Karyotype variability in species of the genus Zephyranthes Herb. (Amaryllidaceae–Hippeastreae)

Abstract

In this work, the cytotaxonomic implications of the chromosomal characterization of cultivated and native Zephyranthes species described in northeastern Brazil were studied. All individuals had karyotype formed by a set of metacentric chromosomes, in addition to submetacentric and acrocentric chromosomes. In Zephyranthes robusta, 2n = 12 was observed and karyotype with formula 4M ? 2SM in somatic cells, representing the most symmetric karyotype among the investigated species. Z. sylvatica showed three different chromosome complement numbers: 2n = 12 with formula 1M ? 5SM, 2n = 12 ? 1B with 1M ? 5SM ? (1B), and 2n = 18 formed by cracks. The cultivated species Z. rosea Lindl. presented 2n = 24 with 4M ? 7SM ? 1A, however Z. grandiflora Lindl. showed the same chromosome number with 2M ? 5SM ? 5A. Zephyranthes aff. rosea Lindl. presented 2n = 25 with one small metacentric forming a crack in the fourth metacentric pair. Z. brachyandra has 2n = 24 ? (1B) and formula 4M ? 3SM ? 5A ? (1B). Z. candida Herb. presented 2n = 38 and karyotype formula 9M ? 10SM. In Habranthus itaobinus numerical variation was observed, with the majority of populations showing a chromosome complement composed of 2n = 44 ? 1B with 5M ? 12SM ? 5A ? (1B), or 2n = 44 ? 3B in a single population. Mechanisms involved in the formation of these karyotypes from chromosomal imbalance data are discussed. Taken together, data from this study only partially confirm previous counts for epithets and further enhance the cytological variability data previously reported for the genus.

Chromosome number variation and evolution in Neotropical Leguminoseae (Mimosoideae) from northeastern Brazil

“…Some taxonomic groups, such as orchids of the genera Oncidium and Epidendrum Guerra, 2000, 2010), and Hoffmannseggella (Yamagishi-Costa and Forni-Martins, 2009) have a strong tendency to form polyploids in environments that experience extreme conditions of abiotic stress. Other taxonomic groups, however, such as the families Convolvulaceae (Pitrez et al, 2008) and Amaryllidaceae (Felix et al, 2011), show no apparent correlation between polyploidy and environmental stress. The evolution of plant groups by the duplication of their genomes is generally rarer in tropical regions than in temperate zones, where environmental fluctuations are more frequent and are conducive to the formation of non-reduced gametes (Leitch and Bennett, 1997).…”

Karyological Investigation on Three <i>Zephyranthes</i> Species and Its Taxonomic Significance

“…In this study, 2n=4x=24 in Z. carinata (tetraploid) and 2n=8x= 48 in Z. tubispatha (octaploid) represents the base number x= 6 that supports the previous findings. However, 2n=38 in Z. candida could occur as hexaploid (2n=6x=36) followed by secondary modification (hyper-aneuploidy), similarly reported by Felix et al (2011b). Because of the most frequent occurrence, it is to be expected that variation in base number might be originated from the normal ancestor having x= 6.…”

“…x=5, 7, 9, 11, 13, and15 (Naranjo 1969, Daviña andFernández 1989), however, those numbers were found to exist in very few cases. Felix et al (2011b) reported Z. robusta and Z. sylvatica as diploid, Z. rosea, Z. brachyandra and Z. grandiflora (=Z. carinata) as tetraploid considering x= 6.…”

The contribution of cytogenetics and flow cytometry for understanding the karyotype evolution in three Dorstenia (Linnaeus, 1753) species (Moraceae)

“…The polyploid origin of plant species has been shown by classical cytogenetics, such as for the genera Psidium Linnaeus, 1753 ( Souza et al 2015 ), Claytonia Linnaeus, 1753 ( McIntyre 2012 ) and Cardamine Linnaeus, 1753 ( Marhold et al 2010 ). From the assembly of accurate karyograms using chromosomes with different levels of chromatin compaction, the type of polyploidy was also evidenced, with autopolyploidy being found in Glycine max (Linnaeus, 1753) Merrill, 1917 ( Clarindo et al 2007 ) and Zephyranthes Herbert, 1821 ( Felix et al 2011 ), and allopolyploidy in Paullinia cupana Kunth, 1821 ( Freitas et al 2007 ) and Triticum aestivum Linnaeus, 1753 ( Kamel 2006 ). Polyploidy has played a key role in plant evolution, with estimates maintaining euploidy in the ascendancy of all angiosperms ( Abbott et al 2013 , Soltis et al 2014 ).…”