Population expansion and genomic adaptation to agricultural environments of the soybean looper, Chrysodeixis includens

Abstract

Evolutionary studies of insect pests improve our ability to anticipate problems in agricultural ecosystems, such as pest outbreaks, control failures, or expansions of the host range. Here, we investigated the mechanisms underlying the evolutionary processes behind the recent census size expansion and local adaptation of Chrysodeixis includens. First, we sequenced mitochondrial markers to conduct a phylogeographic investigation of C. includens historical processes. Then, we combined a de novo genotyping‐by‐sequencing approach with a study of agricultural landscapes to uncover recent processes of adaptation. Primarily, we found low genetic diversity across all markers and clear indications of a recent demographic expansion. We also found a lack of significant isolation by distance (IBD), and weak or absent genetic structure considering geographic locations. However, we did find initial signs of population differentiation that were associated with host plant types (i.e., soybean and cotton). Agricultural landscape attributes, including soybean crops, were significantly associated with putative markers under positive selection. Moreover, positive selection associated with host differentiation was putatively linked to digestive enzymes. This study showed how landscape composition and host plants can affect the evolutionary process of agricultural pest insects such as C. includens.

Large-scale assessment of lepidopteran soybean pests and efficacy of Cry1Ac soybean in Brazil

“…Both cotton and soybean have been documented as suitable hosts of C. includens 38 – 41 . The large increase in soybean cultivation area in Brazil seems to be a particularly important component in C. includens adaptation 31 . Soybean farms now are predominant in the agricultural landscape, narrowing the host plant availability to C. includens in some regions 31 .…”

“…The large increase in soybean cultivation area in Brazil seems to be a particularly important component in C. includens adaptation 31 . Soybean farms now are predominant in the agricultural landscape, narrowing the host plant availability to C. includens in some regions 31 . Increases in cultivation of other crop and non-crop hosts of C. includens also may have created a “green bridge” favoring the growth and spread of populations 7 , 31 .…”

“…Soybean farms now are predominant in the agricultural landscape, narrowing the host plant availability to C. includens in some regions 31 . Increases in cultivation of other crop and non-crop hosts of C. includens also may have created a “green bridge” favoring the growth and spread of populations 7 , 31 . This likely increased the selective pressure of insecticides and Bt soybean plants, leading to higher resistance risk for these control tactics.…”

“…Nevertheless, poor compliance with refuge recommendations has been a common factor in most cases of documented field-evolved resistance to Bt crops 25 – 29 . Moreover, the intensive use of agricultural land creates an environment conducive to the buildup of relatively large insect pest populations and multiple generations of pests potentially under selection of Bt crops or insecticides 30 , 31 . “Tropical agriculture” such as that practiced in Brazil is typically based on two or more crop seasons per year, allowing pest populations to go through multiple generations per year on Bt crops and consequently increasing selection pressure 30 .…”

Filogeografia molecular de >i<Thyrinteina arnobia>/i< (Lepidoptera: Geometridae) e >i<Gonipterus>/i< spp. (Coleoptera: Curculionidae) no Brasil

“…Dessa forma, a filogeografia vem como uma ferramenta capaz de explorar aspectos da diversidade das espécies, cada vez mais sendo utilizada na entomologia. Possibilitando averiguar os padrões locais de dispersão, fluxo gênico, estruturação populacional e distribuição espacial dos genótipos dos organismos estudados, ampliando o entendimento sobre processos evolutivos e gerando novas perspectivas para o manejo integrado de pragas (CORREA et al, 2019;FRESIA et al, 2013;PERETOLCHINA et al, 2018;SILVA et al, 2020;STRÖHER et al, 2019).…”