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      Extinct before discovered? Epactoides giganteus sp. nov. (Coleoptera, Scarabaeidae, Scarabaeinae), the first native dung beetle to Réunion island

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          Abstract

          We describe a new species of dung beetle, Epactoides giganteus sp. nov., from a single female specimen allegedly collected in the 19th century on Réunion island and recently found at the Muséum national d’Histoire naturelle, Paris. This species differs from other species of Epactoides by larger size and a set of other distinctive morphological characters. Epactoides giganteus sp. nov. is the first native dung beetle (Scarabaeinae) of Réunion, and its discovery expands the known area of distribution of the genus Epactoides, which was hitherto believed to be endemic to Madagascar. Like other taxa from Madagascar and peripheral islands (e.g., Comoro, Seychelles, Mascarenes), E. giganteus sp. nov. may have reached Réunion by over-water dispersal. Given the rapid loss of biodiversity on Réunion island and the fact that no additional specimens were re-collected over the last two centuries, it is very likely that E. giganteus sp. nov. has gone extinct. However, we have unconfirmed evidence that the holotype of E. giganteus sp. nov. might be a mislabeled specimen from Madagascar, which would refute the presence of native dung beetles on Réunion. We discuss both hypotheses about the specimen origin and assess the systematic position of E. giganteus sp. nov. by examining most of the described species of Madagascan Epactoides. Additionally, we provide a brief overview of the dung beetle fauna of Mascarene Archipelago.

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          Most cited references 38

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          Has Vicariance or Dispersal Been the Predominant Biogeographic Force in Madagascar? Only Time Will Tell

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            Multiple overseas dispersal in amphibians.

            Amphibians are thought to be unable to disperse over ocean barriers because they do not tolerate the osmotic stress of salt water. Their distribution patterns have therefore generally been explained by vicariance biogeography. Here, we present compelling evidence for overseas dispersal of frogs in the Indian Ocean region based on the discovery of two endemic species on Mayotte. This island belongs to the Comoro archipelago, which is entirely volcanic and surrounded by sea depths of more than 3500 m. This constitutes the first observation of endemic amphibians on oceanic islands that did not have any past physical contact to other land masses. The two species of frogs had previously been thought to be nonendemic and introduced from Madagascar, but clearly represent new species based on their morphological and genetic differentiation. They belong to the genera Mantidactylus and Boophis in the family Mantellidae that is otherwise restricted to Madagascar, and are distinguished by morphology and mitochondrial and nuclear DNA sequences from mantellid species occurring in Madagascar. This discovery permits us to update and test molecular clocks for frogs distributed in this region. The new calibrations are in agreement with previous rate estimates and indicate two further Cenozoic transmarine dispersal events that had previously been interpreted as vicariance: hyperoliid frogs from Africa to Madagascar (Heterixalus) and from Madagascar to the Seychelles islands (Tachycnemis). Our results provide the strongest evidence so far that overseas dispersal of amphibians exists and is no rare exception, although vicariance certainly retains much of its importance in explaining amphibian biogeography.
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              The role of geography and ecological opportunity in the diversification of day geckos (Phelsuma).

              We examine the effects of ecological opportunity and geographic area on rates of species accumulation and morphological evolution following archipelago colonization in day geckos (genus Phelsuma) in the Indian Ocean. Using a newly generated molecular phylogeny for the genus, we present evidence that these geckos likely originated on Madagascar, whereas colonization of three archipelagos in the Indian Ocean, the Seychelles, Mascarene, and Comoros Islands has produced three independent monophyletic radiations. We find that rates of species accumulation are not elevated following colonization but are roughly equivalent on all three isolated archipelagos and on the larger island of Madagascar. However, rates of species accumulation have slowed through time on Madagascar. Rates of morphological evolution are higher in both the Mascarene and Seychelles archipelagos compared to rates on Madagascar. This negative relationship between rate of morphological evolution and island area suggests that ecological opportunity is an important factor in diversification of day gecko species.
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                Author and article information

                Contributors
                (View ORCID Profile)
                Journal
                ZooKeys
                ZK
                Pensoft Publishers
                1313-2970
                1313-2989
                October 01 2021
                October 01 2021
                : 1061
                : 75-86
                Article
                10.3897/zookeys.1061.70130
                © 2021

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