Density-Dependent Cannibalism in Dragonfly Nymphs (Odonata: Anisoptera) Overwintering in Temperate Freshwater Ponds

2021 ◽  
Author(s):  
Candace Clark ◽  
Thomas J Hossie ◽  
David V Beresford
Keyword(s):  
Sampling Period ◽  
Late Winter ◽  
Summer Drought ◽  
Field Surveys ◽  
Density Dependent ◽  
Size Dependent ◽  
Freshwater Ponds ◽  
Winter Conditions ◽  
Lower Oxygen ◽  
Dragonfly Nymphs

Abstract Density-dependent mortality by predation and cannibalism has been observed in aquatic insects such as dragonflies in response to shrinking habitat caused by summer drought. Winter conditions might also reduce the amount of livable habitat in temperate ponds and could augment rates of cannibalism. We hypothesized that cannibalism in dragonfly nymphs would increase in winter due to a seasonal decrease in available habitat caused by stratified lower oxygen levels leading to increased nymph density around pond edges. To determine whether cannibalism in nymphs is density-dependent and size-dependent (i.e., with smaller nymphs consumed) we experimentally manipulated nymph density in aquaria. To evaluate whether these patterns are observed in nature during the winter, we conducted field surveys for nymphs in two ponds across the fall and winter seasons. When nymphs were housed at different densities for 24 h, cannibalism was density-dependent, and only smaller nymphs were preyed upon. Our field surveys found that fewer nymphs were caught in the late winter sampling period (mixed-effects model, P < 0.001), and that these were larger than nymphs caught in the fall, although both patterns were restricted to the deeper pond (P < 0.05). Our results were consistent with the process we hypothesized, and the observed reduction in dissolved oxygen at the bottom of the deeper pond. The lack of significant changes to the relative abundance and size of nymphs in the shallower pond reveals that differences in pond characteristics can influence the degree to which winter conditions induce density-dependent cannibalism among dragonfly nymphs.

Energy allocation strategies of young temperate fish: an eco-genetic modeling approach

2015 ◽  
Vol 72 (8) ◽  
pp. 1243-1258 ◽  
Author(s):  
Lori N. Ivan ◽  
Tomas O. Höök
Keyword(s):  
Genetic Model ◽  
Energy Allocation ◽  
Genetic Models ◽  
Stabilizing Selection ◽  
Density Dependent ◽  
Size Dependent ◽  
Selective Pressures ◽  
Adaptive Processes ◽  
Overwinter Mortality ◽  
Temperate Fish

We use an individual-based eco-genetic model to explore the relative selective pressures of size-dependent predation, overwinter mortality, and density-dependent energy acquisition in structuring plastic and adaptive energy allocation during the first year of life of a temperate fish population. While several patterns emerging from a suite of eco-genetic model simulations were consistent with past theoretical models and empirical evaluations of energy allocation by young fishes, results also highlight the utility of eco-genetic models for simultaneous consideration of plastic and adaptive processes. Across simulations, variation in genetic control of energy allocation was limited during very early ontogeny when size-dependent predation pressure was particularly high. While this stabilizing selection on energy allocation diminished later in the growing season, predation, overwinter mortality, and density-dependent processes simultaneously structured energy partitioning later in ontogeny through the interactive influence of plastic and adaptive processes. Specifically, high risk of overwinter mortality and low predation selected for high prioritization of energy storage. We suggest that simulations demonstrate the utility of eco-genetic models for generating null predictions of how selective pressures may structure expression of life history traits, such as early life energy allocation.

scholarly journals Waterlogging under simulated late-winter conditions had little impact on the physiology and growth of Norway spruce seedlings

2013 ◽  
Vol 70 (8) ◽  
pp. 781-790 ◽  
Author(s):  
Ai-Fang Wang ◽  
Marja Roitto ◽  
Tarja Lehto ◽  
Janusz J Zwiazek ◽  
Mónica Calvo-Polanco ◽  
...  
Keyword(s):  
Norway Spruce ◽  
Late Winter ◽  
Winter Conditions

scholarly journals A comparative study of Calanus finmarchicus mortality patterns at five localities in the North Atlantic

2004 ◽  
Vol 61 (4) ◽  
pp. 687-697 ◽  
Author(s):  
M.D Ohman ◽  
K Eiane ◽  
E.G Durbin ◽  
J.A Runge ◽  
H.-J Hirche
Keyword(s):  
North Atlantic ◽  
Calanus Finmarchicus ◽  
Estimation Methods ◽  
Late Winter ◽  
Zooplankton Abundance ◽  
Biological Interactions ◽  
Georges Bank ◽  
Density Dependent ◽  
The North ◽  
The North Atlantic

Abstract We compare the patterns of stage-specific mortality of Calanus finmarchicus at five localities across the North Atlantic Ocean during the spring–summer period of active population growth: Georges Bank, a continental shelf locality in the NW Atlantic, based on 30 broadscale survey cruises in the US GLOBEC program; the northern North Sea, studied during the historic FLEX program with sampling four times daily for 73 days; Ocean Station M in the central Norwegian Sea, based on an 80-day daily time-series; and Lurefjorden (sampled weekly in late winter–early summer) and Sørfjorden (sampled monthly), two fjords in southwestern Norway characterized by markedly different guilds of predators. The mortality estimation methods included Wood's Population Surface Method, the Vertical Life Table (VLT) method, and a modified VLT, according to the study site and copepod recruitment schedules. Contrary to assumptions implicit in many simulation models and indirect methods for estimating zooplankton mortality, both rates and stage-specific patterns of mortality of C. finmarchicus vary appreciably across the North Atlantic. Characteristics of local environments, including the predator field in particular, appear to strongly influence mortality schedules in different regions. In at least two sites (Georges Bank and Ocean Station M), mortality rates of early stages of C. finmarchicus are density-dependent. We attribute this density-dependent mortality to egg cannibalism, which introduces non-linear population responses to changing environmental conditions. Region-specific biological interactions can substantially modify the effects of physical climate variability and render simple linear relationships between climate and zooplankton abundance unlikely.

Limiting effects of snow on seasonal habitat use and diets of caribou (Rangifer tarandus groenlandicus) on Coats Island, Northwest Territories, Canada

1988 ◽  
Vol 66 (9) ◽  
pp. 1986-1996 ◽  
Author(s):  
J. Z. Adamczewski ◽  
C. C. Gates ◽  
B. M. Soutar ◽  
R. J. Hudson
Keyword(s):  
Northwest Territories ◽  
Rangifer Tarandus ◽  
Late Winter ◽  
Winter Conditions ◽  
Winter Food ◽  
Calf Mortality ◽  
Insular Population ◽  
Rangifer Tarandus Groenlandicus ◽  
Seasonal Habitat Use ◽  
Salix Spp

The insular population of barren-ground caribou (Rangifer tarandus groenlandicus) on Coats Island, Northwest Territories, is ultimately limited by winter food resources. This study was undertaken to assess forage biomass available during summer and to determine the effects of snow on forage availability in winter. Vegetation was low in density and diversity, but provided ample forage of high quality in summer for the 2000–2500 caribou existing on the island. Aboveground green biomass averaged only 50–60 g∙m−2 in mesic and wet meadows, the most productive habitats. Caribou fed almost exclusively in meadows throughout the snow-free period; willows (Salix spp.) constituted 80–90% of rumen contents in caribou collected during the summer. Lichens were scarce and were a major food only at the beginning and end of winter. During mid and late winter, hard-packed snow averaged 4000–9000 g∙cm−2 in hardness and 50–80 cm in depth on all low-lying vegetation. Under these conditions, caribou cratered only where snow was less than 10–20 cm deep; consequently feeding was limited to the slopes of wind-blown ridges and the tops of high-centre polygons. Forage available under these winter conditions was drastically reduced in quantity and quality compared with forage available in summer. During winter 1983 – 1984, snow accumulated rapidly and prolonged deep snow cover was associated with high calf mortality.

scholarly journals Foliar photochemical processes and carbon metabolism under favourable and adverse winter conditions in a Mediterranean mixed forest, Catalonia (Spain)

2014 ◽  
Vol 11 (20) ◽  
pp. 5657-5674 ◽  
Author(s):  
D. Sperlich ◽  
C. T. Chang ◽  
J. Peñuelas ◽  
C. Gracia ◽  
S. Sabaté
Keyword(s):  
Quantum Yield ◽  
Photosystem Ii ◽  
Tree Species ◽  
Cold Period ◽  
Summer Drought ◽  
Mild Winter ◽  
Fluorescence Measurements ◽  
Winter Conditions ◽  
Evergreen Tree ◽  
Wide Range

Abstract. Evergreen trees in the Mediterranean region must cope with a wide range of environmental stresses from summer drought to winter cold. The mildness of Mediterranean winters can periodically lead to favourable environmental conditions above the threshold for a positive carbon balance, benefitting evergreen woody species more than deciduous ones. The comparatively lower solar energy input in winter decreases the foliar light saturation point. This leads to a higher susceptibility to photoinhibitory stress especially when chilly (< 12 °C) or freezing temperatures (< 0 °C) coincide with clear skies and relatively high solar irradiances. Nonetheless, the advantage of evergreen species that are able to photosynthesize all year round where a significant fraction can be attributed to winter months, compensates for the lower carbon uptake during spring and summer in comparison to deciduous species. We investigated the ecophysiological behaviour of three co-occurring mature evergreen tree species (Quercus ilex L., Pinus halepensis Mill., and Arbutus unedo L.). Therefore, we collected twigs from the field during a period of mild winter conditions and after a sudden cold period. After both periods, the state of the photosynthetic machinery was tested in the laboratory by estimating the foliar photosynthetic potential with CO2 response curves in parallel with chlorophyll fluorescence measurements. The studied evergreen tree species benefited strongly from mild winter conditions by exhibiting extraordinarily high photosynthetic potentials. A sudden period of frost, however, negatively affected the photosynthetic apparatus, leading to significant decreases in key physiological parameters such as the maximum carboxylation velocity (Vc, max), the maximum photosynthetic electron transport rate (Jmax), and the optimal fluorometric quantum yield of photosystem II (Fv/Fm). The responses of Vc, max and Jmax were highly species specific, with Q. ilex exhibiting the highest and P. halepensis the lowest reductions. In contrast, the optimal fluorometric quantum yield of photosystem II (Fv/Fm) was significantly lower in A. unedo after the cold period. The leaf position played an important role in Q. ilex showing a stronger winter effect on sunlit leaves in comparison to shaded leaves. Our results generally agreed with the previous classifications of photoinhibition-tolerant (P. halepensis) and photoinhibition-avoiding (Q. ilex) species on the basis of their susceptibility to dynamic photoinhibition, whereas A. unedo was the least tolerant to photoinhibition, which was chronic in this species. Q. ilex and P. halepensis seem to follow contrasting photoprotective strategies. However, they seemed equally successful under the prevailing conditions exhibiting an adaptive advantage over A. unedo. These results show that our understanding of the dynamics of interspecific competition in Mediterranean ecosystems requires consideration of the physiological behaviour during winter which may have important implications for long-term carbon budgets and growth trends.

scholarly journals Evidence for Sexual Recombination in Didymella tanaceti Populations, and Their Evolution Over Spring Production in Australian Pyrethrum Fields

2019 ◽  
Vol 109 (1) ◽  
pp. 155-168 ◽  
Author(s):  
Tamieka L. Pearce ◽  
Jason B. Scott ◽  
Stacey J. Pilkington ◽  
Sarah J. Pethybridge ◽  
Frank S. Hay
Keyword(s):  
Genetic Diversity ◽  
Mating Type ◽  
Sampling Period ◽  
Genotypic Diversity ◽  
Tan Spot ◽  
Late Winter ◽  
Linkage Equilibrium ◽  
Mating Types ◽  
Isolation Frequency ◽  
Sexual Recombination

Tan spot, caused by Didymella tanaceti, is one of the most important foliar diseases affecting pyrethrum in Tasmania, Australia. Population dynamics, including mating-type ratios and genetic diversity of D. tanaceti, was characterized within four geographically separated fields in both late winter and spring 2012. A set of 10 microsatellite markers was developed and used to genotype 774 D. tanaceti isolates. Isolates were genotypically diverse, with 123 multilocus genotypes (MLG) identified across the four fields. Fifty-eight MLG contained single isolates and Psex analysis estimated that, within many of the recurrent MLG, there were multiple clonal lineages derived from recombination. Isolates of both mating types were at a 1:1 ratio following clone correction in each field at each sampling period, which was suggestive of sexual recombination. No evidence of genetic divergence of isolates of each mating type was identified, indicating admixture within the population. Linkage equilibrium in two of the four field populations sampled in late winter could not be discounted following clone correction. Evaluation of temporal changes in gene and genotypic diversity identified that they were both similar for the two sampling periods despite an increased D. tanaceti isolation frequency in spring. Genetic differentiation was similar in populations sampled between the two sampling periods within fields or between fields. These results indicated that sexual reproduction may have contributed to tan spot epidemics within Australian pyrethrum fields and has contributed to a genetically diverse D. tanaceti population.

Body mass variation in semidomesticated reindeer

1994 ◽  
Vol 72 (4) ◽  
pp. 681-688 ◽  
Author(s):  
T. Helle ◽  
I. Kojola
Keyword(s):  
Body Mass ◽  
Snow Depth ◽  
Detrimental Effect ◽  
Sampling Period ◽  
Late Winter ◽  
Supplemental Feeding ◽  
Mass Variation ◽  
Finnish Lapland ◽  
Coefficients Of Variation ◽  
Insect Harassment

The between-years and within-year variation in mass of semidomesticated reindeer calves and females was studied in four herds in Finnish Lapland. Mass data covered 11–23 years. In two of the herds the intensity of supplemental feeding in mid and late winter increased throughout the sampling period, whilst in two other herds the amount of food available per capita fell drastically as a result of increased density (about 1–4 individuals/km2). Calf mass increased in both supplementally fed herds and female mass in one of them. In herds on natural ranges female mass was density dependent. Both calf mass (three herds) and female mass (one herd) correlated negatively with the number of warm days in midsummer, most likely because of severe insect harassment. The sum of snow depth during the two or three preceding winters influenced body mass inversely in one herd and positively in another herd, where snow depth probably increased the availability of arboreal lichens. The detrimental effect of warm midsummers disappeared with intensification of supplemental feeding and the resultant improvement of female condition in winter. Within-year coefficients of variation (CV) correlated negatively with mean mass for calves in all four herds and for females in one herd. For calves (two herds) and for females (one herd) CV correlated positively with the number of warm days in midsummer. We suggest that late-born calves, and females who lost body reserves in winter, were most sensitive to insect harassment.

scholarly journals Estimating Return Intervals for Extreme Climate Conditions Related to Winter Disasters and Livestock Mortality in Mongolia

2021 ◽  
Author(s):  
Masahiko Haraguchi ◽  
Nicole Davi ◽  
Mukund Rao ◽  
Caroline Leland ◽  
Masataka Watanabe ◽  
...  
Keyword(s):  
Minimum Temperature ◽  
Drought Severity ◽  
Summer Drought ◽  
Early 19Th Century ◽  
Climate Conditions ◽  
Winter Conditions ◽  
Return Levels ◽  
Drought Conditions ◽  
Winter Minimum Temperature ◽  
Winter Severity

Abstract. Mass livestock mortality events during severe winters, a phenomenon that Mongolians call dzud, cause the country significant socioeconomic problems. Dzud is an example of a compound event, meaning that multiple climatic and social drivers contribute to the risk of occurrence. Existing studies argue that the frequency and intensity of dzud are rising due to the combined effects of climate change and variability, most notably summer drought and severe winter conditions, on top of socioeconomic dynamics such as overgrazing. Summer droughts are a precondition for dzud because scarce grasses cause malnutrition, which in turn makes livestock more vulnerable to harsh winter conditions. However, these studies typically look at a short time frame (i.e., after 1940); few have investigated either the risk or the recurrence of dzud over a century-scale climate record. This study aims to fill the gaps in technical knowledge about the recurrence probability of dzud by estimating the return levels of relevant climatic variables: summer drought conditions and winter minimum temperature. We divide the country into three regions (Northwest, Southwest, and East Mongolia) based on the mortality index at the soum (county) level. For droughts, our study uses as a proxy the tree-ring reconstructed Palmer Drought Severity Index (PDSI) for three regions between 1700–2013. For winter severity, our study uses observational data of winter minimum temperature after 1901 while inferring winter minimum temperature in Mongolia from instrumental data in Siberia that extends to the early 19th century. The Generalized Extreme Value (i.e., the statistical method to infer the probability of very rare or extreme events) shows that the return levels of drought conditions are changing over time, with variability increasing for all the regions. Winter severity, however, is constant. The median 100-year return levels of the winter minimum temperature in Mongolia have been, over the past 300 years, −26.08 °C for the Southwest, −27.99 °C for the Northwest, and −25.31 °C for the East. This study thus suggests that continued summer drought would lead to increased vulnerability and malnutrition. Here, we link meteorological characteristics to socioeconomic impacts related to livestock populations and draws attention to the need for livestock index insurance.

scholarly journals Suitability of new subterranean clovers in the Canterbury region

2000 ◽  
pp. 161-165 ◽  
Author(s):  
K. Widdup ◽  
C. Pennell
Keyword(s):  
New Zealand ◽  
Seed Set ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Late Winter ◽  
Summer Drought ◽  
Seedling Regeneration ◽  
Breeding Lines ◽  
Herbage Yield ◽  
Late Maturity

The annual legume, subterranean clover, is adapted to permanent pastures in the summer drought-prone areas of eastern New Zealand. Dry summers over the last decade in Canterbury have renewed the interest from farmers in the use of sub clover. As the previously used cultivars Mt Barker and Tallarook are no longer available, a trial was established at AgResearch Templeton to evaluate a new series of cultivars and breeding lines from Australia together with recent New Zealand selections. The lines were sown in rows in May 1993 and assessed for seed set, autumn seedling regeneration and spring growth under sheep grazing for 4 years. The new Australian cultivars had improved seed set and consistently better seedling regeneration and herbage yield compared with older cultivars. The late-flowering, small-leaved and densely branched types were best adapted to the Canterbury environment. The late-maturity cultivars Denmark and Leura, selected from Sardinian germplasm, re-established 50% more seedlings and produced 25% greater late winter/ spring growth than Mt Barker and Tallarook in the third year. The New Zealand selection Ak 948 had similar performance to Denmark and Leura but the remaining selections were mediocre by the fourth year. The Sardinian ecotype breeding material appeared well-adapted to Canterbury conditions and future cultivars based on this material may be most suitable. Further trials are required in harsher sites to confirm these cultivar recommendations. Keywords: Australian cultivars, dry regions, herbage yield, seedling regeneration, subterranean clover, Trifolium subterraneum

scholarly journals “Late Winter/Early Spring” Xylem Sap Characteristics Influence Pecan Crop Load

HortScience ◽  
2014 ◽  
Vol 49 (7) ◽  
pp. 886-890 ◽  
Author(s):  
Bruce W. Wood
Keyword(s):  
Sap Flow ◽  
Xylem Sap ◽  
Sampling Period ◽  
Field Studies ◽  
Early Spring ◽  
Late Winter ◽  
Flow Volume ◽  
Alternate Bearing ◽  
Simple Carbohydrates ◽  
Individual Trees

Alternate bearing (AB) by individual trees is a major biological problem faced by pecan [Carya illinoinensis (Wangenh.) K. Koch] nut producers. The linkage between flowering and subsequent cropload with xylem sap characteristics at the time of floral bud swelling and expansion is unknown. Multiyear field studies of mature ‘Cheyenne’ and ‘Moneymaker’ trees, in “on” or “off” phases of AB, were evaluated regarding this linkage. Xylem sap flowing from trunks of ‘Cheyenne’ trees just before, and at the time of, budbreak (i.e., “late winter/early spring”) consisted of a variety of simple sugars. These were hexoses (fructose and glucose), a disaccharide (sucrose), polysaccharides (raffinose and stachyose), and sugar alcohols (xylitol and sorbitol). Sucrose was the overwhelmingly dominant simple carbohydrate at this growth stage, comprising 55% to 75% of the total molar composition, regardless of tree bearing status or sampling time during the seasonal transition from late winter to early spring as buds swell, break, and begin to produce shoots and flowers. Both sap flow volume and concentration of individual carbohydrates were much greater in “on” phase than “off” phase trees. “On” phase xylem sap contained ≈19.9-fold more sucrose than sap from “off” phase trees. The concentration of all sap carbohydrates was much greater at flow inception, declining quickly as buds transition from “bud swell” to “budbreak” and subsequent “shoot growth.” Depending on crop year, individual “on” phase ‘Cheyenne’ trees (≈25 years old) exhibited flow volumes 5.5- to 20.2-fold greater than “off” phase trees. In-shell nut yield by both ‘Cheyenne’ and ‘Moneymaker’ trees (110 years old) increased hyperbolically with increasing “late winter/early spring” sap flow volume. Sap flow from ‘Cheyenne’ and ‘Moneymaker’ resulted in near maximum nut yield when flow volume per xylem tap peaked was at ≈10 L/tree and ≈15 L/tree, respectively, over a 16-day sampling period. These findings are suggestive that sucrose, and possibly other simple carbohydrates, moving acropetally toward axillary bud meristems of shoots during “late winter/early spring” at about the time of “bud swelling” influences the final phase of floral development and therefore subsequent cropload.

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