The legacy of the extinct Neotropical megafauna on plants and biomes

Andermann T., Faurby S., Turvey S.T., Antonelli A., Silvestro D.

Human driven extinctions of recent past pale in comparison to future predictions, as a major global extinction wave is unfolding.

Dantas V.L., Pausas J.G.

Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior. Grant Number: 88887.311538/2018‐00

Lundgren E.J., Ramp D., Rowan J., Middleton O., Schowanek S.D., Sanisidro O., Carroll S.P., Davis M., Sandom C.J., Svenning J., Wallach A.D.

Significance Humans have caused extinctions of large-bodied mammalian herbivores over the past ∼100,000 y, leading to cascading changes in ecosystems. Conversely, introductions of herbivores have, in part, numerically compensated for extinction losses. However, the net outcome of the twin anthropogenic forces of extinction and introduction on herbivore assemblages has remained unknown. We found that a primary outcome of introductions has been the reintroduction of key ecological functions, making herbivore assemblages with nonnative species more similar to preextinction ones than native-only assemblages are. Our findings support calls for renewed research on introduced herbivore ecologies in light of paleoecological change and suggest that shifting focus from eradication to landscape and predator protection may have broader biodiversity benefits.

Armani M., Goodale U.M., Charles‐Dominique T., Barton K.E., Yao X., Tomlinson K.W.

Given that the rate of resource capture constrains plant growth and defence, understanding the linkage between the leaf economic spectrum (LES) and defence and how it contributes to growth is central to predicting species performance. In spite of the prevalence of spiny plants in many plant communities, little is known about how the LES relates to defence and growth rate across these species. We grew 42 spiny species, from diverse environments, under common garden conditions for 15 weeks and measured LES (leaf N, SLA and assimilation rate), defence and growth traits. We assessed general relationships between LES and growth rate and tested whether structural defences (spines, leaf fibre and lignin content) and quantitative chemical defences (condensed tannins) are linked to the LES and growth and if different spine types (i.e. leaf spines, stipular spines, prickles and thorns), with distinct anatomical origins, partition out across the LES. We observed two independent trait axes that together explained ~68% of trait variation across species. The first axis showed that structural defences (spines, leaf fibre and lignin content) trade off with leaf productivity along the LES. Axis 2 revealed that condensed tannins is orthogonal and less integrated with the LES‐structural defence axis. Bivariate trait analyses disclosed positive covariations between LES traits and sapling growth rate. All structural defence traits were negatively related to sapling growth. Across spine types, species with leaf spines were associated with the conservative end of the LES, characterized by high structural defences and lower leaf productivity relative to other spine types. Synthesis: Our study shows that the LES and structural defences are coupled in spiny species such that constitutive growth – defence strategies range from fast‐growing species with low allocation to defences to slow‐growing species that invest heavily in structural defences (dominated by leaf spiny species).

de Oliveira K., Araújo T., Rotti A., Mothé D., Rivals F., Avilla L.S.

The extinction of the Quaternary megafauna stands out among the evolutionary history of Cenozoic mammals. In South America, nearly 80% of the megamammals went extinct, including the native ungulates Macrauchenia patachonica and Xenorhinotherium bahiense. Little is known about the causes of the macraucheniids’ extinction and their paleobiology. Here, we have reconstructed the dietary habits of M. patachonica and X. bahiense using enamel microwear and occlusal enamel index analyses, and also inferred their niches using species distribution modeling and stable isotope paleoecology, in addition to enamel microwear and occlusal enamel index data. We found that both macraucheniids had grazer-feeding habits, although their environmental requirements were different. M. patachonica could live in colder temperatures and arid, subtropical/temperate ecosystems, while X. bahiense was adapted to warmer temperatures and more humid, semi-arid tropical environments. Thus, despite similar feeding habits, these macraucheniids had distinct environmental requirements and ecological niches, which might explain the disjunction in the South American records.

Armani M., Charles-Dominique T., Barton K.E., Tomlinson K.W.

Abstract Background and Aims Herbivory by large mammals imposes a critical recruitment bottleneck on plants in many systems. Spines defend plants against large herbivores, and how early they emerge in saplings may be one of the strongest predictors of sapling survival in herbivore-rich environments. Yet little effort has been directed at understanding the variability in spine emergence across saplings. Methods We present a multispecies study examining whether and how sapling size, spine type and species' environmental niche (light and precipitation environment) influence early emergence and biomass investment in spines. A phylogenetically diverse pool of 45 species possessing different spine types (spines, prickles and thorns; that are derived from distinct plant organs: leaf, epidermis or cortex, and branch, respectively), were grown under common-garden conditions, and patterns of spine emergence and biomass allocation to spines at 5 and 15 weeks after transplanting were characterized. Key Results Spine type and species' resource niche were the main factors driving early emergence and investment patterns. Spines emerged earliest in leaf spine-bearing species, and latest in thorn-bearing species. The probability of early spine emergence increased with decreasing precipitation, and was greater in species from open than from closed habitats. Sapling investment in spines changed with plant mass but was contingent on spine type and habitat type. Conclusions Different spine types have strikingly different timing of expression, suggesting that developmental origins of spines play a critical role in sapling defences. Furthermore, species from different precipitation and light environments (open vs. closed habitats) showed contrasting patterns of early spine expression, suggesting that resource limitation in their native range may have driven divergent evolution of early defence expression.

Steidinger B.S., Crowther T.W., Liang J., Van Nuland M.E., Werner G.D., Reich P.B., Nabuurs G.J., de-Miguel S., Zhou M., Picard N., Herault B., Zhao X., Zhang C., Routh D., Peay K.G.

The identity of the dominant root-associated microbial symbionts in a forest determines the ability of trees to access limiting nutrients from atmospheric or soil pools1,2, sequester carbon3,4 and withstand the effects of climate change5,6. Characterizing the global distribution of these symbioses and identifying the factors that control this distribution are thus integral to understanding the present and future functioning of forest ecosystems. Here we generate a spatially explicit global map of the symbiotic status of forests, using a database of over 1.1 million forest inventory plots that collectively contain over 28,000 tree species. Our analyses indicate that climate variables—in particular, climatically controlled variation in the rate of decomposition—are the primary drivers of the global distribution of major symbioses. We estimate that ectomycorrhizal trees, which represent only 2% of all plant species7, constitute approximately 60% of tree stems on Earth. Ectomycorrhizal symbiosis dominates forests in which seasonally cold and dry climates inhibit decomposition, and is the predominant form of symbiosis at high latitudes and elevation. By contrast, arbuscular mycorrhizal trees dominate in aseasonal, warm tropical forests, and occur with ectomycorrhizal trees in temperate biomes in which seasonally warm-and-wet climates enhance decomposition. Continental transitions between forests dominated by ectomycorrhizal or arbuscular mycorrhizal trees occur relatively abruptly along climate-driven decomposition gradients; these transitions are probably caused by positive feedback effects between plants and microorganisms. Symbiotic nitrogen fixers—which are insensitive to climatic controls on decomposition (compared with mycorrhizal fungi)—are most abundant in arid biomes with alkaline soils and high maximum temperatures. The climatically driven global symbiosis gradient that we document provides a spatially explicit quantitative understanding of microbial symbioses at the global scale, and demonstrates the critical role of microbial mutualisms in shaping the distribution of plant species. A spatially explicit global map of tree symbioses with nitrogen-fixing bacteria and mycorrhizal fungi reveals that climate variables are the primary drivers of the distribution of different types of symbiosis.

Pausas J.G., Bond W.J.

Alexander von Humboldt is a key figure in the history of ecology and biogeography who contributed to shape what is today ecology, as well as the environmentalist movement. His observation that the world’s vegetation varies systematically with climate was one of his many contributions to science. Here, we question to what extent Humboldt’s view biased our vision of nature. The current emphasis on the role of climate and soils in ecological and evolutionary studies, and the emphasis on forests as the potential and most important vegetation, suggests that we still view nature through the eyes of Humboldt. Over the last 20 years, diverse studies have shown that many open non‐forested ecosystems (savannas, grasslands, and shrublands) cannot be predicted by climate and are ancient and diverse systems maintained by fire and/or vertebrate herbivory. Paleoecological and phylogenetic studies have shown the key role of these plant consumers at geological time scales. This has major implications for how we understand and manage our ecosystems. Synthesis. We need to consciously probe the long‐standing idea that climate and soils are the only major factors shaping broad‐scale patterns in nature. We propose to move beyond the legacy of Humboldt by embracing fire and large mammal herbivory as additional key factors in explaining the ecology and evolution of world vegetation.

Bruelheide H., Dengler J., Purschke O., Lenoir J., Jiménez-Alfaro B., Hennekens S.M., Botta-Dukát Z., Chytrý M., Field R., Jansen F., Kattge J., Pillar V.D., Schrodt F., Mahecha M.D., Peet R.K., et. al.

Plant functional traits directly affect ecosystem functions. At the species level, trait combinations depend on trade-offs representing different ecological strategies, but at the community level trait combinations are expected to be decoupled from these trade-offs because different strategies can facilitate co-existence within communities. A key question is to what extent community-level trait composition is globally filtered and how well it is related to global versus local environmental drivers. Here, we perform a global, plot-level analysis of trait–environment relationships, using a database with more than 1.1 million vegetation plots and 26,632 plant species with trait information. Although we found a strong filtering of 17 functional traits, similar climate and soil conditions support communities differing greatly in mean trait values. The two main community trait axes that capture half of the global trait variation (plant stature and resource acquisitiveness) reflect the trade-offs at the species level but are weakly associated with climate and soil conditions at the global scale. Similarly, within-plot trait variation does not vary systematically with macro-environment. Our results indicate that, at fine spatial grain, macro-environmental drivers are much less important for functional trait composition than has been assumed from floristic analyses restricted to co-occurrence in large grid cells. Instead, trait combinations seem to be predominantly filtered by local-scale factors such as disturbance, fine-scale soil conditions, niche partitioning and biotic interactions. Although plant functional trait combinations reflect ecological trade-offs at the species level, little is known about how this translates to whole communities. Here, the authors show that global trait composition is captured by two main dimensions that are only weakly related to macro-environmental drivers.

Dexter K.G., Pennington R.T., Oliveira-Filho A.T., Bueno M.L., Silva de Miranda P.L., Neves D.M.

Tropical moist forests and savannas are iconic biomes. There is, however, a third principal biome in the lowland tropics that is less well known: tropical dry forest. Discussions on responses of vegetation in the tropics to climate and land-use change often focus on shifts between forests and savannas, but ignore dry forests. Tropical dry forests are distinct from moist forests in their seasonal drought stress and consequent deciduousness and differ from savannas in rarely experiencing fire. These factors lead tropical dry forests to have unique ecosystem function. Here, we discuss the underlying environmental drivers of transitions among tropical dry forests, moist forests and savannas, and demonstrate how incorporating tropical dry forests into our understanding of tropical biome transitions is critical to understanding the future of tropical vegetation under global environmental change.

Staal A., Tuinenburg O.A., Bosmans J.H., Holmgren M., van Nes E.H., Scheffer M., Zemp D.C., Dekker S.C.

Tree transpiration in the Amazon may enhance rainfall for downwind forests. Until now it has been unclear how this cascading effect plays out across the basin. Here, we calculate local forest transpiration and the subsequent trajectories of transpired water through the atmosphere in high spatial and temporal detail. We estimate that one-third of Amazon rainfall originates within its own basin, of which two-thirds has been transpired. Forests in the southern half of the basin contribute most to the stability of other forests in this way, whereas forests in the south-western Amazon are particularly dependent on transpired-water subsidies. These forest-rainfall cascades buffer the effects of drought and reveal a mechanism by which deforestation can compromise the resilience of the Amazon forest system in the face of future climatic extremes. Tree transpiration in the Amazon enhances downwind rainfall. Research now shows that approximately one-third of Amazon rainfall originates within its own basin, with the southern half of the basin contributing most to this effect.

Wigley B.J., Fritz H., Coetsee C.

Southern African savannas are commonly polarised into two broad types based on plant functional types and defences; infertile savannas dominated by broad-leaved trees typically defended by nitrogen-free secondary compounds and fertile savannas dominated by fine-leaved trees defended by structural defences. In this study, we use trait and other data from 15 wooded savanna sites in Southern Africa and ask if broad-leaved and fine-leaved species dominate on nutrient-poor and nutrient-rich soils, respectively. We then test if there is there any evidence for trade-offs in chemical (i.e., condensed tannins and total polyphenols) vs. structural defences on different soil types. We did not find strong evidence for a general divide in fine- vs. broad-leaved savannas according to soil fertility, nor for a simple trade-off between chemical and structural defences. Instead, we found savanna species to cluster into three broad defence strategies: species were high in leaf N and either (A) highly defended by spines and chemicals or (B) only structurally defended, or (C) low in leaf N and chemically defended. Finally, we tested for differences in browser utilisation between soil types and among plant defence strategies and found that browsing by meso-herbivores was higher on nutrient-rich soils and targeted species from groups A and B and avoided C, while browsing by elephants was mostly not affected by soil type or defence strategy. We propose a framework that can be used as a basis for asking strategic questions that will help improve our understanding of plant defences in savannas.

Doughty C.E.

Can the presence of herbivores increase global nutrient availability? Animals disperse vital nutrients through ecosystems, increasing the spatial availability of these nutrients. Large herbivores are especially important for the dispersal of vital nutrients due to their long food passage times and day ranges, and large herbivores from past periods (the Pleistocene) may have increased nutrient concentrations on the continental scale. However, such results have been demonstrated theoretically but not yet empirically. Models suggest that the Pennsylvanian subperiod (323−299 million years ago), with no tetrapod terrestrial herbivores, would have had fewer, less-well-distributed nutrients than the Cretaceous period (145−66 million years ago), with the largest terrestrial herbivores ever—the sauropods. Here, I show that these models are supported empirically by remnant plant material (coal deposits) from the Cretaceous (N = 680), which had significantly (P < 0.00001) increased concentrations (136%) and decreased spatial heterogeneity (22%) of plant-important rock-derived nutrients compared with the Pennsylvanian subperiod (N = 4,996). Non-biotic physical processes, such as weathering rates, cannot account for such differences, because aluminium—a nutrient not important for plants and animals, but weathered in a similar manner to the above elements—showed no significant difference between the two periods, suggesting that these large changes were driven by plant–herbivore interactions. Populations of large wild herbivores are currently at historical lows; therefore, we are potentially losing a key ecosystem service. Nutrients important for plants were more abundant and evenly distributed in the Cretaceous period, probably due to the presence of large herbivorous dinosaurs, than in the Pennsylvanian subperiod, which had no tetrapod herbivores.

Arruda D.M., Schaefer C.E., Fonseca R.S., Solar R.R., Fernandes-Filho E.I.

Aim The two main hypotheses about the Neotropical palaeovegetation, namely that of Amazonian refugia by Haffer and of the Pleistocene arc by Prado and Gibbs, are still constantly debated. We offer new insights on this debate using ecological niche modelling with combined climate–soil predictors to test both hypotheses, reconstruct the palaeovegetation of the Last Glacial Maximum (LGM; 21 ka) and Mid-Holocene (Mid-H; 6 ka) and indicate the configuration of refugia areas. Location Brazil. Time period Last 21 ka. Major taxa studied Biomes. Methods We modelled the environmental space of the 10 most representative biomes with the RandomForest classifier, using climate predictors from three atmospheric general circulation models (CCSM4, MPI-ESM-P and MIROC-ESM) and soil predictors, the same for the different situations. Based on the consensus among the models, we reconstructed the palaeovegetation cover for LGM and Mid-H and used fossil pollen sites to validate the reconstructions in a direct comparison. Results The climate in the past was cooler and wetter throughout most of the territory. The Amazon basin region was the most affected by climate change in the last 21 ka, with equatorial rain forest retracting to refugia areas, while the tropical rain forest (with climatic preferences similar to the Atlantic forest) expanded in the basin. In southern Brazil, the mixed forest (Araucaria forest) shifted to lower latitudes, while the grasslands expanded. In most biomes, the greatest changes occurred in the ecotonal zones, supported by pollen fossils. Main conclusions With regard to Haffer's hypothesis, the forests of the Amazonian lowlands retreated to refugia areas, while the colder and wetter climate of the basin created a favourable niche for another type of forest, instead of savanna. The advance of dry vegetation was restricted to ecotonal conditions, preventing the formation of a continuous Pleistocene arc, predicted by Prado and Gibbs's hypothesis.

Galetti M., Moleón M., Jordano P., Pires M.M., Guimarães P.R., Pape T., Nichols E., Hansen D., Olesen J.M., Munk M., de Mattos J.S., Schweiger A.H., Owen-Smith N., Johnson C.N., Marquis R.J., et. al.

For hundreds of millions of years, large vertebrates (megafauna) have inhabited most of the ecosystems on our planet. During the late Quaternary, notably during the Late Pleistocene and the early Holocene, Earth experienced a rapid extinction of large, terrestrial vertebrates. While much attention has been paid to understanding the causes of this massive megafauna extinction, less attention has been given to understanding the impacts of loss of megafauna on other organisms with whom they interacted. In this review, we discuss how the loss of megafauna disrupted and reshaped ecological interactions, and explore the ecological consequences of the ongoing decline of large vertebrates. Numerous late Quaternary extinct species of predators, parasites, commensals and mutualistic partners were associated with megafauna and were probably lost due to their strict dependence upon them (co-extinctions). Moreover, many extant species have megafauna-adapted traits that provided evolutionary benefits under past megafauna-rich conditions, but are now of no or limited use (anachronisms). Morphological evolution and behavioural changes allowed some of these species partially to overcome the absence of megafauna. Although the extinction of megafauna led to a number of co-extinction events, several species that likely co-evolved with megafauna established new interactions with humans and their domestic animals. Species that were highly specialized in interactions with megafauna, such as large predators, specialized parasites, and large commensalists (e.g. scavengers, dung beetles), and could not adapt to new hosts or prey were more likely to die out. Partners that were less megafauna dependent persisted because of behavioural plasticity or by shifting their dependency to humans via domestication, facilitation or pathogen spill-over, or through interactions with domestic megafauna. We argue that the ongoing extinction of the extant megafauna in the Anthropocene will catalyse another wave of co-extinctions due to the enormous diversity of key ecological interactions and functional roles provided by the megafauna.

Søndergaard S.A., Fløjgaard C., Ejrnæs R., Svenning J.

The extensive, prehistoric loss of megafauna during the last 50 000 years led early naturalists to build the founding theories of ecology based on already‐degraded ecosystems. In this article, we outline how large herbivores affect community ecology, with a special focus on plants, through changes to selection, speciation, drift, and dispersal, thereby directly impacting ecosystem diversity and functionality. However, attempts to quantify effects of large herbivores on ecosystem processes are markedly scarce in past and contemporary studies. We expect this is due to the shifting baseline syndrome, where ecologists omit the now‐missing effects of extinct, large herbivores when designing experiments and theoretical models, despite evidence that large herbivores shaped the physical structure, biogeochemistry, and species richness of the studied systems. Here, we outline how effects of large herbivores can be incorporated into central theoretical models to integrate megaherbivore theory into community ecology. As anthropogenic impacts on climate and nutrient levels continue, further warping ecological processes and disconnecting species distributions from optimal conditions, the importance of quantifying large herbivore functionality, such as facilitation of dispersal and coexistence, increases. Our findings indicate that current scientific attention to large herbivores is disproportionate to their past impacts on habitat structure and evolutionary trajectories, as well as the role large herbivores can play in restoring diverse and resilient ecosystems.

Hyvärinen O.P., te Beest M., le Roux E., Kerley G.I., Buitenwerf R., Druce D.J., Chen J., Rapp L., Fernandes J., Cromsigt J.P.

Abstract Wild animals can modulate ecosystem-climate feedbacks, e.g. through impacts on vegetation and associated carbon dynamics. However, vegetation cover and composition also affect land surface albedo, which is an important component of the global energy budget. We currently know very little about the influence of wild animals on land surface albedo and the resulting climate forcing of these albedo changes. Leveraging a unique, ecosystem-scale, semi-experimental approach, we study how the local removals of the world’s largest, terrestrial grazer, white rhinoceros (Ceratotherium simum), affected the coupling between fire dynamics, woody encroachment and surface albedo in Hluhluwe–iMfolozi Park (HiP), South Africa. Our path analysis revealed that areas in the park where more rhinos had been removed showed a stronger increase in burnt area and woody encroachment compared to areas with fewer rhinos removed, which were both related to a decrease in surface albedo. Increasing burnt area was further associated with higher rates of woody encroachment, indirectly reinforcing the negative effect of rhino loss on albedo. Our study demonstrates that removals of megagrazers in HiP were related to complex ecosystem-wide cascades with measurable impacts on land cover and surface albedo and consequences on climate forcing. This highlights the importance of restoring functional ecosystems by reinstating trophic processes.

Mata J.C., Svenning J., Chequín R.N., Davalos M., Salas R., Vucko A., Buitenwerf R.

ABSTRACTQuestionsHerbivores can exert strong top‐down control on vegetation structure and composition, which in turn can affect overall biodiversity and ecosystem processes. However, South American megafauna was largely driven to extinction in recent prehistory, and remaining species have suffered severe range reductions from human actions. The potential role of South American megafauna in shaping vegetation therefore remains unclear. We examined herbivore‐driven top‐down control of the vegetation, particularly impacts on plant diversity, structure and functional composition.LocationIberá Wetlands, Corrientes, Argentina.MethodsWe set up an herbivore exclosure experiment in a restoration area with 10 wild large‐herbivore species. We compared vegetation dynamics in fenced plots with paired control plots to which herbivores had full access. Replicate plot pairs were established in three grassland types: characterized as short, medium‐tall and tall grasslands. Grass height, plant biomass, functional types and community composition were measured at the start of the experiment and after 6, 13 and 18 months.ResultsWe found that in short and medium‐tall grasslands, herbaceous biomass and grass height increased significantly in no‐grazing plots, while species richness decreased. Similarly, community dissimilarity between paired grazed and ungrazed plots increased over time for short and medium‐tall grasslands. Camera trap images revealed that capybara (Hydrochoerus hydrochaeris) was the dominant grazer on the grazed plots.ConclusionOur results show a strong impact of native herbivores on the structure and composition of South American savannas akin to African grazing lawns, with higher plant species richness and dominance of grazing‐tolerant growth forms. These results imply that South American grassy ecosystems, despite severely reduced herbivore richness and density, have retained plant taxa and functional trait complexes that tolerate intense herbivory. Further, they also show that herbivory can still play an important role in maintaining their plant diversity. The conservation and restoration of South American grassy ecosystems are likely to benefit from restoring functional grazing regimes.

Doughty C.E., Wiebe B.C., Keany J.M., Gaillard C., Abraham A.J., Kristensen J.A.

AbstractIt has been hypothesized that the extinction of the dinosaurs, and later the Pleistocene megafauna, created a darker forest subcanopy benefiting large‐seeded plants. Larger seeds and their fruit, in turn, opened a dietary niche space for animals thus strongly shaping the ecology of the Cenozoic, including our fruit‐eating primate ancestors. In this paper, we develop a mechanistic model where we replicate the conditions of tropical forests of the early Paleocene, with small animal body and small seed size, and the Holocene, with small animal body and large seed size. We first calibrate light levels in our model using stable carbon isotope ratios from fossil leaves and estimate a decrease of understory light of c. 90 μmol m−2 s−1 (a 19% decrease) from the Cretaceous to the Paleocene. Our model predicts a rapid increase in seed size during the Paleocene that eventually plateaued or declined slightly. Specifically, we find a dynamic feedback where increased animal sizes opened the understory causing negative feedback by increasing subcanopy light penetration that limited maximum seed size, matching the actual trend in angiosperm seed sizes in mid/high latitude ecosystems. Adding the ability of larger animals to increase ecosystem fertility to the model, further increased mean animal body size by 17% and mean seed size by 90%. Our model is a drastic simplification and there are many remaining uncertainties, but we show that ecological dynamics can explain seed size trends without adding external factors such as climate change.

Pavanetto N., Niinemets Ü., Rueda M., Puglielli G.

ABSTRACTUnderstanding the main ecological constraints on plants' adaptive strategies to tolerate multiple abiotic stresses is a central topic in plant ecology. We aimed to uncover such constraints by analysing how the interactions between climate, soil features and species functional traits co‐determine the distribution and diversity of stress tolerance strategies to drought, shade, cold and waterlogging in woody plants of the Northern Hemisphere. Functional traits and soil fertility predominantly determined drought and waterlogging/cold tolerance strategies, while climatic factors strongly influenced shade tolerance. We describe the observed patterns by defining ‘stress tolerance biomes’ and ‘polytolerance hotspots’, that is, geographic regions where woody plant assemblages have converged to specific tolerance strategies and where the coexistence of multiple tolerance strategies is frequent. The depiction of these regions provides the first macroecological overview of the main environmental and functional requirements underlying the ecological limits to the diversity of abiotic stress tolerance strategies in woody plants.

Root-Bernstein M., Guerrero-Gatica M., Elorrieta Rossle A., Fleming J., Ramos Aguillar J., Silva Rochefort B., Charles-Dominique T., Armesto J., Jaksic F.M.

Many South American dry woodlands lack good historical or paleoecological baseline data to inform restoration and conservation. However, functionalist approaches such as those popularized by rewilding suggest that functional interactions producing target ecosystem processes are valid even without data confirming compositionalist values such as a long coevolutionary histories or known historical range overlaps of target species. In central Chile, the guanaco (Lama guanicoe) has been extirpated but is known to browse trees in other regions of South America, and the tree Vachellia [Acacia] caven shows adaptations to browsing but has no extant browsers within its Chilean range. Both species are native to Chile but there are no data to assess their historical levels of interaction. Here we test the hypothesis that they can act as mutual "Eltonian proxy" species: interacting species for which we lack sufficient data (the Eltonian shortfall) to prove they are not proxies. Specifically we predict that they have complementary adaptations such that guanacos will browse Vachellia [Acacia] caven and the latter will show adaptive responses to their browsing. We introduced five guanacos into an enclosure of Vachellia [Acacia] caven "espinal" woodland, and over two years measured the growth responses of individual branches, compared to branches of trees in an area without browsing. We predicted that Vachellia [Acacia] caven would show compensatory growth in response to guanaco browsing resulting in an increase in branching. Guanacos browsed throughout the two years. In the presence of guanaco browsing, Vachellia [Acacia] caven branches grew longer, grew more sub-branches, and showed more densely streamlined branch architectures. These results indicate that guanacos could be used to substitute anthropogenic pruning as a restoration and management technique in Vachellia [Acacia] caven "espinal" woodlands. However, other extinct megaherbivores or extirpated deer may also be key components of a past herbivore community to which Vachellia [Acacia] caven was adapted. Further attention to a network of multiple interacting browsers, and their indirect and nontrophic effects, is an area for further research.

Pires M.M.

Most terrestrial large mammals went extinct on different continents at the end of the Pleistocene, between 50,000 and 10,000 years ago. Besides the loss in species diversity and the truncation of body mass distributions, those extinctions were even more impactful to interaction diversity. Along with each extinction, dozens of ecological interactions were lost, reorganizing species interaction networks, which attained species-poor configurations with low functional redundancy. Extinctions of most large herbivores impacted energy flow and the rates of nutrient cycling, reconfiguring ecosystem-level networks. Because large mammals have high mobility, their loss also shortened seed-dispersal distance and reduced nutrient diffusivity, disrupting spatial networks. This review examines the recent advances in understanding how different types of ecological networks have been restructured by megafaunal extinctions and how this reorganization affected ecosystem functions. ▪ Megafaunal extinctions resulted in the loss of multiple ecological interactions in terrestrial systems. ▪ Interaction loss reshaped different types of ecological networks including food webs and spatial networks. ▪ The reorganization of ecological networks changed how terrestrial ecosystems are structured and function. Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 52 is May 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Messeder J.V., Carlo T.A., Zhang G., Tovar J.D., Arana C., Huang J., Huang C., Ma H.

Summary Mutualisms between plants and fruit‐eating animals were key to the radiation of angiosperms. Still, phylogenetic uncertainties limit our understanding of fleshy‐fruit evolution, as in the case of Solanum, a genus with remarkable fleshy‐fruit diversity, but with unresolved phylogenetic relationships. We used 1786 nuclear genes from 247 species, including 122 newly generated transcriptomes/genomes, to reconstruct the Solanum phylogeny and examine the tempo and mode of the evolution of fruit color and size. Our analysis resolved the backbone phylogeny of Solanum, providing high support for its clades. Our results pushed back the origin of Solanum to 53.1 million years ago (Ma), with most major clades diverging between 35 and 27 Ma. Evolution of Solanum fruit color and size revealed high levels of trait conservatism, where medium‐sized berries that remain green when ripe are the likely ancestral form. Our analyses revealed that fruit size and color are evolutionary correlated, where dull‐colored fruits are two times larger than black/purple and red fruits. We conclude that the strong phylogenetic conservatism shown in the color and size of Solanum fruits could limit the influences of fruit‐eating animals on fleshy‐fruit evolution. Our findings highlight the importance of phylogenetic constraints on the diversification of fleshy‐fruit functional traits.

Herold D.M., Breitbarth T., Hergesell A., Schulenkorf N.

As a response to the increasing threat to sport events from climate change and expectations around climate change mitigation, sport event managers increasingly engage in environmentally-related initiatives that aim to reduce GHG emissions. One of the major contributors to GHG emissions at large sport events is spectators' travel and, thus, their associated modal choices. Building on the Sport Logistics Framework (SLF) and using the case study of Rapid Vienna, the largest football club in Austria, this study investigates spectators' modal choice to systematically assess the total GHGs emitted by spectators at a professional football home game. Data was obtained from two sources: a) an extensive data set collected on Rapid Vienna season ticket holders, and b) three surveys at home games which, together, constituted 3,317 valid responses. The calculation of the GHG emissions resulted in 99,548 kg GHG emissions per home game or 6.0 kg GHG emissions per spectator. It was also found that 42.4 per cent spectators arriving by car emit 71.6 per cent of GHG emissions, while in contrast, 52.8 per cent of spectators using public transport emit 27.1 per cent of GHG emissions. The results also indicate that the possession of an annual public transport ticket seems to determine travel behavior, i.e. the majority of spectators with an annual ticket are using it, while spectators without a ticket are using a car. As such, this paper not only provides an opportunity for academics and managers to benchmark the data in order to identify initiatives to reduce the impact of GHG emissions, but also allows for the systematic measuring of the environmental impact of fan and spectator travel.

Pausas J.G., Lamont B.B., Keeley J.E., Bond W.J.

Atkinson J., Gallagher R., Czyżewski S., Kerr M., Trepel J., Buitenwerf R., Svenning J.

Abstract Trophic rewilding is gaining rapid momentum as a means of restoration across the world. Advances in research are elucidating the wide‐ranging effects of trophic rewilding and megafauna re‐establishment on ecosystem properties and processes including resilience, nutrient cycling, carbon sequestration, productivity and plant richness. A substantial gap remains in trophic rewilding research on how rewilding affects the frequency and expression of plant functional traits, a key hypothesised avenue by which megafauna can affect biodiversity and ecosystem processes. Yet, there is extensive literature examining the effects of mammal herbivory and exclusion on plant traits from which we may infer potential effects of megafauna reintroductions. Here, we synthesise the literature to show the multifaceted ways that plant functional composition responds to mammalian herbivory and explore how these responses are modulated by the density and identity of herbivores as well as resource availability, ecosystem productivity and historical contingency. We further explore these interactions in a quantitative analysis on European plant species. In addition, we link these broad patterns between mammal herbivory and traits to literature on plant invasions to predict how trophic rewilding may be able to reduce invasive plant dominance, as ecosystems around the world are transitioning towards novel states, occupied by a mix of native and introduced species. Expanding current research on herbivore effects (and their implications for trophic rewilding) beyond plant species richness and towards measurable functional traits can help assess and quantify processes that were not previously possible. Trait approaches can help to test mechanistic hypotheses on the top‐down impacts of large herbivores on plant communities to reveal links between trophic rewilding and ecosystem processes and properties. Synthesis. Given the rapid, much‐needed expansion of restoration and rewilding activities across the world, trait‐based ecology offers a pathway to generalisable predictions of the ecosystem impacts of rewilding, particularly in the context of both the unique landscape processes associated with rewilding (e.g. landscape scale spatiotemporal variability, dispersal) and of widely emerging novel ecosystems.

Bobadilla Y.T., Ibarra Polesel M.G., Gómez-Cifuentes A., Zurita G.

In the context of the biodiversity crisis, trophic rewilding became an important (but controversial) management practice to restore biological interactions and ecological processes. The success of this practice relies on the richness and abundance of other organisms, mainly invertebrates. In the Ibera wetlands of Argentina, a rewilding project reintroduced large herbivores locally extinct (the Tapir and Pampas deer, among others). Taking advantage of this project, we explored taxonomic and functional changes in dung beetle assemblages associated with replacing domestic livestock with native mammals. In five replicates, we sampled dung beetles with seven different baits, estimated temperature and grass eight and described landscape composition (forest and grassland cover). Through lineal and mixed models, NMDS and ANOSIM, we compared the taxonomic and functional dung beetle structure in both areas and explored the role of environmental variables. Trophic rewilding did not change dung beetle richness and the trophic structure of assemblages; however, it strongly modified the composition of species and their functional structure. Both areas shared 40 % of species. Species associated with cow dung (such as the exotic. D. gazella) became rare or disappeared in rewilded areas. Roller species dominated rewilded areas, whereas livestock areas exhibited a large abundance of burying species. The trophic rewilding changed dung beetle assemblages in the Iberá partially due to changes in the diversity of available dung but also on environmental conditions. Rewilding should include the medium and long-term evaluation of other taxa and ecological processes to quantify the conservation and functional value of species reintroduction.

Rindel D.D., Moscardi B.F., Cobos V.A., Gordón F.

In this paper we study the relationships between plants and extinct megafauna by examining the characteristics of the vegetation in the central region of Argentina (i.e. Espinal, Monte, and Chaco phytogeographic regions). First, we study the size, shape, quantity, and characteristics of fruits and seeds. We also evaluate the presence of mechanical (spinescence and wood density) and chemical (secondary metabolic compounds) defenses against high rates of herbivory. Complementarily, we assess the importance these plants had for human populations, using archeological, ethnographic, and current data. A high percentage of the analyzed plants met the criteria proposed for fruits and seeds dispersed by megafauna, together with a high frequency of spinescence, high density woods, and secondary metabolites. We propose that these traits cannot be explained by the herbivory pressure of extant fauna in the area, but rather developed in interaction with currently extinct fauna. We suggest that Pleistocene megafaunal extinction had important consequences in the region due to their role as ecosystem engineers and to vegetation’s characteristics, which were probably strongly shaped by megafauna activities. Among these consequences, we discuss the loss of certain interactions between these animals and vegetation, such as loss of seed dispersal mechanisms, shrub invasion, and increased susceptibility of vegetation to fire. Other effects for hunter-gatherer groups were the generation of highly regulated mobility patterns and the formation of barriers for the dispersal of prey. Finally, we also discuss the importance of these plants for human populations as food, construction material, medicines and firewood. Likewise, the role of humans as “heirs” of the megafauna in the propagation of tree and shrub species is highlighted.

Barton K.E., Carpenter J.K., Flores A., Saez L., Armani M.

Island plants are predicted to have weak or absent defenses as part of the island plant syndrome. Evidence supporting the weak island defense prediction stems largely from observations of intense damage from invasive mammalian herbivores on islands. However, this evidence is misleading because most oceanic island plants have not evolved with native mammalian herbivores, and so should not have evolved defenses against them. In contrast, many islands have been home to other native vertebrate megafaunal herbivores, including flightless birds, tortoises, and turtles, many of which are now extinct or rare and therefore easy to overlook as agents of selection for island plant defenses. We review the evidence that island megaherbivores have selected for spinescence in island plants, supplementing published data with new estimates of spinescence for island floras varying in historical legacies of megafaunal herbivores. While the proportions of spinescent species are generally low, there are many spinescent island plants, likely functioning in defense against extant herbivores or persisting as defense anachronisms, no longer functioning due to the losses of native island megaherbivores. Future research exploring the evolvability of spinescence, including rates of losses or gains as herbivory selection pressure shifts, will be particularly enlightening for assessing island plant defenses in response to complex and variable historical legacies of megafaunal herbivory.

da Rosa Á.A., Kerber L., Pinheiro F.L., Manfroi J.

Today’s Campos Sulinos have witnessed important paleogeographic, paleoclimatic, and paleoenvironmental shifts in the last 300 million years. When this history is evaluated through the perspective of fossil-bearing sedimentary rocks, it can be divided into four major events: Permian deglaciation and evolution to an alluvial plain in Pangean condition; Triassic recovery of a massive extinction and development in alluvial plains in Pangean circumstances; establishment of an aeolian system under desertic conditions during the Jurassic-Cretaceous; and the Pleistocene onset of megafauna and dominance of grassland vegetation responding to glacial and interglacial cycles. Permian biotas range from marine parareptiles, such as mesosaurs, to fully terrestrial fauna, including large herbivores such as provelosaurids, a saber-toothed herbivore, and large carnivores. Terrestrial environments were dominated by a Glossopteris Flora, with large pteridophytes and primitive gymnosperms. Triassic biota vary from near-the-water parareptiles, temnospondyls, and archosauromorphs, right after the most impressive mass extinction on our planet, to the onset of dinosaurs and the evolution of cynodonts. The Triassic also witnessed one of the main vegetation transitions in Earth’s history: environments once dominated by a Glossopteris Flora gradually became occupied by Dicroidium and Coniferous Floras. The Jurassic faunas are mostly represented by dinosaur footprints from a desert-dominated environment prior to the South America/Africa breakup. Late Pleistocene biota includes large-bodied mammals and reptiles, representatives of the so-called Pleistocene Megafauna. In addition, extant taxa are also present in the fossil record. The Late Pleistocene paleobotanic fossil record demonstrates widespread grasslands that were only slowly subject to the expansion of forests.