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Resource competition triggers the co-evolution of long tongues and deep corolla tubes.

Rodríguez-Gironés MA, Llandres AL - PLoS ONE (2008)

Bottom Line: It is normally thought that deep corolla tubes evolve when a plant's successful reproduction is contingent on having a corolla tube longer than the tongue of the flower's pollinators, and that pollinators evolve ever-longer tongues because individuals with longer tongues can obtain more nectar from flowers.Once the two pollinator species differ in tongue length, divergence in corolla-tube depth between the two plant species ensues.Co-evolution between tongue length and corolla-tube depth is a robust outcome of the model, obtained for a wide range of parameter values, but it requires that tongue elongation is substantially easier for one pollinator species than for the other, that pollinators follow a near-optimal foraging strategy, that pollinators experience competition for resources and that plants experience pollination limitation.

View Article: PubMed Central - PubMed

Affiliation: Department of Functional and Evolutionary Ecology, Estación Experimental de Zonas Aridas (CSIC), Almería, Spain. rgirones@eeza.csic.es

ABSTRACT

Background: It is normally thought that deep corolla tubes evolve when a plant's successful reproduction is contingent on having a corolla tube longer than the tongue of the flower's pollinators, and that pollinators evolve ever-longer tongues because individuals with longer tongues can obtain more nectar from flowers. A recent model shows that, in the presence of pollinators with long and short tongues that experience resource competition, coexisting plant species can diverge in corolla-tube depth, because this increases the proportion of pollen grains that lands on co-specific flowers.

Methodology/principal findings: We have extended the model to study whether resource competition can trigger the co-evolution of tongue length and corolla-tube depth. Starting with two plant and two pollinator species, all of them having the same distribution of tongue length or corolla-tube depth, we show that variability in corolla-tube depth leads to divergence in tongue length, provided that increasing tongue length is not equally costly for both species. Once the two pollinator species differ in tongue length, divergence in corolla-tube depth between the two plant species ensues.

Conclusions/significance: Co-evolution between tongue length and corolla-tube depth is a robust outcome of the model, obtained for a wide range of parameter values, but it requires that tongue elongation is substantially easier for one pollinator species than for the other, that pollinators follow a near-optimal foraging strategy, that pollinators experience competition for resources and that plants experience pollination limitation.

Show MeSH
Pollination effectiveness.Asymmetries in pollination effectiveness (defined as per visit probability of pollen transfer) hardly affect the divergence of proboscis length (triangles) and corolla-tube depth (circles) after 20,000 generations.
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pone-0002992-g005: Pollination effectiveness.Asymmetries in pollination effectiveness (defined as per visit probability of pollen transfer) hardly affect the divergence of proboscis length (triangles) and corolla-tube depth (circles) after 20,000 generations.

Mentions: So far we have assumed that the probability of pollen transfer from the body of a moth of species J to a flower of species K, pJK, is pXA = 0.3, pXB = 0.2, pYA = 0.2 and pYB = 0.3. To study whether co-evolution requires the pairing, in terms of pollination effectiveness, of moth and plant species, we set pXA = pYB = 0.25+δ and pXB = pYA = 0.25–δ and run the simulations for different values of δ. Divergence in proboscis length and corolla-tube depth was observed for all values of δ (including δ = 0). The value of δ does not affect the differences in corolla-tube depth and proboscis length following 20000 generations (Fig. 5), but the rate of evolution does depend on δ: the lower the value of δ, the longer it takes for divergence in corolla-tube depth to get started (Fig. 6).


Resource competition triggers the co-evolution of long tongues and deep corolla tubes.

Rodríguez-Gironés MA, Llandres AL - PLoS ONE (2008)

Pollination effectiveness.Asymmetries in pollination effectiveness (defined as per visit probability of pollen transfer) hardly affect the divergence of proboscis length (triangles) and corolla-tube depth (circles) after 20,000 generations.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2500161&req=5

pone-0002992-g005: Pollination effectiveness.Asymmetries in pollination effectiveness (defined as per visit probability of pollen transfer) hardly affect the divergence of proboscis length (triangles) and corolla-tube depth (circles) after 20,000 generations.
Mentions: So far we have assumed that the probability of pollen transfer from the body of a moth of species J to a flower of species K, pJK, is pXA = 0.3, pXB = 0.2, pYA = 0.2 and pYB = 0.3. To study whether co-evolution requires the pairing, in terms of pollination effectiveness, of moth and plant species, we set pXA = pYB = 0.25+δ and pXB = pYA = 0.25–δ and run the simulations for different values of δ. Divergence in proboscis length and corolla-tube depth was observed for all values of δ (including δ = 0). The value of δ does not affect the differences in corolla-tube depth and proboscis length following 20000 generations (Fig. 5), but the rate of evolution does depend on δ: the lower the value of δ, the longer it takes for divergence in corolla-tube depth to get started (Fig. 6).

Bottom Line: It is normally thought that deep corolla tubes evolve when a plant's successful reproduction is contingent on having a corolla tube longer than the tongue of the flower's pollinators, and that pollinators evolve ever-longer tongues because individuals with longer tongues can obtain more nectar from flowers.Once the two pollinator species differ in tongue length, divergence in corolla-tube depth between the two plant species ensues.Co-evolution between tongue length and corolla-tube depth is a robust outcome of the model, obtained for a wide range of parameter values, but it requires that tongue elongation is substantially easier for one pollinator species than for the other, that pollinators follow a near-optimal foraging strategy, that pollinators experience competition for resources and that plants experience pollination limitation.

View Article: PubMed Central - PubMed

Affiliation: Department of Functional and Evolutionary Ecology, Estación Experimental de Zonas Aridas (CSIC), Almería, Spain. rgirones@eeza.csic.es

ABSTRACT

Background: It is normally thought that deep corolla tubes evolve when a plant's successful reproduction is contingent on having a corolla tube longer than the tongue of the flower's pollinators, and that pollinators evolve ever-longer tongues because individuals with longer tongues can obtain more nectar from flowers. A recent model shows that, in the presence of pollinators with long and short tongues that experience resource competition, coexisting plant species can diverge in corolla-tube depth, because this increases the proportion of pollen grains that lands on co-specific flowers.

Methodology/principal findings: We have extended the model to study whether resource competition can trigger the co-evolution of tongue length and corolla-tube depth. Starting with two plant and two pollinator species, all of them having the same distribution of tongue length or corolla-tube depth, we show that variability in corolla-tube depth leads to divergence in tongue length, provided that increasing tongue length is not equally costly for both species. Once the two pollinator species differ in tongue length, divergence in corolla-tube depth between the two plant species ensues.

Conclusions/significance: Co-evolution between tongue length and corolla-tube depth is a robust outcome of the model, obtained for a wide range of parameter values, but it requires that tongue elongation is substantially easier for one pollinator species than for the other, that pollinators follow a near-optimal foraging strategy, that pollinators experience competition for resources and that plants experience pollination limitation.

Show MeSH