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Predation is an important ecological process that can significantly impact the maintenance of ecosystem services. In arctic environments, the relative ecological importance of predation is thought to be increasing due to climate change, partly because of increased productivity with rising temperatures. Therefore, understanding predator–prey interactions in arctic ecosystems is vital for the sustainable management of these northern regions. Network theory provides a framework for quantifying the structures of ecological interactions. In this study, we use dietary observations on mammalian and avian predators in a high arctic region, including isolated peninsulas on Ellesmere Island and north Greenland, to construct bipartite trophic networks. We quantify the complexity, specialization, and nested as well as modular structures of these networks and also determine if these properties varied among the peninsulas. Mammal prey remains were the dominant diet item for all predators, but there was spatial variation in diet composition among peninsulas. The predator–prey networks were less complex, had more specialized interactions, and were more nested and more modular than random expectations. However, the networks displayed only moderate levels of modularity. Predator species had less specialized interactions with prey than prey had with predators. All network properties differed among the peninsulas, which highlights that ecosystems often show complex responses to environmental characteristics. We suggest that gaining knowledge about spatial variation in the characteristics of predator–prey interactions can enhance our ability to manage ecosystems exposed to environmental perturbations, particularly in high arctic environments subject to rapid environmental change. [ABSTRACT FROM AUTHOR]

Predation is an important ecological process that can significantly impact the maintenance of ecosystem services. In arctic environments, the relative ecological importance of predation is thought to be increasing due to climate change, partly because of increased productivity with rising temperatures. Therefore, understanding predator–prey interactions in arctic ecosystems is vital for the sustainable management of these northern regions. Network theory provides a framework for quantifying the structures of ecological interactions. In this study, we use dietary observations on mammalian and avian predators in a high arctic region, including isolated peninsulas on Ellesmere Island and north Greenland, to construct bipartite trophic networks. We quantify the complexity, specialization, and nested as well as modular structures of these networks and also determine if these properties varied among the peninsulas. Mammal prey remains were the dominant diet item for all predators, but there was spatial variation in diet composition among peninsulas. The predator–prey networks were less complex, had more specialized interactions, and were more nested and more modular than random expectations. However, the networks displayed only moderate levels of modularity. Predator species had less specialized interactions with prey than prey had with predators. All network properties differed among the peninsulas, which highlights that ecosystems often show complex responses to environmental characteristics. We suggest that gaining knowledge about spatial variation in the characteristics of predator–prey interactions can enhance our ability to manage ecosystems exposed to environmental perturbations, particularly in high arctic environments subject to rapid environmental change. [ABSTRACT FROM AUTHOR]

Buxus balearica Lam., Ephedra fragilis Desf., and Juniperus oxycedrus L. are three Pre-Mediterranean shrubs that have become scarce in the Balearic Islands probably due to a climatic change and the anthropogenic activities during the second half of the Holocene. In addition, an endemic artiodactyl, Myotragus balearicus, exerted browsing pressure on these species for thousands of years, and after it disappeared domestic goats were introduced by humans. Adaptations that enable these plants to resist grazing are structural or chemical; however, there is no information about whether their defenses are only constitutive or also inducible. Currently, the mountain ranges of Majorca Island are extensively occupied by feral goats, and a possible increase in the stocking rates could affect the survival of these plant species. The aim of this study was to evaluate and compare the effects of simulated severe browsing on the re-growth capacity and chemical composition of these species in order to determine their tolerance to herbivory. We sampled and compared structural and chemical variables of saplings submitted to two pruning intensities for each species. The results showed that all three species could maintain their growth rate and biomass ratios under simulated herbivory. Sprout production was also stimulated in all them. E. fragilis and B. balearica increased phenolic content after pruning, and E. fragilis also increased the condensed tannins. Pruning treatments did not trigger induction of phenolic content in J. oxycedrus , which could be considered as a constitutive defense. It is noteworthy that alkaloids in E. fragilis decreased with the treatments, which may contribute to preventing a possible addiction to these compounds, and thus reduce browsing damage. The responses induced by pruning show that these species are very tolerant to a level of herbivory, which could indicate a good adaptation to browsing pressure, exerted since the Pleistocene by Myotragus balearicus, and followed by goats during the last millennia. This is especially relevant in Mediterranean islands, such as the Balearic Islands, where practices for conserving relict plant species are based on feral herbivore exclusion. • An increase of feral goat stocking rates in Mallorca could affect the survival of some shrubs. • The effects of simulated browsing on the re-growth and chemical composition of these species was studied. • Buxus balearica , Ephedra fragilis and Juniperus oxycedrus maintained their growth rate and biomass under simulated herbivory. • The responses induced by pruning show that these species are very tolerant to a level of herbivory. • That tolerance indicates a good adaptation to browsing pressure, exerted since the Pleistocene by Myotragus balearicus. [ABSTRACT FROM AUTHOR]