The importance of evolutionary history in studies of plant physiological ecology: examples from cerrados and forests of central Brazil

Abstract

Studies that compare physiology, anatomy, and ecology across species have offered some of the best insight into adaptation and evolutionary constraints in plants. As a result, the comparative approach has become increasingly used in studies of plant physiological ecology. The high species diversity of Brazilian biomes provides many excellent opportunities for comparative plant ecophysiology, and could be better exploited for understanding the evolution of plant form and function. In this paper we emphasize the importance of considering phylogenetic information for the design and analysis of comparative studies, relying on examples from comparisons of woody plants from cerrado and gallery (riparian) forests. The use of congeneric species pairs, each containing one cerrado species and one forest species of the same genus, greatly improves statistical power while assuring phylogenetic independence, an essential condition for inference in comparative studies. For example, in a study of seedlings of nine cerrado species and nine forest species, when we ignore phylogenetic relationships, it is not be possible to conclude that cerrado and forest species differ with regard to leaf area ratio (LAR), specific leaf area (SLA), or seedling height. If, however, we use the generic groupings to account for phylogenetic effects, then we find that seedlings of savanna species have lower LAR, SLA, and seedling height. Much of the phylogenetic inertia observed for these traits appears related to the fact that these traits are all strongly correlated with seed mass, which has been previously shown to be strongly conserved phylogenetically. These examples emphasize the importance of phylogenetic information in comparative studies. Key words: Cerrado, forest, specific leaf area, leaf area ratio, phylogeny A importância da história evolutiva em estudos de ecofisiologia vegetal: exemplos dos cerrados e florestas do Brasil Central: Estudos que comparam a fisiologia, anatomia e ecologia das espécies têm oferecido algumas das melhores apreciações sobre as limitações adaptativas e evolucionárias em plantas. Como resultado, a abordagem comparativa tem sido cada vez mais utilizada em estudos de ecofisiologia vegetal. A alta diversidade de espécies dos biomas brasileiros fornece excelentes oportunidades para estudos de ecofisiologia vegetal comparada, uma abordagem que poderia ser melhor explorada em pesquisas que visam a compreensão da evolução da forma e função em plantas. Neste artigo nós enfatizarmos a importância de considerar a informação filogenética no desenho e analises de estudos comparativos, utilizando como exemplos espécies lenhosas do cerrado e de mata de galeria (mata ripária). O uso de pares congenéricos, cada par contendo uma espécie do cerrado e uma espécie de floresta do mesmo gênero, aumenta o poder estatístico das análises, enquanto assegura concomitantemente a independência filogenética, uma condição essencial para inferência em estudos comparativos. Por exemplo, em um estudo comparativo de nove espécies do cerrado e nov...

Structural and functional leaf traits of two Gochnatia species from distinct growth forms in a sclerophyll forest site in Southeastern Brazil

“…The differences in A mass were likely to be influenced by the differences in SLA. Specific leaf area for both species showed values normally reported for "Cerrado" species (75-200 cm 2 g -1 ) (Hoffmann & Franco 2008), however, when comparing the values of SLA of the species we found lower values for G. polymorpha than for G. barrosii. Lower values of SLA are linked to a high investment in leaf thickness (Sefton et al 2002;Dahlgren et al 2006), which is a common aspect in leaves experiencing high light intensities or low nutrient availability (Turner 1994).…”

“…The differences in light conditions may impose adaptation or acclimation of leaves according to the level of light availability: leaves of emergent or canopy trees are exposed to high light intensities and normally are small and thick (Valladares & Niinemets 2008), whereas large and thin leaves of understory species may be a response to limited light conditions (Evans & Poorter 2001;Santiago & Wright 2007). Understanding responses to the local availability of light is fundamental to understanding the adaptation of such species to the forest environment (Hoffmann & Franco 2008).…”

Decoupling phylogenetic and functional diversity to reveal hidden signals in community assembly

“…This can be useful, for example, when species functional differentiation across habitats is due to replacement of functionally different species from the same clades (Fig. ), like changes in body size along latitude, or when traits vary across habitats mostly within a genus (Hoffmann & Franco ; Revell ; Diniz‐Filho et al . ; de Bello et al .…”

On the need for phylogenetic ‘corrections’ in functional trait-based approaches

“…If some traits become significant only after applying phylogenetic information, then differences between habitats are observable only in changes between more closely related species, i.e. within clades, for example, as a replacement of congeneric species with different traits along environmental gradients (Hoffmann and Franco 2009). This would imply a recent adaptation to either one or both habitats -one that would remain hidden if the evolutionary relationships between species were not taken into account.…”