Abstract
Festuca indigesta subsp. indigesta (Poaceae) is endemic to the southeast of Spain, and until recently, it was considered that its range of distribution was restricted to the siliceous core of Sierra Nevada. However, it has been recently extended in the territory to others calcareous mountains. This study investigates the cytogenetic variability throughout the geographic range of this taxon, the possible edaphic preferences of each cytotype, and the morphological variation of cytotypes. Genome sizes and ploidy levels were estimated using flow cytometry and chromosome count. Soil samples were collected to test the nature of the substrate, i.e., pH, and calcium and magnesium contents. Finally, morphological characters were measured in herbarium specimens. This study provides the first genome size data for the species. Hidden cytogenetic diversity was detected in the taxon, comprising hexaploid (2n = 6x = 42), octoploid (2n = 8x = 56) and dodecaploid (2n = 12x = 84) individuals. No relationship between substrate nature and cytotype was observed. Morphological differences were detected for the size of floral parts and stomata among cytotypes, but these were blurred if the entire morphological variation range was considered. Our results suggest that each mountain range could act as a reservoir of morphologically cryptic genetic diversity regarding this taxon.
Highlights
It was confirmed by chromosome counts that these genome size estimations corresponded to three ploidy levels (Figure 3): hexaploid (2n = 6x = 42 chromosomes; Peñones de San Francisco and Collado de Las Sabinas populations), octoploid (2n = 8x = 56; Puerto de la Ragua and Sierra de Gádor populations), and dodecaploid (2n = 12x = 84; Sierra de las Nieves population)
The 2C values were positively correlated with the chromosome numbers detected (Pearson r = 0.989, p < 0.0001; Spearman r = 0.920, p < 0.0001)
All populations were single-ploidy: no numerical variation in chromosome numbers was found, and there was no significant variation in genome size estimates
Summary
It has been suggested that the Western Mediterranean region was one of the secondary centers of diversification of Festuca during Pleistocene glacial periods, and one of the main driving forces behind its diversification has been postulated as being polyploidization events [1]. The genus includes many polyploid species (about 70%) and comprises a large variation in cytotypes, ranging from 2n = 2x = 14 to 2n = 14x = 98; the latter being recently detected in plants from the Iberian Peninsula [2]. In the Iberian territory, a great taxonomic diversity of the genus is concentrated in the Baetic Range (southeast of Spain), which harbors several endemic fescues, some with a narrow distribution area and others that are present in North Africa (Baetic-North African species). The orographic diversity of the Baetic Cordillera allowed the Festuca species and the taxa of many other genera to find suitable niches. Climatic history and ecology are considered the most important factors in shaping the spatial pattern of genetic diversity
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