Combined effects of bird extinctions and introductions in oceanic islands: decreased functional diversity despite increased species richness

  • Articles in SCI Journals
  • Sep, 2022

Soares, F.C., Lima, R.F., Palmeirim, J.M., Cardoso, P. & Rodrigues, A.S.L. (2022) Combined effects of bird extinctions and introductions in oceanic islands: decreased functional diversity despite increased species richness.

Global Ecology and Biogeography, 31(6), 1172-1183. DOI:10.1111/geb.13494 (IF2020 7,144; Q1 Ecology)
Summary:
Aim

We analyse the consequences of species extinctions and introductions on the functional diversity and composition of island bird assemblages. Specifically, we ask if introduced species have compensated the functional loss resulting from species extinctions.

Location

Seventy-four oceanic islands (> 100 km2) in the Atlantic, Pacific and Indian Oceans.

Time period

Late Holocene.

Major taxa studied

Terrestrial and freshwater bird species.

Methods

We compiled a species list per island (extinct and extant, native and introduced), and then compiled traits per species. We used single-trait analyses to assess the effects of past species extinctions and introductions on functional composition. Then, we used probabilistic hypervolumes in trait space to calculate functional richness and evenness of original versus present avifaunas of each island (and net change), and to estimate how functionally unique are extinct and introduced species on each island.

Results

The net effects of extinctions and introductions were: an increase in average species richness per island (alpha diversity), yet a decline in diversity across all islands (gamma diversity); an average increase in the prevalence of most functional traits, yet an average decline in functional richness and evenness, associated with the fact that extinct species were functionally more unique (when compared to extant natives) than introduced species.

Main conclusions

Introduced species are on average offsetting (and even surpassing) the losses of extinct species per island in terms of species richness, and they are increasing the prevalence of most functional traits. However, they are not compensating for the loss of functional richness due to extinctions. Current island bird assemblages are becoming functionally poorer, having lost unique species and being composed of functionally more redundant species. This is likely to have cascading repercussions on the functioning of island ecosystems. We highlight that taxonomic and functional biodiversity should be assessed simultaneously to understand the global impacts of human activities.


https://onlinelibrary.wiley.com/doi/full/10.1111/geb.13494

Team

  • Combined effects of bird extinctions and introductions in oceanic islands: decreased functional diversity despite increased species richness Filipa Coutinho Soares Tropical and Mediterranean Biodiversity - TMB
  • Combined effects of bird extinctions and introductions in oceanic islands: decreased functional diversity despite increased species richness Jorge Palmeirim Tropical and Mediterranean Biodiversity - TMB
  • Combined effects of bird extinctions and introductions in oceanic islands: decreased functional diversity despite increased species richness Ricardo Faustino de Lima Tropical and Mediterranean Biodiversity - TMB