Stegodon SEA-crossing: Swim, shrink, and disperse

Dispersal of terrestrial mammals into Wallacea requires the crossing of sea straits. Stegodons, an extinct family of proboscideans, managed to settle on roughly a dozen Wallacean islands during the Pleistocene. Their distribution pattern is, however, not well understood. It results from the interact...

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Main Authors: Christine Hertler, Alexandra A.E. van der Geer, Mika Rizki Puspaningrum, Jan-Olaf Reschke, Iwan Pramesti Anwar, Ericson Hölzchen
Format: Article
Language:English
Published: Elsevier 2025-06-01
Series:Earth History and Biodiversity
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Online Access:http://www.sciencedirect.com/science/article/pii/S2950475925000103
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author Christine Hertler
Alexandra A.E. van der Geer
Mika Rizki Puspaningrum
Jan-Olaf Reschke
Iwan Pramesti Anwar
Ericson Hölzchen
author_facet Christine Hertler
Alexandra A.E. van der Geer
Mika Rizki Puspaningrum
Jan-Olaf Reschke
Iwan Pramesti Anwar
Ericson Hölzchen
author_sort Christine Hertler
collection DOAJ
description Dispersal of terrestrial mammals into Wallacea requires the crossing of sea straits. Stegodons, an extinct family of proboscideans, managed to settle on roughly a dozen Wallacean islands during the Pleistocene. Their distribution pattern is, however, not well understood. It results from the interaction of two specific processes, namely respective swimming performances on the one hand, as well as island dwarfing on the other. Reduction of body mass has an impact on swimming performance, because smaller size leads to a slower swimming speed and lower deposits of available energy. In this study we conducted a series of experiments with the agent-based model SEAcross, designed to monitor swimming performances of terrestrial mammals across sea straits by measuring crossing success rates (CSR). We found that the dispersal pattern is in accordance with size-dependent swimming performances, geographic width as well as current speed and direction. Because currents change on a seasonal scale, bottlenecks decelerating or even preventing dispersal are rarely absolute, but should be considered as seasonal phenomena. Our results allow for an in-depth analysis of dispersal routes and success. Dispersal performances cannot, however, explain the lack of a fossil record of stegodons in the eastern part of Wallacea. With very few exceptions, routes should be manageable for terrestrial mammals with the size of a stegodon. Our results illustrate, however, the usefulness and applicability of agent-based models in order to further examine geographic dispersal barriers in conjunction with the dynamics of animal behavior.
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spelling doaj-art-07e9bb0b51eb42d78243eb152dda250d2025-08-20T02:06:27ZengElsevierEarth History and Biodiversity2950-47592025-06-01410002610.1016/j.hisbio.2025.100026Stegodon SEA-crossing: Swim, shrink, and disperseChristine Hertler0Alexandra A.E. van der Geer1Mika Rizki Puspaningrum2Jan-Olaf Reschke3Iwan Pramesti Anwar4Ericson Hölzchen5ROCEEH Research Center, Senckenberg Research Institute, Senckenberganlage 25, Frankfurt am Main 60325, Germany; ROCEEH Research Center, Heidelberg Academy of Sciences and Humanities, Heidelberg, Germany; Corresponding author at: ROCEEH Research Center, Senckenberg Research Institute, Senckenberganlage 25, Frankfurt am Main 60325, Germany.Naturalis Biodiversity Center, Vertebrate Evolution, Development and Ecology, Darwinweg 2, Leiden 2333 CR, the NetherlandsBandung Institute of Technology, Faculty of Earth Sciences and Technology, Bandung, IndonesiaROCEEH Research Center, Senckenberg Research Institute, Senckenberganlage 25, Frankfurt am Main 60325, Germany; Goethe University, Dept. of Biosciences, Paleobiology and Environment, Frankfurt am Main, GermanyBandung Institute of Technology, Faculty of Earth Sciences and Technology, Bandung, IndonesiaTrier University, Universitätsring 15, Trier, Germany; German Research Center for Artificial Intelligence (DFKI), Behringstraße 21, Trier, GermanyDispersal of terrestrial mammals into Wallacea requires the crossing of sea straits. Stegodons, an extinct family of proboscideans, managed to settle on roughly a dozen Wallacean islands during the Pleistocene. Their distribution pattern is, however, not well understood. It results from the interaction of two specific processes, namely respective swimming performances on the one hand, as well as island dwarfing on the other. Reduction of body mass has an impact on swimming performance, because smaller size leads to a slower swimming speed and lower deposits of available energy. In this study we conducted a series of experiments with the agent-based model SEAcross, designed to monitor swimming performances of terrestrial mammals across sea straits by measuring crossing success rates (CSR). We found that the dispersal pattern is in accordance with size-dependent swimming performances, geographic width as well as current speed and direction. Because currents change on a seasonal scale, bottlenecks decelerating or even preventing dispersal are rarely absolute, but should be considered as seasonal phenomena. Our results allow for an in-depth analysis of dispersal routes and success. Dispersal performances cannot, however, explain the lack of a fossil record of stegodons in the eastern part of Wallacea. With very few exceptions, routes should be manageable for terrestrial mammals with the size of a stegodon. Our results illustrate, however, the usefulness and applicability of agent-based models in order to further examine geographic dispersal barriers in conjunction with the dynamics of animal behavior.http://www.sciencedirect.com/science/article/pii/S2950475925000103StegodonPleistoceneWallaceaDispersalAgent-based modelInsular dwarfism
spellingShingle Christine Hertler
Alexandra A.E. van der Geer
Mika Rizki Puspaningrum
Jan-Olaf Reschke
Iwan Pramesti Anwar
Ericson Hölzchen
Stegodon SEA-crossing: Swim, shrink, and disperse
Earth History and Biodiversity
Stegodon
Pleistocene
Wallacea
Dispersal
Agent-based model
Insular dwarfism
title Stegodon SEA-crossing: Swim, shrink, and disperse
title_full Stegodon SEA-crossing: Swim, shrink, and disperse
title_fullStr Stegodon SEA-crossing: Swim, shrink, and disperse
title_full_unstemmed Stegodon SEA-crossing: Swim, shrink, and disperse
title_short Stegodon SEA-crossing: Swim, shrink, and disperse
title_sort stegodon sea crossing swim shrink and disperse
topic Stegodon
Pleistocene
Wallacea
Dispersal
Agent-based model
Insular dwarfism
url http://www.sciencedirect.com/science/article/pii/S2950475925000103
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