title: The influence of habitat on the evolution of plants: a case study across Saxifragales.
abstract: Organismal evolution tends to be closely associated with ecological conditions. However, the extent to which this association constrains adaptation or diversification into new habitats remains unclear. We studied habitat evolution in the hyper-diverse angiosperm clade Saxifragales.
  
  
  
  We used species-level phylogenies for approx. 950 species to analyse the evolution of habitat shifts as well as their influence on plant diversification. We combined habitat characterization based on floristic assignments and state-of-the art phylogenetic comparative methods to estimate within- and across-habitat diversification patterns.
  
  
  
  Our analyses showed that Saxifragales diversified into multiple habitats from a forest-inhabiting ancestor and that this diversification is governed by relatively rare habitat shifts. Lineages are likely to stay within inferred ancestral ecological conditions. Adaptation to some habitat types (e.g. aquatic, desert) may be canalizing events that lineages do not escape. Although associations between increased diversification rates and shifts in habitat preferences are occasionally observed, extreme macroevolutionary rates are closely associated with specific habitats. Lineages occurring in shrubland, and especially tundra and rock cliffs, exhibit comparatively high diversification, whereas forest, grassland, desert and aquatic habitats are associated with low diversification.
  
  
  
  The likelihood of occupation of new habitats appears to be asymmetric. Shifts to aquatic and desert habitats may be canalizing events. Other habitats, such as tundra, might act as evolutionary sources, while forests provide the only habitat seemingly colonized easily by lineages originating elsewhere. However, habitat shifts are very rare, and any major environmental alteration is expected to have dramatic evolutionary consequences.
authors.affiliation: Estación Experimental de Zonas Áridas, EEZA-CSIC, Carretera de Sacramento s/n, 04120 Almería, Spain rafa.rubiodecasas@gmail.com dsoltis@ufl.edu.|CEFE UMR 5175, CNRS, Universite de Montpellier, Universite Paul-Valery 7 Montpellier, EPHE, 1919 route de Mende, 34293 Montpellier cedex 05, France.|Departamento de Ecología, Facultad de Ciencias, Universidad de Granada, Avda. de la Fuentenueva s/n, 18071 Granada, Spain.
authors.forename: Rafael Rubio
authors.initials: RR
authors.lastname: de Casas
authors.affiliation: Department of Ecology and Evolutionary Biology and Biodiversity Institute, University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS 66045-7543, USA.
authors.forename: Mark E
authors.initials: ME
authors.lastname: Mort
authors.affiliation: Department of Biology, University of Florida, Gainesville, FL 32611, USA rafa.rubiodecasas@gmail.com dsoltis@ufl.edu.|Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA.
authors.forename: Douglas E
authors.initials: DE
authors.lastname: Soltis
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics; D044822:Biodiversity; D005075:Biological Evolution; D017753:Ecosystem; D010802:Phylogeny; D031995:Saxifragaceae / Q000235:genetics* / Q000502:physiology
keywords: Aeonium; Crassulaceae; Macaronesia; Saxifraga; anagenesis; cladogenesis; climate change; diversification; ecotone; habitat selection; niche conservatism