A la izquierda, la ardilla de vientre gris meridional (Callosciurus concolor), antes clasificada como subespecie de Callosciurus caniceps. Foto: christopheradler (iNaturalist). A la derecha, la ardilla rayada del sudeste asiático (Tamiops barbei) antes considerada subespecie de Tamiops mcclellandii. Foto: davidaw (iNaturalist)

Despite their abundance, many squirrel species remain poorly studied. In total there are almost 300 known species in the world. Now, thanks to a new study, there are two more. An international team from Spain, Japan, Mexico and the United States, led by a researcher from the Smithsonian's National Museum of Natural History and initiated at the Doñana Biological Station - CSIC, has confirmed the existence of two new squirrel species until now considered subspecies: the Southeast Asian striped squirrel (Tamiops barbei) and the southern grey-bellied squirrel (Callosciurus concolor).

During the last century, these squirrels were mistakenly classified as subspecies of two widely distributed species: Tamiops mclellandii y Callosciurus caniceps. However, the scientific team has determined that each of these squirrels actually corresponds to two distinct species that were incorrectly grouped together, a phenomenon known as ‘synonymy’. Arlo Hinckley, lead author of the study, began studying these squirrels during his doctoral thesis at the Doñana Biological Station and continues this work at the Smithsonian's National Museum of Natural History.

Through detailed analysis of physical characteristics, genetics, distribution and mating calls, the team considered that they were sufficiently distinct to be recognised as unique species and given their own identity. This discovery was made possible through collaboration between taxonomists, ethologists and citizen science platforms. On the one hand, researchers conducted molecular analyses and studies of the skulls and teeth of specimens from the Scientific Collections of different institutions. All this information was complemented with data from citizen science platforms such as iNaturalist, Observation and India Biodiversity, where citizens can register their observations of the natural world and which provided information on the distribution of different species. In addition, bioacoustic studies of mating calls of males were also carried out.

After analysis, the researchers concluded that former Tamiops mcclellandii populations to the east eastern Himalayas and Arakan range should be recognised as a single species, Tamiops barbei. Moreover, the populations of Callosciurus caniceps inhabiting Sundaland, in Southeast Asia, should be recognised as another single species, Callosciurus concolor.

Such studies are essential to support conservation efforts. Distinguishing species and their singularities provides more information when it comes to directing resources to study and protect them. According to the scientists, it is possible that there are many other squirrel species in the same situation, which is why they continue to work in search of other overlooked species.

Reference

Arlo Hinckley, Jesús E. Maldonado, Noriko Tamura, Jennifer A. Leonard, Melissa T. R. Hawkins. Lost in synonymy: Integrative species delimitation reveals two unrecognized species of Southern Asian tree squirrels (Rodentia: Sciuridae: Callosciurinae). Vertebrate Zoology, https://doi.org/10.3897/vz.74.e133467   

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