Effects of habitat destruction on coevolving metacommunities

The coevolutionary consequences of biodiversity change

Coevolutionary selection is a powerful process shaping species interactions and biodiversity. Anthropogenic global environmental change is reshaping planetary biodiversity, including by altering the structure and intensity of interspecific interactions. However, remarkably little is understood of how coevolutionary selection is changing in the process. Here, we outline three interrelated pathways - change in evolutionary potential, change in community composition, and shifts in interaction trait distributions - that are expected to redirect coevolutionary selection under biodiversity change. Assessing how both ecological and evolutionary rules governing species interactions are disrupted under anthropogenic global change is of paramount importance to understand the past, present, and future of Earth's biodiversity.

Coevolutionary hotspots favour dispersal and fuel biodiversity in mutualistic landscapes under environmental changes

Mutualistic interactions are key to sustaining Earth's biodiversity. Yet, we are only beginning to understand how coevolution in mutualistic assemblages can shape the distribution and persistence of species across landscapes. Here, we combine the geographic mosaic theory of coevolution with metacommunity dynamics to understand how geographically structured selection can shape patterns of richness, dispersal, extinction and persistence of mutualistic species. In this model, species may experience strong or weak reciprocal selection imposed by mutualisms within each patch (i.e. hotspots and coldspots, respectively). Using numerical simulations, we show that mutualistic coevolution leads to a concentration of species richness at hotspots. Such an effect occurs because hotspots sustain higher rates of colonization and lower rates of extinction than coldspots, whether the environment changes or not. Importantly, under environmental changes, coldspots fail to sustain a positive colonization-to-extinction balance. Rather, species persistence within coldspots relies on hotspots acting as biodiversity sources and enhancing population dispersal across the landscape. In fact, even a few hotspots in the landscape can fuel the spatial network of dispersal of populations in the metacommunity. Our study highlights that coevolutionary hotspots can act as biodiversity sources, favouring colonization and allowing species to expand their distribution across landscapes even in changing environments. This article is part of the theme issue 'Diversity-dependence of dispersal: interspecific interactions determine spatial dynamics'.

Multi-scale effects of habitat loss and the role of trait evolution

Habitat loss (HL) is a major cause of species extinctions. Although the effects of HL beyond the directly impacted area have been previously observed, they have not been modelled explicitly, especially in an eco-evolutionary context. To start filling this gap, we study a two-patch deterministic consumer-resource model, with one of the patches experiencing loss of resources as a special case of HL. Our model allows foraging and mating within a patch as well as between patches. We then introduce heritable variation in consumer traits related to resource utilization and patch use to investigate eco-evolutionary dynamics and compare results with constant and no trait variation scenarios. Our results show that HL in one patch can indeed reduce consumer densities in the neighbouring patch but can also increase consumer densities in the neighbouring patch when the resources are overexploited. Yet at the landscape scale, the effect of HL on consumer densities is consistently negative. Patch isolation increases consumer density in the patch experiencing HL but has generally negative effects on the neighbouring patch, with context-dependent results at the landscape scale. With high cross-patch dependence and coupled foraging and mating preferences, local HL can sometimes even lead to landscape-level consumer extinction. Eco-evolutionary dynamics can rescue consumers from such extinction in some cases if their death rates are sufficiently small. More generally, trait evolution had positive or negative effects on equilibrium consumer densities after HL, depending on the evolving trait and the spatial scale considered. In summary, our findings show that HL at a local scale can affect the neighbouring patch and the landscape as a whole, where heritable trait variation can, in some cases, alleviate the impact of HL. We thus suggest joint consideration of multiple spatial scales and trait variation when assessing and predicting the impacts of HL.

The Resilience of Plant-Pollinator Networks

There is growing awareness of pollinator declines worldwide. Conservation efforts have mainly focused on finding the direct causes, while paying less attention to building a systemic understanding of the fragility of these communities of pollinators. To fill this gap, we need operational measures of network resilience that integrate two different approaches in theoretical ecology. First, we should consider the range of conditions compatible with the stable coexistence of all of the species in a community. Second, we should address the rate and shape of network collapse once this safe operational space is exited. In this review, we describe this integrative approach and consider several mechanisms that may enhance the resilience of pollinator communities, chiefly rewiring the network of interactions, increasing heterogeneity, allowing variance, and enhancing coevolution. The most pressing need is to develop ways to reduce the gap between these theoretical recommendations and practical applications. This perspective shifts the emphasis from traditional approaches focusing on the equilibrium states to strategies that allow pollination networks to cope with global environmental change.