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Four new species of Rattus are described from the Moluccan islands (Maluku) of Indonesia: Rattus taliabuensis and R. feileri, both from the island of Taliabu, and R. halmaheraensis and R. obiensis from the islands of Halmahera and Obi, respectively. These descriptions are presented as part of a taxonomic review of Moluccan Rattus based on all known specimens in museum collections worldwide. Morphological characters, molecular systematics, and geographical distributions are documented for each of these species. Using both morpho-anatomical and morphometric approaches, we found that the Maluku Islands support Rattus taxa with spiny fur and two distinct morphotypes (1) species with a long tail and short rostrum (R. morotaiensis, R. halmaheraensis, R. obiensis, R. feileri) and (2) species with a short tail and long rostrum (R. taliabuensis, R. feliceus, R. ceramicus, R. elaphinus). Most of the new Moluccan species belong to a clade that includes members of the R. xanthurus species group from Sulawesi and the Australo-Papuan Rattus lineages. Their phylogenetic relationships highlight the role of Wallacea as an important area for diversification of Rattus into the Australo-Papuan region. Finally, the morphologically distinctive taxon Nesoromys ceramicus from Seram was found to be sister species to R. feliceus, and we relegate Nesoromys into the synonymy of the genus Rattus. The close affinities between R. ceramicus and R. feliceus may be an example of in situ island speciation, which has not been observed for small mammals on other Maluku Islands. [ABSTRACT FROM AUTHOR]

Aim: To determine the historical dynamics of colonization and whether the relative timing of colonization predicts diversification rate in the species‐rich, murine rodent communities of Indo‐Australia. Location: Indo‐Australian Archipelago including the Sunda shelf of continental Asia, Sahul shelf of continental Australia, the Philippines and Wallacea of Indonesia. Taxon: Order Rodentia, Family Muridae. Methods: We used a fossil‐calibrated molecular phylogeny and Bayesian biogeographical modelling to infer the frequency and temporal sequence of biogeographical transitions among Sunda, Sahul, the Philippines and Wallacea. We estimated diversification rates for each colonizing lineage using a method‐of‐moments estimator of net diversification and Bayesian mixture model estimates of diversification rate shifts. Results: We identified 17 biogeographical transitions, including nine originating from Sunda, seven originating from Sulawesi and broader Wallacea and one originating from Sahul. Wallacea was colonized eight times, the Phillipines five times, Sunda twice and Sahul twice. Net diversification rates ranged from 0.2 to 2.12 species/lineage/My with higher rates in secondary and later colonizers than primary colonizers. The highest rates were in the genus Rattus and their closest relatives, irrespective of colonization history. Main Conclusions: Our inferences from murines demonstrate once again the substantial role of islands as sources of species diversity in terrestrial vertebrates of the IAA with most speciation events occurring on islands. Sulawesi and broader Wallacea have been a major source of colonists for both island and continental systems. Crossings of Wallace's Line were more common than subsequent transitions across Lydekker's Line to the east. While speciation following colonization of oceanic archipelagos and large islands is consistent with adaptive radiation theory and ideas regarding ecological opportunity, we did not observe a strong signal of incumbency effects. Rather, subsequent colonists of landmasses radiated unhindered by previous radiations. [ABSTRACT FROM AUTHOR]