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Maron Lab

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Research

Below is a sampling of current and past reserach topics. Together they illustrate the breath of conceptual issues addressed in the Maron lab.

Food Web Ecology: Cascading Effects of Top Predators

At the simplest level, food webs describe who eats who in a community. However, beyond this description, food webs can summarize the important ecological interactions that influence the population growth and abundance of species in a community. We are interested in how top predators, through their effects on consumers, influence plant abundance, productivity and comunity organization.

Predator exclosure

In collaboration with Dr. Dean Pearson (U.S. Forest Service), we are currently conducting a long-term and large-scale manipulative experiment to determine how mid-sized mammalian carnivores (weasel, fox, coyote, badger, mountain lion, etc.) and raptors, as a group, influence herbivorous and granivorous small mammal behavior, abundance and population dynamics, and how small mammals in-turn affect plant abundance, community assembly, grassland productivity and diversity. Our goal is to quantify the strength of direct effects of predators on their prey and consumers on vegetation, and in doing so determine the strength of indirect whether predators have cascading indirect effects on terrestrial plant communities.


Ground squirrel Pred exclosuer blackfoot Badger

Our research, now in its eleventh year, takes place in spectacular native grasslands in the Blackfoot Valley of western Montana. This is one of the few locations in North America where the entire predator assemblage remains intact. Starting over a decade ago, we established replicate 1 hectare plots where we either exclude: 1) all predators and native grazers, 2) native grazers (deer and elk) only, and 3) none of these animals. Within these large plots we embedded smaller 10 m x 10 m rodent exclosures to examine rodent impacts on vegetation. We continue to monitor various components of the food web to understand how predator and/or ungulate removal influences an assemblage of small mammal consumers and in-turn determine how small mammals influence plant abuandance and plant community dynamics. Relevant publications: (Maron et al. 2010, Maron and Pearson 2011).

Predator exclosure in winterPlant communityRodent exclosure

Community Assembly

As part of this project, we are also interested in how competition from resident vegetation and generalist rodent consumers influence plant community assembly.  We are conducting a large scale seed addition experiment where we have addeed locally uncommon species to disturbed or undisturbed plots in and out of larger rodent exclosures across 10 sites in the Blackfoot Valley.  This work is quantifying the strength of dispersal limitation and local filters such as competition and seed predation in influencing the assembly and ultimate composition of local communities.  Relevant publications (Maron et al. 2012, Maron et al. 2014).

Seed addition plot1field work

Other food web research

In previous food web research, in collaboration with Drs. Jim Estes and Donald Croll (U.C. Santa Cruz), we have examined how the historic introduction of foxes onto islands in the Aleutian archipeligo has disrupted nutrient subsidies brought in my nesting seasbirds, and how this has had strong cascading indirect effects on island plant communities and productivity (relevant publications: Croll et al. 2005, Maron et al. 2006).

ak workislandsIslands2Aleutian island work

Plant-Animal Interactions

We know from a growing number of studies that interactions between plants and their consumers and mutualists can have strong impacts on plant performance and even plant fitness. Yet, quite surprisingly, we still have a very rudimentary understanding of the conditions under which these pervasive negative or positive interactions influence plant abundance or distribution. As a result, predicting the conditions under which anagonists or mutualists have important population-level impacts on plants has proved difficult. We are interested in understanding the population-level consequencs of plant-animal interactions and determining the ecological and environmental conditions that may predict when these interactions strongly or weakly influence plant distribution or abundance. Previous work has explored the impact of insect herbivory and rodent granivory on habitat specific demography and abundance of the native nitrogen-fixing shrub, bush lupine (relevent publications:Maron and Simms 2001, Maron 1998, Maron and Jefferies 1999, Maron and Gardner 2000, Maron 2001, Maron and Kauffman 2006, Kauffman and Maron 2006). Other research, has examined how rodent consumers influence plant recruitment and population size of native forb species in Montana (relevent publications: Bricker et al. 2010, Bricker and Maron 2012).

Lupine landscapeGhost moth

Role of biotic interactions in affecting plant range limits

While it has long been appreciated that abiotic conditions play a strong role in affecting the geographic distribution of species, how biotic interactions, alone or in concert with the abiotic environment, influence range boundaries remains surprisingly understudied.  We are interested in how range-wide spatial variation in the abiotic environment interacts with spatial variation in biotic interactions (particularly insect herbivores and pollinators) to influence range boundaries and differences in population size across the range.  Current work, spearheaded by Ph.D. student Katie Baer, is examining limits to the geographic range boundaries of the native forb, Astragalus utahensis.  

Invasion Biology

Biological invasions offer unique opportunities to understand fundamental issues in ecology and evolution (Callaway and Maron 2006).  Biological invasions are essentially large-scale “natural experiments” that provide insight into key issues such as population regulation, community assembly, niche partitioning, and the interplay between plasticity and rapid evolutionary change in allowing species to colonize new areas.  Our interests in invasion biology center on three major issues. First, we are interested in how attributes of recipient communities influence community invasibility and invader impact.  We have explored how native plant diversity influences invasibility and invader impact, how invasibility and impact differ among invaders, and how impact scales with invader abundance (relevant publications: Maron and Marler 2007, 2008a, 2008b).   As part of this work, we have also shown the important role of soil pathogens in driving the common positive relationship between plant diversity and productivity (Maron et al. 2011). 

Diversity plotsdiversity plots2

More recently we have also examined the role of generalist rodent consumers in providing biotic resistance to invasion (Pearson et al. 2011, 2012). 

clearwater rodent exclosureTrago

Second, using biogeographical approaches, we are interested in determining the factors that enable a small subset of exotics to go from being relatively uncommon where they are native to occurring in virtual monocultures in recipient communities.  In  collaboration with Dr. Ray Callaway (University of Montana), we have explored whether altered interactions with plant competitors contributes to invasive success of spotted knapweed (Centaurea stoebe; relevent publications:  Callaway et al. 2011, 2012, Maron et al. 2013).   Other work, in collaboration with Drs. Callaway and J. Klironomos explores whether biogegraphical differences in the suppressive effects of soil biota  contribute to invasion success.

Finally, we are interested in the role of rapid evolutionary change in allowing exotics to adapt to new ecological circumstances.   In previous research (a collaboration with Dr. Montse Vila, Estación Biológica de Doñana (EBD-CSIC), Spain), we combined genetic data on invasion history with common garden experiments in the native and introduced range to quantify the evolutionary response of introduced genotypes of the invasive forb, St. John’s Wort (Hypericum perforatum), to new climatic conditions within the introduced range (relevenat publications: .  Publications from this work can be found here (Vila et al. 2003, Maron et al. 2004a, 2004b, Vila et al. 2005, Maron 2006, Maron et al. 2007, Seifert et al. 2009, Molins et al. 2014).

Other Interests

While the major thrust of my research centers on the issues discussed above, I have been involved in a variety of collaborative projects that span a diverse conceptual areas in population and community ecology. These projects have explored how spatial processes influence insect outbreaks (Maron et al. 2001), plant defense (Karban and Maron 2002, Karban et al. 2003, Agrawal et al.  2013), the role of climate change in affecting species interactions and avian community organization (Martin and Maron 2012), eco-evolutionary feedbacks between plants and consumers (Agrawal et al. 2012).

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