Phylogeography of the freshwater fish, Mogurnda adspersa, in streams of northeastern Queensland, Australia: Evidence for altered drainage patterns

A phylogeographic survey was used to elucidate the relative roles of historical processes and contemporary gene flow in structuring the genetic pattern observed with Mogurnda adspersa. This species of freshwater fish is found in the rivers and streams of the northeastern highlands of Queensland, Australia. Specifically, this project focused on populations in the Tully and Herbert Rivers in the Atherton Tablelands. Sequence analysis indicated that three distinct clades exist in the headwaters of the Tully River. The population sampled from one of the Tully River streams (Cheetah Creek) contained haplotypes that displayed ≃ 3.4% sequence divergence from other haplotypes detected in this river. Furthermore, these haplotypes formed part of the clade which exists throughout not only the Herbert River but other surrounding drainages in the area. These results support the hypothesis that the current genetic structure is strongly affected by changes in drainage patterns due to geomorphological processes that occurred in the recent past.</p

Historical interdrainage dispersal of eastern rainbowfish from the Atherton Tableland, north-eastern Australia

The widespread distribution of the eastern rainbowfish Melanotaenia splendida splendida throughout the isolated headwaters of the rivers on the Atherton Tableland, north-eastern Australia, suggests multiple colonization events from the eastern lowlands via each respective river channel, or a single colonization event on to the tableland with subsequent dispersal between the headwaters. To explore the likely processes that resulted in the current distribution on the tableland, two models of gene flow were tested: (a) the hierarchical gene flow model that tests the hypothesis for contemporary gene flow via stream channels and (b) the stepping stone model that tests for dispersal between streams. Neither of these models explained the observed genetic structure, adequately. However, there is support for extensive historical dispersal across the headwaters of the isolated drainages. If this dispersal followed a single colonization event, the subsequent range expansion could have facilitated a rapid rise in population size due to an increase in suitable habitat. The genetic data indicates an eight-fold increase in population size c. 100 thousand years ago.</p

Population structure in the freshwater shrimp (Paratya australiensis) inferred from allozymes and mitochondrial DNA

In 1995, an allozyme study was conducted on the genetic structure of a population of the common atyid shrimp, Paratya australiensis, in the Conondale Range, south-eastern Queensland with two subcatchments each within two river drainages sampled. The allozyme study revealed a high degree of population structure, with the data interpreted as reflecting a pattern of restricted contemporary gene flow, primarily between streams within subcatchments. High levels of differentiation occurred between all subcatchments. In this study, we analysed a partial fragment of the mitochondrial COI gene in order to further test and verify these results. The mtDNA data largely conflicted with the hypothesis of restricted gene flow indicating that contemporary dispersal was highly unlikely, even between streams within subcatchments, with many sites fixed for unique mtDNA haplotypes. Additionally, the level of divergence between the Stony Creek subcatchment and all other sampling sites indicated that it had been isolated for approximately 2-3 million years, while low levels of divergence were detected across the Conondale Range between the Kilcoy and Booloumba Creek subcatchments. The sharing of alleles at certain allozyme loci between all subcatchments is, therefore, likely to be the result of ancestral retention and possibly because of the effects of balancing selection.</p

Genetic differentiation and dispersal among populations of Paratya australiensis (Atyidae) in rainforest streams in southeast Queensland, Australia

We used measures of genetic differentiation at seven allozyme loci to estimate the degree of movement of a stream invertebrate within and between catchments. Populations of Paratya australiensis, a common atyid shrimp, were sampled from three rainforest streams from each of two subcatchments in two adjacent drainage systems in southeast Queensland. Marked genetic differentiation was observed at all loci, suggesting extremely limited movement on a small spatial scale. This result is surprising given the widespread geographic distribution of P. australiensis in Australia, its great abundance in headwater streams in southeast Queensland, and the presence of a planktonic larval stage. Large differences in genetic structure occurred between streams, in some instances between those in the same subcatchment. Even larger genetic differences were seen between samples from streams in different subcatchments, with alternative alleles being fixed at different sites. The greatest differences were not, however, between the two drainage systems as predicted by the stream hierarchy model. This extreme spatial structuring was remarkably stable over a two-year period

A hierarchical analysis of the genetic structure of an aquatic insect Bungona (Baetidae: Ephemeroptera)

Recent studies of the genetic structure of stream-dwelling organisms have suggested that fine-scale patterns are the consequence of patchy recruitment from a small number of matings and limited in-stream dispersal. Predictions of this hypothesis were tested by spatial and temporal analysis of the genetic structure of populations of a stream mayfly (Bungona sp.: Baetidae) in subtropical streams in south-eastern Queensland. Significant departures from Hardy-Weinberg proportions occurred more often than would be predicted by chance alone and no consistent pattern was observed across sites, loci or sampling times. As in previous studies, the largest differentiation was observed at the smallest spatial scale (reaches within streams) on most sampling occasions. These data provide additional support for a patchy recruitment hypothesis. Despite the fine-scale population structure, there was evidence of widespread adult dispersal across the study region, especially between streams and subcatchments within the same block of continuous dense forest.</p

Characterisation of candidate nuclear genes for species delineation in the genus Cherax

Understanding the evolutionary history and phylogenetic relationships between rare and common species is necessary for the effective management of rare species. The genus Cherax, a group of freshwater crayfish species, is of interest in this regard as a number of species are rare or have restricted distributions while other species are common and widespread. Here we describe the characterisation of three novel nuclear genes of the haemocyanin superfamily for phylogenetic reconstruction of the genus. All novel markers developed in this study amplified consistently in species from three divergent clades of the genus Cherax. The level of polymorphism found in these markers was consistently higher than that found in other nuclear genes previously used in invertebrate systematics, such as NaK ATP-ase. In combination, these markers will be useful to delineate phylogenetic relationships between rare and common Cherax species.\u

Genetic differentiation among populations of Caridina zebra (Decapoda: Atyidae) in tropical rainforest streams, northern Australia

1. Caridina zebra is a common atyid shrimp in some tropical rainforest streams in far north Queensland, Australia. Genetic variation at five allozyme loci was used to estimate the level of dispersal among populations of this species, within and between stream systems. Shrimps were sampled from nine streams in the Tully River catchment and two headwater streams in the adjacent Herbert River catchment in an area under consideration for extensive hydroelectric development. 2. High levels of genetic differentiation were recorded among most populations which suggests that, like other fully aquatic species, movement is limited to a very small spatial scale. 3. In the Tully catchment, populations of shrimp from streams with confluences at high altitude showed less genetic differentiation than those from streams which directly entered the lower river. Dispersal between the latter streams is clearly limited by the presence of large waterfalls and cascades. 4. Adjacent stream populations were often highly differentiated, despite their close proximity, suggesting that overland dispersal is unlikely. However, populations of shrimp in the two streams in the Herbert catchment were strikingly similar in genetic structure to those in adjacent headwater streams of the Tully. Such similarity may reflect relatively recent changes in drainage patterns.</p

Diet of the eastern barn owl (Tyto delicatula) in the Simpson Desert reveals significant new records and a different mammal fauna to survey data

The eastern barn owl (Tyto delicatula) is a significant native predator of small mammals in Australia. Regurgitated pellets can provide important data on species presence, current or historical changes in mammal fauna over time, or data on cryptic or threatened species. We collected 125 pellets from Cravens Peak reserve, Simpson Desert, Queensland, and examined the contents, including changes in diet over time (using age of pellet as a proxy) and the relative importance of different prey. In total, 642 unique prey items were recorded, 92% of which were mammals. Small rodents were the dominant prey – Mus musculus and Pseudomys hermannsburgensis, and the presence of Notomys cf. fuscus, Pseudantechinus cf. mimulus and Dasycercus blythi were all significant, being range extensions. Such data add to more traditional or novel techniques to record community changes over time

Genetic evaluation of the unknown contribution of stocked fish in angler catches : a case study using mulloway Argyrosomus japonicus

Stock enhancement involves the augmentation of wild populations with hatchery-reared recruits. Stock enhancement generally also includes a postrelease monitoring program which tracks stocked individuals within the fishery, and this relies on having a means to identify the likely origin of recaptured fish (e.g., physical, otolith, or genetic tags). This study reports the application of sibship analysis to retrospectively infer the origin of mulloway (Argyrosomus japonicus) within stocked estuaries when other means of identification were not available. Eight cohorts of mulloway were stocked into two estuaries across a seven-year period, but only some of the fish released during the program were physically marked with chemical otolith stains. Fish were sampled from stocked estuaries (mostly through an angler-based sampling program) and genotyped for six microsatellite loci, alongside 129 fish sampled from nonstocked estuaries. The presence of multiple sibs within the mixed populations in stocked estuaries was used to infer the origin of captured fish against a background of sibship for known-origin individuals (verified by otolith marks) and sibship levels within unstocked estuaries. The analysis suggested hatchery-reared fish could have contributed 9% of individuals sampled from the augmented populations (7% when corrected for background sibship). The proportion of fish inferred to be of hatchery origin decreased with size (likely due to mortality and migration), and the expected contribution rates for hatchery-reared fish differed among cohorts. The results highlight that sibship analysis may be useful for retrospective genetic evaluation of stocked estuaries.</p