Species diversification in the lowlands of mid-latitude South America: Turnera sidoides subsp. carnea as a case study

Abstract

The lowlands of mid-latitude South America comprise complex temperate ecoregions characterized by a unique biodiversity. However, the processes responsible for shaping its species diversity are still largely unknown. Turnera sidoides subsp. carnea is a variable subspecies occurring in the lowlands of northeastern Argentina and Uruguay, extending to southern Paraguay and Brazil. It constitutes a good model to perform evolutionary studies. Here we used an integrative approach to understand the process of diversifi cation within this subspecies and to increase the knowledge concerning patterns and processes responsible for shaping the species diversity in the temperate lowlands of South America. The results provided strong evidences that this subspecies is an autopolyploid complex per se, being in an active process of intrasubspecifi c diversifi cation. Morphological and genetic data show that the diversity of T. sidoides subsp. carnea is in congruence with the great past and present abiotic and biotic variability of the mid-latitude South American lowlands. The evolutionary history of this subspecies is consistent with past fragmentation and allopatric differentiation at diploid level. Geographic isolation and local adaptation would have promoted strong morphological, ecological, and genetic differentiation, resulting in two morphotypes and different genetic groups indicative of incipient speciation.

Chromosomic Studies in Zephyranthes Citrina Baker (Amaryllidaceae), a Polyploid Ornamental

“…In addition to the morphological variability, polyploidy is the most outstanding feature of T. sidoides complex, with ploidy levels ranging from diploid (2n=2x=14) to octoploid (2n=8x=56), all based on x=7. Polyploid series within each subspecies/morphotype were reported (Fernández, 1987;Solís Neffa, 2000;Solís Neffa and Fernández, 2001;Solís Neffa et al, 2004;Speranza et al, 2007;Elías et al, 2011;Moreno et al, , 2021Solís Neffa et al, 2022). From the study of meiosis (Figure 2) and pollen viability it was suggested that polyploids of T. sidoides would have an autopolyploid origin (Fernández, 1987;Solís Neffa, 2000).…”

“…Besides, populations of T. sidoides subsp. carnea were grouped into two morphotypes (grandense and mercedeño) according to the leaf consistency, the colour of the flowers and geographical distribution (Moreno et al, 2021); while in T. sidoides subsp. pinnatifida five morphotypes (andino, chaqueño, mesopotamico, pampeano and serrano) have been distinguished based on the degree of incision of the leaf blade, the colour of the flowers and geographical distribution (Solís Neffa, 2010).…”