Geographical parthenogenesis, cytotype distribution patterns and ecological variation in the subtropical grass Paspalum intermedium Munro ex Morong

SCHEDLER, MARA; HOJSGAARD, DIEGO H.; KARUNARATHNE, PIYAL; HONFI, ANA I.; MARTÍNEZ, ERIC J.

Montevideo

Congreso; XVI Congreso Latinoamericano de Genética. IV Congreso de la Sociedad Uruguaya de Genética. XLIX Reunión Anual de la Sociedad de Genética de Chile. XLV Congreso Argentino de Genética; 2016

Sociedad Latinoamericana de Genética

Although, it has been neglected by biologists for long, polyploidization is now known to have a major role in evolution of vascular plants. Spatial distribution patterns of cytotypes shed light on dynamics of polyploid complexes (establishment, maintenance and evolution). Unlike in temperate regions, there are only a handful of studies on these phenomena done in tropical and subtropical areas in southern hemisphere where speciation may be totally unrelated to historic glaciation.Paspalum L. is a New World grass genus with many polyploid species. In the present study, we focus on cytotype distribution patterns and ecological differentiation in subtropical grass species P. intermedium. Over 1000 plant samples were cytotyped from populations occurring in the Northeast of Argentina, the core distribution area of the species and past and present environmental data were used to assess ecological differentiation. Two major cytotypes were identified: diploid and tetraploid. The tetraploid cytotype shows a slightly larger range of distribution compared to that of the diploid, with both cytotypes overlapping along a wide contact zone. Ecological assessment on macro-scale does show significant relation to photosynthetically active radiation suggestive of tetraploid adaptation to less productive environments and micro-scale or rather local establishment. We assumed that the two cytotypes evolved as a result of niche shift facilitated by reproductive isolation irrelevant of past glaciation. A population genetic assessment will reveal more details about the evolution of these populations.