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Led by a visiting doctoral student at the University of Tartu, a solution was found for assessing which species can survive in a new habitat.
An international research team, which included University of Tartu’s visiting doctoral student Wen-Gang Zhang and Professor of Botany Meelis Pärtel, has found a new solution to one of ecology’s long-standing controversies —Darwin’s naturalization conundrum, which addresses the question of why some species successfully establish in a new habitat while others do not.
In the 19th century, Charles Darwin proposed two opposing predictions. According to one, a species arriving in a new environment has a greater chance of surviving if it is closely related to local species and thus has similar environmental requirements. According to the other, species with more distant kinship should actually be more successful, as they utilize different resources and do not compete as intensely with local species. Ecologists have debated for more than 160 years when does one explanation apply and when the other.
Now, researchers have found that the answer to Darwin’s conundrum lies in dark diversity, a term which refers to species that could potentially inhabit a given location but do not actually occur there. Together with the present species, dark diversity constitutes the species pool of the study area—in other words, all species for which the habitat conditions are, in principle, suitable. It also allows for an assessment of community completeness, which indicates what proportion of the potential species pool the ecosystem under study actually contains.
According to Meelis Pärtel, the study utilized an exceptionally rich model system. „We had access to a 340-year dataset from Swedish lakes, which includes both successful and unsuccessful fish introductions. Such data allowed with rare precision for the study of the factors that determine whether species successfully establish.“
The results showed that in lakes that were suitable for fewer species but where a larger proportion of the species that could live there were actually present, species similar to local species proved more successful. In lakes that were suitable habitats for more species but where a smaller proportion of those species were actually present, however, species that utilized resources different from those of the local species proved to be more successful.
Thus, the solution to Darwin’s paradox depends on how many species could theoretically live in the region and what proportion of them actually occur there. Importantly, the mere number of present species did not reveal such relationships, but rather, it was the species pool and community completeness, as assessed using dark diversity, that proved decisive.
„The study showed that dark diversity offers a new theoretical framework for understanding species distribution and community formation. This helps reconcile previously conflicting results and improve predictions about which species will be able to establish under new conditions,“ said professor Pärtel. „As climate change, shifts in species ranges, and human activity increasingly shape the world’s biodiversity, dark diversity offers a new way to assess how ecosystems respond to these changes. This can help better guide conservation efforts and predict changes in biodiversity in a rapidly changing world.“
This article was sent to us by the University of Tartu.
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