Research Interests: Causes
and Consequences of Biological Invasions
living in a period of Earth's history characterized by
an unprecedented mass invasion event. Plants and
animals are being rapidly shuttled from one continent
to another, using vectors and pathways created by
human travel and trade.
introduced species are unsuccessful invaders (they
fail to build sustainable populations), and many of
those that do invade have undetectable impacts, while
others can cause dramatic changes to biodiversity and
ecosystem functioning. Ecologists are searching for
ways to predict the success and impact of invaders.
Most work on
invasions has focused on terrestrial systems.
However, freshwater and coastal environments are being
invaded at exponential rates. Aquatic invasions
can degrade habitats, disrupt water supply systems,
damage fisheries, and threaten native biodiversity.
Presently, resource managers lack reliable methods to
anticipate and prioritize aquatic invasion threats.
research seeks to develop a predictive understanding
of aquatic invasions, using a combination of field
experiments, empirical modelling and
meta-analysis. I have been fortunate to work
with excellent students who have made important
contributions toward this goal. I encourage prospective students to
contact me about the possibility of working in my
lab. I supervise MSc and PhD
candidates through McGill's
Biology graduate program. We recruit new
students each year. If you are highly motivated and
committed to ecological research, then send me your CV
and a letter describing your research interests and
how they relate to our objectives:
Identify predictors of invasion success.
Some interesting research questions include: Can the
invasion success of a species be predicted from its
biological traits? In what ways do human disturbance
and propagule pressure influence the vulnerability of
aquatic habitats to invasion? How do species
interactions affect invasion success? For example,
we are exploring how phylogenetic relationships and
evolutionary experience influence the interactions
between introduced species and the communities they
encounter. Using meta-analysis on terrestrial plant
invasions, we discovered that the effect of native
herbivores on introduced plants is six times
stronger on plants that are novel genera to the
region, suggesting that the evolutionary naiveté of
introduced species to resident enemies determines
their invasion success (Ricciardi
& Ward 2006). We are now extending these
phylogenetic tests to aquatic invasions.
Test invasion theories
using aquatic communities.
Aquatic communities are valuable systems for testing
the generality of invasion models. For example,
Elton's hypothesis that species-poor communities are
more vulnerable to invasion than species-rich
communities could be tested in freshwater or marine
ecosystems. Using field experiments and meta-analysis,
we are investigating Simberloff & Von Holle's
alternative hypothesis that introduced species may
facilitate one another to cause an accelerated
accumulation of invaders and their synergistic impacts
- an "invasional meltdown". Data from the Great
Lakes (Ricciardi 2001)
suggest that facilitative interactions between
invaders are more common than antagonistic
interactions, allowing the possibility that the
invasion rate and impacts are influenced by the
invasion history of the system.
models of impact for aquatic invasions.
We are interested in predicting which invasions will
fundamentally alter fish and invertebrate communities
- e.g. why some invaders cause cascading impacts
through food webs and whether these impacts are
predictable. My lab is determining how the
impact of an invader is dependent on the composition
of the invaded community and with other environmental
conditions. For example, a synthesis of cases
studies has revealed that introduced species that
represent novel (ecologically distinct) life forms to
the invaded system pose the greatest threat to native
& Atkinson 2004). We are also studying
impacts caused by interactions between aquatic
invasions and other environmental stressors, such as
climate change and river impoundment. Recently, we
have been working with colleagues to synthesize
theories of impact in order to ultimately develop a
general theoretical framework (Ricciardi
et al. 2013).
Understand the role of
invasion in biodiversity loss.
Freshwater animals are disappearing faster than land
& Rasmussen 1999). Invasions are recognized
as a major cause of extinction, but to what extent are
invasions contributing to declines in freshwater
biodiversity in North America and across the globe?
What kinds of invaders are most likely to promote
species loss? And more problematically, how do
invasions interact with other environmental stressors
to cause extinctions? Another question that we are
exploring is how non-native species compare with
native species with respect to their potential to
undergo pest outbreaks, or to suppress native
populations. We have recently shown that non-native
predators cause greater damage to native populations
than do native predators (Paolucci et al. 2013).
assessment models for invasive species.
is supported by the following funding agencies:
We are developing risk assessment tools for
predicting the impacts of invasive species on native
biodiversity. For example, the world's richest
diversity of freshwater mussels is found in North
America, where they are highly endangered. One
threat to their survival is the zebra mussel, which
can destroy native mussel populations through
intense biofouling (the photo shows a severely
fouled mussel from the St. Lawrence River; it is
carrying more than twice its own weight in zebra
mussels attached to its shell). Recent
evidence suggests that habitat variables such as
water chemistry determine whether native mussels can
persist in systems invaded by zebra mussels (Jokela &
Ricciardi 2008). We are building statistical
models to identify which native populations are
vulnerable to extinction and which habitats are
suitable refugia for them. Recently, we have begun
testing a new method of forecasting the impacts of
predators based on their functional responses (e.g.
Kestrup et al.
et al. 2013).