Rethinking the evolution of specialization: A model for the evolution of phenotypic heterogeneity

Rubin, Ilan N.; Doebeli, Michael

doi:10.1016/j.jtbi.2017.09.020

“…The canonical equation of adaptive dynamics, as described above, can thus only describe the movement of populations in phenotype space, but not speciation or extinction events. Evolutionary branching is a well known phenomenon that occurs when there is an attracting equilibrium or nullcline [27–29] in trait space that is also a fitness minimum [19]. To model these we use a well described algorithm [18] where the adaptive dynamics are run for some period of time at which a random population is chosen and a small mutant is introduced nearby.…”

Section: Models and Methodsmentioning

confidence: 99%

Evolution to alternative levels of stable diversity leaves areas of niche space unexplored

Rubin

¹

,

Ispolatov

²

,

Doebeli

³

2021

Preprint

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One of the oldest and most persistent questions in ecology and evolution is whether natural communities tend to evolve toward saturation and maximal diversity. Robert MacArthur’s classical theory of niche packing and the theory of adaptive radiations both imply that populations will diversify and fully partition any available niche space. However, the saturation of natural populations is still very much an open area of debate and investigation. Additionally, recent evolutionary theory suggests the existence of alternative evolutionary stable states (ESSs), which implies that some stable communities may not be fully saturated. Using models with classical Lokta-Volterra ecological dynamics and three formulations of evolutionary dynamics (a model using adaptive dynamics, an individual-based model, and a partial differential equation model), we show that following an adaptive radiation, communities can often get stuck in low diversity states when limited by mutations of small phenotypic effect. These low diversity metastable states can also be maintained by limited resources and finite population sizes. When small mutations and finite populations are considered together, it is clear that despite the presence of higher-diversity stable states, natural populations are likely not fully saturating their environment and leaving potential niche space unfilled. Additionally, within-species variation can further reduce community diversity from levels predicted by models that assume species-level homogeneity.Author summaryUnderstanding if and when communities evolve to saturate their local environments is imperative to our understanding of natural populations. Using computer simulations of classical evolutionary models, we study whether adaptive radiations tend to lead toward saturated communities in which no new species can invade or remain trapped in alternative, lower diversity stable states. We show that with asymmetric competition and small effect mutations, evolutionary Red Queen dynamics can trap communities in low diversity metastable states. Moreover, limited resources not only reduces community population sizes, but also reduces community diversity, denying the formation of saturated communities and stabilizing low diversity, non-stationary evolutionary dynamics. Our results are directly relevant to the longstanding questions important to both ecological empiricists and theoreticians on the species packing and saturation of natural environments. Also, by showing the ease evolution can trap communities in low diversity metastable stats, we demonstrate the potential harm in relying solely on ESSs to answer questions of biodiversity.

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“…The canonical equation of adaptive dynamics, as introduced above (please see S1 Supporting Information for a full derivation of the adaptive dynamics), can thus only describe the movement of populations in phenotype space, but not speciation or extinction events. Evolutionary branching is a well known phenomenon that occurs when there is an attracting equilibrium or nullcline [ 27 – 29 ] in trait space that is also a fitness minimum [ 19 ]. To model these we use a well described algorithm [ 18 ] where the canonical equation of adaptive dynamics is numerically solved for some period of time at which a random population is chosen and a small mutant is introduced nearby.…”

Section: Models and Methodsmentioning

confidence: 99%

Evolution to alternative levels of stable diversity leaves areas of niche space unexplored

Rubin

¹

,

Ispolatov

²

,

Doebeli

³

2021

Self Cite

View full text Add to dashboard Cite

One of the oldest and most persistent questions in ecology and evolution is whether natural communities tend to evolve toward saturation and maximal diversity. Robert MacArthur’s classical theory of niche packing and the theory of adaptive radiations both imply that populations will diversify and fully partition any available niche space. However, the saturation of natural populations is still very much an open area of debate and investigation. Additionally, recent evolutionary theory suggests the existence of alternative evolutionary stable states (ESSs), which implies that some stable communities may not be fully saturated. Using models with classical Lotka-Volterra ecological dynamics and three formulations of evolutionary dynamics (a model using adaptive dynamics, an individual-based model, and a partial differential equation model), we show that following an adaptive radiation, communities can often get stuck in low diversity states when limited by mutations of small phenotypic effect. These low diversity metastable states can also be maintained by limited resources and finite population sizes. When small mutations and finite populations are considered together, it is clear that despite the presence of higher-diversity stable states, natural populations are likely not fully saturating their environment and leaving potential niche space unfilled. Additionally, within-species variation can further reduce community diversity from levels predicted by models that assume species-level homogeneity.

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“…Such "noisy gene expression" might itself be conceived as a selectable trait tunable by evolution, given that its excesses are regulated by dosage compensation in gene networks (220). There should be a certain "cost of high phenotypic variation" dampens dampening the strength of selection toward phenotypic heterogeneity and promoting directional selection of certain trajectories (221). However, a high rate of phenotypic heterogeneity is a safe "emergence strategy" for bacterial survival, but the advantageous phenotypic variants do not necessarily guide the directionality of the genetic adaptive trajectory (222).…”

Section: Frequencies Of Variation Phenotypic Variation: Bet-hedging Adaptive Strategiesmentioning

confidence: 99%

“…This reduced growth is mediated by genome inversions and reversible stochastic but self-organized inversion switches, which also affect antibiotic resistance, ensuring adequate time to develop compensatory mutations following the emergence of a resistant trait (228)(229)(230) and the stochastic emergence of persister cells with high resistance to the antibiotic killing effect (231,232). However, environmental variation in time or space is not a necessary condition for the evolution of phenotypic heterogeneity (221).…”

Section: Frequencies Of Variation Phenotypic Variation: Bet-hedging Adaptive Strategiesmentioning

confidence: 99%

Evolutionary Pathways and Trajectories in Antibiotic Resistance

Baquero

¹

,

Martínez

²

,

Lanza

³

et al. 2021

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Rethinking the evolution of specialization: A model for the evolution of phenotypic heterogeneity

Cited by 10 publications

References 57 publications

Evolution to alternative levels of stable diversity leaves areas of niche space unexplored

Evolution to alternative levels of stable diversity leaves areas of niche space unexplored

Evolution to alternative levels of stable diversity leaves areas of niche space unexplored

Evolutionary Pathways and Trajectories in Antibiotic Resistance

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