Abstract
The genus Marshallia is made up by seven to ten species of perennial herbs growing mainly in open habitats, whereas the genus Balduina is represented by three sympatric species; two perennial herbs and one annual, growing in open pine forest habitats. Both genera belong to the family Asteraceae, tribe Helenieae, and are endemic to the southeast United States, in North America. Cytogenetic studies concerning these two genera are scarce and genome size data is lacking for both. The main goals of this study were to (i) generate novel insights into the evolution of the genome size and (ii), contribute to filling existing gaps on our knowledge of the Asteraceae family from this point of view. Nuclear DNA contents range from 11.42 pg/2C in Marshallia trinervia to 31.58 pg/2C in Marshallia mohrii. The combination of genome size with chromosome data (and inferred cytotypes) suggests the existence of multiple cytotypes, and provides interesting insights into the potential impact of polyploidy in the evolution of these genera in general, and the shaping of genome size diversity, in particular.
Highlights
The genus Marshallia Schreb. (Asteraceae: Helenieae), commonly known as Barbara’s buttons, is endemic to the southeast United States of America (Hansen and Goertzen 2014)
Some of its morphological features are shared with other groups of Asteraceae (Baldwin 2009). This author placed the genus within subtribe Marshalliinae, closely related to Gaillardiinae in the tribe Helenieae, but its sister group has not yet been clearly established (Baldwin and Wessa 2000)
Species of Marshallia can be difficult to distinguish from each other based on morphological characters, a more recent study carried out by Hansen and Goertzen (2014) revealed that nuclear ribosomal ITS sequences serve as an acceptable DNA barcode marker in the genus, with sufficient nucleotide differences to discriminate amongst most species
Summary
The genus Marshallia Schreb. (Asteraceae: Helenieae), commonly known as Barbara’s buttons, is endemic to the southeast United States of America (Hansen and Goertzen 2014). (Asteraceae: Helenieae), commonly known as Barbara’s buttons, is endemic to the southeast United States of America (Hansen and Goertzen 2014). This small genus is made up of seven (Baldwin 2009; Watson 2006) to ten species (Weakley 2020) of perennial herbs, which grow mainly in open habitats such as pine forests and roadsides, some species show preference for wet habitats as bogs, shoals or stream sides. Species of Marshallia can be difficult to distinguish from each other based on morphological characters, a more recent study carried out by Hansen and Goertzen (2014) revealed that nuclear ribosomal ITS sequences serve as an acceptable DNA barcode marker in the genus, with sufficient nucleotide differences to discriminate amongst most species
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