title: Differential response of the homoploid hybrid species Iris nelsonii (Iridaceae) and its progenitors to abiotic habitat conditions.
abstract: OBJECTIVE
  Homoploid hybrid speciation involves the evolution of reproductive isolation between a hybrid lineage and its progenitors without a change in chromosome number. Ecological divergence presumably plays a large role in the stabilization of hybrid lineages, as all homoploid hybrid species described to date are reported to be ecologically divergent from their progenitors. However, the described ecological divergence in most systems is anecdotal and has not been empirically tested.
  
  
  METHODS
  We assessed the vegetative response of Iris nelsonii, a homoploid hybrid species, and its three progenitor species, I. brevicaulis, I. fulva, and I. hexagona, to different abiotic conditions (i.e., varied sunlight availability and flooding conditions) that largely characterize the habitats of these four species in their natural habitats in Louisiana, USA.
  
  
  RESULTS
  The species differed in their responses to the water-level treatment for many of the response variables, including rhizome weight, ramet growth, plant height, and two principal components used to characterize the data. The species differed in their response to the light-level treatment for root allocation and the principal component used to characterize plant size. Iris nelsonii significantly differed from its progenitors, including its most closely related progenitor species, in response to many of the treatments.
  
  
  CONCLUSIONS
  The differential response to abiotic habitat conditions of I. nelsonii suggests that this species is ecologically divergent from its progenitor species.
authors.affiliation: Department of Biology, Texas State University-San Marcos, San Marcos, Texas 78666, USA. st1188@txstate.edu
authors.forename: Sunni J
authors.initials: SJ
authors.lastname: Taylor
authors.forename: Rees W
authors.initials: RW
authors.lastname: Willard
authors.forename: Joshua P
authors.initials: JP
authors.lastname: Shaw
authors.forename: Mary C
authors.initials: MC
authors.lastname: Dobson
authors.forename: Noland H
authors.initials: NH
authors.lastname: Martin
mesh_terms: D002678:Chimera / Q000254:growth & development / Q000502:physiology*; D004463:Ecology; D017753:Ecosystem; D055868:Floods; D040582:Inheritance Patterns; D031323:Iris Plant / Q000254:growth & development / Q000502:physiology*; D008145:Louisiana; D018515:Plant Leaves / Q000254:growth & development / Q000502:physiology; D025341:Principal Component Analysis; D027343:Rhizome / Q000254:growth & development / Q000502:physiology; D013045:Species Specificity; D013472:Sunlight; D014867:Water / Q000378:metabolism
chemical_list: D014867:Water