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opencc-by-4.0Nov 2021View details →

Effects of phenotypic plasticity on species coexistence

Data generated during a study on the effects of phenotypic plasticity on species coexistence. Hess_etal_Data_Competition_01.csv contains data generated during competition trials between two species (Lemna minor and Spirodela polyrhiza). Prior to the competition trials, replicate populations of these species were subject to one of two different levels of an experimental treatment - either low-frequency plasticity-induction or a high-frequency plasticity-induction. Refer to manuscript for full details. Hess_etal_Data_Traits_01.csv contains data on morphological traits of Lemna minor and Spirodela polyrhiza subject to either low- or high-frequency plasticity-induction. Refer to manuscript for full details.

opencc-by-4.0May 2012View details →

Fig. 1 in Geographic Variation In Habitat Requirements Of Two Coexisting Newt Species In Europe

Fig. 1. (A) Distribution of the northern crested newt (Triturus cristatus) and (B) the smooth newt (T. vulgaris) in Europe (ARNOLD 2002), and their habitat studies performed by country. The symbols indicate (i) landscape types where study was conducted (1 = woodland mosaic with bogs; 2 = woodland mosaic with semi-natural areas; 3 = woodland mosaic with agricultural areas; 4 = inland dunes; 5 = bogs; 6 = agricultural areas; 7 = urban areas) and (ii) the inclusion of terrestrial and aquatic habitat features (filled symbols – both examined; half filled – aquatic habitat only; hollow symbol – terrestrial habitat only). Vegetation zones (according to AASMÄE 2005): A, tundra; B, alpine tundra; C, taiga; D, tem-

opencc-zeroJun 2022View details →

Broad-scale patterns of geographic avoidance between species emerge in the absence of fine-scale mechanisms of coexistence

Aim: The need to forecast range shifts under future climate change has motivated an increasing interest in better understanding the role of biotic interactions in driving diversity patterns. The contribution of biotic interactions to shaping broad-scale species distributions is however, still debated, partly due to the difficulty of detecting their effects. We aim to test whether spatial exclusion between potentially competing species can be detected at the species range scale, and whether this pattern relates to fine-scale mechanisms of coexistence. Location: Western Palearctic Time period: Anthropocene Taxa: bats (Chiroptera) Methods: We develop and evaluate a measure of geographic avoidance that uses outputs of species distribution models to quantify geographic exclusion patterns expected if interspecific competition affects broad-scale distributions. We apply the measure to 10 Palearctic bat species belonging to four morphologically similar cryptic groups in which competition is likely to occur. We compare outputs to null models based on pairs of virtual species and to expectations based on ecological similarity and fine-scale coexistence mechanisms. We project changes in range suitability under climate change taking into account effects of geographic avoidance. Results: Values of geographic avoidance were above null expectations for two cryptic species pairs, suggesting that interspecific competition could have contributed to shaping their broad-scale distributions. These two pairs showed highest levels of ecological similarity and no trophic or habitat partitioning. Considering the role of competition modified predictions of future range suitability. Conclusions: Our results support the role of interspecific competition in limiting the geographic ranges of morphologically similar species in the absence of fine-scale mechanisms of coexistence. This study highlights the importance of incorporating biotic interactions into predictive models of range shifts under climate change, and the need for further integration of community ecology with species distribution models to understand the role of competition in ecology and biogeography.

opencc-by-4.0Jun 2013View details →

Supplementary material 1 from: Hejda M (2013) Do species differ in their ability to coexist with the dominant alien Lupinus polyphyllus? A comparison between two distinct invaded ranges and a native range. NeoBiota 17: 39-55. https://doi.org/10.3897/neobiota.17.4317

Entry data for the univariate models with species richness as a response variable. (doi: 10.3897/neobiota.17.4317.app1) File format: Micrisoft Excell document (xls). :

opencc-zeroJun 2024View details →

Mechanisms of coexistence: Exploring species sorting and character displacement in woody plants to alleviate belowground competition

Rarely do we observe competitive exclusion within plant communities, even though plants compete for a limited pool of resources. Thus, our understanding of the mechanisms sustaining plant biodiversity might be limited. In this study, we explore two common ecological strategies, species sorting and character displacement, that promote coexistence by reducing competition. We assess the degree to which woody plants may implement these two strategies to lower belowground competition for nutrients which occurs via nutritional (mostly mycorrhizal) mutualisms. First, we compile data on plant traits and the mycorrhizal association state of woody angiosperms using a global inventory of indigenous flora. Our analysis reveals that species in locations with high mycorrhizal diversity exhibit distinct mean values in leaf area and wood density based on their mycorrhizal type, indicating species sorting. Second, we reanalyze a large dataset on leaf area to demonstrate that in areas with high mycorrhizal diversity, trees maintain divergent leaf area values, showcasing character displacement. Character displacement among plants is considered rare, making our observation significant. In summary, our study uncovers a rare occurrence of character displacement and identifies a common mechanism employed by plants to alleviate competition, shedding light on the complexities of plant coexistence in diverse ecosystems.

Fig. 6 in Tolerance to Anhydrobiotic Conditions Among Two Coexisting Tardigrade Species Differing in Life Strategies.

Fig. 6. Relation of the measured activity indices to time spent in the tun stage in Milnesium inceptum: (A) time to first movement of any first individual (FM); (B) time to first movement of all individuals (FAA); (C) time to full activity of any first individual (FA); (D) time to full activity of all individuals (FAA). Curves were ± SE fitted with Local Polynomial Regression Fitting (LOESS).

Fig. 5 in Tolerance to Anhydrobiotic Conditions Among Two Coexisting Tardigrade Species Differing in Life Strategies.

Fig. 5. Relationship between the measured activity indices and time spent during the tun stage for Ramazzottius subanomalus: (A) time to first movement of any first individuals (FM); (B) time to first movement of all individuals (FAA); (C) time to full activity of any first individual (FA); (D) time to full activity of all individuals (FAA). Curves ± SE were fitted with Local Polynomial Regression Fitting (LOESS).

Fig. 3. A in Tolerance to Anhydrobiotic Conditions Among Two Coexisting Tardigrade Species Differing in Life Strategies.

Fig. 3. A time from the start of rehydration to the first movement (FM) of any first individual and all individuals (FMA) in the experimental groups representing increasing duration of the tun stage for Milnesium inceptum (A, C) and Ramazzottius subanomalus (B, D). The number of replicate samples for each group n = 10.

Fig. 4. A in Tolerance to Anhydrobiotic Conditions Among Two Coexisting Tardigrade Species Differing in Life Strategies.

Fig. 4. A time from the start of rehydration to the full activity (FA) of any first individual and all individuals (FAA) in the experimental groups representing increasing duration of the tun stage for Milnesium inceptum (A, C) and Ramazzottius subanomalus (B, D). The number of replicate samples for each group n = 10.

Fig. 2 in Tolerance to Anhydrobiotic Conditions Among Two Coexisting Tardigrade Species Differing in Life Strategies.

Fig. 2. Differences in the number of non-moving (NM) and not fully active (NFA) individuals between experimental groups representing increasing duration of the tun stage for Milnesium inceptum (A, C) and Ramazzottius subanomalus (B, D). The number of replicate samples for each group n = 10.

opencc-zeroAug 2021View details →

The evolution of size-dependent competitive interactions promotes species coexistence

1. Theory indicates that competing species coexist in a community when intraspecific competition is stronger than interspecific competition. When body size determines the outcome of competitive interactions between individuals, coexistence depends also on how resource use and the ability to compete for these resources change with body size. Testing coexistence theory in size-structured communities, therefore, requires disentangling the effects of size-dependent competitive abilities and niche shifts. 2. Here, we tested the hypothesis that the evolution of species and size-dependent competitive asymmetries increased the likelihood of coexistence between interacting species. 3. We experimentally estimated the effects of size-dependent competitive interactions on somatic growth rates of two interacting fish species, Trinidadian guppies (Poecilia reticulata) and killifish (Rivulus hartii). We controlled for the effects of size-dependent changes in the niche at two competitive settings representing the early (allopatric) and late (sympatric) evolutionary stages of a killifish-guppy community. We fitted the growth data to a model that incorporates species and size-dependent competitive asymmetries to test whether changes in the competitive interactions across sizes increased the likelihood of species coexistence from allopatry to sympatry. 4. We found that guppies are competitively superior to killifish but were less so in sympatric populations. The decrease in the effects of interspecific competition on the fitness of killifish and increase in the interspecific effect on guppies' fitness increased the likelihood that sympatric guppies and killifish will coexist. However, while the competitive asymmetries between the species changed consistently between allopatry and sympatry between drainages, the magnitude of the size-dependent competitive asymmetries varied between drainages. 5. These results demonstrate the importance of integrating evolution and trait-based interactions into the research on how species coexist.

Figure 4 in Coexistence of species of two amphipod genera: Niphargus timavi (Niphargidae) and Gammarus fossarum (Gammaridae)

Figure 4. Percentage of ovigerous females for Gammarus fossarum (black bars) and Niphargus timavi (white bars).

Figure 1 in Coexistence of species of two amphipod genera: Niphargus timavi (Niphargidae) and Gammarus fossarum (Gammaridae)

Figure 1. (A) The study area with numbers indicating the eight sampling sites; (B) average water level (m) of river Reka at Ilirska Bistrica, measured between 1958 and 2003.

Figure 3 in Coexistence of species of two amphipod genera: Niphargus timavi (Niphargidae) and Gammarus fossarum (Gammaridae)

Figure 3. Life cycles of Gammarus fossarum (A, C) and Niphargus timavi (B, D). (A, B) Relative proportions of males (mid-grey), non-ovigerous females (dark grey), ovigerous females (white), and juveniles (light grey); (C, D) total number of specimens (e) and total number of eggs (m); note that several samples have been pooled for Niphargus.

Figure 2 in Coexistence of species of two amphipod genera: Niphargus timavi (Niphargidae) and Gammarus fossarum (Gammaridae)

Figure 2. Relative abundance of Niphargus timavi at sampling sites 1–8 as box-whiskers plots with the median, lower and upper quartiles, and outliers (×) indicated.

opencc-zeroDec 2020View details →

Hybridization and the coexistence of species: HZAM-Sym code and data files

It is thought that two species can coexist if they use different resources present in the environment, yet this assumes that species are completely reproductively isolated. We model coexistence outcomes for two sympatric species that are ecologically differentiated but have incomplete reproductive isolation. The consequences of interbreeding depend crucially on hybrid fitness. When hybrid fitness is high, just a small rate of hybridization can lead to collapse of two species into one. Low hybrid fitness can cause population declines, making extinction of one or both species likely. High intrinsic growth rates result in higher reproductive rates when populations are below carrying capacity, reducing the probability of extinction and increasing the probability of stable coexistence at moderate levels of assortative mating and hybrid fitness. Very strong but incomplete assortative mating can induce low hybrid fitness via a mating disadvantage to rare genotypes, and this can stabilize coexistence of two species at high but incomplete levels of assortative mating. Given these results and evidence that it may take many millions of years of divergence before related species become sympatric, we postulate that coexistence of closely-related species is more often limited by insufficient assortative mating than by insufficient ecological differentiation.

opencc-zeroDec 2022View details →

Predator discrimination of prey promotes the predator-mediated coexistence of prey species

The predator discrimination of prey can affect predation intensity and the prey density-dependence of predators, which has the potential to alter the coexistence of prey species. We used a predator–prey population dynamics model accounting for the predator's adaptive diet choice and predator discrimination of prey to investigate how the latter influences prey coexistence. The model revealed that: (1) prey species that are perceived as belonging to the same species by a predator are attacked in the same manner, and it is more difficult for them to coexist than those that are recognised as different prey species; and (2) prey species that are not discriminated by a predator—and therefore cannot coexist—may coexist in the presence of an alternative predator that does discriminate between them. These results suggest that prey diversity, which favours the predator discrimination of prey, and the different capabilities of predators to identify prey species both enhance prey coexistence.

opencc-zeroMar 2023View details →

Data for: Does the evolution of ontogenetic niche shifts favor species coexistence? An empirical test in Trinidadian streams

A major question in ecology is how often competing species evolve to reduce competitive interactions and facilitate coexistence. One untested route for a reduction in competitive interactions is through ontogenetic changes in the trophic niche of one or more of the interacting species. In such cases, theory predicts that two species can coexist if the weaker competitor changes its resource niche to a greater degree with increased body size than the superior competitor. We tested this prediction using stable isotopes that yield information about the trophic position (δ15N) and carbon source (δ13C) of two coexisting fish species: Trinidadian guppies (Poecilia reticulata) and killifish (Rivulus hartii). We examined fish from locations representing three natural community types: 1) where killifish and guppies live with predators; 2) where killifish and guppies live without predators; and 3) where killifish are the only fish species. We also examined killifish from communities in which we had introduced guppies, providing a temporal sequence of the community changes following the transition from a killifish only to a killifish-guppy community. We found that killifish, which are the weaker competitor, had a much larger ontogenetic niche shift in trophic position than guppies in the community where competition is most intense (killifish-guppy only). This result is consistent with theory for size-structured populations, which predicts that these results should lead to stable coexistence of the two species. Comparisons with other communities containing guppies, killifish and predators and ones where killifish live by themselves revealed that these results are caused primarily by a loss of ontogenetic niche changes in guppies, even though they are the stronger competitor. Comparisons of these natural communities with communities in which guppies were translocated into sites containing only killifish showed that the experimental communities were intermediate between the natural killifish-guppy community and the killifish-guppy-predator community, suggesting contemporary evolution in these ontogenetic trophic differences. These results provide comparative evidence for ontogenetic niche shifts in contributing to species coexistence and comparative and experimental evidence for evolutionary or plastic changes in ontogenetic niche shifts following the formation of new communities.