title: Beak and skull shapes of human commensal and non-commensal house sparrows Passer domesticus.
abstract: BACKGROUND
  The granivorous house sparrow Passer domesticus is thought to have developed its commensal relationship with humans with the rise of agriculture in the Middle East some 10,000 years ago, and to have expanded with the spread of agriculture in Eurasia during the last few thousand years. One subspecies, P. d. bactrianus, residing in Central Asia, has apparently maintained the ancestral ecology, however. This subspecies is not associated with human settlements; it is migratory and lives in natural grass- and wetland habitats feeding on wild grass seeds. It is well documented that the agricultural revolution was associated with an increase in grain size and changes in seed structure in cultivated cereals, the preferred food source of commensal house sparrow. Accordingly, we hypothesize that correlated changes may have occurred in beak and skull morphology as adaptive responses to the change in diet. Here, we test this hypothesis by comparing the skull shapes of 101 house sparrows from Iran, belonging to five different subspecies, including the non-commensal P. d. bactrianus, using geometric morphometrics.
  
  
  RESULTS
  The various commensal house sparrow subspecies share subtle but consistent skeletal features that differ significantly from those of the non-commensal P. d. bactrianus. Although there is a marked overall size allometry in the data set, the shape difference between the ecologically differentiated sparrows cannot be explained by differences in size alone. Relative to the size allometry commensal house sparrows exhibit a skull shape consistent with accelerated development (heterochrony), resulting in a more robust facial cranium and a larger, more pointed beak.
  
  
  CONCLUSIONS
  The difference in skull shape and robustness of the beak between commensal and non-commensal house sparrows is consistent with adaptations to process the larger and rachis encapsulated seeds of domesticated cereals among human associated populations.
authors.affiliation: Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biological Sciences, University of Oslo, Blindern, P, O, Box 1066, Oslo N-0316, Norway. g.p.satre@ibv.uio.no.
authors.forename: Sepand
authors.initials: S
authors.lastname: Riyahi
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Hammer
authors.forename: Tayebeh
authors.initials: T
authors.lastname: Arbabi
authors.forename: Antonio
authors.initials: A
authors.lastname: Sánchez
authors.forename: Cees S
authors.initials: CS
authors.lastname: Roselaar
authors.forename: Mansour
authors.initials: M
authors.lastname: Aliabadian
authors.forename: Glenn-Peter
authors.initials: GP
authors.lastname: Sætre
mesh_terms: D000222:Adaptation, Physiological; D000383:Agriculture; D000818:Animals; D001502:Beak / Q000033:anatomy & histology* / Q000502:physiology; D004032:Diet; D017753:Ecosystem; D007492:Iran; D012639:Seeds; D012886:Skull / Q000033:anatomy & histology* / Q000502:physiology; D046370:Sparrows / Q000033:anatomy & histology* / Q000145:classification* / Q000235:genetics / Q000502:physiology
references.citation: Trends Ecol Evol. 2006 Jul;21(7):362-8
references.pmid: 16713653
references.citation: J Evol Biol. 2012 Apr;25(4):788-96
references.pmid: 22320215
references.citation: J Evol Biol. 2008 Jan;21(1):263-275
references.pmid: 18021202
references.citation: Evolution. 2003 May;57(5):1176-81
references.pmid: 12836833
references.citation: Nature. 2006 Aug 3;442(7102):563-7
references.pmid: 16885984
references.citation: Proc Natl Acad Sci U S A. 2003 Mar 4;100(5):2489-94
references.pmid: 12604784
references.citation: Nat Rev Genet. 2002 Jun;3(6):429-41
references.pmid: 12042770
references.citation: Science. 2002 Apr 26;296(5568):707-11
references.pmid: 11976447
references.citation: J Hum Evol. 2004 Jun;46(6):679-97
references.pmid: 15183670
references.citation: Heredity (Edinb). 2013 Oct;111(4):286-92
references.pmid: 23695379
references.citation: Trends Ecol Evol. 1991 May;6(5):166-8
references.pmid: 21232448
references.citation: Evolution. 2006 Dec;60(12):2490-7
references.pmid: 17263111
references.citation: Evol Dev. 2007 Jul-Aug;9(4):393-401
references.pmid: 17651363
references.citation: Science. 1981 Oct 2;214(4516):82-5
references.pmid: 17802577