scholarly journals Trait-similarity and trait-hierarchy jointly determine co-occurrences of resident and invasive ant species

2020 ◽  
Author(s):  
Mark K. L. Wong ◽  
Toby P. N. Tsang ◽  
Owen T. Lewis ◽  
Benoit Guénard
Keyword(s):  
Solenopsis Invicta ◽  
Competitive Ability ◽  
Competitive Exclusion ◽  
Assembly Rules ◽  
Ecological Communities ◽  
Relative Importance ◽  
Invasive Ant ◽  
Phenotypic Differences ◽  
Trait Similarity ◽  
Dominant Process

AbstractInterspecific competition, a dominant process structuring ecological communities, acts on species’ phenotypic differences. Species with similar traits should compete intensely (trait-similarity), while those with traits that confer competitive ability should outcompete others (trait-hierarchy). Either or both of these mechanisms may drive competitive exclusion within a community, but their relative importance and interacting effects are rarely studied. We show empirically that spatial associations (pairwise co-occurrences) between an invasive ant Solenopsis invicta and 28 other ant species across a relatively homogenous landscape are explained largely by an interaction of trait-similarity and trait-hierarchy in one morphological trait. We find that increasing trait-hierarchy leads to more negative associations; however these effects are counteracted when species are sufficiently dissimilar (by 37-95%) in their trait ranges. We also show that a model of species co-occurrences integrating trait-similarity and trait-hierarchy consolidates predictions of different theoretical assembly rules. This highlights the explanatory potential of the trait-based co-occurrence approach.

scholarly journals Native and non-native sources of carbohydrate correlate with abundance of an invasive ant

NeoBiota ◽  
2020 ◽  
Vol 63 ◽  
pp. 155-175
Author(s):  
Lori Lach ◽  
Benjamin D. Hoffmann ◽  
Melinda L. Moir
Keyword(s):  
Native Species ◽  
New Caledonia ◽  
Trophic Position ◽  
Ecological Communities ◽  
Relative Importance ◽  
Invasive Ants ◽  
Invasive Ant ◽  
Carbohydrate Availability ◽  
Arnhem Land ◽  
Study Sites

Invasive species threaten many ecological communities and predicting which communities and sites are invasible remains a key goal of invasion ecology. Although invasive ants often reach high abundances in association with plant-based carbohydrate resources, the source and provenance of these resources are rarely investigated. We characterized carbohydrate resources across ten sites with a range of yellow crazy ant abundance in Arnhem Land, Australia and New Caledonia to determine whether yellow crazy ant (Anoplolepis gracilipes) abundance and trophic position correlate with carbohydrate availability, as well as the relative importance of native and non-native sources of carbohydrates to ant diet. In both locations, measures of yellow crazy ant abundance strongly positively correlated with carbohydrate availability, particularly honeydew production, the number of tended hemipterans, and the number of plants with tended hemipterans. In Arnhem Land, 99.6% of honeydew came from native species, whereas in New Caledonia, only 0.2% of honeydew was produced by a native hemipteran. More honeydew was available in Australia due to three common large-bodied species of Auchenorrhyncha honeydew producers (treehoppers and leafhoppers). Yellow crazy ant trophic position declined with increasing yellow crazy ant abundance indicating that in greater densities the ants are obtaining more of their diet from plant-derived resources, including honeydew and extrafloral nectar. The relationships between yellow crazy ant abundance and carbohydrate availability could not be explained by any of the key environmental variables we measured at our study sites. Our results demonstrate that the positive correlation between yellow crazy ant abundance and honeydew production is not contingent upon the provenance of the hemipterans. Native sources of carbohydrate may play an underappreciated role in greatly increasing community invasibility by ants.

scholarly journals Distinct colony boundaries and larval discrimination in polygyne red imported fire ants (Solenopsis invicta)

2021 ◽  
Author(s):  
MacKenzie Kjeldgaard ◽  
Pierre-André Eyer ◽  
Collin McMichael ◽  
Alison Bockoven ◽  
Joanie King ◽  
...  
Keyword(s):  
Solenopsis Invicta ◽  
Sucrose Solution ◽  
Ecological Impact ◽  
Egg Laying ◽  
Fire Ants ◽  
Fire Ant ◽  
Red Imported Fire Ant ◽  
Invasive Ant ◽  
Nestmate Discrimination ◽  
Social Forms

Evaluating the factors that promote invasive ant abundance is critical to assess their ecological impact and inform their management. Many invasive ant species show reduced nestmate recognition and an absence of boundaries between unrelated nests, which allow populations to achieve greater densities due to reduced intraspecific competition. We examined nestmate discrimination and colony boundaries in introduced populations of the red imported fire ant (Solenopsis invicta; hereafter, fire ant). Fire ants occur in two social forms: monogyne (colonies with a single egg-laying queen) and polygyne (colonies with multiple egg-laying queens). In contrast with monogyne nests, polygyne nests are thought to be interconnected due to the reduced antagonism between non-nestmate polygyne workers, perhaps because polygyne workers habituate the colony to an odor unique to Gp-9-carrying adults. However, colony boundaries and nestmate discrimination are poorly documented, particularly for worker-brood interactions. To delimit boundaries between field colonies, we correlated the exchange of a N-glycine tracer dissolved in a sucrose solution with social form. We also evaluated nestmate discrimination between polygyne workers and larvae in the laboratory. Counter to our expectations, polygyne colonies behaved identically to monogyne colonies, suggesting both social forms maintain strict colony boundaries. Polygyne workers also preferentially fed larval nestmates and may have selectively cannibalized non-nestmates. The levels of relatedness among workers in polygyne colonies was higher than those previously reported in North America (mean ±SE: 0.269 ± 0.037). Our study highlights the importance of combining genetic analyses with direct quantification of resource exchange to better understand the factors influencing ant invasions.

scholarly journals Dynamical persistence in resource-consumer models

2020 ◽  
Author(s):  
Itay Dalmedigos ◽  
Guy Bunin
Keyword(s):  
Fixed Points ◽  
Competitive Exclusion ◽  
Resource Competition ◽  
Exclusion Principle ◽  
Ecological Communities ◽  
Competitive Exclusion Principle ◽  
Stable Equilibria ◽  
Species Being ◽  
Abundance Fluctuations ◽  
High Diversity

We show how highly-diverse ecological communities may display persistent abundance fluctuations, when interacting through resource competition and subjected to migration from a species pool. This turns out to be closely related to the ratio of realized species diversity to the number of resources. This ratio is set by competition, through the balance between species being pushed out and invading. When this ratio is smaller than one, dynamics will reach stable equilibria. When this ratio is larger than one, fixed-points are either unstable or marginally stable, as expected by the competitive exclusion principle. If they are unstable, the system is repelled from fixed points, and abundances forever fluctuate. While marginally-stable fixed points are in principle allowed and predicted by some models, they become structurally unstable at high diversity. This means that even small changes to the model, such as non-linearities in how resources combine to generate species’ growth, will result in persistent abundance fluctuations.

scholarly journals An experimental test of the area–heterogeneity tradeoff

2020 ◽  
Vol 117 (9) ◽  
pp. 4815-4822 ◽  
Author(s):  
Eyal Ben-Hur ◽  
Ronen Kadmon
Keyword(s):  
Habitat Heterogeneity ◽  
Competitive Exclusion ◽  
Fundamental Property ◽  
Theoretical Models ◽  
Effective Area ◽  
Individual Species ◽  
Relative Importance ◽  
Average Area ◽  
Fixed Area ◽  
Positive Effect

A fundamental property of ecosystems is a tradeoff between the number and size of habitats: as the number of habitats within a fixed area increases, the average area per habitat must decrease. This tradeoff is termed the “area–heterogeneity tradeoff.” Theoretical models suggest that the reduction in habitat sizes under high levels of heterogeneity may cause a decline in species richness because it reduces the amount of effective area available for individual species under high levels of heterogeneity, thereby increasing the likelihood of stochastic extinctions. Here, we test this prediction using an experiment that allows us to separate the effect of the area–heterogeneity tradeoff from the total effect of habitat heterogeneity. Surprisingly, despite considerable extinctions, reduction in the amount of effective area available per species facilitated rather than reduced richness in the study communities. Our data suggest that the mechanism behind this positive effect was a decrease in the probability of deterministic competitive exclusion. We conclude that the area–heterogeneity tradeoff may have both negative and positive implications for biodiversity and that its net effect depends on the relative importance of stochastic vs. deterministic drivers of extinction in the relevant system. Our finding that the area–heterogeneity tradeoff may contribute to biodiversity adds a dimension to existing ecological theory and is highly relevant for understanding and predicting biodiversity responses to natural and anthropogenic variations in the environment.

scholarly journals Competitive dominance of Microcystis aeruginosa against Raphidiopsis raciborskii is strain- and temperature-dependent

2020 ◽  
pp. 36
Author(s):  
Lamei Lei ◽  
Jingjun Dai ◽  
Qiuqi Lin ◽  
Liang Peng
Keyword(s):  
Microcystis Aeruginosa ◽  
Competitive Ability ◽  
Competitive Exclusion ◽  
Strain Difference ◽  
Freshwater Ecosystems ◽  
Cylindrospermopsis Raciborskii ◽  
Temperature Dependent ◽  
Temperature Levels ◽  
Multiple Strains ◽  
Allelopathic Interactions

Microcystis aeruginosa and Raphidiopsis raciborskii (previously Cylindrospermopsis raciborskii) are both common bloom-forming cyanobacteria which can coexist but alternatively dominate in freshwater ecosystems. To predict their blooming dynamics, we need to understand the potential environmental factors determining their succession. In the present study, we examined the pairwise competition of the three M. aeruginosa strains (FACHB905, 469 and 915) with one R. raciborskii strain (N8) at three temperature levels (16 °C, 24 °C, and 32 °C). We found that the competitive ability of three Microcystis strains were highly variable. M. aeruginosa FACHB905 was the strongest competitor among them which can finally exclude R. raciborskii N8 regardless of initial biovolume ratios and temperature levels. The competitive exclusion of N8 by 915 also was observed at 24 °C, but they coexisted at 16 °C and 32 °C. We observed that M. aeruginosa FACHB469 and R. raciborskii N8 were able to coexist under all the temperature levels, and M. aeruginosa FACHB469 was the weakest competitor among the three M. aeruginosa strains. Rates of competitive exclusion (RCE) showed that temperature affects the competition between three M. aeruginosa strains and R. raciborskii N8. M. aeruginosa strains always grew quickly at 24 °C and significantly enlarged its dominance in the co-culture system, while R. raciborskii N8 was able to maintain its initial advantages at both 16 and 32 °C. The competitive advantage of M. aeruginosa FACHB905 may be explained by allelopathic interactions through its allelochemicals and other secondary metabolites other than microcystin. We concluded that both strain difference and temperature can affect the competition between M. aeruginosa and R. raciborskii. Our results highlighted the complexity of cyanobacterial dynamics in waterbodies where there exist multiple strains.

Ecology

2021 ◽  
pp. 417-452
Author(s):  
Paul Schmid-Hempel
Keyword(s):  
Climate Change ◽  
Body Size ◽  
Infectious Diseases ◽  
Food Webs ◽  
Competitive Ability ◽  
Apparent Competition ◽  
Ecological Communities ◽  
Disease Emergence ◽  
Animal Reservoir ◽  
Transient Structure

Host ecological characteristics, such as body size, longevity, or social living, affect parasitism. Host populations can be regulated in size by their parasites; they can even drive host populations to extinction, usually after hosts have been weakened by other factors. Parasites, therefore, threaten endangered populations and species. Parasites also affect host ecological communities and food webs via effects on competitive ability or with apparent competition. In diverse host communities, infectious diseases become ‘diluted’. Parasite ecological communities seem to have a variable and transient structure; no universal explanation for the observed patterns exists. Host migration can transfer parasites to new areas or leave parasites behind. Disease emergence from an animal reservoir (zoonoses) is especially important. Many human diseases have such an origin, and these have repeatedly caused major epidemics. Climate change will also affect parasitism; however, the direction of change is rather complex and depends on the particular systems.

Landscape Effects on Community Structure and Dynamics

2019 ◽  
pp. 434-511
Author(s):  
Kimberly A. With
Keyword(s):  
Species Diversity ◽  
Species Interactions ◽  
Geographical Area ◽  
Ecological Communities ◽  
Relative Importance ◽  
Habitat Amount ◽  
Structure And Dynamics ◽  
Landscape Effects ◽  
Diversity Gradients ◽  
Patch Scale

Ecological communities consist of species that interact to varying degrees within the same geographical area, and so by definition exist within a landscape context. This chapter begins by reviewing the measures and different scales at which species diversity can be assayed, including the use of spatial partitioning to evaluate multiscale patterns of diversity. The chapter then reviews correlates of species diversity, including explanations for latitudinal and elevational diversity gradients, before considering how habitat loss and fragmentation are expected to influence species diversity. The chapter tackles the debate surrounding the relative importance of habitat amount versus fragmentation in predicting species’ responses to landscape change, and highlights the importance of studying these effects at a landscape rather than patch scale. The chapter concludes with a discussion of landscape effects on different types of species interactions, and how interactions among species in different communities can give rise to metacommunity structure and dynamics.

scholarly journals Influence of the Host Contact Sequence on the Outcome of Competition amongAspergillus flavusIsolates during Host Tissue Invasion

2011 ◽  
Vol 77 (5) ◽  
pp. 1691-1697 ◽  
Author(s):  
H. L. Mehl ◽  
P. J. Cotty
Keyword(s):  
Competitive Ability ◽  
Competitive Exclusion ◽  
Aflatoxin Contamination ◽  
Host Tissue ◽  
Nucleotide Polymorphisms ◽  
Tissue Invasion ◽  
Genetic Types ◽  
Attachment Sites ◽  
Host Infection ◽  
Maize Kernels

ABSTRACTBiological control of aflatoxin contamination byAspergillus flavusis achieved through competitive exclusion of aflatoxin producers by atoxigenic strains. Factors dictating the extent to which competitive displacement occurs during host infection are unknown. The role of initial host contact in competition between pairs ofA. flavusisolates coinfecting maize kernels was examined. Isolate success during tissue invasion and reproduction was assessed by quantification of isolate-specific single nucleotide polymorphisms using pyrosequencing. Isolates were inoculated either simultaneously or 1 h apart. Increased success during competition was conferred to the first isolate to contact the host independent of that isolate's innate competitive ability. The first-isolate advantage decreased with the conidial concentration, suggesting capture of limited resources on kernel surfaces contributes to competitive exclusion. Attempts to modify access to putative attachment sites by either coating kernels with dead conidia or washing kernels with solvents did not influence the success of the first isolate, suggesting competition for limited attachment sites on kernel surfaces does not mediate first-isolate advantage. The current study is the first to demonstrate an immediate competitive advantage conferred toA. flavusisolates upon host contact and prior to either germ tube emergence or host colonization. This suggests the timing of host contact is as important to competition during disease cycles as innate competitive ability. Early dispersal to susceptible crop components may allow maintenance withinA. flavuspopulations of genetic types with low competitive ability during host tissue invasion.

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