Population genomics reveals patterns of divergence and gene flow between population of Fusarium subglutinans and Fusrium temperatum in Argentina

FUMERO M V; YUE W; CHIOTTA M. L; CHULZE , S.N; LESLIE J.F.; TOOMAJIAN C

Pacific Grove

Congreso; 30 th Fungal Genetic Conference; 2019

Genetic Society of America

Recent studies have made it clear that species boundaries between fungi can be semipermeable,and call into question the utility of a bifurcating species tree as a model. More data are needed onhow this semipermeability affects the speciation process and what this it implies for adaptiveevolution, especially in pathogenic species. Fusarium subglutinans and F. temperatum represent closely-related maize pathogens only recently distinguished in the literature based on molecular phylogenies, but which, and but which, in some cases, canpable of cross sexuallying in the laboratory.We collected genome-wide polymorphism data from a sample of both species and used in genotyping-by-sequencing to explore patterns of genetic divergence between the two. Our analysis supports the separation of these two entities as distinct species, with multiple methods consistently placing individuals into species groups, and no individuals identified as clear hybrids. Demographic modeling to fit the joint allele frequency spectrum supported a model withgene flow between species subsequent to their split. It also indicated that this gene flow has been biased from F. subglutinans into F. temperatum. Our data were characterized by high levels of both fixed differences and shared polymorphisms between species; however, we could not pinpoint discrete regions that were critical in speciation. Demographic modeling to fit the joint allele frequency spectrum supported a model with gene flow between species subsequent to their split. It also indicated that this gene flow has been biased into F. temperatum. By investigating the genome-wide distribution of the fixed differences and shared polymorphisms between these species, we cannot pinpoint discrete regions that may have been critical in speciation. However, we find an enrichment of s Shared  polymorphisms between species were enriched at the chromosome ends;  This pattern that raises interesting questions about the interaction between natural selection and gene flow during the divergence of these species. Comparing  the genetic diversity and evidence for population structure within each species, we found there is  more evidence for genetic structure within F. temperatum than within F. subglutinans. This species was also was found at higher elevation and was in associated association with more ancient maize varieties, potentially indicating less adaptation to modern agricultural practices.