Calothamnus Quadrifidus Research Articles

Non‐native plants and nitrogen addition have little effect on pollination and seed set in 3‐year‐old restored woodland

AbstractHuman activities can disrupt the insect pollination process, which can trigger a decline in pollination and plant reproductive output. Floral visitors are not equally effective pollinators, and it is unknown how multiple changes to an environment further change the effectiveness of insect pollination for native plants. We investigated how herbicide treatment, the presence of non‐native plants and addition of nitrogen fertiliser change the relative importance of different species of floral visitors to four native plant species: Callistemon phoeniceus, Calothamnus quadrifidus, Hakea lissocarpha and Banksia sessilis. Our field site was a large‐scale revegetation site in south‐west Western Australia in which the presence of non‐native plants and nitrogen deposition were experimentally manipulated. Experimental exclusion of floral visitors revealed pollinators were likely required for the seed set of three of the native species, and none of the four plant species were pollen‐limited. We observed 8936 floral visitors of 249 morphospecies from 14 insect orders on four native and two non‐native plant species. From PIV calculations, 57% of floral visitors were potential pollinators, with the remainder considered just visitors due to their low Pollinator Importance Value (PIV). The introduced Apis mellifera (European honey bee, Apidae) was the most frequent floral visitor and the most effective pollinator of all four native plant species. The presence of two non‐native plant species and addition of nitrogen fertiliser did not affect the effectiveness of the potential pollinators, or the viable seeds produced by the four native plant species.

Effect of plant root symbionts on performance of native woody species in competition with an invasive grass in multispecies microcosms.

The majority of terrestrial plants form mutualistic associations with arbuscular mycorrhizal fungi (AMF) and rhizobia (i.e., nitrogen‐fixing bacteria). Understanding these associations has important implications for ecological theory and for restoration practice. Here, we tested whether the presence of AMF and rhizobia influences the performance of native woody plants invaded by a non‐native grass in experimental microcosms. We planted eight plant species (i.e., Acacia acuminata, A. microbotrya, Eucalyptus loxophleba subsp. loxophleba, E. astringens, Calothamnus quadrifidus, Callistemon phoeniceus, Hakea lissocarpha and H. prostrata) in microcosms of field‐conditioned soil with and without addition of AMF and rhizobia in a fully factorial experimental design. After seedling establishment, we seeded half the microcosms with an invasive grass Bromus diandrus. We measured shoot and root biomass of native plants and Bromus, and on roots, the percentage colonization by AMF, number of rhizobia‐forming nodules and number of proteaceous root clusters. We found no effect of plant root symbionts or Bromus addition on performance of myrtaceous, and as predicted, proteaceous species as they rely little or not at all on AMF and rhizobia. Soil treatments with AMF and rhizobia had a strong positive effect (i.e., larger biomass) on native legumes (A. microbotrya and A. acuminata). However, the beneficial effect of root symbionts on legumes became negative (i.e., lower biomass and less nodules) if Bromus was present, especially for one legume, i.e., A. acuminata, suggesting a disruptive effect of the invader on the mutualism. We also found a stimulating effect of Bromus on root nodule production in A. microbotrya and AMF colonization in A. acuminata which could be indicative of legumes’ increased resource acquisition requirement, i.e., for nitrogen and phosphorus, respectively, in response to the Bromus addition. We have demonstrated the importance of measuring belowground effects because the aboveground effects gave limited indication of the effects occurring belowground.

An investigation of ethylene sensitivity in three Australian native cut flower genera, Calothamnus , Grevillea and Philotheca

Abstract Knowing a plant’s sensitivity to ethylene is crucial in order to negate ethylene-mediated senescence with inhibitors such as silver thiosulphate (STS) or 1-methylcyclopropene (1-MCP). The ethylene sensitivity of three exported Australian native flowers, Calothamnus quadrifidus, Grevillea ‘Superb’ and Philotheca myoporoides was previously unknown. The first two of these three species produced steady amounts of ethylene during vase life. The vase life of all three species was not significantly shortened after exposing the flowers to ethylene (10 μL L−1 for 12 h). However, STS treatment (0.5 mM pulse for 12 h prior to ethylene exposure) significantly extended the vase life of G. ‘Superb’ from 7 d (control) to 10 d. In contrast, 1-MCP (10 nL L−1), applied either at the same time as ethylene exposure, or 12 h prior to challenging plants with ethylene, did not result in significant differences in vase life over the control for any of the three species. Ethylene production was comparable between the STS and 1-MCP treatments for G. ‘Superb’ over the 11 d test period and was less than that of the control. Endogenous production of ethylene did not appear to relate to longevity or the effectiveness of the protectants. Our results indicate that the treatment of C. quadrifidus and P. myoporoides with ethylene inhibitors is unnecessary and is therefore not recommended. The positive effect of STS on G. ‘Superb’ was not linked to ethylene sensitivity, but may relate to another of the beneficial properties of STS, such as an ionic effect.

Corrigendum

Journal of EcologyVolume 105, Issue 2 p. 558-558 CorrigendumFree Access Corrigendum This article corrects the following: Native soilborne pathogens equalize differences in competitive ability between plants of contrasting nutrient-acquisition strategies Felipe E. Albornoz, Treena I. Burgess, Hans Lambers, Hannah Etchells, Etienne Laliberté, Alison Power, Volume 105Issue 2Journal of Ecology pages: 549-557 First Published online: August 1, 2016 First published: 17 October 2016 https://doi.org/10.1111/1365-2745.12676AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat In the paper by Albornoz et al. (2016), the authors inadvertently reproduced the figure image of figure 4 for figure 5. The authors and journal would like to correct this error. The captions for both images are correct in the original published article. This was an honest error, and the results and conclusions of the article are not affected. The correct version of Figure 5 is below: Figure 5Open in figure viewerPowerPoint Root-to-shoot ratio of non-mycorrhizal cluster-rooted (top row, Banskia attenuata and Banksia menziesii) and ectomycorrhizal (ECM) plant species (bottom row, Calothamnus quadrifidus and Eucalyptus todtiana) grown together in competition with each other: one ECM plant species planted with both cluster-rooted plant species under two inoculum treatments: (i) − Phytophthora and (ii) ‘+ Phytophthora’ (mix of Phytophthora arenaria, P. taxon cooljarloo, P. taxon kwongan, P. aff. rosacearum and P. rosacerarum). Different letters indicate significant (P ≤ 0.05) differences among treatments based on post hoc Tukey's tests. Means and 95% confidence intervals (CI) are shown. Reference Albornoz, F.E., Burgess, T.I., Lambers, H., Etchells, H. & Laliberté, E. (2016) Native soilborne pathogens equalize differences in competitive ability between plants of contrasting nutrient-acquisition strategies. Journal of Ecology, doi:10.1111/1365-2745.12638. CrossrefWeb of Science®Google Scholar Volume105, Issue2March 2017Pages 558-558 FiguresReferencesRelatedInformation

Phylogeographic evidence for two mesic refugia in a biodiversity hotspot.

Phylogeographic studies of flora in species-rich south-western Australia point to complex evolutionary histories, reflecting patterns of persistence and resilience to climatic changes during the Pleistocene. We asked whether coastal areas of the mid-west and south, as well as granite outcrops and inland ranges, have acted as major refugia within this region during Pleistocene climatic fluctuations by analysing phylogeographic patterns in the shrub Calothamnus quadrifidus R.Br. (Myrtaceae). We determined variation in chloroplast DNA data for 41 populations across the geographic range. Relationships and major clades were resolved using parsimony and Bayesian analyses. We tested for demographic and spatial expansion of the major clades and estimated clade divergence dates using an uncorrelated, lognormal relaxed clock based on two conservative chloroplast mutation rates. Two distinct phylogeographic clades were identified showing divergence during the Pleistocene, consistent with other phylogeographic studies of south-west Australian flora, emphasising the impact of climatic oscillations in driving divergence in this landscape. The southern clade was more diverse, having higher haplotype diversity and greater genetic structure, while the northern clade showed evidence of fluctuation in population size. Regions of high haplotype diversity with adjacent areas of low diversity observed in each clade indicated the locations of two coastal refugia: one on the south coast and another along the mid-west coast. This is the first evidence for major Pleistocene refugia using chloroplast genetic data in a common, widespread species from this region.

Germinability of seeds stored in capsules on plants of two myrtaceous shrubs: differences among age cohorts and between species

Canopy-stored seed banks are a common trait among members of several plant families in sclerophyllous woodlands of Australia and South Africa, with their fruits usually opening in response to damage or fire. Unknown is whether the degree of dormancy and of germination differs among age cohorts in seeds stored on the mother plant. We examined the extent and speed of germination from two intensely serotinous myrtaceous species, Callistemon glaucus and Calothamnus quadrifidus, for seed held in capsules for up to 9 years. Germination of both species differed significantly among age cohorts (P < 0.0001). However, no consistent increase in germination over a range of temperatures with storage was found, suggesting that no after-ripening occurred and that seeds were non-dormant at maturity. Differences among cohorts may be due to pre-conditioning. Significant (P ≤ 0.0214) differences occurred between the small-seeded Callistemon and the large-seeded Calothamnus. Germination was (1) optimum at ≥20°C for Callistemon but at <20°C for Calothamnus, (2) 9–12 days earlier for Callistemon than for Calothamnus, and (3) higher in light than in darkness for Callistemon but equal in both light conditions for Calothamnus. While germination of the species differed in important features, we would expect synchronous germination of all age cohorts to occur following fire and the onset of regular rainfall.

Seed production, germinability and seedling growth for a bird-pollinated shrub in fragments of kwongan in south-west Australia

In this study we investigate the effect of population size on the proportion of flowers that produce a fruit (fruit set), the number of seeds per fruit (seed set), seed germinability, seedling mortality and growth in a range of population fragments for the bird-pollinated mixed mating system shrub Calothamnus quadrifidus R. Br. (Myrtaceae). We found no significant linear relationship ( p < 0.05) between population fragment size and fruit set in any of the three years reproduction was studied. In contrast, we found a very strong positive correlation between the number of seeds produced per fruit and increasing population fragment size for each of the three years. We found no significant linear relationships between population fragment size and seed germination, or seedling growth and mortality. The most plausible explanation for the decline in seed set is increased inbreeding in smaller populations. Although a previous mating system analysis with allozymes did not reflect the above, we present evidence from other lines of inquiry to indicate that inbreeding does increase in smaller populations, but is masked by post-zygotic lethal systems that eliminate genetically incompetent homozygous embryos. We found no evidence that highly mobile pollinators transporting pollen among fragments rescue small fragments from inbreeding. We discuss the implications of our findings for the conservation of plant diversity in fragments of species rich Mediterranean climate shrublands.