Research | Jonathan Newman

Book projects

Tue, 24 Jan 2012 13:35:42 -0500

Photograph © Andrew Dunn, 5 November 2004. via Wikimedia Commons. (Note: I'm not comparing my word to Newton's -- just liked the photo!)

2011

J.A. Newman, M. Anand, H.A.L. Henry, S. Hunt and Z. Gedalof Climate Change Biology. Publisher: CABI. 2011. This book was published in April 2011. Climate change has moved from a contested phenomenon to the top of the agenda at global summits.Climate Change Biologyis the first major textbook to address the critical issue of how climate change may affect life on the planet, and particularly its impact on human populations. Presented in three parts, the first deals extensively with the physical evidence of climate change and various modelling efforts to predict its future. Biological responses are then addressed from the individual's physiology to populations and ecosystems, and further to considering adaptation and evolution. The final section examines the specific impact climate change may have on natural resources, particularly as these relate to human livelihood. The aim of this book is to provide an introduction to climate change biology and give a synthesis of progress to date. It is intended for upper level undergraduates and beginning graduate students.

Aphids and climate change

Tue, 24 Jan 2012 13:30:03 -0500

Video by Nick Gould, Hort Research, Ruakura New Zealand

Both endophytic fungi, and climate change seem to alter the interactions between herbivores and their host plants. To-date, most research has tended to characterize the impacts of both endophytic fungi and climate change, in terms of the changes that they induce to the whole plant or whole leaf. However, many herbivores, including aphids, don't actually eat the whole leaf. Aphids are sap sucking insects. To understand aphid responses to these forces, we ideally would like to characterize what is in the phloem sap, as distinct from what is in the whole leaf.

One way to sample phloem sap from a grass plant is to excise a tiller and suspend the tiller so that the sap drains from it. In this case, EDTA is used to help keep the sap from from coagulating. The problem with this approach is that you not only get phloem sap, but everything else too. An alternative that has been around since the late 1970s, but has been little adopted do to the technical difficulties, is the 'styletectomy'. With this technique, an aphid is allowed to feed on a plant. Once committed phloem ingestion begins, a high frequency microcautery is used to sever the aphid's stylet. The stylet remains in the phloem, exuding phloem sap for several hours. Over this time the sap is collected and can then be analyzed for nutrients and/or defense compounds.

Assessing biofuel grasses for invasiveness

Tue, 24 Jan 2012 13:26:07 -0500

Photo: David Brinicombe [CC-BY-SA-2.0 (www.creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons.

Several perennial grass species are under consideration for large-scale bioenergy production in Ontario and elsewhere, including Miscanthus x giganteus, Miscanthus sinensis, Panicum virgatum, and Phalaris arundinacea. Introduction of these species may have deleterious effects on native biodiversity, if viable pollen, seeds, or vegetative fragments are allowed to escape from production fields. Therefore, it is important to investigate the potential invasiveness and community impacts of these species prior to introducing them on large scales for bioenergy production. First, we will compile a database of known invasive populations in Ontario. These populations will be visited and compared with uninvaded surrounding vegetation to quantify local impacts to native seedbank biodiversity. Second, we will perform a weed risk assessment (WRA) for the perennial bioenergy grasses being considered for Ontario. In addition, we will conduct a controlled experiment in an old-field remnant in which we will test the effects of biofuel species identity and planting density on native plant abundance and diversity. Finally, we will monitor the field margins of the bioenergy plots to quantify the rate of vegetative spread for M. sinensis, M. x giganteus and M. sacchariflorus. These activities will advance our understanding of the potential invasiveness, impacts, and sustainability of bioenergy grasses, and will help guide selective breeding programs and bioenergy policy for Ontario.

Spatial scale and the effects of biodiversity on ecosystem function

Tue, 24 Jan 2012 13:01:41 -0500

In grassland communities it is well established that a number of ecosystem functions are correlated with plant species richness. One particularly well documented result has been termed ‘over-yielding’ and occurs when the biomass produced by a species mixture is greater than the average of the biomass produced by each species grown as a monoculture. This result is usually attributed to ‘complementarity’ between species. That is, species use different resources and so the more species present, the more total resources get used and hence the greater the total biomass production. My former postdoc, Kathryn Yurkonis, and I hypothesized that this result relies on very fine-grained species mixtures, perhaps at spatial grains smaller than are often observed in natural grassland communities. We further hypothesized that the impact of an invasive species would similarly be greater, the finer the spatial grain of the species mixture (because the finer the grain, the greater the opportunity for inter-specific competition). To test these hypotheses, we established, in the summer of 2010, a large-scale replicated field study. We established 28 4 x 4 m plots. Each plot has 16 species, 15 native to Ontario tallgrass prairies, and an invasive species, E+ tall fescue. There are 7 replicates of four spatial grains. The plants were established by filling the 4 x 4 m plots with: 16 (1 x 1 m) monocultures, 32 (½ x ½ m) monocultures, 64 (¼ x ¼ m) monocultures, or with all of the seed finely intermixed. In all cases the total amount of seed for each of the 16 species was kept constant. Over the next five years, we will monitor: total biomass production to examine the degree of over-yielding; invasion by non-experimental species; and the degree of dominance by tall fescue and rate of change of species composition.

Herbivore responses to climate change

Wed, 18 Jan 2012 10:20:21 -0500

Figure from: E.A. Robinson*, G.D. Ryan* & J.A. Newman (2012). Tansley Review: A meta-analytical review of the effects of elevated CO2 on plant-arthropod interactions highlights the importance of interacting environmental and biological variables. The New Phytologist, in press. *Co-first authorship.

This is a broad theme in my lab, and we have used five different approaches:

1. Field and Lab Experiments: My PhD student, Emily Robinson, and I are currently working on the bean leaf beetle and how rising temperatures may alter over winter survival. However the mainstay of my experimental work in this field has been the bird cherry-oat aphid and it's responses to rising CO2 concentrations. My most recent work on this subject has been with my PhD student, Gerry Ryan, where we have been trying to link changes in plant host quality brought on by rising levels of CO2 to changes in aphid population dynamics. Papers relating to this area can be found here.

2. Physiologically-based mechanistic models: This model comprises four sub-models. The plant sub-model respond mechanistically to changes in CO2, temperature, water availability, soil nitrogen, relative humidity, and photosynthetically active radiation. There are also simple soil and water sub-models, and a more extensive aphid sub-model. The aphid model is linked to the plant sub-model through the nutritional quality of the phloem sap. We have also looked at a couple of examples of tri-trophic interactions by adding aphid predators and parasitoids. Papers relating to this area can be found here.

Endophytic fungi and plant biochemical pathways

Wed, 18 Jan 2012 10:16:12 -0500

The relationship between cool-season grasses and fungal endophytes is widely regarded as mutualistic, but there is growing uncertainty about whether changes in resource supply and environment benefit both organisms to a similar extent. In this work, we have been artificially infecting perennial ryegrass (Lolium perenne) cultivars that differ in carbohydrate content, with different strains of Neotyphodium lolii (AR1, AR37, common strain) that differ intrinsically in alkaloid profile. We grow endophyte-free and infected plants under high and low nitrogen (N) supply and use quantitative PCR (qPCR) to estimate endophyte concentrations in harvested leaf tissues.

So far we have found that endophyte concentration is reduced by 40% under high N supply, and by 50% in the higher sugar cultivar. These two effects seem to be additive (together resulting in 75% reduction). Alkaloid production is also reduced under both increased N supply and high sugar cultivar, and for three of the four alkaloids quantified, concentrations were linearly related to endophyte concentration.

Endophytic fungi and climate change

Wed, 18 Jan 2012 10:05:57 -0500

Endophytes are a group of fungi that live inside of plants. I study two particular species: Neotyphodium lolii and N. coenophialum. These fungi infect perennial ryegrass and tall fescue respectively. The Neotyphodium species have been refereed to as "trapped parasites". The live asexually entirely within the host plant. They spread only vegetatively via tillering or through the seeds of infected plants. There is no known route of horizontal transmission of the fungus from infected to uninfected grass plants. Because these fungi are trapped within their host, it is thought that the relationship between plant and fungi has evolved away from parasitism and toward mutualism.

We have shown that the presence of the endophyte moderates the plants' responses to elevated CO2. One common plant response to elevated CO2 is a reduction in plant protein. We have shown in both grass species that this reduction is not as great in plants infected with the endophyte than for endophyte-free plants. Another common response of grasses to elevated CO2 is an increase in plant carbohydrate (CHO). Again, we have shown that the presence of the endophyte moderates this repsonse. Endophyte-infected individuals show less accumulation of CHO than endophyte-free plants. In addition to CHO and protein, another common response is a reduction in chlorophyll content under high CO2. We have found that this reduction is much less in endophyte-infected plants.