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Communities that occupy similar environments but vary in the richness of closely related species can illuminate how functional variation and species richness interact to fill ecological space in the absence of abiotic filtering, though this has yet to be explored on an oceanic island where the processes of community assembly may differ from continental settings. In discrete montane communities on the island of Sulawesi, local murine rodent (rats and mice) richness ranges from 7 to 23 species. We measured 17 morphological, ecological, and isotopic traits – both individually and as five multivariate traits – in 40 species to test for the expansion or packing of functional space among nine murine communities. We employed a novel probabilistic approach for integrating intraspecific and community‐level trait variance into functional richness. Trait‐specific and phylogenetic diversity patterns indicate dynamic community assembly due to variable niche expansion and packing on multiple niche axes. Locomotion and covarying traits such as tail length emerged as a fundamental axis of ecological variation, expanding functional space and enabling the niche packing of other traits such as diet and body size. Though trait divergence often explains functional diversity in island communities, we found that phylogenetic diversity facilitates functional space expansion in some conserved traits such as cranial shape, while more labile traits are overdispersed both within and between island clades, suggesting a role of niche complementarity. Our results evoke interspecific interactions, differences in trait lability, and the independent evolutionary trajectories of each of Sulawesi's six murine clades as central to generating the exceptional functional diversity and species richness in this exceptional, insular radiation. 

Abstract We describe 3 new species of shrews (Eulipotyphla, Soricidae, Crocidura) from West Sumatra, Indonesia. Two of these taxa were found above 1,800 m on Mt. Singgalang. The third taxon was found above 1,660 m on Mt. Talamau, 65 km northwest of Mt. Singgalang. We also resurrect Crocidura aequicauda based on 2 specimens from Mts. Tujuh and Kerinci, which lie near the border between West Sumatra and Jambi provinces. Several methodological approaches support our findings: linear cranial morphometrics, landmark-based 2D geometric morphometrics, and molecular phylogenetics using both mtDNA and 6 nuclear exons. A multilocus species-tree analysis places the 3 new species and C. aequicauda in a clade with the Javan endemics C. monticola and C. umbra. Although the 2 taxa from Mt. Singgalang are recovered as sister species, 1 is nearly twice the size of the other, and they are divergent in several other morphological characters, such as tail length, cranium size, and pelage color and texture. Recently diverged yet morphologically disparate sister taxa living syntopically in an isolated habitat “island,” like the montane forests of Mt. Singgalang, is unusual in mammals but documented in other Crocidura on neighboring Java and Borneo; these 2 new taxa represent the first known case of this phenomenon on Sumatra. Our results bring the number of Sumatran Crocidura to 10, 9 of which are endemic to the island. All 3 of the new species appear to be endemic to a single mountain and were not detected in similar surveys of nearby mountains. If this local endemism pattern is common, it would indicate that Sumatra’s mammal diversity may be severely underestimated, largely due to the paucity of small-mammal surveys and museum specimens. 

Abstract Crunomys and Maxomys are closely related murine genera from forested regions of Southeast Asia and western portions of the Indo-Australian Archipelago. Previous phylogenetic analyses suggested that a taxonomic reappraisal is necessary for these genera, but limited taxon sampling prevented formal changes. We produced a mitochondrial DNA dataset that includes 376 individuals representing all 22 recognized species and a nuclear dataset comprising thousands of ultraconserved elements missing only 1 recognized species. Our phylogenetic inferences consistently show that Crunomys is nested within Maxomys. We transfer all Maxomys species to the older genus Crunomys to resolve the paraphyly. We also conducted a morphological analysis of species from Sulawesi and described a new species of Crunomys from the eastern peninsula of the island. We identify 43 geographically defined mitochondrial haplogroups across all species of Crunomys, many of which also are inferred as distinct in a multilocus species delimitation analysis. Historical biogeographic reconstructions consistently inferred multiple dispersal events to and from oceanic islands and among continental shelf islands and mainland Southeast Asia. On both large continental shelf islands like Borneo and large oceanic islands like Sulawesi, in situ divergence produced high levels of diversity. 

Abstract Trabecular bone is modelled throughout an animal’s life in response to its mechanical environment, but like other skeletal anatomy, it is also subject to evolutionary influences. Yet the relative strengths of factors that affect trabecular bone architecture are little studied. We investigated these influences across the Philippine endemic murine rodent clade Chrotomyini. These mammals have robustly established phylogenetic relationships, exhibit a range of well-documented substrate-use types, and have a body size range spanning several hundred grammes, making them ideal for a tractable study of extrinsic and intrinsic influences on trabecular bone morphology. We found slight differences in vertebral trabecular bone among different substrate-use categories, with more divergent characteristics in more ecologically specialized taxa. This suggests that the mechanical environment must be relatively extreme to affect trabecular bone morphology in small mammals. We also recovered allometric patterns that imply that selective pressures on bone may differ between small and large mammals. Finally, we found high intrataxonomic variation in trabecular bone morphology, but it is not clearly related to any variable we measured, and may represent a normal degree of variation in these animals rather than a functional trait. Future studies should address how this plasticity affects biomechanical properties and performance of the skeleton. 

Although Borneo has received more attention from biologists than most other islands in the Malay Archipelago, many questions regarding the systematic relationships of Bornean mammals remain. Using next-generation sequencing technology, we obtained mitochondrial DNA sequences from the holotype ofSuncus ater, the only known specimen of this shrew. Several shrews collected recently in Sarawak are closely aligned, both morphologically and mitochondrially, with the holotype ofS. ater. Phylogenetic analyses of mitochondrial sequences indicate that theS. aterholotype and new Sarawak specimens do not belong to the genusSuncus, but instead are most closely related toPalawanosorex muscorum. Until nowPalawanosorexhas been known only from the neighboring Philippine island of Palawan. Additional sequences from nuclear ultra-conserved elements from the new Sarawak specimens strongly support a sister relationship toP. muscorum. We therefore transferatertoPalawanosorex. The new specimens demonstrate thatP. ateris more widespread in northern Borneo than previously recorded. Continued sampling of Bornean mammal diversity and reexamination of type material are critical in understanding the evolutionary history of the biologically rich Malay Archipelago. 

Abstract Albinism, a congenital disorder that results in a lack of melanin deposition, is common in domesticated animals but rare in nature. Among the ∼2500 species of rodents worldwide, only 67 have published reports of albinism. Here we report the capture of an albino murid (Muridae: Rodentia) from Mt. Singgalang in West Sumatra, Indonesia. The specimen is an adolescent but sexually mature maleMaxomys hylomyoides, a montane Sumatran endemic. To our knowledge, this specimen represents the first reported albino rodent from Indonesia and Sundaland, and only the second from Southeast Asia.