From the pleistocene to the anthropocene [electronic resource] : fossils, genes, and the future of Caribbean mammals
Keywords: Biology.

Islands are widely touted the ideal laboratories in which to study fundamental evolutionary processes. However, islands are also designated as global conservation priorities given their exceptional vulnerability to modern human activities. A glance at the historic past reveals more than half of all extinctions since 1500 AD have occurred on islands, and evaluation of the fossil record has uncovered massive prehistoric extinctions across the Quaternary. Taken together, these extinctions in the recent and deeper past suggest that islands also provide critical opportunities to illuminate fundamental extinction processes -- the other side of the evolutionary coin. In this dissertation, I use insular faunal records to disentangle the mechanisms underlying extinction dynamics across the Pleistocene and Holocene, and I follow the trail of surviving species to understand what new selective pressures they face in the Anthropocene. This narrative of extinction and survival through time, spanning the Pleistocene to the Anthropocene, offers a practical lesson in how to apply hindsight of the past in guiding conservation planning for the future. The islands of the Caribbean are on the frontlines of global change; they face rapid deforestation, sea level rise, a burgeoning human population, and an onslaught of invasive species. My dissertation crosses traditional disciplinary and temporal boundaries by interrogating paleontological, palynological, archaeological, ecological, and genetic lines of evidence across the past 15,000 years to holistically reconstruct the dynamics of change in this system at the species and community levels. The first portion of my dissertation leveraged a dataset of over 1,500 radiocarbon dates to reconstruct the ramifications of human arrival in the Caribbean, distinguishing the impacts of Archaic, Ceramic, and European cultures (Ch. 1). This analysis identified the selective loss of large- and small-bodied mammal species, with only medium-sized species alive today. I conducted extensive fieldwork in the Dominican Republic with one surviving species, the Hispaniolan Solenodon, Solenodon paradoxus, to understand what traits promoted its persistence in the past and its survival in the present. The solenodon, a Eulipotyphlan, is considered a "living fossil", and its continued survival represents the conservation of over 50 million years of unique evolutionary history. I investigated whether dietary generalism and flexibility are the mechanisms underlying solenodon survival using feces, which provide a rapid snapshot of an animal's resource use. I applied two complementary approaches: stable isotopes (Ch. 2) and DNA metabarcoding (Ch. 3), and revealed that solenodons inherited a generalist Holocene niche and are able to flexibly feed from numerous taxonomic and trophic groups. These data suggest that, ecologically, the Anthropocene provides resources suitable for solenodon survival. Finally, I assembled a long-term picture of solenodon survival by providing multiple historic baselines of genetic diversity for the species across the past hundred years (Ch. 4). Sequences from museum specimens revealed the recent, rapid extensive loss of genetic diversity and connectivity across the island. Thus, while solenodons may be able to cope with changing landscapes at the population level, as a whole their range has collapsed, likely linked to predation by dogs and other human activities. These findings, integrated into a broader context of Caribbean extinctions, suggest that in some cases, survival mechanisms of the Pleistocene/Holocene may not align with the traits needed to thrive in the Anthropocene. Together, these data implicate recent (post-industrial) human activity as the main driver of solenodon decline in the Caribbean, creating a new extinction filter independent of ecological generalism and body size as in the past. Hands-on, collaborative management on the ground is necessary to ensure the survival of this "living fossil".