Brown, K.A., Spector, S.& Wu, W. (2008)Multi-scale analysis of species introductions:
combining landscape and demographic models to improve management
decisions about non-native species. Journal of Applied Ecology, 45,
1639–1648.
Abstract:
1.
Non-native, invasive species can affect biological patterns and processes at multiple ecological
scales. The multi-scalar effects of invasions can influence community structure, ecosystem processes
and function, and the nature and intensity of ecological interactions. Consequently, efforts to assess
the spread of invasive species may benefit from a multi-scale analytic approach.
2.
We analysed results from landscape- and population-scale models for
Syzygium jambos
, a nonnative
tree in the Luquillo Mountains of Puerto Rico, to demonstrate a multi-scale approach that
can be used to inform management decisions about invasive plants. At the landscape-level, we used
an Ecological Niche Modelling approach to predict environmentally suitable habitats for the target
plant. At the population-level, we constructed matrix projection models to determine the finite rate
of population increase (
λ
) for
S. jambos
. We then extrapolated
λ
values to the landscape-scale to
obtain a distribution map of
λ
values for the Luquillo forest.
3.
The landscape analyses suggested that the most environmentally suitable habitats were those
most similar to where
S. jambos
had already been observed. The population-level analyses showed
that four of the seven populations had
λ
values less than 1, indicating that they were projected to be
below replacement. The
λ
distribution map showed that
S. jambos
growth was highest in areas
where it was most common and lowest in areas where it was most rare.
4.
Our analyses further suggested that the importance of different drivers of invasion and the environmental
variables that mediate them appear to be strongly scale-dependent. Past disturbances
seemed most important for controlling invasions at fine-spatial scales; while abiotic environmental
variables modulated coarse-scale invasion dynamics.
5.
Synthesis and applications.
We have shown that a multi-scale analytic approach can be used to
manage invasive species by simultaneously targeting susceptible life stages and rapidly growing
populations in a landscape. The utility of this approach stems from an ability to: (i) map the
distribution of habitats that can potentially sustain
λ
values above replacement; (ii) identify
populations to manage or monitor during selected stages of an invasion; (iii) forecast the probability
for a target species to increase above a critical threshold abundance; and (iv) set priorities for control
and monitoring actions.