Gary J. Houliston

A CASE OF REVERSAL: THE EVOLUTION AND MAINTENANCE OF SEXUALS FROM PARTHENOGENETIC CLONES IN HIERACIUM PILOSELLA

We provide evidence for the origin of sexual individuals from parthenogenetic progenitors in natural populations. We demonstrate that this reversal has occurred independently in three geographically separated populations of the Asteraceous polyploid, Hieracium pilosella. We used chromosome counts and flow cytometry to determine ploidy and crossing experiments and flow cytometry to confirm sexuality. Inter–simple sequence repeat and allozyme markers demonstrated that the sexuals at each site were more closely related to their parthenogenetic neighbors than to sexuals at other sites. The same markers were used to estimate levels of ramet diversity, which were equally high among the parthenogens and sexuals. The observation that sexuals were always tetraploid is possibly explained by their having arisen through a rare sexual event, the fusion of two reduced (2x) gametes from pentaploid, facultatively apomictic parents. Such a reversal from almost total clonality to obligate sexual reproduction is unusual, and further work will determine whether the sexuals are in evolutionary equilibrium, are increasing at the expense of asexuals, or are simply surviving because of a lack of negative selection pressure.

Sexual reproduction in field populations of the facultative apomict,Hieracium pilosella

Abstract Hand pollination under New Zealand field conditions of capitula from each of six populations of Hieracium pilosella (maternal parent) with the closely related but morphologically distinct H. aurantiacum produced F1 hybrids in every case. The frequency of F1 hybrid offspring among the populations ranged from 0.2 to 21.6%. Involucral bract characteristics, leaf shape, and petal colour were the most useful characters for identifying hybrid progeny. Most F1 hybrids were able to set seed by apomixis, but a sexual individual was also recovered. The discovery that both tetraploid and pentaploid H. pilosella can reproduce sexually, following artificial pollination under field conditions, in New Zealand has implications for the bio‐control of this species. Sexually reproducing plants are more likely to evolve resistance to host‐specific bio‐control agents than are apomicts. These results are part of a larger, ongoing research programme investigating the role of the environment in the expression of apomixis.

New Lepidium (Brassicaceae) from New Zealand

Abstract A revision of the New Zealand endemic Lepidium oleraceum and allied species is presented. Sixteen species are recognised, 10 of these are new. The new species are segregated on the basis of morphological characters supported by molecular data obtained from three DNA markers (two rDNA and one cpDNA). One species, Lepidium castellanum sp. nov., is endemic to the Kermadec Islands where it is sympatric with Lepidium oleraceum. The North Island of New Zealand supports four species, with two of them, Lepidium amissum sp. nov. and Lepidium obtusatum, now extinct. The South Island supports six species, that, aside from Lepidium banksii, Lepidium flexicaule and Lepidium oleraceum, are all confined to the south-eastern half of the island (Lepidium aegrum sp. nov., Lepidium crassum sp. nov. and Lepidium juvencum sp. nov.). One of these, Lepidium juvencum sp. nov., extends to Stewart Island. The Chatham Islands support six species (Lepidium flexicaule, Lepidium oblitum sp. nov., Lepidium oleraceum, Lepidium oligodontum sp. nov., Lepidium panniforme sp. nov., and Lepidium rekohuense sp. nov.), one of which, Lepidium oligodontum sp. nov., extends to the Antipodes Islands group. The remote, subantarctic Bounty Islands group supports one endemic, Lepidium seditiosum sp. nov., which is the only vascular plant to be recorded from there. Lepidium limenophylax sp. nov. is known from islands off the south-western side of Stewart Island/Rakiura, The Snares and Auckland islands. Lepidium naufragorum, although not related to Lepidium oleraceum and its allies, is also treated because populations with entire leaves are now known. Typification is undertaken for Lepidium banksii, Lepidium oleraceum, Lepidium oleraceum var. acutidentatum, var. frondosum and var. serrulatum.

Genetic and morphological evidence for localised interspecific gene flow in Phormium (Hemerocallidaceae)

Abstract Gene flow between two species of Phormium, P. tenax and P. cookianum, was investigated by analysis of morphology, AFLP profiles, and chloroplast simple sequence repeats (cpSSRs). We examined 44 wild samples of Phormium, focusing on Okiwi Bay (Marlborough, New Zealand), where the two species grow in close proximity. Two genetic groups corresponding with P. tenax and P. cookianum are evident in analyses of AFLP profiles from Okiwi Bay. The profiles of Okiwi Bay plants were also compared with profiles from three hypothetically pure P. cookianum populations from Marlborough, and a representative sample of P. tenax combined from sites throughout New Zealand. Bayesian analysis of genetic admixture suggests that all of the plants resembling P. tenax and most of the plants resembling P. cookianum sampled from Okiwi Bay are admixed (i.e., of hybrid origin). Neighbour Net and principal component analyses reveal that P. cookianum and P. tenax from Okiwi Bay are genetically intermediate between “pure” populations of the species. Further, all of the Okiwi Bay samples share the same chloroplast haplotype. Analysis of morphological characters comparing a small number of Okiwi Bay P. tenax plants to selected P tenax plants from throughout New Zealand under common garden conditions confirm that the Okiwi Bay population includes plants with unusually small stature and fruit characters approaching P cookianum. These results support a hypothesis of local introgression between P. tenax and P. cookianum.

Metal bioavailability dynamics during a two-year trial using ryegrass (Lolium perenne L.) grown in soils treated with biosolids and metal salts

A 24-month field lysimeter experiment using ryegrass (Lolium perenne L.) grown in three soil types was used to investigate metal bioavailability dynamics following amendment with biosolids and metal salts (Cd, Cu, Ni, Zn). Common surrogates of soil metal bioavailability (total soil metal, EDTA, Ca(NO3)2, total dissolved, diffusive gradient in thin film, and modelled free ion activity) were determined on soil samples taken every 6 months. Ryegrass was also harvested every 6 months and analysed for metal concentrations. Across soils and treatments dissolved organic carbon (DOC) and pH decreased, whereas dissolved Ca and Mg increased with time. The free ion activity concentrations of each metal also increased over 24 months, whereas Ca(NO3)2-extracted metals were unchanged. Zinc presented the most changes in bioavailability status, with total Zn concentration decreasing over time, and EDTA-extractable and soil solution Zn increasing significantly by 1.82mgkg -1 (1.1%) and 1.52mgL -1 (29%), respectively. Shoot concentration of Zn increased by 1.32mgkg -1 (2.7%), whereas shoot Ni concentration decreased by 0.65mgkg -1 (4%). The findings of this study clearly demonstrated that over 24 months, soil metal bioavailability and shoot metal concentrations register only minor changes and appear to be unaffected by soil DOC and pH fluctuations.

Sophora microphylla (Fabaceae) Microsatellite Markers and their Utility Across the Genus

Premise of the study: Genus-specific microsatellite markers were developed for Sophora for population genetic and systematic studies of the group in New Zealand, and potentially elsewhere in the geographic range. Methods and Results: From sequencing a total genomic DNA library (using Roche 454), we identified and developed 29 polymorphic microsatellite markers for S. microphylla and S. chathamica. We tested 12 of these markers on 14 S. chathamica individuals and four S. microphylla populations. All loci amplified in both species and species-specific alleles occurred at seven loci. In S. microphylla populations, the observed and expected heterozygosities ranged from 0.000–0.960 and 0.000–0.908, respectively, with alleles per locus ranging from seven to 23. Conclusions: The developed markers will be valuable in studies of phylogenetics, population structure, mating system, and selection of provenances for restoration projects.

Geographic patterns of genetic variation in Cordyline australis; does fingerprinting recover phenotypic and phenological patterns?

Abstract The genetic variation of 28 populations of Cordyline australis (cabbage tree, tī kōuka) grown from wild-collected seed from across New Zealand was assessed using amplified fragment length polymorphism (AFLP). There was strong geographical structure in the data, with the main differentiation being between plants from the northern North Island and those from the central North Island and further south; a split that was not concurrent with any obvious physical barriers. Further smaller genetic divisions were evident in the data, with eight groups found across the range of C. australis, while genetic variation was found to decrease markedly with latitude. We compare the patterns of genetic variation with earlier studies looking at morphological variation across the range of C. australis, as well as the relative survival of plants from different latitudes in three common garden replicates.

New threats to endangered Cook’s scurvy grass (Lepidium oleraceum; Brassicaceae): introduced crop viruses and the extent of their spread

To date, most research conducted on plant viruses has centred on agricultural systems where viruses greatly reduce economic output. Introduced viruses are globally common and there is a lack of knowledge around how they might affect natural populations. Although it has been suggested that infectious disease may have played an underestimated role in past species extinctions, there is little empirical evidence. Cook’s scurvy grass (Lepidium oleraceum Sparrm. ex G.Forst; Brassicaceae) is a threatened coastal plant endemic to New Zealand. Following the discovery of Turnip mosaic virus (TuMV) in some glasshouse cultivated specimens, we surveyed wild extant Lepidium populations on the Otago coast for TuMV while screening for two other common crop viruses. We show that TuMV is almost ubiquitous among remaining wild L. oleraceum populations on the South Island’s east coast and report the first record of L. oleraceum as a host for both Cauliflower mosaic virus and Turnip yellows virus. The high incidence of virus infection throughout the study populations may make this system one of the first examples of introduced viruses affecting the conservation of a threatened plant species.

Olearia telmatica (Asteraceae: Astereae), a new tree species endemic to the Chatham Islands

Abstract Olearia teimatica is described as a new species endemic to the two main islands of the Chatham Island group, Chatham (Rekohu/Whareka‐uri) and Pitt (Rangiauria). Oiearia teimatica is distinguished from the closely related O. traversiorum by its smaller growth habit, slender trunk, narrower leaves, earlier flowering, lemon‐yellow and less hairy corolla, less branched inflorescence with fewer capitula, fulvous hairs on the inflorescence, readily dispersed seed, and abscising inflorescences. Oiearia teimatica and O. traversiorum are further distinguished by Amplified Fragment Length Polymorphism DNA data, as samples of both species collected from sites on Pitt Island and Chatham Island form two discrete groups in a principal coordinates analysis. As with all other species of Oiearia sect. Divaricaster, O. teimatica has a chromosome number of 2n =108. Oiearia traversiorum is the correct species epithet for plants previously known as O. traversii because the protologue for the species clearly and unambiguously states that the name commemorates both W. T. L. Travers (father) and H. H. Travers (son). Arevised description is provided for O. traversiorum.

A plant growth-promoting symbiosis between Mycena galopus and Vaccinium corymbosum seedlings

Typically, Mycena species are viewed as saprotrophic fungi. However, numerous detections of Mycena spp. in the roots of green plants suggest that a continuum from saprotrophy to biotrophy could exist. In particular, mycenoid species have repeatedly been found in Ericaceae plant roots. Our study asked whether (1) Mycena species are commonly found in the roots of green Ericaceae plants; (2) Mycena sequences are limited to a single group/lineage within the genus; and (3) a Mycena sp. can behave as a beneficial root associate with a typical ericoid mycorrhizal plant (Vaccinium corymbosum), regardless of how much external labile carbon is available. We detected Mycena sequences in roots of all sampled Ericaceae plants. Our Mycena sequences clustered in four different groups distributed across the Mycena genus. Only one group could be assigned with confidence to a named species (M. galopus). Our Mycena sequences clustered with other Mycena sequences detected in roots of ericoid mycorrhizal plant species collected throughout Europe, America, and Australia. An isolate of M. galopus promoted growth of V. corymbosum seedlings in vitro regardless of external carbon supply in the media. Seedlings inoculated with M. galopus grew as well as those inoculated with the ericoid mycorrhizal fungus Rhizoscyphus ericae. Surprisingly, this M. galopus isolate colonized Vaccinium roots and formed distinctive peg-like structures. Our results suggest that Mycena species might operate along a saprotroph–symbiotic continuum with a range of ericoid mycorrhizal plant species. We discuss our results in terms of fungal partner recruitment by Ericaceae plants.