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Jean-louis Martin - One of the best experts on this subject based on the ideXlab platform.
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Deer slow down litter decomposition by reducing litter quality in a temperate forest
Ecology, 2020Co-Authors: Simon Chollet, Morgane Maillard, Juliane Schorghuber, Susan J Grayston, Jean-louis MartinAbstract:Litter decomposition is a key process that allows the recycling of nutrients within ecosystems. In temperate forests the role of large herbivores in litter decomposition remains a subject of debate. To address this question, we used two litterbag experiments in a quasi-experimental situation resulting from the introduction of Sitka Black-Tailed Deer Odocoileus hemionus sitkensis on forested islands of Haida Gwaii (Canada). We investigated the two main pathways by which Deer could modify litter decomposition: change in litter quality and modification of decomposer communities. We found that Deer presence significantly reduced litter mass loss after one year, mainly through a reduction in litter quality. This mass loss reflected a 30 and 28 % lower loss of carbon (C) and nitrogen (N), respectively. The presence of Deer also reduced the ability of decomposers to breakdown carbon, but not nitrogen. Indeed, litter placed on an island with Deer lost 5% less carbon after one year of decomposition than did litter decomposing on an island without Deer. This loss in ability to decompose litter in presence of Deer was outweighed by the differences in mass loss associated with the effect of Deer on litter quality. Additional effects of feces deposition by Deer on the decomposition process were also significant but minor. These results suggest that the effects continental-scale dramatic increases in Deer populations may have on broad-scale patterns of C and N cycling deserve closer attention.
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Deer slow down litter decomposition by reducing litter quality in a temperate forest
bioRxiv, 2019Co-Authors: Simon Chollet, Morgane Maillard, Juliane Schorghuber, Susan J Grayston, Jean-louis MartinAbstract:In temperate forest ecosystems, the role of Deer in litter decomposition, a key nutrient cycling process, remains debated. Deer may modify the decomposition process by affecting plant cover and thus modifying litter abundance. They can also alter litter quality through differential browsing and affect decomposer ability by changing soil abiotic properties and the nature of decomposer communities. We used two litterbag experiments in a quasi-experimental situation resulting from the introduction of Sitka Black-Tailed Deer Odocoileus odocoileus sitkensis on forested islands of Haida Gwaii (Canada). We investigated the effects of Deer on decomposition through their impacts on litter quality and on decomposer ability. After one year, the effect of Deer on litter quality resulted in a lower rate of mass loss in litter from litterbags. This mass loss mainly reflected a 21 and 38 % lower rate of carbon (C) and nitrogen (N) loss, respectively. Presence of Deer resulted in lower decomposer ability for the rate of carbon loss, but not for nitrogen loss. The level of C loss after one year was 5% higher for litter decomposing on an island without Deer. But the change in the rate of carbon loss explained by the effect of Deer on decomposer ability was outweighed by the effect Deer had on litter quality. Additional effects of Deer on the decomposition process through feces deposition were significant but minor. These results question the role the large increase in Deer populations observed in temperate forests at continental scales may play in broad scale patterns of C and N cycling.
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innate threat sensitive foraging black tailed Deer remain more fearful of wolf than of the less dangerous black bear even after 100 years of wolf absence
Oecologia, 2014Co-Authors: Simon Chamaillejammes, Helene Malcuit, Soizic Le Saout, Jean-louis MartinAbstract:Anti-predator behaviors often entail foraging costs, and thus prey response to predator cues should be adjusted to the level of risk (threat-sensitive foraging). Simultaneously dangerous predators (with high hunting success) should engender the evolution of innate predator recognition and appropriate anti-predator behaviors that are effective even upon the first encounter with the predator. The above leads to the prediction that prey might respond more strongly to cues of dangerous predators that are absent, than to cues of less dangerous predators that are actually present. In an applied context this would predict an immediate and stronger response of ungulates to the return of top predators such as wolves (Canis lupus) in many parts of Europe and North America than to current, less threatening, mesopredators. We investigated the existence of innate threat-sensitive foraging in Black-Tailed Deer. We took advantage of a quasi-experimental situation where Deer had not experienced wolf predation for ca. 100 years, and were only potentially exposed to black bears (Ursus americanus). We tested the response of Deer to the urine of wolf (dangerous) and black bear (less dangerous). Our results support the hypothesis of innate threat-sensitive foraging with clear increased passive avoidance and olfactory investigation of cues from wolf, and surprisingly none to black bear. Prey which have previously evolved under high risk of predation by wolves may react strongly to the return of wolf cues in their environments thanks to innate responses retained during the period of predator absence, and this could be the source of far stronger non-consumptive effects of the predator guild than currently observed.
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introduced Deer and the pollination and reproduction of an animal pollinated herb
Botany, 2010Co-Authors: Diego P Vazquez, Julie Gresserj Gresser, Jean-louis MartinAbstract:We evaluated the hypothesis that the modified population density of Aquilegia formosa Fisch. ex DC. (Ranunculaceae) resulting from the introduction of Sitka Black-Tailed Deer (Odocoileus hemionus sitkensis) in the Haida Gwaii archipelago affects the pollination and reproductive performance of this herbaceous species. We compared the population density, pollination, and reproductive success of A. formosa among three small islands colonized by Deer and three Deer-free islands. Islands with Deer had a substantially lower absolute density and a greater relative density of A. formosa than Deer-free islands. The presence of Deer was associated with higher pollen deposition, which probably resulted from the greater relative density of A. formosa on islands with Deer. However, the presence of Deer had no significant effect on individual reproductive success. The latter result is likely a consequence of the lack of pollen limitation in this species, as well as of the conflicting relationship between the absolute a...
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top down and bottom up consequences of unchecked ungulate browsing on plant and animal diversity in temperate forests lessons from a Deer introduction
Biological Invasions, 2010Co-Authors: Jean-louis Martin, Stephen A Stockton, Sylvain Allombert, Anthony J GastonAbstract:Debate on the relative importance of competition for resources and trophic interactions in shaping the biological diversity of living communities remains unsettled after almost a century. Recently, dramatic increases in ungulate populations have provided a useful quasi-experiment on the effects of unrestrained ungulates on forest ecology. The islands of Haida Gwaii (Canada) offer a unique situation to investigate the potential of large herbivores to control temperate forest community structure and diversity. Black-Tailed Deer Odocoileus hemionus Merriam, native to adjacent mainland areas of British Columbia, were introduced in 1878 and spread to all but a few islands. Because Deer were not native to the archipelago, islands that still lack Deer provide a rare instance of temperate forest vegetation and fauna that developed in the absence of large herbivores. The colonisation of different islands at different times, and the absence of significant predation allow us to assess whether and how a large herbivore can exert “top-down” control on vegetation and its associated fauna. We studied plant communities in forest interior and shoreline, on seven small islands of varying browse history. Three islands were untouched by Deer, Deer had been resident for about 15 years on two, and on another two Deer had been present for more than 50 years. Without Deer, vegetation in the understorey and/or shrub layer was dense or very dense. Structure and composition varied markedly within and between shoreline and interior communities. Without Deer, shoreline communities were dominated by species absent from islands with Deer. Where Deer had been present for less than 20 years most plant species characteristic of shorelines on islands without Deer were already absent or scarce, but in the forest interior species richness was less affected and extensive shrub thickets remained. On islands where Deer had been present for >50 years vegetation below the browse line was extremely simplified, converging in both forest interior and shoreline towards an open assemblage of a few Deer-tolerant species, basically two coniferous trees. This top down effect on the plant community reflected up the food chain so that understorey invertebrate and shrub-dependent songbird communities became simplified. In contrast, species densities of litter arthropods (especially weevils and millipedes) were highest where Deer were present for >50 years. Canopy birds were unaffected by Deer presence. In the absence of predators, major climatic stress or other means to control the herbivore, Deer browsing created greatly simplified plant and animal communities.
Eric P. Hoberg - One of the best experts on this subject based on the ideXlab platform.
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A cryptic species of Onchocerca (Nematoda: Onchocercidae) in blackflies (Simulium spp.) from southern California, USA.
Parasites & vectors, 2018Co-Authors: Guilherme G. Verocai, Kimberly J. Nelson, R. Trey Callahan, Joseph Wakoli Wekesa, Hassan K. Hassan, Eric P. HobergAbstract:Entomological surveillance for pathogens based on molecular screening of putative arthropod vectors such as blackflies (Diptera: Simuliidae) is becoming increasingly important. Surveillance provides a means to understand host and geographical patterns of underestimated biodiversity among North American species of Onchocerca and a pathway to identify and track expanding emergence of the zoonotic Onchocerca lupi. Herein, we have screened two blackfly species, Simulium tescorum and Simulium vittatum (s.l.), from Los Angeles County, southern California, USA for DNA of filarioid nematodes to better understand species richness and limits within the genus Onchocerca. A total of 1056 and 378 female blackflies was collected using CO2-baited mosquito traps from March to November of 2015 and 2016, respectively. All blackflies during 2015 were individually processed for DNA extraction and PCR targeting of the cytochrome c oxidase subunit 1 (cox1) of the mitochondrial DNA (mtDNA). Specimens of S. tescorum collected in 2016 were processed individually with heads and bodies extracted separately, whereas those of S. vittatum (s.l.) were processed in pooled samples with heads and bodies extracted separately. A subset of filarioid-positive samples from 2015 and all samples from 2016 were screened using a PCR targeting the NADH dehydrogenase subunit 5 (nad5) gene (mtDNA). In 2015, 356 S. tescorum (33.7%) and 683 S. vittatum (s.l.) (64.7%) were collected, and an additional 17 specimens were not assessed morphologically. In 2016, a total of 378 blackflies was collected. Of these, 43 (11.6%) were S. tescorum and 327 (88.4%) were S. vittatum (s.l.), and an additional 8 specimens were not assessed morphologically. In 2015, Onchocerca sequences were detected in 4.8% (n = 17) of S. tescorum samples, and only one S. vittatum (0.15%). In 2016, only a single S. vittatum pool was positive for the same cryptic Onchocerca species. In phylogenetic comparisons based on nad5, the Onchocerca sequences from California formed a clade with those isolates in white-tailed Deer from upstate New York, suggesting these belong to a single widespread cryptic species. An uncharacterized species of Onchocerca associated with cervid hosts was found in blackflies from southern California. Sequence data demonstrated it is likely conspecific with an unnamed species of Onchocerca previously found in white-tailed Deer from upstate New York. Current data support recognition of a broad geographical distribution across North America for an apparently cryptic species of Onchocerca that is discrete from O. cervipedis, considered to be a typical filarioid among cervids. Our data suggest that this cryptic species of Onchocerca may infect subspecies of white-tailed Deer (Odocoileus virginianus), and mule and Black-Tailed Deer (Odocoileus hemionus) at temporal latitudes. The blackflies Simulium tescorum and S. vittatum (s.l.) (presumably, S. tribulatum) are putative vectors. Discovery of a cryptic complex indicates that species diversity and putative associations for definitive hosts and vectors of Onchocerca species in North America must be reassessed.
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A cryptic species of Onchocerca (Nematoda: Onchocercidae) in blackflies (Simulium spp.) from southern California, USA
Parasites & Vectors, 2018Co-Authors: Guilherme G. Verocai, Kimberly J. Nelson, R. Trey Callahan, Joseph Wakoli Wekesa, Hassan K. Hassan, Eric P. HobergAbstract:Background Entomological surveillance for pathogens based on molecular screening of putative arthropod vectors such as blackflies (Diptera: Simuliidae) is becoming increasingly important. Surveillance provides a means to understand host and geographical patterns of underestimated biodiversity among North American species of Onchocerca and a pathway to identify and track expanding emergence of the zoonotic Onchocerca lupi . Herein, we have screened two blackfly species, Simulium tescorum and Simulium vittatum ( s.l .), from Los Angeles County, southern California, USA for DNA of filarioid nematodes to better understand species richness and limits within the genus Onchocerca . Methods A total of 1056 and 378 female blackflies was collected using CO_2-baited mosquito traps from March to November of 2015 and 2016, respectively. All blackflies during 2015 were individually processed for DNA extraction and PCR targeting of the cytochrome c oxidase subunit 1 ( cox 1) of the mitochondrial DNA (mtDNA). Specimens of S. tescorum collected in 2016 were processed individually with heads and bodies extracted separately, whereas those of S. vittatum ( s.l .) were processed in pooled samples with heads and bodies extracted separately. A subset of filarioid-positive samples from 2015 and all samples from 2016 were screened using a PCR targeting the NADH dehydrogenase subunit 5 ( nad 5) gene (mtDNA). Results In 2015, 356 S. tescorum (33.7%) and 683 S. vittatum ( s.l .) (64.7%) were collected, and an additional 17 specimens were not assessed morphologically. In 2016, a total of 378 blackflies was collected. Of these, 43 (11.6%) were S. tescorum and 327 (88.4%) were S. vittatum ( s.l .), and an additional 8 specimens were not assessed morphologically. In 2015, Onchocerca sequences were detected in 4.8% ( n = 17) of S. tescorum samples, and only one S. vittatum (0.15%). In 2016, only a single S. vittatum pool was positive for the same cryptic Onchocerca species. In phylogenetic comparisons based on nad 5, the Onchocerca sequences from California formed a clade with those isolates in white-tailed Deer from upstate New York, suggesting these belong to a single widespread cryptic species. Conclusions An uncharacterized species of Onchocerca associated with cervid hosts was found in blackflies from southern California. Sequence data demonstrated it is likely conspecific with an unnamed species of Onchocerca previously found in white-tailed Deer from upstate New York. Current data support recognition of a broad geographical distribution across North America for an apparently cryptic species of Onchocerca that is discrete from O. cervipedis , considered to be a typical filarioid among cervids. Our data suggest that this cryptic species of Onchocerca may infect subspecies of white-tailed Deer ( Odocoileus virginianus ), and mule and Black-Tailed Deer ( Odocoileus hemionus ) at temporal latitudes. The blackflies Simulium tescorum and S. vittatum ( s.l .) (presumably, S. tribulatum ) are putative vectors. Discovery of a cryptic complex indicates that species diversity and putative associations for definitive hosts and vectors of Onchocerca species in North America must be reassessed.
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geographic distribution of the muscle dwelling nematode parelaphostrongylus odocoilei in north america using molecular identification of first stage larvae
Journal of Parasitology, 2005Co-Authors: Emily J Jenkins, Eric P. Hoberg, Greg D Appleyard, Benjamin M Rosenthal, Susan J Kutz, Alasdair Veitch, Helen M Schwantje, Brett Elkin, Lydden PolleyAbstract:Molecular identification of dorsal-spined larvae (DSL) from fecal samples indicates that the protostrongylid parasite Parelaphostrongylus odocoilei occupies a broader geographic range in western North America than has been previously reported. We analyzed 2,124 fecal samples at 29 locations from thinhorn sheep (Ovis dalli dalli and O. d. stonei), bighorn sheep (Ovis canadensis canadensis and O. c. californiana), mountain goats (Oreamnos americanus), woodland caribou (Rangifer tarandus caribou), mule Deer (Odocoileus hemionus hemionus), and Black-Tailed Deer (O. h. columbianus). The DSL were recovered from populations of thinhorn sheep south, but not north, of the Arctic Circle, and they were not recovered from any of the bighorn sheep populations that we examined. In total, DSL were recovered from 20 locations in the United States and Canada (Alaska, Yukon Territory, Northwest Territories, British Columbia, Alberta, and California). The DSL were identified as P. odocoilei by comparing sequences of the second internal transcribed spacer (ITS2) region of ribosomal RNA among 9 protostrongylid species validated by adult comparative morphology. The ITS2 sequences were markedly different between Parelaphostrongylus and other protostrongylid genera. Smaller fixed differences served as diagnostic markers for the 3 species of Parelaphostrongylus. The ITS2 sequences (n = 60) of P. odocoilei were strongly conserved across its broad geographic range from California to Alaska. Polymorphism at 5 nucleotide positions was consistent with multiple copies of the ITS2 within individual specimens of P. odocoilei. This work combines extensive fecal surveys, comparative morphology, and molecular diagnostic techniques to describe comprehensively the host associations and geographic distribution of a parasitic helminth.
Emily K Latch - One of the best experts on this subject based on the ideXlab platform.
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range wide analysis of genetic structure in a widespread highly mobile species odocoileus hemionus reveals the importance of historical biogeography
Molecular Ecology, 2014Co-Authors: Emily K Latch, James R Heffelfinger, Dawn M Reding, Carlos H Alcalagalvan, Olin E RhodesAbstract:Highly mobile species that thrive in a wide range of habitats are expected to show little genetic differentiation across their range. A limited but growing number of studies have revealed that patterns of broad-scale genetic differentiation can and do emerge in vagile, continuously distributed species. However, these patterns are complex and often shaped by both historical and ecological factors. Comprehensive surveys of genetic variation at a broad scale and at high resolution are useful for detecting cryptic spatial genetic structure and for investigating the relative roles of historical and ecological processes in structuring widespread, highly mobile species. In this study, we analysed 10 microsatellite loci from over 1900 samples collected across the full range of mule Deer (Odocoileus hemionus), one of the most widely distributed and abundant of all large mammal species in North America. Through both individual- and population-based analyses, we found evidence for three main genetic lineages, one corresponding to the ‘mule Deer’ morphological type and two to the ‘Black-Tailed Deer’ type. Historical biogeographic events likely are the primary drivers of genetic divergence in this species; boundaries of the three lineages correspond well with predictions based on Pleistocene glacial cycles, and substructure within each lineage demonstrates island vicariance. However, across large geographic areas, including the entire mule Deer lineage, we found that genetic variation fit an isolation-by-distance pattern rather than discrete clusters. A lack of genetic structure across wide geographic areas of the continental west indicates that ecological processes have not resulted in restrictions to gene flow sufficient for spatial genetic structure to emerge. Our results have important implications for our understanding of evolutionary mechanisms of divergence, as well as for taxonomy, conservation and management.
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identification of novel single nucleotide polymorphisms snps in Deer odocoileus spp using the bovinesnp50 beadchip
PLOS ONE, 2012Co-Authors: Gwilym D Haynes, Emily K LatchAbstract:Single nucleotide polymorphisms (SNPs) are growing in popularity as a genetic marker for investigating evolutionary processes. A panel of SNPs is often developed by comparing large quantities of DNA sequence data across multiple individuals to identify polymorphic sites. For non-model species, this is particularly difficult, as performing the necessary large-scale genomic sequencing often exceeds the resources available for the project. In this study, we trial the Bovine SNP50 BeadChip developed in cattle (Bos taurus) for identifying polymorphic SNPs in cervids Odocoileus hemionus (mule Deer and Black-Tailed Deer) and O. virginianus (white-tailed Deer) in the Pacific Northwest. We found that 38.7% of loci could be genotyped, of which 5% (n=1068) were polymorphic. Of these 1068 polymorphic SNPs, a mixture of putatively neutral loci (n=878) and loci under selection (n=190) were identified with the FST-outlier method. A range of population genetic analyses were implemented using these SNPs and a panel of 10 microsatellite loci. The three types of Deer could readily be distinguished with both the SNP and microsatellite datasets. This study demonstrates that commercially developed SNP chips are a viable means of SNP discovery for non-model organisms, even when used between very distantly related species (the Bovidae and Cervidae families diverged some 25.1230.1 million years before present).
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hybrid swarm between divergent lineages of mule Deer odocoileus hemionus
Molecular Ecology, 2011Co-Authors: Emily K Latch, James R Heffelfinger, Elizabeth M Kierepka, E Olin J R RhodesAbstract:Studies of hybrid zones have revealed an array of evolutionary outcomes, yet the underlying structure is typically characterized as one of three types: a hybrid zone, a hybrid swarm or a hybrid taxon. Our primary objective was to determine which of these three structures best characterizes a zone of hybridization between two divergent lineages of mule Deer (Odocoileus hemionus), mule Deer and Black-Tailed Deer. These lineages are morphologically, ecologically and genetically distinct, yet hybridize readily along a zone of secondary contact between the east and west slopes of the Cascade Mountains (Washington and Oregon, USA). Using microsatellite and mitochondrial DNA, we found clear evidence for extensive hybridization and introgression between lineages, with varying degrees of admixture across the zone of contact. The pattern of hybridization in this region closely resembles a hybrid swarm; based on data from 10 microsatellite loci, we detected hybrids that extend well beyond the F1 generation, did not detect linkage disequilibrium at the centre of the zone and found that genotypes were associated randomly within the zone of contact. Introgression was characterized as bidirectional and symmetric, which is surprising given that the zone of contact occurs along a sharp ecotone and that lineages are characterized by large differences in body size (a key component of mating success). Regardless of the underlying mechanisms promoting hybrid swarm maintenance, it is clear that the persistence of a hybrid swarm presents unique challenges for management in this region.
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species wide phylogeography of north american mule Deer odocoileus hemionus cryptic glacial refugia and postglacial recolonization
Molecular Ecology, 2009Co-Authors: Emily K Latch, James R Heffelfinger, Jennifer A Fike, Olin E RhodesAbstract:: Quaternary climatic oscillations greatly influenced the present-day population genetic structure of animals and plants. For species with high dispersal and reproductive potential, phylogeographic patterns resulting from historical processes can be cryptic, overshadowed by contemporary processes. Here we report a study of the phylogeography of Odocoileus hemionus, a large, vagile ungulate common throughout western North America. We examined sequence variation of mitochondrial DNA (control region and cytochrome b) within and among 70 natural populations across the entire range of the species. Among the 1766 individual animals surveyed, we recovered 496 haplotypes. Although fine-scale phylogenetic structure was weakly resolved using phylogenetic methods, network analysis clearly revealed the presence of 12 distinct haplogroups. The spatial distribution of haplogroups showed a strong genetic discontinuity between the two morphological types of O. hemionus, mule Deer and Black-Tailed Deer, east and west of the Cascade Mountains in the Pacific Northwest. Within the mule Deer lineage, we identified several haplogroups that expanded before or during the Last Glacial Maximum, suggesting that mule Deer persisted in multiple refugia south of the ice sheets. Patterns of genetic diversity within the Black-Tailed Deer lineage suggest a single refugium along the Pacific Northwest coast, and refute the hypothesis that Black-Tailed Deer persisted in one or more northern refugia. Our data suggest that Black-Tailed Deer recolonized areas in accordance with the pattern of glacial retreat, with initial recolonization northward along a coastal route and secondary recolonization inland.
Gwenaël Vourc'h - One of the best experts on this subject based on the ideXlab platform.
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Monoterpene Effect on Feeding Choice by Deer
Journal of Chemical Ecology, 2002Co-Authors: Gwenaël Vourc'h, Alice Labbé, Dimitri Rosolowski, Jean-louis Martin, Michel De Garine-wichatitsky, Herve FritzAbstract:A previous study showed that Sitka Black-Tailed Deer ( Odocoileus hemionus sitkensis ) consumption was negatively correlated with monoterpene content in western redcedar ( Thuja plicata ). To test whether these monoterpenes were deterrent to Sitka Black-Tailed Deer, we performed feeding choice experiments with four hydrocarbon (sabinene, myrcene, α-pinene, and d + l -limonene) and one oxygenated (α,β-thujone) monoterpene solution at their highest natural concentration in western redcedar foliage. To test whether Deer response was species specific, we ran similar experiments on European roe Deer ( Capreolus capreolus ) and rusa Deer ( Cervus timorensis russa ). In all experiments, monoterpenes were repellent. Solutions with α,β-thujone, the major monoterpene in redcedar leaves, were the most repellent of the solutions tested. We then analyzed how Black-Tailed and roe Deer responded to (1) an increase in concentration of the monoterpenes with the weakest repellent effects (hydrocarbon monoterpenes) and (2) a decrease in concentration of the monoterpene with strongest effect (α,β-thujone). Repellency tended to increase with concentration for hydrocarbon monoterpenes, but remained strong for α,β-thujone. As wild Deer regularly feed on plants containing monoterpenes, this raises the question as to how the animals deal with these molecules.
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Disentangling the causes of damage variation by Deer browsing on young Thuja plicata
Oikos, 2002Co-Authors: Gwenaël Vourc'h, Herve Fritz, Bruno Vila, Dominique Gillon, Frederic Guibal, José Escarré, Thomas P. Clausen, Jean-louis MartinAbstract:Long-lived trees experience different levels of damage due to mammalian herbivores. To untangle the mechanisms that underlie this variation, we combined chemical with dendrochronological analyses to study variation in browsing on Western redcedars (Thuja plicata) on Haida Gwaii (British Columbia, Canada). Since the last glaciation, Haida Gwaii forests had lacked large herbivore browser until Sitka Black-Tailed Deer (Odocoileus hemionus sitkensis) were introduced at the beginning of the 20th century. Dendrochronology yielded information on radial growth and plant annual responses to environmental stresses including herbivory. Secondary metabolite content and plant nutritional quality provided insights into proximate causes of food choices made by herbivores. We sampled lightly- and heavily-browsed young trees at four sites: three clear-cut sites with high browsing pressure and one old-growth forest site where browsing pressure had, until recently, been lower. Heavily-browsed young trees had lower concentrations of secondary metabolites and were of lower nutritive value than lightly-browsed trees at all sites. Under high browsing pressure, tree growth patterns suggested that all young trees were initially severely browsed until some trees, currently scored as lightly-browsed, started to escape Deer. At the old-growth site, both lightly- and heavily-browsed trees tended to have lower overall average secondary metabolite concentrations than those of all other sites, a trend possibly related to greater canopy closure. Lightly-browsed trees were older than heavilybrowsed ones which resulted, during the period of lower browsing pressure, in higher growth rate and a same pattern of change in growth from one year to the next year. This suggests that, under low browsing pressure, selection of young trees related to chemical defense was weak and that growth differences due to other factors than browsing could be expressed. Under strong browsing pressure, however, all young trees had equally low growth rates until trees with better genetic potential to produce effective defenses were able to escape Deer. This suggests that selection by Deer could occur on a long-lived tree.
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Defensive adaptations of Thuja plicata to ungulate browsing: a comparative study between mainland and island populations
Oecologia, 2001Co-Authors: Gwenaël Vourc'h, Jean-louis Martin, Patrick Duncan, José Escarré, Thomas P. ClausenAbstract:Forests on the Haida Gwaii (HG) archipelago (British Columbia, Canada) evolved for about 10,000 years in the absence of large-mammal browsing. The introduction of Black-Tailed Deer (Odocoileus hemionus sitkensis) from the mainland prior to 1901 provides an opportunity to evaluate changes in the adaptive defensive responses of plants to herbivory. We compared (1) food choice by Deer and (2) chemical defence (terpene concentrations) between HG and mainland red cedars (Thuja plicata) using (1) nursery-grown seedlings never exposed to Deer, (2) branches from trees that grew before the introduction of Deer (“old trees”) and (3) saplings exposed to Deer herbivory on the mainland and on HG. We used the first two plant categories to test the hypothesis that plants that evolve under low herbivory levels have lower anti-herbivore defences. We used saplings to study the consequences of the dramatic increase in browsing on HG. During food experiments, Deer preferred HG seedlings and old tree branches compared to those from the mainland. Total monoterpene concentrations were much higher than diterpene concentrations in all plant categories. Within plant categories, multivariate analysis showed that terpene profiles differed significantly between HG and mainland red cedars: HG seedlings and old trees had lower monoterpene levels. These results suggest that some monoterpenes may be determinants of Deer food choice and that the defences of HG plants are less effective than those of mainland plants. The Deer used branches from HG and mainland saplings indiscriminately. However, terpene profiles differed significantly between HG and mainland saplings, with multivariate analysis suggesting a higher defensive response in browsed HG saplings. Monoterpene profiles were different in lightly and heavily browsed saplings from HG, suggesting that under the current browsing regime, individuals with the greatest constitutive defences, or with greatest potential for induced defences, grow better and are selected on HG.
Heiko U Wittmer - One of the best experts on this subject based on the ideXlab platform.
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seasonal variation in the feeding ecology of pumas puma concolor in northern california
Canadian Journal of Zoology, 2014Co-Authors: Maximilian L Allen, L M Elbroch, David S Casady, Heiko U WittmerAbstract:Direct effects of predators depend upon factors that can vary across seasons, including variations in the abundance and vulnerability of migrating prey. Past studies show conflicting results of whether puma (Puma concolor (L., 1771)) feeding ecology varies among seasons. We employed GPS collars to study puma feeding ecology in a single-prey system with migratory Black-Tailed Deer (Odocoileus hemionus columbianus (Richardson, 1829)). We hypothesized that puma feeding ecology would vary based on changes in prey abundance and spatial distribution, as well as competition with scavengers and decomposers. Our results supported these hypotheses. Kill rates in number of ungulates/week were significantly higher in summer and autumn than in winter, likely owing to the increased availability and density of Black-Tailed Deer fawns. The handling times of blacktailed Deer ≥1 year old were significantly higher in winter than in spring, summer, or autumn. We speculated that reduced handling time in summer may have been influenced by black bear (Ursus americanus Pallas, 1780) kleptoparasitism and the decomposition of kills. Pumas killed Black-Tailed Deer at higher elevations in summer than in winter, spring, or autumn, and the elevations correlated significantly with seasonal elevations used by Black-Tailed Deer, suggesting that pumas exhibited seasonal foraging behaviours and tracked prey availability in a system with migrating prey.
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a review of the population dynamics of mule Deer and black tailed Deer odocoileus hemionus in north america
Mammal Review, 2013Co-Authors: Tavis Forrester, Heiko U WittmerAbstract:Mule Deer and Black-Tailed Deer Odocoileus hemionus have exhibited marked population fluctuations throughout their range over the past century. The relative contributions of predation, forage availability and weather to observed population changes remain unclear and controversial. We reviewed 48 studies on Odocoileus hemionus survival and predation from the past 30 years and quantified age-specific vital rates, population growth rates (λ) and causes of mortality. We also evaluated the effect of environmental variables on variation in vital rates and the contribution of age-specific survival to population growth. Age-specific survival (ϕ) was the most frequently studied population parameter. Odocoileus hemionus have lower and more variable fawn survival than other ungulate species (ϕsummer = 0.44, CV = 0.42; ϕannual = 0.29, CV = 0.67). Adult female survival conversely appeared to be high and stable throughout the geographical range of the species (ϕannual = 0.84, CV = 0.06). Observed low fawn survival appears to be compensated for by high fecundity rates. Predation was the primary proximate cause of mortality for all age classes, and was an important source of summer fawn mortality and of mortality in multi-prey, multi-predator systems. However, predator removal studies suggest that predation is compensatory, particularly at high Deer densities, and that nutrition and weather shape population dynamics. We propose three models to explain local population dynamics of Odocoileus hemionus: (i) populations are limited by forage availability and weather; (ii) adult females are limited by forage availability, fawns are limited by forage availability and predation, and population growth is constrained by fecundity and fawn predation; and (iii) large changes in the abundance of predators or alternative prey change predation risk and destabilize population dynamics. Future research should be focused on: the effects of age-specific survival on population growth; possible interactions between predation, forage availability and weather; and the importance of multiple predator and prey species in shaping the population dynamics of Odocoileus hemionus.