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The evolutionary histories of many polyploid plant species are difficult to resolve due to a complex interplay of hybridization, incomplete lineage sorting, and missing diploid progenitors. In the case of octoploid strawberry with four subgenomes designated ABCD, the identities of the diploid progenitors for subgenomes C and D have been subject to much debate. By integrating new sequencing data from North American diploids with reticulate phylogeny and admixture analyses, we uncovered introgression from an extinct or unsampled species in the clade ofFragaria viridis,Fragaria nipponica, andFragaria nilgerrensisinto the donor of subgenome A of octoploidFragariaprior to its divergence fromF. vescasubsp. bracteata. We also detected an introgression event fromF. iinumaeinto an ancestor ofF. nipponicaandF. nilgerrensis.Using an LTR-age-distribution-based approach, we estimate that the octoploid and its intermediate hexaploid and tetraploid ancestors emerged approximately 0.8, 2, and 3 million years ago, respectively. These results provide an explanation for previous reports ofF. viridisandF. nipponicaas donors of the C and D subgenomes and suggest a greater role than previously thought for homoploid hybridization in the diploid progenitors of octoploid strawberry. The integrated set of approaches used here can help advance polyploid genome analysis in other species where hybridization and incomplete lineage sorting obscure evolutionary relationships.
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This content will become publicly available on May 1, 2026
Were bed bugs the first urban pest insect? Genome-wide patterns of bed bug demography mirror global human expansion
There are calls for research into the historical evolutionary relationships between humans and their commensals, as it would greatly inform models that predict the spread of pests and diseases under urban population expansion. The earliest civilizations emerged approximately 10 000 years ago and created conditions ideal for the establishment and spread of commensal urban pests. Commensal relations between humans and pests likely emerged with these early civilizations; however, for most species (e.g. German cockroach and black rat), these relationships have formed relatively recently—within the last 5000 years—raising the question of whether others could have emerged earlier. Following comparative whole genome analysis of bed bugs,Cimex lectularius, belonging to two genetically distinct lineages, one associated with bats and the other with humans, coupled with demographic modelling, our findings suggests that while their association with humans dates back potentially hundreds of thousands of years, a dramatic change in the effective population size of the human-associated lineage occurred approximately 13 000 years ago; a pattern not found in the bat-associated lineage. The timing and magnitude of the demographic patterns provide compelling evidence that the human-associated lineage closely tracked the demographic history of modern humans and their movement into the first cities. As such, bed bugs may represent the firsttrueurban pest insect species.
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- Award ID(s):
- 2307044
- PAR ID:
- 10608216
- Publisher / Repository:
- Royal Society
- Date Published:
- Journal Name:
- Biology Letters
- Volume:
- 21
- Issue:
- 5
- ISSN:
- 1744-957X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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