Martin Burd - Academia.edu (original) (raw)
Papers by Martin Burd
Evolutionary Ecology, 2016
Proceedings of the National Academy of Sciences, 2006
As pollinators decline globally, competition for their services is expected to intensify, and thi... more As pollinators decline globally, competition for their services is expected to intensify, and this antagonism may be most severe where the number of plant species is the greatest. Using metaanalysis and comparative phylogenetic analysis, we provide a global-scale test of whether reproduction becomes more limited by pollen receipt (pollen limitation) as the number of coexisting plant species increases. As predicted, we find a significant positive relationship between pollen limitation and species richness. In addition, this pattern is particularly strong for species that are obligately outcrossing and for trees relative to herbs or shrubs. We suggest that plants occurring in species-rich communities may be more prone to pollen limitation because of interspecific competition for pollinators. As a consequence, plants in biodiversity hotspots may have a higher risk of extinction and͞or experience increased selection pressure to specialize on certain pollinators or diversify into different phenological niches. The combination of higher pollen limitation and habitat destruction represents a dual risk to tropical plant species that has not been previously identified.
New Phytologist, 2013
Colour signals are a major cue in putative pollination syndromes. There is evidence that the refl... more Colour signals are a major cue in putative pollination syndromes. There is evidence that the reflectance spectra of many flowers target the distinctive visual discrimination abilities of hymenopteran insects, but far less is known about bird-pollinated flowers. Birds are hypothesized to exert different selective pressures on floral colour compared with hymenopterans because of differences in their visual systems.
Ecology, 2004
Determining whether seed production is pollen limited has been an area of intensive empirical stu... more Determining whether seed production is pollen limited has been an area of intensive empirical study over the last two decades. Yet current evidence does not allow satisfactory assessment of the causes or consequences of pollen limitation. Here, we critically evaluate existing theory and issues concerning pollen limitation. Our main conclusion is that a change in approach is needed to determine whether pollen limitation reflects random fluctuations around a pollen-resource equilibrium, an adaptation to stochastic pollination environments, or a chronic syndrome caused by an environmental perturbation. We formalize and extend D. Haig and M. Westoby's conceptual model, and illustrate its use in guiding research on the evolutionary consequences of pollen limitation, i.e., whether plants evolve or have evolved to ameliorate pollen limitation. This synthesis also reveals that we are only beginning to understand when and how pollen limitation at the plant level translates into effects on plant population dynamics. We highlight the need for both theoretical and empirical approaches to gain a deeper understanding of the importance of life-history characters, Allee effects, and environmental perturbations in population declines mediated by pollen limitation. Lastly, our synthesis identifies a critical need for research on potential effects of pollen limitation at the community and ecosystem levels.
Annual Review of Ecology, Evolution, and Systematics, 2005
■ Abstract Quantifying the extent to which seed production is limited by the availability of poll... more ■ Abstract Quantifying the extent to which seed production is limited by the availability of pollen has been an area of intensive empirical study over the past few decades. Whereas theory predicts that pollen augmentation should not increase seed production, numerous empirical studies report significant and strong pollen limitation. Here, we use a variety of approaches to examine the correlates of pollen limitation in an effort to understand its occurrence and importance in plant evolutionary ecology. In particular, we examine the role of recent ecological perturbations in influencing pollen limitation and discuss the relation between pollen limitation and plant traits. We find that the magnitude of pollen limitation observed in natural populations depends on both historical constraints and contemporary ecological factors.
American Journal of Botany, 2009
The number of ovules per flower varies over several orders of magnitude among angiosperms. Here w... more The number of ovules per flower varies over several orders of magnitude among angiosperms. Here we consider evidence that stochastic uncertainty in pollen receipt and ovule fertilization has been a selective factor in the evolution of ovule number per flower. We hypothesize that stochastic variation in floral mating success creates an advantage to producing many ovules per flower because a plant will often gain more fitness from occasional abundant seed production in randomly successful flowers than it loses in resource commitment to less successful flowers. Greater statistical dispersion in pollination and fertilization among flowers increases the frequency of windfall success, which should increase the strength of selection for greater ovule number per flower. We therefore looked for evidence of a positive relationship between ovule number per flower and the statistical dispersion of pollen receipt or seed number per flower in a comparative analysis involving 187 angiosperm species. We found strong evidence of such a relationship. Our results support the hypothesis that unpredictable variation in mating success at the floral level has been a factor in the evolution of ovule packaging in angiosperms.
Oecologia, 2015
Plant associations with protective ants are widespread among angiosperms, but carry the risk that... more Plant associations with protective ants are widespread among angiosperms, but carry the risk that 3 ants will deter pollinators as well as herbivores. Such conflict, and adaptations to ameliorate or 4 prevent the conflict, have been documented in African and neotropical acacias. Ant-acacia 5 associations occur in Australia but little is known of their ecology. Moreover, recent phylogenetic 6 evidence indicates that Australian acacias are only distantly related to African and American 7 acacias, providing an intercontinental natural experiment in management of ant-pollinator 8 conflict. We examined four populations of Acacia myrtifolia over a 400 km environmental 9 gradient in southeastern Australia using ant and pollinator exclusion as well as direct observation 10 of ants and pollinators to assess the potential for ant-pollinator conflict to affect seed set. Native 11 bees were the only group of floral visitors whose visitation rates were a significant predictor of 12 fruiting success, although beetles and wasps may play an important role as "insurance" 13 pollinators. We found no increase in pollinator visitation or fruiting success following ant 14 exclosure, even with large sample sizes and effective exclusion. Because ants are facultative 15 visitors to A. myrtifolia plants, their presence may be insufficient to interfere greatly with floral 16
Evolutionary Ecology, 2016
Proceedings of the National Academy of Sciences, 2006
As pollinators decline globally, competition for their services is expected to intensify, and thi... more As pollinators decline globally, competition for their services is expected to intensify, and this antagonism may be most severe where the number of plant species is the greatest. Using metaanalysis and comparative phylogenetic analysis, we provide a global-scale test of whether reproduction becomes more limited by pollen receipt (pollen limitation) as the number of coexisting plant species increases. As predicted, we find a significant positive relationship between pollen limitation and species richness. In addition, this pattern is particularly strong for species that are obligately outcrossing and for trees relative to herbs or shrubs. We suggest that plants occurring in species-rich communities may be more prone to pollen limitation because of interspecific competition for pollinators. As a consequence, plants in biodiversity hotspots may have a higher risk of extinction and͞or experience increased selection pressure to specialize on certain pollinators or diversify into different phenological niches. The combination of higher pollen limitation and habitat destruction represents a dual risk to tropical plant species that has not been previously identified.
New Phytologist, 2013
Colour signals are a major cue in putative pollination syndromes. There is evidence that the refl... more Colour signals are a major cue in putative pollination syndromes. There is evidence that the reflectance spectra of many flowers target the distinctive visual discrimination abilities of hymenopteran insects, but far less is known about bird-pollinated flowers. Birds are hypothesized to exert different selective pressures on floral colour compared with hymenopterans because of differences in their visual systems.
Ecology, 2004
Determining whether seed production is pollen limited has been an area of intensive empirical stu... more Determining whether seed production is pollen limited has been an area of intensive empirical study over the last two decades. Yet current evidence does not allow satisfactory assessment of the causes or consequences of pollen limitation. Here, we critically evaluate existing theory and issues concerning pollen limitation. Our main conclusion is that a change in approach is needed to determine whether pollen limitation reflects random fluctuations around a pollen-resource equilibrium, an adaptation to stochastic pollination environments, or a chronic syndrome caused by an environmental perturbation. We formalize and extend D. Haig and M. Westoby's conceptual model, and illustrate its use in guiding research on the evolutionary consequences of pollen limitation, i.e., whether plants evolve or have evolved to ameliorate pollen limitation. This synthesis also reveals that we are only beginning to understand when and how pollen limitation at the plant level translates into effects on plant population dynamics. We highlight the need for both theoretical and empirical approaches to gain a deeper understanding of the importance of life-history characters, Allee effects, and environmental perturbations in population declines mediated by pollen limitation. Lastly, our synthesis identifies a critical need for research on potential effects of pollen limitation at the community and ecosystem levels.
Annual Review of Ecology, Evolution, and Systematics, 2005
■ Abstract Quantifying the extent to which seed production is limited by the availability of poll... more ■ Abstract Quantifying the extent to which seed production is limited by the availability of pollen has been an area of intensive empirical study over the past few decades. Whereas theory predicts that pollen augmentation should not increase seed production, numerous empirical studies report significant and strong pollen limitation. Here, we use a variety of approaches to examine the correlates of pollen limitation in an effort to understand its occurrence and importance in plant evolutionary ecology. In particular, we examine the role of recent ecological perturbations in influencing pollen limitation and discuss the relation between pollen limitation and plant traits. We find that the magnitude of pollen limitation observed in natural populations depends on both historical constraints and contemporary ecological factors.
American Journal of Botany, 2009
The number of ovules per flower varies over several orders of magnitude among angiosperms. Here w... more The number of ovules per flower varies over several orders of magnitude among angiosperms. Here we consider evidence that stochastic uncertainty in pollen receipt and ovule fertilization has been a selective factor in the evolution of ovule number per flower. We hypothesize that stochastic variation in floral mating success creates an advantage to producing many ovules per flower because a plant will often gain more fitness from occasional abundant seed production in randomly successful flowers than it loses in resource commitment to less successful flowers. Greater statistical dispersion in pollination and fertilization among flowers increases the frequency of windfall success, which should increase the strength of selection for greater ovule number per flower. We therefore looked for evidence of a positive relationship between ovule number per flower and the statistical dispersion of pollen receipt or seed number per flower in a comparative analysis involving 187 angiosperm species. We found strong evidence of such a relationship. Our results support the hypothesis that unpredictable variation in mating success at the floral level has been a factor in the evolution of ovule packaging in angiosperms.
Oecologia, 2015
Plant associations with protective ants are widespread among angiosperms, but carry the risk that... more Plant associations with protective ants are widespread among angiosperms, but carry the risk that 3 ants will deter pollinators as well as herbivores. Such conflict, and adaptations to ameliorate or 4 prevent the conflict, have been documented in African and neotropical acacias. Ant-acacia 5 associations occur in Australia but little is known of their ecology. Moreover, recent phylogenetic 6 evidence indicates that Australian acacias are only distantly related to African and American 7 acacias, providing an intercontinental natural experiment in management of ant-pollinator 8 conflict. We examined four populations of Acacia myrtifolia over a 400 km environmental 9 gradient in southeastern Australia using ant and pollinator exclusion as well as direct observation 10 of ants and pollinators to assess the potential for ant-pollinator conflict to affect seed set. Native 11 bees were the only group of floral visitors whose visitation rates were a significant predictor of 12 fruiting success, although beetles and wasps may play an important role as "insurance" 13 pollinators. We found no increase in pollinator visitation or fruiting success following ant 14 exclosure, even with large sample sizes and effective exclusion. Because ants are facultative 15 visitors to A. myrtifolia plants, their presence may be insufficient to interfere greatly with floral 16