Alternative Designs and the Evolution of Functional Diversity

Biology Department, McGill University, 1205 Dr. Penfield Avenue, Montreal, Quebec H3A 1B1, Canada.
The American Naturalist (Impact Factor: 3.83). 02/2006; 167(1):55-66. DOI: 10.1086/498276
Source: PubMed


According to conventional wisdom, functional diversity is exclusively a consequence of species having evolved adaptations to fill different niches within a heterogeneous environment. This view anticipates only one optimal combination of trait values in a given environment, but it is also conceivable that alternative designs of equal fitness in the same environment might evolve. To investigate that possibility, we use a genetic algorithm to search for optimal combinations of 34 functional traits in a realistic model of tree seedling growth and survival. We show that separate lineages of seedlings evolving in identical environments result in many alternative functional designs of approximately equal fitness.

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Available from: Christian Marks, Oct 07, 2014
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    • "2C–E and 3). These results support the idea that the integrated effects of functionally linked traits may lead to low overall functional diversity due to approximately equal fitness among species in a locality (Marks and Lechowicz 2006a) and that communities can arise with an apparently neutral pattern based on an underlying, complex traitbased niche process (Purves and Pacala 2005). "
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    ABSTRACT: Niche differentiation arising in functional trait diversity is expected to increase the potential for species coexistence, but empirical evidence for these relationships is sparse. We test whether grazing increases the functional diversity of leaf traits and niche differentiation in phosphorus limited Tibetan alpine meadows. We measured five traits in the leaf economic spectrum (LES; LC, leaf carbon concentration; LN, leaf nitrogen concentration; LP, leaf phosphorus concentration; SLA, specific leaf area; and LDMC, leaf dry matter content) for all species occurring in grazed and ungrazed plots at each of five sites. By comparing indicators of the fundamental and realized niches of co-occurring plants in both grazed and ungrazed plots, we quantified a grazing-mediated competitive effect on trait divergence and convergence. This trait response reflects the relative importance of niche differentiation and competitive exclusion in response to grazing. We found that while grazing induced LP divergence, both LC and LN tended to converge under grazing. Grazing had no effect on either SLA or LDMC diversity. When all five traits are considered together as a functionally integrated suite (LES hypervolume), there is no evidence for either divergence or convergence in response to grazing. Although grazing promotes functionally relevant diversity in LP that enables niche differentiation in competition for scarce soil available P, these results suggest that coordinated shifts in other LES traits sustain effective overall foliar function despite shifts in LP.
    Ecosphere 09/2015; 6(9):Artical 150. DOI:10.1890/ES14-00547.1 · 2.26 Impact Factor
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    • "This anticipated contrast in structural stability (SLA and LDMC) versus stoichiometric lability (LCC, LNC and LPC) under grazing together with the potential for trade-offs among these five foliar traits raises the possibility of grazing responses in three different components of FD—functional richness, functional divergence and functional evenness (Villéger et al. 2008; Mouchet et al. 2010). In this regard, we hypothesized that: (i) the increased species richness of alpine meadow communities that occurs when grazing reduces competitive conclusion (Niu et al. 2012) should also enhance functional richness in the suite of LES traits; (ii) the countervailing effects of decreased light competition and increased competition for nutrients and water under grazing should leave both functional divergence and functional evenness in the suite of LES traits unchanged because of coordinated trade-offs among the traits (Marks and Lechowicz 2006a; Reich 2014). In summary, in this paper we investigate the possibility that grazing in Tibetan alpine meadows tends to increase competition for soil phosphorus while decreasing competition for light, resulting in an increase in the functional richness in grazed plant communities without any significant changes in the overall functional diversity of foliar traits. "

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    • "1989 ) . This can result in contrasting phenotypes with similar fitness ( Marks and Lechowicz 2006 ) . In addition , it might be that intraspecific variation is large when compared to interspecific trait variation . "

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