Résumé
Positive species-genetic diversity correlations (SGDCs) are often thought
to result from the parallel influence of neutral processes on genetic and
species diversity. Yet, confounding effects of non-neutral mechanisms have
not been explored. Here, we investigate the impact of non-neutral genetic
diversity on SGDCs in high Andean wetlands. We compare correlations
between plant species diversity (SD) and genetic diversity (GD) calculated
with and without loci potentially under selection (outlier loci). The
study system includes 2188 specimens from five species (three common
aquatic macroinvertebrate and two dominant plant species) that were
genotyped for 396 amplified fragment length polymorphism loci. We also
appraise the importance of neutral processes on SGDCs by investigating the
influence of habitat fragmentation features. Significant positive SGDCs
were detected for all five species (mean SGDC = 0.52 ± 0.05). While only a
few outlier loci were detected in each species, they resulted in
significant decreases in GD and in SGDCs. This supports the hypothesis
that neutral processes drive species-genetic diversity relationships in
high Andean wetlands. Unexpectedly, the effects on genetic diversity of
the habitat fragmentation characteristics in this study increased with the
presence of outlier loci in two species. Overall, our results reveal
pitfalls in using habitat features to infer processes driving SGDCs and
show that a few loci potentially under selection are enough to cause a
significant downward bias in SGDC. Investigating confounding effects of
outlier loci thus represents a useful approach to evidence the
contribution of neutral processes on species-genetic diversity
relationships.