' populations are characterized by a large size of adult females, high fecundity, and a short juvenile period. The "dwarfish" ones are distinguished by small sizes, low fecundity, and a prolonged juvenile period. Such changes in life-history parameters do not correspond with the classical concept of r/K-selectlon. The decrease of the juvenile periods (r selection) in the "gigantic"- populations is accompanied by an increase of the adult size (K-selection). On the contrary, an increase of the juvenile period (K-seleciion) in the "dwarf" populations is accompanied by diminished adult size (r-selection). The life-history characteristics of G.lacustris populations from water bodies with rather constant temperatures (cold spring, geothermal stream) are in rather good agreement with the so called "A-selection" which occurs in some severe but predictable habitats.
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