[vc_row][vc_column][vc_column_text]February 10, 2020
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[vc_row][vc_column][vc_column_text]February 10, 2020
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[vc_row][vc_column][vc_column_text]From VT News | February 6, 2020
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[vc_row][vc_column][vc_column_text]From VT News | February 5, 2020
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[vc_row][vc_column][vc_column_text]From VT News | December 2, 2019
More than half of America’s national parks are facing a grave and immediate threat: the ongoing presence and spread of invasive animal species. The National Park Service has taken the first step in combatting this invasion by asking a group of experts to help chart a course that will ensure the survival of these national treasures.
The experts’ findings were recently published in the journal Biological Invasions. According to lead author Ashley Dayer, assistant professor of wildlife conservation in the College of Natural Resources and Environment, “As Americans, we value national parks for the natural habitats and wildlife they protect, but because of invasive species, some of our native species are struggling or unable to survive, even with the protection of our park system.”
More invaders are likely to arrive and flourish because, currently, the National Park Service has no comprehensive program to reverse or halt the trend. Coordinated action and a financial commitment by the NPS and others will be critical. According to Dayer, “If we don’t take action, native species will continue to struggle due to the invasives. But taking action is no small feat; it requires the commitment and resources of the National Park Service, neighboring lands, and the public.”
Dayer received the opportunity to address this complex problem when she accepted an invitation from the National Park Service to serve on a panel of experts to address the threat of invasive animal species and suggest solutions. As a conservation social scientist, her work in the Department of Fish and Wildlife Conservationfocuses on understanding how to best engage people in wildlife conservation issues. Other panelists were selected for their expertise in such areas as parks management, invasive species management, emerging technologies, economics, or decision support.
As to why the agency chose this particular time to act and form the panel, Elaine Leslie, former chief of the NPS Biological Resource Management Division, said, “The NPS is very concerned about nonnative and invasive species across the landscape within and outside of national park units and their impacts on native biodiversity, especially at-risk species and their habitats. . . . Nationally and internationally, the world is losing native biodiversity at an alarming rate. Threats from invasive species play a critical part in this loss.”
Dayer and the team of experts have been grappling with this complex issue for three years. Their primary finding is that the presence of invasive animals undermines the mission of the NPS. These invaders can cause the loss of park wildlife, lessen visitors’ enjoyment of parks, introduce diseases, and have huge economic impacts due to the cost of control measures.
Yet invasive animal species can be found in more than half of all national parks. Of the 1,409 reported populations of 311 invasive animal species in national parks, there are management plans for 23 percent and only 11 percent are being contained. The invaders include mammals, such as rats, cats, and feral pigs; aquatic species like lake trout and the quagga mussel; and reptiles, including the Burmese python.
Everglades National Park has been well-known for its invasive animal issues since pythons were found to be thriving and reproducing there in 2000. Local and national media, as well as documentary producers, quickly found an audience in the general public for their works featuring these snakes, which can reach up to 23 feet in length. Researchers have also been attentive to what is happening in the Everglades, reporting huge declines in native mammals like raccoons and opossums.
In Virginia, the hemlock woolly adelgid has infested hemlocks along the Blue Ridge Parkway and in Shenandoah National Park. Hemlocks help maintain the cool habitats needed by other species to thrive, such as native trout. Although hemlocks can live up to 600 years, a woolly adelgid infestation can kill a tree in just three to 10 years.
The second finding of the panel is that coordinated action is required to meet the challenge of invasive species. The four additional findings carry the same mandate for collaboration: partnering is essential for success; public engagement, cooperation, and support are critical; decision support across all levels must be strategic; and emerging technologies, when appropriately used, would be beneficial.
According to Mark Schwartz, a fellow panelist and professor of conservation science at the University of California–Davis, it is the complex nature of this problem that calls for such a coordinated and widespread effort. “Our national parks face a suite of wicked management problems, with the invasive species standing out for the sheer diversity of species, the geographic spread of their impact, the magnitude of the threat, and the complexity of solutions.”
Both Schwartz and Dayer, as well as their other panelists, agree not only that national coordination is the way forward, but also that this will be a major challenge, an idea that is expressed in their findings. Schwartz said, “In addition to national coordination on invasive animals, a better means to fully integrate managing invasive animals across the full suite of challenges facing individual parks is needed.”
Organizational change is possible, Dayer believes. As an affiliate of the Global Change Center housed in Virginia Tech’s Fralin Life Sciences Institute, she sees good examples of progress through cross-jurisdictional efforts like the National Invasive Species Council and the Invasive Species Advisory Committee, as well as through regional collaborations that have engaged national park units.
Schwartz also sees promise in some recent park successes: “After a false start, Yellowstone regrouped, sought broad public input, and now has an effective program to manage invasive lake trout. Working with the Everglades Cooperative Invasive Species Management Area, the NPS has coordinated with other agencies, tribes, and private parties to control the invasive sacred ibis. More such collaborative efforts are needed.”
Elaine Leslie believes that a coordinated effort as well as additional funding will be critical to success. “This issue is also one of economic importance,” she stressed. “If we can take national steps, as other countries have, to prevent and eradicate invasive species, we can make a difference — but it has to be a priority and well-coordinated.”
Another important group of people that is referenced in the findings and could pave the way for long-lasting change is the public. “The public can play a key role in helping the parks detect or remove invasive species, pushing for new governmental policies and funding allocations, or assisting through philanthropy efforts,” Dayer said. “In order to make headway, it is critical that the people of the U.S. are engaged fully in determining and implementing the solution to this challenge.”
Along with the other panelists, Dayer will continue to tackle this complex issue by making sure that the findings are disseminated, promoting action from the NPS, and encouraging people to buy into and participate in efforts to protect our national parks. All of this matters because, as she firmly states, “The national parks are not the National Park Service’s parks; they belong to the U.S. public and serve as conservation models nationally and internationally.”
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From VT News | October 31, 2019
Bats flying through the inside of a house might conjure up visions of a Halloween movie — or even a sitcom.
Just two weeks ago, Alexa Briehl, communications director for Operations at Virginia Tech, was just beginning to fall asleep when four bats descended through the master bathroom vent from the attic and began to flutter about her bedroom and home.
Unsure what to do about the flying creatures flickering from room to room, Briehl and her husband reached out to friend, neighbor, and fellow Virginia Tech communications director Kristin Rose Jutras and her husband, Virginia Tech assistant professor Brandon Jutras, who knew just what to do.
They put out the bat signal to Kate Langwig and Joe Hoyt, both assistant professors in the Department of Biological Sciences in the College of Science. Langwig and Hoyt’s research focuses on endangered bats and the proliferation of the fungal disease white nose syndrome in bats.
According to the Virginia Department of Game and Inland Fisheries, three species of bats are endangered in Virginia and 12 are nongame protected species in Virginia. Also,“it is illegal to transport, release, or relocate a bat anywhere other than the property it was caught on.”
Langwig and Hoyt walked Briehl and Rose Jutras through a humane step-by-step process for catching and releasing the bats. “First, open windows and try to encourage them to leave with a soft towel. Otherwise, you can safely catch them with a soft, thick towel, or handle them directly with thick leather gloves like fireplace gloves,” said Langwig, who is also an affiliated faculty member of the Global Change Center.
Bats are nighttime insect predators that can greatly benefit agriculture, but their populations are being decimated by white-nose syndrome.
“Little brown bats were not an uncommon species prior to the emergence of white-nose disease. It would be like losing robins from the bird community. These are abundant backyard species that you would see at nighttime that have essentially been removed,” Hoyt said.
In a relatively new discovery, Hoyt and researchers found in a field trial that probiotic bacteria could be used to reduce wildlife disease and conserve biodiversity. They found that it reduces the impact of the disease about five-fold. These findings were published recently in Scientific Reports.
“Bats are surrounded by myths and folklore that date back centuries, and are always a focal point this time of year,” said William Hopkins, director of the Global Change Center, housed within the Fralin Life Sciences Institute. “The reality is that the world would be very unpleasant for people if bats weren’t around. Many bat species regulate populations of biting insects and agricultural insect pests, thus providing economic and human health benefits as well as reducing our need for damaging pesticides. In addition, other bats are important pollinators of plants around the globe. The more we can learn to coexist with bats, the better off we will be. The research conducted by Drs. Langwig and Hoyt represents an enormous step towards protecting these critically important species.”
And the bats won’t be too far away after all. They have a new home in a bat “condo” in the Briehls yard.
Installing a bat condo, or “bat box” as they are often called, is just one way to help reduce humans’ impact on the bat population. Other ways include protecting waterways and changing landscaping to provide insects for bats. To learn more about how you can help the bats and build your own bat box, read here.
–Written by Alexa Briehl and Kristin Rose Jutras
Related stories:
Researchers find that probiotic bacteria reduces the impact of white-nose syndrome in bats
Virginia Tech researchers receive $2.9 million grant with China to study infectious diseases
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CONTACT:
Kristin Rose (540) 231-6614
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Header image: College of Science researchers Kate Langwig (left) and Joseph Hoyt (right) received a grant to understand the long-term host and pathogen dynamics of white-nose syndrome in bats.
VT NEWS | August 14, 2019
Sometimes, scientists have to look to the past to better understand the present.
Researchers from the Department of Biological Sciences in the College of Science received a $2.9 million dollar award from the National Science Foundation (NSF) and the National Natural Science Foundation of China (NSFC) to understand the long-term host and pathogen dynamics of white-nose syndrome in bats. If all goes according to plan, their research will provide implications for other diseases as well.
Kate Langwig, an assistant professor, and Joseph Hoyt, a research scientist, are combining their respective specialties in infectious disease ecology with a focus on past and present disease patterns to find out how some hosts and pathogens can coexist, particularly after a host has already seen a massive decline from disease.
Langwig and Hoyt are collaborating with Chinese researchers to examine how the pathogen that is responsible for white-nose syndrome has affected bats across both time and space, and whether there are similar or different mechanisms that bats use to survive with this deadly disease.
White-nose syndrome is a fungal disease that spreads in the winter and causes lesions in the wings of bats during hibernation, setting off a cascade of physiological consequences that eventually lead to death. Since 2005, the fungus that causes white-nose syndrome, Pseudogymnoascus destructans, has killed millions of bats, causing bat population declines of 70 to 100 percent across multiple bat species in eastern North America.
However, researchers have noticed that, of the few remaining populations, some bats are less affected by the devastation, and they want to know why.
“Some of the major questions that we are trying to understand are ‘Is it the bats that are special? Or is it the environment that they inhabit? Or is it some combination of the two?’ If it is the bats that are special, it means that you could take individuals from these surviving populations and repopulate areas like Virginia, which has been really hard hit by white-nose syndrome,” said Langwig, who is also an affiliated faculty member of the Global Change Center.
Hoyt’s previous research has provided evidence that the fungus likely emerged in Eastern Asia tens of thousands of years ago and then spread to Europe thousands of years ago. It was likely introduced to northeastern North America in 2005.
One of the novel components of their research is that they are focusing on bat populations in Eurasia, which have survived with white-nose syndrome for millennia, to make their predictions about coexistence and the survival of bat populations.
“We are not just looking in areas where the disease has already caused impacts in North America and trying to understand the process of coexistence in our bat populations here, but we are actually trying to look at an area where that coexistence has already been reached – in Europe and Asia,” said Hoyt. “Can we draw some inference from these long-term dynamics to understand what our bat populations will look like in the future?”
In order to fine-tune their predictions about the future of white-nose syndrome afflicted bats, Langwig is building a mathematical integral projection model, a hybrid between an individually based model and a population model, which will allow researchers to make better predictions about disease dynamics.
She hopes that her modeling framework, combined with the experimental, observational, and genomic components of the project, can be applied to understand how hosts and pathogens are coexisting in other disease systems.
Both Langwig and Hoyt say that a large component of the grant is to identify the long-term effects of this disease on different bat populations, and if what we are seeing now in North America are actually long-term or short-term adaptations that will change in the future.
“If we see that this fungus is impacting populations in Eurasia, then it’s probably something that North American bats are going to face for a long time,” said Langwig.
This grant is an example of history in the making. This grant was the first time that this joint NSF, NIH, and USDA program has collaborated with NSFC.
In addition to Hoyt and Langwig, who are both affiliated faculty members of the Fralin Life Sciences Institute, the co-principal investigators of this project include Jiang Feng and Keping Sun from Northeast Normal University in China, Jeff Foster from Northern Arizona University, and Beth Shapiro and A. Marm Kilpatrick from the University of California Santa Cruz.
Langwig and Hoyt were hired as part of the Global Systems Science Destination Area in the College of Science at Virginia Tech to address issues of infectious disease. The Global Systems Science Destination Area is focused on understanding and finding solutions to critical problems associated with human activity and environmental change that together affect diseases states, water quality, and food production.
~ Written by Kendall Daniels
Related Article: https://vtnews.vt.edu/articles/2019/06/062419-FLSI-bats-white-nose-syndrome.html
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Interfaces of Global Change graduate students hosted a science outreach day at 2351 Glade Road in Blacksburg, VA. The afternoon exhibition titled “Backyard Biodiversity Bonanza” focused on sharing information with the public for promoting biodiversity conservation for birds, bees and native plants in backyard habitats.
IGC Fellow, Ben Vernasco, spearheaded the planning for the outreach event. He shared information about bird houses, the types of boxes that can be built (wood duck, bluebird/chickadee/tree swallow, owl boxes) and examples of building plans. Bird coloring sheets for kids were available as handouts, in addition to information about common yard birds and tips to promote nesting. IGC Fellow, Jessica Hernandez, was also on-site to talk about her research with tree swallows, with nest boxes on display!
IGC Fellow and IGC GSO Outreach Committee Chair, Vasiliy Lakoba, led a table featuring native plants beneficial to wildlife and pollinators. This included a hands-on comparison display of commonly planted non-natives along with great native plant alternatives for landscaping around the home and town. Free sunflower seedlings were also available for participants to take home!
Chris McCullough, a graduate student in VT’s School of Plant and Environmental Sciences, provided information about pollinator conservation. A bee collection display allowed participants to see different types of bees up close, and there was also a bee house to check out.
Kudos to these students for sharing both their science and conservation stewardship information with the local community!! [/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_raw_html]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[/vc_raw_html][/vc_column][/vc_row][vc_row][vc_column][vc_separator][/vc_column][/vc_row]
[vc_row][vc_column][vc_column_text]From VT News
Cover image: McMurdo Dry Valleys in Antarctica. Image Credit: McMurdo Dry Valleys LTER.
Antarctica is a nearly uninhabited, ice-covered continent ravaged by cold, windy, and dry conditions. Virginia Tech researcher and GCC faculty affiliate Jeb Barrett was part of an international collaborative team that analyzed biodiversity patterns in the McMurdo Dry Valleys of Antarctica.
“Surprisingly, we found that biotic, or living, interactions are crucial in shaping biodiversity patterns even in the extreme ecosystems of the Antarctic Dry Valleys. Antarctic soils are model ecosystems, limited by the extreme climate and lack of vascular plants, and they host simple food webs with few species,” said Barrett, professor in the Department of Biological Sciences in the College of Science.
These findings were recently published in two separate papers in Communications Biology. A paper on biotic interactions analyzes the entire community of soil organisms; its companion paperfocuses on the soil nematode community using a modeling approach.
Characteristics of Antarctic communities, such as simple food webs and low species richness, allow for a greater understanding of the whole community, from bacteria to multicellular invertebrates.
This research is the product of an international collaboration of scientists from half a dozen countries: the United States, New Zealand, Canada, Australia, Great Britain, and South Africa. Organized by the University of Waikato and the New Zealand Antarctic Program, it is the first of its kind to study a soil community in its entirety at a regional scale.
Barrett has been conducting research in Antarctica for 20 years; he deployed for this research collaboration in 2009 and 2010. Research in the Barrett lab addresses the influences of soils, climate variability, hydrology, and biodiversity on biogeochemical cycling from the scale of microorganisms to regional landscapes.
“My research in the Antarctic has been focused on analyzing the physical and geochemical drivers that predict biodiversity patterns. I focused initially on the nematode communities, and my work has now expanded into the bacterial communities, as well,” said Barrett, an affiliated faculty member of the Global Change Center, housed within the Fralin Life Science Institute.
The Communications Biology paper on biotic interactions considers the entire community of soil organisms: cyanobacteria, heterotrophic bacteria, nematodes, and other microscopic invertebrates. The scientists studied the factors that determine the distribution and abundance of these organisms, as well as temperature, topography, distance to the coast, and soil properties, such as water and pH levels, in their analysis.
“What makes this paper truly unique is that we considered the entire community of soil organisms and all the possible biotic and abiotic interactions that potentially shape the species composition and diversity,” said Barrett. “We used the statistical technique of structural equation modeling to tease out what the drivers of these communities are.”
Biogeochemistry and climate have strong effects on biodiversity, but this new data demonstrated that there are two other important factors. They found that biogeography and species interactions are stronger drivers of biodiversity than originally expected. Biogeographic processes occur when an organism moves through space, interacting with its community as it moves. Species interactions, such as predator-prey relationships and competition, also influence biodiversity.
In the companion paper, the researchers used a modeling approach to study the co-occurrence and distribution of three dominant nematode species found in the soil. Nematodes, also known as roundworms, are a group of simple organisms that have successfully adapted to nearly every ecosystem on Earth. The researchers demonstrated that competition is a more important driver of diversity patterns in the nematode community than previously thought.
“We modeled three nematode species – Plectus, Scottnema, and Eurdoylaimus – that are potentially interacting. Our results show that it is not just environmental drivers that influence species distribution across the polar landscape but that competition and interactions are playing a large role in diversity patterns as well,” said Barrett.
The future challenge for researchers is to understand how the effects of climate change on these interactions will alter species coexistence in Antarctica. They expect that with increasing temperatures, the thawing of ice will create environments that select for nematode species more adapted to warmer and wetter environments. Early indications of this have already been observed in the team’s long-term monitoring studies of soil communities, as reported in the journal Ecology last year.
Barrett’s ongoing research is funded by the National Science Foundation’s Long Term Ecological Research (LTER) Program. His research goal with the LTER is to use a combination of manipulative experiments and long-term observations to understand how climate variability influences Antarctic organisms and ecosystems.
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Jeb Barrett’s research shows that extreme melt restructured the invertebrate ecosystem in Antarctica
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Biodiversity is more than the number of species on Earth. It is also the amount of unique evolutionary history in the tree of life. We find that losses of this phylogenetic diversity (PD) are disproportionally large in mammals compared with the number of species that have recently gone extinct. This lost PD can only be restored with time as lineages evolve and create new evolutionary history. Without coordinated conservation, it will likely take millions of years for mammals to naturally recover from the biodiversity losses they are predicted to endure over the next 50 y. However, by prioritizing PD in conservation, we could potentially save billions of years of unique evolutionary history and the important ecological functions they may represent.
The incipient sixth mass extinction that started in the Late Pleistocene has already erased over 300 mammal species and, with them, more than 2.5 billion y of unique evolutionary history. At the global scale, this lost phylogenetic diversity (PD) can only be restored with time as lineages evolve and create new evolutionary history. Given the increasing rate of extinctions however, can mammals evolve fast enough to recover their lost PD on a human time scale? We use a birth–death tree framework to show that even if extinction rates slow to preanthropogenic background levels, recovery of lost PD will likely take millions of years. These findings emphasize the severity of the potential sixth mass extinction and the need to avoid the loss of unique evolutionary history now.
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As we enter a potential sixth mass extinction (1), triaging species and prioritizing limited conservation funds grow increasingly urgent if we wish to preserve biodiversity (2). However, taxonomic species richness (SR), the most used metric for measuring biodiversity among researchers, governments, and managers, is insufficient for these purposes because it implicitly treats all species equally (3). Functional diversity (FD), a richer metric that captures species’ ecological adaptations and contributions to ecosystem function is growing in popularity, but it is difficult to measure and hard to compare between different taxonomic groups (2⇓–4). Phylogenetic diversity (PD), the amount of independent evolution within a phylogeny (5), is a complementary metric that measures lineage history and may be correlated to functional trait diversity and evolutionary potential (4, 6, 7, but cf. ref. 8). PD is generally considered a better metric of biodiversity than SR because it incorporates both SR and phylogeny, is less influenced by arbitrary taxonomic decisions, and provides a powerful metaphor of “national heritage” for conservationists (5, 9). Furthermore, unlike FD index values, which are relative to each idiosyncratic analysis, PD is typically measured in millions of years of independent evolution (the sum of all branch lengths connecting a set of species to the root of their phylogenetic tree), a meaningful common currency that allows comparisons across a wide range of taxa and studies (2, 5). It is difficult to understand and measure the FD contribution of every species in a community, but with the rapid advancement of environmental DNA methods and computational capabilities, we could potentially place all those species on the tree of life to measure their contribution to PD (6, 10).
The incipient sixth mass extinction that started during the Late Pleistocene has been diagnosed by extremely elevated modern extinction rates compared with background levels (1). However, one can also put our current biodiversity crisis in perspective by estimating the time necessary for global diversity to recover to a preanthropogenic state (11). Although regional losses in biodiversity might be lessened by restoration activities such as species reintroductions and rewilding (12), at the global scale, lost PD can only be restored by time as species evolve and create new evolutionary history. For example, although as few as 500 individuals of the critically endangered (CR) pygmy sloth (Bradypus pygmaeus) remain (13), global PD would recover from the extinction of this species in less than 2 y (11). This is not to say that a new species of pygmy sloth would evolve within this time or that the sloth’s ecological functions would be restored, but that the 8,900-y loss in unique evolutionary history brought about by the sloth’s extinction could be countered simply by all 5,418 remaining mammal species existing, and hence evolving, for an additional 1.64 y. The pygmy sloth, however, is one of the youngest mammal species, splitting from its congener during a vicariance event in the Holocene. The extinction of the aardvark (Orycteropus afer) would cause a much larger drop in PD, over 75 My, because the aardvark is the sole representative of an entire order. Such deep cuts into the mammal tree are increasingly likely, given that over one-fifth of current mammal species are threatened with extinction (14). How much PD will mammals lose during the ongoing sixth mass extinction, and can they recover this lost biodiversity?
We randomly sampled 30 phylogenies from the posterior distribution reported by Faurby (15), which includes all extant and extinct Late Quaternary mammal species. Combining these trees and ranked threat statuses from the International Union for the Conservation of Nature (IUCN), we calculated the loss of PD since the Last Interglacial (∼130,000 y ago) and the expected loss of PD, given probabilities that currently threatened species will go extinct in the near future (16). Unlike most previous studies, here, we use the Last Interglacial as a baseline instead of the present day because it better represents the typical, megafauna-rich state that existed through much of the Cenozoic (17). Leaving prehistoric extinctions out of analyses undercounts biodiversity loss and ignores the many large impacts these extinctions have had on modern ecology (17). To put global PD losses in perspective compared with species losses, we randomly shuffled species’ IUCN statuses 250 times so that taxonomic losses during simulated extinctions were of the same severity but random with respect to phylogeny (SI Appendix).
Several unique mammal lineages (notably the endemic South American orders Litopterna and Notoungulata) were completely lost during the likely human-linked extinctions of the terminal Pleistocene and early Holocene (18). These extinctions also decimated the sloth and anteater, armadillo, odd-toed ungulate, and elephant lineages, all disproportionately rich in PD (Fig. 1 and SI Appendix, Fig. S1). Human-linked prehistoric extinctions saddled global mammal diversity with a PD loss of 2 billion y of unique evolutionary history. Historic extinctions since 1500 CE caused an additional 500 My of loss, leaving PD levels far worse than expected, given null expectations of random extinctions (Fig. 2 and SI Appendix, Table S1). This is partly because prehistoric and historic extinctions were highly size-biased (19), devastating large mammals (SI Appendix, Fig. S2), a group shouldering a disproportionate share of PD. Evolutionary history has its own intrinsic value (20), but these lost years also represent a loss of instrumental value in the extinction of unique functional traits (2, 10). Human-linked extinctions have already left the world in an atypical state: depauperate of large animals and the important ecosystem functions and services they provide (17).
If current lineages simply persisted without any new speciation or extinction, it would take nearly 500,000 y for the ∼5,400 current mammal species to evolve enough new history to restore net PD to preanthropogenic levels. But there will be new extinctions. The IUCN’s own definitions for ranks predict the loss of 99.9% of CR species and 67% of endangered species within the next 100 y (16), eliminating even more ecosystem functions and services and further increasing mammals’ already large PD debt. At the same time, mammals will also continue to diversify; if every lineage speciated into two distinct lineages, PD could be restored in half the time. The larger the speciation rate (λ) is compared with the extinction rate (μ), the shorter the amount of time (t) that it will take for mammals to naturally evolve back their lost PD. Given realistic background speciation and extinction rates, how long would it take mammals to regain this evolutionary history? Put another way, given a human time scale, can mammals evolve fast enough to recover from the sixth mass extinction?
We considered a “best-case” counterfactual model where the average global extinction rate drops down to background levels (21) before mammals are allowed to recover and start evolving new evolutionary history (Fig. 3). This could happen either because of a massive, global paradigm shift toward increased conservation efforts or because human populations have somehow collapsed to a point at which we are no longer a dominant and threatening ecological force. Using extinction probabilities extrapolated from IUCN definitions (16), we examined five scenarios for when PD was allowed to recover. Mammals could start recovering immediately or after 20, 50, or 100 y of status quo conservation efforts. If they started recovering immediately, only the PD lost during historic and prehistoric extinctions would need to be recovered. However, if mammals were not allowed to recover until sometime in the future, there would be a large chance that many extant species would also go extinct (SI Appendix, Table S2), creating even more lost PD compared with the baseline of all species alive at the Last Interglacial. To determine how large of an effect prehistoric extinctions had (18, 22), we also measured what would happen if mammals were allowed to recover from a 1499 CE baseline (i.e., before any “historic” or potential future extinctions). Using a birth–death tree framework (23) and a range of preanthropogenic background extinction rates (21), we then determined the speciation rate necessary to generate enough new PD through the evolution of new branch lengths to equal the PD lost during prehistoric and historic extinctions and potential future extinctions (Fig. 3 and SI Appendix).
Although PD losses may be highly variable across clades and regions, previous studies predict that, globally, expected mammal PD losses should not be disproportionally severe (24⇓–26, but cf. ref. 27 in which disproportionate losses of higher taxonomic units, although not necessarily PD, are predicted). Phylogenetic traits like lineage age, lineage richness, and evolutionary distinctiveness (ED) show no significant relationships with extinction risk (28), and simulations suggest that even though extinctions may be highly phylogenetically clustered (29), this is not enough to cause large losses in PD (30). However, when considering a baseline of the Last Interglacial, we found that global PD losses were much worse than expected (Fig. 2 and SI Appendix, Table S1), although losses did vary greatly across different taxonomic groups (SI Appendix, Fig. S3). Although extinction risk did not show a strong phylogenetic signal in our data, species that went extinct prehistorically (before 1500 CE) were significantly larger, older, and more evolutionarily distinct than other species (SI Appendix, Figs. S2, S4, and S5). Considering only terrestrial species, extinct megafauna (≥45 kg) were, on average, 48% older than surviving species and 61% more evolutionarily distinct. This is partly just a function of size, but even among large terrestrial mammals, extinct megafauna stood out. On average, they were 49% older and 57% more evolutionarily distinct than surviving megafauna. This means that prehistoric and historic extinctions were close to worst-case scenarios for PD loss, as many of the most phylogenetically distinct species were lost first, a pattern that has little analog in the fossil record (31). Even when excluding the strong effect of these extinct species by using the present day as a baseline like previous studies (24⇓–26), we still found disproportionate (albeit much smaller) losses in PD compared with SR in 14 of the 30 phylogenetic trees examined (SI Appendix, Fig. S6 and Table S5).
If the status quo of mammal conservation continues for 50 y before mammals are allowed to recover, speciating and going extinct at their average preanthropogenic background rates of λ = 0.276 and μ = 0.272 (roughly, one to two extinctions per 1,000 y) (21), it would take 5–7 My to restore the PD debt from prehistoric and historic extinctions (Fig. 4 and SI Appendix, Fig. S7). Even if background extinction rates effectively slowed to a stop (μ = 0), speciation rates in mammals would still have to be about twice as high as their highest levels during the Cenozoic to restore PD debt within 500,000 y. Rates this high would mean that all mammals on Earth would have to speciate as fast as the Lake Victoria and Lake Malawi cichlids (32), the textbook vertebrate clade for extremely rapid evolution, without a single lineage going extinct. These high rates are not merely due to using the Late Pleistocene as a baseline. Of the 4,280 My of total PD debt we expect to have accrued after 50 y of status quo conservation, less than 60% comes from historic (509 My) and prehistoric (1,995 My) extinctions. Speciation rates and recovery times would still be excessive using the modern day as a baseline by completely ignoring historic and prehistoric extinctions (SI Appendix, Fig. S8). If the extinction rate fell to its average preanthropogenic level (μ = 0.272), mammals would have to speciate faster than their highest Cenozoic rate (21) (λ = 0.969) for 1 My just to restore the amount of evolutionary history we are expected to lose in the next five decades (SI Appendix, Fig. S8). More realistically, average preanthropogenic speciation rates suggest a recovery time of 3–5 My (SI Appendix, Fig. S8).
Functional recovery from the sixth mass extinction would likely take even longer than PD recovery. We estimated mass distributions of future mammals using simulated birth–death trees and a neutral Brownian motion model of evolution on log-transformed weight with rates conditioned on the full trees (Fig. 4B). Currently, median mammal body mass (72.7 g) is 14% lower than its preanthropogenic level of 84.3 g. Stopping extinctions right now (μ = 0) could restore PD within 500,000 y, given a very high speciation rate (SI Appendix, Fig. S7), but it would still take 4–5 My before median body mass returned to its pre-Pleistocene extinction level (SI Appendix, Fig. S9). If all extinctions stopped 50 y from now, it could take over 7 My for body sizes to recover (SI Appendix, Fig. S9). Although Faith (5) originally developed PD as a measure of the total number of features in an assemblage, PD is now often implicitly treated as equivalent to the range of trait values in an assemblage (33, 34) (i.e., functional richness, a component of FD). Prioritizing PD is generally a reasonable method for conserving FD (4), but restoring one does not always restore the other (24, 33, 35). This is partly because, even if traits are perfectly phylogenetically conserved, not all evolutionary time is equal. For example, one could say that losing 500 My of PD is roughly equivalent to losing a monotypic phylum (27). However, because the expected variance of traits evolving through Brownian motion increases linearly with time, a 1-My-old clade with 500 species would have only 1/250th of the expected trait variance of a pair of sister species that split apart 250 Mya despite both clades having the same rate of trait evolution and representing 500 My of PD (36). Even if PD is equal, for trait diversity, recovery at short time scales and high speciation rates is not equivalent to recovery at long time scales and lower speciation rates. This means that given neutral evolution, the unique traits of threatened, phylogenetically isolated taxa (10) cannot be easily replaced by short, rapid bursts of speciation, greatly prolonging the time needed for full functional recovery.
Even recovering such a large amount of PD through a rapid burst of speciation is highly unlikely. This is made clear by examining the expected number of species generated if PD lost during prehistoric and historic extinctions and the next 50 y was restored (Fig. 4C). To generate this much PD within 500,000 y and with an average background extinction rate (μ = 0.272), new lineages would have to rapidly split, creating many functionally similar species on short branches. The world would have over 22,000 mammal species, 6,000 of them rats (Muroidea) (Fig. 4C). The existence of a strict carrying capacity for SR is debatable even at local scales (37); however, it seems unlikely that the globe could support almost fourfold the number of species that it harbored during the Late Pleistocene without some major geographical alterations. More reasonable speciation rates are likely those where the Earth maintains a taxonomic diversity close to its current level (λ ≈ 0.276), leading to a recovery time of 5–7 My. Even then, each order’s proportional contribution to global PD could change greatly in the future. After 50 y of status quo conservation, rodents are predicted to show a large increase in proportional PD. Bats, eulipotyphlans, carnivorans, opossums, rabbits and pikas, and hyraxes are expected to make smaller gains (SI Appendix, Fig. S10). All other orders are predicted to decrease in their proportional contribution to global PD. Primates and many Australasian marsupials could show large losses.
Is there any way to avoid the grim predictions of our model and speed recovery of PD and FD? The preferential extinction of older lineages seen in the Late Pleistocene and early Holocene is rare in the deeper fossil record (31), making mechanistic comparisons with past extinction events uncertain. Although the size bias of recent extinctions could lead to a “Lilliput effect” where small, surviving species rapidly evolve into vacant niches (38), the correlation between genetic substitution rates and high diversification rates necessary for this pattern have not been found in mammals (39). In general, mammals may not have the elevated speciation rates (21) shown by other taxa after mass extinctions (40). However, even with strong selection for mammals to fill vacant niche space, recovery times on the order of millions of years are probably realistic. The maximum body mass of terrestrial mammals took over 10 My to first evolve from horse-sized to elephant-sized (41).
The results reported here show that it is unlikely that mammals can evolve fast enough to restore their lost PD on any kind of time scale relevant to humans. Just the PD that mammals are expected to lose in the next few decades would realistically take millions of years to recover (SI Appendix, Fig. S8). Even after this PD recovery, FD (SI Appendix, Fig. S9) would likely remain highly altered for millions of years more. The lost evolutionary history from previous and ongoing extinctions is already affecting ecosystems (42), a trend that will likely only get worse. If anything, our grim predictions of long recovery times are conservative. Unlike our best-case scenario model, there is little reason to expect that humans will be able to bring extinction rates down to background levels within the next century with a rising human population and increasing anthropogenic climate change. The only real option to speed PD recovery is to save unique evolutionary history before it is already lost. In addition to increasing overall conservation efforts, we should use available PD methods to prioritize action for evolutionarily distinct species and dedicate more research to exploring PD’s relationship with FD and ecosystem services (4, 7). If we could momentarily stop extinctions for mammals, we would save as much evolutionary history in the next 100 y as what our ancestors lost in the last 100,000 y (SI Appendix, Table S1). Extinction is part of evolution, but the unnatural rapidity of current species losses forces us to address whether we are cutting off twigs or whole branches from the tree of life.
We developed a counterfactual model to investigate how fast current mammal species would have to evolve to replace the amount of evolutionary history they have already lost and are expected to lose during the ongoing sixth mass extinction. This model assumes a best-case scenario, where the average global extinction rate for mammals drops down to background levels (21) before they are allowed to recover and start evolving new evolutionary history (Fig. 3). Using a birth–death tree framework (23) and a combination of simulations and algebraic solutions, we iteratively determined the speciation rate (λ) necessary to recover lost PD with a given time span (t) and extinction rate (μ). Both λ and μ were measured in lineages per species per million years, and t was measured in millions of years.
Mammal phylogenies and body mass data came from a prerelease (version 1.1) of the PHYLACINE database (15). Average background diversification rates for mammals were from Alroy (21). Extinction probabilities for extant species were based on studies by Mooers et al. (16) and Isaac et al. (43). To partition expected PD (44) fairly among taxa, we developed a missing PD metric, expected ED, a probabilistic version of ED (45). To facilitate the use of the expected ED metric, we created an R package (“mallorn”) that can quickly calculate expected ED and expected PD (10.5281/zenodo.1286923, available at https://megapast2future.github.io). All analyses were carried out in R version 3.4 (46). Detailed information on data and methods is provided in SI Appendix. The complete data and code necessary to replicate this analysis are archived at Zenodo (doi.org/10.5281/zenodo.1286876).
We thank the editor and two anonymous reviewers for their thorough comments and Emilio Berti, Arne Mooers, Daniel Rabosky, Anthony Barnosky, and John Alroy for helpful and enlightening discussions. This work was funded as part of the Carlsberg Foundation Semper Ardens project MegaPast2Future (Grant CF16-0005) and a VILLUM Investigator project funded by VILLUM FONDEN (Grant 16549). S.F. was supported by the Swedish Research Council (Grant 2017-03862) and a Wallenberg Academy Fellowship from the Knut and Alice Wallenberg Foundation (awarded to Alexandre Antonelli, principal investigator).
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[vc_row][vc_column][vc_column_text]Congratulations to Dr. Daniel Medina in the Department of Biological Sciences, for passing his Ph.D. defense on Friday, July 27, 2018 in Derring Hall. His dissertation seminar was titled “Assessing diversity, cultivability and context-dependent function of the amphibian skin microbiome”.
Daniel joined the IGC program in it’s inaugural year in the Fall of 2013. He completed his Ph.D. while working with the Belden Lab to study community and disease ecology. Daniel’s doctoral research focused on understanding the effects of environmental factors on the diversity and function of the amphibian skin microbiota, and how those microbes may impact the persistence of Batrachochytrium dendrobatidis (Bd) on host organisms. A seasoned tropical biologist – Daniel is headed to the Amphibian Natural History Laboratory of the University of Campinas in Brazil where he will be working as a postdoctoral fellow under the supervision of Dr. Luis Felipe Toledo.
Congratulations Daniel – it’s been an honor working with you through the IGC and we know you’re off to do great things in the biological conservation realm!
Photos from Daniel’s defense seminar on Flickr.
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