Ecological differentiation between coexisting sexual and asexual strains of Daphnia pulex

摘要: 1. The widespread occurrence of sexual reproduction indicates that the benefits sex can overcome its costs relative to asexual reproduction. Many closely related and taxa have different geographic distributions suggesting their fitness may depend on environment. However, support for such ecological differentiation is mainly based correlative evidence, with experimental being scarce, especially from wild. 2. We studied between (obligate parthenogenetic) (cyclical Daphnia pulex in Southern Finland, where two forms ('reproduction types') coexist regionally a metapopulation. found differences several environmental factors ponds inhabited by populations (pH, calcium, oxygen, conductivity absorbance). 3. A reciprocal competition experiment carried out directly natural confirmed sexuals asexuals were ecologically differentiated; was pH calcium titres ponds. 4. Our study provides clear evidence coexistence mediated differentiation. In addition, results our suggest each types has larger fundamental niche (absence competition) than realized (presence competition). Thus, temporarily creating competition-free space, metapopulation turnover allow occur wider range habitats under more stable population dynamics, thus further contribute stabilize regional coexistence.