The effects of defaunation on plants’ capacity to track climate change

Science ◽  
2022 ◽  
Vol 375 (6577) ◽  
pp. 210-214
Author(s):  
Evan C. Fricke ◽  
Alejandro Ordonez ◽  
Haldre S. Rogers ◽  
Jens-Christian Svenning

Seed dispersal in decline Most plant species depend on animals to disperse their seeds, but this vital function is threatened by the declines in animal populations, limiting the potential for plants to adapt to climate change by shifting their ranges. Using data from more than 400 networks of seed dispersal interactions, Fricke et al . quantified the changes in seed disposal function brought about globally by defaunation. Their analyses indicate that past defaunation has severely reduced long-distance seed dispersal, cutting by more than half the number of seeds dispersed far enough to track climate change. In addition, their approach enables the prediction of seed dispersal interactions using species traits and an estimation of how these interactions translate into ecosystem functioning, thus informing ecological forecasting and the consequences of animal declines. —AMS

2021 ◽  
Author(s):  
◽  
Larissa Nowak

Global biodiversity is changing rapidly and contemporary climate change is an important driver of this change. As climate change continues, the challenge is to understand how it may affect the future of biodiversity. This is relevant to informing policy and conservation, but it requires reliable future projections of biodiversity. Biodiversity is the variety of life on Earth which includes the diversity of species. The species on Earth are linked in diverse networks of biotic interactions. Interacting species can respond differently to climate change. This can cause spatial or temporal mismatches between interacting species and result in secondary extinctions of species that lose obligate interaction partners. Yet, accounting for biotic interactions in biodiversity projections remains challenging. One way to address this challenge is the use of trait-based approaches because the impact of climate change on interacting species is influenced by species’ functional traits, i.e., measurable characteristics of the species that influence their abiotic and biotic interactions. First, species’ functional traits influence how species respond to climate change. Second, they influence whether the species find compatible interaction partners in reshuffled species assemblages under climate change. Thus, the overarching aim of this dissertation was to explore how trait-based approaches can increase our understanding of how climate change might affect interacting species. For this, I focussed on interactions between fleshy-fruited plants and avian frugivores along a tropical elevational gradient. I investigated three principal research questions. First, I investigated how traits related to the sensitivity of avian frugivores to climate change and their adaptive capacity vary along elevation and covary across species. I combined estimates of species’ climatic niche breadth (approximating species’ sensitivity) with traits influencing species’ dispersal ability, dietary niche breadth and habitat niche breadth (aspects of species’ adaptive capacity). Species’ climatic niche breadth increased with increasing elevation, while their dispersal ability and dietary niche breadth decreased with increasing elevation. Across species, there was no significant relationship of the sensitivity of the avian frugivores to climate change and their adaptive capacity. The opposing patterns of species’ sensitivity to climate change and their adaptive capacity along elevation imply that species from assemblages at different elevations may respond differently to climate change. The independence between species’ sensitivity and adaptive capacity suggests that it is important to account for both sensitivity and adaptive capacity to fully understand how climate change might affect biodiversity. Second, I assessed how climate change might influence the co-occurrence of interaction partners with compatible traits, i.e., the functional correspondence of interacting species. I integrated future projections of species’ elevational ranges considering different vertical dispersal scenarios with analyses of the functional diversity of interacting species assemblages. The functional correspondence of fleshy-fruited plants and avian frugivores was lowest if plant and bird species were projected to contract their ranges towards higher elevations in response to increasing temperatures. Contrastingly, if species were projected to expand their ranges upslope, the functional correspondence remained close. The low functional correspondence under a scenario of range contraction indicates that plant species with specific traits might miss compatible interaction partners in future assemblages. This could negatively affect their seed dispersal ability. These results suggest that ensuring the integrity of biotic interactions under climate change requires that species can shift their ranges upslope unlimitedly. Third, I examined whether avian seed dispersal is sufficient for plants to track future temperature change along the elevational gradient. With a trait-based modelling approach, I simulated seed-dispersal distances avian frugivores can provide to fleshy-fruited woody plant species and quantified the number of long-distance dispersal events the plant species would require to fully track projected temperature shifts along elevation. Most plant species were projected to require several long-distance dispersal events to fully track the projected temperature shifts in time. However, the number of required long-distance dispersal events varied with the degree of trait matching and plant species’ traits. These findings suggest that avian seed dispersal is insufficient for plants to track future temperature change along the elevational gradient as woody plant species might not be able to undergo several consecutive long-distance dispersal events within a short time window, due to their long maturation times. These results also imply that the ability of bird-dispersed plant species to track climate change is associated with the specialization of the seed dispersal system and with plant species’ traits. Trait-based approaches are promising tools to study impacts of climate change on interacting species. The trait-based approaches that I have developed in this thesis are applicable more widely, e.g., to other types of biotic interactions, or to assess the effects of other drivers of global change. Moreover, these approaches may be further developed to model changes in biotic interactions under global change more dynamically. Taken together, I have shown how a trait-based perspective could help to account for biotic interactions in biodiversity projections. The development of such approaches and the gained knowledge are urgently needed to facilitate the conservation of biodiversity in a rapidly changing world.


Ecology ◽  
2010 ◽  
Vol 91 (3) ◽  
pp. 767-781 ◽  
Author(s):  
Paul Kardol ◽  
Melissa A. Cregger ◽  
Courtney E. Campany ◽  
Aimee T. Classen

2016 ◽  
Vol 283 (1837) ◽  
pp. 20161267 ◽  
Author(s):  
Sandra Bibiana Correa ◽  
Joisiane K. Arujo ◽  
Jerry Penha ◽  
Catia Nunes da Cunha ◽  
Karen E. Bobier ◽  
...  

When species within guilds perform similar ecological roles, functional redundancy can buffer ecosystems against species loss. Using data on the frequency of interactions between fish and fruit, we assessed whether co-occurring frugivores provide redundant seed dispersal services in three species-rich Neotropical wetlands. Our study revealed that frugivorous fishes have generalized diets; however, large-bodied fishes had greater seed dispersal breadth than small species, in some cases, providing seed dispersal services not achieved by smaller fish species. As overfishing disproportionately affects big fishes, the extirpation of these species could cause larger secondary extinctions of plant species than the loss of small specialist frugivores. To evaluate the consequences of frugivore specialization for network stability, we extracted data from 39 published seed dispersal networks of frugivorous birds, mammals and fish (our networks) across ecosystems. Our analysis of interaction frequencies revealed low frugivore specialization and lower nestedness than analyses based on binary data (presence–absence of interactions). In that case, ecosystems may be resilient to loss of any given frugivore. However, robustness to frugivore extinction declines with specialization, such that networks composed primarily of specialist frugivores are highly susceptible to the loss of generalists. In contrast with analyses of binary data, recently developed algorithms capable of modelling interaction strengths provide opportunities to enhance our understanding of complex ecological networks by accounting for heterogeneity of frugivore–fruit interactions.


2017 ◽  
Vol 65 (5) ◽  
pp. 401 ◽  
Author(s):  
Trevor H. Booth

Eucalypt species have several features that make them particularly well suited for climate change studies. A key assumption is that they have very limited powers of dispersal. If this is correct, it means that climate change analyses to the end of this century can concentrate mainly on assessing whether or not eucalypt species are likely to be able to survive at their existing sites. A recent major climate change study of more than 600 eucalypt species for the period 2014–2085 has used 5 km as a usual dispersal limit for the period to 2085, with the possibility of rare long-distance events. The review presented here considers how far natural stands of eucalypt species are likely to be able to migrate in the period to 2085. It is the first review to consider eucalypt seed dispersal as its major focus. It draws on evidence from millions of years ago to the present, and from eucalypt stands in Australia and around the world. Although rare long-distance events cannot be entirely ruled out, it is concluded that the great bulk of the evidence available indicates that the most likely potential dispersal rate is equivalent to about 1–2 m per year, i.e. ~70–140 m in the period to 2085. Over decades, this is likely to occur as a series of stepwise events, associated with disturbances such as bushfires. However, limitations such as inadequate remnant eucalypt stands and extensive agricultural developments may reduce actual migration rates below even this modest potential.


2014 ◽  
Vol 29 (4) ◽  
pp. 641-651 ◽  
Author(s):  
Felix Heydel ◽  
Sarah Cunze ◽  
Markus Bernhardt-Römermann ◽  
Oliver Tackenberg

2020 ◽  
Author(s):  
Jelle Treep ◽  
Monique de Jager ◽  
Frederic Bartumeus ◽  
Merel B. Soons

Abstract Background – Plant dispersal is a critical factor driving ecological responses to global changes. Knowledge on the mechanisms of dispersal is rapidly advancing, but selective pressures responsible for the evolution of dispersal strategies remain elusive. Recent advances in animal movement ecology identified general strategies that may optimize efficiency in animal searches for food or habitat. We here explore the potential for evolution of similar general movement strategies for plants.Methods – We propose that seed dispersal in plants can be viewed as a strategic search for suitable habitat, where the probability of finding such locations has been optimized through evolution of appropriate dispersal kernels. Using model simulations, we demonstrate how dispersal strategies can optimize key dispersal trade-offs between finding habitat, avoiding kin competition, and colonizing new patches. These trade-offs depend strongly on the landscape, resulting in a tight link between optimal dispersal strategy and spatiotemporal habitat distribution.Results – Our findings reveal that multi-scale seed dispersal strategies that combine short-distance and long-distance dispersal, including Lévy-like dispersal, are optimal across a wide range of dynamic and patchy landscapes. Static patchy landscapes select for short-distance dominated dispersal strategies, while uniform and highly unpredictable landscapes both select for long-distance dominated dispersal strategies.Conclusions – By viewing plant seed dispersal as a strategic search for suitable habitat, we provide a reference framework for the analysis of plant dispersal data. This reference framework helps identify plant species’ dispersal strategies, the evolutionary forces determining these strategies and their ecological consequences, such as a potential mismatch between plant dispersal strategy and altered spatiotemporal habitat dynamics due to land use change. Our perspective opens up directions for future studies, including exploration of composite search behaviour and ‘informed searches’ in plant species with directed dispersal.


Author(s):  
Harald Pauli ◽  
Stephan R.P. Halloy

High mountains (i.e., mountains that reach above the climatic treeline) are regions where many interests converge. Their treeless alpine landscapes and ecosystems are key areas for biodiversity, they act as water sources and reservoirs, and they are cultural and religious icons. Yet, mountain environments are threatened by global stressors such as land use impacts and anthropogenic climate change, including associated species redistributions and invasions. High mountains are warming faster than lower elevations. The number of frost days is declining, glaciers are retreating, and snow is remaining for shorter periods, while CO2 partial pressure is increasing. All of these factors affect the way in which ecosystems prosper or degrade. Thanks to the compression of thermal belts and to topographic ruggedness that favors habitat heterogeneity, mountains have a high diversity of biotic communities and species richness at the landscape level. In tropical to temperature regions, high mountains are biogeographically much like islands. With small habitat areas, species tend to be distributed patchily, with populations evolving independently from those on other isolated summits. Although high mountain areas strongly differ in size, geological age, bedrock, glacial history, solar radiation, precipitation patterns, wind exposure, length of growing season, and biotic features, they are all governed by low-temperature conditions. Combined with their distribution over all climate zones on Earth, mountain habitats and their biota, therefore, represent an excellent natural indicator system for tracing the ecological impacts of global climate change. As temperatures rise, plants and animals migrate upward (and poleward). Plant and animal populations on small, isolated mountains have nowhere to go if climates warm and push them upslope. On the other hand, habitat heterogeneity may buffer against biodiversity losses by providing a multitude of potential refugia for species which become increasingly maladapted to their present habitats. Global-scale approaches to monitor climate and biotic change in high mountains as well as modeling and experimental studies are helping explain the nature of these changes. Such studies have found that species from lower elevations are colonizing habitats on mountain summits at an accelerating pace, with five times faster rates than half a century ago. Further, repeated in situ surveys in permanent plots showed a widespread transformation of alpine plant community assemblages toward more warmth-demanding and/or less cold-adapted species. Concurrently to widespread increases in overall species richness, high-elevation plant species have declined in abundance and frequency. Strongly cold-adapted plant species may directly suffer from warmer and longer growing seasons through weak abilities to adjust respiration rates to warmer conditions. Combined effects of warming and decreasing water availability will amplify detrimental effects of climatic stresses on alpine biota. Many of the dwarf and slow-growing species, however, will be affected when taller and faster-growing species from lower elevations invade and prosper with warming in alpine environments and, thus, threaten to outcompete locally established species. Warming conditions will also encourage land use changes and upward movement of agriculture, while loss of snow is a loss to ski fields and scenic tourism.


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