1 It is widely accepted that tropical lowland rain forest holds the greatest diversity of organisms, and it is often implied that this general pattern is also true for virtually all individual higher-level taxa. Standardized elevational transect surveys of non-flying small mammals (Insectivora and Rodentia) on geologically old, species-rich islands in the Philippines consistently show maximum diversity and relative abundance in upper montane/lower mossy forest at 1500–2200 m, often exceeding lowland species richness and relative abundance by a factor of three or more.

2 On mountains where maximum elevation exceeds 2000 m, there is a decline in species richness above about 1500–2000 m, yielding a curvilinear pattern of species richness along the elevational gradient. The peak in species richness occurs at the area of transition from montane to mossy forest, which is also the point at which rainfall probably peaks. In parallel with species richness, relative abundance of small mammals in the Philippines also increases from the lowlands to 1500–2200 m, increasing by a factor from two to 10.

3 Twelve hypotheses concerning patterns of diversity along elevational gradients, plus the null hypothesis, are evaluated. The null hypothesis of no variation and the hypotheses that maximum diversity is in the lowlands, that diversity is highest in areas of least perturbation, and that diversity increases with increasing area, are rejected. There is weak or ambiguous support for the hypotheses that diversity is greatest in areas of community interdigitation, that diversity is highest in the area of highest productivity, that diversity is correlated with habitat complexity, and that diversity is correlated with habitat diversity. There is strongest support for the hypotheses that diversity is correlated with annual rainfall, with total abundance of individuals in the community, with food resource diversity, with areas of reduced competition from other organisms, and with areas characterized by high rates of speciation.

4 Causality is difficult to evaluate because many hypotheses make non-exclusive predictions, they probably represent non-independent aspects of causal factors (in other words, there is much interaction among the processes highlighted by the various hypotheses), and they represent the range from proximate to ultimate and from descriptive to causal. All the hypotheses probably represent phenomena that exist in nature, but few (or none) represent phenomena found in all taxa. The primary challenge in the future will not be simply to accept or reject individual hypotheses, but rather to determine the circumstances under which the various causal factors are most important, how they interact, and how they can be combined into a more comprehensive and general multi-factorial model.

Small mammal diversity along elevational gradients in the Philippines: an assessment of patterns and hypotheses

Large collections of fragmentary animal bones excavated from archaeological contexts in East Timor between 1968 and 2002 provide new material referable to the recently extinct, gigantic murine genus Coryphomys. We document the upper and lower dentition and palatal anatomy of C. buehleri Schaub, 1937, and identify and name a second species of Coryphomys, based on differences in molar size and morphology and skeletal robusticity. Alternative interpretations of the observed morphological and metric variability (sexual dimorphism, resource-based polymorphism, sample heterochroneity) are each carefully assessed and rejected, and we conclude that the genus comprised two species of approximately similar body size. Preserved cranial elements of both species of Coryphomys feature a high degree of anatomical specialization, including an unusual elaboration of the maxillary sinus complex. Though the specialized anatomy of Coryphomys invites consideration of its phylogenetic relationships, this exercise is h...

Quaternary Murid Rodents of Timor Part I: New Material of Coryphomys buehleri Schaub, 1937, and Description of a Second Species of the Genus

We describe a new species of wide-disked ranine frog from Aurora National Park and possibly Mt. Cetaceo, two montane localities within the geologically distinct Sierra Madres coastal mountain range, eastern Luzon Island, Philippines. This endemic differs from Philippine congeners in the R. everetti species group by the combination of a relatively small body size, the presence of densely distributed asperities throughout the skin of most males, a translucent tympa- num in females and most males, an iridescent green dorsum with black spots or faint reticulum in males and an iridescent green to golden dorsum with distinctive brown reticulum in females. In addition to the new species, we support the designation of Rana everetti, R. luzonensis, and R. albotuberculata as distinct evolutionary species, and we resurrect R. igorota from the synonymy of R. everetti luzonensis.

Everetti (anura: ranidae), description of a new species, and resurrection of rana igorota taylor 1922

Status of some philippine frogs referred to rana everetti (anura: ranidae), description of a new species, and resurrection of rana igorota taylor 1922

Body shape and life style of the extinct rodent Canariomys bravoi (Mammalia, Murinae) from Tenerife, Canary Islands (Spain)

This paper describes a preliminary field survey of bushy-tailed cloud rats Crateromys spp. and slender-tailed cloud rats Phloeomys in the Philippines in April and May 1990. Brief visits were made to all islands/locations known to support these animals and also to neighbouring areas considered likely to do so. Comparing the results with information from previous surveys suggests that both genera, particularly Crateromys, are more widely distributed than formerly believed, but that some forms are threatened. Three of the four known species of Crateromys are known only from their holotype specimens, one of which awaits description. Another is extinct in its type locality on Ilin Island but may survive on neighbouring Mindoro. These preliminary findings indicate that thorough surveys are required to establish the status of certain species, to investigate the possibility that new species remain undiscovered and to develop conservation plans to reduce the likelihood of further extinctions occurring. The discovery of the Panay species means that the genus Crateromys is now known from widely separated locations in each of the four principal faunal regions or late Pleistocene

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C. R. Cox

Papers

Cloud rats in the Philippines — preliminary report on distribution and status