about project
Major insect declines have now been detected across the planet. Global warming is an important cause of insect declines since their body temperatures rise with temperatures in their habitat. Insects can use two quick responses as their habitat becomes too hot — escape and/or acclimatize. Yet, the two are rarely jointly studied in insects at a large scale, and we need to know if and how insects can use behaviour, physiology, or both to avoid overheating. We plan to fill this critical knowledge gap by testing two non-mutually exclusive hypotheses.
The Thermal landscape hypothesis posits that thermal variability in a landscape determines the regulation of body temperature via behaviour. The Specialist-generalist hypothesis predicts that populations in stable habitats have narrower thermal ranges and higher maximum performance. We will focus on ants, a lineage of globally distributed and ecologically important insects. We will measure microclimates experienced by ants and record their behavioral and physiological thermoregulation strategies to model and predict the composition of ant communities in a warming world. Warming in the Mediterranean region is higher than the global average, so it is pressing to understand the effects of warming on insects.
motivation
the mediterranean region
The Mediterranean region encompasses the area surrounding the Mediterranean Sea and is predominantly under the influence of a Mediterranean climate, with warm, dry summers and mild, rainy winters. Global warming is more pronounced in the Mediterranean region than in the rest of the world, making this region ideal for early documentation of organismal adaptations to temperature increases. This trend of intensified warming in the Mediterranean is particularly concerning because the region is one of the world's biodiversity hotspots, and the negative impact of global warming in this region could lead to alarming losses of biological diversity. However, this warming trend in the Mediterranean also provides an opportunity to study some of the responses of insects in already thermally stressful Mediterranean habitats, where they must cope with unprecedented thermal challenges. In Croatia, the Mediterranean region is one of three biogeographical regions, and it covers nearly 40% of the country’s total area.
- Newbold, T., Oppenheimer, P., Etard, A. & Williams, J. J. Tropical and Mediterranean biodiversity is disproportionately sensitive to land-use and climate change. Nat. Ecol. Evol. 4, 1630-1638 (2020).
- Lionello, P. & Scarascia, L. The relation between climate change in the Mediterranean region and global warming. Reg. Environ. Chang. 18, 1481-1493 (2018).
climate change
Climate change refers to long-term shifts in Earth's climate, including temperature rise, change in precipitation patterns with more frequent and severe droughts, and extreme weather events like heat waves, floods, hurricanes or snowstorms. The global warming that we currently experience is primarily driven by human activities and is occurring at an unprecedented rate. Since pre-industrial times, global temperatures have risen by more than 1°C and are projected to increase by another 1°C within the next 25 years. This rate of warming is 10 times faster than the average rate after the last ice age. The consequences of global warming are severe, including shifts in rainfall patterns, accelerated sea level rise, and more intense heatwaves. Many species will not be able to withstand the heat stress of long-term temperature increase or the heat waves, and extinction rates are expected to accelerate. Global warming is also one of the many factors contributing to insect decline, disrupting their role in nutrient cycling, pollination, pest control, and soil regeneration.
- Matthews, H. D. & Wynes, S. Current global efforts are insufficient to limit warming to 1.5°C. Science (80-. ). 376, 1404-1409 (2022).
- Meehl, G. A. & Tebaldi, C. More intense, more frequent, and longer lasting heat waves in the 21st century. Science (80-. ). 305, 994-997 (2004).
- Urban, M. C. Accelerating extinction risk from climate change. Science (80-. ). 348, 920-923 (2015).
- Wagner, D. L., Grames, E. M., Forister, M. L., Berenbaum, M. R. & Stopak, D. Insect decline in the Anthropocene: Death by a thousand cuts. Proc. Natl. Acad. Sci. 118, 1-10 (2021).
goals
Determine community level changes caused by temperature differences.
Discover how nest microclimate governs foraging decisions.
Explore the role of behavior and physiology in coping with rising temperatures.
why ants?
Ants are important
Ants are important as decomposers and scavengers. With their nest building, ants aerate the soil and enrich the soil surrounding the nests with nutrients. Ants spread the seeds of numerous plants and are food for many organisms. They are often considered ecosystem engineers because their activities can alter the environment.
Ants are globally distributed and numerous
Ants are distributed across the globe, and the only continent they do not inhabit is Antarctica. The total biomass of the global ant population exceeds the biomass of all wild mammal and bird populations combined.
Ants are diverse
The number of ant species currently exceeds 14,000, and these species display a wide range of ecological adaptations and come in various sizes. This diversity of ecological adaptations and a wide range of sizes makes ants practical as models for studying other insects.
Ant colonies can be long-lived
A single colony can live in one place for years, even decades. As such, they are excellent for monitoring long-term environmental changes.
why islands?
To study insect responses to elevated temperatures, we were looking for ecosystems that are isolated, have reduced habitat complexity, and are exposed to high temperatures. Islands fit this description perfectly — they are nearly isolated systems with very low immigration rates. There are over 1000 islands along the Croatian coast.
The Adriatic islands are located in the Mediterranean region, which is warming faster than the global average. This is concerning as the Mediterranean region is also one of the biodiversity hotspots. Therefore, it is extremely important to understand to what extent island Mediterranean insect populations are threatened by rising temperatures.
study sites
We selected the islands in the archipelagos of Brijuni National Park and Mljet National Park. These two archipelagos provide a unique opportunity to test local adaptations, given that the same ant species are exposed to different climatic conditions — cooler climates in the north and warmer climates in the south. In Brijuni National Park, we will collect ants on the islands of Galija, Mali Brijun, Vrsar, Obljak, Gaz, and Veliki Brijun. In Mljet National Park, we will study ants on the islands of Mljet, Tajnik, Glavat, Galicija, Pomeštak, and Moračnik. Each national park will also include mainland habitats as controls.
Brijuni
Mljet
metodology
1.Standardized transect sampling
2.Mapping thermal heterogeneity around the nests – drone sampling with thermal cameras
3.Test of thermal adaptations
