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IMPACT OF WATER CALCIUM ON THE PHENOTYPIC DIVERSITY OF ALPINE POPULATIONS OF GAMMARUS FOSSARUM
Author(s) -
Meyran Jean-Claude
Publication year - 1997
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/0012-9658(1997)078[1579:iowcot]2.0.co;2
Subject(s) - biology , intraspecific competition , calcium , interspecific competition , ecology , calcite , zoology , chemistry , organic chemistry , paleontology
As an example of the relative impact of a specific ambient parameter on intraspecific phenotypic differentiation, the contribution of environmental sources of calcium on the geographic variation between alpine populations of the freshwater crustacean Gammarus fossarum was investigated through a comparative analysis of six different populations in the torrents of the Grenoble region of France. Major differences in water calcium levels were observed in correlation with lithological differences (average 13.6 mg/L in the crystalline massif of the Belledonne and 83.4 mg/L in the limestone areas of the Chartreuse and Vercors). The comparative analysis of the populations was performed through field and laboratory experimentation at morphometrical and ecophysiological levels. Uniform samples of male adult specimens from six different sites (two sites in the Belledonne, two sites in the Chartreuse, and two sites in the Vercors) were compared using three easily measurable parameters: maximum dry mass, duration of the molt cycle, and calcium balance during the molt cycle. Animals from waters that flow over limestone show a larger maximum size and a longer molt cycle than those from waters that flow over crystalline rocks. Spectrophotometrical analysis of their calcium balance during the molt cycle reveals that, whereas all animals are equally calcified during the intermolt, the decalcification during the premolt and the recalcification during the postmolt are more rapid in animals from limestone areas than in those from crystalline sites. Translocation experiments in both natural and artificially calcium‐enriched waters confirm these differences. A significant increase in the duration of the molt cycle was observed in animals translocated to water of lower calcium concentration and vice versa, whereas no significant difference was observed between controls and animals translocated into water of comparable calcium concentration. Current results, supported by such a new synthetic experimental approach, indicate that variations in water calcium levels may generate important ecophysiological differentiation between populations, which may suggest a possible influence of environmental calcium on the geographic distribution of Gammarus fossarum.