A universe of dwarfs and giants: genome size and chromosome evolution in the monocot family<scp>M</scp>elanthiaceae

Chromosome number changes during the evolution of angiosperms are likely to have played a major role in speciation. Their study is of utmost importance, especially now, as a probabilistic model is available to study chromosome evolution within a phylogenetic framework. In the present study, likelihood models of chromosome number evolution were fitted to the largest family of flowering plants, the Asteraceae. Specifically, a phylogenetic supertree of this family was used to reconstruct the ancestral chromosome number and infer genomic events. Our approach inferred that the ancestral chromosome number of the family is n = 9. Also, according to the model that best explained our data, the evolution of haploid chromosome numbers in Asteraceae was a very dynamic process, with genome duplications and descending dysploidy being the most frequent genomic events in the evolution of this family. This model inferred more than one hundred whole genome duplication events; however, it did not find evidence for a paleopolyploidization at the base of this family, which has previously been hypothesized on the basis of sequence data from a limited number of species. The obtained results and potential causes of these discrepancies are discussed.

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“…2013: Thalictrum , Ranunculaceae; Chacón et al. 2014: Colchicaceae; Pellicer et al. 2014: Melanthiaceae; Sousa et al.…”

Section: Introductionunclassified

The Evolution of Haploid Chromosome Numbers in the Sunflower Family

2016

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“…The changes to the nuclear DNA content have also been attributed to structural rearrangements and/or heterochromatin polymorphisms (Pellicer et al 2014, Amaral-Silva et al 2016). …”

Section: Discussionmentioning

confidence: 99%

First karyotype description and nuclear 2C value for Myrsine (Primulaceae): comparing three species

Carvalho¹,

Amaral-Silva²,

Spadeto³

et al. 2017

CCG

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Cytogenetic studies in Primulaceae are mostly available for herbaceous species, and are focused on the chromosome number determination. An accurate karyotype characterization represents a starting point to know the morphometry and class of the chromosomes. Comparison among species within Myrsine, associating these data with the nuclear 2C value, can show changes that led the karyotype evolution. Here, we studied three Myrsine species [Myrsine coriacea (Swartz, 1788) Brown ex Roemer et Schultes, 1819, Myrsine umbellata Martius, 1841 and Myrsine parvifolia Candolle, 1841] that show different abilities to occupy the varied types of vegetation within the Brazilian Atlantic Forest. Cytogenetic characterization showed some individuals with 2n = 45 chromosomes for Myrsine parvifolia and Myrsine coriacea, with most individuals of the three species having 2n = 46. The first karyograms for Myrsine were assembled and presented morphologically identical and distinct chromosome pairs. In addition, differences in the mean 2C nuclear value and chromosome morphometry were found. Therefore, the first description of the Myrsine karyotype has been presented, as well as the nuclear 2C value. The procedures can be applied to other Myrsine species for future investigations in order to better understand its effects on the differential spatial occupation abilities shown by the species in Brazilian Atlantic Forest.

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“…Our chromosome number has been included in a recent reconstruction of ancestral chromosome numbers for major clades within Melanthiaceae (Pellicer et al 2014). Bayesian and maximum likelihood analyses with ChromEvol v. 1.3 (Mayrose et al 2010) support nine as the likely base (haploid) chromosome number for tribe Melanthieae, and eight for the sister-clade to Zigadenus glaberrimus, which includes the remaining genera in the tribe.…”

Section: Resultsmentioning

confidence: 99%