Wild mallards have more "goose-like" bills than their ancestors: a case of anthropogenic influence?

PLoS One. 2014 Dec 16;9(12):e115143. doi: 10.1371/journal.pone.0115143. eCollection 2014.

Abstract

Wild populations of the world's most common dabbling duck, the mallard (Anas platyrhynchos), run the risk of genetic introgression by farmed conspecifics released for hunting purposes. We tested whether bill morphology of free-living birds has changed since large-scale releases of farmed mallards started. Three groups of mallards from Sweden, Norway and Finland were compared: historical wild (before large-scale releases started), present-day wild, and present-day farmed. Higher density of bill lamellae was observed in historical wild mallards (only males). Farmed mallards had wider bills than present-day and historical wild ones. Present-day wild and farmed mallards also had higher and shorter bills than historical wild mallards. Present-day mallards thus tend to have more "goose-like" bills (wider, higher, and shorter) than their ancestors. Our study suggests that surviving released mallards affect morphological traits in wild population by introgression. We discuss how such anthropogenic impact may lead to a maladapted and genetically compromised wild mallard population. Our study system has bearing on other taxa where large-scale releases of conspecifics with 'alien genes' may cause a cryptic invasive process that nevertheless has fitness consequences for individual birds.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Beak / anatomy & histology*
  • Body Weights and Measures
  • Breeding
  • Ducks / anatomy & histology*
  • Female
  • Finland
  • Male
  • Norway
  • Sweden

Grants and funding

Funding provided by V-205-09 The Swedish Environmental Protection Agency, http://www.naturvardsverket.se/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.