Understanding the Macroevolutionary Stability of Birds through Networks
Networks have been studied in numerous scenarios in the natural world. A recent study published in Science examined the evolutionary history of fruit-eating bird species and their interactions with seed dispersal networks in numerous regions around the world. The original paper by Gustavo Burin, Paulo R. Guimarães Jr., and Tiago B. Quental was supplemented by a Perspectives piece by Carolina Bello and Elisa Barreto. The team of researchers studied 468 bird species and 29 seed dispersal networks and found that the bird species that distribute the most to the seed dispersal networks tend to belong to lineages with higher macroevolutionary stability.
The relationship between birds and plants is mutually beneficial; birds feed on the fruits of various plants and help spread the seeds across long distances, allowing for plant reproduction and higher species diversity in different ecological communities. In the paper, the authors defined species with macroevolutionary stability as those characterized with lower extinction rates or higher speciation rates. They observed that the interaction between plants and the evolutionary success of bird species was strongest in warm, wet regions with less seasonal variations (the Amazon rainforest, for example).
The paper provides a clear example of an ecological network, in which the nodes can be defined as the bird and plant species. An edge joins two nodes if the species interact with each other – that is, if the bird consumes the fruit of the plant and if the plant’s seeds are spread by the bird. Burin et al. found that the bird species with more connections were more evolutionary stable than species with fewer interactions. Further exploration of how this network would be influenced by the rapid pace of climate change and the impending sixth mass extinction could provide insight into potential cascading extinctions and where to target conservation efforts.
Sources:
https://www.science.org/lookup/doi/10.1126/science.abf0556
https://www.science.org/lookup/doi/10.1126/science.abi8160