VARIATION OF MICROSATELLITE SIZE HOMOPLASY ACROSS ELECTROMORPHS, LOCI, AND POPULATIONS IN 3 INVERTEBRATE SPECIES

Size homoplasy was analyzed at microsatellite loci by sequencing elect romorphs, that is, variants of the same size (base pairs). This study was conducted using five interrupted and/or compound loci in three inv ertebrate species, the honey bee Apis mellifera, the bumble bee Bombus terrestris, and the freshwater snail Bulinus truncatus. The 15 electr omorphs sequenced turned out to hide 31 alleles (i.e., variants identi cal in sequence). Variation in the amount of size homoplasy was detect ed among electromorphs and loci. From one to seven alleles were detect ed per electromorph, and one locus did not show any size homoplasy in both bee species. The amount of size homoplasy was related to the sequ encing effort, since the number of alleles was correlated with the num ber of copies of electromorphs sequenced, but also with the molecular structure of the core sequence at each locus. Size homoplasy within po pulations was detected only three times, meaning that size homoplasy w as detected mostly among populations. We analyzed population structure , estimating F-st and a genetic distance, based on either electromorph s or alleles. Whereas little difference was found in A. mellifera, unc overing size homoplasy led to a more marked population structure in B. terrestris and B, truncatus. We also showed in A. mellifera that the detection of size homoplasy may alter phylogenetic reconstructions.