Exploring Rattus praetor (Rodentia, Muridae) as a possible species complex using geometric morphometrics on dental morphology

Overview & Synopsis

Taxonomic uncertainties in the Rattus genus persist due to among-species morphological conservatismcoupled with within-species environmental variation in morphology. As a result, this genus containsa number of possible cryptic species. One important example can be found in R. praetor, where morphologicalstudies indicate it is a possible species complex. Genetic studies of R. praetor (limited toanalysis of mitochondrial DNA) have been inconclusive, but do indicate such subdivision. Here we usegeometric morphometrics to explore this possible species complex by analysing the dental traits of48 specimens from New Guinea and neighbouring regions. We find separate molar morphologies forBougainsville Island, central New Guinea and west New Guinea which cannot be easily explained bydifferent environmental factors (climate, precipitation and altitude), strongly suggesting the existence ofa number of evolutionarily distinct taxa within what is currently called R. praetor thus supporting previoussuggestions that R. praetor is a species complex. Our findings demonstrate the potential of advancedmorphological analyses in identifying separate species, contrary to the claims of morphological conservatism.Future analyses should combine geometric morphometrics with genetic analyses over the speciesrange and include sub-fossil specimens from the Bismarck archipelago and Solomon Islands to resolvethe evolutionary history of R. praetor.