Crop domestication, global human-mediated migration, and the unresolved role of geography in pest control

Abstract

Ecological pest management seeks to improve pest control through the manipulation of ecological processes that promote natural enemies and suppress pests. These approaches can involve cultural practices such as reduced tillage, increased use of non-crop plants that provide food and shelter for natural enemies, and intercropping to enhance the abundance and diversity of natural enemies. A major assumption of ecological pest management is that these activities can be equally effective for all insect herbivores. Here, I propose that these strategies may only be effective for a subset of pests and geographic regions because most insect pests have complex evolutionary histories that make them difficult to manage. I discuss how crop domestication and human-mediated migration are major evolutionary events that shape the geography of interactions between plants, herbivores, and natural enemies. Insect herbivores can evolve to be pests through three major modes: 1) herbivores associated with the crop wild ancestor may shift onto the domesticated crop, 2) herbivores may host-shift from native host plants onto an introduced crop, or 3) human-mediated migration can introduce insect pests into new cropping regions. The resulting geographic structure can influence the success of pest management by altering ecological factors such as: species distributions, patterns of biodiversity, community structure, and natural enemy attack rates. I discuss how the different modes of insect pest evolution structure a set of relevant questions and approaches for ecological pest management. By acknowledging how agricultural history and geography shape the ecology and evolution of insect pests, we may collectively develop a better capacity to identify where and how ecological pest management approaches can be most broadly effective.

Did maize domestication and early spread mediate the population genetics of corn leafhopper?

“…The study of crop domestication and agricultural evolution is relevant to understanding contemporary agriculture and can inform the design of agricultural systems to sustainably feed and clothe society into the future. However, while a substantial amount of research addresses fundamental agronomic questions concerning domestication and agricultural evolution, such as their environmental contexts (e.g., Araus et al ., , , ), less research specifically addresses the relevance of crop domestication and early spread and improvement to contemporary pest management (Chen et al ., ; Chen, ). Indeed, while much is known concerning the chronology and genetics of domestication and spread of important crops, for example, maize ( Zea mays mays L.) (Staller et al ., ; Kato et al ., ; Staller, ; Hufford et al ., ; Blake, ), comparatively little is known about how today's pest assemblages may have been shaped partly by agricultural, ecological and evolutionary processes over the last ∼10K years.…”

“…Similarly, crop domestication may have altered trophic interactions among crop plants, herbivores, and herbivore antagonists, such as parasitoids, so that herbivores are more abundant on crop plants compared to crop wild ancestors (Macfadyen & Bohan, ). For example, common‐garden studies showed that the abundances of important pests of sunflower and maize were higher in crops compared to crop wild ancestors, partly due to enhanced performance and lower parasitism of those pests on the former compared to the latter hosts (Bernal et al ., ; Chen, ). Overall, the evidence accumulated to date shows that crop domestication and the spread of agriculture mediated the evolution and ecology of herbivores that are presently considered pests (Medina et al ., ; Chen et al ., ; Chen, ; Medina, ; Forbes et al ., ).…”

Diversity and abundance of lepidopteran stem borers and their host plants in Ethiopia

“…Insect herbivores switch more easily between closely related plants (Brandle & Brandl, ) and typically perform better on agricultural plants than on wild ancestors due to reductions in secondary compounds during crop domestication (Chen, ). Resource concentration hypothesis (Root, ) also suggests that if plant species are more abundant or nearly pure stands, insects are able to specialize on them and often do so.…”

“…Insect herbivores switch more easily between closely related plants (Brandle & Brandl, 2001) and typically perform better on agricultural plants than on wild ancestors due to reductions in secondary compounds during crop domestication (Chen, 2016).…”

Back to the Origin: In Situ Studies Are Needed to Understand Selection during Crop Diversification

“…Under climate change, these pressures are predicted to intensify (Hatfield et al, 2010). Perhaps because centers of origin tend to be the geographic source for the major diseases (Leppik, 1970) and insect pests of crops (Chen, 2016), they are also the source for genes for resistance (Harlan, 1976;Hijmans et al, 2003;Zhang et al, 2017), insect natural enemies (van den Bosch, 1971;van Driesche et al, 2008), and microbes (Philippot et al, 2013;Perez-Jaramillo et al, 2016) that help plants to resist pests and tolerate abiotic stress.…”