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Adaptation of Rotifers to Seasonal Variation
Author(s) -
King Charles E.
Publication year - 1972
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1934226
Subject(s) - biology , population , adaptation (eye) , ecology , abiotic component , local adaptation , competition (biology) , demography , neuroscience , sociology
Most lakes display extensive seasonal variation in both their biotic and abiotic components. The question posed in this paper is how do rotifers adapt to this temporal heterogeneity?. Three alternate models of population structure for temporal adaptation are advanced and considered. If the physiological state of population varies continuously with its environment, the relative fitness of a population will be constant. To test this hypothesis, rotifers (Euchlanis dilatata) were periodically collected from a nature, cloned, allowed to adapt to the laboratory environment for 10 generations, and then used in experiments to determine the intrinsic rate of population growth, r. The r values of clones collected at different times indicated that physiological adaptation alone is not the major factor involved in adaptation to seasonal variation. Moreover, the pattern of variation in r revealed genetic differences among clones collected at different times. An alternate explanation, genetic discontinuity through time, is presented in two forms. Both models assume that different genotypes are maximally adapted to different parts of the environmental spectrum. The first model further assumes that adults of all genotypes are present throughout the spring and summer, but that the frequencies of the genotypes vary directly with the environmental variation. This model is the most likely statement of rotifer population structure if there is considerable gene flow throughout the population and if interclonal competition is not important. If either of these conditions does not hold,the population is expected to be subdivided into a number of genetically discrete units, each unit occupying a different temporal part of the environmental mosaic. An insufficient number of clones was tested to distinguish between the two models of temporal genetic polymorphism. However, the data that were obtained demonstrate that the large genetic component is necessary to explain the adaptation of E. dilatata to seasonal variation.