Biology subjects

Olofsson, J. K.

Publications and source records attributed to Olofsson, J. K..

2 recordsLinked to original sources

bioRxiv2021

Hybridisation boosts dispersal of two contrasted ecotypes in a grass species

O_LIIn the absence of strong reproductive barriers, genetic exchanges between closely related groups of organisms with different adaptations have well-documented beneficial and detrimental consequences. In plants, pollen-mediated exchanges affect the sorting of alleles across physical landscapes, and influence rates of hybridisation. How these dynamics affect the emergence and spread of novel ecological strategies remains only partially understood. C_LIO_LIWe use phylogenomics and population genomics to retrace the origin of two geographically overlapping ecotypes of the African grass Alloteropsis angusta. C_LIO_LIWe report the existence of a previously undescribed ecotype inhabiting miombo woodlands and grasslands. The two ecotypes have divergent nuclear genomes. However, the seed-transported chloroplast genomes are consistently shared by distinct ecotypes inhabiting the same region. These patterns suggest that the nuclear genome of one ecotype can reach the seeds of the other via pollen movements, with strong selection subsequently sorting nuclear alleles by habitat. C_LIO_LIThe contrasting ecotypes of A. angusta can use each other as a gateway to new locations across a large part of Africa. Coupled with newly discovered hybridisation with the sister species A. semialata, our results show that hybridisation can facilitate the geographical dispersal of distinct ecotypes of the same grass species. C_LI

evolutionary biology↗

bioRxiv2020

Physiological diversity enhanced by recurrent divergence and secondary gene flow within a grass species

O_LIC4 photosynthesis evolved multiple times independently in angiosperms, but most origins are relatively old so that the early events linked to photosynthetic diversification are blurred. The grass Alloteropsis semialata is an exception, as this single species encompasses C4 and non-C4 populations. C_LIO_LIUsing phylogenomics and population genomics, we infer the history of dispersal and secondary exchanges before, during, and after photosynthetic divergence in A. semialata. We further establish the genetic origins of polyploids in this species. C_LIO_LIOrganelle phylogenies indicate limited seed dispersal within the Central Zambezian region of Africa, where the species originated [~] 2-3 Ma. Outside this region, the species spread rapidly across the paleotropics to Australia. Comparison of nuclear and organelle phylogenies and analyses of whole genomes reveal extensive secondary gene flow. In particular, the genomic group corresponding to the C4 trait was swept into seeds from distinct geographic regions. Multiple segmental allopolyploidy events mediated additional secondary genetic exchanges between photosynthetic types. C_LIO_LILimited dispersal and isolation allowed lineage divergence, while episodic secondary exchanges led to the pollen-mediated, rapid spread of the derived C4 physiology. Overall, our study suggests that local adaptation followed by recurrent secondary gene flow promoted physiological diversification in this grass species. C_LI

evolutionary biology↗