Rapid phenological change differs across four trophic levels over 15 years

Host-Parasitoid Phenology, Distribution, and Biological Control under Climate Change

Climate change raises a serious threat to global entomofauna-the foundation of many ecosystems-by threatening species preservation and the ecosystem services they provide. Already, changes in climate-warming-are causing (i) sharp phenological mismatches among host-parasitoid systems by reducing the window of host susceptibility, leading to early emergence of either the host or its associated parasitoid and affecting mismatched species' fitness and abundance; (ii) shifting arthropods' expansion range towards higher altitudes, and therefore migratory pest infestations are more likely; and (iii) reducing biological control effectiveness by natural enemies, leading to potential pest outbreaks. Here, we provided an overview of the warming consequences on biodiversity and functionality of agroecosystems, highlighting the vital role that phenology plays in ecology. Also, we discussed how phenological mismatches would affect biological control efficacy, since an accurate description of stage differentiation (metamorphosis) of a pest and its associated natural enemy is crucial in order to know the exact time of the host susceptibility/suitability or stage when the parasitoids are able to optimize their parasitization or performance. Campaigns regarding landscape structure/heterogeneity, reduction of pesticides, and modelling approaches are urgently needed in order to safeguard populations of natural enemies in a future warmer world.

Current and lagged climate affects phenology across diverse taxonomic groups

The timing of life events (phenology) can be influenced by climate. Studies from around the world tell us that climate cues and species' responses can vary greatly. If variation in climate effects on phenology is strong within a single ecosystem, climate change could lead to ecological disruption, but detailed data from diverse taxa within a single ecosystem are rare. We collated first sighting and median activity within a high-elevation environment for plants, insects, birds, mammals and an amphibian across 45 years (1975-2020). We related 10 812 phenological events to climate data to determine the relative importance of climate effects on species' phenologies. We demonstrate significant variation in climate-phenology linkage across taxa in a single ecosystem. Both current and prior climate predicted changes in phenology. Taxa responded to some cues similarly, such as snowmelt date and spring temperatures; other cues affected phenology differently. For example, prior summer precipitation had no effect on most plants, delayed first activity of some insects, but advanced activity of the amphibian, some mammals, and birds. Comparing phenological responses of taxa at a single location, we find that important cues often differ among taxa, suggesting that changes to climate may disrupt synchrony of timing among taxa.

Rapid decline of a four-trophic-level system over a 15-year period

Recent climate change has produced a wide range of shifts in the phenology of species and consequent changes in the relationships among them. However, a dearth of studies exists that evaluates an entire trophic pyramid over an extended period. Here I characterize changes in several important variables on such a multitrophic suite of species, which contains two primary producers (sensitive and marsh ferns Onoclea sensibilis and Thelypteris palustris), one herbivore (caterpillars of the fern moth Herpetogramma theseusalis), one primary parasitoid (the braconid wasp Alabagrus texanus), and three facultative hyperparasitoids (including the eulophid wasp Aprostocetus sp.). I ask how the abundance of these species changes over time, how parasitism and mortality change along with the plants an herbivore selects, how the relationships between the different trophic levels change, and what effect these results play in the makeup of a trophic pyramid. Herbivores prospered most on sensitive fern, while levels of parasitism and mortality on herbivores and primary parasitoids remained relatively similar over the study period. However, facultative hyperparasitoids declined strikingly, and the few remaining individuals increased their exploitation of caterpillars (vs. Alabagrus), further decreasing the impact of the fourth trophic level. Since a previous study demonstrated that phenological change by these primary parasitoids exceeds that of their herbivore, further breakdown of the system appears likely.