WHERE DID YOU COME FROM? WHERE DID YOU GO? NEW RADIOCARBON DATES FOR RECENTLY-EXTINCT HISPANIOLAN RODENTS CLARIFY TIMING OF SPECIES LOSS AND SUGGEST EXTINCTION TRIGGERS ON THE TIBURON PENINSULA

Today, Hispaniola has one endemic rodent (Plagiodontia aedium, Cuvier’s Hutia), while non-endemic murid rats and mice are prevalent. Until recently, the island had at least 10 endemic rodent species. Previously, just 15 radiocarbon dates were available for these extinct rodents, with most species only represented by one or two dates. Consequently, the timing and triggers of rodent extinction are poorly understood; natural climate change and human impacts have both been suggested. We radiocarbon dated 68 specimens from P. aedium and six extinct species (P. ipnaeum, Hexolobodon phenax, Rhizoplagiodontia lemkei, Isolobodon montanus, I. portoricensis, and Brotomys sp.) from the Tiburon Peninsula of southwestern Hispaniola. Combining these dates with previously published ones from the Tiburon, we can evaluate the timing of regional species loss. Directly measured last appearance dates for extinct species (in median calibrated years before present, Cal BP) are: 5407 Cal BP (H. phenax); 2227 Cal BP (R. lemkei); 1322 Cal BP (I. montanus); 1154 Cal BP (I. portoricensis); 778 Cal BP (Brotomys sp.); and 523 Cal BP (P. ipnaeum). All seven species were present in the mid-Holocene and co-existed with humans during the Lithic Cultural Period (ca. 6000 years ago). An absence of dates for H. phenax after ca. 5000 Cal BP roughly coincides with the beginning of the Archaic Cultural Period (ca. 5000-2500 years ago), while most recent dates for other taxa roughly coincide with the Ceramic Cultural Period (ca. 2500-500 years ago) and European arrival (ca. 500 years ago). This strongly implicates humans in the extirpation of endemic rodents from southwest Hispaniola. Most species were present in the late Pleistocene and early Holocene, but the earliest appearance of both Brotomys sp. and I. portoricensis is between 7000 and 5000 years ago. This may indicate movement of these species from central Hispaniola, either via natural immigration (the Tiburon Peninsula was periodically separated from northeastern Hispaniola during the Plio-Pleistocene) or by people. Dates from elsewhere on Hispaniola will help distinguish regional from island-wide trends in species presence (and absence) throughout the Holocene and provide additional evidence for extinction triggers.