Treeshrews (Scandentia): an integrative review of taxonomy, ecology, evolution, and conservation

Treeshrews (order Scandentia) are a phylogenetically significant mammalian lineage restricted to the tropical forests of South and Southeast Asia and southwestern China, representing an important component of the Euarchonta. Despite their evolutionary significance, treeshrews remain among the least comprehensively studied mammalian orders. This review synthesizes current knowledge across taxonomy, phylogeny, morphology, ecology, behavior, reproduction, and molecular biology to provide an integrative understanding of the group. Recent advances in molecular and morphological studies confirm Ptilocercus lowii as the earliest-diverging lineage and highlight substantial diversity in locomotor strategies, ranging from fully arboreal to predominantly terrestrial forms. Ecological and behavioral studies reveal niche differentiation, diverse foraging strategies, rapid digestive processing of fruit, specialized feeding behaviors, and interspecific associations, underscoring their functional role in tropical forest ecosystems. Reproductive biology is characterized by unique life-history traits such as absentee maternal care, energetically rich milk composition, and variable nesting strategies, reflecting adaptations to predation risk and resource availability. Genomic and molecular studies have positioned Tupaia belangeri as a key non-rodent, non-primate biomedical model, bridging the gap between traditional laboratory rodents and primates in studies of viral infections, neurobiology, metabolism, and immune function. At the same time, molecular phylogenetics and population genetics approaches have improved resolution of species boundaries, dispersal patterns, and adaptive responses to environmental gradients. Despite these advances, significant gaps remain. Research is heavily biased toward a few model species, particularly T. belangeri , while many island endemics and Data Deficient taxa remain poorly studied. Fossil records are sparse, long-term ecological and demographic data are lacking, and genomic resources across Southeast Asian lineages are still limited. Conservation assessments further reveal dynamic status changes, with Tupaia nicobarica (Endangered) and T. chrysogaster (Vulnerable) highlighting the vulnerability of range-restricted species. An integrative framework combining taxonomy, ecology, behavior, and genomics is therefore essential to advance treeshrew research and conservation. Priority areas include (i) systematic field surveys and ecological studies of poorly known and insular taxa, (ii) expansion of population genomic and phylogeographic datasets across the group, and (iii) long-term monitoring of populations and habitats to inform evidence-based conservation strategies. By synthesizing multidisciplinary evidence, this review provides a comprehensive foundation for future research and conservation planning in Scandentia.