Climate change is accelerating (IPCC 2022), and so applies ever stronger selective pressures on biodiversity (Segan et al. 2016). Possible responses include range shifts or adaptations to new climatic conditions (Bellard et al. 2012), but there is still much uncertainty about the extent of most species' adaptive capacities and the impact of extreme climatic events.
The pine processionary is a major pest of pine trees in the Mediterranean area. It is notably one of the few species for which a clear link between recent climate change and its northward expansion has been established (Battisti et al. 2005), and as such is often considered as globally benefitting from climate change. However, recent results show a retraction of its range at the southern limit (Bourougaaoui et al. 2021), exposed to high warming (+1.4°C in Tunisia since 1901 as opposed to +1.12°C on average in the Northern hemisphere) and extreme summer temperature events (Verner et al. 2013). Thus, it is possible that the species' adaptive abilities are being challenged at the southern limit of its native range by the magnitude of observed climate change.
In this work, Bourougaaoui et al. (2022) investigate how climate change over the last 30 years has impacted the reproductive success of the pine processionary moth in Tunisia. A major methodological interest of this study is that they used data both from historical collections and from recent samplings, which raised a challenge for running a longitudinal analysis as sampling locations differed between the two periods. By applying a grouping method to local climatic data, the authors were able to define several large climatic clusters within the country, and analyze long-term data from different sites within the same clusters. They find that both fecundity and hatching rate decreased over the period, while at the same time both the average temperature increased and climate variability increased. One of the main conclusions is that recurrent episodes of extreme heat during summer might have a larger impact than the long-term increase of average temperature, which strongly echoes how the intensification of weather extremes is currently proving one of the most important dimensions of climate change.
However, a most interesting hypothesis also arises from the analysis of the differences between climatic clusters: preexisting adaptations to heat, for instance, phenological shifts that allow the most sensitive stages to develop earlier in the season before the extreme heat events are most likely to occur, might actually reduce impacts in the historically warmest areas. Thus the greatest climate vulnerability might not always stand where one expects it.
Battisti A, Stastny M, Netherer S, Robinet C, Schopf A, Roques A, Larsson S (2005) Expansion of Geographic Range in the Pine Processionary Moth Caused by Increased Winter Temperatures. Ecological Applications, 15, 2084–2096. https://doi.org/10.1890/04-1903
Bellard C, Bertelsmeier C, Leadley P, Thuiller W, Courchamp F (2012) Impacts of climate change on the future of biodiversity. Ecology Letters, 15, 365–377. https://doi.org/10.1111/j.1461-0248.2011.01736.x
Bourougaaoui A, Ben Jamâa ML, Robinet C (2021) Has North Africa turned too warm for a Mediterranean forest pest because of climate change? Climatic Change, 165, 46. https://doi.org/10.1007/s10584-021-03077-1
Bourougaaoui A, Robinet C, Jamaa MLB, Laparie M (2022) Effects of climate warming on the pine processionary moth at the southern edge of its range: a retrospective analysis on egg survival in Tunisia. bioRxiv, 2021.08.17.456665, ver. 5 peer-reviewed and recommended by Peer Community in Ecology. https://doi.org/10.1101/2021.08.17.456665
IPCC. 2022. Climate Change 2022: Impacts, Adaptation, and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press. In Press.
Segan DB, Murray KA, Watson JEM (2016) A global assessment of current and future biodiversity vulnerability to habitat loss–climate change interactions. Global Ecology and Conservation, 5, 12–21. https://doi.org/10.1016/j.gecco.2015.11.002
Verner D (2013) Tunisia in a Changing Climate : Assessment and Actions for Increased Resilience and Development. World Bank, Washington, DC. https://doi.org/10.1596/978-0-8213-9857-9
DOI or URL of the preprint: https://doi.org/10.1101/2021.08.17.456665
Version of the preprint: 3
Thank you very much for submitting a revised version of your work for recommendation in PCI Ecology. I apologize for the delay in evaluating this revision, as two of the former reviewers were not available and it took some time to find another reviewer.
Both reviewers evaluated the revision very positively and have only minor comments that should be easily addressed. Dr Iltis, who did not review the first version of the manuscript, had very interesting suggestions to improve the structure and the clarity of the manuscript, so please try to address these at best.
For my part, I am still convinced that focusing on the longitudinal analysis would be a better option for the manuscript, but I only ask you to consider all my arguments carefully before making your decision.
I am looking forward reading your final improvements on this already very good manuscript. Don’t hesitate if I can be of any help, or if you want to discuss my suggestions further.
ElodieDownload recommender's annotations
DOI or URL of the preprint: https://doi.org/10.1101/2021.08.17.456665
Version of the preprint: 2
Thank you very much for submitting your work for recommendation in PCI Ecology. Your manuscript has been evaluated by 3 reviewers and myself, and we all concur that the topic of the study is most timely, and the use of collection data is an excellent way to address issues around long-term climate change and its effect on living organisms.
The manuscript was described as well-written, scientifically sound, and likely to be of interest to a wide community of ecologists. I would be most willing to recommend this work for PCI Ecology, provided you can address the concerns raised by the different evaluators.
Please pay particular attention to the following points that appear most critical for a better :
- Use of NASA satellite data at lower scale to measure temperature variations
- Cluster definition and inclusion/exclusion of some of the data (e.g. data from Thélepte in later years)
- Analysis of time series for temperature
- Use of GLM(M)s instead of non-parametric tests
- Justification of the relevance of “length of egg masses” as a variable
Don’t hesitate to ask if any of the reviewers’ comments are unclear to you, or if I can help in any way. I sincerely hope our comments are helpful to you and contribute to improving the manuscript further.