Cytogenetic studies of Haplopappus gracilis in both callus and suspension cell cultures

Summary Investigations have been carried out on karyotype change in both callus and suspension cell cultures of Haplopappus gracilis (2n=4). It has been found that polyploidization arises directly in culture to give up to six times the normal diploid chromosome number in some cultures. In polyploid cultures, both chromosome loss and chromosome rearrangements occur to give rise to aneuploid karyotypes displaying chromosomes which differ in morphology from the diploid set. Whole or partial chromosome loss has been observed in the form of lagging chromosomes and chromosome bridges at anaphase, and micronuclei, ring chromosomes and chromosome fragments at other stages in mitosis. C-banded preparations have confirmed the occurrence of chromosomal rearrangements. Comparative investigations suggest that (i) more polyploidy occurs in callus cultures than in suspension cell cultures, and (ii) the presence of cytokinin (kinetin) in the culture medium may reduce the extent of karyotype change.     

Magnesium and Manganese Content of Halophilic Bacteria

Magnesium and manganese contents were measured by atomic absorption spectrophotometry in bacteria of several halophilic levels, in Vibrio costicola, a moderately halophilic eubacterium growing in 1 M NaCl, Halobacterium volcanii, a halophilic archaebacterium growing in 2.5 M NaCl, Halobacterium cutirubrum, an extremely halophilic archaebacterium growing in 4 M NaCl, and Escherichia coli, a nonhalophilic eubacterium growing in 0.17 M NaCl. Magnesium and manganese contents varied with the growth phase, being maximal at the early log phase. Magnesium and manganese molalities in cell water were shown to increase with the halophilic character of the logarithmically growing bacteria, from 30 mmol of Mg per kg of cell water and 0.37 mmol of Mn per kg of cell water for E. coli to 102 mmol of Mg per kg of cell water and 1.6 mmol of Mn per kg of cell water for H. cutirubrum. The intracellular concentrations of manganese were determined independently by a radioactive tracer technique in V. costicola and H. volcanii. The values obtained by ⁵⁴Mn loading represented about 70% of the values obtained by atomic absorption. The increase of magnesium and manganese contents associated with the halophilic character of the bacteria suggests that manganese and magnesium play a role in haloadaptation.     

Population modelling and genetics of a critically endangered Madagascan palm Tahina spectabilis

Madagascar is home to 208 indigenous palm species, almost all of them endemic and >80% of which are endangered. We undertook complete population census and sampling for genetic analysis of a relatively recently discovered giant fan palm, the Critically Endangered Tahina spectablis in 2008 and 2016. Our 2016 study included newly discovered populations and added to our genetic study. We incorporated these new populations into species distribution niche model (SDM) and projected these onto maps of the region. We developed population matrix models based on observed demographic data to model population change and predict the species vulnerability to extinction by undertaking population viability analysis (PVA). We investigated the potential conservation value of reintroduced planted populations within the species potential suitable habitat. We found that the population studied in 2008 had grown in size due to seedling regeneration but had declined in the number of reproductively mature plants, and we were able to estimate that the species reproduces and dies after approximately 70 years. Our models suggest that if the habitat where it resides continues to be protected the species is unlikely to go extinct due to inherent population decline and that it will likely experience significant population growth after approximately 80 years due to the reproductive and life cycle attributes of the species. The newly discovered populations contain more genetic diversity than the first discovered southern population which is genetically depauperate. The species appears to demonstrate a pattern of dispersal leading to isolated founder plants which may eventually lead to population development depending on local establishment opportunities. The conservation efforts currently put in place including the reintroduction of plants within the species potential suitable habitat if maintained are thought likely to enable the species to sustain itself but it remains vulnerable to anthropogenic impacts.     

Comparison of the population genetics and densities of five pinanga palm species at kuala belalong, brunei

This study investigated the effect of population density on the population genetic structure of five co-occurring congeneric understorey palm species: Pinanga aristata, P. sp. aff. brevipes, P. dumetosa, P. tenella var. tenella and P. veitchii, all endemic to northern Borneo. The average population densities of the study species varied across a wide spectrum, ranging from 343 (plants per ha) in P. tenella to 10 (plants per ha) in P. veitchii. All species of Pinanga palms studied had quite high levels of genetic diversity (HE: 0.379, 0.256, 0.294, 0.133, 0.352). Genetic diversity (HE) was correlated with population density (D; rs = - 0.433, P < 0.01) and the average distance to the nearest conspecific neighbour (NN; rs = 0.576, P < 0.001) such that the most-dense species had less genetic diversity and the less-dense species had greater genetic diversity. Gene flow (Nm) among populations approximately followed a gradient of increasing species density and abundance, such that the most common species P. dumestosa had the greatest gene flow (Nm = 2.268) between its populations and the rarest, most sparsely distributed species P. sp. aff. brevipes had the lowest (Nm = 0.698). All species of Pinanga were effectively inbred (F: 0.760, 0.856, 0.640, 0.753, 0.674). The amount of homozygosity and inbreeding (HO, F) were not correlated (P > 0.05) with population density (D) or the distance between nearest neighbouring plants of the same species (NN).     

The OJIP fast fluorescence rise characterizes Graptophyllum species and their stress responses

Causes for rarity in plants are poorly understood. Graptophyllum reticulatum is an endangered endemic species, and it has three close relatives with different conservation status: the vulnerable G. ilicifolium, the rare G. excelsum, and the common G. spinigerum. Applied to the chlorophyll a fluorescence transient of leaves, the JIP test provides a Performance Index (PI) which quantifies the main steps in photosystem II (PSII) photochemistry including light energy absorption, excitation energy trapping, and conversion of excitation energy into electron flow. The PI is calculated from three components which depend on the reaction center density, the trapping efficiency, and the electron transport efficiency. PI was measured in the natural habitats of the four species and under artificially imposed environmental stresses in the glasshouse to determine whether conservation status was related to stress resilience. The results showed that soil type is unlikely to restrict the endangered G. reticulatum, vulnerable G. ilicifolium, or rare G. excelsum because PI was similar in plants grown in diverse soils in the glasshouse. Photoinhibition is likely to restrict the endangered G. reticulatum to shade habitats because PI was significantly reduced when plants were exposed to more than 15% ambient light in controlled experiments. Water availability may determine the location and distribution of the vulnerable G. ilicifolium and common G. spinigerum because PI was reduced more than 60% when plants were exposed to water stress. While the characteristics of their natural habitats correspond to and explain the physiological responses, there was no obvious relationship between conservation status and environmental resilience. PI can be used to monitor vigor and health of populations of plants in the natural habitat. In cultivation experiments PI responds to key environmental variables that affect the distribution of species with conservation significance.     

Conservation genetics and ecology of an endemic montane palm on Lord Howe Island and its potential for resilience

Lepidorrhachis mooreana (Arecaceae) is a monotypic palm genus endemic to the remote Lord Howe Island where it is restricted to a small area of cloud forest above 750 m that is likely to be vulnerable to climate change. We investigated genetic diversity and key demographic parameters to assess the palm’s potential long term viability including possible climate change impacts. The palm was found on only one of the island’s two mountain summits, where the sampled sites were effectively behaving as one panmictic population. The moderate genetic diversity found indicates some adaptive potential for L. mooreana. The population was effectively inbred. Large numbers of fruit are produced, but successful juvenile recruitment is limited by predation by introduced rats. The relatively large population size increases the potential for selection for adaptation to a changing climate.     

Vagility and the Monsoon Rain Forest Archipelago of Northern Australia: Patterns of Genetic Diversity in Syzygium nervosum (Myrtaceae)1

Syzygium nervosum is a common monsoon rain forest tree. Its habitat in Australia consists of small rain forest patches that are scattered through a savanna matrix. It is a mast flowering canopy species that produces large quantities of fruits fed on by mobile frugivores such as birds and fruit bats. The genetic diversity of this species was investigated, especially in relation to rain forest patch size, geographic isolation, and geographic distribution. Syzygium nervosum was found to have high levels of genetic diversity within populations (H_e= 0.307). Diversity among populations, however, was relatively low (Fsr = 0.118), and was not spatially structured across its geographic range in Australia. This is thought to have been caused by relatively frequent gene flow among populations (N_m= 1.67), mediated primarily by mobile frugivores. Genetic diversity was not correlated with patch size or isolation. It is thought that seed dispersal by frugivores has acted to expand the effective population size of this species beyond the individual rain forest patch, and thus has prevented the substantial loss of genetic diversity that otherwise would have been observed. Thus this species is dependent upon these frugivores for the maintenance of its genetic diversity and hence its long-term viability. These results lend support to theories of post-Holocene expansion of rain forest by vagile species in northern Australia.     

Fragmentation and Genetic Diversity in Romnalda (Dasypogonaceae), a Rare Rain forest Herbaceous Genus from New Guinea and Australia

Rain forests are expected to be amongst the ecosystem types most affected by fragmentation due to their high species diversity, high endemism, complexity of interactions, and contrast with surrounding altered matrix. Due to their shorter life cycles and dependence on canopy cover, rain forest understory herbs are expected to indicate the effects of recent fragmentation more rapidly than canopy trees. This study investigated all four known species of the genus Romnalda , all of which are rare rain forest herbaceous species, to investigate the possible effects of habitat fragmentation and isolation on genetic diversity and gene flow. Allozymes were used as genetic markers and regional remnant vegetation maps were used to compare landscape fragmentation. We found that R. strobilacea populations in a highly fragmented landscape were genetically depauperate compared with those of its congeneric species that are found within continuous rain forest habitats and that allelic diversity decreased with decreasing population size but not geographic distance in R. strobilacea . Given the similarity among the species, our results indicate that all Romnalda species are potentially susceptible to loss of genetic diversity due to habitat fragmentation within relatively short timeframes. The results indicate that populations are not highly genetically differentiated and there is little evidence of genetic provenance where the species have restricted geographic ranges. Thus, species recovery programs would be better to focus on maintaining population size and genetic diversity rather than population differentiation.     

Low genetic diversity and recovery implications of the vulnerable Bankoualé Palm Livistona carinensis (Arecaceae), from North-eastern Africa and the Southern Arabian Peninsula

The Bankoualé Palm, Livistona carinensis is the only known species of Livistona occurring in Africa and is currently classified as vulnerable (IUCN 2004). This extreme outlier species of the genus is restricted to Yemen, Somalia and Djibouti, where all populations are in rapid decline. In Djibouti the palm is confined to three valley systems within the upland plateau of the Goda Massif. This study used microsatellite markers to investigate the genetic diversity and relationships within the species. At the species level L. carinensis contained very low genetic diversity. Most variation was due to the variation between the samples from Yemen and Somalia compared with those in Djibouti. The Djibouti populations were almost monomorphic across the nine loci tested. Interestingly, and despite the small sample sizes, the individuals from botanic gardens collections of the Yemen and Somalia populations were more genetically diverse than the Djibouti populations. This study indicates that the populations in Yemen and Somalia are highly significant for the conservation of the species genetic diversity. Given the lack of genetic diversity both within and among L. carinensis populations in Djibouti, plants could be cultivated for in-situ population enhancement from any seed that is available from within Djibouti with no significant genetic impacts of provenance mismatch. Clearly the populations from Djibouti, Somalia and Yemen are different genetic provenances raising some issues for the conservation and recovery of L. carinensis.     

Mapping Biodiversity and Setting Conservation Priorities for SE Queensland’s Rainforests Using DNA Barcoding

Australian rainforests have been fragmented due to past climatic changes and more recently landscape change as a result of clearing for agriculture and urban spread. The subtropical rainforests of South Eastern Queensland are significantly more fragmented than the tropical World Heritage listed northern rainforests and are subject to much greater human population pressures. The Australian rainforest flora is relatively taxonomically rich at the family level, but less so at the species level. Current methods to assess biodiversity based on species numbers fail to adequately capture this richness at higher taxonomic levels. We developed a DNA barcode library for the SE Queensland rainforest flora to support a methodology for biodiversity assessment that incorporates both taxonomic diversity and phylogenetic relationships. We placed our SE Queensland phylogeny based on a three marker DNA barcode within a larger international rainforest barcode library and used this to calculate phylogenetic diversity (PD). We compared phylo- diversity measures, species composition and richness and ecosystem diversity of the SE Queensland rainforest estate to identify which bio subregions contain the greatest rainforest biodiversity, subregion relationships and their level of protection. We identified areas of highest conservation priority. Diversity was not correlated with rainforest area in SE Queensland subregions but PD was correlated with both the percent of the subregion occupied by rainforest and the diversity of regional ecosystems (RE) present. The patterns of species diversity and phylogenetic diversity suggest a strong influence of historical biogeography. Some subregions contain significantly more PD than expected by chance, consistent with the concept of refugia, while others were significantly phylogenetically clustered, consistent with recent range expansions.