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Land use change is a key component of regional environmental change. In mountain regions, where conditions for agriculture and human life are often difficult, land use trends are dominated by changes in the population's distribution across rural and urban areas and shifts in the main human activities. In the Argentinian puna—a high-elevation subtropical plateau of about 95,000 km2 situated above 3200 masl—land is chiefly used for grazing, mining, and tourism. In this article, we analyze trends in these land uses over the last 57 years in the context of climatic changes toward drier and warmer conditions. Since 1960, the human population grew from 80,000 to 130,000; but this increase largely occurred in the scattered urban centers, while the rural population decreased. The main livestock— sheep—showed a net decrease of around 100,000 animals (–18.5%), with numbers increasing between 1960 and 1980 and then dropping markedly. The number of mining operations declined during the 1970s and 1980s and then rose sharply, reaching a 30% increase since the 1990s. Simultaneously, structural wild vicuña populations increased from a few thousand to around 130,000. These results show that environmental changes over the past half century involved a major wildlife recovery associated with a change from widespread extensive grazing to intensive but spatially limited impacts around mining operations and growing urban centers. Tourism emerged as a new activity over the last decades, but the environmental impacts have been poorly studied. To promote local development and regional conservation, research priorities should include (1) empirical assessments of the ecological consequences of land use changes, such as grazing regimes shifting from domestic to wild herbivores, as well as the impacts of mining, tourism, and urbanization on wetlands and hydrological regimes; (2) modeling of future scenarios of mining and tourism expansion and resulting conflicts with environmental conservation; and (3) coproduction of knowledge about interactions among land uses, climate change, and the different decision-making agents.

In most of the planet, large herbivore communities have been replaced by livestock, but this process is reversing in many places. Here, we outline and review the pathways of “megaherbivore rewilding transitions” in three social-ecological-systems of subtropical Argentina. In the extensive arid high-elevation Puna plateau we observed a “rapid rewilding pathway” where the reduction of livestock was accompanied by the recovery of native camelid populations from near extinction in a few decades. In the forest-grassland ecotone, decreasing livestock favored higher fire frequency, probably limiting the speed of native herbivore recovery in an “increasing fire pathway”. In lowland montane forests, the recovery of native herbivore communities appears to be lagged by fragmentation, local extinctions and human pressure, representing a case of “connectivity-limited rewilding”. These typologies exemplify the complexity of outcomes resulting from livestock diminishing density, and provide a framework to understand and optimize processes of large herbivore rewilding according to different social-ecological contexts.

Some of the most profound effects of climate change on ecological communities are due to alterations in species interactions rather than direct physiological effects of changing environmental conditions. Empirical evidence of historical changes in species interactions within climate-impacted communities is, however, rare and difficult to obtain. Here, we demonstrate the recent disappearance of key habitat-forming kelp forests from a warming tropical–temperate transition zone in eastern Australia. Using a 10-y video dataset encompassing a 0.6 °C warming period, we show how herbivory increased as kelp gradually declined and then disappeared. Concurrently, fish communities from sites where kelp was originally abundant but subsequently disappeared became increasingly dominated by tropical herbivores. Feeding assays identified two key tropical/subtropical herbivores that consumed transplanted kelp within hours at these sites. There was also a distinct increase in the abundance of fishes that consume epilithic algae, and much higher bite rates by this group at sites without kelp, suggesting a key role for these fishes in maintaining reefs in kelp-free states by removing kelp recruits. Changes in kelp abundance showed no direct relationship to seawater temperatures over the decade and were also unrelated to other measured abiotic factors (nutrients and storms). Our results show that warming-mediated increases in fish herbivory pose a significant threat to kelp-dominated ecosystems in Australia and, potentially, globally.

Eukaryotic cells acquired novel organelles during evolution through mechanisms that remain largely obscure. The existence of the unique oil body compartment is a synapomorphy of liverworts that represents lineage-specific acquisition of this organelle during evolution, although its origin, biogenesis, and physiological function are yet unknown. We find that two paralogous syntaxin-1 homologs in the liverwort Marchantia polymorpha are distinctly targeted to forming cell plates and the oil body, suggesting that these structures share some developmental similarity. Oil body formation is regulated by an ERF/AP2-type transcription factor and loss of the oil body increases M . polymorpha herbivory. These findings highlight a common strategy for the acquisition of organelles with distinct functions in plants, via periodical redirection of the secretory pathway depending on cellular phase transition. Liverworts have a unique oil body organelle unrelated to lipid stores found in other eukaryotes. Here the authors show that oil body formation is analogous to that of cell plates, relying on periodic redirection of the secretory pathway and a syntaxin-1 homolog, and that oil bodies contribute to defence against herbivory.

SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) genes, as unique plant transcription factors, play important roles in plant developmental regulation and stress response adaptation. Although mulberry is a commercially valuable tree species, there have been few systematic studies on SPL genes. In this work, we identified 15 full-length SPL genes in the mulberry genome, which were distributed on 4 Morus notabilis chromosomes. Phylogenetic analysis clustered the SPL genes from five plants (Malus × domestica Borkh, Populus trichocarpa, M. notabilis, Arabidopsis thaliana, and Oryza sativa) into five groups. Two zinc fingers (Zn1 and Zn2) were found in the conserved SBP domain in all of the MnSPLs. Comparative analyses of gene structures and conserved motifs revealed the conservation of MnSPLs within a group, whereas there were significant structure differences among groups. Gene quantitative analysis showed that the expression of MnSPLs had tissue specificity, and MnSPLs had much higher expression levels in older mulberry leaves. Furthermore, transcriptome data showed that the expression levels of MnSPL7 and MnSPL14 were significantly increased under silkworm herbivory. Molecular experiments revealed that MnSPL7 responded to herbivory treatment through promoting the transcription of MnTT2L2 and further upregulating the expression levels of catechin synthesis genes (F3′H, DFR, and LAR).

Prior to transitioning to a coral diet, juvenile Acanthaster cf. solaris, the Crown-of-Thorns Seastar (COTS), feed on crustose coralline algae. Although a detailed understanding of juvenile ecology is crucial to predict and prevent outbreaks, the exact timing of the transition is unresolved. Two experiments were conducted to measure time and size of COTS at the transition, and investigate potential modulating effects of different coral species. COTS began early transitions at similar sizes (7.5–8.5 mm), and these first transitions were observed around 136–145 d. Between 175 and 191 d, a 50% transition in the presence of Acropora tenuis was measured. After 175d, the percentage of COTS cohorts that had transitioned was significantly lower in A. millepora (38%) and Stylophora pistillata (7%) compared to A. tenuis (51%). These data fill important knowledge gaps in juvenile ecology, and the influence of coral species on transition suggests an undescribed feedback mechanism between prey and predator.

Herbivores can reach extraordinary abundances in many ecosystems. When herbivore abundance is high, heavy grazing can severely defoliate primary producers and, in some cases, even drive ecosystem to undergo regime shifts from a high productivity state to a denuded, low productivity state. While the phenomenon of herbivore-driven regime shifts is well documented, we only partially understand the mechanisms underlying these events. Here, we combine herbivory experiments with 21 years of long-term monitoring data of kelp forest ecosystems to test the hypothesis that herbivores drive regime shifts when herbivory exceeds primary production. To test this hypothesis, we quantified how the foraging habits of an important group of marine herbivores—sea urchins—change with increases in sea urchin biomass and trigger regime shifts to a foundation species, giant kelp (Macrocystis pyrifera). Using experiments, we quantified how the grazing capacity of urchins increases as urchin biomass increases, then we combined these estimates of urchin grazing capacity with estimates of kelp production to predict when and where urchin grazing capacity exceeded kelp production. When grazing capacity exceeded kelp production, sea urchins caused a 50-fold reduction in giant kelp biomass. Our findings support the hypothesis that the balance between herbivory and production underlies herbivore-driven regime shifts in Southern California kelp forests and provides insight into when and where urchins are likely to force regime shifts in kelp forest ecosystems.

Forest–grassland mosaics, with abrupt boundaries between the two vegetation types, occur across the globe. Fire and herbivory are widely considered primary drivers that maintain these mosaics by limiting tree establishment in grasslands, while edaphic factors and frosts are generally considered to be secondary factors that reinforce these effects. However, the relative importance of these drivers likely varies across systems. In particular, although frost is known to occur in many montane tropical mosaics, experimental evidence for its role as a driving factor is limited. We used replicated in situ transplant and warming experiments to examine the role of microclimate (frost and freezing temperatures) and soil in influencing germination and seedling survival of both native forest trees and alien invasive Acacia trees in grasslands of a tropical montane forest–grassland mosaic in the Western Ghats of southern India. Seed germination of both native and alien tree species was higher in grasslands regardless of soil type, indicating that germination was not the limiting stage to tree establishment. However, irrespective of soil type, native seedlings in grasslands incurred high mortality following winter frosts and freezing temperatures relative to native seedlings in adjoining forests where freezing temperatures did not occur. Seedling survival through the tropical winter was thus a primary limitation to native tree establishment in grasslands. In contrast, alien Acacia seedlings in grasslands incurred much lower levels of winter mortality. Experimental night‐time warming in grasslands significantly enhanced over‐winter survival of all tree seedlings, but increases were much greater for alien Acacia than for native tree seedlings. Synthesis. Our results provide evidence for a primary role for frost and freezing temperatures in limiting tree establishment in grasslands of this tropical montane forest–grassland mosaic. Future increases in temperature are likely to release trees from this limitation and favour tree expansion into grasslands, with rates of expansion of non‐native Acacia likely to be much greater than that of native trees. We suggest that studies of frost limitation to plant establishment are needed across a range of tropical ecosystems to re‐evaluate the general importance of frost as a driver of vegetation transitions in the tropics. Our study provides evidence for a primary role for frost and freezing temperatures in limiting tree establishment in grasslands of a tropical montane forest‐grassland mosaic. Future increases in temperature are likely to release trees from this limitation and favour tree expansion into grasslands, with non‐native woody species likely to expand at much greater rates than native trees (Photo credit: Prasenjeet Yadav).

In human financial and social systems, exchanges of information among individuals cause speculative bubbles, behavioral cascades, and other correlated actions that profoundly influence system-level function. Exchanges of information are also widespread in ecological systems, but their effects on ecosystem-level processes are largely unknown. Herbivory is a critical ecological process in coral reefs, where diverse assemblages of fish maintain reef health by controlling the abundance of algae. Here, we show that social interactions have a major effect on fish grazing rates in a reef ecosystem. We combined a system for observing and manipulating large foraging areas in a coral reef with a class of dynamical decision-making models to reveal that reef fish use information about the density and actions of nearby fish to decide when to feed on algae and when to flee foraging areas. This “behavioral coupling” causes bursts of feeding activity that account for up to 68% of the fish community’s consumption of algae. Moreover, correlations in fish behavior induce a feedback, whereby each fish spends less time feeding when fewer fish are present, suggesting that reducing fish stocks may not only reduce total algal consumption but could decrease the amount of algae each remaining fish consumes. Our results demonstrate that social interactions among consumers can have a dominant effect on the flux of energy and materials through ecosystems, and our methodology paves the way for rigorous in situ measurements of the behavioral rules that underlie ecological rates in other natural systems.

Background Although feeding behavior and food habit are ecologically and economically important properties, little is known about formation and evolution of herbivory. Grass carp ( Ctenopharyngodon idella ) is an ecologically appealing model of vertebrate herbivore, widely cultivated in the world as edible fish or as biological control agents for aquatic weeds. Grass carp exhibits food habit transition from carnivory to herbivory during development. However, currently little is known about the genes regulating the unique food habit transition and the formation of herbivory, and how they could achieve higher growth rates on plant materials, which have a relatively poor nutritional quality. Results We showed that grass carp fed with duckweed (modeling fish after food habit transition) had significantly higher relative length of gut than fish before food habit transition or those fed with chironomid larvae (fish without transition). Using transcriptome sequencing, we identified 10,184 differentially expressed genes between grass carp before and after transition in brain, liver and gut. By eliminating genes potentially involved in development (via comparing fish with or without food habit transition), we identified changes in expression of genes involved in cell proliferation and differentiation, appetite control, circadian rhythm, and digestion and metabolism between fish before and after food habit transition. Up-regulation of GHRb , Egfr , Fgf , Fgfbp1 , Insra , Irs2 , Jak , STAT , PKC , PI3K expression in fish fed with duckweed, consistent with faster gut growth, could promote the food habit transition. Grass carp after food habit transition had increased appetite signal in brain. Altered expressions of Per , Cry , Clock , Bmal2 , Pdp , Dec and Fbxl3 might reset circadian phase of fish after food habit transition. Expression of genes involved in digestion and metabolism were significantly different between fish before and after the transition. Conclusions We suggest that the food habit transition from carnivory to herbivory in grass carp might be due to enhanced gut growth, increased appetite, resetting of circadian phase and enhanced digestion and metabolism. We also found extensive alternative splicing and novel transcript accompanying food habit transition. These differences together might account for the food habit transition and the formation of herbivory in grass carp.