The Australian lungfish is a unique living representative of an ancient dipnoan lineage, listed as ‘vulnerable’ to extinction under Australia’s Environment Protection and Biodiversity Conservation Act 1999. Historical accounts indicate this species occurred naturally in two adjacent river systems in Australia, the Burnett and Mary. Current day populations in other rivers are thought to have arisen by translocation from these source populations. Early genetic work detected very little variation and so had limited power to answer questions relevant for management including how genetic variation is partitioned within and among sub-populations. In this study, we use newly developed microsatellite markers to examine samples from the Burnett and Mary Rivers, as well as from two populations thought to be of translocated origin, Brisbane and North Pine. We test whether there is significant genetic structure among and within river drainages; assign putatively translocated populations to potential source populations; and estimate effective population sizes. Eleven polymorphic microsatellite loci genotyped in 218 individuals gave an average within-population heterozygosity of 0.39 which is low relative to other threatened taxa and for freshwater fishes in general. Based on F ST values (average over loci = 0.11) and STRUCTURE analyses, we identify three distinct populations in the natural range, one in the Burnett and two distinct populations in the Mary. These analyses also support the hypothesis that the Mary River is the likely source of translocated populations in the Brisbane and North Pine rivers, which agrees with historical published records of a translocation event giving rise to these populations. We were unable to obtain bounded estimates of effective population size, as we have too few genotype combinations, although point estimates were low, ranging from 29 - 129. We recommend that, in order to preserve any local adaptation in the three distinct populations that they be managed separately.

1. We performed spatial genetic analyses, incorporating landscape genetic methods using microsatellite data and phylogeographic analyses using mtDNA data, to identify the principal factors that determine population heterogeneity of the tropical freshwater fish, Mogurnda mogurnda, in the Daly River, northern Australia. We tested the individual and interactive effects of several environmental variables on spatial genetic patterns, including metrics relating to connectivity (i.e. stream distance, maximum stream gradient and elevation), habitat size (i.e. mean annual discharge) and a categorical variable relating to population history, as determined by mtDNA phylogeographic analyses. The Daly River is geomorphologically and hydrologically complex, and M. mogurnda has life history traits that limit its dispersal potential at river basin scales. Thus, we predicted that variables relating to connectivity would be the most important landscape factors driving population structure of the species. 2. Tree-based phylogeographic analyses indicated four divergent mtDNA lineages within M. mogurnda in the Daly River, although three of the lineages were sympatric in various combinations and did not correspond with microsatellite groups identified by assignment tests. The allopatric mtDNA lineage detected in the uppermost part of the catchment was also identified as being highly differentiated by the microsatellite data, strongly suggesting that it may be a cryptic species. This site was therefore excluded from subsequent landscape genetic analyses. 3. Analyses of Molecular Variance indicated that M. mogurnda has a hierarchical population structure in the Daly River, thus supporting theoretical expectations that hierarchically arranged river habitats in dendritic systems impose hierarchal population structures on lotic species. 4. All landscape genetic analyses rejected stream distance, and supported stream gradient, as the major determinant of spatial genetic variation in M. mogurnda in the Daly River. Support for elevation as a determinant of spatial genetic patterns differed among the landscape genetic methods. Several of the landscape genetic methods also indicate that population history, including secondary contact between divergent and formerly allopatric genetic lineages, has a strong influence on spatial genetic patterns within M. mogurnda in the Daly River.5. This study demonstrates the need to consider multiple environmental factors, especially factors relating to connectivity, and their interactions in spatial genetic analysis, rather than just geographic distance. Importantly, it demonstrates the need to account for population history and evolutionary divergences in landscape genetic analyses.

A set of twelve microsatellite DNA loci were developed for the threatened Australian freshwater fish Mogurnda adspersa (Eleotridae). Primers were tailed with one of four 20-mer oligonucleotides for use in four-colour fluorescent detection and optimised for multiplex PCR. The loci were used to genotype individuals from two populations in the Pioneer River catchment of central Queensland, eastern Australia. Number of alleles per locus ranged from 2 to 33 and per locus heterozygosity ranged from 0.06 to 0.81. Successful cross-species amplification of all loci was achieved in the congener M. mogurnda. These markers will be used to estimate effective population size and to examine the relationship between flow regime and population demographic parameters.

Wolbachia pipientis is a commonly occurring endosymbiont with well-characterised effects on host reproductive biology associated with its infection of the gonads. Wolbachia infections are also widespread in somatic tissues and consequently they have the potential to play a much broader role in host biology. Recently, Wolbachia was shown to alter the locomotion of Drosophila melanogaster in response to food cues in the laboratory. To determine whether this laboratory-based phenotype might translate to real differences for insects in the field, we performed a simple mark-release-recapture experiment with Wolbachiainfected D. melanogaster in a forested habitat. We demonstrate that infected flies are recaptured at twice the rate of uninfected flies, although infection does not affect the distance traveled by those flies recaptured. The differences in recapture could be explained by infection-induced changes in physiology or behavior. If generalizable, such changes may affect the interpretation of behavioral studies for Wolbachia-infected insects and have potential implications for the dynamics of Wolbachia infections in natural populations, including situations where Wolbachia-infected insects are being released for biological control.

Freshwater fish are a group that is especially susceptible to biodiversity loss as they often exist naturally in small, fragmented populations that are vulnerable to habitat degradation, pollution and introduction of exotic species. Relatively little is known about spatial dynamics of unperturbed populations of small-bodied freshwater fish species. This study examined population genetic structure of the purple spotted gudgeon (Mogurnda adspersa, Eleotridae), a small-bodied freshwater fish that is widely distributed in eastern Australia. The species is threatened in parts of its range but is common in coastal streams of central Queensland where this study took place. Microsatellite (msat) and mitochondrial DNA (mtDNA) variation was assessed for nine sites from four stream sections in two drainage basins. Very high levels of among population structure were observed (msat F ST = 0.18; mtDNA ΦST = 0.85) and evidence for contemporary migration among populations was rare and limited to sites within the same section of stream. Hierarchical structuring of variation was best explained by stream section rather than by drainage basin. Estimates of contemporary effective population size for each site was low (range 28 – 63, Sibship method), but compared favorably with similar estimates for other freshwater fish species, and there was no genetic evidence for inbreeding or recent population bottlenecks. In conclusion, within a stable part of its range, M adspersa exists as a series of small, demographically stable populations that are highly isolated from one another. Complimentary patterns in microsatellites and mtDNA indicate this structuring is the result of long-term processes that have developed over a remarkably small spatial scale. High population structure and limited dispersal mean that recolonisation of locally extinct populations is only likely to occur from closely situated populations within stream sections. Limited potential for recolonisation should be considered as an important factor in conservation and management of this species.