Island history affects faunal composition: the treeshrews (Mammalia: Scandentia: Tupaiidae) from the Mentawai and Batu Islands, Indonesia

Abstract

The Mentawai and Batu Island groups off the west coast of Sumatra have a complicated geological and biogeographical history. The Batu Islands have shared a connection with the Sumatran ‘mainland’ during periods of lowered sea level, whereas the Mentawai Islands, despite being a similar distance from Sumatra, have remained isolated from Sumatra, and probably from the Batu Islands as well. These contrasting historical relationships to Sumatra have influenced the compositions of the respective mammalian faunas of these island groups. Treeshrews (Scandentia, Tupaiidae) from these islands have, at various times in their history, been recognized as geographically circumscribed populations of a broadly distributed Tupaia glis, subspecies, or distinct species. We used multivariate analyses of measurements from the skull and hands to compare the island populations from Siberut (Mentawai Islands) and Tanahbala (Batu Islands) with the geographically adjacent species from the southern Mentawai Islands (T. chrysogaster) and Sumatra (T. ferruginea). Results from both the skull and manus of the Siberut population show that it is most similar to T. chrysogaster, whereas the Tanahbala population is more similar to T. ferruginea, confirming predictions based on island history. These results are further corroborated by mammae counts. Based on these lines of evidence, we include the Siberut population in T. chrysogaster and the Tanahbala population in T. ferruginea. Our conclusions expand the known distributions of both the Mentawai and Sumatran species. The larger geographical range of the endangered T. chrysogaster has conservation implications for this Mentawai endemic, so populations and habitat should be re‐evaluated on each of the islands it inhabits. However, until such a re‐evaluation is conducted, we recommend that the IUCN Red List status of this species be changed from ‘Endangered’ to ‘Data Deficient’. Published 2013. This article is a U.S. Government work and is in the public domain in the USA, Biological Journal of the Linnean Society, 2014, 111, 290–304.

Rule reversal: Ecogeographical patterns of body size variation in the common treeshrew (Mammalia, Scandentia)

“…For the purposes of this study, we recognize Tupaia glis as comprising those populations taxonomically equated with this species by Helgen (), with the exception of several populations we recently recognized as distinct ( T. ferruginea from Sumatra and Tanahbala Island; T. discolor from Bangka Island; T. hypochrysa from Java; and T. chrysogaster from the Mentawai Islands, including Siberut Island: Sargis, Woodman, Reese, et al., ; Sargis, Woodman, Morningstar, et al., ; Sargis, Woodman, et al., ).…”

“…To evaluate morphological variation within and among populations, EJS recorded 22 craniomandibular variables ( Table 2) employed in previous studies of treeshrews (Sargis, Woodman, Morningstar, et al, 2013;Sargis, Woodman, et al, 2014;Sargis, Campbell, et al, 2014;Sargis et al, 2017) from adult skulls (those with fully erupted permanent dentition) using digital calipers. Total length and body weight were recorded from skin tags or the original field notes of collectors.…”

“…We further explored the effect of a number of additional factors on the variation in body size among the 13 island populations. We T A B L E 2 Measurement descriptions (and abbreviations) following Sargis, Woodman, Morningstar, et al (2013), Sargis, Woodman, et al (2014), Sargis, Campbell, et al (2014), Sargis et al (2017). Uppercase abbreviations for teeth (i.e., I, C, P, M) refer to maxillary and premaxillary teeth; lowercase abbreviations (i, c, p, m) refer to mandibular teeth Because of collinearity in the explanatory variables, we did not attempt to model or estimate the strength of the main effects, but instead focused on determining the sign of these effects (i.e., positive or negative) because we were interested in testing the generality of ecogeographical patterns.…”

“…They are seemingly poor overwater dispersers, so their distribution on islands is presumably attributable to vicariance resulting from sea‐level fluctuations in most cases (Olson, Sargis, & Martin, ; Roberts et al., ). Although they have been included in some taxonomically broad tests of the island rule (e.g., Lomolino et al., ; Meiri et al., ), they have never been the focus of an intensive study, and recent taxonomic revisions that have greatly altered our understanding of the geographical ranges of individual species (Sargis, Campbell, & Olson, ; Sargis, Woodman, Morningstar, Reese, & Olson, ; Sargis, Woodman, Morningstar, Reese, & Olson ; Sargis, Woodman, Reese, & Olson, ) have not been taken into account in these meta‐analyses. Furthermore, Bergmann's rule has never been tested in treeshrews, nor has the possible interaction between these two rules (e.g., Fooden & Albrecht, ).…”

Molecular systematics and biogeography of the Hemigalinae civets (Mammalia, Carnivora)

“…Very little is known about the population from Siberut Island, which has not been attributed to any subspecies (Jennings et al 2013). The four Mentawai Islands were likely connected during periods of lower sea levels (Sathiamurthy & Voris 2006), and there does not seem to be any endemism on each island, as several species occur on all or several of the four islands (Sargis et al 2014). It is therefore likely that banded civets from the islands of Siberut, Sipora and South Pagai belong to the same taxon, which would be Hemigalus derbyanus minor.…”