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Abstract Detail



Ecological Section

Carlson, Jane [1], Holsinger, Kent [2].

Evolutionary transitions between color monomorphism and polymorphism in the genus Protea and the role of local ecological processes.

Phenotypic polymorphisms are either actively maintained by natural selection or are neutral consequences of mutation and genetic drift. Similarly, the presence of a striking polymorphism in one species and its absence in another reflects either differential adaptation to divergent ecological circumstances or artifacts of evolutionary history. For flower color polymorphisms, the persistence of different color morphs is often linked to selection mediated by pollinators, enemies or abiotic effects, yet it is unknown whether this adaptive basis extends to the interspecific level. In other words, is the absence of color polymorphism associated with shifts in the pressures involved in its maintenance? We address this question by comparing traits and interactions of closely related polymorphic and monomorphic species and assessing whether differences can be predicted based on 'scaling-up' of local ecological processes. We focus on the plant genus Protea of South Africa, within which >40% of species have co-occurring pink and white floral color morphs. Our previous work within four Protea species revealed fertility advantages in white morphs but reduced seed predation in pink morphs. We therefore predict that monomorphic pink species should have lighter seeds, smaller inflorescences and less predation than their co-occurring polymorphic species. We further expect that for those traits, monomorphic pink species should more closely resemble pink relative to white morphs. If non-adaptive processes are more important in determining polymorphism, we expect site-level or species-level effects to better explain differences in these traits. The study was conducted in two sites in western South Africa, each site containing one polymorphic species and one monomorphic pink species from the same clade. Between June and July 2012, we measured a suite of plant traits on 12-24 plants per species including inflorescence size, seed mass, and rates of seed predation. Using these traits as response variables, we performed nested ANOVAs. Focal predictors were polymorphism presence or absence, site, flowerhead color, and species. We found that in support of our expectations, the monomorphic pink species in each site had reduced seed predation and smaller inflorescences than did the polymorphic species. However, we detected no differences in seed mass between species pairs, and monomorphs were no more similar to pink morphs than to white morphs for any trait. Although within-species patterns were not as expected, these findings indicate that selection associated with seed predators and inflorescence size not only promotes polymorphism maintenance within some species, it may also be linked to monomorphism in others.

Broader Impacts:


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1 - Nicholls State University, Biological Sciences , P.O. Box 2021, Thibodaux, LA, 70310, USA
2 - University of Connecticut, Department of Ecology & Evolutionary Biology, 75 N. Eagleville Road, U-3043, STORRS, CT, 06269-3043, USA

Keywords:
seed predation
evolutionary and ecological adaptation
Flower color and shape
South Africa
Protea
polymorphism.

Presentation Type: Oral Paper:Papers for Sections
Session: 32
Location: Marlborough B/Riverside Hilton
Date: Tuesday, July 30th, 2013
Time: 2:15 PM
Number: 32004
Abstract ID:432
Candidate for Awards:None


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