More than one million copies of the ∼300-bp Alu element are interspersed throughout the human genome, with up to 75% of all known genes having Alu insertions within their introns and/or UTRs. Transcribed Alu sequences can alter splicing patterns by generating new exons, but other impacts of intragenic Alu elements on their host RNA are largely unexplored. Recently, repeat elements present in the introns or 3′-UTRs of 15 human brain RNAs have been shown to be targets for multiple adenosine to inosine (A-to-I) editing. Using a statistical approach, we find that editing of transcripts with embedded Alu sequences is a global phenomenon in the human transcriptome, observed in 2674 (∼2%) of all publicly available full-length human cDNAs (n = 128,406), from >250 libraries and >30 tissue sources. In the vast majority of edited RNAs, A-to-I substitutions are clustered within transcribed sense or antisense Alu sequences. Edited bases are primarily associated with retained introns, extended UTRs, or with transcripts that have no corresponding known gene. Therefore, Alu-associated RNA editing may be a mechanism for marking nonstandard transcripts, not destined for translation

A successful biological invasion involves survival in a newly occupied environment. If a population bottleneck occurs during an invasion, the resulting depletion of genetic variants could cause increased inbreeding depression and decreased adaptive potential, which may result in a fitness reduction. How invasive populations survive in the newly occupied environment despite reduced heterozygosity and how, in many cases, they maintain moderate levels of heterozygosity are still contentious issues 1 . The Fall armyworm (FAW; Lepidoptera: Spodoptera frugiperda), a polyphagous pest, is native to the Western hemisphere. Its invasion in the Old World was first reported from West Africa in early 2016, and in less than four years, it swept sub-Saharan Africa and Asia, finally reaching Australia. We used population genomics approaches to investigate the factors that may explain the invasive success of the FAW. Here we show that genomic balancing selection played a key role in invasive success by restoring heterozygosity before the global invasion. We observe a drastic loss of mitochondrial polymorphism in invasive populations, whereas nuclear heterozygosity exhibits a mild reduction. The population from Benin in West Africa has the lowest length of linkage disequilibrium amongst all invasive and native populations despite its reduced population size. This result indicates that balancing selection increased heterozygosity by facilitating the admixture of invasive populations from distinct origins and that, once heterozygosity was sufficiently high, FAW started spreading globally in the Old World. As comparable heterozygosity levels between invasive and native populations are commonly observed 1 , we postulate that the restoration of heterozygosity through balancing selection could be widespread among successful cases of biological invasions.

The fall armyworm (FAW; Spodoptera frugiperda) is one of the major agricultural pest insects. FAW is native to the Americas, and its invasion was first reported in West Africa in 2016. Then it quickly spread through Africa, Asia, and Oceania, becoming one of the main threats to corn production. We analyzed whole genome sequences of 177 FAW individuals from 12 locations on four continents to infer evolutionary processes of invasion. Principal component analysis from the TPI gene and whole genome sequences shows that invasive FAW populations originated from the corn strain. Ancestry coefficient and phylogenetic analyses from the nuclear genome indicate that invasive populations are derived from a single ancestry, distinct from native populations, while the mitochondrial phylogenetic tree supports the hypothesis of multiple introductions. Adaptive evolution specific to invasive populations was observed in detoxification, chemosensory, and digestion genes. We concluded that extant invasive FAW populations originated from the corn strain with potential contributions of adaptive evolution.

Since 2016, the fall armyworm (Spodoptera frugiperda, J.E. Smith) has spread from the Americas to invade many regions of the world, including Australia in early 2020. The development of effective pest management strategies for S. frugiperda is a high priority for crop protection. In the invasive range, the degree to which endemic biological control agents can constrain S. frugiperda remains sparsely investigated. This study examines 11 isolates of fungi including six Beauveria isolates and five Metarhizium isolates from Oceania for their potential as S. frugiperda biocontrol. Two Beauveria isolates (B-0571, B-1311) exhibited high virulence toward S. frugiperda caterpillars and adults. The overall mortalities over seven days in 3rd and 6th instar caterpillars and moths (respectively) for B-0571 was 82.81±5.75, 61.46±6.83, and 93.75±3.61, and for B-1311 was 73.72±2.51, 71.88±5.41, and 97.92±2.08%. The majority of deaths in the caterpillars occurred within the first 24 hours (3rd instar control 0.74±0.33%, B-0571 73.96±7.85 and B-1311 62.08±3.67%; 6th instar control 0%, B-0571 66.67±11.02% and B-1311 62.5±9.55%). Infection from both isolates fully prevented reproduction in surviving S. frugiperda females. The two isolates, however, cause a significantly lower mortality in a native noctuidae species: Helicoverpa armigera (3rd instar B-0571 44.79±4.54% and B-1311 19.80±7.51%). The discovery of two fungal isolates with high virulence to S. frugiperda caterpillars and adults opens new avenues for the development of biological control tools for this invasive moth pest. Such tools may also provide additional options for control of native pest lepidoptera, and reduce selection pressure for resistance to Bt and synthetic insecticides.

Since 2016, the fall armyworm (Spodoptera frugiperda, J.E. Smith) has spread from the Americas to invade many regions of the world, including Australia in early 2020. The development of effective pest management strategies for S. frugiperda is a high priority for crop protection. In the invasive range, the degree to which endemic biological control agents can constrain S. frugiperda remains sparsely investigated. This study examines 11 isolates of fungi including six Beauveria isolates and five Metarhizium isolates from Oceania for their potential as S. frugiperda biocontrol. Two Beauveria isolates (B-0571, B-1311) exhibited high virulence toward S. frugiperda caterpillars and adults. The overall mortalities over seven days in 3rd and 6th instar caterpillars and moths (respectively) for B-0571 was 82.81 ± 5.75, 61.46 ± 6.83, and 93.75 ± 3.61, and for B-1311 was 73.72 ± 2.51, 71.88 ± 5.41, and 97.92 ± 2.08%. The majority of deaths in the caterpillars occurred within the first 24 hours (3rd instar control 0.74 ± 0.33%, B-0571 73.96 ± 7.85 and B-1311 62.08 ± 3.67%; 6th instar control 0%, B-0571 66.67 ± 11.02% and B-1311 62.5 ± 9.55%). Infection from both isolates fully prevented reproduction in surviving S. frugiperda females. The two isolates, however, cause a significantly lower mortality in a native noctuidae species: Helicoverpa armigera (3rd instar B-0571 44.79 ± 4.54% and B-1311 19.80 ± 7.51%). The discovery of two fungal isolates with high virulence to S. frugiperda caterpillars and adults opens new avenues for the development of biological control tools for this invasive moth pest. Such tools may also provide additional options for control of native pest lepidoptera, and reduce selection pressure for resistance to Bt and synthetic insecticides.