Understanding the factors that determine the geographical area that a species occupies is critical to predict and manage changes to that area that may occur as a result of climate change or the appearance of an invasive species. How a species distributes itself depends on physiological constraints, physical barriers and interactions with other species; distinguishing between these factors, however, is not straightforward. But in an upcoming print edition of the journal PNAS (Proceedings of the National Academies of Sciences, USA), a team of scientists from Brazil, Australia and CIBIO – Centro de Investigação em Biodiversidade e Recursos Genéticos describes a new modeling approach that shows how interactions with other species (co-called biotic interactions) are able to explain the distribution patterns of an invasive species.
The researchers applied their approach to the cane toad (Rinella marina). Introduced to Australia in 1935 as a biological control agent for sugar cane pests, the cane toad has expanded its occupied range to include more than 1.2 million square kilometres of the continent, thus becoming a pest itself.
The researchers found that in Australia the toad expanded into areas with drier climates and more extreme temperatures. Interestingly, the same type of climate areas exist in South America, yet the toad does not colonise these regions in its native environment. The models developed by the researchers suggest that the cane toad does not occupy the full range in South America due to the presence of a closely related toad species, with which the cane toad hybridizes, establishing a biotic interaction that limits its expansion into neighbouring regions. This related species is absent in Australia, allowing the cane toad to fill its so-called fundamental niche.
The novel approach described in this study, part-funded by FCT, may be applied to any species or environment, and therefore may lead to the development of more effective species management strategies. These may involve identifying potential biocontrol agents for invasive species, or predicting the ability of native species to adapt to climate change.
CIBIO has a long-standing collaboration with Universidade Federal de Belém do Pará, in Brazil, to be strengthened soon with the official setting up of a TwinLab – the second of CIBIO’s TwinLabs, after the one in Lubango, Angola.