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July 27, 2010
10:11 AM
66 views

Enhanced biodiversity-ecosystem function relationships in polluted systems

by Marc Cadotte in The EEB and flow

*note: this text was adapted from an Editor's Choice I wrote for the Journal of Applied Ecology.In this era of species loss and habitat degradation, understanding the link between biodiversity and functioning of species assemblages is a critically important area of research. Two decades of research has shown that communities with more species or functional types results in higher levels of ecosystem functioning, such as nutrient processing rates, carbon sequestration and productivity, among others. This research has typically used controlled experiments that standardize environmental influences and manipulate species diversity. However, a number of people have hypothesized that biodiversity may be even more important for the maintenance of ecosystem functioning during times of environmental stress or change rather than under stable, controlled conditions. It is during these times of environmental change that preserving ecological function is most important, as changes in function can have cascading effects on other trophic levels, compounding environmental stress. Therefore, explicitly testing how biodiversity affects function under environmental stress can help to inform management decisions. Image from Wikimedia commonsIn a recent paper in the Journal of Applied Ecology, Li and colleagues examine how algal biodiversity influences productivity in microcosms with differing cadmium concentrations. Cadmium (Cd) is a heavy metal used in a number of products and industrial processes, but it is toxic and Cd pollution is a concern for human populations and biological systems, especially aquatic communities. This is especially true in nations currently undergoing massive industrial expansion. In response to concerns about Cd pollution effects on aquatic productivity, Li et al. used algal assemblages from single species monocultures to eight species polycultures grown under a Cd-free control and two concentrations of Cd, and measured algal biomass. Their results revealed that there was only a weak biodiversity-biomass relationship in the Cd-free teatment, which the authors ascribed to negative interactions offsetting positive niche partitioning. In particular, those species that were most productive in their monocultures were the most suppressed in polycultures. However, in microcosms with Cd present there were positive relationships between diversity and biomass. They attribute this to a reduction in the strength of competitive interactions and the opportunity for highly productive species to persist in the communities. While a plethora of experiments generally find increased ecosystem function with greater diversity, Li et al.’s research indicates that the effect of biodiversity on function may be even more important in polluted systems. If this result can be duplicated in other systems, then this gives added pressure for management strategies to maintain maximal diversity as insurance against an uncertain future.Li, J., Duan, H., Li, S., Kuang, J., Zeng, Y., & Shu, W. (2010). Cadmium pollution triggers a positive biodiversity-productivity relationship: evidence from a laboratory microcosm experiment Journal of Applied Ecology, 47 (4), 890-898 DOI: 10.1111/j.1365-2664.2010.01818.x... Read more »

Li, J., Duan, H., Li, S., Kuang, J., Zeng, Y., & Shu, W. (2010) Cadmium pollution triggers a positive biodiversity-productivity relationship: evidence from a laboratory microcosm experiment. Journal of Applied Ecology, 47(4), 890-898. DOI: 10.1111/j.1365-2664.2010.01818.x

July 7, 2010
11:02 AM
88 views

Organic farming and natural enemy evenness

by Marc Cadotte in The EEB and flow

The basic reality of agricultural activity is that it reduces biological diversity, and these reductions in diversity potentially impact ecosystem services. But do some agricultural practices impact these services less than others? In a recent paper in Nature by David Crowder and colleagues, the question of how organic versus conventional farming affects predator and herbivore pathogen diversity and how this cascades to pest suppression. They show through a meta-analysis, that organic farms tend to support greater natural enemy evenness, and they hypothesize that greater evenness of enemies should better control pest populations, resulting in larger, more productive plants.Picture from wikipediaThis result in itself is interesting, but they also carried out an elegant enclosure experiment where they manipulate the evenness of insect predators and pathogens and measure potato plant size. They found that even communities had the lowest herbivore densities and saw the greatest increases in plant biomass. Conversely, very uneven communities, typical of conventional farms, had the largest pest populations resulting in lower plant biomass accumulation.While, multiple farming strategies are needed for adequate agricultural production, there are strong arguments for organic farms to be a important part of agricultural practice. These results show that organic farms have cascading effects on pest predators and pathogens and show that enemy evenness, as opposed to richness, has important ecosystem service consequences. To quote myself, evenness is a critical component of biodiversity, and much research has emphasized species richness, maybe at the detriment of studying evenness.Crowder, D., Northfield, T., Strand, M., & Snyder, W. (2010). Organic agriculture promotes evenness and natural pest control Nature, 466 (7302), 109-112 DOI: 10.1038/nature09183... Read more »

Crowder, D., Northfield, T., Strand, M., & Snyder, W. (2010) Organic agriculture promotes evenness and natural pest control. Nature, 466(7302), 109-112. DOI: 10.1038/nature09183

June 1, 2010
10:00 PM
136 views

Experimental test of Darwin's naturalization hypothesis

by Marc Cadotte in The EEB and flow

Among the numerous and still informative ecological predictions made by Darwin, one posits that when species are introduced into regions where they were not formerly found, the most successful tend to not have close relatives already occupying the region. This is known as Darwin's Naturalization Hypothesis, and his logic was that among close relatives, where ecological requirements should be most similar, the struggle for existence is most severe. Thus the modern formulation is that invader success is influenced by the amount of time since two species shared a common ancestor (usually called phylogenetic distance). Tests of this hypothesis have been primarily done on large species inventories, with results from different studies either supporting or refuting it. In a new study by Lin Jiang and colleagues published in the American Naturalist, they cleverly use bacteria with known relatedness to test this hypothesis.They used four species of bacteria: Bacillus pumilus, B. cereus, Frigoribacterium sp. and Serratia marcescens as residents in every possible 1, 2, 3 and 4-species communities and invaded them with a subspecies of S. marcescens. What they found was that the invader density was highly significantly related to phylogenetic distance, so that the invader reached its greatest density when communities contained only distantly-related species.Though these types of laboratory experiments are simplistic (I too use these systems), they offer insights into particular mechanisms, which may otherwise be difficult to detect in noisier systems.Jiang, L., Tan, J., & Pu, Z. (2010). An Experimental Test of Darwin’s Naturalization Hypothesis The American Naturalist, 175 (4), 415-423 DOI: 10.1086/650720... Read more »

Jiang, L., Tan, J., & Pu, Z. (2010) An Experimental Test of Darwin’s Naturalization Hypothesis. The American Naturalist, 175(4), 415-423. DOI: 10.1086/650720

May 11, 2010
09:37 AM
152 views

Picante's coming out party

by Marc Cadotte in The EEB and flow

This past decade has seen a rapid expansion of the use of evolutionary phylogenies in ecological studies. This expansion is largely due to the increased availability of phylogenies, but has resulted in new types of hypotheses and statistics aimed to test the phylogenetic patterns underpinning ecological communities. The main computational tool used has been phylocom, created by Cam Webb, David Ackerly and Steve Kembel, which has its own binaries to be installed on one’s computer. However, a new R package, picante has been created by Steve Kembel and colleagues which runs many of the same routines as in phylocom, but in the R framework, allowing one to tie these analyses in better with other, non-phylogenetic tests. Picante also has a number of features and tests not found in phylocom, including tests of phylobetadiversity and phylogenetic signal using Blomberg’s K.

Thanks Steve for all your hard work and for making these tests available to everyone.

Kembel, S., Cowan, P., Helmus, M., Cornwell, W., Morlon, H., Ackerly, D., Blomberg, S., & Webb, C. (2010). Picante: R tools for integrating phylogenies and ecology Bioinformatics DOI: 10.1093/bioinformatics/btq166
... Read more »

Kembel, S., Cowan, P., Helmus, M., Cornwell, W., Morlon, H., Ackerly, D., Blomberg, S., & Webb, C. (2010) Picante: R tools for integrating phylogenies and ecology. Bioinformatics. DOI: 10.1093/bioinformatics/btq166

April 14, 2010
01:28 PM
225 views

Teaching a quoll that cane toads are bad

by Marc Cadotte in The EEB and flow

Often, species become endangered because of multiple stressors, with habitat destruction taking the prize as the most egregious. However, often what pushes a species into extinction is not the main driver of endangerment. For example, passenger pigeon numbers were decimated by unabated hunting, but the proximate cause of extinction was likely an inability to thrive in low densities. Yet, seldom is the case where a known single species interaction is the primary cause of engangerment and maybe extinction. The northern quoll, Dasyurus hallucatus, is an endangered marsupial predator in Australia. The current major threat to the northern quoll is the invasion of toxic can toads. Quolls, being predators of small mammals, birds, reptiles and amphibians, readily attacks cane toads, which are toxic to quolls. Quoll populations have disappeared from areas invaded by cane toads, and extinction seems almost inevitable.Given that the spread of cane toads into the remaining quoll habitats is inevitable, research, led by Stephanie O'donnell in Richard Shine's lab at the University of Sydney and published in the Journal of Applied Ecology, is underway to train quoll's to avoid cane toads. These researchers feed a subset of captive quolls dead toads laced with thiabendazole, a chemical that induces nausea. They then fitted individuals with radio collars and released these toad-smart quolls as well as toad naive ones. Some toad-naive quolls died quickly, after attacking cane toads. Only 58% of male naive quolls survived, while 88% of toad-smart males survived. While females seemed less likely to attack toads, 84% of naive females survived and 94% of toad-smart females survived!See the video of a toad-smart quoll deciding not to eat a cane toad, its pretty cool.O’Donnell, S., Webb, J., & Shine, R. (2010). Conditioned taste aversion enhances the survival of an endangered predator imperilled by a toxic invader Journal of Applied Ecology DOI: 10.1111/j.1365-2664.2010.01802.x... Read more »

O’Donnell, S., Webb, J., & Shine, R. (2010) Conditioned taste aversion enhances the survival of an endangered predator imperilled by a toxic invader. Journal of Applied Ecology. DOI: 10.1111/j.1365-2664.2010.01802.x

April 8, 2010
10:26 PM
223 views

Plant rarity: environemtal or dispersal limited?

by Marc Cadotte in The EEB and flow

In order to promote the persistence and possible spread of extremely rare plant species, ecologists need to know why a species is rare in the first place. In 1986, Deborah Rabinowitz identified seven forms of rarity, where rarity could mean several things depending on range size, habitat specificity and population sizes. When considering rarity, it often feels intuitive to look for environmental causes for these different forms of rarity. Habitat alteration is an obvious environmental change that affects abundance and distribution, but are rare species generally limited by habitat or resource availability? The alternative cause of rarity could just be that sufficient habitat exists, but that the rare species is simply unable to find or disperse to other sites. An extreme example of this would be the Devil's Hole pupfish which exists at only a single pool. It can survive elsewhere (such as in artificial tanks) but natural dispersal is impossible as its pool is in a desert.Photo taken by Kristian Peters and available through GNU free documentation licenseIn a recent paper by Birgit Seifert and Markus Fischer in Biological Conservation, they examine whether an endangered plant, Armeria maritima subsp. elongata, was limited because of a lack of habitats or if it was dispersal limited. They collected seeds from eight populations and experimentally added these seeds to their original populations and to uninhabited, but apparently appropriate sites. They found that seeds germinated equally well in inhabited and uninhabited sites and seedlings had similar survivorships. They found that variation in germination rates were likely caused by originating population size and that low genetic diversity and inbreeding reduce viability.These results reinforce two things. First is that conserving species may only require specific activities, such as collect and distributing seeds. Here ideas like assisted migration seem like valuable conservation strategies. Secondly, we really need to be doing these simple experiments to better understand why species are rare. If we fail to understand the causes of rarity, we may be wasting valuable resources when try to protect rare species.Seifert, B., & Fischer, M. (2010). Experimental establishment of a declining dry-grassland flagship species in relation to seed origin and target environment Biological Conservation DOI: 10.1016/j.biocon.2010.02.028... Read more »

Seifert, B., & Fischer, M. (2010) Experimental establishment of a declining dry-grassland flagship species in relation to seed origin and target environment. Biological Conservation. DOI: 10.1016/j.biocon.2010.02.028

March 22, 2010
09:25 PM
232 views

Predicting endangered carnivores: the role of environment, space and phylogeny

by Marc Cadotte in The EEB and flow

For conservation biology, there are several research thrusts that are of critical importance, and one of these is to find predictors of species' extinction risk. Oft-cited is the particular susceptibility of large-bodied organisms, with their large ranges and slow reproductive rates. But there should be other predictors too, especially within larger mammals. In a forthcoming paper in Global Ecology and Biogeography, Safi and Pettorelli use just a few variables to predict extinction risk in carnivores.They quantified species extinction risk according to the IUCN risk assessments and asked how well three attributes explained variation in extinction risk. They quantified the environmental characteristics of the species' ranges (temperature, precipitation, etc.), spatial distances between species' ranges and the phylogenetic distances among species. Overall, spatial and phylogenetic distances were good predictors of threat status -generally predicting between 21-70% of variation in extinction risk, whereas the environmental variables were weaker predictors. Full models incorporating all three variables (and accounting for their covariance), were able to explain upwards of 96% of the variation in extinction risk!Although these variables do not represent causal mechanisms of extinction risk -rather they are correlative, they do provide conservation biologists with a rapid assessment tool to evaluate extinction risk. These tools should be particularly important in cases were population data are lacking and immediate pragmatic decisions are required.Safi, K., & Pettorelli, N. (2010). Phylogenetic, spatial and environmental components of extinction risk in carnivores Global Ecology and Biogeography DOI: 10.1111/j.1466-8238.2010.00523.x... Read more »

Safi, K., & Pettorelli, N. (2010) Phylogenetic, spatial and environmental components of extinction risk in carnivores. Global Ecology and Biogeography. DOI: 10.1111/j.1466-8238.2010.00523.x

March 9, 2010
09:44 AM
253 views

Ecology and industry: bridging the gap between economics and the environment

by Marc Cadotte in The EEB and flow

Applied ecology is the science of minimizing human impacts and of supporting ecological systems in an economic landscape. Often though, applied ecologists work in isolation from those economic forces shaping biological landscapes, not really knowing what businesses would like to accomplish for habitat protection or sustainability. At the same businesses are seldom aware of the knowledge, tools and insight provided by ecologists. And perhaps, greater interaction could help turn ecology into a science with direct impact into how human activities proceed and how we manage the impacts of those activities.This is the premise of a paper by Paul Armsworth and 15 other authors on the ecological research needs of business, appearing in the Journal of Applied Ecology (for an interview with Paul, by yours truly, please go to the podcast, and I should point out that I am an Editor with this journal). The authors include academics, NGOs and industrial representatives, and they've come together to analyze patterns of cooperation and to discuss ways forward.They reviewed papers appearing in the top applied ecology journals and grant proposals to the National Environmental Research Council (NERC) in the UK to measure the degree and type of interaction between ecologists and different industries. Ten to 15 percent of publications in applied journals showed some business involvement -mostly from the traditional biological resource industries (farming, fishing and forestry). Further, 35% of NERC proposals included some business engagement, but only 1% had direct business interaction.Further, the authors reported on a workshop where ecologists and business representatives discussed a number of topics. This included how to minimize negative biodiversity impacts and for industries, such as mining, to consider ecosystem function, and how to develop new ecologically-based economic opportunities, such as insurers managing environmental risk. While there were some challenges identified (such as differing time frames of business needs versus scientific research), the authors note the positive atmosphere and the spirit of collaboration.The research in this paper should be emulated elsewhere. A better understanding of business needs and desires can only inform and offer opportunities for applied ecological research. Top-down governmental regulation can only take conservation and ecosystem management so far and those who are directly involved in altering and managing ecosystems must articulate goals and desires in order to successfully apply ecological principles to biodiversity protection in an economic landscape.Armsworth, P., Armsworth, A., Compton, N., Cottle, P., Davies, I., Emmett, B., Fandrich, V., Foote, M., Gaston, K., Gardiner, P., Hess, T., Hopkins, J., Horsley, N., Leaver, N., Maynard, T., & Shannon, D. (2010). The ecological research needs of business Journal of Applied Ecology, 47 (2), 235-243 DOI: 10.1111/j.1365-2664.2010.01792.x... Read more »

Armsworth, P., Armsworth, A., Compton, N., Cottle, P., Davies, I., Emmett, B., Fandrich, V., Foote, M., Gaston, K., Gardiner, P.... (2010) The ecological research needs of business. Journal of Applied Ecology, 47(2), 235-243. DOI: 10.1111/j.1365-2664.2010.01792.x

February 22, 2010
06:30 PM
260 views

How can evolution inform conservation decisions?

by Marc Cadotte in The EEB and flow

First of all, let me apologize for the lack of blog posts over the past 2 weeks, I've been busy visiting the Olympics and reading a couple of hundred blog, judging them for the Research Blogging awards.

The conservation of biological diversity is a major imperative for biologists. International agreements such as the Convention on Biological Diversity and intergovernmental exercises, such as the Millennium Ecosystem Assessment, call upon scientists to provide evidence on the current state of biological diversity and to evaluate solutions for reducing diversity and ecosystem function loss. Critical to these efforts have been the work of ecologists, conservation biologists and ecological economists. However, seemingly missing from the conversation about the state of biodiversity knowledge has been evolutionary biologists. Are they primarily concerned with describing historical processes and mechanisms of biological change, or do they have substantive knowledge and ideas that should be viewed as a critical component of any scheme to conserve biological diversity?

In a recent paper in Evolution, Hendry and a number of coauthors convincingly make the case that evolutionary biology is a necessary component for conservation. Evolution offer four key insights that should inform conservation and policy decisions. First, they point out that evolutionary biologists are in the business of discovering and documenting biodiversity. They are the primary drivers behind long-term, sustained biological collections, because they need to know what exists in order to better understand evolutionary history. With millions of species awaiting scientific discovery, their efforts are critical to measuring biodiversity. But not only are they discovering new species and enumerating them, they are uncovering their evolutionary relationships, which gives conservationists better information about which species to prioritize. What Vane-Wright famously called 'the agony of choice', with limited resources, we need to prioritize some species over others, and their evolutionary uniqueness ought to be a factor. More than this, evolutionary biologists have developed pragmatic tools for inventorying and sharing data on biodiversity at all levels, from genes to species, which is available for prioritization.

The second key insight is that by understanding the causes of diversification, we can better understand and predict diversity responses to environmental and climatic change. By understanding how key functional traits evolve, we can develop predictions about which species or groups of species can tolerate certain perturbations. Further, research into how and why certain evolutionary groups faced extinction can help us respond to the current extinction crisis. For example, the evolutionary correspondence between coevolved mutualists, such as plants and pollinators, can be used to assess the potential for cascading extinctions. These types of analyses can help identify those groups of related species, or those possessing some trait, which make species more susceptible to extinction.
Normal 0 0 1 355 1779 UTSC 36 4 2490 10.265 0 0 0 Thirdly, evolution allows for an understanding of the potential responses to human disturbance. Evolutionary change is a critical part of ecological dynamics, and as environment change can result in reduced fitness, smaller population sizes and extinction, evolution offers an adaptive response to these negative impacts. Knowing when and how populations can evolve is crucial. Evolutionary change is a product of genetic variation, immigration, population size and stochasticity, and if the ability to evolve to environmental change is key for persistence, then these evolutionary processes are also key. Finally, evolutionary patterns and processes have important implications for ecosystem services and economic and human well-being. Both genetic and evolutionary diversity of plant communities has been shown to affect arthropod diversity, primary productivity (including work by me) and nutrient dynamics. Thus understanding how changes in diversity affect ecosystem processes should consider evolutionary processes. Further, exotic species are often cited as one of the major threats to biodiversity, and evolutionary change in exotics has been shown to increase exotic impacts on native species.
All together, these key reasons why evolution matters for conservation, mean that developing sound management plans requires considering evolution patterns and processes. We can use evolution to our benefit only if we understand how evolution shapes current dynamics. The challenge to evolutionary biologists is the same as it was for ecologists perhaps 15 to 20 years ago, to present their understanding and conservation ideas to a broader audience and to engage policy makers. To this end, the authors highlight some recent advances in incorporating evolutionary views into existing biodiversity and conservation programmes –most notably into DIVERSITAS.
Just like ecological processes and dynamics cannot be fully understood without appreciating evolution ancestry or dynamics, developing an extensive, expansive conservation strategies must take into account evolution. I hope that this paper signals a new era of a synthesis between ecology and evolution, which produces precise, viable conservation strategies. ... Read more »

Hendry, A., Lohmann, L., Conti, E., Cracraft, J., Crandall, K., Faith, D., HÃ¤user, C., Joly, C., Kogure, K., Larigauderie, A.... (2010) EVOLUTIONARY BIOLOGY IN BIODIVERSITY SCIENCE, CONSERVATION, AND POLICY: A CALL TO ACTION. Evolution. DOI: 10.1111/j.1558-5646.2010.00947.x

February 3, 2010
09:38 PM
334 views

The evolution of a symbiont

by Marc Cadotte in The EEB and flow

The evolution of negative interactions seems like a logical consequence of natural selection. Organisms compete for resources or view one another as a resource, thus finding ways to more efficiently find and consume prey. However, to me, the natural selection of symbiotic or mutualistic interactions has never seemed as straight forward (expect maybe the case where one species provides protection for the other, such as in ant-plant mutualisms). A specific example is the rise of nitrogen-fixing plants, who supply nutrients to bacteria called rhizobia capable of converting atmospheric nitrogen into forms, such as ammonia, usable to the plant host. Not only has this symbiosis evolved, but has seemed to evolve in very evolutionarily distinct lineages. The question is, what are the mechanisms allowing for this?In a recent paper, Marchetti and colleagues answer part of the question. They experimentally manipulate a pathogenic bacteria and observe it turning into a symbiont. They transferred a plasmid from the symbiotic nitrogen fixing Cupriavidus taiwanensis into Ralstonia solanacearum and infected Mimosa roots with it. Plasmid transfer among distinct bacteria species is common and referred to horizontal genetic transfer (as opposed to vertical, which is the transfer to daughter cells). The presence of the plasmid caused R. solanacearum to quickly evolve into a root-nodulating symbiont. Two regulatory genes lost function, and this caused R. solanacearum to form nodules and to impregnate Mimosa root cells.This extremely novel experiment reveals how horizontal gene transfer can supply the impetus for rapid evolution from being a pathogen to a symbiont. More importantly it reveals that sometimes just a few steps are required for this transition and how distantly-related bacterial species can acquire symbiotic behaviors.Marchetti, M., Capela, D., Glew, M., Cruveiller, S., Chane-Woon-Ming, B., Gris, C., Timmers, T., Poinsot, V., Gilbert, L., Heeb, P., Médigue, C., Batut, J., & Masson-Boivin, C. (2010). Experimental Evolution of a Plant Pathogen into a Legume Symbiont PLoS Biology, 8 (1) DOI: 10.1371/journal.pbio.1000280... Read more »

Marchetti, M., Capela, D., Glew, M., Cruveiller, S., Chane-Woon-Ming, B., Gris, C., Timmers, T., Poinsot, V., Gilbert, L., Heeb, P.... (2010) Experimental Evolution of a Plant Pathogen into a Legume Symbiont. PLoS Biology, 8(1). DOI: 10.1371/journal.pbio.1000280

January 19, 2010
09:47 PM
235 views

Timing is everything: global warming and the timing of species interactions

by Marc Cadotte in The EEB and flow

While an obvious affect of climate change will be changes in the distributions or range sizes of species, more insidious and likely more consequential will be how species interactions are affected by changes in the timing of growth and reproduction. These changes in an organism's life cycle, or phenology, can create mismatches between an organism's need and resource availability or the readiness of coevolved partners -such as plants and pollinators.In an 'Idea and Perspective' paper in Ecology Letters, Louie Yang and Volker Rudolf set out a new framework to examine the effects of phenological shifts on species interactions. They argue that one cannot understand or predict the fitness consequences of a phenology shift without knowing how interacting species' phenologies are also influenced by environmental changes. The consequences of phenological shifts are changes in fitness, and the question is: how would one go about assessing the fitness effects of phenological changes on interactions? This is where this paper really hits its stride. Yang and Rudolf set out a new conceptual framework for studying the fitness consequences of phenological shifts. They make the case that an experimental approach is required to test the three likely scenarios. The first is that there are no changes in phenology -that is, measuring the fitness levels of the two interacting species under stable conditions. Second, you induce an experimental shift in the timing of one of the species. For example, in a plant-herbivore interaction, germinate the plant earlier and when the herbivore normally has access to the plant, the plant will be older. What are the fitness changes associated with this shift? Finally, you can shift the timing of the other species relative to the first. In our example, the herbivore has access to younger plants and again are there fitness consequences?Yang and Rudolf call the full combination of possible fitness effects, across a number of timing mismatches, 'the ontogeny-phenology landscape'. By mapping fitness changes across this ontogeny-phenology landscape, researchers can offer better predictions, on top of just changes in range size or habitat use, about the possible affects of climate change. The obvious question, and Yang and Rudolf acknowledge this, is how to extend two-species ontogeny-phenology to multi-species communities. Of course, extending two-species interactions to communities is a question that plagues most of community ecology, but I think the solution is that researchers who know their systems often have intuition about the major players, and thus those species where phenology shifts should have disproportionate effects on other species. Such species could be the place to start. Another strategy would be a food web type approach, where species are lumped into broader trophic groups and we ask how shifts in certain trophic groups affect other groups.Regardless of how to extend this framework to multispecies assemblages, I see this paper as likely to be very influential. It gives researches a new focus and framework, where specific predictions about climate change can be made.Yang, L., & Rudolf, V. (2010). Phenology, ontogeny and the effects of climate change on the timing of species interactions Ecology Letters, 13 (1), 1-10 DOI: 10.1111/j.1461-0248.2009.01402.x... Read more »

Yang, L., & Rudolf, V. (2010) Phenology, ontogeny and the effects of climate change on the timing of species interactions. Ecology Letters, 13(1), 1-10. DOI: 10.1111/j.1461-0248.2009.01402.x

January 14, 2010
10:28 PM
361 views

Plant genotypic diversity supports pollinator diversity

by Marc Cadotte in The EEB and flow

Research over the past 20 years has shown that plant communities with greater diversity maintain higher productivity, greater stability and support more diverse arthropod assemblages. More recently, several experiments have shown that interspecific diversity (namely genotypic differences) also affects community functioning. Pollination is often considered an essential function, and does plant genotypic diversity affect pollinator diversity and frequency?In a recent paper in PLoS ONE, Genung and colleagues test whether plant genotypic diversity affects pollinator visits. They use an experimental system set-up by Greg Crutsinger that combines multiple genotypes of the goldenrod, Solidago altissima, and record pollinator visits over two years. Experimental plots contained 1, 3, 6, or 12 genotypes of S. altissima. After accounting for differences in abundance, Genung et al. show that as genotypic diversity increases, both pollinator richness and number of visits to the plot significantly increase. This increase is greater than expectations of randomly simulated assemblages combining proportional pollinator visits from monocultures.The previous research at the species-level has made a persuasive rationale to protect species diversity in order to maintain ecosystem functioning. Now, research like this is making a case that there are consequences for not explicitly considering genetic diversity in conservation planning and habitat restoration.Genung, M., Lessard, J., Brown, C., Bunn, W., Cregger, M., Reynolds, W., Felker-Quinn, E., Stevenson, M., Hartley, A., Crutsinger, G., Schweitzer, J., & Bailey, J. (2010). Non-Additive Effects of Genotypic Diversity Increase Floral Abundance and Abundance of Floral Visitors PLoS ONE, 5 (1) DOI: 10.1371/journal.pone.0008711... Read more »

Genung, M., Lessard, J., Brown, C., Bunn, W., Cregger, M., Reynolds, W., Felker-Quinn, E., Stevenson, M., Hartley, A., Crutsinger, G.... (2010) Non-Additive Effects of Genotypic Diversity Increase Floral Abundance and Abundance of Floral Visitors. PLoS ONE, 5(1). DOI: 10.1371/journal.pone.0008711

January 5, 2010
12:50 PM
313 views

Predicting invader success requires integrating ecological and land use patterns.

by Marc Cadotte in The EEB and flow

Disclaimer, this was modified from an editorial I wrote for the Journal of Applied Ecology.In the quest to understand species invasions, we often try to link the abundance and distribution of invaders to underlying ecological processes. For example, oft-studied are the links between exotic diversity and native richness or environmental heterogeneity. Seemingly independently, research into how specific land use or management activities affect invasion dynamics is also fairly common. While both research strategies are of fundamental importance, not often recognized, or at least explicitly studied, is that both ecological patterns and management activities simultaneously affect invasion success. Thus a truly integrative approach to understanding invader success must take into account variation in ecological communities and abiotic resource avalibility as well as land use patterns at multiple spatial scales. Such an approach is necessary if ecologists wish to predict potential invader abundance, spread and impact.Diez et al. Examine how environmental and management heterogeneity interact to influence patterns of Hieracium pilosella (Asteraceae) inasions in the South Island of New Zealand. The spread of H. Pilosella in New Zealand is threatening native habitats (tussock fields) and the livestock grazing industry. Diez et al. Asked how environmental and management regimes affect H. Pilosella abundance and distribution across six large farms on the South Island. This is an interesting and important question, not just because they are examining how human-caused and ecological variation interact to affect H. Pilosella dynamics, but also because these sources are heterogeneity are realized at different spatial scales.Diez et al. show that the abundance and distribution of H. Pilosella was significantly affected by the interaction of habitat type (i.e., short vs. tall tussocks) and farm management strategies (i.e., fertilization and grazing rates). At larger scales, H. Pilosella was more abundant in tall tussock habitats and was unaffected by fertilization, while in short tussocks, it was less abundant in fertilized patches. At small scales, H. Pilosella was less likely to be found in short tussocks with high exotic grass cover and high productivity (measured as site soil moisture and solar radiation). Conversely, in tall tussocks, H. Pilosella was more likely to be found on sites with high natural productivity. Diez et al. were able to tease these complex causal mechanism apart by using Bayesian multilevel linear models, for which they included example R code in an online appendix.While it is a truism in ecology to say that heterogeneity affects ecological patterns, this paper deserves mention because they convincingly show that the spread of noxious exotic plants in a complex landscape, can potentially predicted by understanding the invader success in different habitat types and land management strategies. In their case they show how human activities, which were not designed to affect H. Pilosella, can strongly affect abundance in different habitat types. This type of approach to understanding invader dynamics can potentially arm managers with the ability to use existing land use strategies to predict how and where further invader targeting would be most useful.Diez, J., Buckley, H., Case, B., Harsch, M., Sciligo, A., Wangen, S., & Duncan, R. (2009). Interacting effects of management and environmental variability at multiple scales on invasive species distributions Journal of Applied Ecology DOI: 10.1111/j.1365-2664.2009.01725.x... Read more »

Diez, J., Buckley, H., Case, B., Harsch, M., Sciligo, A., Wangen, S., & Duncan, R. (2009) Interacting effects of management and environmental variability at multiple scales on invasive species distributions. Journal of Applied Ecology. DOI: 10.1111/j.1365-2664.2009.01725.x

December 16, 2009
09:51 PM
384 views

Parastie competition enhances host survival

by Marc Cadotte in The EEB and flow

Contracting a parasite is bad. But is getting colonized by multiple parasitic species worse? This is an interesting and important question. The host is a resource, which can support a limited number of parasitic individuals, and so how does competition affect parasitic species and host mortality?This was the premise of a recent paper by Oliver Balmer and colleagues, studying trypanosome infection of mice hosts. They engineered two transgeneic strains of the protozoan parasite, Trypanosoma brucei (African sleeping sickness), to fluoresce different colors in order to assess infections. They infected mice with each strain separately and together and measured host survival and parasite density.They found that when both strains were present, they competitively suppressed each other and that the level of suppression depended on the initial density of each strain. One of the strains was more virulent than the other, and infection by both strains reduced mortality by 15% compared to infection by the virulent strain only. This is due to the suppression of the virulent strain by the low virulent strain.The authors argue that strain source and intraspecific genetic diversity can have an important effect on host mortality. I would also argue that understanding interspecific interactions and within-host niche differences, would also be critical.What a cool use of molecular technology to test basic hypotheses about disease ecology.Balmer, O., Stearns, S., Schötzau, A., & Brun, R. (2009). Intraspecific competition between co-infecting parasite strains enhances host survival in African trypanosomes Ecology, 90 (12), 3367-3378 DOI: 10.1890/08-2291.1... Read more »

Balmer, O., Stearns, S., Schötzau, A., & Brun, R. (2009) Intraspecific competition between co-infecting parasite strains enhances host survival in African trypanosomes. Ecology, 90(12), 3367-3378. DOI: 10.1890/08-2291.1

November 25, 2009
10:13 PM
500 views

Taking below-ground processes seriously: plant coexistence and soil depth

by Marc Cadotte in The EEB and flow

Some of the earliest ecologists, like Eugen Warming and Christen Raunkiaer, were enthralled with the minutia of the differences in plant life forms and how these differences determined where plants lived. They realized that differences in plant growth forms corresponded to how different plants made their way in the world. Since this early era, understanding the mechanisms of plant competition is one of the most widely-studied aspects of ecology. This is such an important aspect of ecology because understanding plant coexistence allows us to understand what controls productivity in the basal trophic level for most terrestrial food webs. There are a plethora of plausible mechanisms for how plants are able to coexist, and most involve above-ground partitioning strategies (such as different leaf shapes) or phenological differences (such as germination or bolting timing). Yet, below-ground interactions among plants as a way to understand competition and coexistence have been making a strong resurgence in the literature lately. This resurgence has been driven by new hypotheses and technologies.In what is probably the best hypothesis test of the role for below-ground niche partitioning, Mathew Dornbush and Brian Wilsey reveal how soil depth can affect coexistence. They seeded 36 tallgrass prairie species into plot that were either shallow, medium or deep soiled, and asked if species richness and diversity were affected after 3 years. They found that species richness significantly increased with increased soil depth, revealing that deeper soils likely had greater niche opportunities for species. Not only did deeper soils harbor greater richness, but compositions were non-random subsets. The species inhabiting shallow soils were a subset of medium soils, and medium a subset of deep. This means that increasing depth opened new niche opportunities, unique from the ones for shallow soils.This study is the first field-based experiment of soil depth and coexistence, that I know of and the results are compelling. Plant species are segregating below-ground niches, and perhaps we look for other partitioning strategies for species that inhabit the same soil depth.Dornbush, M., & Wilsey, B. (2009). Experimental manipulation of soil depth alters species richness and co-occurrence in restored tallgrass prairie Journal of Ecology DOI: 10.1111/j.1365-2745.2009.01605.xOther notable recent papers on below-ground processes:Bartelheimer, M., Gowing, D., & Silvertown, J. (2009). Explaining hydrological niches: the decisive role of below-ground competition in two closely related species Journal of Ecology DOI: 10.1111/j.1365-2745.2009.01598.xCramer, M., van Cauter, A., & Bond, W. (2009). Growth of N-fixing African savanna species is constrained by below-ground competition with grass Journal of Ecology DOI: 10.1111/j.1365-2745.2009.01594.xMeier, C., Keyserling, K., & Bowman, W. (2009). Fine root inputs to soil reduce growth of a neighbouring plant via distinct mechanisms dependent on root carbon chemistry Journal of Ecology, 97 (5), 941-949 DOI: 10.1111/j.1365-2745.2009.01537.x... Read more »

Dornbush, M., & Wilsey, B. (2009) Experimental manipulation of soil depth alters species richness and co-occurrence in restored tallgrass prairie. Journal of Ecology. DOI: 10.1111/j.1365-2745.2009.01605.x

Bartelheimer, M., Gowing, D., & Silvertown, J. (2009) Explaining hydrological niches: the decisive role of below-ground competition in two closely related species . Journal of Ecology. DOI: 10.1111/j.1365-2745.2009.01598.x

Cramer, M., van Cauter, A., & Bond, W. (2009) Growth of N -fixing African savanna species is constrained by below-ground competition with grass . Journal of Ecology. DOI: 10.1111/j.1365-2745.2009.01594.x

Meier, C., Keyserling, K., & Bowman, W. (2009) Fine root inputs to soil reduce growth of a neighbouring plant via distinct mechanisms dependent on root carbon chemistry. Journal of Ecology, 97(5), 941-949. DOI: 10.1111/j.1365-2745.2009.01537.x

November 9, 2009
10:14 AM
401 views

Emergent linkages in seemingly unconnected food chains

by Marc Cadotte in The EEB and flow

Food webs are notoriously complex, and a difficult aspect of ecology is to offer a priori model-derived predictions of food web processes. There are some ecologists, such Neo Martinez and Jordi Bascompte, who have advanced our understanding of the general mechanisms of food web properties and dynamics through tools such as network theory. Such advanced approaches rely on direct interactions among species, or at least indirect interactions that are mediated through changes in abundance of different network players. However, what is missing from our general understanding of food web interactions is the role that behavioral responses can affect patterns of consumption and network connectivity.Washington State University ecologists, Renée Prasad and William Snyder convincingly show how behavioral responses to predation can fundamentally alter food web interactions and link previously independent predator-prey interactions. They used two spatially independent insect predator-prey links in a novel, factorially-designed experiment. The two food chains consisted of a ground-based one, where ground beetles consume fly eggs and a plant-based one, where green peach aphids feed on the plants and are consumed by lady beetles. Under the ground-based chain only, the ground-based chain plus aphids, or ground-based chain plus lady beetles, the ground beetles consume a high proportion of the fly eggs. However, when both aphids and lady beetles are present, aphids respond to lady beetles by dropping off the plants and the ground beetles switch from consuming fly eggs to aphids. Under this last treatment, very few fly eggs are consumed, fundamentally altering the strength of the linkages in the two food chains and connecting them together.This research highlights the inherent complexity in trying to understand multispecies systems, where the actors potentially have behavioral responses to other species, changing the nature of interactions. These types of responses may also generally increase the connectedness of such networks, which may result in more stable food webs, but this would need to be empirically tested. Regardless, this type of experiment offers food-for-thought to scientists trying to work general processes into a broad understanding of food web dynamics.Prasad, R., & Snyder, W. (2009). A non-trophic interaction chain links predators in different spatial niches Oecologia DOI: 10.1007/s00442-009-1486-7... Read more »

Prasad, R., & Snyder, W. (2009) A non-trophic interaction chain links predators in different spatial niches. Oecologia. DOI: 10.1007/s00442-009-1486-7

October 21, 2009
05:04 PM
446 views

Adaptation and dispersal = (mal)adapted

by Marc Cadotte in The EEB and flow

Ever since Darwin, we often think of organisms as being in a constant battle against other organisms and local environments. Thus natural selection and the resulting arms race results in organisms highly adapted to local conditions and against local antagonists. At the same time, and especially driven by theoretical advances in the 1990's, researchers began to ask how dispersal -that is, the flow of genetic material from elsewhere, can disrupt local adaptation. On the one hand it may provide genetic variation allowing for novel solutions to new difficulties. On the other hand, dispersal may reduce the prevalence of fitness-increasing genes within local populations.In a simple but elegant experiment, Jill Anderson and Monica Geber performed a reciprocal transplant experiment, moving Elliott's Blueberry plants between two habitats. One population was from highland, dryer habitats and the other from moist lowlands. They further evaluated performance in greenhouse conditions. Their results, published in Evolution, show that these two populations have not specialized to local conditions. Rather, due to asymmetric gene transfer, lowland individuals actually performed better when planted in highlands than compared to their home habitat. Further, in the greenhouse trials, lowland species did not perform better under higher moisture conditions. While genetic or physiological constraints may also limit adaptation, Anderson and Geber present a fairly convincing case that gene flow is the culprit.These results reveal that populations may actually be relatively mal-adapted to local conditions, which has numerous consequences. For example, we need to be cognizant of adaptations to particular conditions when selecting populations for use in habitat restoration and when trying to predict response to altered climatic or land-use conditions. Importantly what does this mean for multi-species coexistence? Dispersal seems to limit the ability to adapt, and thus, better use local resources or maximize fitness, making for a better competitor. At the same time, dispersal can offset high death rates, allowing for the persistence of a population that would otherwise go extinct. Understanding how these two consequences of dispersal shape populations and communities is an interesting question, and work like Anderson and Geber's provides a foundation for future studies.Anderson, J., & Geber, M. (2009). DEMOGRAPHIC SOURCE-SINK DYNAMICS RESTRICT LOCAL ADAPTATION IN ELLIOTT'S BLUEBERRY ( ) Evolution DOI: 10.1111/j.1558-5646.2009.00825.x... Read more »

Anderson, J., & Geber, M. (2009) DEMOGRAPHIC SOURCE-SINK DYNAMICS RESTRICT LOCAL ADAPTATION IN ELLIOTT'S BLUEBERRY ( ) . Evolution. DOI: 10.1111/j.1558-5646.2009.00825.x

October 7, 2009
11:38 AM
499 views

Exotic plants integrate into plant-pollinator networks

by Marc Cadotte in The EEB and flow

At almost any spot on the globe, there are species present that are not native to that locale, having been transported by human activities. Whether and how exotic species impact communities is a multifaceted problem that requires understanding the multitude of direct and indirect species interactions that occur. In a paper published in the Proceedings of the Royal Society, B, Montserrat Vila and colleagues asked if exotic plants where integrated into plant-pollinator networks, and whether this integration had any observable impacts on these networks. This is an important question, as most ecological theory predicts that plant-pollinator networks are actually quite resilient to perturbations since most associations tend to be between generalists as opposed to the more susceptible specialists.They studied invaded plant communities across Europe, observing pollinator visits to flowers in multiple 50 x 50 m plots. They calculated connectance as the number of interactions standardized by network size. They showed that exotics fully integrated into plant-pollinator networks. Exotic species accounted for 42% of all pollinator visits and 24% of all network connections -a testament to the overall abundance of exotics in many communities. However, these exotics did not affect overall changes in network connectedness, revealing that these networks are quite robust to invasions.That said, researchers must now ask if this is true in networks that do contain high numbers of specialists (e.g., orchids) or if the relative few specialists in generalist-dominated systems are more susceptible to changes from exotics.Vila, M., Bartomeus, I., Dietzsch, A., Petanidou, T., Steffan-Dewenter, I., Stout, J., & Tscheulin, T. (2009). Invasive plant integration into native plant-pollinator networks across Europe Proceedings of the Royal Society B: Biological Sciences, 276 (1674), 3887-3893 DOI: 10.1098/rspb.2009.1076... Read more »

Vila, M., Bartomeus, I., Dietzsch, A., Petanidou, T., Steffan-Dewenter, I., Stout, J., & Tscheulin, T. (2009) Invasive plant integration into native plant-pollinator networks across Europe. Proceedings of the Royal Society B: Biological Sciences, 276(1674), 3887-3893. DOI: 10.1098/rspb.2009.1076

September 25, 2009
10:09 PM
594 views

Global warming and shifts in food web strucutre

by Marc Cadotte in The EEB and flow

Predicting the effects of global warming on biological systems is of critical importance for informing proactive policy decisions. Most research so far has been on trying to predict shifts in species distributions and changes in interactions within local habitats. But what many of these studies assume is that the basic biological processes and requirements of the individual species will not change -that is their biology is fixed and they simply need to find the place that best suits them. Not so, say Mary O'Connor and colleagues, in a just-released study in PLoS Biology.O'Connor and colleagues experimentally warmed marine microcosms and tested two alternative hypotheses on food web structure: 1) that productivity increases with warming; and 2) warming increases metabolic rates, thus changing consumer-autotroph (i.e., primary producers) interactions. What they found was that warming indeed altered consumer-autotroph interactions. Warming increased base metabolic rates of consumers, as well as primary production, and the net effect was that food webs shifted towards increasing consumer control (i.e., top-down control).What this research means is that global warming may alter food web interactions by increasing resource needs of organisms as their metabolic rates increase. This may increase the stress on communities and change diversity patterns as increased needs may shift competitive hierarchies or affect autotroph's ability to withstand consumer effects.O'Connor, M., Piehler, M., Leech, D., Anton, A., & Bruno, J. (2009). Warming and Resource Availability Shift Food Web Structure and Metabolism PLoS Biology, 7 (8) DOI: 10.1371/journal.pbio.1000178... Read more »

O'Connor, M., Piehler, M., Leech, D., Anton, A., & Bruno, J. (2009) Warming and Resource Availability Shift Food Web Structure and Metabolism. PLoS Biology, 7(8). DOI: 10.1371/journal.pbio.1000178

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