Research

jc

Doing the funky chicken in a River Murray wetland.

I am a plant ecologist with an interest in community assembly and invasion ecology. I am particularly interested in how environmental and geographic factors affect the functional composition of plant communities at the landscape scale, and I focus on invasion ecology to tackle such questions. Humans can alter “natural” community assembly rules by altering environmental filters and dispersal patterns. Increased understanding of the role of these factors could be used to alleviate some of the ecological degradation caused by humans.

While rooted in community and invasion ecology, my work and interests extend to succession, species coexistence, disturbance, ecosystem restoration, vegetation management, novel ecosystems, assisted colonization, river health, environmental flows and climate change. To tackle these topics, I typically combine ecological theory with empirical and quantitative approaches and I collaborate widely. Working with a broad range of people is easily one of the highlights of my job.

Research themes

  1. Community assembly and biological invasion
  2. Testing ecological theory with invaders
  3. Using traits to increase mechanistic understanding
  4. Clarity in invasion ecology
  5. Applied ecology and conservation biology (often in relation to rivers)

 

1.  Community assembly and biological invasion

Regardless of whether a species is native or exotic, it must have a sufficient number of propagules, be able to acquire enough resources for growth and survival, and must be able to withstand interactions with competitors and predators in order to join a community. Although there are some characteristics that set exotic species apart (namely their strong association with humans and novel evolutionary histories), the process of community assembly is effectively the same regardless of species origin.

Through the addition of new species into a system, biological invasion effectively acts as a real-life experiment in community assembly (albeit one that lacks controls). Identifying the mechanisms that drive exotic species establishment can therefore increase our understanding of community assembly, a task that is otherwise challenging due to the long temporal and broad spatial scales at which community dynamics typically operate.

Of course, things can work the other way too: better understanding of the importance of community assembly processes (like environmental filtering and biotic interactions) can advance invasion ecology and guide environmental policy and management.

cc IMG_0950

Some of my experimental plots at Cedar Creek Ecosystem Science Reserve, Minnesota. This was the first summer after seeding. I wonder how different they’ll look after a couple of decades.

Examples 

Richard Duncan and I have a Discovery project that touches on this theme.

I am currently working with Nicki MunroCindy Hauser, Brendan Wintle, Adam Clark and Dave Tilman on a project that I have nominally entitled “the process of invasion”.

My DECRA field experiment and work with Dave Tilman targets this general theme.

Catford, J.A., Jansson, R. & Nilsson, C. (2009) Reducing redundancy in invasion ecology by integrating hypotheses into a single theoretical framework. Diversity and Distributions 15: 22‐40. pdf

Catford, J.A. & Jansson, R. (2014) Drowned, buried and carried away: effects of plant traits on the distribution of native and alien species in riparian ecosystems. New Phytologist (Tansley Review). abstract pdf (open access)

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2.  Testing ecological theory with invaders

As an offshoot to Theme 1, I like to test some key theoretical ideas using invading species – whether they are exotic or added as part of an experiment.

Examples 

Michael BodeDave Tilman and I are currently examining ways in which human-mediated species invasions may disrupt competition-colonisation tradeoffs and, as a consequence, species coexistence.

Catford, J.A., Daehler, C.C., Murphy, H.T., Sheppard, A.W., Hardesty, B.D., Westcott, D.A., Rejmánek, M., Bellingham, P.J., Pergl, J., Horvitz, C.C. & Hulme, P.E. (2012) The intermediate disturbance hypothesis and plant invasions: implications for species richness and management. Perspectives in Plant Ecology, Evolution & Systematics 14: 231-241. pdf (more about this paper here)

Catford, J.A., Downes, B.J., Gippel, C.J. & Vesk, P.A. (2011) Flow regulation reduces native plant cover and facilitates exotic invasion in riparian wetlands. Journal of Applied Ecology 48: 432-442. pdf

 

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3.  Using traits to increase mechanistic understanding

Cha_fa_(J1-J3)_2_jul_2014

The lovely (juvenile) leaves of Chaemacrista fasciculata, one of the “invaders” in my Cedar Creek experiment.

Species can be characterised based on morphological, physiological, phenological and behavioural traits that affect their growth, reproduction and survival. Based on species characteristics rather than identity, functional traits can act as a universal currency in which the characteristics and responses of myriad species can be compared. Functional traits thus provide a fabulous tool for community ecology. By enabling ready comparison across regions, ecosystems and taxa, functional traits can help us to understand general processes, like mechanisms of species coexistence and characteristics related to species rarity and dominance. Traits have been widely used to characterise species that are invasive and non-invasive, which has been very useful for biosecurity and species risk assessment.

 

Examples 

I’ve got a number of trait-based projects in the pipeline with Dave Tilman, Peter Reich, Jeanine Cavender-Bares and Peter Wragg.

Catford, J.A., Naiman, R.J., Chambers, L.E., Roberts, J., Douglas, M.M. & Davies, P.M. (in press) “Predicting novel riparian ecosystems in a changing climate” Ecosystems. Online. pdf  (more about that here).

Catford, J.A., Morris, W.K., Vesk, P.A., Gippel, C.J. & Downes, B.J. (2014) Species and environmental characteristics point to flow regulation and drought as drivers of riparian plant invasion. Diversity and Distributions 20: 1084-1096. abstract

Catford, J.A. & Jansson, R. (2014) Drowned, buried and carried away: effects of plant traits on the distribution of native and alien species in riparian ecosystems (Tansley Review). New Phytologist 204: 19-36. abstract pdf 

 

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4.  Clarity in invasion ecology

Many concepts used in invasion ecology are slightly (if not very) ambiguous. How do weeds, pests, invasives, aliens, exotics and non-indigenous species differ? What exactly do “species invasiveness” and “ecosystem invasibility” mean? And how distinct are the ideas underpinning the limiting similarity, opportunity windows and empty niche hypotheses?

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The three primary drivers of invasion (invasion = the big black spot in the middle). From Catford, Jansson & Nilsson (2009).

Despite many valiant efforts to define and clarify concepts used in invasion ecology, a lot of confusion still remains. This certainly isn’t unique to invasion ecology (what is a niche, after all?!), but it does provide challenges for the discipline. It is very hard to increase general understanding of invasion when species classified as invasive in one region or one study may be classified as non-invasive in another. Plus, if we struggle to define these terms, how are we expected to quantify them in a general and meaningful way?

Examples 

I’m currently doing a bit of “quantitative” work in relation to this theme with Mick McCarthy, John Baumgartner and Pete Vesk.

Catford, J.A., Jansson, R. & Nilsson, C. (2009) Reducing redundancy in invasion ecology by integrating hypotheses into a single theoretical framework. Diversity and Distributions 15: 22‐40. pdf

Catford, J.A., Vesk, P.A., Richardson, D.M. & Pyšek, P. (2012) Quantifying levels of biological invasion: towards the objective classification of invaded and invasible ecosystems. Global Change Biology 18: 44-62. pdf

 

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5.  Applied ecology and conservation biology (often in relation to rivers)

Like many ecologists, I am motivated by the heady aspiration of Saving the Planet and the less heady goal of satisfying my own curiosity. Unfortunately, I don’t quite have the powers (let alone talent) of Captain Planet, but little steps…Captain Planet

Examples 

I was recently involved in a project that developed and trialed a river health monitoring strategy and an environmental flows assessment protocol for three major rivers in China (the Gui, Taizi and Yellow). Funded by AusAid’s Australia-China Environment Development Program, the project was led by the International Water Centre in conjunction with the Chinese Ministry of Water Resources and Ministry of Environmental Protection. (reports listed in Publications)

I’m currently working on projects that relate to ecosystem resilience and novel ecosystems with Rachel Standish and Richard Hobbs, conservation strategies under climate change with Joslin Moore and effective ways to manage Bitou Bush invasion with David Lindenmayer, Richard Hobbs and Yvonne Buckley.

Catford, J.A., Naiman, R.J., Chambers, L.E., Roberts, J., Douglas, M.M. & Davies, P.M. (in press) “Predicting novel riparian ecosystems in a changing climate” Ecosystems. Online. pdf

Catford, J.A., Downes, B.J., Gippel, C.J. & Vesk, P.A. (2011) Flow regulation reduces native plant cover and facilitates exotic invasion in riparian wetlands. Journal of Applied Ecology 48: 432-442. pdf

Driscoll, D. & Catford, J. (2014) Invasive plants: New pasture plants pose weed risk.Nature 516: 37. link pdf

Driscoll, D.A.,  Catford, J.A., Barney, J.N., Hulme, P.E., Inderjit, Martin, T.G., Pauchard, A., Pyšek, P., Richardson, D.M., Riley, S. & Visser, V. (2014) New pasture plants intensify invasive species risk. Proceedings of the National Academy of Sciences of the USA 111: 16622-16627abstract pdf video Featured in Nature as a Research Highlight.