Understanding and predicting large-scale ecological responses to global environmental change requ... more Understanding and predicting large-scale ecological responses to global environmental change requires comparative studies across geographic scales with coordinated efforts and standardized methodologies. We designed, applied and assessed standardized protocols to measure tundra herbivory at three spatial scales: plot, site (habitat), and study area (landscape). The plot and site-level protocols were tested in the field during summers 2014-2015 at eleven sites, nine of them comprising warming experimental plots included in the International Tundra Experiment (ITEX). The study area protocols were assessed during 2014-2018 at 24 study areas across the Arctic. Our protocols provide comparable and easy-to-implement methods for assessing the intensity of invertebrate herbivory within ITEX plots and for characterizing vertebrate herbivore communities at larger spatial scales. We discuss methodological constraints and make recommendations for how these protocols can be used and how sampling...
ABSTRACT Fungal endophytes are species rich and ubiquitous, yet, apart from the genus Epichloë, t... more ABSTRACT Fungal endophytes are species rich and ubiquitous, yet, apart from the genus Epichloë, their ecology is largely unknown. Here we explore how herbivores affect the diversity of fungal endophytes in tundra grasslands. We assess both hyphal morphological and taxonomic diversity in grass individuals. By microscopic examination we identified endophytes to be present in all sampled grass individuals whereas identification to taxonomic units were only achieved in a subset of the individuals using laser micro dissection pressure catapulting and culturing for endophyte isolation. Hyphal morphological diversity was significantly higher in grasses exposed to grazing, along with 45 % more taxonomic units achieved. Our results suggest that grazing is an important mediator of fungal endophyte diversity in tundra grasslands. Furthermore, we suggest laser dissection of stained endophytes as a method for further exploring the ecological role of fungal endophytes.
ABSTRACT The Svalbard rock ptarmigan (Lagopus muta hyperborea) is an endemic subspecies of rock p... more ABSTRACT The Svalbard rock ptarmigan (Lagopus muta hyperborea) is an endemic subspecies of rock ptarmigan inhabiting the high Arctic archipelagos of Svalbard and Franz Josefs Land. This ptarmigan species exists at low population densities, with little interannual variations in population numbers, and limited habitat for breeding with less than 5 % of the land area in Svalbard constituting medium to high quality breeding habitat. Unander and Steen (1985) hypothesized, based on a descriptive study, that territories sufficiently attractive for breeding could be a limiting factor of the Svalbard rock ptarmigan population. Here, we use experimental data from a 3-year removal experiment (1984–1986) to test their hypothesis by comparing breeding density, demography (sex and age ratios) and body mass of birds between experimental removal plots and control locations. We found evidence of surplus birds by showing that both sexes of Svalbard rock ptarmigan replaced quickly in vacant territories after removal of the resident birds, and that breeding densities were similar for the experimental and control populations. Replaced males in the breeding population weighed less than males in the initial breeding population and tended to be younger. Experimental harvest during the preceding spring had no effect on male body mass, population sex ratio or the proportion of juvenile males in the pre-breeding population the following spring. The documented surplus of male and female Svalbard rock ptarmigan and a lack of impact on breeding densities from removal of birds leave a proportion available for harvest.
Isotopes in Environmental and Health Studies, 2014
Intraspecific competition for food is expected to increase the trophic niche width of consumers, ... more Intraspecific competition for food is expected to increase the trophic niche width of consumers, defined here as their diet diversity, but this process has been little studied in herbivores. Population densities of small rodents fluctuate greatly, providing a good study model to evaluate effects of competition on trophic niche. We studied resource use in five arctic small rodent populations of four species combining DNA metabarcoding of stomach contents and stable isotope analysis (SIA). Our results suggest that for small rodents, the most pronounced effect of competition on trophic niche is due to increased use of secondary habitats and to habitat-specific diets, rather than an expansion of trophic niche in primary habitat. DNA metabarcoding and SIA provided complementary information about the composition and temporal variation of herbivore diets. Combing these two approaches requires caution, as the underlying processes causing observed patterns may differ between methodologies due to different spatiotemporal scales.
We studied carabid beetle abundance at eight forest-farmland edges using pitfall traps across 60-... more We studied carabid beetle abundance at eight forest-farmland edges using pitfall traps across 60-m gradients (30 m into the forest, 30 m into the adjacent farmland) in southern Finland in May–August 2001. Carabid assemblages changed gradually across the studied gradients, the most drastic changes occurring right at the edge (5 m). Forest-associated carabids were often caught in farmland habitat within 20–30 m from the edges, and open-habitat carabids were also caught in the forest patches. However, these two groups responded to the edge in slightly different ways. Forest carabids were abundant all across the gradient from forest interior to the edge ( 80 m 9), while open-habitat carabids showed a drastic abundance decrease toward the forest, 5–10 m before the edge the abundance-change slope across the edge: gradient was steeper for open-habitat than for forest carabids. Wing-dimorphic and long-winged carabids increased more steeply from forest to farmland, compared to short-winged carabids. Moreover, carabids associated with dry and moist habitat showed indications of stronger response to the edge than did eurytopic species. The pair-wise comparisons between predatory/mixed-diet carabids and seed-eaters, spring and autumn breeders, and day- and night-active species did not indicate edge-response differences.
Understanding and predicting large-scale ecological responses to global environmental change requ... more Understanding and predicting large-scale ecological responses to global environmental change requires comparative studies across geographic scales with coordinated efforts and standardized methodologies. We designed, applied and assessed standardized protocols to measure tundra herbivory at three spatial scales: plot, site (habitat), and study area (landscape). The plot and site-level protocols were tested in the field during summers 2014-2015 at eleven sites, nine of them comprising warming experimental plots included in the International Tundra Experiment (ITEX). The study area protocols were assessed during 2014-2018 at 24 study areas across the Arctic. Our protocols provide comparable and easy-to-implement methods for assessing the intensity of invertebrate herbivory within ITEX plots and for characterizing vertebrate herbivore communities at larger spatial scales. We discuss methodological constraints and make recommendations for how these protocols can be used and how sampling...
ABSTRACT Fungal endophytes are species rich and ubiquitous, yet, apart from the genus Epichloë, t... more ABSTRACT Fungal endophytes are species rich and ubiquitous, yet, apart from the genus Epichloë, their ecology is largely unknown. Here we explore how herbivores affect the diversity of fungal endophytes in tundra grasslands. We assess both hyphal morphological and taxonomic diversity in grass individuals. By microscopic examination we identified endophytes to be present in all sampled grass individuals whereas identification to taxonomic units were only achieved in a subset of the individuals using laser micro dissection pressure catapulting and culturing for endophyte isolation. Hyphal morphological diversity was significantly higher in grasses exposed to grazing, along with 45 % more taxonomic units achieved. Our results suggest that grazing is an important mediator of fungal endophyte diversity in tundra grasslands. Furthermore, we suggest laser dissection of stained endophytes as a method for further exploring the ecological role of fungal endophytes.
ABSTRACT The Svalbard rock ptarmigan (Lagopus muta hyperborea) is an endemic subspecies of rock p... more ABSTRACT The Svalbard rock ptarmigan (Lagopus muta hyperborea) is an endemic subspecies of rock ptarmigan inhabiting the high Arctic archipelagos of Svalbard and Franz Josefs Land. This ptarmigan species exists at low population densities, with little interannual variations in population numbers, and limited habitat for breeding with less than 5 % of the land area in Svalbard constituting medium to high quality breeding habitat. Unander and Steen (1985) hypothesized, based on a descriptive study, that territories sufficiently attractive for breeding could be a limiting factor of the Svalbard rock ptarmigan population. Here, we use experimental data from a 3-year removal experiment (1984–1986) to test their hypothesis by comparing breeding density, demography (sex and age ratios) and body mass of birds between experimental removal plots and control locations. We found evidence of surplus birds by showing that both sexes of Svalbard rock ptarmigan replaced quickly in vacant territories after removal of the resident birds, and that breeding densities were similar for the experimental and control populations. Replaced males in the breeding population weighed less than males in the initial breeding population and tended to be younger. Experimental harvest during the preceding spring had no effect on male body mass, population sex ratio or the proportion of juvenile males in the pre-breeding population the following spring. The documented surplus of male and female Svalbard rock ptarmigan and a lack of impact on breeding densities from removal of birds leave a proportion available for harvest.
Isotopes in Environmental and Health Studies, 2014
Intraspecific competition for food is expected to increase the trophic niche width of consumers, ... more Intraspecific competition for food is expected to increase the trophic niche width of consumers, defined here as their diet diversity, but this process has been little studied in herbivores. Population densities of small rodents fluctuate greatly, providing a good study model to evaluate effects of competition on trophic niche. We studied resource use in five arctic small rodent populations of four species combining DNA metabarcoding of stomach contents and stable isotope analysis (SIA). Our results suggest that for small rodents, the most pronounced effect of competition on trophic niche is due to increased use of secondary habitats and to habitat-specific diets, rather than an expansion of trophic niche in primary habitat. DNA metabarcoding and SIA provided complementary information about the composition and temporal variation of herbivore diets. Combing these two approaches requires caution, as the underlying processes causing observed patterns may differ between methodologies due to different spatiotemporal scales.
We studied carabid beetle abundance at eight forest-farmland edges using pitfall traps across 60-... more We studied carabid beetle abundance at eight forest-farmland edges using pitfall traps across 60-m gradients (30 m into the forest, 30 m into the adjacent farmland) in southern Finland in May–August 2001. Carabid assemblages changed gradually across the studied gradients, the most drastic changes occurring right at the edge (5 m). Forest-associated carabids were often caught in farmland habitat within 20–30 m from the edges, and open-habitat carabids were also caught in the forest patches. However, these two groups responded to the edge in slightly different ways. Forest carabids were abundant all across the gradient from forest interior to the edge ( 80 m 9), while open-habitat carabids showed a drastic abundance decrease toward the forest, 5–10 m before the edge the abundance-change slope across the edge: gradient was steeper for open-habitat than for forest carabids. Wing-dimorphic and long-winged carabids increased more steeply from forest to farmland, compared to short-winged carabids. Moreover, carabids associated with dry and moist habitat showed indications of stronger response to the edge than did eurytopic species. The pair-wise comparisons between predatory/mixed-diet carabids and seed-eaters, spring and autumn breeders, and day- and night-active species did not indicate edge-response differences.
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