title: Environmental niche variation and evolutionary diversification of the Brachypodium distachyon grass complex species in their native circum-Mediterranean range.
abstract: •
  
  
  OBJECTIVE
  We conducted environmental niche modeling (ENM) of the Brachypodium distachyon s.l. complex, a model group of two diploid annual grasses (B. distachyon, B. stacei) and their derived allotetraploid (B. hybridum), native to the circum-Mediterranean region. We (1) investigated the ENMs of the three species in their native range based on present and past climate data; (2) identified potential overlapping niches of the diploids and their hybrid across four Quaternary windows; (3) tested whether speciation was associated with niche divergence/conservatism in the complex species; and (4) tested for the potential of the polyploid outperforming the diploids in the native range.•
  
  
  METHODS
  Geo-referenced data, altitude, and 19 climatic variables were used to construct the ENMs. We used paleoclimate niche models to trace the potential existence of ancestral gene flow among the hybridizing species of the complex.•
  
  
  RESULTS
  Brachypodium distachyon grows in higher, cooler, and wetter places, B. stacei in lower, warmer, and drier places, and B. hybridum in places with intermediate climatic features. Brachypodium hybridum had the largest niche overlap with its parent niches, but a similar distribution range and niche breadth.•
  
  
  CONCLUSIONS
  Each species had a unique environmental niche though there were multiple niche overlapping areas for the diploids across time, suggesting the potential existence of several hybrid zones during the Pleistocene and the Holocene. No evidence of niche divergence was found, suggesting that species diversification was not driven by ecological speciation but by evolutionary history, though it could be associated to distinct environmental adaptations.
authors.affiliation: Department of Agriculture and Environmental Sciences, University of Zaragoza, Ctra. Cuarte km 1 22071 Huesca, Spain.
authors.forename: Diana
authors.initials: D
authors.lastname: López-Alvarez
authors.affiliation: Department of Plant and Animal Biology and Ecology, University of Jaén, Paraje las Lagunillas s n 23071 Jaén, Spain.
authors.forename: Antonio J
authors.initials: AJ
authors.lastname: Manzaneda
authors.affiliation: Department of Plant and Animal Biology and Ecology, University of Jaén, Paraje las Lagunillas s n 23071 Jaén, Spain.
authors.forename: Pedro J
authors.initials: PJ
authors.lastname: Rey
authors.affiliation: Department of Biotechnology-Plant Biology, School of Agriculture, Polytechnic University of Madrid 28040 Madrid, Spain.
authors.forename: Patricia
authors.initials: P
authors.lastname: Giraldo
authors.affiliation: Department of Biotechnology-Plant Biology, School of Agriculture, Polytechnic University of Madrid 28040 Madrid, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: Benavente
authors.affiliation: Department of Biological, Biomedical and Analytical Sciences, University of the West of England, Coldharbour Lane, Bristol BS16 1QY, UK.
authors.forename: Joël
authors.initials: J
authors.lastname: Allainguillaume
authors.affiliation: Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Plas Gogerddan, Aberystwyth SY23 3EB, Wales, UK.
authors.forename: Luis
authors.initials: L
authors.lastname: Mur
authors.affiliation: Biology Department, University of Massachusetts, Amherst, Massachusetts 01003 USA.
authors.forename: Ana L
authors.initials: AL
authors.lastname: Caicedo
authors.affiliation: Biology Department, University of Massachusetts, Amherst, Massachusetts 01003 USA.
authors.forename: Samuel P
authors.initials: SP
authors.lastname: Hazen
authors.affiliation: Department of Molecular Biology and Ecology of Plants, Tel-Aviv University, Tel-Aviv 69978 Israel.
authors.forename: Adina
authors.initials: A
authors.lastname: Breiman
authors.affiliation: Institute for Cereal Crops Improvement, Tel Aviv University, Tel Aviv 69978 Israel.
authors.forename: Smadar
authors.initials: S
authors.lastname: Ezrati
authors.affiliation: Department of Agriculture and Environmental Sciences, University of Zaragoza, Ctra. Cuarte km 1 22071 Huesca, Spain Department of Botany, Institute of Biology, Tomsk State University, Lenin Av. 36, Tomsk 634050, Russia.
authors.forename: Pilar
authors.initials: P
authors.lastname: Catalán
mesh_terms: D005075:Biological Evolution; D058431:Brachypodium / Q000235:genetics* / Q000502:physiology; D002980:Climate; D004171:Diploidy; D004463:Ecology; D004777:Environment; D019083:Mediterranean Region; D008962:Models, Theoretical; D011123:Polyploidy; D013045:Species Specificity
keywords: Brachypodium distachyon, B. stacei, B. hybridum; Poaceae; circum-Mediterranean native range; current and past bioclimatic envelopes; environmental niche modeling; model grasses; niche differentiation–conservatism; predicted distribution of potential hybrid zones