UNDERSTANDING THE PAST TO PROTECT MODERN DIVERSITY: DOCUMENTING THE HISTORY OF HOLOCENE VERTEBRATE EXTINCTION IN THE CARIBBEAN

1. Understanding the past to protect modern diversity:
Documenting the history of Holocene vertebrate
extinction in the Caribbean
Jessica A. Oswald1,2, Julie M. Allen1, Brian J. Stucky2, Robert P. Guralnick2, David W. Steadman2, Michelle J. LeFebvre2
1. Biology Department, University of Nevada, Reno, Reno, NV 89557, USA
2. Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA
Acknowledgements: Funding for this research provided by NSF DEB grant (UF: 033905; UNR: 2034316), Department of Natural History (Florida
Museum of Natural History), and South Florida Archaeology and Ethnography Program (Florida Museum of Natural History). We thank colleagues and
collaborators from the Antiquities, Monuments & Museums Corporation, Bahamas for their continued support of this research, including Dr. Grace Turner,
Nancy Albury, and Kelly Fowler.

2. Background, aims, methods
Human arrival in the Caribbean in the mid-Holocene (ca. 6,000 years ago) marked the beginning of a
major vertebrate extinction event across the region, followed by a second wave of extinction upon
European arrival. Many species are imperiled in the region today.
Therefore, the Caribbean is an excellent focal region to study pre-human but post Pleistocene vertebrate
diversity and to ask the following questions:
1. What diversity should be present in pre-human (pristine) sites and what can this diversity tell us
about ecological, evolutionary, and biogeographic patterns in pristine systems?
2. Beyond causing extinction, how did humans interact with extinct, extirpated, and living taxa?
Ultimately, understanding which species should be present if not for human impacts, their evolutionary
relationships, and their relationships with humans before their extinction will help to develop
comprehensive baseline data of diversity loss and conservation initiatives.
For this work we are using fossils and zooarchaeological specimens, radiocarbon dating, and ancient
DNA to investigate historical diversity, distributions, and human impacts on Caribbean species.

3. 1. Biogeographic and evolutionary insights from extinct species: Nesotrochis
steganinos
Nesotrochis is a genus composed of three flightless species
endemic to Greater Antilles that became extinct upon European
colonization of the Caribbean.
Nesotrochis was long thought to be an aberrant species of rail
(Rallidae) based on morphology.
We obtained a mitochondrial genome from DNA from a Nesotrochis
steganinos 7,000 year-old toe bone.
Results: Mitochondrial phylogeny indicates Nesotrochis is not a rail
but likely deserves its own family and is related to the extant
flufftails (Sarothruridae) and the extinct, flightless New Zealand
Adzebill (Aptornithidae)
Importance: This is the only known Caribbean taxa with sister
relationships to Old World families.
Understanding the relationships of extinct taxa provides novel
insight into biogeographic processes and evolutionary mechanisms
including the repeated loss of flight of the most recent common
ancestor of Aptornithidae + Sarothruridae + Nesotrochis.
Nesotrochis - cave-rails (extinct; 3 species; flightless)
Sarothruridae - flufftails (extant; 15 species; flighted)
Aptornithidae - adzebills (extinct; 2 species; flightless)
Oswald et al. 2021 Biology Letters
Nesotrochis stegninos fossil sampled for DNA

4. 2. Human translocations and extinct diversity: Geocapromys ingrahami
Today the Bahamian Hutia (Geocapromys ingrahami) is restricted
to East Plana Cay (green dot & arrow in figure) and was recently
introduced to other small cays. However, it was once found
across the Bahamas and Turks and Caicos during the Holocene.
Radiocarbon dating indicates that indigenous people likely
introduced Bahamian hutia from the Great Bahama Bank (purple
circle) to the Little Bahama Bank (Abaco and Grand Bahama).
Ancient DNA from multiple individuals sampled (blue dots) from
paleontological sites across the Bahamian Archipelago reveals
an extinct northern population (Abaco + Eleuthera; above red
line) that is 2.2% divergent from the extant southern population.
Radiocarbon and isotopic data also indicate that indigenous
peoples brought Bahamian hutia to the Turks and Caicos (orange
star; LeFebvre et al. 2019, Environmental Archaeology).
Bahamian hutia Source: repeatingislands.com
Oswald et al. 2020 Scientific Reports
Fossil sample
Extant population
Great Bahama Bank
Population boundary
Turks and Caicos
KEY

5. Quantifying extant and extinct diversity will help to develop diversity baselines
There is ongoing NSF-funded work to place extinct bird species
(Figure 1A) and extirpated populations (Figure 1B) of Caribbean
birds in phylogenetic contexts with ancient DNA to understand
biogeographic, evolutionary, and extinction patterns across the
Holocene.
Archaeological and paleontological sampling with radiocarbon
dating of focal bird species of will allow for insights into human
translocations of taxa.
Ancient DNA of Geocapromys species from archaeological sites
will aid in understanding overall historical diversity of this genus
and how species were translocated as people spread across the
Caribbean. Figure 1. A. Distribution of extinct focal taxa B. Extant focal species that have
experienced Holocene extirpation. Purple = modern distribution, green =
extirpated population. Athene and Amazona illustrations are from HBW Alive
(del Hoyo et al., 2018)
Ultimately, understanding which native species should still be present on Caribbean
islands if humans never arrived will help to devise comprehensive conservation initiatives
(figure to the left) by providing genetic diversity baselines and historical and native
distributions.