title: Character displacement among bat-pollinated flowers of the genus Burmeistera: analysis of mechanism, process and pattern.
abstract: Coexisting plants that share pollinators can compete through interspecific pollen transfer. A long-standing idea holds that divergence in floral morphology may reduce this competition by placing pollen on different regions of the pollinator's bodies. However, surprisingly little empirical support for this idea exists. Burmeistera is a diverse neotropical genus that exhibits wide interspecific variation in the degree to which the reproductive parts are exserted outside the corolla. Coexisting Burmeistera share bats as their primary pollinators, and the degree of exsertion determines the site of pollen deposition on the bats' heads. Here we study the mechanism, process and pattern of floral character displacement for assemblages of coexisting Burmeistera. Flight cage experiments with bats and pairs of Burmeistera species demonstrate that the greater the divergence in exsertion length, the less pollen transferred interspecifically. Null model analyses of exsertion lengths for 19 species of Burmeistera across 18 sites (each containing two to four species) demonstrate that observed assemblage structure is significantly overdispersed relative to what would be expected by chance. Local evolution, rather than ecological sorting, appears to be the primary process driving this pattern of overdispersion because local adaptation of the nine widespread species accounts for a large portion of the observed pattern. Taken together, results of this study provide strong support for the idea that competition through interspecific pollen transfer can drive character displacement in plants.
authors: Department of Biology, University of Miami, Coral Gables, FL 33124, USA. n_muchhala@yahoo.com
authors: Nathan
authors: N
authors: Muchhala
authors: Matthew D
authors: MD
authors: Potts
mesh_terms: D000818:Animals; D005075:Biological Evolution; D029422:Campanulaceae / Q000502:physiology*; D002685:Chiroptera / Q000502:physiology*; D005247:Feeding Behavior / Q000502:physiology*; D008954:Models, Biological; D011058:Pollen / Q000502:physiology*
references: Am J Bot. 2001 Feb;88(2):213-9
references: 11222244
references: Oecologia. 2003 Feb;134(3):373-80
references: 12647145
references: Proc Natl Acad Sci U S A. 2006 Jan 24;103(4):956-61
references: 16418284
references: Am Nat. 2006 Jan;167(1):67-80
references: 16475100
references: Evolution. 2006 Mar;60(3):538-52
references: 16637499
references: Nature. 2006 Dec 7;444(7120):701-2
references: 17151655
references: Trends Ecol Evol. 1995 Feb;10(2):67-71
references: 21236955
references: Am J Bot. 2006 Aug;93(8):1081-9
references: 21642173
references: Oecologia. 2000 Aug;124(3):332-342
references: 28308770
references: Oecologia. 2001 Sep;129(1):43-49
references: 28547066
references: Evolution. 1981 Nov;35(6):1206-1228
references: 28563391
references: Evolution. 1968 Mar;22(1):202-210
references: 28564982
references: Evolution. 1990 May;44(3):558-569
references: 28567973
references: Evolution. 1979 Sep;33(3):897-913
references: 28568434
references: Am Nat. 2000 Sep;156(3):322-328
references: 29587501
references: Am Nat. 2000 Oct;156(S4):S17-S34
references: 29592584