Impacts of grazing soil fauna on decomposer fungi are species-specific and density-dependent

Early-instar caterpillars experience very high and often very variable mortality; if it is density dependent, it can be a key factor in outbreak dynamics. Plant physical and chemical defenses can be extremely effective against young caterpillars, even of specialists. Phenological asynchrony with host plants can lead to dispersal and mortality in the early instars and increased predation or poor nutrition in later instars. Predation on early-instar larvae (including cannibalism) can be extremely high, parasitism appears generally low, and pathogens acquired early in larval development can lead to high mortality in later stadia. Four well-studied species reveal very different roles of early-instar mortality in population dynamics. In spruce budworm and gypsy moth, early-instar mortality rates can be very high; they do not drive outbreak cycles because density dependence is weak, but can modulate cycles and contribute to outbreak size and duration. For the autumnal moth, early-instar survival depends on host plant synchrony, but may or may not be density dependent. For monarch butterflies, the relative importance of larval mortality rates in population dynamics remains unclear. Tritrophic interactions between herbivores, host plants, natural enemies, and microbes play complex and species-specific roles in early-instar ecology, leading to emergent dynamics in population fluctuations. The phenology of these relationships is often poorly understood, making their responses to climate change unpredictable.

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Comparative analysis of phenotypic plasticity sheds light on the evolution and molecular underpinnings of locust phase polyphenism

Scientific Reports ◽

10.1038/s41598-021-91317-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Bert Foquet ◽

Adrian A. Castellanos ◽

Hojun Song

Keyword(s):

Phenotypic Plasticity ◽

Central American ◽

Reaction Norms ◽

Density Dependent ◽

Alternative Phenotypes ◽

Molecular Reaction ◽

Phase Polyphenism ◽

Highly Correlated ◽

The Individual ◽

Species Specific

AbstractLocusts exhibit one of nature’s most spectacular examples of complex phenotypic plasticity, in which changes in density cause solitary and cryptic individuals to transform into gregarious and conspicuous locusts forming large migrating swarms. We investigated how these coordinated alternative phenotypes might have evolved by studying the Central American locust and three closely related non-swarming grasshoppers in a comparative framework. By experimentally isolating and crowding during nymphal development, we induced density-dependent phenotypic plasticity and quantified the resulting behavioural, morphological, and molecular reaction norms. All four species exhibited clear plasticity, but the individual reaction norms varied among species and showed different magnitudes. Transcriptomic responses were species-specific, but density-responsive genes were functionally similar across species. There were modules of co-expressed genes that were highly correlated with plastic reaction norms, revealing a potential molecular basis of density-dependent phenotypic plasticity. These findings collectively highlight the importance of studying multiple reaction norms from a comparative perspective.

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A gene expression comparison of Trypanosoma brucei and Trypanosoma congolense in the bloodstream of the mammalian host reveals species-specific adaptations to density-dependent development

PLoS Neglected Tropical Diseases ◽

10.1371/journal.pntd.0006863 ◽

2018 ◽

Vol 12 (10) ◽

pp. e0006863 ◽

Cited By ~ 12

Author(s):

Eleanor Silvester ◽

Alasdair Ivens ◽

Keith R. Matthews

Keyword(s):

Gene Expression ◽

Trypanosoma Brucei ◽

Trypanosoma Congolense ◽

Mammalian Host ◽

Dependent Development ◽

Density Dependent ◽

Species Specific

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A multispecies aphid–ant association: density dependence and species-specific effects

Canadian Journal of Zoology ◽

10.1139/z79-066 ◽

1979 ◽

Vol 57 (3) ◽

pp. 558-569 ◽

Cited By ~ 105

Author(s):

John F. Addicott

Keyword(s):

Contingency Table Analysis ◽

Density Dependent ◽

Tapinoma Sessile ◽

Specific Effects ◽

Large Populations ◽

Table Analysis ◽

Central Rocky Mountains ◽

The Stability ◽

Species Specific ◽

Multidimensional Contingency Table

In the central Rocky Mountains of Colorado 4 species of aphids feed on fireweed, and 10 species or ants have been observed tending 3 of these species of aphids. Local populations of aphids and their associated ants were counted nondestructively at weekly intervals for up to 11 weeks. The effects of ants upon the persistence of recently initiated populations and the growth of populations during 1-week intervals were assessed by multidimensional contingency table analysis. Macrosiphum valerianae, which is not tended by ants, was affected negatively by ants. Aphis varians and A. helianthi were affected by tending, but A. salicariae was not affected. The responses of both A. varians and A. helianthi to tending were density dependent; i.e., small populations that were untended were more likely to decrease than tended populations, but large populations that were tended were either more likely to decrease than untended populations or equivalent to them. Possible reasons for this density-dependent effect are discussed, and its implications for the stability of the mutualism between aphids and ants are considered. Different species of ants had different effects. Populations of A. varians that were tended by Formica neorufibarbis or Tapinoma sessile performed no differently than untended populations, but low-density populations that were tended by F. cinerea or F. fusca were less likely to decline than untended populations.

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Describing condition-specific determinants of competition in boreal and sub-boreal mixedwood stands

The Forestry Chronicle ◽

10.5558/tfc80736-6 ◽

2004 ◽

Vol 80 (6) ◽

pp. 736-742 ◽

Cited By ~ 9

Author(s):

D. Scott Green

Keyword(s):

Best Management Practices ◽

Management Practices ◽

Management Strategies ◽

Local Environment ◽

Density Dependent ◽

Best Management ◽

Primary Growth ◽

Context Specific ◽

Species Specific ◽

Mixedwood Stands

There is a growing economic and ecological incentive in developing best-management practices for broadleaf-conifer mixedwood stands in boreal and sub-boreal regions of Western Canada. Current free-growing guidelines employed in these areas appear to be poor predictors of interactions between primary growth determinants and environmental conditions in these complex stands. Density dependent relations between broadleaf and conifer components in mixedwood stands may vary across a range of conditions due to interactions discussed in this paper between primary growth determinants (i.e., light limitations, edaphic limitations and species specific traits) and local environment. Clarifying these interactions will promote the development of adaptable tools that can be used to develop context-specific mixedwood management strategies. Key words: mixedwood management, free-growing guidelines, boreal, sub-boreal, density-dependent competition

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Density Dependent Song Duration in the Grasshopper Omocestus Viridulus

Behaviour ◽

10.1163/156853992x00345 ◽

1992 ◽

Vol 122 (1-2) ◽

pp. 121-132 ◽

Cited By ~ 4

Author(s):

Thorleifur Eiriksson

Keyword(s):

Short Form ◽

Field Studies ◽

Calling Song ◽

Density Dependent ◽

Female Response ◽

Species Specific ◽

Number Of Males

AbstractAlthough duration of grashopper song is species specific, there is also considerable variation within species. One possible reason for this is that males are adjusting their singing tactics in relation to the density of competitors. Males are expected to sing shorter songs when other males are nearby to enhance the probability of hearing female response or to listen to other males. To test this hypothesis an experiment was performed by placing different numbers of Omocestus viridulus males in large outdoor cages and monitoring their singing behaviour. The results show that males sing on average shorter calling songs as the number of males increases. It was also found that males compensate for singing shorter songs by singing more songs, so the total time spent singing stays similar at all densities. The scenario is complicated by the singing of very short songs which are mainly, but not exclusively, used in male-male interactions. The probability that males sing rivalry songs increases with the density of males and the number of these songs increases as male-male interactions get longer. The results suggests that part of the variation in the duration of calling songs reported in several field studies is caused by a change in singing tactics at different densities of males. The function of rivalry songs is not clear. These songs may function in the spacing of males or may be an extremely short form of the normal calling song used when other males are very close.

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Species-specific effects of soil fauna on fungal foraging and decomposition

Oecologia ◽

10.1007/s00442-011-2005-1 ◽

2011 ◽

Vol 167 (2) ◽

pp. 535-545 ◽

Cited By ~ 53

Author(s):

Thomas W. Crowther ◽

Lynne Boddy ◽

T. Hefin Jones

Keyword(s):

Soil Fauna ◽

Specific Effects ◽

Species Specific

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Electron Microscopy in the Study of Natural Phytoplankton Assemblages

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100119831 ◽

1985 ◽

Vol 43 ◽

pp. 620-623

Author(s):

Linda Sicko-Goad

Keyword(s):

Electron Microscopy ◽

Aquatic Environment ◽

Size Range ◽

Physical Parameters ◽

Specific Information ◽

Phytoplankton Assemblages ◽

Phytoplankton Productivity ◽

Ecosystem Effects ◽

Time Of Year ◽

Species Specific

Although the use of electron microscopy and its varied methodologies is not usually associated with ecological studies, the types of species specific information that can be generated by these techniques are often quite useful in predicting long-term ecosystem effects. The utility of these techniques is especially apparent when one considers both the size range of particles found in the aquatic environment and the complexity of the phytoplankton assemblages.The size range and character of organisms found in the aquatic environment are dependent upon a variety of physical parameters that include sampling depth, location, and time of year. In the winter months, all the Laurentian Great Lakes are uniformly mixed and homothermous in the range of 1.1 to 1.7°C. During this time phytoplankton productivity is quite low.

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