Cytotype distribution and genetic structure in a diploid x tetraploid contact zone of the Turnera sidoides (Passifloraceae, Turneroideae) polyploid complex

IVANA EVELIN KOVALSKY; VIVIANA GRISELDA SOLÍS NEFFA; ESTEBAN NADAL PAREDES; SILVIA ANDREA FERNÁNDEZ

Foz de Iguazú

Congreso; 2018 International Congress of Genetics; 2018

Turnera sidoides L. (x= 7) complex constitutes a suitable biological model system to study the evolutionary dynamics of polyploids in natural populations. Diploids and tetraploids of this complex overlap in Corrientes (Argentina). In order to investigate the evolutionary forces governing the establishment of polyploids and their coexistence with diploids, we analyzed the frequencies of diploids, triploids and tetraploids in the area of overlapping as well as the coincidence of genetic structure with cytotype distributions. Ploidy was inferred from estimates of DNA content by flow cytometry, while genetic structure for all cytotypes was assessed using amplified fragment length polymorphisms (AFLPs). We made intra- and intercytotype site comparisons to determine numbers of pairwise differences and calculate FST values. We also performed AMOVA to assess partitioning of genetic variance among populations and cytotypes.Diploids and tetraploids were the most abundant whereas triploids were the least abundant. Most populations were constituted by a single cytotype and were either diploid or tetraploid but never triploid. Cytotypes were spatially segregated, occupying different topographic positions, being diploids most frequent in the Miriñay riverside. At a microsite scale, diploid and triploid individuals coexist alongside male and/or female unreduced gametes producers. Also, some mixed diploidtriploid-tetraploid populations were found. AFLP data revealed significant genetic differentiation between diploids and tetraploids, but modest genetic differentiation between triploids and tetraploids. AMOVA indicated that most of the variation occurred within populations. Genetic structure coincided with cytotype distributions. The contribution of genetic variation and frequencydependent mating success to the cytotype distribution is discussed.Keywords: polyploidy, contact zone, cytotype distribution, Genetic structure