title: Germination responses to current and future temperatures of four seeder shrubs across a latitudinal gradient in western Iberia.
abstract: OBJECTIVE
  Species differ in their temperature germination niche. Populations of a species may similarly differ across the distribution range of the species. Anticipating the impacts of climate variability and change requires understanding the differential sensitivity to germination temperature among and within species. Here we studied the germination responses of four hard-seeded Cistaceae seeders to a range of current and future temperatures.
  
  
  METHODS
  Seeds were collected at sites across the Iberian Peninsula and exposed or not exposed to a heat shock to break dormancy, then set to germinate under four temperature regimes. Temperatures were varied daily and seasonally, simulating the temperature range across the gradient, plus an increased temperature simulating future climate. Time to germination onset and cumulative germination at the end of each season were analyzed for the effects of temperature treatments, seasons, and local climate (temperature of the germination period, Tgp) at each site.
  
  
  RESULTS
  Tgpwas a significant covariate of germination in all species but Cistus populifolius. Temperature treatments significantly affected Cistus ladanifer, C. salviifolius, and Halimium ocymoides. Germination occurred in simulated autumn conditions, with little germination occurring at later seasons, except in unheated seeds of H. ocymoides. Exposure to a heat shock changed the sensitivity to temperature treatments and the relationships with Tgp.
  
  
  CONCLUSIONS
  Germination responses to temperature differ not only among species but also within species across their latitudinal range. The responses were idiosyncratic and related to the local climate of the population. This germination variability complicates generalizing the impacts of climate variability and climate change.
authors.affiliation: Departamento de Ciencias Ambientales, Universidad de Castilla-La Mancha, Av. Carlos III s/n 45071 Toledo, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Chamorro
authors.affiliation: Departamento de Ciencias Ambientales, Universidad de Castilla-La Mancha, Av. Carlos III s/n 45071 Toledo, Spain.
authors.forename: Belén
authors.initials: B
authors.lastname: Luna
authors.affiliation: Departamento de Ciencias Ambientales, Universidad de Castilla-La Mancha, Av. Carlos III s/n 45071 Toledo, Spain josem.moreno@uclm.es.
authors.forename: José M
authors.initials: JM
authors.lastname: Moreno
mesh_terms: D000531:Altitude; D030601:Cistaceae / Q000145:classification / Q000502:physiology*; D029758:Cistus / Q000145:classification / Q000502:physiology; D002980:Climate; D057231:Climate Change; D017753:Ecosystem; D005843:Geography; D018525:Germination / Q000502:physiology*; D016014:Linear Models; D011174:Portugal; D012621:Seasons; D012639:Seeds / Q000502:physiology*; D013030:Spain; D013045:Species Specificity; D013696:Temperature; D013997:Time Factors
keywords: Cistaceae; Cistus; Mediterranean shrubs; climate change; fire-cues; germination niche; hard seeds; physical dormancy; regeneration