Abstract Detail

Ecology

Moore, Timothy [1], Cramer, Michael [2], Verboom, G. Anothony [2].

The adaptive significance of leaf size and shape variation in Jamesbrittenia (Scrophulariaceae: Manuleae).

The genus Jamesbrittenia (Scrophulariaceae: Manuleae) is widespread in southern Africa, where it occupies a diversity of environments and shows striking variation in leaf size and shape. This leaf form variation may reflect adaptation for leaf thermoregulation or water conservation in contrasting habitats. To evaluate these competing hypotheses, we correlated leaf form variation in Jamesbrittenia against a series of environmental variables (soil nutrients, rainfall and temperature). We also compared rates of water and heat loss in potted plants representing a sample of Jamesbrittenia species of variable leaf size and shape. Although species showed significant variation in leaf temperature under experimental conditions, this variation was not correlated with leaf size. Whilst water loss per leaf area was greater in smaller-leaved species, the shoots of larger leaved species showed higher rates of water loss overall due to their higher leaf area per shoot length. Consistent with these results, interspecific leaf size variation in a clade of summer-rainfall perennial species was strongly correlated with rainfall received during the driest time of the year, even when comparisons were phylogenetically controlled. In contrast, leaf size was poorly correlated with environmental variables in the predominantly annual, winter-rainfall clade. Since reduced leaf size leads to reduced leaf area per shoot length in Jamesbrittenia, the evolution of smaller leaves represents an adaptation for reduced water loss during the dry season.

1 - University of Connecticut, Ecology and Evolutionary Biology, 75 N Eagleville, Torrey Life Science Building, Storrs, Connecticut, 06269-3043, United States
2 - University of Cape Town, Department of Biological Sciences, Private Bag X3, Rondebosch, Cape Town, Western Cape, 7701, South Africa

Keywords:
boundary layer
comparative method
life history.

Presentation Type: Oral Paper
Session: 14, Ecology Section: Plant Functional Traits and Responses
Location: 201/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 3:45 PM
Number: 14007
Abstract ID:924
Candidate for Awards:Ecological Section Best Graduate Student Paper