Tags Posts tagged with "Liliana M. Dávalos"

Liliana M. Dávalos

Liliana M. Dávalos, PhD. Photo by Angelique Corthals

Animals losing their habitats, humans losing their homes, deforestation and land grabbing are all well-documented issues in the Amazon — but some of their drivers have yet to be investigated. 

A newly established Fulbright Scholar Program called Fulbright Amazonia supports an international network of scientists who will carry out research dedicated to protecting the diverse wildlife and indigenous communities of the Amazon. Evolutionary biologist and Stony Brook University Professor Liliana M. Dávalos, PhD, will be part of this select group of international experts seeking to find solutions to some of the Amazon region’s ecological and environmental problems.

Dávalos, Professor of Conservation Biology in the Department of Ecology and Evolution in the College of Arts and Sciences, and the Fulbright Amazonia Scholar in Environmental Science, joins this first-ever cohort of scholars with research set to begin in July. Fulbright announced a total of 16 Fulbright Amazonia Scholars.

Under the fellowship, Dávalos will conduct research to study the dynamics of cocaine trafficking in the Amazon rainforest and assess the associated impact on land use.

The project will combine historical research with data analysis to measure the breadth of cocaine trafficking’s influence on long-standing environmental and humanitarian crises. The findings could have actionable impacts on regional policies throughout the Amazon. Dávalos believes the study will proved to be key to promoting sustainability within political and socioeconomic landscapes.

“Trafficking dynamics and their relationship to land use in the Amazon remain unexplored,” she said. “By providing the first quantitative analyses of this kind, my project will generate invaluable information on risks to protected areas and local communities and inform conservation and counterdrug policy.”

As a Stony Brook Professor, Dávalos has spearheaded leading ecological and biodiversity studies including work on biodiversity trends and changes in the Caribbean, how shrews shrink then regrow their brains, and the science behind sensory adaptations across mammals. Dávalos, an expert on the biodiversity of bat populations around the world, also co-directs the Global Union of Bat Diversity Networks (GBatNet), a position in which she brings research groups together worldwide to advance knowledge of ecological and evolutionary bat characteristics.

For more information about her research and collaborative work, visit the Dávalos Lab.

Aardvark. Pixabay photo

An international scientific project that compares the genomes of 240 living species of mammals has identified transposable elements (TEs) – genes that can change their position within a genome, creating or reversing mutations and thus altering a cell’s genetic identity – as a crucial area of study to help uncover the evolutionary process of mammals and to better understand biodiversity. Stony Brook University’s Liliana M. Dávalos is a collaborator in the analyses of TEs for the project. Two new papers, one published in the current issue of Science, and the other in Molecular Biology and Evolution, highlight the findings.

This graphic depicts the range of recently accumulated transposable elements (TEs) among sample mammals by proportion of their genome. Image credit: Osmanski et al. 2023 Science

The past 100 million years has caused mammals to adapt to virtually every environment on the planet. The Zoonomia Project, of which Dávalos is a scientific contributor, has cataloged the diversity in mammalian genomes by completing comparative genomic DNA sequences from the 240 species. The team, which consists of more than 150 scientists worldwide, published their multi-year comparative genome analysis in the Science paper.

Dávalos studies how biodiversity changes through time and what biological processes fuel biodiversity. She teamed up with David Ray and his lab at Texas Tech University to qualitatively analyze the dynamics of TEs.

The paper describes the TE repertoires of 248 placental mammals. TEs make up a sizeable proportion of all mammalian genomes, yet there is much variation from one species to the next. The scientific team points out that that relating TEs to biodiversity is far from simple. Additionally, with the ability to move throughout the genome, TEs can contribute to biodiversity or also stymie it.

“Determining how many transposable elements of each kind are in each species is key to figuring out how transposons contribute to biodiversity. It seems simple to relate these counts to the number of species or their ecology, however that is misleading,” explains Dávalos, Professor of Conservation Biology in the Department of Ecology and Evolution, and a co-author of the paper. “Some species , like bats and whales, believe it or not are more closely related to each other than to others, such as bats and primates, so we must factor this related into our statistics within the comparative genomic mammalian analyses.”

The researchers identified more than 25,000 TE sequences in the mammalian set, with some mammals having large portions of TEs in their genome, calculated over time for each species. The average was approximately 45 percent

Overall, they concluded that “considering the wide-ranging effects that TEs impose on genomic architecture, these data are an important resource for future inquiries into mammalian genomics and evolution and suggest avenues for continued study of these important yet understudied genomic denizens.”

In the Molecular Biology and Evolution paper, novel statistical approaches to determining genome sequences in bats developed by Dávalos were used by the authors to describe the place bats hold with regard to TEs in mammals.

According to the lead author, Nicole Paulat, a graduate student in the Ray Lab, the research team found bats uniquely have more events involving TE transfers from one species to another. One mechanism that may explain such excess transfers is through viruses, an important finding on how several bat species have been found to host diverse and sometimes dangerous viruses.

Both papers based on the work from the Zoonomia Project illustrate that TEs are highly active across the genome of most mammal species, and because of this, future studies centering on TEs may help provide answers to mammalian biodiversity worldwide. Such research may also provide further hints as to how and why TEs disrupt mammalian genomes, therefore changing DNA and contributing to evolutionary processes and/or the development of disease.

The Brown Mouse Lemur (Microcebus rufus) is recognized as a vulnerable species on Madagascar. Photo by Chien C. Lee

A new study by a team of international scientists including Liliana M. Dávalos, PhD, of Stony Brook University’s Department of Ecology and Evolution, reveals that it would take three million years to recover the number of species that went extinct from human activity on Madagascar. Published in Nature Communications, the study also projects that if currently threatened species go extinct on Madagascar, recovering them would take more than 20 million years – much longer than what has previously been found on any other island archipelago in the world.

From unique baobab species to lemurs, the island of Madagascar is one of the world’s most important biodiversity hotspots. Approximately 90 percent of its species of plants and animals are found nowhere else. After humans settled on the island about 2,500 years ago, Madagascar experienced many extinctions, including giant lemurs, elephant birds and dwarf hippos.

Yet unlike most islands, Madagascar’s fauna is still relatively intact. Over two hundred species of mammals still survive on the island, including unique species such as the fossa and the ring-tailed lemur. Alarmingly, over half of these species are threatened with extinction, primarily from habitat transformation for agriculture. How much has human activity perturbed Madagascar away from its past state, and what is at stake if environmental change continues?

The team of biologists and paleontologists from Europe, Madagascar and the United States set out to answer this question by building an unprecedented new dataset describing the evolutionary relationships of all species of mammals that were present on Madagascar at the time that humans colonized the island.

As a co-author of “The macroevolutionary impact of recent and imminent mammal extinctions on Madagascar,” Daválos helped design the study, interpret a previously published lemur phylogeny, and analyzed prospects for new species discovery in Madagascar.

The dataset includes species that have already gone extinct and are only known from fossils, as well as all living species of Malagasy mammals. The researchers identified 249 species in total, 30 of which already are extinct. Over 120 of the 219 species of mammals that remain on the island today are currently classified as threatened with extinction by the IUCN Red List, due to habitat destruction, climate change and hunting.

Using a computer simulation model based on island biogeography theory, the team, led by Nathan Michielsen and Luis Valente from the University of Groningen (Netherlands) and Naturalis Biodiversity Center (Netherlands) found that it would take approximately three million years to regain the number of mammal species that were lost from Madagascar in the time since humans arrived.

The research team also determined through the computer simulation that if currently threatened species go extinct, it would take much longer: about 23 million years of evolution would be needed to recover the same number of species. Just in the last decade, this figure has increased by several million years, as human impact on the island continues to grow.

The amount of  time it would take to recover this mammalian diversity surprised the international team of scientists.

“These staggering results highlight the importance of effective conservation efforts in Madagascar. Here at Stony Brook, we can have an extraordinary impact on preventing extinction because of the longstanding biological field research at Centre ValBio and the associated Ranomafana National Park, with ongoing research on conservation while enhancing local livelihoods,” said Dávalos.

“It was already known that Madagascar was a hotspot of biodiversity, but this new research puts into context just how valuable this diversity is,” says leading researcher Luis Valente, Assistant Professor at the University of Groningen. “The time it would take to recover this diversity is much longer than what previous studies have found on other islands, such as New Zealand or in the Caribbean.”

The study findings ultimately suggest that an extinction wave with deep evolutionary impact is imminent on Madagascar, unless immediate conservation actions are taken. The good news – the computer simulation model shows that with adequate conservation action, we may still preserve over 20 million years of unique evolutionary history on the island.

 

Sloths, rodents and primates – some of the largest and smallest mammals on Caribbean islands – are among those most vulnerable to extinction. Image from David Rini, Johns Hopkins University

A new study by a team of international scientists jointly led by Stony Brook University Professor Liliana M. Dávalos, PhD, and Professor Samuel Turvey of the Zoological Society of London, reveals that the largest and smallest mammals in the Caribbean have been the most vulnerable to extinction. The findings, published in the Proceedings of the Royal Society B, help predict future extinction risk and inform the conservation strategies needed to prevent future biodiversity loss.

Most past studies find that larger mammals go extinct more often, so this study’s findings are unusual. Titled “Where the Wild Things Were,” the paper looked at past extinction patterns across the Caribbean mammal fauna in order to help scientists understand the factors that predispose species to extinction. With mammal extinction, what they found is that size does indeed matter in life.

The islands of the Caribbean have long been a source of fascination for scientists and conservationists. They were once home to a diverse array of land mammals including sloths, primates, unusual insectivores, and giant rodents, but the arrival of different waves of human colonists from around 6000 years ago onwards instigated the largest series of human-caused mammal extinctions since the end of the last Ice Age.

Only 11 native Caribbean rodents and two insectivores still survive today – including the two solenodons, large shrew-like mammals that have the unique ability to inject venom into their prey using modified grooved teeth. Both solenodon species are the only representatives of an ancient mammalian lineage that diverged from the ancestors of all other living mammals during the time of the dinosaurs, approximately 76 million years ago.

Dávalos, a Professor in the Department of Ecology and Evolution in the College of Arts and Sciences, designed and completed the statistical analyses that led to the findings. By carrying out the study at the level of mammal populations instead of species, the team’s methods were able to account for the effect of varying environmental conditions across different islands on species’ chances of survival.

Conducting a huge-scale analysis that included records of extinction patterns for 219 land mammal populations across 118 Caribbean islands, the study went beyond previous research into Caribbean mammal extinctions, which has largely focused on reconstructing last-occurrence dates for extinct species and matching them with specific historical events. This study instead sought to identify wider ecological patterns – such as the relationship between body mass and extinction risk – that influence a mammal’s chance of survival in response to human activities.

They found that medium-sized Caribbean mammals – like the solenodons – have been less sensitive to extinction compared to both their smaller and larger counterparts.

According to Dávalos and co-authors, this overall discovery is likely to reflect the fact that larger species were more vulnerable to past human hunting, whereas smaller species were more vulnerable to predation or competition by introduced species such as mongooses and rats.

“To answer questions such as ‘what traits predispose species to survival?’ Or ‘what island features are associated with extinction?,’ we studied each population on an island as a natural experiment,” says Dávalos. “With enough of them, patterns that have often been discussed but couldn’t quantify start to emerge. Without the large database of many natural experiments in the Caribbean and powerful computing approaches, there is no way to answer these questions.

“The analyses also showed that Caribbean mammals of all sizes were less likely to survive on the earliest-colonized islands by humans and more likely to survive on tiny, low-elevation offshore islands, meaning that their future survival could be at risk from climate change and rising sea levels unless measures are put in place to protect these vital natural refuges.”

“Preventing the extinction of highly endangered species requires an awareness of not only the immediate risks to their survival, but also the history of human-caused biodiversity loss – and the unique insights that the past can provide about species’ vulnerability or resilience under differing conditions,” adds Professor Samuel Turvey of ZSL’s Institute of Zoology.

“The Caribbean islands are home to unique mammalian biodiversity, which has tragically been almost completely wiped out by past human activities. Our study clearly highlights the importance of learning from the past to make the future better – we must use information from the historical, archaeological and recent fossil records to inform current-day conservation, or else we risk losing these remarkable species forever.”

Research for this study was supported in part by the National Science Foundation (NSF). For Professor Dávalos, grant numbers DEB 1442142 and 1838273, DGE 1633299. Additional funding by the NSF (OAC 1531492) enabled analyses by the SeaWulf computing system at the Institute for Advanced Computational Science at Stony Brook University.