Tag Archives: systematics

Deep sequencing coming for three taxa at key phylogenetic nodes

Following his recent visit to Cambridge, Josh Mylne (UWA) will be collaborating with Jill Harrison (Cambridge) and Kingsley Dixon (Perth Botanic Garden) to sequence the transcriptomes of three rare taxa at key phylogenetic nodes.

Kingsley collected the lycophytes Phylloglossum drummondii and Isoetes drummondii and the basal angiosperm representative Trithuria bibracteata from Alison Baird Reserve, Kenwick in Western Australia this week.

Lycophytes from the Alison Baird Reserve.

Isoetes drummondii (A,D), Phylloglossum drummondii (B,E) and Trithuria bibracteata (C,F) collected from the Alison Baird reserve.

Although lycophytes formed the dominant land plant tree flora in coal swamps that existed over 300 million years ago,[1] they are now small herbs forming three distinct relict lineages.[2] Whilst club mosses such as Phylloglossum comprise c. 400 species, spike mosses such as Selaginella comprise c.700 species and quillworts such as Isoetes comprise c. 150 species.

As the evolutionary divergence of these three lineages was ancient, and the taxa sampled are rare, the new sequence data will be useful in comparative and phylogenetic studies that seek to sample densely at the base of the plant tree of life to minimize long branch artefacts.

Phylloglossum also has corms, organs with a unique ‘fuzzy morphology’ and root/shoot-like identity.[3] The new sequence data will be helpful to future evo-devo projects aiming to determine homologies.

In contrast, Trithuria comprises just 12 species and sits at a key evolutionary divergence point higher up the plant tree of life. It is an aquatic angiosperm placed in the family Hydatellaceae, one of three families in the basal angiosperm order Nymphales.[4]

Trithuria differs from other water lilies in that it is tiny with narrow grass-like leaves, and the flowers may not be homologous to other angiosperm flowers, having an ‘inside out’ floral whorl arrangement.[5]

Again, the new sequence data will be useful in future systematic and evo-devo studies.

To access the raw reads or de novo assembled transcriptomes when they become available please contact Josh Mylne at joshua.mylne@uwa.edu.au.

Further reading

  1. Taylor et al. (2009). Palaeobotany: The biology and evolution of fossil plants. Academic Press, Burlington.
  2. Pryer et al. (2001). Horsetails and ferns are a monophyletic group and the closest living relatives to seed plants. Nature 409: 618-622. doi:10.1038/35054555
  3. Bower FO. 1885 On the development and morphology of Phylloglossum drummondii. Philosophical Transactions of the Royal Society of London 176:665–678. doi:10.1098/rstl.1885.0012
  4. Saarela et al. (2007). Hydatellaceae identified as a new branch near the base of the angiosperm phylogenetic tree. Nature 446, 312-315. doi:10.1038/nature05612
  5. Rudall et al. (2009). Nonflowers near the base of extant angiosperms? Spatiotemporal arrangement of organs in reproductive units of Hydatellaceae and its bearing on the origin of the flower. American Journal of Botany 96:67-82. doi:10.3732/ajb.0800027

Australia’s national flower is an invasive species – even in Australia

Phylogeography of invasive Acacia

Phylogeography of invasive Acacia

Australia’s national flower, Acacia pycnantha (the golden wattle), is native to New South Wales, Victoria and South Australia. And very pretty it is too. But this species was introduced and has become invasive in Western Australia and is probably naturalizing in some areas of New South Wales and South Australia from cultivated plantings in revegetation projects and along roadsides. A. pycnantha is also an invasive species in the Eastern and Western Cape Provinces of South Africa, in Portugal, and possibly in California.

Understanding botanical introduction and invasion histories has important practical implications. The selection of effective host-specific biocontrol agents for invasive plants can depend on identifying which subspecific entities of the plant were introduced. Following the success of other biological control agents against Australian acacias in South Africa, a gall-forming wasp and a seed-feeding weevil have been used to try to control the plant.

A recent paper published in Annals of Botany aims to place invasive populations of Acacia pycnantha in the context of historical biogeographical patterns in the native range of the species in south-eastern Australia. The authors use plastid and nuclear DNA markers to reconstruct phylogenetic relationships among invasive and native populations, and to compare genetic diversities in these invasive and native populations. They show that the invasive genotype found in South Africa is similar to the invasive genotypes in Portugal and Western Australia and thus introduction of the same variant of gall-forming wasp successfully used for biological control in South Africa is recommended.

 

Elucidating the native sources of an invasive tree species, Acacia pycnantha, reveals unexpected native range diversity and structure. (2013) Annals of Botany 111 (5): 895-904. doi: 10.1093/aob/mct057
Understanding the introduction history of invasive plant species is important for their management and identifying effective host-specific biological control agents. However, uncertain taxonomy, intra- and interspecific hybridization, and cryptic speciation may obscure introduction histories, making it difficult to identify native regions to explore for host-specific agents. The overall aim of this study was to identify the native source populations of Acacia pycnantha, a tree native to south-eastern Australia and invasive in South Africa, Western Australia and Portugal. Using a phylogeographical approach also allowed an exploration of the historical processes that have shaped the genetic structure of A. pycnantha in its native range. Nuclear (nDNA) and plastid DNA sequence data were used in network and tree-building analyses to reconstruct phylogeographical relationships between native and invasive A. pycnantha populations. In addition, mismatch distributions, relative rates and Bayesian analyses were used to infer recent demographic processes and timing of events in Australia that led to population structure and diversification. The plastid network indicated that Australian populations of A. pycnantha are geographically structured into two informally recognized lineages, the wetland and dryland forms, whereas the nuclear phylogeny showed little geographical structure between these two forms. Moreover, the dryland form of A. pycnantha showed close genetic similarity to the wetland form based on nDNA sequence data. Hybrid zones may explain these findings, supported here by incongruent phylogenetic placement of some of these taxa between nuclear and plastid genealogies.
It is hypothesized that habitat fragmentation due to cycles of aridity inter-dispersed with periods of abundant rainfall during the Pleistocene (approx. 100 kya) probably gave rise to native dryland and wetland forms of A. pycnantha. Although the different lineages were confined to different ecological regions, we also found evidence for intraspecific hybridization in Victoria. The invasive populations in Portugal and South Africa represent wetland forms, whereas some South African populations resemble the Victorian dryland form. The success of the biological control programme for A. pycnantha in South Africa may therefore be attributed to the fact that the gall-forming wasp Trichilogaster signiventris was sourced from South Australian populations, which closely match most of the invasive populations in South Africa.

 

Free paper — Genome size in Anthurium evaluated in the context of karyotypes and phenotypes

Little is known about the genome of Anthurium other than chromosome observations, which frequently indicate supernumerary (“B”) chromosomes. New genome size estimates for 34 species and nine cultivars presented here  provide insights into genome organization and evolution in this very large genus.

Free paper — Identification of Stylosanthes guianensis varieties using molecular genetic analysis

Molecular genetic diversity and population structure analysis were used to clarify the controversial botanical classification of Stylosanthes guianensis.  In this paper, the accessions were clustered in nine groups, each of which was mainly composed of only one of the four botanical varieties.

Free paper — Dividing without centrioles

Innovative MTOCs organize mitotic spindles in bryophytes, the earliest extant lineages of land.
Triple staining of γ-tubulin, microtubules, and nuclei here reveal that three types of MTOCs initiate spindles in bryophytes. Polar organizers in liverworts and plastid MTOCs in hornworts are unique and nuclear envelope MTOCs in mosses appear like those in seed plants.

  • Roy C. Brown and Betty E. Lemmon

Dividing without centrioles: innovative MTOCs organize mitotic spindles in bryophytes, the earliest extant lineages of land plantsAoB PLANTS  http://dx.doi.org/10.1093/aobpla/plr028