DOI: 10.5061/dryad.1k6313f
title: Data from: Parasite resistance predicts fitness better than fecundity in a natural population of the freshwater snail Potamopyrgus antipodarum

description: The cost of males should give asexual females an advantage when in
 competition with sexual females. In addition, high-fecundity asexual
 genotypes should have an advantage over low-fecundity clones, leading to
 reduction in clonal diversity over time. To evaluate fitness components in
 a natural population, we measured the annual reproductive rate of
 individual sexual and asexual female Potamopyrgus antipodarum, a New
 Zealand freshwater snail, in field enclosures that excluded competitors
 and predators. We used allozyme genotyping to assign the asexual females
 to particular clonal genotypes. We found that the most fecund asexual
 clones had similar or higher fecundity as the top 10 % of sexual families,
 suggesting that fecundity selection, even without the cost of males, would
 lead to replacement of the sexual population by clones. Consequently, we
 expected that the clones with the highest fecundity would dominate the
 natural population. Counter to this prediction, we found that high annual
 reproductive rates did not correlate with the frequency of clones in the
 natural population. When we exposed the same clones to parasites in the
 laboratory, we found that resistance to infection was positively
 correlated with the frequency of clones in the population. The correlation
 between fecundity and parasite resistance was negative, suggesting a
 trade-off between these two traits. Our results thus suggest that parasite
 resistance is an important short-term predictor of the success of asexual
 P. antipodarum in this population.
description: background_sampleAllozyme genotypes at 9 loci and ploidy information for the 200 Potamopyrgus antipodarum snails from Lake Alexandrina, New Zealand, of the random sample collected in 2010 (“background sample”). Genotypes were obtained with cellulose acetate electrophoresis. Ploidy level was assigned based on asymmetric banding pattern in heterozygotes. Loci used for assigning ploidy level include: 6PGD, MPI, IDH2, PGM1 and PGM2 (ploidy assignment based on AAT1, AAT2, IDH1 and PEP-D was not reliable). Descriptions of column headings and abbreviations used: A: SNAIL - snail number. B: PLOIDY - ploidy level (0-homozygote, 2-diploid, 3-triploid, 4-tetraploid). Diploid snails are sexual, and polyploid snails are asexual; homozygotes were included in the sexual group. C: GENOTYPE_ID - The numbers above zero are unique clone numbers. Zeroes indicate genotypes for which unique clone number could not be assigned. Sexual snails are marked as "S". D-L: column names are allozyme loci names. Genotypes are coded with a single digit. Loci for which the banding pattern is unreliable for assigning ploidy level are left with 2 alleles for triploid heterozygotes.field_experimentFecundity and offspring size of Potamopyrgus antipodarum snails in the field experiment. Descriptions of column headings and abbreviations used: A: FAMILY_NUMBER - number of experimental enclosure (cage). B: GENOTYPE_ID - Asexual families were assigned unique clone numbers, "S" - sexual families, "NA" - unresolved genotypes. Allozyme genotypes were obtained from one or two (if available) snails per family. C: PLOIDY - 2- diploid, 3- triploid. D: LINEAGE_TYPE - 1- unresolved, 2- common clone, 3- rare clone, 4 -sexual. We assigned clone as common if the clone was replicated by at least three independent families. E: LENGTH_mm - snail length [mm].infection_experiments_2009_2011Infection status of individual Potamopyrgus antipodarum snails in the laboratory infection experiments of 2009 and 2011. Descriptions of column headings and abbreviations used: A: SNAIL - individual snail number. B: DATASET - "I2009"- infection experiment of 2009, "I2011"- infection experiment of 2011. C: YEAR - 2009, 2011. D: TREATMENT: "alex" - parasite source from Lake Alexandrina, "control" - control for parasite exposure. E: HABITAT: Lake Alexandrina habitat zone from which the snails were sampled. F: REP: Replicate number. In 2009 the experimental snails were exposed in 2 trays, and control snails in 2 trays. In 2011 the experimental snails were exposed in 6 trays and control snails in 2 trays; the control snails were combined into one tray before terminating the experiment. G: LENGTH: Snail length [mm]. H: SEX: Snail sex: "F"- female, "M"- male. I: MIC: Microphallus sp. infection: "1"- present, "0"- absent. J: PLOIDY - 2- diploid, 3- triploid. K: GENOTYPE_ID - The numbers above zero are unique clone numbers. Zeroes indicate genotypes for which unique clone number could not be assigned. Sexual snails are marked as "S".