title: Localized versus generalist phenotypes in a broadly distributed tropical mammal: how is intraspecific variation distributed across disparate environments?
abstract: BACKGROUND
  The extent of phenotypic differentiation in response to local environmental conditions is a key component of species adaptation and persistence. Understanding the structuring of phenotypic diversity in response to local environmental pressures can provide important insights into species evolutionary dynamics and responses to environmental change. This work examines the influence of steep environmental gradients on intraspecific phenotypic variation and tests two hypotheses about how the tropical soft grass mouse, Akodon mollis (Cricetidae, Rodentia), contends with the disparate environmental conditions encompassed by its broad distribution. Specifically, we test if the species expresses a geographically unstructured, or generalist, phenotype throughout its range or if it shows geographically localized morphological differentiation across disparate environments.
  
  
  RESULTS
  Using geometric morphometric and ecomorphological analyses of skull shape variation we found that despite distinct environmental conditions, geographically structured morphological variation is limited, with the notable exception of a distinct morphological disjunction at the high-elevation forest-grassland transition in the southern portion of A. mollis distribution. Based on genetic analyses, geographic isolation alone does not explain this localized phenotype, given that similar levels of genetic differentiation were also observed among individuals inhabiting other ecosystems that are nonetheless not distinct morphologically.
  
  
  CONCLUSIONS
  Instead of phenotypic specialization across environments in these tropical mountains, there was limited differentiation of skull shape and size across the broad range of A. mollis, with the exception of individuals from the puna, the highest-elevation ecosystem. The high morphological variance among individuals, together with a weak association with local environmental conditions, not only highlights the flexibility of A. mollis' skull, but also highlights the need for further study to understand what maintains the observed morphological patterns. The work also indicates that mechanisms other than processes linked to local ecological specialization as a driver of diversification may contribute to the high diversity of this tropical region.
authors.affiliation: Department of Ecology & Evolutionary Biology, Museum of Zoology, University of Michigan, Ann Arbor, MI 48109-1079, USA. dalvarad@umich.edu
authors.forename: Diego F
authors.initials: DF
authors.lastname: Alvarado-Serrano
authors.forename: Lucia
authors.initials: L
authors.lastname: Luna
authors.forename: L Lacey
authors.initials: LL
authors.lastname: Knowles
mesh_terms: D000220:Adaptation, Biological; D000818:Animals; D003411:Arvicolinae / Q000033:anatomy & histology* / Q000145:classification* / Q000502:physiology; D005075:Biological Evolution; D017753:Ecosystem; D004777:Environment; D040961:Genetic Drift; D009929:Organ Size; D010568:Peru; D010641:Phenotype; D012886:Skull / Q000033:anatomy & histology
references.citation: J Mammal. 2016 Jun 9;97(3):663-688
references.pmid: 29692469
references.citation: Heredity (Edinb). 2005 Feb;94(2):217-28
references.pmid: 15523507
references.citation: Mol Ecol. 2008 Jan;17(1):450-63
references.pmid: 17892465
references.citation: Evol Bioinform Online. 2007 Feb 23;1:47-50
references.pmid: 19325852
references.citation: Cancer Res. 1967 Feb;27(2):209-20
references.pmid: 6018555
references.citation: Am Nat. 2012 Jul;180(1):50-9
references.pmid: 22673650
references.citation: PLoS One. 2011;6(10):e25630
references.pmid: 21991324
references.citation: Physiol Biochem Zool. 1999 Sep-Oct;72(5):613-22
references.pmid: 10521329
references.citation: J Morphol. 1996 Aug;229(2):229-37
references.pmid: 8755340
references.citation: Folia Primatol (Basel). 1989;53(1-4):190-202
references.pmid: 2606395
references.citation: Genetics. 1943 Mar;28(2):114-38
references.pmid: 17247074
references.citation: Integr Comp Biol. 2006 Feb;46(1):5-17
references.pmid: 21672718
references.citation: J Exp Biol. 2001 Jun;204(Pt 11):1991-2000
references.pmid: 11441040
references.citation: Proc Natl Acad Sci U S A. 2008 May 6;105(18):6668-72
references.pmid: 18458348
references.citation: J Evol Biol. 2009 Aug;22(8):1669-78
references.pmid: 19538346
references.citation: Am Nat. 2000 Oct;156(4):390-415
references.pmid: 29592141
references.citation: J Morphol. 2012 Dec;273(12):1319-37
references.pmid: 22833466
references.citation: J Hum Evol. 2004 Jun;46(6):655-77
references.pmid: 15183669
references.citation: Mol Ecol Resour. 2011 Mar;11(2):353-7
references.pmid: 21429143
references.citation: J Evol Biol. 2012 Jul;25(7):1275-90
references.pmid: 22519748
references.citation: Evolution. 2012 Aug;66(8):2587-98
references.pmid: 22834755
references.citation: Trends Ecol Evol. 2009 Sep;24(9):487-96
references.pmid: 19500875
references.citation: J Morphol. 2010 Aug;271(8):897-909
references.pmid: 20623653
references.citation: Naturwissenschaften. 2009 Jan;96(1):93-101
references.pmid: 18843477
references.citation: J Morphol. 2009 Nov;270(11):1338-47
references.pmid: 19480012
references.citation: Am Nat. 2003 Jan;161(1):1-28
references.pmid: 12650459
references.citation: Evolution. 2010 May;64(5):1231-44
references.pmid: 19922442
references.citation: PLoS Biol. 2007 Sep;5(9):e219
references.pmid: 17696646
references.citation: Ecology. 2006 Oct;87(10):2603-13
references.pmid: 17089668
references.citation: Evolution. 2011 Apr;65(4):946-60
references.pmid: 21073450
references.citation: Evolution. 2004 Aug;58(8):1781-93
references.pmid: 15446430
references.citation: Nature. 2004 Jun 24;429(6994):870-3
references.pmid: 15215863
references.citation: Science. 1993 Jan 29;259(5095):639-46
references.pmid: 8430313
references.citation: Mol Ecol. 2010 Sep;19(17):3727-45
references.pmid: 20723059
references.citation: Trends Genet. 2003 Nov;19(11):585-8
references.pmid: 14585605
references.citation: Evolution. 2005 Nov;59(11):2460-72
references.pmid: 16396186
references.citation: Evolution. 2002 Oct;56(10):1909-20
references.pmid: 12449478
references.citation: Ecol Lett. 2012 May;15(5):475-83
references.pmid: 22414160
references.citation: Evolution. 2007 Feb;61(2):346-67
references.pmid: 17348945
references.citation: J Evol Biol. 2010 Feb;23(2):237-48
references.pmid: 20002248
references.citation: C R Acad Hebd Seances Acad Sci D. 1972 Feb 7;274(6):940-2
references.pmid: 4622883
references.citation: Proc Biol Sci. 2011 Apr 22;278(1709):1131-40
references.pmid: 21227966