Phylogeogrpahy and genetic diversity of terrestrial arthropods from the Ross Dependency, Antarctica

The pattern of genetic diversity in many species observed today can be traced back to historic ecological events that influenced the distribution of species not only on a global but also a local scale. For example, historical events such as habitat fragmentation, divergence in isolation, and subsequent range expansion, can result in a recognisable pattern of genetic variation which can be used to infer ecological factors (e.g. effective population size, dispersal capacity), as well as those affecting speciation processes. This thesis examines these issues from a phylogeographic and phylogenetic perspective by analysing patterns of variation in the mtDNA cytochrome c oxidase sub-unit 1 (COI) gene in two co-occurring Antarctic endemic arthropods in Southern Victoria Land, Ross Dependency. Within the Southern Victoria Land Dry Valleys of Garwood, Marshall and Miers, populations of the springtail Gomphiocephalus hodgsoni (Collembola: Hypogastruridae) and mite Stereotydeus mollis (Acari: Prostigmata) revealed consistently dissimilar patterns of genetic structure. COI divergence within G. hodgsoni was less than 0.7%, while divergence within S. mollis reached upwards of 17%. Within our study area G. hodgsoni and S. mollis harboured 10 and 22 haplotypes, respectively and showed links to previously sampled populations across Southern Victoria Land. The distribution of G. hodgsoni haplotypes across sites was homogenous while those of S. mollis were distinctly heterogenous. The extremely low genetic variation and links to previously sampled populations suggest that G. hodgsoni is a relatively recent colonist within our study area and/or the victim of an extreme bottleneck event. On the other hand, the extreme levels of genetic diversity observed for S. mollis, and the occurrence of two highly divergent haplotypes that were unique to our study area, suggest that: (1) S. mollis may have had a longer association in isolation with our southern study area; and/or (2) S. mollis has colonised our study area on more than one occasion via multiple extant refugial populations. Throughout its entire Southern Victoria Land range S. mollis is characterised by extremely high levels of mtDNA (COI) divergence (greater than 17%), suggesting a possible multi species complex. To examine this issue, I used both Neighbour Joining (NJ) and Maximum Likelihood (ML) methods to construct a phylogeny utilising all 50 known unique S. mollis sequences with other Victoria Land congeners including an available S. belli sequence, and several new S. shoupi sequences. Both NJ and ML analyses revealed significantly congruent trees with strong bootstrap support. The morphologically similar S. shoupi was placed as a monophyletic sister group, basal to S. mollis in both analyses with strong support. However, there was disagreement between the two methods in the placement of the single S. belli sequence within in the resulting phylogenies which was not possible to resolve with the current data. Despite this latter uncertainty, the possibility of cryptic species within S. mollis remains. Collectively, these studies have demonstrated differences in the genetic structure between two co-occurring species and suggested how similar historic processes, combined with differing life history attributes can lead to that differentiation. Furthermore, genetic analyses were used to identify isolated and unique populations, which are likely to be of high conservation value

Latitudinal distribution and mitochondrial DNA (COI) variability of Stereotydeus spp. (Acari: Prostigmata) in Victoria Land and the central Transantarctic Mountains

We examined mitochondrial DNA (COI) variability and distribution of Stereotydeus spp. in Victoria Land and the Transantarctic Mountains, and constructed Neighbour Joining (NJ) and Maximum Likelihood (ML) phylogenetic trees using all publicly available COI sequences for the three Stereotydeus species present (S. belli, S. mollis and S. shoupi). We also included new COI sequences from Miers, Marshall and Garwood valleys in southern Victoria Land (78°S), as well as from the Darwin (79°S) and Beardmore Glacier (83°S) regions. Both NJ and ML methods produced trees which were similar in topology differing only in the placement of the single available S. belli sequence from Cape Hallett (72°S) and a S. mollis haplotype from Miers Valley. Pairwise sequence divergences among species ranged from 9.5–18.1%. NJ and ML grouped S. shoupi from the Beardmore Glacier region as sister to those from the Darwin with pairwise divergences of 8%. These individuals formed a monophyletic clade with high bootstrap support basal to S. mollis and S. belli. Based on these new data, we suggest that the distributional range of S. shoupi extends northward to Darwin Glacier and that a barrier to dispersal for Stereotydeus, and possibly other arthropods, exists immediately to the north of this area

Wild record of an apple snail in the Waikato River, Hamilton, New Zealand and their incidence in freshwater aquaria

We report the discovery of a single specimen of a live apple snail Pomacea diffusa Blume 1957 (Ampullariidae: Prosobranchia), from the Waikato River, Hamilton city, central North Island, New Zealand. This species, along with the congeneric P. insularum, is imported for the aquarium trade, and its occurrence in the river likely stemmed from an aquarium release. A survey of 55 aquaria belonging to 43 hobbyists revealed 27 apple snails, with one owner having 22 snails. Assessment of environmental tolerances and impacts of P. diffusa, based largely on studies of the closely related and commonly confused congener P. bridgesii, suggests that direct habitat impacts by this species are likely to be minor. However, there could be indirect influences on native biodiversity through predation on eggs or competition for food supplies with other detritivorous species if densities were to become high. Water temperatures in the Waikato River below Hamilton (10-23˚C in 2009) may enable released individuals to persist for an extended period, and over summer may exceed the threshold required to enable breeding. However, population establishment would be most likely in locations where water is heated through geothermal influences or industrial cooling water discharges

Monitoring brown trout (Salmo trutta) eradication in a wildlife sanctuary using environmental DNA

Restoration of habitats often necessitates the eradication of exotic animals from a specified area. One of the many challenges associated with the removal of introduced animals is determining the distribution and continued presence of individuals in order to efficiently target control operations and minimise any adverse effects associated with removal. We examined the feasibility of using environmental DNA (eDNA) from water samples, relative to more traditional electric fishing, netting and spotlight surveys (i.e., visual observations of the small streams at night), to determine the presence of brown trout. Samples were taken from within the Zealandia Sanctuary near Wellington, New Zealand, before and after treatment with the piscicide rotenone. Using filtration of water samples, we successfully extracted brown trout DNA from water both before and after rotenone treatment. In most cases, DNA presence corresponded to results obtained through netting and spotlight surveys, and in one instance detected the continued presence of trout in a treated stream (which was subsequently confirmed). We conclude that the use of environmental DNA to detect the presence of exotic fish can be a useful tool to assist in the assessment and restoration of aquatic habitats

Measuring category intuitiveness in unconstrained categorization tasks

What makes a category seem natural or intuitive? In this paper, an unsupervised categorization task was employed to examine observer agreement concerning the categorization of nine different stimulus sets. The stimulus sets were designed to capture different intuitions about classification structure. The main empirical index of category intuitiveness was the frequency of the preferred classification, for different stimulus sets. With 169 participants, and a within participants design, with some stimulus sets the most frequent classification was produced over 50 times and with others not more than two or three times. The main empirical finding was that cluster tightness was more important in determining category intuitiveness, than cluster separation. The results were considered in relation to the following models of unsupervised categorization: DIVA, the rational model, the simplicity model, SUSTAIN, an Unsupervised version of the Generalized Context Model (UGCM), and a simple geometric model based on similarity. DIVA, the geometric approach, SUSTAIN, and the UGCM provided good, though not perfect, fits. Overall, the present work highlights several theoretical and practical issues regarding unsupervised categorization and reveals weaknesses in some of the corresponding formal models

Extreme glacial legacies: a synthesis of the Antarctic springtail phylogeographic record

We review current phylogeographic knowledge from across the Antarctic terrestrial landscape with a focus on springtail taxa. We describe consistent patterns of high genetic diversity and structure among populations which have persisted in glacial refugia across Antarctica over both short (10 Mya) timescales. Despite a general concordance of results among species, we explain why location is important in determining population genetic patterns within bioregions. We complete our review by drawing attention to the main limitations in the field of Antarctic phylogeography, namely that the scope of geographic focus is often lacking within studies, and that large gaps remain in our phylogeographic knowledge for most terrestrial groups.Angela McGaughran, Mark I. Stevens, Ian D. Hogg and Antonio Carapell

WORKING PARENTS' CONVERSATIONAL RESPONSES TO THEIR TWO-YEAR-OLD SONS (LINGUISTIC INPUT, LANGUAGE ACQUISITION).

Despite claims by some theorists to the contrary, investigators have shown that information about grammatical errors is available to young children learning language via the conversational responses of their parents. The present study described five categories of responses in the conversations of working mothers and fathers to their normally developing two-year-old sons, and investigated whether any of these responses were differentially related to well-formed vs. ill-formed child utterances. Subjects were six middle-class, monolingual (English) parent-child dyads. Parents worked full-time jobs and the children were enrolled in full-time daycare. Within a two week period, four 20-minute conversational samples were audio and video recorded for each dyad in the subjects' homes during freeplay activities of the subjects' choice. Results indicated that the pattern of responses for these six parents was very similar to that reported for other parent-child dyads. The most frequent type of response for all parents was one that continued the conversation without either repeating or clarifying the child's previous utterance. The least frequent type of response was one that explicitly corrected portions of the child's utterance. Of all responses, repetitions--both clarifying and nonclarifying--appeared to be the type of response most differentially related to well-formed and ill-formed child utterances. Exact repetitions were more likely to follow well-formed utterances, while the remaining repetitions were more likely to follow ill-formed utterances. This pattern of differential responses was similar for all six dyads. Very few differences regarding the style or pattern of interaction were noted for fathers and mothers. Implications were drawn regarding the nature of linguistic input that is available to two-year-old children learning language

Where Predators and Prey Meet: Anthropogenic Contact Points Between Fishes in a Freshwater Estuary

The Sacramento–San Joaquin Delta has been invaded by several species of non-native predatory fish that are presumed to be impeding native fish population recovery efforts. Since eradication of predators is unlikely, there is substantial interest in removing or altering manmade structures in the Delta that may exacerbate predation on native fish (contact points). It is presumed that these physical structures influence predator-prey dynamics, but how habitat features influence species interactions is poorly understood, and physical structures in the Delta that could be remediated to benefit native fish have not been inventoried completely. To inform future research efforts, we reviewed literature that focused on determining the effects of predator-prey interactions between fish, based on contact points that are commonly found in the Delta. We also performed a geospatial analysis to determine the extent of potential contact points in the Delta. We found that the effects of submerged aquatic vegetation (SAV) and artificial illumination are well studied and documented to influence predation in other freshwater systems worldwide. Conversely, other common structures in the Delta—such as docks, pilings, woody debris, revetment, and water diversions—did not have the same breadth of research. In the Delta, the spatial extent of the different types of contact points differed considerably. For example, 22% of the Delta water surface area is occupied by SAV, whereas docks only cover 0.44%. Our conclusion, based on both the literature review and spatial analysis, is that the effects of SAV and artificial illumination on predation warrant the most immediate future investigation in the Delta.

Non-Native Fish Predator Density and Molecular-Based Diet Estimates Suggest Differing Impacts of Predator Species on Juvenile Salmon in the San Joaquin River, California

https://doi.org/10.15447/sfews.2018v16iss4art3 The Sacramento-San Joaquin Delta is a major survival bottleneck for imperiled California salmonid populations, which is partially due to a multitude of non-native fish predators that have proliferated there throughout the 20th century. Understanding the diets of salmonid predators is critical to understanding their individual impacts, role in the food web, and the implications for potential management actions. We collected the stomach contents of Striped Bass Morone saxatilis, Largemouth Bass Micropterus salmoides, Channel Catfish Ictalurus punctatus and White Catfish Ameiurus catus sampled from three 1-km reaches in the lower San Joaquin River in 2014 and 2015 during the peak juvenile salmon outmigration period. We tested each stomach (n = 582) for the presence of juvenile Chinook Salmon Oncorhynchus tshawytscha and other prey items using a genetic barcoding technique. Channel Catfish had significantly higher frequency of Chinook Salmon in their stomachs (27.8% of tested Channel Catfish contained Chinook Salmon DNA), compared to the other three predators (2.8% to 4.8%). However, non-native fish species occurred at greater frequencies in the diets of all four predator species than salmon. Using depletion estimation from electrofishing, we were able to generate population densities for Striped Bass and Largemouth Bass in our reaches. Largemouth Bass were evenly distributed throughout all three reaches, at a mean density of approximately 333 (± 195 SE) per km of river. Striped Bass were patchily distributed, ranging from 21 to 1,227 per km. Extrapolating the frequency of salmon detected in stomachs to the predator abundance estimates, we estimate that the population of Largemouth Bass we sampled consumed between 3 and 5 Chinook Salmon per day per 1-km study reach (consumption rate of 0.011 salmon per predator per day), whereas the Striped Bass population consumed between 0 and 24 Chinook Salmon per day (0.019 salmon per predator per day)