Structure, spatial dynamics, and stability of novel seed dispersal mutualistic networks in Hawaiʻi

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Science  05 Apr 2019:
Vol. 364, Issue 6435, pp. 78-82
DOI: 10.1126/science.aau8751

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Invasive birds spread native seeds

When humans introduce exotic species to sensitive ecosystems, invasion and extinction of native species often follow. The resulting ecological communities can develop unusual interactions between the survivors and newcomers. Vizentin-Bugoni et al. analyzed the structure of seed dispersal networks in Hawai'i, where native bird species have been mostly replaced by invaders. They found that the native plants now depend on the invasive birds for seed dispersal. The network of dispersal interactions is complex and stable, which are features of native seed-dispersal networks in other parts of the world. It appears that introduced species may, in some circumstances, become integrated into native ecosystems.

Science, this issue p. 78


Increasing rates of human-caused species invasions and extinctions may reshape communities and modify the structure, dynamics, and stability of species interactions. To investigate how such changes affect communities, we performed multiscale analyses of seed dispersal networks on Oʻahu, Hawaiʻi. Networks consisted exclusively of novel interactions, were largely dominated by introduced species, and exhibited specialized and modular structure at local and regional scales, despite high interaction dissimilarity across communities. Furthermore, the structure and stability of the novel networks were similar to native-dominated communities worldwide. Our findings suggest that shared evolutionary history is not a necessary process for the emergence of complex network structure, and interaction patterns may be highly conserved, regardless of species identity and environment. Introduced species can quickly become well integrated into novel networks, making restoration of native ecosystems more challenging than previously thought.

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