Sunken Lands Reveal Rising Seas Caused By Glacial Melting Linked To Caribbean Extinction Of Bats

 

Credit: Stony Brook

 

According to Professor Dávalos and her colleague Amy L. Russell, PhD, Assistant Professor, Department of Biology at Grand Valley State University in Michigan, the high extinction rate following deglaciation in the Caribbean has been noted for decades and rich fossil deposits in the Bahamas and the Greater Antilles attest to a fauna that no longer exists. Among mammals, most terrestrial species were wiped out around the time humans arrived, and many bat populations that existed elsewhere went extinct (e.g., Cuban vampire bat, Puerto Rican flower bat, etc.) on one or several islands. The many instances of both extinction and persistence of bats across dozens of islands made it an ideal system for investigating how climate change may shape island fauna.

 

Liliana M. Dávalos, PhD, Assistant Professor, Department of Ecology and Evolution, Stony Brook University.

Credit: Stony Brook

 

The researchers used deep sea-bathymetry (measurement of underwater depth) and Geographic Information Systems (GIS) to model the extent to which land would have been exposed in the Caribbean at the peak of the glaciation, when sea levels were 125 meters below their current levels. Combining the record of current and fossil bats with the area for each island, they then used a simple mathematical relationship between the number of species and area of an island to estimate the number of local extinction events that could be explained by the change in area.

 

The skulls of Subfossil Caribbean bats from the Dominican Republic.

Credit: Courtesy of the Museo del Hombre Dominicano, Dr. Renato Rímoli and the Antillothrix Projec

Together, they found that most of the species loss in the Bahamas and Greater Antilles could be explained by the loss of area caused by rising sea levels. In the Lesser Antilles the mathematical models pointed out gaps in the fossil record of most islands. The large impact of area loss on species loss held, even after excluding species that may have colonized the islands recently and accounting for coral growth in the Bahamas.

“There have been many explanations before as to why so many bat populations collapsed: cave drowning, the arrival of new species, lack of tolerance to the warmer and wetter climate of the Holocene are examples,” said Professor Dávalos.

 

Noctilionoid bats comprise more than 200 species that span nearly the entire ecological diversity of land mammals. They range from tiny insectivores and nectarivores to large carnivores, and even vampire bats. This superfamily provides an unparalleled system for understanding how, when, and where bats evolved new diets, changed roosting habits and developed different kinds of echolocation. This project will use DNA sequences and comparison of morphological variations to reconstruct evolutionary relationships among these bats, including the fossils of >20 extinct species. Together with powerful methods for estimating the timing of historical events, this extensive fossil series will provide a timeline for investigating patterns and processes of ecological adaptation, speciation, and extinction across all species.

“We were expecting area loss to be important in explaining extinction, but not as important as we found. This drives home the point that rising sea levels pose great risks to biodiversity today,” Professor Russell said.