Periodic Reporting for period 1 - HELICITY (HELICITY: Evolution of correlated traits in response to city life: helicid snails as windows on the consequences of urban history)
Période du rapport: 2021-06-01 au 2023-05-31
Urbanization is one of the most dramatic land-use changes caused by humans, combining habitat fragmentation and loss, pollutions and increased temperature. While it causes numerous population declines in many species, others persist or even thrive in cities, possibly through evolutionary changes. In this project, the Researcher will study how urbanization shapes multivariate phenotypic evolution in such an organism, including not only life-history traits, movement strategies/space use… but their association into integrated phenotypes. As a central point, they will explicitly consider the oft-neglected temporal heterogeneity of the urbanization process, comparing new and older urban neighbourhoods to see under which conditions organisms can adapt to city life fast enough. Using snails as models, this Action will combine advances in small animal tracking, statistical analysis and data science with state-of-the-art evolutionary ecology, to not only explore the mechanisms behind observed changes, but also potential consequences for relevant aspects of ecosystem functioning. This project will increase our understanding of the ecological consequences of evolution in response to human-caused environmental changes, helping fill major knowledge gaps noted by the IPBES. Through outreach, it will increase community engagement with (urban) biodiversity.
The main objectives of HELICITY are:
• Understanding how urban history systematically improves our understanding of urban evolution and more broadly phenotypic changes
• Quantifying The (genetic) trait axes of least resistance for urban evolution
• Understanding how evolutionary responses predict ecosystem functioning shifts in cities
• Showing how/whether embracing the complexity of urbanisation improves our understanding of urban evolution
The main objectives of HELICITY are:
• Understanding how urban history systematically improves our understanding of urban evolution and more broadly phenotypic changes
• Quantifying The (genetic) trait axes of least resistance for urban evolution
• Understanding how evolutionary responses predict ecosystem functioning shifts in cities
• Showing how/whether embracing the complexity of urbanisation improves our understanding of urban evolution
Following fieldwork across the Flanders and Brussels regions of Belgium, the following main results were achieved in the project:
We provided major evidence of trait changes in responses to urbanisation in land molluscs, an understudied taxon in urban ecology. In particular, we found evidence that city life leads to smaller body sizes and faster heart/metabolic rates, both being key traits with major ecological implications. We showed however that responses were not correlated across traits, meaning that urban phenotypic changes do not occur along any "axis of least resistance" and may be much more flexible, at least in this species.
By combining information on historical levels of urbanisation, analyses of present urbanisation at multiple spatial scales and common garden experiments in lab conditions, we found evidence that most phenotypic variation we observed between traits (with the possible exception of heart rate and colour) was not evolutionary but plastic.
Snail population densities were largely independent from urbanisation, indicating that the focal snails are highly tolerant from human presence, but also importantly that changes in snail-related ecosystem functioning would be driven by phenotypic traits, not abundance changes.
Finally, we showed that snails parasitic burden varied substantially between populations, and that some snail-parasite interactions varied with urbanisation.
We provided major evidence of trait changes in responses to urbanisation in land molluscs, an understudied taxon in urban ecology. In particular, we found evidence that city life leads to smaller body sizes and faster heart/metabolic rates, both being key traits with major ecological implications. We showed however that responses were not correlated across traits, meaning that urban phenotypic changes do not occur along any "axis of least resistance" and may be much more flexible, at least in this species.
By combining information on historical levels of urbanisation, analyses of present urbanisation at multiple spatial scales and common garden experiments in lab conditions, we found evidence that most phenotypic variation we observed between traits (with the possible exception of heart rate and colour) was not evolutionary but plastic.
Snail population densities were largely independent from urbanisation, indicating that the focal snails are highly tolerant from human presence, but also importantly that changes in snail-related ecosystem functioning would be driven by phenotypic traits, not abundance changes.
Finally, we showed that snails parasitic burden varied substantially between populations, and that some snail-parasite interactions varied with urbanisation.
The project provided what is to our knowledge the first evidence that historical land use data older than the 20th century could be used to understand phenotypic responses to city life.
This project is also the first multi-city and multi-trait study of urban phenotypic changes in any land mollusc, despite the fact that land molluscs are both a highly diverse taxon and common in cities.
HELICITY also shows that measuring changes in population abundances is not enough to quantify changes in ecosystem functions in cities, and that detailed phenotypic measurements will often be needed despite the added cost.
We provide the first evidence that the prevalence of nematodes trapped in snail shells (a recently described defence mechanism) varies non-randomly between populations, including between urban and non-urban populations, in a way that can be used for ecological studies and comparisons.
We also provide the first evidence that snails may use their shell to trap not only nematode parasites, but also trematodes.
Through the HELICITY project, we also developed methods to accurately estimate snail heart rates in non-invasive way, and improved methods for the automated tracking of snail movements in lab settings, increasing the usefulness of land snails as models in (urban) ecology, evolution and ethology.
Finally, we expect that analysis of shell colour data will provide new valuable information on the quantitative genetics of shell colour, as little is known so far on how plasticity and genetics shape shell colour variation outside to one model genus with much simpler colour variation.
This project is also the first multi-city and multi-trait study of urban phenotypic changes in any land mollusc, despite the fact that land molluscs are both a highly diverse taxon and common in cities.
HELICITY also shows that measuring changes in population abundances is not enough to quantify changes in ecosystem functions in cities, and that detailed phenotypic measurements will often be needed despite the added cost.
We provide the first evidence that the prevalence of nematodes trapped in snail shells (a recently described defence mechanism) varies non-randomly between populations, including between urban and non-urban populations, in a way that can be used for ecological studies and comparisons.
We also provide the first evidence that snails may use their shell to trap not only nematode parasites, but also trematodes.
Through the HELICITY project, we also developed methods to accurately estimate snail heart rates in non-invasive way, and improved methods for the automated tracking of snail movements in lab settings, increasing the usefulness of land snails as models in (urban) ecology, evolution and ethology.
Finally, we expect that analysis of shell colour data will provide new valuable information on the quantitative genetics of shell colour, as little is known so far on how plasticity and genetics shape shell colour variation outside to one model genus with much simpler colour variation.