Department of Biology (Fredericton)
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Impacts of the brown spruce longhorn beetle, Tetropium fuscum (Fabricius) (Coleoptera: Cerambycidae), on insect community structure in its invaded habitat of Nova Scotia, Canada
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by Allyson Anne Heustis, Tetropium fuscum (Coleoptera: Cerambycidae), a wood boring beetle native to Europe, was accidentally introduced to Halifax, Nova Scotia, likely in wood packaging in shipping containers. Non-indigenous species can change insect community diversity, or displace native species. I tested whether the invasive Tetropium fuscum or Tetropium cinnamopterum a native congener, had a significant impact on insect community structure (Simpson’s Diversity, richness, and evenness) in spruce logs, and if impact was greater on closely related species by comparing emerged insects from red and Norway spruce bolts colonized with Tetropium fuscum and Tetropium cinnamopterum to control bolts. Tetropium egg treatments generally reduced community diversity, although the combination of significantly affected indices varied somewhat among Tetropium species and host. In Norway spruce, both Tetropium spp. significantly reduced Simpson’s diversity and richness; evenness was significantly lower only for T. fuscum. In red spruce, both Tetropium spp. significantly reduced richness; only T. fuscum reduced Simpson’s diversity and evenness. Impact of Tetropium on presumed competitors was not simply related to phylogenetic distance: the closest relative was not impacted, although the next closest relative, Evodinus monticola, was significantly reduced in both red and Norway spruce.
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Impacts of the kelp conveyor hypothesis on population genetics of subtidal red algae (Rhodophyta)
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by Cody Brooks, Endemic species of Haida Gwaii are commonly attributed to populations persisting in glacial refugia; however, kelp rafting has been recently proposed to explain the disjunct distributions of macroalgal species previously considered endemic to Haida Gwaii. Using mtDNA from five predominantly subtidal species and three predominantly intertidal species of red algae, this study tested the hypothesis that disjunct distributions between Haida Gwaii and California are caused by kelp rafting of subtidal, non-buoyant species. In support of this hypothesis, genetic connectivity of populations in California and Haida Gwaii was greater in subtidal species than intertidal species and allele frequencies suggest direct migration of subtidal species from Haida Gwaii to California. Interestingly, unique Haida Gwaii alleles in subtidal and intertidal species indicate long residence times for some populations, suggesting glacial refugia and kelp rafting may be jointly responsible for disjunct distributions observed at the population level for macroalgae along this coast.
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In-stream habitat enhancement for juvenile Atlantic salmon in the Little Main Restigouche River, New Brunswick
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by Peter Emerson, Boulder clusters were placed at three sites with small, homogeneous substrate in the Little Main Restigouche River in northern New Brunswick, Canada, in late summer 2005 to improve the rearing habitat for pre-smolt Atlantic salmon (Salmo salar). Population estimates were conducted at enhancement, control and reference sites between 2005-2007 prior to enhancement and for two years following enhancement to compare response of salmon parr. Age-2 parr density increased at enhancement sites following enhancement. During December 2005, a 25-year flood event and subsequent ice up and freshet in spring disturbed the study sites. A method was designed to interpret and rank boulder cluster stability degradation, and the data were compared with electrofishing estimates of abundance of salmon ages 0+, 1+ and 2+. Age 2+ parr abundance and biomass and age 1+ parr abundance were significantly higher at clusters ranked stable than at clusters ranked degraded., Electronic Only.
(UNB thesis number) Thesis 9462
(OCoLC)957123616, M.Sc. University of New Brunswick, Department of Biology, 2014.
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Indirect interactions between the invasive brown spruce longhorn beetle, Tetropium fuscum, and a native defoliator, Choristoneura fumiferana
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by Mallory MacDonnell, Two important pests in Atlantic Canada are an invasive beetle, the brown spruce longhorn beetle (BSLB), and a native defoliator, the spruce budworm. Both species are currently attacking spruce in separate regions; however, there is a high likelihood that these attack ranges will overlap. It remains unknown what impact concurrent attacks of these herbivores might have on trees, or on population trends for either species. We investigated the effects of BSLB on interactions between spruce budworm and red spruce, using field experiments near Halifax, Nova Scotia. We established four stress treatments involving natural and simulated BSLB attack, with five branches on each tree assigned densities of spruce budworm. We measured the impact of natural and simulated BSLB attack on red spruce, and spruce budworm defoliation and examined its dependence on budworm density. We also examined performance of adult moths through fecundity measurements. Natural and simulated BSLB attack did not change density defoliation relationships, relative to no attack. Survival of spruce budworm on red spruce appeared to be reduced as spruce budworm density, presumably due to reductions in the availability of the preferred developing foliage. There are indications that, in general, simulated BSLB stressed trees allow higher larval survival than trees with natural BSLB attack or trees that are unattacked., M.Sc. University of New Brunswick, Department of Biology, 2017.
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Interactions between the invasive brown spruce longhorn beetle, Tetropium fuscum (Fabricius) (Coleoptera: Cerambycidae), and its native congener, Tetropium cinnamopterum (Kirby)
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by Kenneth William Dearborn, Tetropium fuscum (TF) (Coletopetra: Cerambycidae) is a European spruce borer established in Nova Scotia since at least 1990. I tested whether TF displaces a native congener, T. cinnamopterum (TC), in red spruce. Stressed trees, 24 girdled and 24 felled, were selected for natural colonization: 28 inside the invaded zone and 20 outside. Both Tetropium species and their parasitoid wasps emerged exclusively from felled trees. Combined Tetropium density (inside invaded zone = 0.34 ± 0.07 vs. outside = 0.63 ± 0.19 per m2; P = 0.070) and overall parasitism rates (inside invaded zone = 31% vs. outside = 44%; P = 0.111) did not statistically differ inside vs. outside the invasion zone, but TC density was significantly greater outside the invasion zone (0.63 ± 0.19 compared to 0.18 ± 0.05 m2; P = 0.001), suggesting TF may displace TC where they are sympatric.
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Intracellular localization and regulation of Gelatinase-A in zebrafish skeletal muscle
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Matrix metalloproteinase (MMPs) are class-I secreted proteins known to function in extracellular matrix remodeling. However, studies in the last decade and a half revealed the unexpected presence of MMP-2 (a.k.a. gelatinase-A) intracellularly, within cardiomyocytes and implicated them in the pathology of ischemia/reperfusion injury (IRI). Furthermore, the activity of this protease in mammals is controlled by phosphorylation implicating the existence of unknown kinases and phosphatases, and possibly a signalling system that modulate MMP-2 activity inside cells. Two questions that emerge from these discoveries are (1) is the intracellular localization of gelatinase-A is something common in striated muscles, and (2) is its regulation by phosphorylation of physiological significance? Answering these questions is the objective of this thesis.
Using immunofluorescence, confocal microscopy, and ultrathin sectioning, I have confirmed the intracellular localization of Mmp2 in zebrafish skeletal muscle. However, I observed zebrafish Mmp2 accumulating on M-bands within sarcomeres, rather than in the Z-discs as has been reported for mammalian MMP-2 within cardiomyocytes. I also note that the signal sequence that directs this protease into the secretory pathway is consistently poorly recognized, indicating a selective pressure for maintaining a significant intracellular portion of this enzyme. While I was unable to determine the phosphorylation status of Mmp2 purified from zebrafish muscle, there are high probability phosphorylation sites in the Mmp2 sequence that are conserved across all homologues of this protease for which sequence is available. Thus I show that the intracellular localization of gelatinase-A proteases within the sarcomere of striated muscle is not unique to mammalian cardiomyocytes, and that its regulation by phosphorylation is likely an evolutionarily conserved characteristic of physiological significance. I speculate that this protease is a previously unrecognized component of the mechanism that regulates protein turnover within the contractile apparatus of striated muscle.
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Investigating the gut microbiomes of aquatic benthic macroinverterbrates in the Saint John river (New Brunswick, Canada)
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by Shawn Kroetsch, Aquatic invertebrates are key members of aquatic food webs; however, little is known about their gut microbiomes. Understanding how environment, taxonomy, dietary habits, and time alter gut bacteria is important in addressing current gaps in microbiome research. The objectives of this study were to characterize the gut microbiomes of aquatic invertebrates and to assess whether the composition of gut bacteria differs temporally and across taxa with different habitats and feeding habits. Invertebrates from 16 orders were collected from 8 sites within a 20 km reach of the Saint John River (New Brunswick, Canada) in fall 2016 and 2017, with these individuals containing nearly 20,000 operational taxonomic units. Gut microbiomes of invertebrates differed significantly among invertebrate taxa and temporally; however, few significant within-taxa differences were found among habitat types and no significant differences were observed among functional feeding groups. This study is the first to describe the gut microbiomes of aquatic invertebrates in the Saint John River. This information establishes a baseline of natural variability and diversity of aquatic invertebrate gut microbiomes, providing a foundation for future work.
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Larval drift characteristics, habitat use, and environmental determinants of year-class strength in wild age-0 Lake Sturgeon, Acipenser fulvescens, within a large impounded river
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by Laura Marie Henderson, The dynamics of early life stages of Lake Sturgeon ( Acipenser fulvescens) within a large impounded river were studied. Recruitment success, larval drift, and basic habitat and diet use were observed and analysed over a two-year period. As part of a separate study, larval drift monitoring, and juvenile gillnetting were conducted one year prior to the start of the current study; these results were considered preliminary work and included in the analyses. Timing, duration, and extent of larval drift varied from year to year. No correlation was found between year-class strength and water discharge or temperature. Post-drift, age-0 Lake Sturgeon were found in habitats consisting of sand substrates, in depths of greater than 6 m (maximum 24 m), and low to medium velocities (0.0- 0.4 m s-1 ). Diet was composed of Diptera, Ephemeroptera, Trichoptera and Nematoda. Age-0 Lake Sturgeon captured in Dorothy Lake only consumed Dipteran organisms. Nitrogen isotopes indicated that age-0 Lake Sturgeon captured in this lake were significantly different from those captured in other locations of the study area. Daily growth was calculated as 2.0 mm in total length and 0.20 g in weight from August through September. Findings from this study will aid in future age-0 Lake Sturgeon research and management including artificial propagation and nursery habitat remediation.
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Late-quaternary paleoclimate of Mount Field, Tasmania
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by Andrew Rees, The mid-latitudes of the Southern Hemisphere possess a complex history of paleoenvironmental change. I address two objectives using lake sediment records from Tasmania, one of the few landmasses situated within this critical region of the “Water Hemisphere”. First, cosmogenic dates from terminal moraines and sea surface temperatures (SST) suggest the climate of south-eastern Australia warmed rapidly after the Last Glacial Maximum, whereas pollen records indicate temperatures only began to increase at the onset of the Holocene, roughly 11.5 thousand calibrated years before present (cal ka BP). To explicitly address this discrepancy, I surveyed the modern environmental drivers of chironomid (Insecta: Diptera) distributions in Tasmania and developed an independent proxy of temperature. Second, a large body of literature has emerged invoking the Southern Westerly Winds (SWW) and El Niño/Southern Oscillation (ENSO) as major drivers of paleoenvironmental change. Some researchers have hypothesized that the SWW governed broad scale precipitation patterns from 14 to 5 cal ka BP, when ENSO became the main control of synoptic climate. Using a suite of lacustrine proxies, I investigated the nature of the transition from a SWW-to ENSO-dominated climate regime.
In terms of the first objective, pH explains most of the variance in the modern chironomid distributions. This environmental variable delineates between two geological provinces in Tasmania: one province has infertile, acidic soils and the other has soils generally richer in clay, possessing a greater buffering capacity. However, temperature of the warmest quarter (TWARM) explains most of the variance in the chironomid fauna within either geological province. Consequently, I applied a chironomid-based transfer function for TWARM to a pair of fossil chironomid records from Mount Field National Park. Temperatures were at or above modern values early in the record, from about 15 to 13 cal ka BP, supporting the evidence from the cosmogenic dates and SST. After a prolonged cooling, temperatures again returned to modern, supportinga mid-Holocene thermal maximum between 6.7 and 4.6 cal ka BP. I used another lake sediment record from Mount Field to address the second objective. Based on lacustrine proxies, SSW controlled precipitation from 12 to 4.9 cal ka BP, fluctuating from wet to dry conditions around 8.4 cal ka BP. The abrupt shift to a generally dry though variable climate at 4.9 cal ka BP was characterized by an increased fire frequency. Considering all of the proxies, their transitions were nearly simultaneous and concurrent with the onset of ENSO activity in Ecuador, highlighting close links between the equatorial Pacific and south-eastern Australia., Electronic Only.
(UNB thesis number) Thesis 9454.
(OCoLC) 962752679., Ph.D., University of New Brunswick, Department of Biology, 2014.
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Life history trade-offs in host choice for a specialist folivore, spruce budworm (Choristoneura fumiferana)
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by Lauren Stead, Spruce budworm, Choristoneura fumiferana Clem., is an important outbreaking pest in Atlantic Canada. It defoliates several coniferous tree species, including balsam fir, Abies balsamea (L.) Mill, and black spruce, Picea mariana (Mill.) Britton, Sterns & Poggenb.. Budworm is a flush feeder, meaning it feeds on the newest foliage as soon as the buds burst, and times its emergence from diapause accordingly. This emergence often lines up with that of balsam fir, but is asynchronous to its secondary host, black spruce, which bursts much later. This asynchrony with black spruce begs the question of why budworm would choose black spruce as a host if/when balsam fir is available. To better understand the consequences of host plant selection by budworm in the spring for feeding, as well as prior to overwintering, I completed field experiments to determine how host tree species influences the budworm performance during both the overwintering and feeding periods. I established weekly cohorts to put budworm on two host species, simulating a broad window of emergence from diapause, beginning a few weeks before expected budburst of balsam fir to a few weeks after budburst of black spruce. After pupation, I removed the budworm from branches they were on. I assessed bud stage of these host trees for each cohort and various performance measures of surviving budworm. Budworm on balsam fir had higher survival than those on black spruce. I also investigated budworm overwintering mortality on these same trees. In northern New Brunswick, I felled and collected various sections of the host trees including branches and trunks from the upper and middle crown in the spring prior to emergence from diapause. I collected emerging budworm from these tree sections and reared them so I could assess parasitism. Unless budworm emerge from diapause perfectly synchronous to balsam fir’s budburst, black spruce is just as good of a host for budworm to feed and overwinter on. Budworm overwintering on balsam fir had higher parasitism, likely due to its evolution with that host. There are ultimately trade-offs between overwintering mortality and having a superior quality food host. This study is the first to look at how these tri-trophic interactions may affect budworm host selection.
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Linking stream ecosystem integrity to catchment and reach conditions in an intensively-managed forest landscape
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by Maitane Erdozain Ibarra, Forests are vital to maintain headwater stream integrity in forested biomes, which in turn ensures the delivery of aquatic ecosystem services downstream. Forest harvesting, however, can alter land-water linkages and compromise stream integrity. Although the main effects of forestry on streams have been documented, most studies have focused on short-term, post-harvest effects and used only a few (mainly abiotic) indicators. To address this, I investigated the effects of varying forest management intensities (FMIs) on different components of stream ecosystems in a holistic two-year study. In 12 catchments ranging in FMI, I measured a suite of abiotic and biotic indicators of stream ecosystem integrity to determine which explanatory catchment and reach variables were driving the observed differences. Most indicators detected the gradient in FMI, with abiotic indicators responding most strongly: streams in catchments with highest FMI tended to have higher fine inorganic sediment deposition and entrainment, water cations and carbon, DOM aromaticity and humification, and water temperature. These abiotic differences were associated with higher biofilm biomass and shredder densities, but lower leaf decomposition and contribution of algae to stream macroinvertebrate diets. Therefore, higher FMIs promoted the delivery of terrestrial water-borne materials to streams, which were incorporated into food webs. However, there were hardly signs of impaired biological communities in these 12 streams compared to data from 3 reference streams.
Fixed-width riparian buffers are used to protect stream ecosystems from forestry, but this fails to acknowledge areas with strong hydrological connectivity (variable source areas – VSAs) that may warrant special protection due to being vegetation and biogeochemical hotspots. To assess whether these hotspots have an effect on the receiving waters, I compared stream ecosystem integrity between VSA and non-VSA stream reaches in a paired study. Although I detected some differences (higher understory vegetation density, deposited organic matter, % gatherers, lower % riffles, DOC, algal biomass), I found little evidence that inputs from VSAs had significant effects on stream communities and functions.
Overall, this study demonstrates the advantages of assessing several indicators for a more holistic understanding of the linkages between forestry and streams, it shows that current management practices do not fully protect against an increased delivery of terrestrial materials derived from high FMI to streams, and calls for more studies assessing the ecological implications of VSAs.
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Living at the edge: peripheral plant populations and climate change
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by Sabine Dietz, Climate change is expected to place peripheral populations of some species at higher risk of extirpation than others, yet these populations may be significant because they may contain important evolutionary potential. Assessing the conservation significance of peripheral populations is complex, and requires an evaluation of their genetic and ecological distinctness, as well as their likely persistence (extirpation risk) in a changing climate.
To address the question of whether rear-edge populations of widespread species are genetically distinct, I used Amplified Fragment Length Polymorphisms (AFLPs) to assess genetic diversity and genetic differentiation of arctic-alpine Anemone parviflora, Dryas integrifolia and Vaccinium uliginosum in Atlantic Canada. The three species showed different genetic patterns at the rear range edge possibly associated with different dispersal capacities and phylogeographic histories. No strong predictors of genetic patterns (disjunction, distance, disturbance) could be confirmed for rear range-edge populations. Some disjunct populations of all three species maintained considerable genetic diversity.
To evaluate if rear-edge disjunct populations of A. parviflora, and D. integrifolia at Wilson Brook, NB, are at risk of extirpation from a warming climate, the microclimate
of the site was compared to local, regional and northern climates, and short-term responses of population growth to microclimatic variation were evaluated through survey and experimental approaches (Open Top Chambers). The persistence of rear-edge disjunct populations at Wilson Brook may be attributable to a cooler local microclimate. While the temperature manipulation experiment did not increase temperatures in the experimental plots as intended, there were no biologically significant associations of microclimate variables with population growth.
Species prioritization based on extinction risk assessments may not be useful for peripheral populations of widespread species, because peripheral populations need to be evaluated at the population rather than species level. I propose a framework that is based on genetic and ecological distinctness as well as extinction risk, and apply it to disjunct range-edge populations of the three species. While none of the disjunct populations were identified as of high conservation significance through this process, my research highlights the value of a population-level approach for these rear-edge disjunct populations.
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