Recruitment limitation in dry sclerophyll forests: Regeneration requirements and potential density‐dependent effects in Eucalyptus tricarpa (L.A.S. Johnson) L.A.S. Johnson & K.D. Hill (Myrtaceae)

Recruitment limitation in canopy trees is receiving increasing attention as restoration of tree cover for connectivity, biodiversity offsets, carbon‐trading and improved catchment health becomes more prominent. Recruitment limitation is often addressed by examining seed traits and germination requirements. Distance between trees is also often explored as a factor, particularly in agricultural landscapes where forest structure has been altered, with large distances between fragments generating Allee effects linked to pollen limitation. Fewer studies have examined how short distances between trees (high stem densities), which can characterize regenerated forests, might affect recruitment. This study examined recruitment limitation by exploring germination requirements of Eucalyptus tricarpa (red ironbark) and the effects of stem density on seed characters and germination. Eucalyptus tricarpa is a canopy species in the box‐ironbark forests of central Victoria, Australia. During the early European settlement phase in the 1800s these forests were heavily impacted by human disturbances including mining, logging and livestock grazing. In many regenerated stands, now more than 100 years old, current stem density exceeds those documented in 19th century reports and there is little regeneration of key canopy species such as E. tricarpa. In laboratory trials seed germinated at 18°C in darkness, and while viability varied among populations, overall it remained high (91–96%) and did not differ among populations with different stem densities. An in situ germination trial addressing sowing season, ground‐cover, soil‐ripping, canopy‐cover and stem density recorded no germination. High stem density in coppicing box‐ironbark forest was hypothesized to limit resources for reproduction; however, no relationship was found between nearest neighbour distance, allocation to selected reproductive structures or seed viability. The relative insensitivity of reproductive allocation to intraspecific competition (high stem density) may be interpreted as a trait linked to unpredictable environments and consistent with long‐lived species. In terms of management, recruitment limitation in E. tricarpa appears not primarily attributable to seed viability, tested seedbed treatments or stem density so further factors, including fire, now require exploration.     

The numerical intraspecific taxonomy of Eucalyptus globulus Labill. (Myrtaceae)

The history of the taxonomic perception of Eucalyptus globulus Labill. is described. Morphological-geographical clusters within E. globulus are identified through the use of a polythetic, agglomerative classificatory strategy. The results of the numerical analysis and unpublished data on geographic variation strongly suggest that four subspecies should be recognized. Thus three taxa formerly regarded as species are reduced to subspecies of E. globulus.     

Development of 198 novel EST-derived microsatellites in Eucalyptus (Myrtaceae)

? Premise of the study: Expressed sequence tag (EST)-derived microsatellites were identified in Eucalyptus through screening the GenBank database. The loci were sequence-verified and explored for polymorphism among 20 genotypes. ? Methods and Results: In total, 198 novel microsatellites were developed from 8262 unigenes, with the identity of 73.6-100% to the original sequences and presence of the expected repeat motifs. One hundred and eighty-four markers proved to be polymorphic among 10 E. urophylla and 10 E. tereticornis genotypes, with the number of alleles per locus, observed heterozygosity, and polymorphic information content being 2-17 (mean: 7.11), 0-1.0 (mean: 0.4511), and 0.0940-0.9131 (mean: 0.6571), respectively. ? Conclusions: These markers will be useful for germplasm characterization, genome mapping, and gene tagging for economic traits in the two species examined and may have potential for genetic applications in Eucalyptus.     

Chloroplast DNA evidence for reticulate evolution in Eucalyptus (Myrtaceae)

Four highly differentiated chloroplast DNA (cpDNA) lineages were identified in the forest tree species Eucalyptus globulus Labill. (Myrtaceae) in Australia using restriction site polymorphisms from Southern analysis. The cpDNA variation did not conform with ssp. boundaries, yet there was a strong geographical pattern to the distribution of the lineages. One lineage (C) was geographically central and widespread, whereas the other three lineages were found in peripheral populations: Western (W), Northern (N) and Southern (S). Thirteen haplotypes were detected in E. globulus , seven of which belonged to clade C. At least three of the cpDNA lineages (C, N and S) were shared extensively with other species. On the east coast of the island of Tasmania, there was a major north–south difference in cpDNA in the virtually continuous distribution of E. globulus . Northern populations harboured haplotypes from clade C while southeastern populations harboured a single haplotype from clade S. This difference was also reflected in several co-occurring endemic species. It is argued that the extensive cpDNA differentiation within E. globulus is likely to originate from interspecific hybridization and 'chloroplast capture' from different species in different parts of its range. Superficially, this hybridization is not evident in taxonomic traits; however, large-scale common garden experiments have revealed a steep cline in quantitative genetic variation that coincides with the haplotype transition in Tasmania. Our cpDNA results provide the strongest evidence to date that hybridization has had a widespread impact on a eucalypt species and indicate that reticulate evolution may be occurring on an unappreciated scale in Eucalyptus .     

A cladistic study of Arillastrum, Angophora and Eucalyptus (Myrtaceae)

A cladistic study of Anllastrum, Angophora and Eucalyptus (Myrtaceae). Transformed cladistic; character compatibility; branch and bound, and Farris-Wagner methods gave similar solutions in a cladistic study of Arillastrum, Angophora and Eucalyptus. These analyses, based on morphological characters, indicate that Eucalyptus is a monophyletic group and that its sister taxon is Angophora.
Within Eucalyptus , subgenera Blakella and Corymbia are sister taxa to all other groups; subgenera Monocalyptus, Idiogenes and Gaubaea form a monophyletic group with subgenus Monocalyptus sister to subgenera Idiogenes and Gaubaea ; subgenera Symphyomyrtus and Telocalyptus together also form a monophyletic group and, with Eucalyptus similis (subgenus Eudesmia group 4), are sister to the Monocalyptus group. Eucalyptus subgenus Telocalyptus (4 species), Eucalyptus subgenus Idiogenes (1 species) and Eucalyptus subgenus Gaubaea (2 species) should not be recognized as subgenera and some individual species need further examination. Eucalyptus subgenus Eudesmia is a paraphyletic group.
Some characters are identified as parallelisms, e.g. axillary inflorescences, sepaline operculum, bristle glands, and clustered anthers. A more congruent interpretation of the single operculum of Eucalyptus subgenus Monocalyptus as at least partly petaline rather than solely sepaline in origin is suggested.
The area relationships for the taxa are concordant with those derived from geological and climatological information. New Caledonia is sister area to Australia, and within Australia southwestern Australia is sister area to south-eastern and north-eastern Australia.     

Incongruence between chloroplast and species phylogenies in Eucalyptus subgenus Monocalyptus (Myrtaceae)

Seventy-eight polymorphic cpDNA (chloroplast DNA) characters were found in 13 closely related taxa from Eucalyptus series Amygdalinae (subgenus Monocalyptus) and seven potential outgroup taxa. The strict consensus of six cladograms generated from cpDNA data confirmed monophyly of Monocalyptus. However, cpDNA phylogeny within Monocalyptus was incongruent with taxonomic classification, being more related to geography, even when accessions were from divergent series. Monocalyptus cpDNA formed two major clades. On the island of Tasmania cpDNA was restricted to a single clade, exhibited very little variation, and was phylogenetically related to cpDNA found in central and western Victoria. In contrast, cpDNA of mainland monocalypt taxa was more variable, even within the Amygdalinae. Four out of six Tasmanian Amygdalinae species were polymorphic. The difference between cpDNA of replicates was often greater than differences between species from different series. The low level of cpDNA variation and extensive morphological intergradation between the Tasmanian endemics suggest recent speciation. However, the transfer of cpDNA through hybridization between lineages is the most likely explanation for the observed sharing of cpDNA across series. This study highlights that the geographical pattern to cpDNA variation in Eucalyptus may be an important source of information on past plant distributions in Australia.     

An AFLP marker approach to lower-level systematics in Eucalyptus (Myrtaceae)

Genus Eucalyptus, with over 700 species, presents a number of systematic difficulties including taxa that hybridize or intergrade across environmental gradients. To date, no DNA marker has been found capable of resolving phylogeny below the sectional level in the major subgenera. Molecular markers are needed to support taxonomic revision, assess the extent of genetic divergence at lower taxonomic levels, and inform conservation efforts. We examined the utility of 930 amplified fragment length polymorphisms (AFLPs) for analyzing relationships among Tasmanian taxa of subgenus Symphyomyrtus section Maidenaria. Phenetic and cladistic analyses resolved species into clusters demonstrating significant genetic partitioning, largely concordant with series defined in the most recent taxonomic revision of Eucalyptus. Some departures from current taxonomy were noted, indicating possible cases of morphological convergence and character reversion. Although the resolution obtained using AFLP was greatly superior to that of single sequence markers, the data demonstrated high homoplasy and incomplete resolution of closely related species. The results of this study and others are consistent with recent speciation and reticulate evolution in Maidenaria. We conclude that a combination of phylogenetic and population genetic approaches using multiple molecular markers offers the best prospects for understanding taxonomic relationships below the sectional level in Eucalyptus.     

Interspecific Pollen-Pistil Interaction in Eucalyptus L'Her. (Myrtaceae): The Effect of Taxonomic Distance

The pollen-pistil interaction was investigated in three intraspecific,57 interspecific and six intergeneric crosses using three speciesof Eucalyptus (Myrtaceae) subgenus Symphyomyrtus, section Bisectariaas female parents Interspecific prefertilization isolation occursin the pistil and manifests as a number of pollen-tube abnormalitiesin the style and ovary associated with a lowered probabilityof ovule penetration The major selection points in the pistilare the upper style and the ovary The seventy of abnormalitiesand the probability of pollen-tube arrest in the pistil wasproportional to the taxonomic distance between parent speciesOvule penetrations were seen mainly in crosses within the sectionBisectaria or between the sections Bisectaria and Adnataria Pollen storage, style length and mean maximum temperature duringthe flowering period of the male parent had no significant effecton pollen-tube growth in the crosses used Mechanisms of reproductiveisolation are discussed in relation to evolutionary relationshipsand the implications for taxonomic groupings Eucalyptus L'Hér, pollen-pistil interaction, incongruity, interspecific hybridization, pollen-tube growth, breeding system, taxonomy     

Transferability of microsatellite markers from Eucalyptus spp. to Eugenia dysenterica (Myrtaceae family)

Cagaita (Eugenia dysenterica) is a widespread plant found in the Brazilian cerrado. Its fruit is used for popular consumption and for industrial purposes. A battery of 346 primer pairs developed for Eucalyptus spp. was tested on cagaita. Only 10 primer pairs were found to be transferable between the two species. Using a polyacrilamide gel, an average of 10.4 alleles per locus was detected, in a sample of 116 individuals from 10 natural populations of cagaita. Seven polymorphic loci allowed estimation of genetic parameters, including expected average heterozigosity H_E = 0.442, diversity among populations, R_ST = 0.268 and gene flow Nm = 0.680.     

Volatile leaf oil diversity in the narrow range endemic Eucalyptus argutifolia (Myrtaceae) and its widespread congener Eucalyptus obtusiflora

Variation in the qualitative composition of volatile leaf oil was examined in the rare Eucalyptus argutifolia and its widespread congener Eucalyptus obtusiflora . The results revealed that, consistent with the pattern seen with allozymes, E. argutifolia had less variation within populations than E. obtusiflora . Total leaf oil diversity was also significantly lower in the rare species. As found with allozymes, most leaf oil diversity was within populations, but there was also a significant proportion of the variation between populations (25.2% and 27.3% for E. argutifolia and E. obtusiflora , respectively). There were significant associations between phenotypic distance based on leaf oils and geographical distance and between phenotypic and genetic distance across all populations, but these associations were not evident within species. Factors leading to reduced variation in E. argutifolia appear to affect all types of variation, but the relationships between different types of variation within the species are less apparent.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 738–745.     

Foliar anatomy and micromorphology of eleven species of Eugenia L. (Myrtaceae)

The anatomy and micromorphology of eleven species of Eugenia found in the 'restinga' of Marica, Rio de Janeiro, Brazil, were studied and compared. The characteristics found to be of most use in distinguishing the species are: presence and types of trichomes persistent in the adult material, form and arrangement of overlying cells (epidermal cells over secretory cavities), pattern of anticlinal walls of epidermal cells (primary sculpturing), occurrence of epicuticular striae and folds (secondary sculpturing) and presence of peristomatal folds. An analytical key based on these characteristics is presented for the Eugenia species studied.     

Structure and development of the elaiosome in Myrtus communis L. (Myrtaceae) seeds

Myrtus communis L. (Myrtaceae) is a fleshy-fruited shrub occurring in the Mediterranean area, whose seeds are snail shaped, with a very thick coat and a central elaiosome. This structure is a fleshy and edible appendage responsible of seed dispersal by ants, a phenomenon known as myrmecochory. The elaiosome develops very early from the external integument cells near the funicular and micropylar area, through cell enlargement and cell divisions. At the latest stages of development, some internal integument cells participate to its formation so that myrtle elaiosome can be classified among those originating from both epidermal and inner tissues.The low content of lipids, starch and proteins revealed by histochemical and biochemical analyses on M. communis elaiosomes suggests that the myrtle is a plant with a multiple pattern of seed dispersal. Myrmecochory seems to play a secondary role.     

Population genetic analysis and phylogeny reconstruction in Eucalyptus (Myrtaceae) using high-throughput, genome-wide genotyping

A set of over 8000 Diversity Arrays Technology (DArT) markers was tested for its utility in high-resolution population and phylogenetic studies across a range of Eucalyptus taxa. Small-scale population studies of Eucalyptus camaldulensis, Eucalyptus cladocalyx, Eucalyptus globulus, Eucalyptus grandis, Eucalyptus nitens, Eucalyptus pilularis and Eucalyptus urophylla demonstrated the potential of genome-wide genotyping with DArT markers to differentiate species, to identify interspecific hybrids and to resolve biogeographic disjunctions within species. The population genetic studies resolved geographically partitioned clusters in E. camaldulensis, E. cladocalyx, E. globulus and E. urophylla that were congruent with previous molecular studies. A phylogenetic study of 94 eucalypt species provided results that were largely congruent with traditional taxonomy and ITS-based phylogenies, but provided more resolution within major clades than had been obtained previously. Ascertainment bias (the bias introduced in a phylogeny from using markers developed in a small sample of the taxa that are being studied) was not detected. DArT offers an unprecedented level of resolution for population genetic, phylogenetic and evolutionary studies across the full range of Eucalyptus species.     

Analysis of hybridization between Eucalyptus pauciflora Sieber ex Spreng. and E. radiata Sieber ex DC. (Myrtaceae)

Eucalyptus is a large genus in which hybridization may produce populations which present taxonomic difficulties. A small group of plants, apparently morphologically intermediate between Eucalyptus pauciflora and E. radiata, was studied in an attempt to determine whether hybridization was occurring, and to investigate the use of different techniques of analysis (morphological, chemical and numerical). Taken as a whole, the data from adult and seedling morphology, flavonoid composition, and volatile oil composition of the plants studied prove that they are indeed hybrids between the two species of Eucalyptus; however, these data also indicate some interesting problems in the application of some of these techniques to this particular situation.     

Pistil Structure and Pollen Tube Pathways in Leptospermum myrsinoides and L. continentale (Myrtaceae)

Pistil structure and pollen tube growth were investigated inLeptospermum myrsinoides and L. continentale (Myrtaceae). BothL. myrsinoides and L. continentale pistils consist of an ovarywith five locules, a style and a five-lobed dry, papillate stigma.A centrally located stigmatic cleft is present but extends onlyto the base of the stigma. Pollen germinates and grows intercellularlythrough the stigma into the central transmitting tissue of thestyle. Pollen tubes do not grow down the stigmatic cleft. Atthe base of the style the transmitting tissue separates intofive, each tract leading through the placenta to one of thefive locules. The pollen tubes continue to grow intercellularlythrough these five tracts entering the locules between the lobesof the placenta. Pollen tubes are smooth-walled and straightwhilst in the transmitting tissue of the style but produce shortlateral branches at regular intervals when in the locules. Branchingcontinues until pollen tubes enter ovules. It is suggested thatthe observed branching in the locules is a result of pollentubes following a chemotropic or thigmotropic pathway to theovules. This behaviour was consistent in all pistils examinedand no difference was observed in the behaviour of self- orcross-pollen tubes in the style or ovary.Copyright 1994, 1999Academic Press Leptospermum myrsinoides Schldl., Leptospermum continentale J. Thompson, pistil structure, pollen tube pathway, pollen tube branching     

Eucalyptus regnans (Myrtaceae): A fire-sensitive eucalypt with a resprouter epicormic structure

Determining the location of buds and bud-forming meristems and hence the level of protection from heat is essential to understanding plant response to fire. Most eucalypts resprout readily from the stem (epicormic resprouting) and the base after felling or high intensity fire. In contrast, Eucalyptus regnans is one of the few eastern Australian fire-sensitive, obligate seeder eucalypts. Some authors have suggested that the relatively weak epicormic resprouting is due to a lack of bud-forming structures. Epicormic strands from the bark and outer xylem of three very large trees and two saplings were examined anatomically. Epicormic bud-forming structures were found in all samples examined. The bud-forming capacity consisted of narrow, radially elongated strips of cells of meristematic appearance. These strips were continuous from the outermost secondary xylem through to the outer bark. Bark was relatively thick at the base of the large trees, but remarkably thin above this basal skirt. Eucalyptus regnans was found to possess the apparently fire-adapted epicormic strands previously described in other eucalypts, thus showing its fire-adapted lineage. However, this fire-sensitive species apparently directs much of its resources to rapid height-growth rates in younger trees, rather than to vegetative fire survival.     

A new species of Psidium L. (Myrtaceae) from southern Brazil

Rewardless kettle‐trap flowers Cypripedium yunnanense and C. flavum were watched for pollinators during 73 and 101 man‐hours, respectively, in north‐west Yunnan at 3490–3590 m a.s.l. They differ from typical Cypripedium, such as C. calceolus, in having a broad infolded flap of the lip extending all around the entrance of the pouch (instead of being restricted to the vicinity of the staminode) and in the flap not being slippery. Cypripedium yunnanense is pollinated by Lasioglossum zonulum euronotum (Halictidae), and C. flavum is pollinated by Andrena orchidea and Andrena sp. (Andrenidae, two of nine new hymenopterans discovered at the sites). The bees do not inadvertently fall into the trap by slipping (as often occurs in other slipper orchids), but enter it by crawling down the flap in full control of their movements. No natural hybrids between the two orchids are known, although they occur in close‐by or mixed stands, are co‐flowering and size compatible with regard to their pollinators, and produce fruits following manual cross‐pollination in situ. Analyses of the (non‐Cypripedium) pollen carried indicate that: (1) the two andrenids are probably oligolectic; (2) the andrenids and the halictid do not share the same flower species; and (3) the halictid is polylectic. Points (1) and (2) are probable reasons for the lack of hybrids. The other reason why Lasioglossum zonulum euronotum does not visit C. flavum despite being polylectic may be the flower's odour; cases of discrimination of closely related flowers by polylectic Lasioglossum have been reported elsewhere. Blow flies Calliphora vomitoria and Calliphora pattoni (Calliphoridae) also enter the orchids, some smearing themselves with pollen, yet they are not pollinators. They are too large to leave by the exit and die imprisoned. However, they may be accidental pollinators of the rather larger C. tibeticum present at the sites. Such accidental pollinators probably play an important role in the evolution of new pollination syndromes. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 156 , 51–64.     

Foliar Essential Oil Glands of Eucalyptus Subgenus Eucalyptus (Myrtaceae) Are a Rich Source of Flavonoids and Related Non-Volatile Constituents

The sub-dermal secretory cavities (glands) embedded within the leaves of Eucalyptus (Myrtaceae) were once thought to be the exclusive repositories of monoterpene and sesquiterpene oils. Recent research has debunked this theory and shown that abundant non-volatile compounds also occur within foliar glands. In particular, glands of four species in subgenus Eucalyptus contain the biologically active flavanone pinocembrin. Pinocembrin shows great promise as a pharmaceutical and is predominantly plant-sourced, so Eucalyptus could be a potential commercial source of such compounds. To explore this we quantified and assessed the purity of pinocembrin in glands of 11 species of E. subg. Eucalyptus using Electro-Spray Ionisation Liquid Chromatography Mass Spectrometry of acetonitrile extracts and Gas Chromatography Mass Spectrometry analyses of hexane extracts of isolated glands which were free from other leaf tissues. Our results showed that the glands of subgenus Eucalyptus contain numerous flavanones that are structurally related to pinocembrin and often present in much greater abundance. The maximum concentration of pinocembrin was 2 mg g^-1 dry leaf found in E. stellulata, whereas that of dimethylpinocembrin (5,7-dimethoxyflavanone) was 10 mg g^-1 in E. oreades and that of pinostrobin (5-hydroxy-7-methoxyflavanone) was 12 mg g^-1 in E. nitida. We also found that the flavanones are exclusively located within the foliar glands rather than distributed throughout leaf tissues. The flavanones differ from the non-methylated pinocembrin in the degree and positions of methylation. This finding is particularly important given the attractiveness of methylated flavonoids as pharmaceuticals and therapeutics. Another important finding was that glands of some members of the subgenus also contain flavanone O-glucosides and flavanone-β-triketone conjugates. In addition, glands contain free β-triketones, β-triketone heterodimers and chromone C-glucosides. Therefore, the foliar glands of this taxonomically distinct group of plants are a rich source of a range of flavonoids and other biologically active compounds with great commercial potential.     

Biology of the Eucalyptus leaf beetle Paropsisterna selmani (Chrysomelidae: Paropsini): a new pest of Eucalyptus species (Myrtaceae) in Ireland

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