Phylogenetic relations in tribe Leucocoryneae (Amaryllidaceae, Allioideae) and the validation ofZoellneralliumbased on DNA sequences and cytomolecular data

Abstract

Tribe Leucocoryneae comprises the genera Beauverdia, Ipheion, Leucocoryne, Nothoscordum, Tristagma and Zoellnerallium, a more recently described genus, the validity and relationships with the other genera of the tribe of which are still unclear. The present work aims to characterize the karyotype of Zoellnerallium and to evaluate the phylogenetic relationships among the genera of Leucocoryneae. The phylogeny of the tribe was reconstructed based on trnG intron plastid and internal transcribed spacer nr(ITS) nuclear sequences. Karyotype description of the two Zoellnerallium spp. was based on chromosome morphometry, DAPI and CMA fluorochrome staining, rDNA sites and silver nitrate staining. Phylogenetic analyses indicated that all genera of Leucocoryneae, except Beauverdia (included in Nothoscordum), are monophyletic. Nothoscordum spp. appeared as sister to a major clade of Leucocoryneae (Ipheion + Tristagma and Leucocoryne + Zoellnerallium). The two Zoellnerallium spp. had 2n = 24 (8M + 16A). The occurrence of two pairs of 5S rDNA sites in Zoellnerallium and tetraploids of Nothoscordum spp. further supports the tetraploid nature of this genus. The higher diploid number of Zoellnerallium was due to centric fissions followed by the emergence of a 45S rDNA cluster on the short arm of the new acrocentric chromosomes. The data suggest that Zoellnerallium spp. are tetraploids with a basic number x = 12 (4M + 8A), whereas the ancestor diploid karyotype with n = 3M + 2A is currently present only in Nothoscordum and Leucocoryne. Different combinations of karyotypic changes may have led to the isolation of lineages and formation of most genera in Leucocoryneae.

Divide to Conquer: Evolutionary History of Allioideae Tribes (Amaryllidaceae) Is Linked to Distinct Trends of Karyotype Evolution

“…The maintenance of the number of chromosome arms accompanied by chromosomal number (2n) changes in Chilean Gilliesieae species analyzed here clearly indicates a karyotype evolution by Robertsonian translocations Escobar, 2012). This type of chromosomal rearrangement was also observed other genera of Gilliesieae (Crosa, 1972;Jones, 1998;Souza et al, 2010Souza et al, , 2012Souza et al, , 2015Souza et al, , 2016Souza et al, , 2019b, however, it is rarely reported in species of Allieae or Tulbaghieae (Vosa, 2000;Peruzzi et al, 2017). Interestingly, our data also suggests that chromosome number evolution is more associated with phylogenetic relatedness in Gilliesieae than in the other tribes ( Supplementary Table S1), which reinforces the impact of chromosome number change for the evolution of this tribe.…”

“…& Endl., Miersia chilensis Lindl., Solaria miersioides Phil., and Speea humilis Loes. In addition, new genome size estimates were undertaken for genera Ipheion Raf., Leucocoryne Lindl., Nothoscordum Kunth, and Zoellnerallium Crosa [vouchers and collection locations presented in Souza et al (2010Souza et al ( , 2016]. Collection locations, voucher numbers and karyotype data are presented in Table 1.…”

“…The subfamily Allioideae of Amaryllidaceae (sensu Angiosperm Phylogeny Group [APG], 2016) is an excellent model to assess the links between karyotypes and environmental variables by presenting large chromosomes with remarkable cytogenetic variability (Vosa, 2000;Souza et al, 2016;Pellicer et al, 2017;Peruzzi et al, 2017;Sassone et al, 2018), associated with an intriguing discontinuous geographical distribution (Figure 1). Allioideae is phylogenetically composed of three tribes (Angiosperm Phylogeny Group [APG], 2016): Allieae, Gilliesieae, and Tulbaghieae, which are exclusively distributed in North Hemisphere, South America (Peru to Chile), and Southern Africa, respectively (Figure 1).…”

“…Conversely, the South American Gilliesieae present the highest karyotype variability in Allioideae: it is represented by both different basic chromosome numbers (x = 4, 5, 6, 7, and 10) and chromosome numbers (2n = 8, 10, 12, 14, 15, 16, 18, 19, 20, 24, 26, and 32) resulted from intense Robertsonian translocation and polyploidy events (Escobar, 2012;Souza et al, 2016;Pellicer et al, 2017;Sassone et al, 2018). In addition, analyses of heterochromatic bands and distribution of 5S/35S rDNA sites by fluorescence in situ hybridization (FISH) have revealed extensive cytomolecular variability in the subfamily (Souza et al, 2016(Souza et al, , 2019b. The different patterns of karyotype evolution and speciesrichness (i.e., high karyotype variation in low diversified lineages or stable karyotypes in high diversified groups) of Allioideae tribes (Figure 1) represent an interesting case study for the implications of intercontinental disjunction.…”

Towards stable classifications

“…Bone, Cribb & Buerki, ; Chase et al ., ). Finally, in this issue, we present papers on fungi and lichens (Auxier et al ., ; Widhelm et al ., ), Alismatales (Platonova et al ., ; Volkova et al ., ), Amaryllidaceae (Souza et al ., ), Ranunculaceae (Lehtonen, Christenhusz & Falck, ), Malvales (Aubriot, Singh & Knapp, 2016b; Aubriot et al ., 2016b) and Malpighiales (Ghislain et al ., ). These and other similar papers are leading towards ever more stable classifications.…”