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Predicting the outcome of competition when fitness inequality is variable.

Pedruski MT, Fussmann GF, Gonzalez A - R Soc Open Sci (2015)

Bottom Line: We used numerical simulations to investigate the outcome of two-species resource competition along gradients of fitness inequality (inequality in R*) and initial population size in the presence of demographic stochasticity.We found that the deterministic prediction of more fit competitors excluding less fit competitors was often unobserved when fitness inequalities were low or stochasticity was strong, and unexpected outcomes such as dominance by the less fit competitor, long-term co-persistence of both competitors or the extinction of both competitors could be common.By examining the interaction between fitness inequality and stochasticity our results mark the range of parameter space in which the predictions of niche theory break down most severely, and suggest that questions about whether competitive dynamics are driven by neutral or niche processes may be locally contingent.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology , McGill University, 1205 Docteur Penfield , Montréal, Quebec, Canada H3A 1B1.

ABSTRACT
Traditional niche theory predicts that when species compete for one limiting resource in simple ecological settings the more fit competitor should exclude the less fit competitor. Since the advent of neutral theory ecologists have increasingly become interested both in how the magnitude of fitness inequality between competitors and stochasticity may affect this prediction. We used numerical simulations to investigate the outcome of two-species resource competition along gradients of fitness inequality (inequality in R*) and initial population size in the presence of demographic stochasticity. We found that the deterministic prediction of more fit competitors excluding less fit competitors was often unobserved when fitness inequalities were low or stochasticity was strong, and unexpected outcomes such as dominance by the less fit competitor, long-term co-persistence of both competitors or the extinction of both competitors could be common. By examining the interaction between fitness inequality and stochasticity our results mark the range of parameter space in which the predictions of niche theory break down most severely, and suggest that questions about whether competitive dynamics are driven by neutral or niche processes may be locally contingent.

No MeSH data available.


The percentage of simulations at fitness equality (parameter space value 18) that yield the dominance of one competitor (either species) as a function of initial population size and growth rate.
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RSOS150274F2: The percentage of simulations at fitness equality (parameter space value 18) that yield the dominance of one competitor (either species) as a function of initial population size and growth rate.

Mentions: Initial population size affected the probability of observing all the potential competitive outcomes. In general, dominance by the more fit competitor and co-persistence increased as the initial population size increased (figure 1, rows 1,3), while cases of dual extinction decreased as initial population size increased (figure 1, row 4). The frequency of dominance of the less fit competitor (figure 1, row 2), and the dominance of either competitor at fitness equality (figure 2) were also affected by initial population size, but the relationship between population size and frequency was dependent on growth rates: in the low growth model both had unimodal relationships to initial population size with maxima at intermediate population sizes, whereas at high growth rates the frequency of both declined as initial population size increased.Figure 2.


Predicting the outcome of competition when fitness inequality is variable.

Pedruski MT, Fussmann GF, Gonzalez A - R Soc Open Sci (2015)

The percentage of simulations at fitness equality (parameter space value 18) that yield the dominance of one competitor (either species) as a function of initial population size and growth rate.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4555862&req=5

RSOS150274F2: The percentage of simulations at fitness equality (parameter space value 18) that yield the dominance of one competitor (either species) as a function of initial population size and growth rate.
Mentions: Initial population size affected the probability of observing all the potential competitive outcomes. In general, dominance by the more fit competitor and co-persistence increased as the initial population size increased (figure 1, rows 1,3), while cases of dual extinction decreased as initial population size increased (figure 1, row 4). The frequency of dominance of the less fit competitor (figure 1, row 2), and the dominance of either competitor at fitness equality (figure 2) were also affected by initial population size, but the relationship between population size and frequency was dependent on growth rates: in the low growth model both had unimodal relationships to initial population size with maxima at intermediate population sizes, whereas at high growth rates the frequency of both declined as initial population size increased.Figure 2.

Bottom Line: We used numerical simulations to investigate the outcome of two-species resource competition along gradients of fitness inequality (inequality in R*) and initial population size in the presence of demographic stochasticity.We found that the deterministic prediction of more fit competitors excluding less fit competitors was often unobserved when fitness inequalities were low or stochasticity was strong, and unexpected outcomes such as dominance by the less fit competitor, long-term co-persistence of both competitors or the extinction of both competitors could be common.By examining the interaction between fitness inequality and stochasticity our results mark the range of parameter space in which the predictions of niche theory break down most severely, and suggest that questions about whether competitive dynamics are driven by neutral or niche processes may be locally contingent.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology , McGill University, 1205 Docteur Penfield , Montréal, Quebec, Canada H3A 1B1.

ABSTRACT
Traditional niche theory predicts that when species compete for one limiting resource in simple ecological settings the more fit competitor should exclude the less fit competitor. Since the advent of neutral theory ecologists have increasingly become interested both in how the magnitude of fitness inequality between competitors and stochasticity may affect this prediction. We used numerical simulations to investigate the outcome of two-species resource competition along gradients of fitness inequality (inequality in R*) and initial population size in the presence of demographic stochasticity. We found that the deterministic prediction of more fit competitors excluding less fit competitors was often unobserved when fitness inequalities were low or stochasticity was strong, and unexpected outcomes such as dominance by the less fit competitor, long-term co-persistence of both competitors or the extinction of both competitors could be common. By examining the interaction between fitness inequality and stochasticity our results mark the range of parameter space in which the predictions of niche theory break down most severely, and suggest that questions about whether competitive dynamics are driven by neutral or niche processes may be locally contingent.

No MeSH data available.