Melissa E. Carew

Shifting clinal patterns and microsatellite variation in Drosophila serrata populations: a comparison of populations near the southern border of the species range

Geographical patterns for quantitative traits in Drosophila and other insects are commonly used to investigate climatic selection. They are usually determined from comparisons of populations over extensive areas and based on one collection per population. Here we consider patterns in the Australian endemic species Drosophila serrata established over a shorter transect with repeated sampling. Summer (prewinter) and spring (post‐winter) collections were made from 10 to 14 localities, incorporating the southern border of D.serrata and extending approximately 1000 km northwards along the eastern coast of Australia. Linear or curvilinear associations with latitude were evident for development time, viability and cold resistance but patterns differed between collections. Some geographical (population) and genetic associations between traits were found and these also tended to differ between collections. Results confirm the importance of cold stress resistance over winter to the southern border of this species. Microsatellite markers were developed for D.serrata. These indicated a low level of genetic differentiation between populations, high levels of gene flow and no evidence that the most southerly populations were isolated. The results suggest that selection generated geographical patterns in cold resistance, development time and viability, and that substantial gene flow may prevent adaptation at the border to conditions beyond the current distribution of D. serrata.

Mutability of microsatellites developed for the ant Camponotus consobrinus

Five highly polymorphic (GA)n microsatellite loci are reported for the formicine ant Camponotus consobrinus. The occurrence of many nests with a simple family structure enabled a search for new mutations, 11 of which were found from 3055 informative typings. These mutations were not randomly distributed across loci, 10 of them occurring at the locus Ccon70. The spectrum of mutations across alleles at Ccon70 was also nonrandom, with all of them occurring in alleles in the upper half of the allele size distribution. Six of the Ccon70 mutations decreased allele size. The mutations observed fit the stepwise mutation model well, i.e. mutations could always be assigned to an allele which differed in size from them by one repeat unit. The parental origins of the Ccon70 mutations were established and appear more female biased than vertebrate mutations, significantly so compared with human haemophilia A and primate intron mutations. This result may indicate that the lack of meiosis in males (which are haploid in ants) reduces the mutation rate in that sex relative to species in which both sexes are diploid.

Molecular markers indicate that the wheat curl mite, Aceria tosichella Keifer, may represent a species complex in Australia

The wheat curl mite (WCM), Aceria tosichella Keifer, is an eriophyoid pest of cereals, and the vector responsible for transmitting wheat streak mosaic virus. Several authors have suggested cryptic species of this mite identified through morphological variation, but this has never been conclusively demonstrated. Here, we use the mitochondrial 16S rRNA gene and two nuclear markers (internal transcribed spacer 1 and adenine nucleotide translocase) to show that WCM from Australia consists of at least two separate lineages that may represent putative species. In our study, both WCM variants were widespread and the only eriophyoids found on wheat varieties. The WCM variants were also found on alternate host plants, including some plants not known to host WCM. These results have implications for the control of this pest within Australian cereal crops.

DNA identification of urban Tanytarsini chironomids (Diptera:Chironomidae)

Abstract DNA barcoding is becoming widely used to provide species identifications in a variety of invertebrate taxa, but there has been little application so far to environmental monitoring. Here we make this connection using a group of aquatic macroinvertebrates, chironomids of the tribe Tanytarsini. Tanytarsini larvae commonly collected in biological surveys can be difficult to identify to species because of high intraspecific variability and because not all larvae are linked to described adult life stages. We examined whether Tanytarsini larvae could be reliably identified to species with polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) using the mitochondrial cytochrome oxidase I (COI) gene. Tanytarsini were collected from lentic environments and consisted of 3 common genera (Cladotanytarsus, Paratanytarsus, and Tanytarsus). COI PCR-RFLP profiles could discriminate larvae, including morphologically similar larvae, and could be linked to described life stages. COI sequences identified the same species from different localities. DNA identification has potential for distinguishing Tanytarsini species and facilitating their use as biological indicators.

Species status and population genetic structure of grapevine eriophyoid mites

Bud mite, blister mite (Colomerus vitis Pagenstecher), and rust mite (Calepitrimerus vitis Nalepa) (Acari: Eriophyoidae) are recognized grapevine pests. Much of the biology and ecology of these pests is poorly understood. We used two types of molecular markers to gain further insight into the breeding biology and population structure of these mites, using individuals collected from sites around south‐eastern Australia. Patterns of genetic variation observed using PCR‐RFLP of ITS 1 (Internal Transcribed Spacer 1) confirmed the separate species status of the rust mite, and resolved the species status of bud and blister mites, revealing two closely related but distinct species. Microsatellite markers revealed extensive genetic differentiation between bud mite populations and blister mite populations even at micro‐geographical levels, suggesting low movement in these species. The findings indicate that separate control strategies are needed against bud and blister mites, and that localized control strategies are likely to be effective given their limited dispersal.

The Utility of DNA Markers in Classical Taxonomy: Using Cytochrome Oxidase I Markers to Differentiate Australian Cladopelma (Diptera: Chironomidae) Midges

Abstract There is growing debate about the role DNA methods can play in species identification and whether DNA-based methods can become the predominant means to describe species. DNA methods already have the potential to assist in traditional taxonomy and form the basis of routine species identification once species boundaries are clear. We show how DNA methods helped in separating three “species” of the midge, Cladopelma Kieffer. The “species” were initially identified in surveys from Melbourne, Australia, by using cytochrome oxidase I (COI) polymerase chain reaction-restriction fragment-length polymorphism markers. The DNA markers and further sequence analysis of COI assisted in identifying unique morphological characters for the “new” species, and provided a way of linking different life stages. DNA tools should be used to routinely to assign species groups such as the Chironomidae, where in some genera there are morphological ambiguities and where life cycle stages cannot be easily connected.

Identifying chironomids (Diptera: Chironomidae) for biological monitoring with PCR–RFLP

Chironomids are excellent biological indicators for the health of aquatic ecosystems, but their use at finer taxonomic levels is hindered by morphological similarity of species at each life stage. Molecular markers have the potential to overcome these problems by facilitating species identification particularly in large-scale surveys. In this study, the potential of the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) approach was tested to rapidly distinguish among chironomids within a geographic area, by considering chironomid species from Melbourne, Australia. By comparing molecular markers with diagnostic morphological traits, RFLP profiles of the cytochrome oxidase I (COI) region were identified that were specific to genera and some common species. These profiles were used to develop an RFLP-based key, which was validated by testing the markers on samples from several wetlands and streams. As well as allowing for rapid identification of species that are difficult to separate on morphological grounds, this approach also has the potential to resolve current taxonomic ambiguities.

Isolating the impact of sediment toxicity in urban streams

Several factors can contribute to the ecological degradation of stream catchments following urbanization, but it is often difficult to separate their relative importance. We isolated the impact of polluted sediment on the condition of an urban stream in Melbourne, Australia, using two complementary approaches. Using a rapid bioassessment approach, indices of stream condition were calculated based on macroinvertebrate field surveys. Urban stream reaches supported impoverished macroinvertebrate communities, and contained potentially toxic concentrations of heavy metals and hydrocarbons. Using a field microcosm approach, a bioassay was carried out to assess sediment pollution effects on native macroinvertebrates. Sediment from urban sites substantially altered the microcosm macroinvertebrate community, most likely due to elevated heavy metal and hydrocarbon concentrations. Macroinvertebrate surveys combined with a bioassay approach based on field microcosms can help isolate the effect of stream pollutants in degraded ecosystems.

Phylogenetic signals and ecotoxicological responses: potential implications for aquatic biomonitoring

Macroinvertebrates can be successfully used as biomonitors of pollutants and environmental health because some groups are sensitive whereas, others are relatively tolerant to pollutants. An issue of ongoing debate is what constitutes an appropriate group for biomonitoring; should the group represent species, genera or higher taxonomic levels? A phylogenetic framework can provide new insights into this issue. By developing phylogenies for chironomids and mayflies, this investigation shows that there is strong phylogenetic signal for pollution responses, and that phylogenetic nodes are common to tolerant and sensitive groups of species. A phylogenetic analysis of biotic indices developed for mayflies based on their response to organic pollution shows that mayfly families varied in pollution tolerance. In contrast, based on sediment zinc concentrations as an indicator of pollution tolerance, Australian chironomids tend to vary in tolerance at lower taxonomic levels. Published data on North American chironomids shows much of the signal for pollution responses is contained within genera rather than sub-families. Tools are now available to distinguish whether this signal reflects historical evolutionary constraints or environmental effects leading to common evolved responses. This suggests that ideally higher taxonomic levels should be used for biomonitoring when there are strong phylogenetic constraints at higher levels. Evolutionary considerations can therefore help to guide the development of macroinvertebrate biomonitors and provide insights into processes that produce sensitive and tolerant taxa.

Molecular, morphological and behavioural data reveal the presence of a cryptic species in the widely studied Drosophila serrata species complex

The Drosophila serrata species complex from Australia and New Guinea has been widely used in evolutionary studies of speciation and climatic adaptation. It is believed to consist of D. serrata, D. birchii and D. dominicana, although knowledge of the latter is limited. Here we present evidence for a previously undescribed cryptic member of the D. serrata species complex. This new cryptic species is widespread in far north Queensland, Australia and is likely to have been previously mistaken for D. serrata. It shows complete reproductive isolation when crossed with both D. serrata and D. birchii. The cryptic species can be easily distinguished from D. serrata and D. birchii using either microsatellite loci or visual techniques. Although it occurs sympatrically with both D. serrata and D. birchii, it differs from these species in development time, viability, wing size and wing morphology. Its discovery explains patterns of recently described mitochondrial DNA divergence within D. serrata, and may also help to clarify some ambiguities evident in early evolutionary literature on reproductive incompatibility within the D. serrata species complex.