Nathaniel Holland - Profile on Academia.edu (original) (raw)

Papers by Nathaniel Holland

Ann Entomol Soc Amer, 2003

Despite great variation in instar number among Insecta, no Lepidopteran has been observed to have... more Despite great variation in instar number among Insecta, no Lepidopteran has been observed to have less than four larval instars. I report in this work on the life cycle and growth of the senita moth, Upiga virescens Hulst, which forms an obligate pollinating predispersal seed-eating mutualism with senita cacti (Lophocereus schottii Engelmann) in the Sonoran Desert of North America. From 1996 to 1999, I studied larval growth and life cycle associations of U. virescens with L. schottii in the Þeld by labeling cohorts of eggs laid in ßowers and following them through pupation. All life stages of U. virescens were associated with ßowers, fruit, or cactus stems of L. schottii. Among the Þve cohorts studied, larval growth consistently conformed to DyarÕs rule. Only three larval instars were identiÞed among the Ͼ500 larvae for which head capsule widths were measured. I discuss and dismiss the feasibility of a fourth undetected instar. I then discuss selection pressures that may have contributed to the evolutionary loss of an instar, including a time and/or size constraint on larval growth, as well as the nutritional quantity and quality of larval food.

Annals of the Entomological Society of America, 2003

Despite great variation in instar number among Insecta, no Lepidopteran has been observed to have... more Despite great variation in instar number among Insecta, no Lepidopteran has been observed to have less than four larval instars. I report in this work on the life cycle and growth of the senita moth, Upiga virescens Hulst, which forms an obligate pollinating predispersal seed-eating mutualism with senita cacti (Lophocereus schottii Engelmann) in the Sonoran Desert of North America. From 1996 to 1999, I studied larval growth and life cycle associations of U. virescens with L. schottii in the Þeld by labeling cohorts of eggs laid in ßowers and following them through pupation. All life stages of U. virescens were associated with ßowers, fruit, or cactus stems of L. schottii. Among the Þve cohorts studied, larval growth consistently conformed to DyarÕs rule. Only three larval instars were identiÞed among the Ͼ500 larvae for which head capsule widths were measured. I discuss and dismiss the feasibility of a fourth undetected instar. I then discuss selection pressures that may have contributed to the evolutionary loss of an instar, including a time and/or size constraint on larval growth, as well as the nutritional quantity and quality of larval food.

Ecology Letters, Oct 1, 2009

Interactions between two populations are often defined by their interaction outcomes; that is, th... more Interactions between two populations are often defined by their interaction outcomes; that is, the positive, neutral, or negative effects of species on one another. Yet, signs of outcomes are not absolute, but vary with the biotic and abiotic contexts of interactions. Here, we develop a general theory for transitions between outcomes based on consumer-resource (C-R) interactions in which one or both species exploit the other as a resource. Simple models of C-R interactions revealed multiple equilibria, including one for species coexistence and others for extinction of one or both species, indicating that speciesÕ densities alone could determine the fate of interactions. All possible outcomes [(+ +), (+ )), () )), (+ 0), () 0), (0 0)] of species coexistence emerged merely through changes in parameter values of C-R interactions, indicating that variation in C-R interactions resulting from biotic and abiotic conditions could determine shifts in outcomes. These results suggest that C-R interactions can provide a broad mechanism for understanding context-and density-dependent transitions between interaction outcomes.

The foley catheter in the management of epistaxis

International Journal of Clinical Practice, 2001

The Foley urinary catheter has been used in the management of epistaxis for many years, yet it ha... more The Foley urinary catheter has been used in the management of epistaxis for many years, yet it has never been designed or licensed for this purpose. We performed a telephone questionnaire of senior house officers in 90 ENT departments in England and Wales. The aim was to determine how many departments used the Foley catheter for epistaxis management, whether licensed nasal balloon devices were available and if there had been any complications associated with their use. Eighty-three (92%) ENT departments in the study used the Foley catheter for epistaxis management and 44 (49%) departments had licensed balloon devices available. Only 22% of ENT senior house officers questioned were aware that the Foley catheter was not licensed for use in the nose. Most complications associated with the use of nasal balloon devices appear to be due to Foley catheters.

Discrimination among floral resources by an obligately pollinating seed-eating moth: host-marking signals and pollination and florivory cues

Evolutionary Ecology Research, 2010

Discrimination among floral resources by an obligately ... Katherine C. Horn and J. Nathaniel Hol... more Discrimination among floral resources by an obligately ... Katherine C. Horn and J. Nathaniel Holland ... Department of Ecology and Evolutionary Biology, Rice University, Houston, Texas, USA ... Background: For oviposition, some insects exploit small discrete food ...

Oecologia, Feb 22, 2001

Mutualistic interactions almost always produce both costs and benefits for each of the interactin... more Mutualistic interactions almost always produce both costs and benefits for each of the interacting species. It is the difference between gross benefits and costs that determines the net benefit and the per-capita effect on each of the interacting populations. For example, the net benefit of obligate pollinators, such as yucca and senita moths, to plants is determined by the difference between the number of ovules fertilized from moth pollination and the number of ovules eaten by the pollinator's larvae. It is clear that if pollinator populations are large, then, because many eggs are laid, costs to plants are large, whereas, if pollinator populations are small, gross benefits are low due to lack of pollination. Even though the size and dynamics of the pollinator population are likely to be crucial, their importance has been neglected in the investigation of mechanisms, such as selective fruit abortion, that can limit costs and increase net benefits. Here, we suggest that both the population size and dynamics of pollinators are important in determining the net benefits to plants, and that fruit abortion can significantly affect these. We develop a model of mutualism between populations of plants and their pollinating seed-predators to explore the ecological consequences of fruit abortion on pollinator population dynamics and the net effect on plants. We demonstrate that the benefit to a plant population is unimodal as a function of pollinator abundance, relative to the abundance of flowers. Both selective abortion of fruit with eggs and random abortion of fruit, without reference to whether they have eggs or not, can limit pollinator population size. This can increase the net benefits to the plant population by limiting the number of eggs laid, if the pollination rate remains high. However, fruit abortion can possibly destabilize the pollinator population, with negative consequences for the plant population.

Ecological conditions for fruit abortion to regulate pollinator/seed-predators and increase plant re

Journal of Ecology, 2009

Nearly all mutualisms entail the production of resources by one species that attract and reward t... more Nearly all mutualisms entail the production of resources by one species that attract and reward the species with which it interacts. As such resource production could otherwise be allocated to growth or reproduction, mutualists are predicted to minimize these investment costs. Here, we employ optimal defence theory for plant secondary compounds to evaluate plant production of extrafloral nectar (EFN) resources to attract and reward ants for resistance against herbivores. 2. Through ant exclusion and artificial herbivory experiments, we examined investment in EFN by both buds and fruits of Pachycereus schottii (senita cacti) in the Sonoran Desert of North America. We tested predictions of optimal defence theory that plants invest more in high value parts (fruits) through constitutive EFN, less in low value parts (buds) through induced EFN, and that for a given plant part (buds or fruits), constitutive and induced EFN are negatively correlated. 3. Constitutive levels of EFN were greater in fruits than in buds. Only buds showed induced EFN production following artificial herbivory. Constitutive EFN scaled positively with fruit size but not bud size. Induced EFN was negatively correlated with constitutive EFN for fruits (but not buds), suggesting a potential trade-off in these two herbivore resistance traits. 4. These results indicate that P. schottii minimizes its costs by investing in induced EFN for buds and constitutive EFN for fruits. Moreover, by shifting from induced to constitutive EFN with the morphogenesis of buds to fruits, our results show that investment in EFN can change as a particular plant tissue increases from a lower to a higher value. 5. Synthesis . Indirect defence through EFN production is in accord with that of direct defence through plant secondary compounds, thereby supporting optimal defence theory as a general framework with which to evaluate the costs of producing resources (i.e. the defence) by plants, lycaenids and homopterans to attract and reward ants for their resistance against natural enemies in protection mutualisms.

Post-hibernation movement and foraging habitat of a male Indiana bat, Myotis sodalis (Chiroptera: Vespertilionidae), in western Virginia

á Post-hibernation movement and foraging habitat of a male Indiana bat, Myotis sodalis (Chiropter... more á Post-hibernation movement and foraging habitat of a male Indiana bat, Myotis sodalis (Chiroptera:áVespertilionidae), in western Virginia. DSpace/Manakin Repository. ...

Ecology, 1999

Pollinating seed-consuming interactions are rare, but include fig-fig wasp and yucca-yucca moth i... more Pollinating seed-consuming interactions are rare, but include fig-fig wasp and yucca-yucca moth interactions, both of which are thought to be coevolved.

Emergence of functional responses from interactions of individuals

Interspecific interactions and range margins: contrasts among interaction types

Background/Question/Methods Ecologists seek to anticipate how species interactions shift a specie... more Background/Question/Methods Ecologists seek to anticipate how species interactions shift a species’ range margins (the limit of its geographic distribution). There is a great diversity of types of species interactions and at present, we lack a clear understanding of which species’ interactions most influence species’ range margins. To resolve this, we synthesize results from a broad array of models of pairwise species interactions to ask 1) Which species interactions most influence species’ range margins and 2) How many parameters must be measured to anticipate a species’ range margin. Here we focus on one species and analyse where its range margin will be in the face of a second species. Interactions may benefit (+), harm (-), or have no effect (0) on either the focal species or the second species. We use this framework to contrast the effects of all interaction types on range margins, notably competition, commensalism, amensalism, mutualism and predation. Mathematically, we derive...

Dynamics of an ant–plant-pollinator model

Communications in Nonlinear Science and Numerical Simulation, 2015

ABSTRACT In this paper, we consider plant-pollinator–ant systems in which plant-pollinator intera... more ABSTRACT In this paper, we consider plant-pollinator–ant systems in which plant-pollinator interaction and plant–ant interaction are both mutualistic, but there also exists interference of pollinators by ants. The plant-pollinator interaction can be described by a Beddington–DeAngelis formula, so we extend the formula to characterize plant-pollinator mutualisms, including the interference by ants, and form a plant-pollinator–ant model. Using dynamical systems theory, we show uniform persistence of the model. Moreover, we demonstrate conditions under which boundary equilibria are globally asymptotically stable. The dynamics exhibit mechanisms by which the three species could coexist when ants interfere with pollinators. We define a threshold in ant interference. When ant interference is strong, it can drive plant-pollinator mutualisms to extinction. Furthermore, if the ants depend on pollination mutualism for their persistence, then sufficiently strong ant interference could lead to their own extinction as well. Yet, when ant interference is weak, plant–ant and plant-pollinator mutualisms can promote the persistence of one another.

Theoretical Population Biology, 2002

Coevolved mutualisms, such as those between senita cacti, yuccas, and their respective obligate p... more Coevolved mutualisms, such as those between senita cacti, yuccas, and their respective obligate pollinators, benefit both species involved in the interaction. However, in these pollination mutualisms the pollinator's larvae impose a cost on plants through consumption of developing seeds and fruit. The effects of pollinators on benefits and costs are expected to vary with the abundance of pollinators, because large population sizes result in more eggs and larval seed-eaters. Here, we develop the hypothesis that fruit abortion, which is common in yucca, senita, and plants in general, could in some cases have the function of limiting pollinator abundance and, thereby, increasing fruit production. Using a general steady-state model of fruit production and pollinator dynamics, we demonstrate that plants involved in pollinating seed-eater mutualisms can increase their fecundity by randomly aborting fruit. We show that the ecological conditions under which fruit abortion can improve plants fecundity are not unusual. They are best met when the plant is long-lived, the population dynamics of the pollinator are much faster than those of the plant, the loss of one fruit via abortion kills a larva that would have the expectation of destroying more than one fruit through its future egg laying as an adult moth, and the effects of fruit abortion on pollinator abundance are spatially localized. We then use the approach of adaptive dynamics to find conditions under which a fruit abortion strategy based on regulating the pollinator population could feasibly evolve in this type of plantpollinator interaction. & 2002 Elsevier Science (USA)

Theoretical Ecology, 2013

Food web dynamics are well known to vary with indirect interactions, classic examples including a... more Food web dynamics are well known to vary with indirect interactions, classic examples including apparent competition, intraguild predation, exploitative competition, and trophic cascades of food chains. Such food web modules entailing predation and competition have been the focus of much theory, whereas modules involving mutualism have received far less attention. We examined an empirically common food web module involving mutualistic (N 2 ) and parasitic (N 3 ) consumers exploiting a resource of a basal mutualist (N 1 ), as illustrated by plants, pollinators, and nectar robbers. This mutualism-parasitism food web module is structurally similar to exploitative competition, suggesting that the module of two consumers exploiting a resource is unstable. Rather than parasitic consumers destabilizing the module through (−,−) indirect interactions, two mechanisms associated with the mutualism can actually enhance the persistence of the module. First, the positive feedback of mutualism favors coexistence in stable limit cycles, whereby (+,−) indirect interactions emerge in which increases in N 2 have positive effects on N 3 and increases in N 3 have negative effects on N 2 . This (+,−) indirect interaction arising from the saturating positive feedback of mutualism has broad feasibility across many types of food web modules entailing mutualism. Second, optimization of resource exploitation by the mutualistic consumer can lead to persistence of the food web module in a stable equilibrium. The mutualismparasitism food web module is a basic unit of food webs in which mutualism favors its persistence simply through density-dependent population dynamics, rather than parasitism destabilizing the module.

The American Naturalist, 2002

We develop an approach for studying population dynamics resulting from mutualism by employing fun... more We develop an approach for studying population dynamics resulting from mutualism by employing functional responses based on density-dependent benefits and costs. These functional responses express how the population growth rate of a mutualist is modified by the density of its partner. We present several possible dependencies of gross benefits and costs, and hence net effects, to a mutualist as functions of the density of its partner. Net effects to mutualists are likely a monotonically saturating or unimodal function of the density of their partner. We show that fundamental differences in the growth, limitation, and dynamics of a population can occur when net effects to that population change linearly, unimodally, or in a saturating fashion. We use the mutualism between senita cactus and its pollinating seed-eating moth as an example to show the influence of different benefit and cost functional responses on population dynamics and stability of mutualisms. We investigated two mechanisms that may alter this mutualism's functional responses: distribution of eggs among flowers and fruit abortion. Differences in how benefits and costs vary with density can alter the stability of this mutualism. In particular, fruit abortion may allow for a stable equilibrium where none could otherwise exist.

Emergence of functional responses from interactions of individuals

Oikos, 2004

2004. Testing hypotheses for excess flower production and low fruit-to-flower ratios in a pollina... more 2004. Testing hypotheses for excess flower production and low fruit-to-flower ratios in a pollinating seed-consuming mutualism. Á/ Oikos 105: 633 Á/640.

Consequences of ants and extrafloral nectar for a pollinating seed-consuming mutualism: ant satiation, floral distraction or plant defense?

Oikos, 2011

Skip to Main Content. ...

Herbivore-induced changes in plant carbon allocation: assessment of below-ground C fluxes using carbon-14

Oecologia, 1996

... J. Nathaniel Holland-Weixin Cheng DA Crossley, Jr ... By using 14C-labelling techniques, the ... more ... J. Nathaniel Holland-Weixin Cheng DA Crossley, Jr ... By using 14C-labelling techniques, the quantity of root exudates released into soil has been estimated for arable crops to be 1040% of total net carbon assimilat-ed (Barber and Martin 1976; Whipps and Lynch 1983; Whipps ...

Ann Entomol Soc Amer, 2003

Despite great variation in instar number among Insecta, no Lepidopteran has been observed to have... more Despite great variation in instar number among Insecta, no Lepidopteran has been observed to have less than four larval instars. I report in this work on the life cycle and growth of the senita moth, Upiga virescens Hulst, which forms an obligate pollinating predispersal seed-eating mutualism with senita cacti (Lophocereus schottii Engelmann) in the Sonoran Desert of North America. From 1996 to 1999, I studied larval growth and life cycle associations of U. virescens with L. schottii in the Þeld by labeling cohorts of eggs laid in ßowers and following them through pupation. All life stages of U. virescens were associated with ßowers, fruit, or cactus stems of L. schottii. Among the Þve cohorts studied, larval growth consistently conformed to DyarÕs rule. Only three larval instars were identiÞed among the Ͼ500 larvae for which head capsule widths were measured. I discuss and dismiss the feasibility of a fourth undetected instar. I then discuss selection pressures that may have contributed to the evolutionary loss of an instar, including a time and/or size constraint on larval growth, as well as the nutritional quantity and quality of larval food.

Annals of the Entomological Society of America, 2003

Despite great variation in instar number among Insecta, no Lepidopteran has been observed to have... more Despite great variation in instar number among Insecta, no Lepidopteran has been observed to have less than four larval instars. I report in this work on the life cycle and growth of the senita moth, Upiga virescens Hulst, which forms an obligate pollinating predispersal seed-eating mutualism with senita cacti (Lophocereus schottii Engelmann) in the Sonoran Desert of North America. From 1996 to 1999, I studied larval growth and life cycle associations of U. virescens with L. schottii in the Þeld by labeling cohorts of eggs laid in ßowers and following them through pupation. All life stages of U. virescens were associated with ßowers, fruit, or cactus stems of L. schottii. Among the Þve cohorts studied, larval growth consistently conformed to DyarÕs rule. Only three larval instars were identiÞed among the Ͼ500 larvae for which head capsule widths were measured. I discuss and dismiss the feasibility of a fourth undetected instar. I then discuss selection pressures that may have contributed to the evolutionary loss of an instar, including a time and/or size constraint on larval growth, as well as the nutritional quantity and quality of larval food.

Ecology Letters, Oct 1, 2009

Interactions between two populations are often defined by their interaction outcomes; that is, th... more Interactions between two populations are often defined by their interaction outcomes; that is, the positive, neutral, or negative effects of species on one another. Yet, signs of outcomes are not absolute, but vary with the biotic and abiotic contexts of interactions. Here, we develop a general theory for transitions between outcomes based on consumer-resource (C-R) interactions in which one or both species exploit the other as a resource. Simple models of C-R interactions revealed multiple equilibria, including one for species coexistence and others for extinction of one or both species, indicating that speciesÕ densities alone could determine the fate of interactions. All possible outcomes [(+ +), (+ )), () )), (+ 0), () 0), (0 0)] of species coexistence emerged merely through changes in parameter values of C-R interactions, indicating that variation in C-R interactions resulting from biotic and abiotic conditions could determine shifts in outcomes. These results suggest that C-R interactions can provide a broad mechanism for understanding context-and density-dependent transitions between interaction outcomes.

The foley catheter in the management of epistaxis

International Journal of Clinical Practice, 2001

The Foley urinary catheter has been used in the management of epistaxis for many years, yet it ha... more The Foley urinary catheter has been used in the management of epistaxis for many years, yet it has never been designed or licensed for this purpose. We performed a telephone questionnaire of senior house officers in 90 ENT departments in England and Wales. The aim was to determine how many departments used the Foley catheter for epistaxis management, whether licensed nasal balloon devices were available and if there had been any complications associated with their use. Eighty-three (92%) ENT departments in the study used the Foley catheter for epistaxis management and 44 (49%) departments had licensed balloon devices available. Only 22% of ENT senior house officers questioned were aware that the Foley catheter was not licensed for use in the nose. Most complications associated with the use of nasal balloon devices appear to be due to Foley catheters.

Discrimination among floral resources by an obligately pollinating seed-eating moth: host-marking signals and pollination and florivory cues

Evolutionary Ecology Research, 2010

Discrimination among floral resources by an obligately ... Katherine C. Horn and J. Nathaniel Hol... more Discrimination among floral resources by an obligately ... Katherine C. Horn and J. Nathaniel Holland ... Department of Ecology and Evolutionary Biology, Rice University, Houston, Texas, USA ... Background: For oviposition, some insects exploit small discrete food ...

Oecologia, Feb 22, 2001

Mutualistic interactions almost always produce both costs and benefits for each of the interactin... more Mutualistic interactions almost always produce both costs and benefits for each of the interacting species. It is the difference between gross benefits and costs that determines the net benefit and the per-capita effect on each of the interacting populations. For example, the net benefit of obligate pollinators, such as yucca and senita moths, to plants is determined by the difference between the number of ovules fertilized from moth pollination and the number of ovules eaten by the pollinator's larvae. It is clear that if pollinator populations are large, then, because many eggs are laid, costs to plants are large, whereas, if pollinator populations are small, gross benefits are low due to lack of pollination. Even though the size and dynamics of the pollinator population are likely to be crucial, their importance has been neglected in the investigation of mechanisms, such as selective fruit abortion, that can limit costs and increase net benefits. Here, we suggest that both the population size and dynamics of pollinators are important in determining the net benefits to plants, and that fruit abortion can significantly affect these. We develop a model of mutualism between populations of plants and their pollinating seed-predators to explore the ecological consequences of fruit abortion on pollinator population dynamics and the net effect on plants. We demonstrate that the benefit to a plant population is unimodal as a function of pollinator abundance, relative to the abundance of flowers. Both selective abortion of fruit with eggs and random abortion of fruit, without reference to whether they have eggs or not, can limit pollinator population size. This can increase the net benefits to the plant population by limiting the number of eggs laid, if the pollination rate remains high. However, fruit abortion can possibly destabilize the pollinator population, with negative consequences for the plant population.

Ecological conditions for fruit abortion to regulate pollinator/seed-predators and increase plant re

Journal of Ecology, 2009

Nearly all mutualisms entail the production of resources by one species that attract and reward t... more Nearly all mutualisms entail the production of resources by one species that attract and reward the species with which it interacts. As such resource production could otherwise be allocated to growth or reproduction, mutualists are predicted to minimize these investment costs. Here, we employ optimal defence theory for plant secondary compounds to evaluate plant production of extrafloral nectar (EFN) resources to attract and reward ants for resistance against herbivores. 2. Through ant exclusion and artificial herbivory experiments, we examined investment in EFN by both buds and fruits of Pachycereus schottii (senita cacti) in the Sonoran Desert of North America. We tested predictions of optimal defence theory that plants invest more in high value parts (fruits) through constitutive EFN, less in low value parts (buds) through induced EFN, and that for a given plant part (buds or fruits), constitutive and induced EFN are negatively correlated. 3. Constitutive levels of EFN were greater in fruits than in buds. Only buds showed induced EFN production following artificial herbivory. Constitutive EFN scaled positively with fruit size but not bud size. Induced EFN was negatively correlated with constitutive EFN for fruits (but not buds), suggesting a potential trade-off in these two herbivore resistance traits. 4. These results indicate that P. schottii minimizes its costs by investing in induced EFN for buds and constitutive EFN for fruits. Moreover, by shifting from induced to constitutive EFN with the morphogenesis of buds to fruits, our results show that investment in EFN can change as a particular plant tissue increases from a lower to a higher value. 5. Synthesis . Indirect defence through EFN production is in accord with that of direct defence through plant secondary compounds, thereby supporting optimal defence theory as a general framework with which to evaluate the costs of producing resources (i.e. the defence) by plants, lycaenids and homopterans to attract and reward ants for their resistance against natural enemies in protection mutualisms.

Post-hibernation movement and foraging habitat of a male Indiana bat, Myotis sodalis (Chiroptera: Vespertilionidae), in western Virginia

á Post-hibernation movement and foraging habitat of a male Indiana bat, Myotis sodalis (Chiropter... more á Post-hibernation movement and foraging habitat of a male Indiana bat, Myotis sodalis (Chiroptera:áVespertilionidae), in western Virginia. DSpace/Manakin Repository. ...

Ecology, 1999

Pollinating seed-consuming interactions are rare, but include fig-fig wasp and yucca-yucca moth i... more Pollinating seed-consuming interactions are rare, but include fig-fig wasp and yucca-yucca moth interactions, both of which are thought to be coevolved.

Emergence of functional responses from interactions of individuals

Interspecific interactions and range margins: contrasts among interaction types

Background/Question/Methods Ecologists seek to anticipate how species interactions shift a specie... more Background/Question/Methods Ecologists seek to anticipate how species interactions shift a species’ range margins (the limit of its geographic distribution). There is a great diversity of types of species interactions and at present, we lack a clear understanding of which species’ interactions most influence species’ range margins. To resolve this, we synthesize results from a broad array of models of pairwise species interactions to ask 1) Which species interactions most influence species’ range margins and 2) How many parameters must be measured to anticipate a species’ range margin. Here we focus on one species and analyse where its range margin will be in the face of a second species. Interactions may benefit (+), harm (-), or have no effect (0) on either the focal species or the second species. We use this framework to contrast the effects of all interaction types on range margins, notably competition, commensalism, amensalism, mutualism and predation. Mathematically, we derive...

Dynamics of an ant–plant-pollinator model

Communications in Nonlinear Science and Numerical Simulation, 2015

ABSTRACT In this paper, we consider plant-pollinator–ant systems in which plant-pollinator intera... more ABSTRACT In this paper, we consider plant-pollinator–ant systems in which plant-pollinator interaction and plant–ant interaction are both mutualistic, but there also exists interference of pollinators by ants. The plant-pollinator interaction can be described by a Beddington–DeAngelis formula, so we extend the formula to characterize plant-pollinator mutualisms, including the interference by ants, and form a plant-pollinator–ant model. Using dynamical systems theory, we show uniform persistence of the model. Moreover, we demonstrate conditions under which boundary equilibria are globally asymptotically stable. The dynamics exhibit mechanisms by which the three species could coexist when ants interfere with pollinators. We define a threshold in ant interference. When ant interference is strong, it can drive plant-pollinator mutualisms to extinction. Furthermore, if the ants depend on pollination mutualism for their persistence, then sufficiently strong ant interference could lead to their own extinction as well. Yet, when ant interference is weak, plant–ant and plant-pollinator mutualisms can promote the persistence of one another.

Theoretical Population Biology, 2002

Coevolved mutualisms, such as those between senita cacti, yuccas, and their respective obligate p... more Coevolved mutualisms, such as those between senita cacti, yuccas, and their respective obligate pollinators, benefit both species involved in the interaction. However, in these pollination mutualisms the pollinator's larvae impose a cost on plants through consumption of developing seeds and fruit. The effects of pollinators on benefits and costs are expected to vary with the abundance of pollinators, because large population sizes result in more eggs and larval seed-eaters. Here, we develop the hypothesis that fruit abortion, which is common in yucca, senita, and plants in general, could in some cases have the function of limiting pollinator abundance and, thereby, increasing fruit production. Using a general steady-state model of fruit production and pollinator dynamics, we demonstrate that plants involved in pollinating seed-eater mutualisms can increase their fecundity by randomly aborting fruit. We show that the ecological conditions under which fruit abortion can improve plants fecundity are not unusual. They are best met when the plant is long-lived, the population dynamics of the pollinator are much faster than those of the plant, the loss of one fruit via abortion kills a larva that would have the expectation of destroying more than one fruit through its future egg laying as an adult moth, and the effects of fruit abortion on pollinator abundance are spatially localized. We then use the approach of adaptive dynamics to find conditions under which a fruit abortion strategy based on regulating the pollinator population could feasibly evolve in this type of plantpollinator interaction. & 2002 Elsevier Science (USA)

Theoretical Ecology, 2013

Food web dynamics are well known to vary with indirect interactions, classic examples including a... more Food web dynamics are well known to vary with indirect interactions, classic examples including apparent competition, intraguild predation, exploitative competition, and trophic cascades of food chains. Such food web modules entailing predation and competition have been the focus of much theory, whereas modules involving mutualism have received far less attention. We examined an empirically common food web module involving mutualistic (N 2 ) and parasitic (N 3 ) consumers exploiting a resource of a basal mutualist (N 1 ), as illustrated by plants, pollinators, and nectar robbers. This mutualism-parasitism food web module is structurally similar to exploitative competition, suggesting that the module of two consumers exploiting a resource is unstable. Rather than parasitic consumers destabilizing the module through (−,−) indirect interactions, two mechanisms associated with the mutualism can actually enhance the persistence of the module. First, the positive feedback of mutualism favors coexistence in stable limit cycles, whereby (+,−) indirect interactions emerge in which increases in N 2 have positive effects on N 3 and increases in N 3 have negative effects on N 2 . This (+,−) indirect interaction arising from the saturating positive feedback of mutualism has broad feasibility across many types of food web modules entailing mutualism. Second, optimization of resource exploitation by the mutualistic consumer can lead to persistence of the food web module in a stable equilibrium. The mutualismparasitism food web module is a basic unit of food webs in which mutualism favors its persistence simply through density-dependent population dynamics, rather than parasitism destabilizing the module.

The American Naturalist, 2002

We develop an approach for studying population dynamics resulting from mutualism by employing fun... more We develop an approach for studying population dynamics resulting from mutualism by employing functional responses based on density-dependent benefits and costs. These functional responses express how the population growth rate of a mutualist is modified by the density of its partner. We present several possible dependencies of gross benefits and costs, and hence net effects, to a mutualist as functions of the density of its partner. Net effects to mutualists are likely a monotonically saturating or unimodal function of the density of their partner. We show that fundamental differences in the growth, limitation, and dynamics of a population can occur when net effects to that population change linearly, unimodally, or in a saturating fashion. We use the mutualism between senita cactus and its pollinating seed-eating moth as an example to show the influence of different benefit and cost functional responses on population dynamics and stability of mutualisms. We investigated two mechanisms that may alter this mutualism's functional responses: distribution of eggs among flowers and fruit abortion. Differences in how benefits and costs vary with density can alter the stability of this mutualism. In particular, fruit abortion may allow for a stable equilibrium where none could otherwise exist.

Emergence of functional responses from interactions of individuals

Oikos, 2004

2004. Testing hypotheses for excess flower production and low fruit-to-flower ratios in a pollina... more 2004. Testing hypotheses for excess flower production and low fruit-to-flower ratios in a pollinating seed-consuming mutualism. Á/ Oikos 105: 633 Á/640.

Consequences of ants and extrafloral nectar for a pollinating seed-consuming mutualism: ant satiation, floral distraction or plant defense?

Oikos, 2011

Skip to Main Content. ...

Herbivore-induced changes in plant carbon allocation: assessment of below-ground C fluxes using carbon-14

Oecologia, 1996

... J. Nathaniel Holland-Weixin Cheng DA Crossley, Jr ... By using 14C-labelling techniques, the ... more ... J. Nathaniel Holland-Weixin Cheng DA Crossley, Jr ... By using 14C-labelling techniques, the quantity of root exudates released into soil has been estimated for arable crops to be 1040% of total net carbon assimilat-ed (Barber and Martin 1976; Whipps and Lynch 1983; Whipps ...