POPULATION STRUCTURE VARIATION EXPLAINS THE NICHE DIVERGENCE IN DIPLOID-TETRAPLOID POLYPLOID COMPLEX PASPALUM INTERMEDIUM

SCHEDLER, MARA; HOJSGAARD, DIEGO; KARUNARATHNE, PIYAL; MARTINEZ E.J.; ANA I. HONFI

FOZ DO IGUAZU

Congreso; 2018 INTERNATIONAL CONGRESS OF GENETICS; 2018

INTERNATIONAL FEDERATION OF GENETICS, SOCIEDADE BRASILERA DE GENETICA, ASOCIACION LATINOAMERICANA DE GENETICA

Intraspecific ploidy variation and divergent reproductive systems are of greater importance to understand the distribution of genetic variation and the evolutionary dynamics of polyploid complexes. We used the South American grass species Paspalum intermedium as a model plant to study the ecological differentiation and genetic variation in a diploid (2x) - tetraploid (4x) polyploid complex. Plant populations from over 70 localities were examined using Flow cytometry method for ploidy determination, of which 35 populations were analyzed using AFLP markers for inter- and intra-population genetic variation. Ecological Differentiation was assessed using environmental data. Both cytotypes show pronounced ecological differentiation along a latitudinalgradient, including a contact zone of 2x-4x populations, with mixed-ploidy populations. The genetic variation among populations resolved three major clusters. One cluster containing most 4x populations, a second cluster mainly consisting of all the 2x populations, and a third cluster made up of three isolated 4x populations. Mixed ploidy populations were genetically closely related to 2x than to 4x cytotypes and clustered with 2x. Furthermore, higher genotypic diversitywas observed among and within 2x populations in comparison to 4x populations which were mainly composed of both single and multiple genotypes. Reproductive isolation and facultative apomixis may explain the lack of genotypic variability in tetraploid populations. Populationstructure analyses point to multiple independent origins of 4x cytotype although the majority is of single origin. This observation explains indicative cytotype displacement by both cytotypes owning to divergent ecological specialization and niche differentiation between cytotypes.