Jocelyn Bowyer

Bio: Jocelyn Bowyer is an academic researcher from Macquarie University. The author has contributed to research in topics: Population bottleneck & Habitat fragmentation. The author has an hindex of 4, co-authored 4 publications receiving 158 citations.

Genetic effects of habitat contraction on Lumholtz's tree-kangaroo (Dendrolagus lumholtzi) in the Australian Wet Tropics

Abstract: Lumholtz’s tree-kangaroo (Dendrolagus lumholtzi) is one of two species of tree-kangaroo resident in the tropical rainforests of north-eastern Australia The species is confined to the Wet Tropics region, with its distribution centred on the Atherton Tablelands While D lumholtzi was exposed to periodic large-scale climatic fluctuations during the Quaternary that have effectively acted as natural fragmentation events, the species is currently under pressure from anthropogenic disturbance and habitat fragmentation This study aimed to assess the level of genetic diversity in D lumholtzi by examining hypervariable microsatellite loci and the control region of mitochondrial DNA (mtDNA) in 21 individuals from a single 20 ha forest fragment, and from a further 24 animals collected throughout the Atherton Tablelands Results suggest that D lumholtzi has relatively low levels of genetic diversity which is uniformly distributed throughout the Atherton Tablelands; a pattern congruent with data from many other vertebrates endemic to the Australian Wet Tropics It is suggested that Pleistocene climatic fluctuations, which resulted in large-scale rainforest contractions, have imposed an ancient population bottleneck on the ancestral D lumholtzi population The apparent over-riding influence of these natural, historical effects on the genetic structure of D lumholtzi populations, will complicate attempts to assess the genetic impact of current anthropogenic habitat loss and fragmentation

Tree-kangaroos Dendrolagus in Australia: are D. lumholtzi and D. bennettianus sister taxa?

Abstract: Tree-kangaroos Dendrolagus sp. are a poorly known group of folivorous arboreal macropodid marsupials endemic to the rainforests of north-eastern Australia and New Guinea. Over the last century there has been little agreement on the relationship between the two Australian species, D. lumholtzi and D. bennettianus. In light of this uncertainty, we undertook a phylogenetics study based on 430 bp of sequence from the mitochondrial DNA gene cytochrome b (cytb). Samples were collected from D. lumholtzi (n = 45) and D. bennettianus (n = 3), as well as representative of six New Guinean Dendrolagus species. Results from distance and parsimony analyses strongly support a sister relationship between the two Australian species. However, D. lumholtzi and D. bennettanius show considerable sequence divergence (5.3%), suggesting that their speciation predates the mid-late Pleistocene. Although inter-relationships amongst New Guinean Dendrolagus were not fully resolved by our preliminary analysis, a number of distinct lin...

Identifying the Dominant Soil Bacterial Taxa in Libraries of 16S rRNA and 16S rRNA Genes

Abstract: From near to far , from here to there , funny things are everywhere. —Dr. Seuss, One Fish Two Fish Red Fish Blue Fish In 1909, H. Joel Conn ([25][1]) expressed the hope that methods would soon be at hand by which the significance of the different bacteria present in any soil could be

Improved culturability of soil bacteria and isolation in pure culture of novel members of the divisions Acidobacteria, Actinobacteria, Proteobacteria, and Verrucomicrobia

Abstract: The culturability of bacteria in the bulk soil of an Australian pasture was investigated by using nutrient broth at 1/100 of its normal concentration (dilute nutrient broth [DNB]) as the growth medium. Three-tube most-probable-number serial dilution culture resulted in a mean viable count that was only 1.4% of the mean microscopically determined total cell count. Plate counts with DNB solidified with agar and with gellan gum resulted in viable counts that were 5.2 and 7.5% of the mean microscopically determined total cell count, respectively. Prior homogenization of the soil sample with an ultrasonic probe increased the viable count obtained by using DNB solidified with gellan gum to 14.1% of the mean microscopically determined cell count. A microscopic examination of the cell aggregates that remained after sonication revealed that the potential CFU count was only 70.4% of the total cell count, due to cells occurring as pairs or in clumps of three or more cells. Staining with SYTO 9 plus propidium iodide indicated that 91.3% of the cells in sonicated soil samples were potentially viable. Together, these findings suggest that the maximum achievable CFU count may be as low as 64.3% of the total cell count. Thirty isolates obtained from plate counting experiments performed with DNB as the growth medium were identified by comparative analysis of partial 16S rRNA gene sequences. A large proportion of these isolates represent the first known isolates of globally distributed groups of soil bacteria belonging to novel lineages within the divisions Actinobacteria, Acidobacteria, Proteobacteria, and Verrucomicrobia.

Responses of soil bacterial and fungal communities to extreme desiccation and rewetting.

Abstract: The microbial response to summer desiccation reflects adaptation strategies, setting the stage for a large rainfall-induced soil CO2 pulse upon rewetting, an important component of the ecosystem carbon budget. In three California annual grasslands, the present (DNA-based) and potentially active (RNA-based) soil bacterial and fungal communities were tracked over a summer season and in response to controlled rewetting of intact soil cores. Phylogenetic marker genes for bacterial (16S) and fungal (28S) RNA and DNA were sequenced, and the abundances of these genes and transcripts were measured. Although bacterial community composition differed among sites, all sites shared a similar response pattern of the present and potentially active bacterial community to dry-down and wet-up. In contrast, the fungal community was not detectably different among sites, and was largely unaffected by dry-down, showing marked resistance to dessication. The potentially active bacterial community changed significantly as summer dry-down progressed, then returned to pre-dry-down composition within several hours of rewetting, displaying spectacular resilience. Upon rewetting, transcript copies of bacterial rpoB genes increased consistently, reflecting rapid activity resumption. Acidobacteria and Actinobacteria were the most abundant phyla present and potentially active, and showed the largest changes in relative abundance. The relative increase (Actinobacteria) and decrease (Acidobacteria) with dry-down, and the reverse responses to rewetting reflected a differential response, which was conserved at the phylum level and consistent across sites. These contrasting desiccation-related bacterial life-strategies suggest that predicted changes in precipitation patterns may affect soil nutrient and carbon cycling by differentially impacting activity patterns of microbial communities.

Laboratory Cultivation of Widespread and Previously Uncultured Soil Bacteria

Abstract: Most soil bacteria belong to family-level phylogenetic groups with few or no known cultivated representatives. We cultured a collection of 350 isolates from soil by using simple solid media in petri dishes. These isolates were assigned to 60 family-level groupings in nine bacterial phyla on the basis of a comparative analysis of their 16S rRNA genes. Ninety-three (27%) of the isolates belonged to 20 as-yet-unnamed family-level groupings, many from poorly studied bacterial classes and phyla. They included members of subdivisions 1, 2, 3, and 4 of the phylum Acidobacteria, subdivision 3 of the phylum Verrucomicrobia, subdivision 1 of the phylum Gemmatimonadetes, and subclasses Acidimicrobidae and Rubrobacteridae of the phylum Actinobacteria. In addition, members of 10 new family-level groupings of subclass Actinobacteridae of the phylum Actinobacteria and classes Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria of the phylum Proteobacteria were obtained. The high degree of phylogenetic novelty and the number of isolates affiliated with so-called unculturable groups show that simple cultivation methods can still be developed further to obtain laboratory cultures of many phylogenetically novel soil bacteria.

Cultivation of globally distributed soil bacteria from phylogenetic lineages previously only detected in cultivation-independent surveys

Abstract: The culturability of microorganisms in a 10 cm core of an Australian pasture soil was investigated using a minimal agar medium with xylan as the growth substrate. Culturability decreased with increasing depth, from a maximum of 19% of the total microscopically countable cells in the 0-2 cm section to 2.4% in the 8-10 cm section. Seventy-one isolates from the core were identified by comparative 16S rRNA gene sequence analysis. Many of these isolates belong to groups of globally distributed soil bacteria, including well-characterized families of the classes Alphaproteobacteria and Betaproteobacteria, and of the subclass Actinobacteridae. Other isolates belong to groups with few or no cultivated representatives: 10 isolates in two subdivisions of the phylum Acidobacteria, five isolates in a new order and nine isolates in a new family of the class Alphaproteobacteria, two isolates in a new order of the class Gammaproteobacteria, three isolates in two new families of the subclass Actinobacteridae, and two isolates in the subclass Rubrobacteridae. These new isolates represent the first laboratory cultures able to be assigned to some of these groups and greatly increase the number of cultivated strains known for others. This demonstrates that a minimal change in cultivation strategy (using a polymeric growth substrate and longer incubation times) can result in the isolation of globally distributed but previously uncultured phylogenetically novel soil bacteria.