A lineage colonizing a geographic region with no competitors may exhibit rapid diversification due to greater ecological opportunity. The resultant species diversity of this primary-colonizing (incumbent) clade may limit subsequent lineages’ ability to persist unless these non-incumbent lineages are ecologically distinct. We compare the diversity in diet-related mandibular morphology of two sympatric murid rodent clades endemic to Luzon Island, Philippines—incumbent Phloeomyini and secondary-colonizing Chrotomyini—to the mandibular morphological diversity of Sahul Hydromyini, the sister clade of Chrotomyini and the incumbent murid lineage on the supercontinent of Sahul. This three-clade comparison allows us to test the hypothesis that incumbent lineages can force persistent ecological distinction of subsequent colonists at the time of colonization and throughout the subsequent history of the two sympatric clades. We find that Chrotomyini forms a subset of the diversity of their clade plus Sahul Hydromyini that minimizes overlap with Phloeomyini. We also infer that this differentiation extends to the stem ancestor of Chrotomyini and Sahul Hydromyini, consistent with a biotic filter imposed by Phloeomyini. Our work illustrates that incumbency has the potential to have a profound influence on the ecomorphological diversity of colonizing lineages at the island scale even when the traits in question are evolving at similar rates among independently colonizing clades.

This archive contains a total of 88 files in 11 directories detailing analyses of comparative morphological evolution of mandibular shape of the Luzon Old Endemics and Sahul hydromyines after landmark collection.

Note 1: The R scripts require files from the Dryad archive associated with: Rowsey et al. 2019. Tempo and mode of mandibular shape and size evolution reveal mixed support for incumbency effects in two clades of island-endemic rodents (Muridae: Murinae) Evolution 73:1411-1427. The archive can be found here: https://doi.org/10.5061/dryad.gb7k5d1 

Note 2: throughout the script we refer to Phloeomyini as cloud rats (abbreviated "cr"), Chrotomyini as earthworm mice (abbreviated "ewm"), and Sahul Hydromyini as Sahul Old Endemics (abbreviated "SOE") which are alternative names for these respective clades.

Note 3: Sahul hydromyine mandible photographs will be deposited at the museums where the specimens were borrowed.