Abstract
The study of genome size variation can contribute valuable information on species relationships as well as correlate to several morphological or ecological features, among others. Here we provide an extensive report on genome sizes on genus Tripleurospermum and its closely related genus Matricaria, which are two typically Mediterranean genera particularly widespread and diverse in Turkey, the origin of most of the populations here studied. We analyse and discuss genome size variation in the first relatively complete molecular phylogenetic framework of Tripleurospermum (based on ITS and ETS ribosomal DNA–rDNA–regions). We find cases of intraspecific genome size variation, which could be taxonomically significant. Genome downsizing is also detected as the typical response to polyploidisation in Tripleurospermum taxa, being most conspicuous at the tetraploid level. Several positive correlations with genome size, including those with pollen and stomatal size or cypsela length, among others, are also found. Remarkably, taxa presenting rhizomes tend to present higher genome sizes, confirming a trend to accumulate nuclear DNA in such species, which could be explained by the nutrient reserves availability in their storage organs, allowing genome expansion, or by the lower rates of sexual reproduction in rhizomatous taxa.
Highlights
Tripleurospermum Sch.Bip. is a genus of family Asteraceae, tribe Anthemideae, comprising between 30 to 40 species, depending on the authors and systematic treatments
The main purpose of this study is to address genome size variation in the two closely related genera Tripleurospermum and Matricaria, increasing the sample to embrace most of the species of both genera, for many of which we will provide first estimates
We have included the species Anthemis macrotis (Rech.f.) Oberpr. & Vogt in the analysis since (i) it was relevant as a genus closely related to both genera and had been previously considered a member of Matricaria (M. macrotis Rech.f.), a more recent taxonomic study based on molecular markers best placed it as a member of Anthemis [9], and (ii) no previous genome size estimate was available for the species
Summary
Tripleurospermum Sch.Bip. is a genus of family Asteraceae, tribe Anthemideae, comprising between 30 to 40 species, depending on the authors and systematic treatments. Distributed in the Northern hemisphere, mainly in the Mediterranean basin including Europe, temperate Asia and North Africa [1, 2, 3], some taxa are present in North America. It is abundant and diverse in Turkey, its main center of diversity, where around 30 Tripleurospermum taxa can be found half of which endemic [4]. T. inodorum (L.) Sch. Bip., is widespread as a weed [1].
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