RE-assembly and COMpetition during Biotic INterchangEs: consequences of old invasions on the evolutionary and ecological history of biotas

Project Information

RECOMBINE

Grant agreement ID: 896323

DOI

10.3030/896323

Project closed

EC signature date 17 March 2020

Start date 1 February 2021

End date 10 April 2024

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 263 827,20

EU contribution

€ 263 827,20

Coordinated by

ECOLE NORMALE SUPERIEURE
France

Periodic Reporting for period 2 - RECOMBINE (RE-assembly and COMpetition during Biotic INterchangEs: consequences of old invasions on the evolutionary and ecological history of biotas)

Reporting period: 2023-02-01 to 2024-01-31

Summary of the context and overall objectives of the project

What are the Biotic interchanges?
We are currently at a peak of Earth's biological diversity, despite recent extinctions caused by the human activities that define the Anthropocene. The Cenozoic, the current geological era, began about 66 million years ago with catastrophic events such as a large asteroid impact or major volcanic eruptions at global level, all of which were followed by significant tectonic movements, mountain liftings, and climatic oscillations. During this era, after an initial big mass extinction, many biological groups diversified rapidly, resulting in drastic changes in the composition of ecological communities.
An important factor that shaped the current distribution of global biodiversity was biotic exchanges: movements of species between different biotas. The high tectonic activity of the Cenozoic caused a reorganization of the planet's land masses, which on the one hand continued the isolation of some biotas, and on the other hand facilitated the exchange of species between biotas with independent evolutionary histories.

Why BI are important to society?
The study of biotic interchanges led to major breakthroughs in our understanding of evolution, paleontology and geography. For example, A. R. Wallace’s observation of admixtures between distinct faunas across Wallace's Line gave rise to the field of global biogeography and informed the concept of natural selection. Through the study of extinct mammals across North and South America, Simpson realised the magnitude of historical intercontinental dispersals, breaking new ground in our understanding of the evolution and ecology of extant (and extinct) faunas in the world. The study of biotic interchanges continues to have the potential to make important advances in knowledge; with an ever-increasing rate of human-mediated invasions, the study of biotic interchanges could also hold key insights for the management and conservation of biota into the future.
Despite the importance of biotic interchanges for understanding the assembly of extant biological communities, macroecological and macroevolutionary studies on biotic interchanges remain scarce.

Objectives of the project
Extensive data on evolutionary relationships and distribution of tetrapod species, through comprehensively-sampled fossil-calibrated phylogenies and big geographic distribution databases curated by experts and conservation organisations have recently been available. Paleoclimatic and tectonic reconstructions at global level have been made available as well. The methods to reconstruct ancestral biogeography, although still with lots of scope to improvement, have also reached some stability and curation in the last decade. Therefore, there is currently a unique and unprecedented opportunity to understand better the magnitude and importance of historical and contemporary biotic interchanges to explain the ecological assembly of current terrestrial vertebrate communities and how this affected their evolution and diversification.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Using the most complete phylogenetic trees and distribution databases of current terrestrial vertebrates, we run models of ancestral biogeographic estimation. These models were based on the Dispersal-Extinction Cladogenesis model, a method broadly used in historical biogeography. From the results of these, we summarise the probabilities of dispersal events between all the areas using stochastic maps and counting events through consecutive time bins of a few million years. This allows to detect the major biotic interchanges (North, Central and South America; Africa-Eurasia, India-Eurasia, Sahul-Wallacea-Eurasia) and their fluctuations through time. Furthermore, this also shows the relative importance of other dispersal events that happened less often, such as long-distance dispersals that in some cases resulted in evolutionary radiations in colonised areas.
Distance between areas seems to be important.
In general, the number of dispersal events between two land masses is asymmetric. This asymmetry is in great part driven by the different number of lineages in each source area. This can be explained by the size of each area, with big areas behaving as big sources of dispersal. When dividing the number of dispersal events by the sum of branch lengths in each source area in each time bin, the obtained rates of dispersal still show differences depending on the direction of dispersal (asymmetry) and variation through time. However the approach of measuring variation of dispersal rates between areas and through time, with a model that assumes constant and equal dispersal rates (the Dispersal-Extinction-Cladogenesis model) is not methodologically correct. We dig more into the theoretical problems and its consequences using data simulated under known dispersal parameters. A big part of the issue derives from the structure of phylogenetic trees based only on extant taxa and missing information on the past lineages.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

This reconstruction of ecologic and evolutionary historical events is the first one to look at the processes of biotic interchange at a global level across big clades. So far, most studies on this field have focused on small clades or particular regions such as the Great American Biotic Interchange, the Wallace line, the collision of India with Asia…
In general, there is strong asymmetry in the number of dispersal events between pairwise combination of areas. When correcting the dispersal events by the number of lineages present in the dispersal source areas, the obtained rates are quite symmetrical between pair of landmasses. That makes the size of the source communities (which correlates highly with area size) as the main predictor driving the asymmetry of dispersal events in biotic interchanges with distances modulating the number of observed dispersal events. The role that area and distance, the main predictors of diversity in the theory of island biogeography, seem to be as well fundamental factors in this context at continental and geological scale.
This project provides strong insights on how evolution of diversity is strongly linked to changes in the environment that happen at geological scales. It also helps understanding the long-term consequences of invasive species, by bringing the perspective of this process in a geological scale with ecological and evolutionary consequences. It also helps valuing the species that compose our present-day communities in function of their historical biographic legacies (for example whether they are the remnants of lineages that suffered considerable extinction or whether they are part of a successful evolutionary radiation with ancestors in a different continent).

Some steps of parts of the reconstruction of dispersal events of tetrapods during the Cenozoic