Laura Warman

Plant traits vary widely across species and underpin differences in ecological strategy. Despite centuries of interest, the contributions of different evolutionary lineages to modern-day functional diversity remain poorly quantified.Expanding data bases of plant traits plus rapidly improving phylogenies enable for the first time a data-driven global picture of plant functional diversity across the major clades of higher plants. We mapped five key traits relevant to metabolism, resource competition and reproductive strategy onto a phylogeny across 48324 vascular plant species world-wide, along with climate and biogeographic data. Using a novel metric, we test whether major plant lineages are functionally distinctive. We then highlight the trait–lineage combinations that are most functionally distinctive within the present-day spread of ecological strategies.For some trait–clade combinations, knowing the clade of a species conveys little information to neo- and palaeo-ecologists. In other trait–clade combinations, the clade identity can be highly revealing, especially informative clade–trait combinations include Proteaceae, which is highly distinctive, representing the global slow extreme of the leaf economic spectrum. Magnoliidae and Rosidae contribute large leaf sizes and seed masses and have distinctively warm, wet climatic distributions.Synthesis. This analysis provides a shortlist of the most distinctive trait–lineage combinations along with their geographic and climatic context: a global view of extant functional diversity across the tips of the vascular plant phylogeny.

QuestionAre plant traits more closely correlated with mean annual temperature, or with mean annual precipitation?Are plant traits more closely correlated with mean annual temperature, or with mean annual precipitation?LocationGlobal.Global.MethodsWe quantified the strength of the relationships between temperature and precipitation and 21 plant traits from 447,961 species-site combinations worldwide. We used meta-analysis to provide an overall answer to our question.We quantified the strength of the relationships between temperature and precipitation and 21 plant traits from 447,961 species-site combinations worldwide. We used meta-analysis to provide an overall answer to our question.ResultsMean annual temperature was significantly more strongly correlated with plant traits than was mean annual precipitation.Mean annual temperature was significantly more strongly correlated with plant traits than was mean annual precipitation.ConclusionsOur study provides support for some of the assumptions of classical vegetation theory, and points to many interesting directions for future research. The relatively low R2 values for precipitation might reflect the weak link between mean annual precipitation and the availability of water to plants.Our study provides support for some of the assumptions of classical vegetation theory, and points to many interesting directions for future research. The relatively low R2 values for precipitation might reflect the weak link between mean annual precipitation and the availability of water to plants.

Around the world tropical rainforests intergrade with open, fire-dependent (pyrophytic) vegetation forming landscapescale mosaics. However, rainforests and open vegetation are mostly studied independently from each other. This has been the case in the Australian Wet Tropics. This thesis begins by arguing that the vegetation of north-eastern Queensland can be considered as a complex system where rainforests and pyrophytic vegetation represent alternative stable states.

Leaves come in many sizes and shapes, and the relationships between leaf traits and the environments they occur in are better understood every day. However we still know very little about the ecological consequences of plants having either compound or simple leaves. We attempted to address this knowledge gap by comparing chemical and physical characteristics (leaf area, length:width ratio, water content, leaf mass per area, ‘toughness’ and C:N ratio), as well as rates of herbivory between compound and simple leaves across 34 species in adjacent rainforest, open woodland and wet sclerophyll (tall open forest) vegetation in northeastern Australia. We found C:N ratio to be lower in simple leaves, but this was the only leaf trait that differed significantly between leaf types and did not stand up under phylogenetic analysis. Overall, we found no differences in herbivory between simple and compound leaves. While it remains unclear what the advantages of having one leaf type over another might be, the differences do not seem to lie in construction, or in vulnerability to herbivores, at least in the Australian Wet Tropics.

The vegetation of the Wet Tropics bioregion of Far North Queensland is a complex system whose components (mainly tropical rainforests and fire-prone forests and woodlands) have mostly been studied independently from each other. We suggest that many characteristics of the vegetation are consistent with those of a complex, dynamic, spatially heterogeneous system which exhibits alternative stable states. We propose these states are driven and maintained by the interaction of vegetation-specific positive feedback loops with the regions’ environmental parameters (such as topography, steep humidity gradients and seasonality) and result in the rainforest/fire-prone vegetation mosaic that characterises the area. Given the regions’ magnitude, biodiversity and complexity, we propose the Wet Tropics as an important new example and a good testing ground for alternative stable state and resilience theories in large heterogeneous natural systems. At the same time, thinking in terms of alternative stable states and resilience creates a new context for understanding the regions’ biological dynamics.