Browsing by Author "Melin, Amanda D."

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    Chemical ecology and genetics of rough-skinned newts, Taricha granulosa
    (2020-05-15) Glass, Haley Cathleen; Vamosi, Steven M.; Theodor, Jessica M.; De Koning, A. P. Jason; Melin, Amanda D.
    Interactions between predator and prey have played a crucial role in adaptive evolutionary processes; however, phenotypic and genetic variation may also be driven by many other spatially variable biotic and abiotic factors. Rough-skinned newts, Taricha granulosa, possess a neurotoxin known as tetrodotoxin (TTX), which acts as an antipredator defense and was originally presumed to be a result of reciprocal coevolutionary interactions with resistant garter snakes across a geographic mosaic. In this thesis, I investigate several aspects of the chemical ecology and genetics of rough-skinned newts and consider how these factors play out on Vancouver Island, an interesting study region due to its isolation from mainland populations and recent non-native species introductions. By characterizing toxicity both within and among 23 populations of newts on Vancouver Island, I found significant variation in TTX and evidence for a previously unidentified hotspot, indicating selection pressures besides reciprocal coevolution may contribute to the observed patterns. Next, I present the first investigation into molecular mechanisms of tetrodotoxin expression in newts using an RNA-sequencing approach. By creating a de novo transcriptome assembly and annotation, I was able to identify novel differentially expressed genes putatively related to endogenous sources of TTX. Amphibians are also facing worldwide population declines due to factors such as negative impacts by non-native species, and Vancouver Island has experienced a recent introduction of signal crayfish and American bullfrogs. I reviewed the potential impacts of these species on rough-skinned newts and found a negative correlation between their presence and newt relative abundance, but no effect on body condition or toxicity. Using the aforementioned transcriptome assembly, I identified thousands of single nucleotide polymorphisms in 32 newts from BC and Oregon and characterized the population genetic structure at two spatial scales. Vancouver Island newts were found to belong to a cluster genetically distinct from Oregon with lower heterozygosity while displaying a lack of population structure across the island. Collectively, these results improve our understanding of the spatial variation and genetics of chemical defense in rough-skinned newts while integrating these findings with conservation implications for Vancouver Island populations.
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    Figs Are More Than Fallback Foods: The Relationship between Ficus and Cebus in a Tropical Dry Forest
    (2011-10-03) Parr, Nigel A.; Melin, Amanda D.; Fedigan, Linda Marie
    In many studies on primate feeding ecology, figs (Ficus spp.) are characterized as fallback foods, utilized only when preferred sources of food are unavailable. However, for white-faced capuchin monkeys (Cebus capucinus) living in northwestern Costa Rica, figs are a consistently important resource and may increase groupwide energy intake. We investigated whether visits to figs affect ranging and behavioural patterns of capuchins. Although daily range length and average travel speed do not differ on days when fig trees are visited, capuchins spend more time in directed travel and more time stationary on “fig days”. Capuchins also increase time spent foraging for fruit and decrease time spent foraging for invertebrates on days when figs trees are visited. Capuchins experience higher energy intake and lower energy output on “fig” days. Thus, the patterns of foraging for figs support an energy-maximization strategy and constitute an important nutritional resource for capuchins.
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    The Heterozygote Superiority Hypothesis for Polymorphic Color Vision Is Not Supported by Long-Term Fitness Data from Wild Neotropical Monkeys
    (Public Library of Science, 2014-01-03) Fedigan, Linda M.; Melin, Amanda D.; Addicott, John F.; Kawamura, Shoji
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    Intraspecific niche divergence in foraging and habitat use in wild Costa Rican capuchin monkeys
    (2019-09-20) Williamson, Rachel Elaine; Melin, Amanda D.; Fedigan, Linda Marie; Pavelka, Mary McDonald; Neuhaus, Peter
    Permanent social grouping, while rare among mammals, is routine in primates. Group-living increases intraspecific foraging competition, but niche divergence, i.e. differences in food selection and microhabitat use, may help mitigate competition. I investigated whether niche divergence occurs in wild white-faced capuchins (Cebus capucinus imitator) based on their age and/or sex classes and found that: 1) immature monkeys spent more foraging time on fruits and embedded invertebrates than adults. Females spent more time on fruits than males, but males foraged more on embedded invertebrates and difficult-to-process fruits; 2) immatures and males foraged more in the lower canopy; 3) adults and males foraged more on the forest floor; 4) immatures and females foraged more on small branches; and 5) immatures foraged more on angled branches. These results indicate that age- and sex-specific patterns are present. This likely reduces the experience of intraspecific foraging competition and may help facilitate group-living.
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    Lemur paparazzi: investigating the use of arboreal camera traps to monitor lemurs in the Kianjavato region of southeastern Madagascar
    (2020-05-12) Chen, Devin Marie; Johnson, Steig E.; Bender, Darren J.; Melin, Amanda D.
    Primate species face growing risks of extinction throughout the world. In order to better protect their populations, effective monitoring techniques are needed. This thesis examines different camera trapping methodologies as well as occupancy modeling for monitoring lemur species in Madagascar. Research took place in Kianjavato, Madagascar in reforestation areas and across five forest fragments using a system of both ground and arboreal camera traps. Arboreal cameras were significantly more likely to capture a higher lemur species richness compared to ground cameras. Likewise, an increase in camera height was an important covariate for increased detection of lemur species within occupancy models. There was no significant difference between using photograph versus video mode for trapping lemurs. Only one lemur event was captured in reforestation sites during the field season, while all nine lemur species were detected in natural forest. However, there were only enough detections in natural forest for three of the species to conduct occupancy modeling: the red-fronted brown lemur (Eulemur rufifrons), Jolly’s mouse lemur (Microcebus jollyae), and the greater dwarf lemur (Cheirogaleus major). The red-fronted brown lemur had an occupancy of 0.56, Jolly’s mouse lemur had an occupancy of 0.10, and the greater dwarf lemur had an occupancy of 0.33. Tree diameter (DBH) was an important covariate, with decreased DBH correlating with increased occupancy for Jolly’s mouse lemur and the greater dwarf lemur and increased DBH correlating with increased occupancy for the red-fronted brown lemur. Elevation was also an important covariate, with a decrease in elevation corresponding to an increase in occupancy for Jolly’s mouse lemur. Site was an important covariate for the greater dwarf lemur, with the largest forest fragment corresponding to higher occupancy. These findings show the effectiveness of arboreal camera trapping and its ability to be used for occupancy modeling for some lemur species. Future research should continue using arboreal camera traps but might have longer trapping periods to better study rarer lemur species. Overall, arboreal camera trapping is a useful method for monitoring lemurs and has the potential to be an effective tool to study arboreal primates across the globe.
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    Tree Diameter Effects on Mountain Pine Beetle Success
    (2018-06-15) Murphy, William Anthony; Reid, Mary L.; Goldblum, David; Melin, Amanda D.; Yeaman, Sam
    Habitat-seeking dispersers are faced with the challenge of finding high quality habitats while minimizing the costs incurred during habitat selection; dispersers can facilitate habitat selection by using cues emitted by their habitat. Here I investigate the habitat selection of the mountain pine beetle (MPB, Dendroctonus ponderosae), a pest insect which kills large lodgepole pine (Pinus contorta) trees during outbreaks. I measured host quality traits (phloem thickness and defensive traits) with respect to tree size as well as MPB attack and brood production. I also tested MPB orientation to two host size treatments by using baited funnel traps. Larger trees tended to be better MPB hosts. Larger trees had thick phloem and fewer to neutral defences compared to smaller trees. Larger trees were more likely to be attacked and sustained more attacks while smaller trees were nearly unattacked. After accounting for tree size, there was no evidence that MPB preferentially attacked trees with the thickest phloem or fewest defences which suggests that MPB attack the most detectable hosts rather than the highest quality hosts. Absolute brood production showed a hump-shaped relationship to tree size, suggesting that large trees may not necessarily benefit MPB offspring. More MPB were caught in large-diameter traps than small-diameter traps; however, this only occurred when the traps were paired. When traps were independent, the mean catch of both treatments was approximately equal. This work shows that larger trees tend to be better hosts for MPB but MPB do not appear to preferentially orient to large silhouettes, suggesting that visual host size information is a minor component of MPB host selection behaviour.
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    Trichromatic perception of flower colour improves resource detection among New World monkeys
    (Nature Scientific Reports, 2018-07-18) Hogan, Jeremy D.; Fedigan, Linda Marie; Hiramatsu, Chihiro; Kawamura, S.; Melin, Amanda D.
    Many plants use colour to attract pollinators, which often possess colour vision systems well-suited for detecting flowers. Yet, to isolate the role of colour is difficult, as flowers also produce other cues. The study of florivory by Neotropical primates possessing polymorphic colour vision provides an opportunity to investigate the importance of colour directly. Here we determine whether differences in colour vision within a mixed population of wild dichromatic and trichromatic white-faced capuchins (Cebus capucinus imitator) affect flower foraging behaviours. We collected reflectance data for flower foods and modelled their chromatic properties to capuchin colour vision phenotypes. We collected behavioural data over 22 months spanning four years, determined the colour vision phenotype of each monkey based on amino acid variation of the L/M opsin gene from fecal DNA, and compared foraging behaviours of dichromats and trichromats. Most flowers were more conspicuous to trichromats, and trichromats foraged in small flower patches significantly more often. These data demonstrate a difference in wild primate foraging patterns based on colour vision differences, supporting the hypothesis that trichromacy enhances detection of small, ephemeral resources. This advantage, which may also extend to other foods, likely contributes to the maintenance of colour vision polymorphism in Neotropical monkeys.