Maria Paniw et al.’s article ‘Demographic traits improve predictions of spatiotemporal changes in community resilience to drought‘ was one of those shortlisted for this year’s award.
My academic career began a bit unusually for most ecologists – with history. I started out studying how humans interact with nature and received my BA degree from the University of Maryland with a History Major. I was fortunate enough to travel a lot during this time and became increasingly interested in what maintains the diversity of ecosystems – many shaped in one way or another by human activities. So, I focused on ecology during my MS in Environmental Sciences at Johns Hopkins University. My fascination with how plants and animals interact with their environment and how these interactions are shifting under global change really grew when I worked on my MS thesis on invasive plants in one of Europe’s lesser known biodiversity hotspots: The Carpathian Mountains. During my PhD (Universidad de Cádiz) and first postdoc (University of Zurich), I focused largely on understanding the demographic mechanisms (changes in survival vs. growth vs. reproduction) that allow species to mitigate global-change impacts.
During these initial years of my career, I realized that population ecology has advanced tremendously in the availability of data and tools that allow us to forecast how populations will respond to global change. However, the focus still remains on a focal population, and interactions among species are still very rarely accounted for in populations forecasts. This is different in community ecology, where a strong focus is given to species interactions – unfortunately at the expense of detailed knowledge on species demography in most cases. I have therefore begun to focus my research on developing multi-species mechanistic population forecasts, borrowing from, and hopefully integrating, population and community ecology. I am intrigued by understanding which taxa are most sensitive to global-change drivers directly affecting their vital rates vs. indirectly affecting them via species interactions.
🔎About the shortlisted article
The shortlisted paper is a result of my research integrating population and community ecology. A severe episode of drought in an iconic shrubland (Doñana National Park, Spain) in 2005 marked the beginning of a long-term monitoring project of shrub resilience to extreme events. A team led by F. Lloret at CREAF, who is the senior author of our paper, has been recording how shrubs have bounced back from drought (Figure 1) and have attempted to link resilience of different patches to commonly-measured shrub functional traits. However, quite a bit of variation in resilience could not be explained by these traits. And when I joined the research group at CREAF (after my time in Zurich), I proposed a new perspective: linking resilience to demographic, or life-history, traits. And I had to good reasons to think of demography. Demographic traits describe dynamic processes of growth and tradeoffs with survival and reproduction, and capture the mechanisms that allow species to recover from a disturbance. In fact, the first important result of our work is that, although some demographic traits are correlated with functional traits, such as reproductive output (demographic) being related to seed size (functional), these correlations are not very strong overall; and so two shrub species with similar functional traits could show quite distinct combinations of demographic traits.
Our results also clearly show that components of resilience that track changes in species cover are much better explained by demographic traits than functional traits. In addition, we demonstrate that resilience changes through time and is highly contingent on the magnitude of the initial extreme event. All these results are important because attempts to link drought resilience to functional traits using snapshot views of “before-after disturbance” have often failed to predict community dynamics, and we offer a new, more dynamic perspective on how resilience measures can be improved. Importantly, we derived relatively simple demographic traits that are easily obtainable from most community-level datasets, making our work applicable to a wide range of systems.
We’ve done the first step of integrating a demographic perspective into community-level resilience. However, to get a more comprehensive picture of the dynamics of plant responses to extreme events, we need to follow individual plants through time to obtain changes in demographic traits. I am currently attempting just that in the Doñana shrub community (Figure 2) and communities of invasive species in the Carpathian Mountains. Building such integrated multi-species demographic models is challenging due to the high data requirements, but with some data integration, the results are quite exciting and show us just how much our estimates of species fates rely on an accurate picture of joint climate (or abiotic more generally) and biotic effects.
Read the full list of articles shortlisted for the 2021 Harper Prize here.