Evolutionary history predicts high‐impact invasions by herbivorous insects

Abstract

A long‐standing goal of invasion biology is to identify factors driving highly variable impacts of non‐native species. Although hypotheses exist that emphasize the role of evolutionary history (e.g., enemy release hypothesis & defense‐free space hypothesis), predicting the impact of non‐native herbivorous insects has eluded scientists for over a century.Using a census of all 58 non‐native conifer‐specialist insects in North America, we quantified the contribution of over 25 factors that could affect the impact they have on their novel hosts, including insect traits (fecundity, voltinism, native range, etc.), host traits (shade tolerance, growth rate, wood density, etc.), and evolutionary relationships (between native and novel hosts and insects).We discovered that divergence times between native and novel hosts, the shade and drought tolerance of the novel host, and the presence of a coevolved congener on a shared host, were more predictive of impact than the traits of the invading insect. These factors built upon each other to strengthen our ability to predict the risk of a non‐native insect becoming invasive. This research is the first to empirically support historically assumed hypotheses about the importance of evolutionary history as a major driver of impact of non‐native herbivorous insects.Our novel, integrated model predicts whether a non‐native insect not yet present in North America will have a one in 6.5 to a one in 2,858 chance of causing widespread mortality of a conifer species if established (R 2 = 0.91) Synthesis and applications. With this advancement, the risk to other conifer host species and regions can be assessed, and regulatory and pest management efforts can be more efficiently prioritized.

The Risk of Bark and Ambrosia Beetles Associated with Imported Non-Coniferous Wood and Potential Horizontal Phytosanitary Measures

“…However, counter examples offered by other studies suggest that one should be wary of generalising. Mech et al [26] reviewed 58 non-native conifer-specialist insects in North America, belonging to five orders, 20 families, and five feeding guilds, and concluded that insect life history traits comparable to those examined in the present study (reproductive strategy, polyphagy, pest status, dispersal, etc.) had little predictive value regarding the impact of these species in new territories, whilst factors related to the newly colonised areas (shared evolutionary history of the native and novel hosts, shade, drought tolerance of the novel hosts, absence of a coevolved congener on a shared host) were better predictors.…”

Negative effects of an allelopathic invader on AM fungal plant species drive community‐level responses

“…For example, by understanding how herbivorous insects identify their host plants, we can anticipate the species‐specific impacts of invasive plants or insects on other trophic levels in the native food web (Pearse and Altermatt 2013, Desurmont and Pearse 2014). Moreover, evolutionary divergence time between native range host tree and invaded range host trees is a strong predictor of high impacts of introduced insects on forests (Mech et al 2019). For trophic interactions (such as herbivory, above), the mechanism of impact is a function of diet, and can be relatively straightforward and consistent across space and time.…”

Phylogenetic escape from pests reduces pesticides on some crop plants

“…Comparative models of agricultural economics (10), introduced species (31, 32), and injury thresholds (33) can guide actions to optimize the control of pests in crop species and to minimize pesticide use. Phylogenetic relationships have been used to explain major patterns in ecology (34,35), and there is substantial promise to applying phylogenetic tools to address pressing problems in coping with disease and herbivory (29,30,36). We show that phylogeny predicts variation in pests and pesticide use in diverse cropping systems.…”

“…Many introduced pests did not historically interact with the crop that they damage, so they have expanded their host range in doing so. The phylogenetic breadth of hosts consumed by that pest (its degree of diet generalism or specialization) and the phylogenetic distance from its ancestral hosts to a crop may help determine its likelihood of establishment (29) and impact (30).…”