CLONAL-DIVERSITY PATTERNS AND BREEDING-SYSTEM VARIATION IN DAPHNIA PULEX, AN ASEXUAL-SEXUAL COMPLEX

Area of Science:

• Evolutionary Biology
• Genetics
• Ecology

Background:

• Daphnia pulex exhibits both cyclic and obligate parthenogenesis.
• The transition to obligate parthenogenesis is linked to meiosis suppression.
• Understanding breeding systems and clonal diversity is crucial for Daphnia pulex.

Purpose of the Study:

• Investigate breeding-system distribution and clonal diversity in Daphnia pulex populations.
• Analyze genotypic characteristics across the Great Lakes watershed.
• Provide a quantitative method for assessing clonal diversity.

Main Methods:

• Genotypic analysis of 10 Daphnia pulex populations from 22 Great Lakes sites.
• Electrophoretic surveys to identify clones.
• Combinatorial analysis to assess clone discovery rates relative to sample size and genetic intensity.

Main Results:

• Cyclic parthenogenesis was uncommon and restricted to southern sites.
• Most populations exhibited obligate parthenogenesis.
• An average of three clones per pond and 145 unique clones were identified watershed-wide.
• Regional clonal diversity was underestimated.

Conclusions:

• Obligate parthenogenesis is the dominant reproductive mode in Great Lakes Daphnia pulex.
• Electrophoresis and combinatorial analysis offer quantitative insights into clonal diversity.
• The study highlights the need for robust methods to assess genetic diversity in asexual populations.