Research

I use observational, experimental, meta-analytical and theoretical approaches to address a suite of inter-related questions:


How does the disruption of mutualisms influence plant communities?

My research program has focused on the multiple effects of the disruption of plant-seed disperser mutualisms by both human activities such as habitat fragmentation, as well as the spread of invasive species. In previous work, I studied the effects of habitat disturbance and fragmentation on dispersal mutualisms and found that fragmentation leads to the extinction of a seed disperser causing the extinction of a keystone plant within these habitat fragments (Rodriguez-Cabal et al. 2007). For my PhD dissertation research, I have focused on the effects of exotic insects (ants and wasps) and vertebrates (ungulates) on mutualisms in North America and in the temperate forests of South America. Several plant species rely on ants for seed dispersal but these mutualisms are highly susceptible to be disrupted by the invasion of exotic ants. I used a meta-analytical approach to study the effect of a single, globally disperser invasive ant species (the argentine ant, Linepithema humile) on ant-plant seed dispersal mutualisms. I found that this exotic ant disrupted seed dispersal mutualisms by displacing native ant seed dispersers while failing to effectively disperse seeds itself (Rodriguez-Cabal et al. 2009). Additionally, I conducted field experiment to study the effect of invasive Asian needle ant (Pachycondyla chinensis) on the ant-seed dispersal mutualisms in the eastern deciduous forest of USA. I was the first to find that this exotic invasive ant negatively affected seed dispersal by displacing a proposed keystone ant these deciduous forests (Rodriguez-Cabal et al. 2012).


Cascading effects: what are the indirect effects of the disruption of mutualisms?

For my PhD I also investigated the node-by-node disassembly of a mutualistic interactions web driven by the losses of native and the gain of exotic species. Interaction webs summarize the diverse interactions among species in communities. The addition or extinction of particular species and the alteration of key interactions can lead to the disassembly of the entire interaction web, though, the non-trophic effects of species loss on interaction webs are poorly understood. I took advantage of ongoing invasions by a suite of exotic species in Patagonia to examine the mechanisms and consequences of the node-by-node disassembly of highly co-evolved interaction web. I found that the reduction of one species (a host of a keystone mistletoe) resulted in diverse indirect effects that lead to the disassembly of a mutualistic web, through the loss of the mistletoe, of two key seed dispersers (a marsupial and a bird) and a pollinator (hummingbird) (Rodriguez-Cabal et al. 2013). My results demonstrate that the gains and losses of species are both consequences and drivers of global change that can lead to under-appreciated cascading co-extinctions. Taken together, my findings demonstrate the importance of viewing biodiversity not only as the sum of different components but also the direct and indirect interactions among them.

 

Genes to ecosystems 


A ‘genes-to-ecosystems’ approach to ecology has sought to understand the importance of genetic variation from genes to phenotypes to community structure and ecosystem function. For example, different plant genotypes can have strong effects on the population dynamics of associated arthropods. Moreover, differences in plant genotypes can influence both above- and below-ground ecosystem processes such as primary productivity, litter quality, decomposition rates, and nutrient cycling (Crutsinger, Rodriguez-Cabal, et al. 2013). I seek to understand genetic variation within species, patterns of diversity within communities and how ecosystem function. Lately, we have started exploring the influence of genetic diversity across ecosystem boundaries (Rudman, Rodriguez-Cabal, et al. 2015; Rodriguez-Cabal, et al. 2017)

Warming and Removal in Mountains (WaRM)

Rising temperatures associated with climate change is a major global political and socio-economical priority. The amount of carbon in the atmosphere regulates how much warming will occur globally, but the amount of carbon taken up and released from terrestrial ecosystems under warming remains uncertain in the models that predict future climates. Warming has a range of direct (e.g. changes in process rates) and indirect (shifts in dominant plant species, plant-soil interactions) effects on ecosystem properties and processes. In WaRM we study community and ecosystem responses to the direct and indirect effects of warming in a coordinated project that combines experimental warming and dominant plant species removal at high and low elevations among 12 globally-distributed gradients. We have five overarching objectives with this network: (1) To determine the relative influences of climate and interactions among species on biodiversity and ecosystem carbon dynamics. (2) To examine the patterns and processes that shape ecosystem function among disparate ecosystems. (3) To investigate whether the functional composition of plant communities determines how communities respond to warming and dominant species removal. (4) To assess whether functional traits can be used to improve predictions of how ecosystem function and community structure change in response to climate and climate change. (5) To leverage the results of these experiments to improve a community land model to refine predictions about global carbon cycling.

Within this network M. Noelia Barrios-Garcia and I work is largely focused on running the Patagonia site in Argentina.

CollaboratorsMaja Sundqvist (Umeå University), Aimee Classen (University of Vermont), Nate Sanders (University of Vermont), Toke Hoye (Aarhus University), David Wardle (Nanyang Technological University), Jennie McLaren (University of Texas), Thomas Crowther (Netherlands Institute for Ecology), Mark Hovenden (University of Tasmania), Julie Deslippe (University of Wellington), Jin-Sheng He (Peking University), Christian Rixen (Swiss Federal Institute for Forest, Snow and Landscape Research), John-Arvid Grytnes (University of Bergen), Sandra Lavorel (University of Grenoble)


How successful are exotic species after establishment?

I have been evaluating recent attempts to refute the tens rule (about 10% of all introduced species establish and about 10% of these established species become invasive) of two relatively very well-studied groups, exotic birds and mammals, and comparing these data with those from a previous study. I showed that lack of information about failed species introductions, and the tendency to report species that have become invasive more than those that have not, results in an overestimate of the establishment success and invasion rates of non-native species (Rodriguez-Cabal et al 2009; Rodriguez-Cabal et al. 2013).

 

Can positive interactions lead to the realized niche of species to be larger than its fundamental? 

I reviewed the inclusion of positive interactions in niche theory. Some studies have suggested that positive interactions can lead the realized niche of a species to be larger than its fundamental niche. In this study I made theoretical arguments about the niche concept and how it changes in response to invasive species. Specifically, I used exotic invasive species to show that although positive interactions can counteract the effects of negative interactions and possibly modify the realized niche of a species, the realized niche of a species can never be larger than the fundamental niche (Rodriguez-Cabal et al. 2012).