Climate-induced range expansions of caddisflies have limited effects on ecosystem functions

Researchers from North Carolina State University have conducted a study to investigate the impact of climate-induced changes on animal distribution and their effects on ecosystem functions. The study found that resident species can continue to fulfill important ecological processes even in the presence of similar newcomer species. However, when the newcomers are more dissimilar, the role of resident species in ecosystem functioning undergoes changes.

This research has significant implications for understanding the consequences of climate change on species communities. As climate change forces new species into different habitats, such as species moving from lower to higher latitudes or elevations, predictive tools can be developed to anticipate the outcomes.

Professor Brad Taylor, co-author of the study and a professor of applied ecology at NC State, highlighted the importance of understanding the impact of species range expansions due to climate change on the existing ecosystem structure and function. In cases where resident and newcomer species are relatively similar, the consequences for ecosystem functions may not be significant.

The study focused on caddisfly populations in Colorado’s pristine ponds over a span of 30 years. The researchers assessed key ecosystem functions linked to the overall health of the ecosystem, including nitrogen and phosphorus excretion by caddisflies, as well as the speed at which caddisflies process dead plant material, known as detritus. The effects of resident and newcomer species on these processes varied depending on the composition of the community.

Changes in nitrogen and phosphorus levels can lead to alterations in the algal community, which serves as a food source for higher trophic levels such as fish or amphibians, according to Taylor.

In the study, it was found that caddisflies play a crucial role in the processing of detritus, as they consume decomposing wetland plant material and break it down into smaller fragments that can be utilized by other organisms. A high level of detritus processing indicates a well-functioning ecosystem, according to Taylor.

Over the course of 30 years, the study identified three expansions in the range of caddisfly populations. In the first two expansions, caddisfly species similar to the resident species in terms of detritus processing and nutrient dynamics entered the ponds. One of these similar newcomer species played a larger role in nitrogen supply throughout the 30-year period.

In the third expansion, a dissimilar newcomer species emerged as the dominant supplier of phosphorus. However, despite these changes in the community composition, the overall detritus processing and nutrient supply in the ecosystem remained stable. There was no evidence of declining caddisfly populations over time, although the dissimilar newcomer species is close to becoming the dominant resident species.

The study provides valuable temporal data that illustrates the potential consequences of climate-induced species introductions into new ecosystems and communities. Understanding the specific rates of nutrient supply and detritus processing by different species is essential for predicting the effects of species shifts. Nitrogen and phosphorus are crucial factors that regulate algae populations in the ponds, and changes in dominant species like caddisflies can influence the abundance of these nutrients.

Taylor emphasized the need to examine the effects of these range expansions on other invertebrates and vertebrates in the ecosystem. The researchers intend to investigate the long-term consequences of these changes and how they may impact other organisms.

As climate-induced range expansions continue to occur, the study highlights the importance of exploring and understanding the various ecosystem processes associated with these shifts. The findings contribute to our knowledge of how climate change can affect species interactions and ecosystem dynamics. The study was published in Communications Biology.

Source: North Carolina State University

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