Asexuality and polyploidy in <i>Daphnia</i> from the tropical Andes

Abstract

We assessed genetic variation at microsatellite loci within and among populations of the planktonic crustacean Daphnia pulex in 12 Bolivian Andean lakes, located above 4,000 m above sea level. Genetic analyses show that all populations consisted of obligately asexual lineages, a fact that was confirmed by observations from laboratory cultures. Moreover, microsatellite phenotypes indicate that these tropical lineages are polyploid. Levels of genetic diversity were comparable to those found in polyploid Daphnia from arctic regions, indicating a local origin rather than an accidental colonization from arctic regions. This is the first record of polyploid cladocerans in a tropical region. We suggest that their origination and abundance have probably been facilitated by the extreme environmental conditions in Andean lakes. Our analysis of multilocus genotype frequencies in relation to variation in environmental conditions indicates lineage sorting along a food availability and fish predation gradient.