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Dryad

Infrequent oceanic long-range dispersal and evolution of a top terrestrial arthropod predator in the sub-Antarctic

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Apr 18, 2024 version files 549.40 KB

Abstract

The UNESCO world heritage sub-Antarctic terrestrial ecosystems are unique. They have been isolated for over 30 million years by constant circum-polar currents and winds, and shaped by climatic cycles that surpass the tolerance limits of many species. Despite this recognition, surprisingly little is known about how these ecosystems acquired their native terrestrial fauna and how it changed over deep time scales. Here the patterns and timing of colonization and speciation in the largest and dominant arthropod predators in the Eastern sub-Antarctic – spiders of the genus Myro – are demonstrated for the first time. Our results indicate that this lineage originated from Australia before the Plio-Pleistocenic glacial cycles and underwent an adaptive radiation on the Crozet archipelago. We discuss the gain and loss of pre-adaptations acting as filter that enabled only one of four Myro species native to the Crozet islands to repeatedly disperse via the Antarctic circum-polar current, resulting in an outstanding distribution range over 9000 kilometres. The results highlight the outstanding role of the volcanic Crozet archipelago for the evolution of arthropod life in the sub-Antarctic, and the potential of terrestrial macro-invertebrates to achieve rare but ecologically influential trans-oceanic dispersal events over thousands of kilometres under hostile conditions.