The genome of shepard’s purse (Capsella bursa-pastoris) and the genetic basis of extreme cosmopolitanism
Authors: Daniel Koenig 1; Chris Fiscus 1; Christina Wesse 3; Max Collenberg 2; Barbara Neuffer 3; Detlef Weigel 2; Christa Lanz 2; Rebecca Schwab 2
Affiliations: 1) University of California Riverside; 2) Max Plank Institute for Biology Tübingen; 3) University of Osnabrück
Keywords: Comparative genomics & genome evolution
The allopolyploid Capsella bursa-pastoris is one of the world’s most successful plant species being found in abundance on six of seven continents across a wide diversity of environments. Shepard’s purse only recently spread to much of this distribution having been brought to the Americas and Australia by colonizers in the last few hundred years. In contrast, the diploid progenitors of C. bursa-pastoris reside in relatively constricted ranges in Eurasia. Here, we explore the birth and evolution of Capsella bursa-pastoris using several high quality genome assemblies from it and it’s diploid relatives. We that varied patterns of genome evolution in the diploid progenitors have continued to shape genomic diversity in the polyploid species and may predict the outcome of ongoing diploidization. Furthermore we characterize genomic and phenotypic diversity in hundreds of shepherds purse samples drawn from across the globe. We find that the wide range of climate environments occupied by this species is partly explained by strongly segregated ecotypic diversity. The two dominant ecotypes remain segregated across climates even after recent colonization of the Americas. However, hybrid zones found in intermediate climates facilitate mapping of adaptive loci. Our work links standing genetic variation to extremely rapid colonization of new habitats and advances C. bursa-pastoris as a model system for studying the contribution of molecular variation to climate adaptation.