Current ecological communities are in a constant state of flux from climate change and from species introductions. Recent discussion has focused on the positive roles introduced species can play in ...ecological communities and on the importance of conserving resilient ecosystems, but not how these two ideas intersect. There has been insufficient work to define the attributes needed to support ecosystem resilience to climate change in modern communities. Here, I argue that non‐invasive, introduced plant species could play an important role in supporting the resilience of terrestrial ecosystems to climate change. Using examples from multiple taxonomic groups and ecosystems, I discuss how introduced plants can contribute to ecosystem resilience via their roles in plant and insect communities, as well as their associated ecosystem functions. I highlight the current and potential contributions of introduced plants and where there are critical knowledge gaps. Determining when and how introduced plants are contributing to the resilience of ecosystems to climate change will contribute to effective conservation strategies.
In this perspective, I argue that we need to rethink the way we consider introduced plants in the resiliency of ecosystems to climate change. Given the ability of introduced species to tolerate and adapt to a broad range of environmental conditions, I suggest that introduced plants may fulfill a similar functional role as native plants that have been lost and/or provide a critical role that cannot (yet) be performed by ‘local’ native plant species. I propose that we need a clearer picture of the complex roles that introduced species play in our ecosystems and how they respond to climate change.
The performance and population dynamics of insect herbivores depend on the nutritive and defensive traits of their host plants. The literature on plant-herbivore interactions focuses on plant trait ...mean values, but recent studies showing the importance of plant genetic diversity for herbivores suggest that plant trait variance may be equally important. The consequences of plant trait variance for herbivore performance, however, have been largely overlooked. Here we report an extensive assessment of the effects of within-population plant trait variance on herbivore performance using 457 performance datasets from 53 species of insect herbivores. We show that variance in plant nutritive traits substantially reduces mean herbivore performance via non-linear averaging of performance relationships that were overwhelmingly concave down. By contrast, relationships between herbivore performance and plant defence levels were typically linear, with variance in plant defence not affecting herbivore performance via non-linear averaging. Our results demonstrate that plants contribute to the suppression of herbivore populations through variable nutrient levels, not just by having low average quality as is typically thought. We propose that this phenomenon could play a key role in the suppression of herbivore populations in natural systems, and that increased nutrient heterogeneity within agricultural crops could contribute to the sustainable control of insect pests in agroecosystems.
Phenological responses to climate change (e.g., earlier leaf-out or egg hatch date) are now well documented and clearly linked to rising temperatures in recent decades. Such shifts in the phenologies ...of interacting species may lead to shifts in their synchrony, with cascading community and ecosystem consequences. To date, single-system studies have provided no clear picture, either finding synchrony shifts may be extremely prevalent Mayor SJ, et al. (2017) Sci Rep 7:1902 or relatively uncommon Iler AM, et al. (2013) Glob Chang Biol 19:2348–2359, suggesting that shifts toward asynchrony may be infrequent. A meta-analytic approach would provide insights into global trends and how they are linked to climate change. We compared phenological shifts among pairwise species interactions (e.g., predator–prey) using published long-term time-series data of phenological events from aquatic and terrestrial ecosystems across four continents since 1951 to determine whether recent climate change has led to overall shifts in synchrony. We show that the relative timing of key life cycle events of interacting species has changed significantly over the past 35 years. Further, by comparing the period before major climate change (pre-1980s) and after, we show that estimated changes in phenology and synchrony are greater in recent decades. However, there has been no consistent trend in the direction of these changes. Our findings show that there have been shifts in the timing of interacting species in recent decades; the next challenges are to improve our ability to predict the direction of change and understand the full consequences for communities and ecosystems.
Climate change has led to widespread shifts in the timing of key life history events between interacting species (phenological asynchrony) with hypothesized cascading negative fitness impacts on one ...or more of the interacting species—often termed ‘mismatch’. Yet, predicting the types of systems prone to mismatch remains a major hurdle. Recent reviews have argued that many studies do not provide strong evidence of the underlying match‐mismatch hypothesis, but none have quantitatively analysed support for it. Here, we test the hypothesis by estimating the prevalence of mismatch across antagonistic trophic interactions in terrestrial systems and then examine whether studies that meet the assumptions of the hypothesis are more likely to find a mismatch. Despite a large range of synchrony to asynchrony, we did not find general support for the hypothesis. Our results thus question the general applicability of this hypothesis in terrestrial systems, but they also suggest specific types of data missing to robustly refute it. We highlight the critical need to define resource seasonality and the window of ‘match’ for the most rigorous tests of the hypothesis. Such efforts are necessary if we want to predict systems where mismatches are likely to occur.
We test for support for the match‐mismatch hypothesis by estimating the prevalence of mismatch across antagonistic consumer–resource interactions in terrestrial systems and then examine whether studies that meet the assumptions of the hypothesis are more likely to find a mismatch. The lack of support we found for the hypothesis questions its general applicability in terrestrial systems, but our results also suggest specific types of data missing to robustly refute it. We highlight the critical need to define resource seasonality and the window of ‘match’ for the most rigorous tests of the hypothesis.
The negative impacts of non‐native species have been well documented, but some non‐natives can play a positive role in native ecosystems. One way that non‐native plants can positively interact with ...native butterflies is by provisioning nectar. Relatively little is known about the role of phenology in determining native butterfly visitation to non‐native plants for nectar, yet flowering time directly controls nectar availability. Here we investigate the phenological patterns of flowering by native and non‐native plants and nectar foraging by native butterflies in an oak savanna on Vancouver Island, British Columbia, Canada. We also test whether native butterflies select nectar sources in proportion to their availability. We found that non‐native plants were well integrated into butterfly nectar diets (83% of foraging observations) and that visitation to non‐natives increased later in the season when native plants were no longer flowering. We also found that butterflies selected non‐native flowers more often than expected based on their availability, suggesting that these plants represent a potentially valuable resource. Our study shows that non‐native species have the potential to drive key species interactions in seasonal ecosystems. Management regimes focused on eradicating non‐native species may need to reconsider their aims and evaluate resources that non‐natives provide.
The mechanisms of phenology Chmura, Helen E.; Kharouba, Heather M.; Ashander, Jaime ...
Ecological monographs,
02/2019, Volume:
89, Issue:
1
Journal Article
Peer reviewed
Open access
Species across a wide range of taxa and habitats are shifting phenological events in response to climate change. While advances are common, shifts vary in magnitude and direction within and among ...species, and the basis for this variation is relatively unknown. We examine previously suggested patterns of variation in phenological shifts in order to understand the cue–response mechanisms that underlie phenological change. Here, we review what is known about the mechanistic basis for nine factors proposed to predict phenological change (latitude, elevation, habitat type, trophic level, migratory strategy, ecological specialization, species' seasonality, thermoregulatory mode, and generation time). We find that many studies either do not identify a specific underlying mechanism or do not evaluate alternative mechanistic hypotheses, limiting the ability of scientists to predict future responses to global change with accuracy. We present a conceptual framework that emphasizes a critical distinction between environmental (cue-driven) and organismal (response-driven) mechanisms causing variation in phenological shifts and discuss how this distinction can reduce confusion in the field and improve predictions of future phenological change.
Forecasting species’ responses to climate change is critical and challenging.One commonly used approach is space-for-time substitution (SFTS), which takes the hypothesis that the biotic–climate ...relationships observed over space are causal, and uses this spatial relationship to predict responses over time.The underlying assumptions have seldom been tested; if not supported, the resulting predictions can be biased and have a high degree of uncertainty.We currently cannot discern for which type of species the SFTS approach is likely to be more reliable.We argue that the way forward is to test the underlying assumptions by evaluating contexts and species using a comparative approach, through improvements in the quality of biological data, and through the integration of experimental and modelling approaches to the distribution of species.
To anticipate species’ responses to climate change, ecologists have largely relied on the space-for-time-substitution (SFTS) approach. However, the hypothesis and its underlying assumptions have been poorly tested. Here, we detail how the efficacy of using the SFTS approach to predict future locations will depend on species’ traits, the ecological context, and whether the species is declining or introduced. We argue that the SFTS approach will be least predictive in the contexts where we most need it to be: forecasting the expansion of the range of introduced species and the recovery of threatened species. We highlight how evaluating the underlying assumptions, along with improved methods, will rapidly advance our understanding of the applicability of the SFTS approach, particularly in the context of modelling the distribution of species.
To anticipate species’ responses to climate change, ecologists have largely relied on the space-for-time-substitution (SFTS) approach. However, the hypothesis and its underlying assumptions have been poorly tested. Here, we detail how the efficacy of using the SFTS approach to predict future locations will depend on species’ traits, the ecological context, and whether the species is declining or introduced. We argue that the SFTS approach will be least predictive in the contexts where we most need it to be: forecasting the expansion of the range of introduced species and the recovery of threatened species. We highlight how evaluating the underlying assumptions, along with improved methods, will rapidly advance our understanding of the applicability of the SFTS approach, particularly in the context of modelling the distribution of species.
Variation among species in their phenological responses to temperature change suggests that shifts in the relative timing of key life cycle events between interacting species are likely to occur ...under climate warming. However, it remains difficult to predict the prevalence and magnitude of these shifts given that there have been few comparisons of phenological sensitivities to temperature across interacting species. Here, we used a broad‐scale approach utilizing collection records to compare the temperature sensitivity of the timing of adult flight in butterflies vs. flowering of their potential nectar food plants (days per °C) across space and time in British Columbia, Canada. On average, the phenology of both butterflies and plants advanced in response to warmer temperatures. However, the two taxa were differentially sensitive to temperature across space vs. across time, indicating the additional importance of nontemperature cues and/or local adaptation for many species. Across butterfly–plant associations, flowering time was significantly more sensitive to temperature than the timing of butterfly flight and these sensitivities were not correlated. Our results indicate that warming‐driven shifts in the relative timing of life cycle events between butterflies and plants are likely to be prevalent, but that predicting the magnitude and direction of such changes in particular cases is going to require detailed, fine‐scale data.
Changing temperature can substantially shift ecological communities by altering the strength and stability of trophic interactions. Because many ecological rates are constrained by temperature, new ...approaches are required to understand how simultaneous changes in multiple rates alter the relative performance of species and their trophic interactions. We develop an energetic approach to identify the relationship between biomass fluxes and standing biomass across trophic levels. Our approach links ecological rates and trophic dynamics to measure temperature‐dependent changes to the strength of trophic interactions and determine how these changes alter food web stability. It accomplishes this by using biomass as a common energetic currency and isolating three temperature‐dependent processes that are common to all consumer–resource interactions: biomass accumulation of the resource, resource consumption and consumer mortality. Using this framework, we clarify when and how temperature alters consumer to resource biomass ratios, equilibrium resilience, consumer variability, extinction risk and transient vs. equilibrium dynamics. Finally, we characterise key asymmetries in species responses to temperature that produce these distinct dynamic behaviours and identify when they are likely to emerge. Overall, our framework provides a mechanistic and more unified understanding of the temperature dependence of trophic dynamics in terms of ecological rates, biomass ratios and stability.
Despite the challenges posed by climate change and the biodiversity crisis, most academic research continues to stay within academia and the gaps between conservation science, policy, and practice ...remain intact. We need to improve the exchange of evidence between researchers and conservation practitioners and focus on solutions-oriented, interdisciplinary science and co-developed research. As we continue to break climate records and lose record numbers of species every year, now is the time for academics to think and act beyond their institutions.
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