Cycad Macrozamia Research Articles

First record of the tribe Oecleini in Australia (Hemiptera: Auchenorrhyncha: Fulgoromorpha: Cixiidae) with the description of a new genus and species

A new genus and species, Apollo maculiceps gen. & sp. nov., in the planthopper family Cixiidae is described from south Western Australia. It can be distinguished from all other Australian Cixiidae by the presence of a denticle on the distal part of the fore coxa, a character that is shared with some other Oecleini genera. Large numbers of Apollo maculiceps gen. & sp. nov. were observed feeding on a native Australian cycad Macrozamia riedlei (family Zamiaceae). This is the first record of the economically important tribe Oecleini from Australia. A revised key to the tribes of the Australian Cixiidae is presented.

Cycad killer, qu'est-ce que c'est? Dieback of Macrozamia communis on the south coast of New South Wales

The association of an armoured scale insect (a diaspidid) with dieback of a population of a native cycad (Macrozamia communis L.A.S.Johnson) was investigated on the south coast of New South Wales. The diaspidid was found to be undescribed but morphologically similar to oleander scale – here we call it Aspidiotus cf. nerii. It is probably native to Australasia and its current known distribution is within Murramarang National Park (MNP). Aspidiotus cf. nerii has been abundant on symptomatic M. communis at MNP over at least the past decade and has spread to new parts of the park. In population studies of infested and uninfested areas we found that, although both areas had populations with reverse J curves showing dominance of seedlings, mortality of seedlings and caulescent plants was significantly higher in infested sites. Infested areas had been burnt less frequently than uninfested areas. Fire does not appear to eradicate the diaspidid but may reduce its effects enough for plants to recover. We recommend further research into the use of fire as a management tool. Although other factors may be contributing to the severity of the dieback, we suggest there is sufficient evidence for the diaspidid to be regarded as the primary cause of dieback in M. communis in MNP, regardless of its origin. Given the occurrence of similar diaspidids on cultivated plants in botanic gardens, translocation of threatened Macrozamia species using plants grown in nurseries should be undertaken with extreme caution.

Beetle Pollination of Cycads in the Mesozoic

Cycads, unlike modern wind-pollinated conifers and Ginkgo, are unusual in that they are an ancient group of gymnosperms pollinated by insects [1-3]. Although it is well documented that cycads were diverse and abundant during the mid-Mesozoic, little is known about their biogeography and pollination before the rise of angiosperms. Direct fossil evidence illuminating the evolutionary history of cycads is extremely rare [4, 5]. Here we report a specialized beetle-mediated pollination mode from the mid-Cretaceous of Myanmar, wherein a new boganiid beetle, Cretoparacucujus cycadophilus, with specialized pollen-feeding adaptations in its mouthparts and legs, was associated with many pollen grains of Cycadopites. Phylogenetic analyses indicate Cretoparacucujus as a sister group to the extant Australian Paracucujus, which pollinate the cycad Macrozamia riedlei. Our discovery, along with the current disjunct distribution of related beetle-herbivore (tribe Paracucujini) and cycad-host (tribe Encephalarteae) pairs in South Africa and Australia, indicate a probable ancient origin of beetle pollination of cycads at least in the Early Jurassic, long before angiosperm dominance and the radiation of flowering-plant pollinators later in the Cretaceous.

Determining maturity and population structure in Macrozamia parcifolia (Zamiaceae), a threatened Australian cycad

There is difficulty assigning maturity to non-arborescent (trunkless) cycad species and as a consequence in determining the mature–immature structure of populations, which is important for their management, particularly for those under threat. The aim of this investigation was to find a reliable and simple method to determine maturity for the threatened, non-arborescent cycad Macrozamia parcifolia P.I. Forst. & D.L. Jones, and to incorporate this information into a population structure. Measurements were taken from tagged plants on four quadrats in eucalypt-dominated open forest in south-eastern Queensland, Australia. Using a single time-point dataset of three variables associated with the longest mature leaf, basal petiole width coupled with several years of coning evidence was found best at distinguishing mature plants. Choice of this variable and the threshold point to class non-coning plants as mature or immature was through a classification-tree model using a binary recursive partitioning process, the tree being pruned to identify the best variable and threshold point via a cross-validation process. This simple, reliable method to determine maturity was still effective when using a single time-point dataset for coning evidence. The method can be applied to other threatened, non-arborescent cycads, which could aid in their conservation management. The structure of M. parcifolia population was bimodal. The mode that encompassed immature plants was broadly reverse-J shaped, indicating younger immature plants had highest mortality. Reasons for the bimodality are possibly complex, but could simply highlight a non-lineal relationship of basal petiole width with plant age.

Anything more than a picnic? Re‐considering arguments for ceremonial Macrozamia use in mid‐Holocene Australia

AbstractInfluential arguments have been advanced in Australian archaeology concerning the origins and development of social and economic change in the mid‐late Holocene (Lourandos 1997). One example used to support this claim is the perceived existence of ceremonial feasting events held in the semi‐arid and rugged sandstone gorge systems of central Queensland, attended by large groups of people for extended periods, and underwritten by large quantities of kernels from the cycad Macrozamia moorei (Beaton 1977, 1982; see also Lourandos 1997). However the re‐examination of the macrobotanical evidence from archaeological sites in this region using taphonomic analysis, replicative processing experiments, recalculations of seed density and estimations of the minimum numbers of seeds, does not support this model. This re‐examination questions the role of Macrozamia seeds in the context of socio‐economic change and suggests new interpretations of Macrozamia resource use.

Respiration and thermogenesis by cones of the Australian cycad Macrozamia machinii

Summary While cycads are often considered to be wind‐pollinated, it is now clear that insects are pollen vectors in many species. This study addresses the role of thermogenesis in pollination biology of the dioecious cycad Macrozamia machinii P.I. Forster & D.L. Jones. The patterns of thermogenesis in intact male and female cones were assessed with thermometry and respirometry throughout the pollination period in the field. Thermogenic episodes in male cones occurred from about 17.00–00.00 h on successive evenings, in association with dehiscence of sporangia and presence of their pollinating weevils (Tranes sp.). Temperatures of the 167 g male cones rose ≈6 °C above ambient, and mean rate of oxygen consumption peaked at 7·7 µmol s−1 (3·6 W). Regulation of male cone temperature was not evident, and thermogenesis of female cones was insignificant. Male cones probably heat to augment scent production and enhance weevil activity, including mating and egg‐laying, but female cones may benefit from reduced visitation and freedom from damage by weevil larvae. Male cones may be sacrificial in providing the reward to the pollinators while the female cones are safeguarded.

Sequence based data supports a single Nostoc strain in individual coralloid roots of cycads

The genetic diversity of cyanobacteria associated with cycads was examined using the tRNA Leu (UAA) intron as a genetic marker. Coralloid roots of both natural populations of the cycad Macrozamia riedlei (Fischer ex Gaudichaud-Beaupré) C.A. Gardner growing in Perth, Australia and cycads growing in greenhouses, also in Perth, were used and their respective cyanobionts analyzed. Several Nostoc strains were found to be involved in this symbiosis, both in natural populations and greenhouse-originated cycads. However, only one strain was present in individual coralloid roots and in individual plants, even when analyzing different coralloid roots from the same plant. Moreover, when examining plants growing close to each other (female plants and their respective offspring) the same cyanobacterium was consistently present in the different coralloid roots. Whether this reflects a selective mechanisms or merely the availability of Nostoc strains remains to be ascertained. The high cyanobacterial diversity in coralloid roots of cycads revealed by PCR fingerprinting is, therefore, contested. In this study, the potential problems of using different methods (e.g., PCR fingerprinting) to study the genetic diversity of symbiotic cyanobacteria, is also addressed.

Sequence based data supports single Nostoc strain in individual coralloid roots of cycads

The genetic diversity of cyanobacteria associated with cycads was examined using the tRNA Leu (UAA) intron as a genetic marker. Coralloid roots of both natural populations of the cycad Macrozamia riedlei (Fischer ex Gaudichaud-Beaupré) C.A. Gardner growing in Perth, Australia and cycads growing in greenhouses, also in Perth, were used and their respective cyanobionts analyzed. Several Nostoc strains were found to be involved in this symbiosis, both in natural populations and greenhouse-originated cycads. However, only one strain was present in individual coralloid roots and in individual plants, even when analyzing different coralloid roots from the same plant. Moreover, when examining plants growing close to each other (female plants and their respective offspring) the same cyanobacterium was consistently present in the different coralloid roots. Whether this reflects a selective mechanisms or merely the availability of Nostoc strains remains to be ascertained. The high cyanobacterial diversity in coralloid roots of cycads revealed by PCR fingerprinting is, therefore, contested. In this study, the potential problems of using different methods (e.g., PCR fingerprinting) to study the genetic diversity of symbiotic cyanobacteria, is also addressed.

Reconstitution of the symbiosis of Gunnera manicata Linden: cyanobacterial specificity

SUMMARYThe ability of various cyanobacteria to establish a symbiosis with Gunnera manicata Linden was examined under sterile conditions. Cyanobacterial strains were classified as infective if they could be found in a well‐defined infected area within the Gunnera gland tissue 40 d after inoculation. Nine out of 17 tested Nostoc strains were able to infect G. manicata. The infecting strains were all symbiotic isolates. These included six out of ten isolates from Gunnera spp., the isolate from the cycad Macrozamia sp., that from the hornwort Anthocerns sp., and that from the lichen Peltigera canina. None of the seven strains belonging to genera other than Nostne was capable of infection, even though the majority of them were also able to form motile hormogonia. Negative staining revealed fimbria‐like structures in both infective and non‐infective strains. In fact, two of the non‐infecting strains had the most abundant fimbria‐like filaments. No conspicuous structural or ultrastructural differences between infecting and non‐infecting strains were detected using light‐ and transmission electron microscopy. We conclude that selection between conceivable microsymbionts is exerted at the recognition and/or entrance stage.

Ornithine cycle in Nostoc PCC 73102. Arginase, OCT and arginine deiminase, and the effects of addition of external arginine, ornithine, or citrulline

Arginase, ornithine carbamoyl transferase (OCT) and arginine deiminase activities were found in cell-free extracts of Nostoc PCC 73102, a free-living cyanobacterium originally isolated from the cycad Macrozamia. Addition of either arginine, ornithine or citrulline to the growth medium induced significant changes in their in vitro activities. Moreover, growth in darkness, compared to in light, induced higher in vitro activities. The in vitro activities of arginase and arginine deiminase, two catabolic enzymes primarily involved in the breakdown of arginine, increased substantially by a combination of growth in darkness and addition of either arginine, or ornithine, to the growth medium. The most significant effects on the in vitro OCT activities where observed in cells grown with the addition of ornithine. Cells grown in darkness exhibited about 6% of the in vivo nitrogenase activity observed in cells grown in light. However, addition of external carbon (glucose and fructose) to cells grown in darkness resulted in in vivo nitrogenase activity levels similar to, or even higher than, cells grown in light. Growth with high in vivo nitrogenase activity or in darkness with the addition of external carbon, resulted in repressed levels of in vitro arginase and arginine deiminase activities. It is suggested that nitrogen starvation induces a mobilization of the stored nitrogen, internal release of the amino compound arginine, and an induction of two catabolic enzymes arginase and arginine deiminase. A similar and even more pronunced induction can be observed by addition of external arginine to the growth medium.

Ornithine cycle in Nostoc PCC 73102. Occurrence and localization of ornithine carbamoyl transferase, and the effects of external carbon and ornithine on nitrogenase activity and citrulline synthesis

Cells of free‐living nitrogen‐fixing Nostoc PCC 73102, a filamentous heterocystous cyanobacterium originally isolated from coralloid roots of the cycad Macrozamia. were examined for the presence of ornithine carbamoyl transferase (OCT) by native‐PAGE/in situ activity stain, and SDS‐PAGE/Western immunoblots. Transmission electron microscopy and immunocytological labeling were used to study the cellular and subcellular distribution of OCT in the Nostoc cells. Moreover, the effects of photoautotrophic and dark heterotrophic growth metabolism on growth, nitrogenase activity and in vivo citrulline synthesis were investigated. PAGE in combination with in situ activity staining demonstrated an in vitro active OCT with a molecular weight of approximately 80 kDa. SDS‐PAGE/Western immunoblots revealed that a polypeptide with a molecular weight of approximately 38 kDa was immunologically related to OCT purified from pea (Pisum sativum L. cv. Alaska). Immunolocalization demonstrated that the OCT protein was located both in vegetative cells and heterocysts. Using the particle analysis of an image processor, the labeling associated with the photosynthetic vegetative cells was calculated to be 75.6 (± 5.5) gold particles μm−2 compared with 62.0 (± 7.5) in the nitrogen‐fixing heterocysts. Glucose and fructose stimulated both cyanobacterial growth and nitrogenase activity in light and darkness. Addition of exogenous ornithine decreased nitrogenase activity. In light grown cells, additions of glucose and fructose in combination with ornithine not only stimulated growth and nitrogenase activity but also in vivo citrulline synthesis, measured as 14CO2‐fixation into [14C]‐citrulline. In darkness no stimulation was observed on in vivo citrulline synthesis. The substantial stimulation of nitrogenase activity by additions of external glucose and fructose, both in the light and in darkness, was not followed by a simultaneous stimulation of in vivo citrulline synthesis.

The first thrips species (Insecta, Thysanoptera) from cycad male cones, and its family level significance

A new genus and species of Thysanoptera: Aeolothripidae, Cycadothrips chadwicki, is described, collected from within the male cones of the cycad Macrozamia communis in Australia. This is the first published record of a member of this Order of insects from this family of Gymnosperms, but its relationship to these plants remains unknown. Details of the structure of the antennae and seventh abdominal segment suggest that the species is not closely related to any known member of the family Aeolothripidae, and so a new sub-family name is proposed.

Coning Phenology of the Cycad Macrozamia riedlei (Zamiaceae) Over a Five- Year Interval

ORNDuFF, R. (Department of Integrative Biology, University of California, Berkeley, CA 94720). Coning phenology ofthe cycad Macrozamia riedlei (Zamiaceae) over a five-year interval. Bull. Torrey Bot. Club 118: 6-11. 1991.-Phenotypic sex ratios and estimates of coning frequencies of seven populations of the Western Australian cycad Macrozamia riedlei (Fisch. ex Gaud.) C. A. Gardner have been published based on fieldwork conducted in 1983. These populations, plus two additional ones, were sampled five years later for the same traits. In addition, size classes were determined for known males, females, and plants of unknown sex, cone numbers of males and females with 1988 cones were determined, and insects associated with male cones shedding pollen were collected and identified. Of the five populations with males and females having 1983 cones, three had no individuals of either sex with 1988 cones, one had males but no females with 1988 cones, and one had males and females with 1988 cones. Two additional populations with no 1983 cones also had no 1988 cones, although these had evidence of very low levels of cone production in the intervening period. One population with a male-biased phenotypic sex ratio in 1983 had a 1:1 male: female sex ratio in 1988; two populations not sampled in 1983 had a male bias and a 1:1 phenotypic sex ratio, respectively. For the two sampling periods, a male bias prevails. Considerable interpopulation differences were present in average leaf numbers of plants with 1988 cones. Males and females were of equal size within all populations but one, where females had twice the leaf number of males. Plants with cones were larger than plants lacking cones. Cone numbers produced by males equaled those of females except in two populations, where males produced more cones than females. For males, there was no correlation between leaf number and cone number, and in all samples but one this was true for females. In one population of females, leaf number increased with cone number. The two studies support earlier suggestions that males and females of M. riedlei under natural conditions rarely produce cones in successive years, and that males produce cones more frequently than females. The absence of 1988 cones in some populations is attributed to competition and shading effects, but may also be related to the marginal conditions under which these populations grow. Fire appears to stimulate cone production by reducing competition and increasing nitrogen fixation by root-inhabiting Cyanobacteria. The percentage of plants judged to be mature in various populations ranged from 45 to 90 percent. Four species of Coleoptera, two of which are weevils, were collected from male cones shedding pollen, suggesting that insects may play a role in the pollination of this cycad.

Occurrence of azoxyglycosides in Macrozamia riedlei and their effects on the free-living isolated Nostoc PCC 73102

The presence of azoxyglycosides in the Australian cycad Macrozamia reidlei was examined using high performance liquid chromatography. Cycasin and macrozamia were present in all tissues examined, cycasin being three to 17 times more abundant than macrozamin. The symbiotic organ, the coralloid root, contained 0.16% [g/g (fresh weight)] cycasin and 0.01 % (same unit) macrozamin. Addition of these azoxyglycoside concentrations to nitrogen-fixing Nostoc PCC 73102 cultures, a filamentous heterocystous cyanobacterium originally isolated from Macrozia, inhibited light and dark nitrogenase (acetylene reduction) activity. No effects were observed on in vitro glutamine synthetase activity or net in vivo CO 2 fixation. Cycasin (1.6%) and macrozamin (0.1%), i.e. 10 times the concentrations observed in the coralloid root, decreased phycobiliprotein content by 25 and 45%, 1 and 4 hr after the addition, respectively. The relative distribution of individual phycobiliproteins was not affected.

GENETIC STRUCTURE OF THE AUSTRALIAN CYCAD, MACROZAMIA COMMUNIS (ZAMIACEAE)

Cycads have been the subject of a wide variety of botanical studies. However, nothing is known of the genetic structure of their populations. Seeds were collected from five populations of the common Australian cycad Macrozamia communis along a north to south transect through its 500‐km‐long range in eastern New South Wales. Leaf samples from seedlings grown from those seeds were the subject of isozyme analysis. Nine of the 18 isozyme loci studied were polymorphic. Levels of polymorphism varied among loci and among populations. The three southern‐most populations were genetically similar to one another but well differentiated from the other two. The levels of species‐wide genetic diversity observed for M. communis were relatively low compared with those of other gymnosperms and angiosperms. On the other hand, the levels of spatial differentiation were relatively high, especially compared with other gymnosperms.

Genetic Structure of the Australian Cycad, Macrozamia Communis (Zamiaceae)

Cycads have been the subject of a wide variety of botanical studies. However, nothing is known of the genetic structure of their populations. Seeds were collected from five populations of the common Australian cycad Macrozamia communis along a north to south transect through its 500-km-long range in eastern New South Wales. Leaf samples from seedlings grown from those seeds were the subject of isozyme analysis. Nine of the 18 isozyme loci studied were polymorphic. Levels of polymorphism varied among loci and among populations. The three southern-most populations were genetically similar to one another but well differentiated from the other two. The levels of species-wide genetic diversity observed for M. communis were relatively low compared with those of other gymnosperms and angiosperms. On the other hand, the levels of spatial differentiation were relatively high, especially compared with other gymnosperms.

Geographic Variation in Reproductive Behavior and Size Structure of the Australian Cycad Macrozamia communis (Zamiaceae)

Geographic Variation in Reproductive Behavior and Size Structure of the Australian Cycad Macrozamia communis (Zamiaceae)

Sex Ratios and Coning Frequency of the Cycad Zamia pumila L. (Zamiaceae) in the Dominican Republic

In January 1985, features of coning behavior were examined in three populations of the cycad Zamia pumila (Zamiaceae) growing in different environmental conditions in the Dominican Republic. One population exists in a state of semi-cultivation in the relatively open lawns of the National Botanical Garden, Santo Domingo. A second occurs in moderately open areas at the edge of a second-growth forest at Boca Chica, and a third occupies shaded areas under the canopy of a relatively undisturbed forest at Bayahibe. One-third of the botanical garden females bore cones from the current and previous season, whereas only 9 percent of the Boca Chica females showed successive coning and none of the Bayahibe plants did. Four percent of the mature individuals in the botanical garden showed no evidence of coning in either season, whereas one-third and two-thirds of those in the latter two populations, respectively, fell into this non-coning category. The phenotypic sex ratio for the botanical garden and the Boca Chica populations was 1:1. Since nearly all individuals at the first site produced cones and thus were assignable to sex, the genotypic sex ratio of that population was 1:1. A male bias was evident at Bayahibe, where 73 percent of the coning individuals were male. Where environmental conditions are most favorable, the energetically costly female cones appear to be produced more frequently and by a greater proportion of females than where these conditions are less favorable. These environmental differences thus influence the phenotypic sex ratio, which is equality under good to excellent environmental conditions, but male-biased under less favorable environmental conditions under which fewer females than males produce cones each season. DESPITE CONSIDERABLE RECENT INTEREST in the population biology of dioecious seed plants, little attention has been paid to gymnosperms, even though some of these, such as the cycads, show striking sexual dimorphism in their allocation of resources to cones during episodes of sexual reproduction. Of the 75 taxa of seed plants for which published sex ratios were summarized by Willson (1983), only two are gymnosperms (two species of Dacrydium, Podocarpaceae). Since Willson's summary appeared, a study including data on sex ratios and coning frequencies for a population of the New World cycad Zamia pumila L. in Puerto Rico was published by Newell (1983), and another has been published dealing with similar features of the cycad Macrozamia riedlei (Fisch. ex Gaud.) C. A. Gardner in Western Australia (Ornduff 1986). The present paper is concerned with coning behavior and sex ratios in Zamia pumila, and extends observations from the Puerto Rican population studied by Newell to three populations growing under different environmental conditions in the Dominican Republic.

The Hydrogenase-Nitrogenase Relationship in a Symbiotic Cyanobacterium Isolated From Macrozamia communis L. Johnson

The relationship between nitrogenase and hydrogenase activity in the cyanobacterial isolate from the corolloid roots of the cycad Macrozamia communis, grown both photoautotrophically and heterotrophically, has been investigated. The organism actively consumes hydrogen gas in both light and darkness in an oxygen-dependent reaction. The hydrogen consumption was substantially stimulated by light and was nickel-dependent. Nitrogenase activity was found not to be enhanced by hydrogen, either in the dark or light.

Masting, seed dispersal and seed predation in the cycad Macrozamia communis.

Little is known about the adaptive value of mast seeding, a common phenomenon in temperate trees and shrubs. Masting is likely to affect both seed dispersal and seed predation. In systems where similar taxa of animals are involved in these two processes, the consequences of mast seeding are likely to be particularly complicated. This study examined the effects of mast seeding in a cycad, Macrozamia communis, on the dispersal of seeds, the pattern of dispersion of seeds and post-dispersal predation on seeds. Dispersal of seeds by possums was poorer from source plants in a masting population than from source plants in an adjacent, non-masting population. This resulted in fewer seeds per seeding female plant in the masting plot being dispersed to favourable sites. We conclude that this is caused by the feeding behaviour and movements of possums in the masting site. The abundance of seeds in this site did not satiate the post-dispersal predators, native rats. In fact, more seeds in this site were eaten than in the nonmasting site. We suggest that the mast seeding observed in M. communis may not be adaptive, but is more likely a consequence of other factors which synchromize flowering within local populations.