Research in the Maherali Lab

Our research is focused on identifying the causes of physiological adaptation and its consequences for ecological processes at the population, community and ecosystem levels.  Because plant physiology strongly influences ecosystem function, predicting the course of physiological evolution is necessary to evaluate how ecosystem functions and services will be affected in the long-term by human influences on the abiotic and biotic environment. We use model species and systems to answer basic questions in physiological and evolutionary ecology and utilize ongoing biological invasions and climate change experiments to explore how physiology and evolution  can shape the assembly of communities and the functioning of ecosystems.

Research Themes

What are the causes of physiological adaptation to the abiotic environment? Because they are sessile, plants are vulnerable to many forms of abiotic and biotic stress. Of these potential stressors, water and nutrient limitation are ubiquitous, highly variable across space and time, and the most limiting to plant growth and net primary production in many environments. Although physiological variation along these resource gradients is often assumed to be adaptive, much of the evidence to support this assumption is indirect, i.e., it is derived from correlations between trait and abiotic resource variation. We use ecological genetic and phylogenetic tools to directly identify the causes of physiological adaptation and targets of natural selection. 

Research Questions:
1.    Which physiological traits are the targets of natural selection in contrasting resource environments and how does selection on physiology vary across time and space?
2.    In which kinds of environments does physiological plasticity evolve?
3.    How does shared evolutionary history influence physiological adaptation?
4.    How is physiological evolution constrained by the amount of genetic variation and genetic correlations among traits in populations?
5.    How do whole genome duplication events in the history of angiosperms (polyploidy) influence the evolution of physiology?

   Collaborators: Christina Caruso (UG), Brian Husband (UG), Robert Latta (Dalhousie).
   Postdoctoral Fellow: Patrick Vogan.
   Undergraduate Students: Nigel Gale.

How does plant function evolve in the context of ecological communities? The resource requirements and physiological tolerances of organisms change when they interact with competitors, predators, parasites and mutualists, suggesting that abiotic and biotic agents of selection interact to influence physiological adaptation. However, these perspectives are disconnected in theories of physiological adaptation and are rarely examined together in empirical studies. We use comparative phylogenetic, experimental and field studies to examine how interactions between mutualistic and antagonistic biotic components and the abiotic environment influence physiological evolution. We are especially interested in how interactions with arbuscular mycorrhizal (AM) fungi shape the function and evolution of plants.

Research Questions:
1.    What are the physiological mechanisms responsible for variation in plant responsiveness to AM fungi and other soil biota?
2.    How do interactions with soil biota influence the evolution of plant physiology?  How do these interactions change with resource availability?
3.    How do invasive species shape the physiological evolution of native species?  How will these evolutionary responses influence community structure?

   Postdoctoral Fellow: Patrick Vogan.
   Graduate Student: Gary Poon.
   Undergraduate Student: Emily Upham-Mills.

How  do functional traits, interactions with mutualists, and evolutionary history affect the assembly of communities and the functioning of ecosystems? A major goal in ecology is to discover mechanisms of community assembly. One hypothesis that accounts for non-random community assembly is competition. If species share a fundamental niche, then competitive exclusion will cause communities to be made up of species that have disimilar functional traits.  If these functional traits are phylogenetically conserved, then species will also be more distantly related to each other than would be expected by chance (phylogenetically even). Though competition has long been considered an important ecological process, competitive exclusion is rare in communities, which suggests that other processes such as trophic interactions and habitat filtering also shape community structure. We are examining how plant interactions with communities of AM fungi influence competition and co-existence in both fungal and plant communties.  

Research Questions: 
1.    How do functional traits and character evolution influence the assembly of AM fungal communities on plant roots?
2.    How are competitive interactions among plants influenced by fungal mediated affects on resource uptake and abiotic tolerances?

    Collaborator: John Klironomos (UBC).
    Graduate Students: Gary Poon, Sabina Stanescu.
   

How do mutualisms influence community dynamics and the functioning of ecosystems? In a recently (2007) established large scale field experiment, we are tracking the ecological impacts of 31 different cultivars of three grass species (perennial ryegrass, tall fescue and meadow fescue) on native grasslands.  Experimental plots have been invaded with grass cultivars that are either endophyte-free, endophyte-infected, or in some cases infected by ‘novel endophytes’.  We are examining how the experimental treatments affect the assembly of communities, successional dynamics, and ecosystem functioning.

    Collaborators: Jonathan Newman (UG), John Klironomos (UBC), Kathryn Yurkonis (UND).
    Undergraduate Student: Emily Drystek.

Research Funding is generously provided by...

The Natural Sciences and Engineering Research Council of Canada (NSERC)

The Canada Foundation for Innovation

The Ontario Ministry of Research and Innovation

The Ontario Ministry of Food, Agriculture & Rural Affairs