Two parthenogenetic populations of <Emphasis Type="Italic">Chara canescens</Emphasis> differ in their capacity to acclimate to irradiance and salinity |
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Authors: | Ralf Schaible Antje Gerloff-Elias Fernando Colchero Hendrik Schubert |
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Institution: | (1) Institute of Bio Sciences, Aquatic Ecology, University of Rostock, Albert-Einstein Str. 3, 18051 Rostock, Germany;(2) Max Planck Institute for Demographic Research, Konrad Zuse Str. 1, 18057 Rostock, Germany |
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Abstract: | The parthenogens of Chara canescens (Charophyceae) occupy broader geographical and ecological ranges than their sexual counterparts. Two possible hypotheses
explain the ubiquity of parthenogens: the occurrence of one or several parthenogens with wide niches, or of many parthenogens
that are restricted to narrow ecological niches. For the purposes of this study, C. canescens individuals from two neighbouring populations of the Baltic Sea (Bodstedter Bodden = BB; Salzhaff = SH), which differed significantly
in water transparency and salinity, were investigated for significant differences in physiological capacity. Individuals of
both habitats acclimated quickly to daily changes in irradiances in the field, but the photosynthetic efficiency of PS II
showed a significant decrease with increasing daily irradiance in the habitat BB, which has lower levels of salinity and water
transparency. In addition to the field study, individuals were reared under different levels of environmental factors in the
laboratory: four irradiances (70–600 μmol m−2 s−1) and five salinity levels (0–24 psu). The individuals of both habitats grew almost equally well at intermediate salinity
levels. Growth under the artificial light supply was highest at levels corresponding to the in situ conditions for each population.
Total chlorophyll was highest at intermediate salinities (BB), or hardly changed with salinity (SH). The physiological capacity
for individuals from SH clearly depends upon changing growth irradiance, whereas the capacity for individuals from BB was
relatively independent of salinity and irradiance. These findings indicate that both parthenogenetic C. canescens populations are locally adapted to light. However, to test adaptive potential of the parthenogens, more than two populations
should be tested in future. |
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