title: Population genetic structure and hybridization patterns in the cryptic sister species Chironomus riparius and Chironomus piger across differentially polluted freshwater systems.
abstract: Chironomids are an integral and functionally important part of many freshwater ecosystems. Yet, to date, there is limited understanding of their microevolutionary processes under chemically polluted natural environments. In this study, we investigated the genetic variation within populations of the ecotoxicological model species Chironomus riparius and its cryptic sister species Chironomus piger at 18 metal-contaminated and reference sites in northwestern Portugal. Microsatellite analysis was conducted on 909 samples to answer if metal contamination affects genetic variation in natural chironomid populations as previously suggested from controlled laboratory experiments. Similarly high levels of genetic diversity and significant but weak genetic substructuring were found across all sites and temporal replicates, with no effects of metal contamination on the genetic variation or species' abundance, although C. piger tended to be less frequent at highly contaminated sites. Our results indicate that high levels of gene flow and population dynamic processes may overlay potential pollutant effects. At least for our study species, we conclude that the "genetic erosion hypothesis", which suggests that chemical pollution will reduce genome-wide genetic variability in affected populations, does not hold under natural conditions. Interestingly, our study provides evidence of successful hybridization between the two sister species under natural conditions.
authors.affiliation: Department of Biology & CESAM, Universidade de Aveiro, 3810-193 Aveiro, Portugal; Conservation Genetics Group, Senckenberg Research Institute and Natural History Museum Frankfurt, Clamecystrasse 12, 63571 Gelnhausen, Germany. Electronic address: joaoampedrosa@gmail.com.
authors.forename: João A M
authors.initials: JAM
authors.lastname: Pedrosa
authors.affiliation: Conservation Genetics Group, Senckenberg Research Institute and Natural History Museum Frankfurt, Clamecystrasse 12, 63571 Gelnhausen, Germany.
authors.forename: Berardino
authors.initials: B
authors.lastname: Cocchiararo
authors.affiliation: MARE - Marine and Environmental Sciences Centre, Faculty of Sciences and Technology, University of Coimbra, 3004-517 Coimbra, Portugal.
authors.forename: Tiago
authors.initials: T
authors.lastname: Verdelhos
authors.affiliation: Department of Biology & CESAM, Universidade de Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Amadeu M V M
authors.initials: AMVM
authors.lastname: Soares
authors.affiliation: Department of Biology & CESAM, Universidade de Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: João L T
authors.initials: JLT
authors.lastname: Pestana
authors.affiliation: Conservation Genetics Group, Senckenberg Research Institute and Natural History Museum Frankfurt, Clamecystrasse 12, 63571 Gelnhausen, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Nowak
mesh_terms: D000818:Animals; D002683:Chironomidae / Q000187:drug effects* / Q000235:genetics; D016000:Cluster Analysis; D005618:Fresh Water / Q000737:chemistry*; D014644:Genetic Variation / Q000187:drug effects*; D005828:Genetics, Population; D055106:Genome-Wide Association Study; D006824:Hybridization, Genetic; D008670:Metals / Q000032:analysis / Q000633:toxicity*; D011174:Portugal; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D008670:Metals; D014874:Water Pollutants, Chemical
keywords: Genetic diversity; Genetic erosion; Interspecific hybridization; Metal contamination; Microsatellites