Professor Frithjof Lutscher works the interface between mathematics and biology. His research focuses on mechanistic models for ecological systems, in particular on population persistence and spread in fragmented landscapes. The Canadian Applied and Industrial Mathematics Society (CAIMS) presented the 2022 CAIMS Research Prize to Prof. Lutscher, in recognition of his outstanding contributions to mathematical ecology. Awarded annually, the CAIMS Research Prize is the most prestigious award granted by CAIMS and the only award in Canada that recognizes contributions to applied mathematics.
Together with many students and colleagues over the course of more than 10 years, Prof. Lutscher developed a new framework for modelling population dynamics in strongly heterogeneous environments. This framework integrates births and deaths of individuals as well as their movement behaviour and preference for certain habitat types to make predictions about whether a population can persist and spread regionally. It greatly increases the applicability of previous models that did not consider landscape heterogeneity and habitat preference, yet it remains simple enough to yield analytical results on, say, how the speed of spatial spread of an invasive species depends on landscape characteristics (such as the distribution of their preferred resource).
A tangible example of how Prof. Lutscher’s framework has been used to model population dynamics is the Emerald ash borer. Originally from Asia, this invasive insect arrived in Canada in 2002 and could decimate 85% of all ash trees. One suggestion to stop this invasion included the felling of thousands of ash trees in the hope that the insect would die out when it did not find suitable locations to lay its eggs. Prof. Lutscher showed that this approach could lead to an unexpected increase in the invasion speed! The decrease in population due to fewer eggs laid could be more than compensated for by the increase in distance covered in search of favourable habitat. Protecting existing trees, for example by using an existing “vaccine”, would provide a better strategy since it does not alter the movement behaviour of the insects.
While we wish to avoid the spread of some species, there are others, such as the Baltimore Checkerspot butterfly, that we want to help spread. Landscape fragmentation and climate change threaten this species’ survival. Northward migration could help the species reach more suitable areas in terms of temperature patterns. Prof. Lutscher’s work shows that interspersing high- and low-quality habitat can lead to higher spread rates than high-quality habitat by itself. In fact, for the Checkerspot butterfly, around 15% of high-quality habitat leads to the fastest spread rates. This is encouraging because this amount of high-quality habitat seems achievable whereas 100% of high-quality habitat is in many cases impossible.
The impacts of Prof. Lutscher’s framework has not only generated new and exciting mathematical theory but can be felt in ecological theory and in conservation and invasion biology with new methods to estimate the spread of invasive species, something that affects all Canadians.
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