The high species endemism characteristic of many of the world's terrestrial island systems provides a model for studying evolutionary patterns and processes, yet there has been no synthesis of studies to provide a systematic evaluation of terrestrial island systems in this context. The banded iron formations (BIFs) of south-western Australia are ancient terrestrial island formations occurring within a mosaic of alluvial clay soils, sandplains and occasional granite outcropping, across an old, gently undulating, highly weathered, plateau. Notably, these BIFs display exceptionally high beta plant diversity. Here, we address the determinants and consequences of genetic diversity for BIF-associated plant species through a comprehensive review of all studies on species distribution modelling, phylogenetics, phylogeography, population genetics, life-history traits and ecology. The taxa studied are predominantly narrowly endemic to individual or a few BIF ranges, but some have more regional distributions occurring both on and off BIFs. We compared genetic data for these BIF-endemic species to other localised species globally to assess whether the unique history and ancestry of BIF landscapes has driven distinct genetic responses in plants restricted to this habitat. We also assessed the influence of life-history parameters on patterns of genetic diversity. We found that BIF-endemic species display similar patterns of genetic diversity and structure to other species with localised distributions. Despite often highly restricted distributions, large effective population size or clonal reproduction appears to provide these BIF-endemic species with ecological and evolutionary resilience to environmental stochasticity. We conclude that persistence and stochasticity are key determinants of genetic diversity and its spatial structure within BIF-associated plant species, and that these are key evolutionary processes that should be considered in understanding the biogeography of inselbergs worldwide.

The relationships among rare ‘leafless’ species of Tetratheca Sm. occurring on banded ironstone ranges near Koolyanobbing, Western Australia, and allied, unclassified, populations from Eneabba, Newdegate and the Die Hardy Range have been assessed by molecular characters. These findings, in conjunction with morphological investigations, have identified a new species and two new subspecies from within the ‘T. aphylla group’ and these are formally described here. Tetratheca nephelioides R.Butcher, is geographically restricted to the Eneabba area and has close morphological affinity to T. aphylla F.Muell. Tetratheca aphylla subsp. megacarpa R.Butcher, is restricted to the Newdegate area, some 300 km south of the only known populations of T. aphylla subsp. aphylla in the Helena and Aurora Range. Tetratheca paynterae Alford subsp. cremnobata R.Butcher is restricted to the Die Hardy Range, c. 10 km north-east of the only known population of T. paynterae subsp. paynterae at ‘Windarling’. All of these taxa are recognised as Declared Rare Flora. In the process of updating the existing key to ‘leafless’ species of Tetratheca to include these new taxa, two additional new species were identified from within collections of T. nuda Lindl. These are described here as T. angulata R.Butcher and T. applanata R.Butcher. Images and distribution maps for all taxa are provided.

Abstract. Morphological and molecular investigations of taxon relationships among rare species of Tetratheca Sm. occurring near Koolyanobbing, Western Australia, have confirmed the distinctness of T. aphylla F.Muell., T. harperi F.Muell. and T. paynterae Alford and identified three new rare taxa from collections affiliated with T. aphylla and T. paynterae. The recognition of these taxa at specific and sub-specific ranks is based on their different degrees of morphological and molecular divergence, combined with geographic disjunction. Cladistic analysis of nrDNA internal transcribed spacer and cpDNA trnL-trnF sequences from a range of Tetratheca species from Western Australia and the eastern states indicates that T. aphylla, T. harperi and T. paynterae belong to three separate evolutionary lineages and that the endemism displayed among these taxa to small, disjunct ranges within the same geographic area, is a result of in situ speciation due to historical fragmentation. These results exemplify the extremely high conservation value of the Yilgarn banded ironstone ranges. The superficial similarity among the study taxa in having a 'leafless' habit can be seen to be adaptive convergence in response to the marginal and semi-arid environments in which they occur, and this character is highly homoplastic within the genus.

Volatile organic compounds emitted by growing intact oilseed rape plants have been detected using an entrainment apparatus enabling volatile headspace analysis by thermal desorption coupled to capillary gas chromatography-mass spectrometry. In total, 22 volatile compounds were identified as being emitted during the flowering period. The main constituents were alpha-farnesene (a sesquiterpene); beta-myrcene (a monoterpene); linalool (a monoterpene alcohol) and the 'green leaf' volatile (E)-3-hexen-1-ol acetate. These compounds constituted between 50 and 87% (mean 68%) of the total volatiles emitted in all of the entrainments carried out with flowering oilseed rape plants. The remaining constituents consisted of a range of compounds including other terpenoids, the characteristic 'green leaf' volatile (E)-3-hexen-1-ol, short chain alcohols and ketones, organic sulphides and nitrogen-containing compounds. These were generally present as minor constituents but some plant entrainments revealed that higher relative amounts could be emitted. This was particularly apparent for dimethyl disulphide, 3-methyl-2-pentanone, 3-hydroxy-2-butanone, sabinene, isomyrcenol and (E)-3-hexen-1-ol. The possible role of the 22 compounds in respiratory mucosa and conjunctiva irritation associated with airborne releases from oilseed rape is discussed.

Thermal desorption coupled to capillary gas chromatography-mass spectrometry has been used to identify volatile chemicals released from the flowers of five varieties of oilseed rape. An entrainment apparatus for volatile headspace analysis is described. The major classes of compound found were organic sulphides, C4 substituted compounds, aldehydes and terpenes. The possible role of these compounds in the human allergic-type response associated with oilseed rape is discussed.