Abstract
The interest to study genome evolution, in particular genome size variation and polyploid incidence, has increased in recent years. Still, only a few studies have been focused at a community level. Of particular interest are high mountain species, because of the high frequency of narrow endemics and their higher susceptibility to extinction due to the effects of climate change. In the present study we explored genome size variation and polyploidy incidence in the entomophilous plant communities of two distinct mountain ranges, the Sierra Nevada and Picos de Europa National Parks. For that, chromosome numbers and DNA ploidies were assessed through a review of the literature, and the genome size and incidence of polyploidy in 39 taxa from several key genera were estimated using flow cytometry. In this study, first genome size estimations are given for 32 taxa. The majority of the analyzed taxa presented very small to small genome sizes (2C ≤ 7.0 pg), with no differences being detected between genome size and geographic origin and distribution ranges. A low incidence of polyploid taxa was observed (23.3%), with polyploids being more common in Picos de Europa than in Sierra Nevada. Most taxa inferred as polyploids were high altitude plants, but no clear pattern between polyploidy incidence and endemic status was observed. The obtained results are discussed within the context of angiosperm’s genome size variation and of polyploidy incidence in alpine and arctic flora, contributing to the scientific knowledge of these natural communities of great biological importance.
Highlights
The study of the genome size and its variation has been increasingly important in many areas of plant research, including taxonomy, biosystematics, ecology and population biology
As part of an ongoing project focused on the study of pollination interactions in high mountain plants (Santamaría & al., 2011a, b), in the present study we explored genome size variation and polyploidy incidence on two distinct mountain ranges in Spain, placed in the Mediterranean region and in its transition with the Euro-Siberian region, the Sierra Nevada and Picos de Europa National Parks, respectively
For Picos de Europa community, we considered as narrow endemics those plants that were distributed in both Picos de Europa and Pyrenees, such as Minuartia villarsii, and Saxifraga hirsuta subsp. paucicrenata
Summary
The study of the genome size and its variation has been increasingly important in many areas of plant research, including taxonomy, biosystematics, ecology and population biology. Genome contraction has been associated with deletional mechanisms, such as, unequal intra-strand homologous recombination, illegitimate recombination and/or higher rate of nucleotide deletion over insertion (Swigonova & al., 2005) Another important mechanism responsible for rapid increases in genome size is polyploidy. It is generally considered that polyploids are more frequent at higher latitude or altitude than related diploids (Petit & Thompson, 1999) This pattern is based on two hypotheses: first, polyploids might be more successful than diploids in colonizing after glaciation (Brochmann & al., 2004); second the last glacial maximum climate enforced range shifts that might have led to the formation of hybrids of formerly allopatric taxa, which subsequently suffered chromosome doubling to restore fertility [secondary contact hypothesis of Stebbins (1984)]. Considering that polyploid individuals may have higher colonization success after glacial periods than their diploid progenitors (Brochmann & al., 2004), we expect that the high mountain communities studied will show a high frequency of polyploids
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