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How does biodiversity affect species interactions

Biodiversity brings to mind coral reefs or dense tropical forests. In each of these environments, there are a large number of species with a lot of interactions between them. These animals cooperate to watch for predators, prey on each other, and parasitize one another. Fishes hide among corals and monkeys climb trees – and both may eat from their shelters.  

Species interactions and biodiversity seem to increase together, and previous studies suggest that the two are interdependent. However, the question of how species interactions are impacted by biodiversity has not been thoroughly investigated.

Now, a new study from Kyoto University shows that although biodiversity increases with species interactions, the strength of these interactions decreases.

The strength of interactions among species can be measured in many different ways, with each technique yielding a different answer. Interaction strength is often used to predict stability and robustness within an ecosystem.   

“The total interaction strength experienced by a single species is a limiting factor, resulting in weakened interspecific interactions in a high-diversity community,” said study lead author Masayuki Ushio.

He suggested that the interaction capacity hypothesis can be used to explain this phenomenon. This theory suggests that biodiversity and network connectance are driven by the sum of interaction strength that an individual species gives and receives. Connectance is the number of interaction links between two species compared to the potential links. 

“This phenomenon can provide mechanistic explanations for many observed ecological patterns in nature,” said Ushio.

To test this hypothesis, the researchers constructed interaction networks using DNA that was collected from the environment of 1,197 species found on experimental rice plots. The data was then mathematically modeled to test the hypothesis.   

The results of the analysis suggest that community diversity, interaction capacity and connectance are dependent on each other. 

“Our meta-analysis of datasets on biodiversity suggests that the interaction capacity hypothesis might be applicable to a wide range of taxa and ecosystems,” concluded Ushio.

By Zach Fitzner, Staff Writer

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