Mary F. Willson

Bio: Mary F. Willson is an academic researcher. The author has contributed to research in topics: Sexual selection & Sexual reproduction. The author has an hindex of 5, co-authored 6 publications receiving 1300 citations.

Sexual Selection in Plants

Abstract: The concept of sexual selection (intrasexual competition for mates and mate preference) is used in revising the classical explanation of dioecy in plants. Male and female functions of hermaphroditic flowers can be subject to different sexual selection pressures, which may conceivably lead to the separation of male and female structures. This suggestion does not exclude genetic advantages that may accrue from outcrossing; the two aspects of selection probably operated together in the evolution of dioecy. The hypothesis regarding the importance of sexual selection could be tested by monitoring variation in individual fitness via pollen donation and via ovule maturation. The evolution of pollinia and other large pollen dispersal units is also viewed in terms of sexual selection. Availability of a reliable pollen vector is a prerequisite to the evolution of pollen packages. From the point of view of a flower functioning as a male, large PDU's ensure fertilization of more ovules and possible preemption of stig...

Mate choice in plants: tactics, mechanisms and consequences.

Abstract: This book maintains that higher plants manifest some degree of sexual selection, and it begins to build a framework that unifies many features of plant reproduction previously considered unrelated Reviewing evidence for sexual selection in plants, the authors discuss possible male-female interactions, concluding with an extensive set of hypotheses for testing Mechanisms that could be employed in sexual selection in plants include various cellular mechanisms, such as both nuclear and cytoplasmic genetics, B chromosomes, and paternal contributions to the zygote, as well as abortion, double fertilization, delayed fertilization, and certain forms of polyembryony This study compares the consequences of these processes for the evolution of mate choice in "gymnosperms" and angiosperms

Sexual selection in plants : perspective and overview

Abstract: Sexual selection has a long history of controversy, which shows little sign of waning. The more recent application of the concept to plants continues the historical trend. In recent years, the number of articles on sexual selection has grown; in journals that regularly accept articles on both animals and plants, the frequency of those on sexual selection in plants has grown dramatically. However, articles that examine processes and outcomes related to sexual selection in plants often do not use the term sexual selection, a tendency that indicates the aura of controversy in the field. In the decade since the last broad review of sexual selection in plants, considerable progress has been made in understanding both process and outcome of sexual selection in the botanical world. I have argued that sexual selection can occur at any phase of the reproductive process, from "courtship" to postnatal stages, in plants as well as animals. Most of this work has addressed events or traits before fertilization, but pos...

Sexual selection in plants and animals.

Abstract: Belated recognition of the evolutionary import of reproductive success through male function in plants has led to the application of sexual selection theory to these organisms. Recent work has shown that there are many parallels, related to sexual selection, in the reproductive processes of animals and of plants, although the proximate mechanisms and evolutionary constraints sometimes differ.

Flower and Fruit Abortion: Proximate Causes and Ultimate Functions

Abstract: During the past decade ecologist have devoted considerable energy to demographic studies of flowers and fruits between anthesis and dispersal. These efforts have led to the growing realization that the number of flowers and fruits and the way they are clustered in time and space influence pollinator attraction...

The descent of man and selection in relation to sex

Abstract: ION, GENERAL CONCEPTIONS, SELF-CONSCIOUSNESS, MENTAL INDIVIDUALITY. It would be very difficult for any one with even much more knowledge than I possess, to determine how far animals exhibit any traces of these high mental powers. This difficulty arises from the impossibility of judging what passes through the mind of an animal; and again, the fact that writers differ to a great extent in the meaning which they attribute to the above terms, causes a further difficulty. If one may judge from various articles which have been published lately, the greatest stress seems to be laid on the supposed entire absence in animals of the power of abstraction, or of forming general concepts. But when a dog sees another dog at a distance, it is often clear that he perceives that it is a dog in the abstract; for when he gets nearer his whole manner suddenly changes, if the other dog be a friend. A recent writer remarks, that in all such cases it is a pure assumption to assert that the mental act is not essentially of the same nature in the animal as in man. If either refers what he perceives with his senses to a mental concept, then so do both. (44. Mr. Hookham, in a letter to Prof. Max Muller, in the 'Birmingham News,' May, 1873.) When I say to my terrier, in an eager voice (and I have made the trial many times), "Hi, hi, where is it?" she at once takes it as a sign that something is to be hunted, and generally first looks quickly all around, and then rushes into the nearest thicket, to scent for any game, but finding nothing, she looks up into any neighbouring tree for a squirrel. Now do not these actions clearly shew that she had in her mind a general idea or concept that some animal is to be discovered and hunted? It may be freely admitted that no animal is self-conscious, if by this term it is implied, that he reflects on such points, as whence he comes or whither he will go, or what is life and death, and so forth. But how can we feel sure that an old dog with an excellent memory and some power of imagination, as shewn by his dreams, never reflects on his past pleasures or pains in the chase? And this would be a form of self-consciousness. On the other hand, as Buchner (45. 'Conferences sur la Theorie Darwinienne,' French translat. 1869, p. 132.) has remarked, how little can the hardworked wife of a degraded Australian savage, who uses very few abstract words, and cannot count above four, exert her self-consciousness, or reflect on the nature of her own existence. It is generally admitted, that the higher animals possess memory, attention, association, and even some imagination and reason. If these powers, which differ much in different animals, are capable of improvement, there seems no great improbability in more complex faculties, such as the higher forms of abstraction, and selfconsciousness, etc., having been evolved through the development and combination of the simpler ones. It has been urged against the views here maintained that it is impossible to say at what point in the ascending scale animals become capable of abstraction, etc.; but who can say at what age this occurs in our young children? We see at least that such powers

Plant invasions--the role of mutualisms.

Abstract: Many introduced plant species rely on mutualisms in their new habitats to overcome barriers to establishment and to become naturalized and, in some cases, invasive. Mutualisms involving animal-mediated pollination and seed dispersal, and symbioses between plant roots and microbiota often facilitate invasions. The spread of many alien plants, particularly woody ones, depends on pollinator mutualisms. Most alien plants are well served by generalist pollinators (insects and birds), and pollinator limitation does not appear to be a major barrier for the spread of introduced plants (special conditions relating to Ficus and orchids are described). Seeds of many of the most notorious plant invaders are dispersed by animals, mainly birds and mammals. Our review supports the view that tightly coevolved, plant-vertebrate seed dispersal systems are extremely rare. Vertebrate-dispersed plants are generally not limited reproductively by the lack of dispersers. Most mycorrhizal plants form associations with arbuscular mycorrhizal fungi which, because of their low specificity, do not seem to play a major role in facilitating or hindering plant invasions (except possibly on remote islands such as the Galapagos which are poor in arbuscular mycorrhizal fungi). The lack of symbionts has, however, been a major barrier for many ectomycorrhizal plants, notably for Pinus spp. in parts of the southern hemisphere. The roles of nitrogen-fixing associations between legumes and rhizobia and between actinorhizal plants and Frankia spp. in promoting or hindering invasions have been virtually ignored in the invasions literature. Symbionts required to induce nitrogen fixation in many plants are extremely widespread, but intentional introductions of symbionts have altered the invasibility of many, if not most, systems. Some of the world's worst invasive alien species only invaded after the introduction of symbionts. Mutualisms in the new environment sometimes re-unite the same species that form partnerships in the native range of the plant. Very often, however, different species are involved, emphasizing the diffuse nature of many (most) mutualisms. Mutualisms in new habitats usually duplicate functions or strategies that exist in the natural range of the plant. Occasionally, mutualisms forge totally novel combinations, with profound implications for the behaviour of the introduced plant in the new environment (examples are seed dispersal mutualisms involving wind-dispersed pines and cockatoos in Australia; and mycorrhizal associations involving plant roots and fungi). Many ecosystems are becoming more susceptible to invasion by introduced plants because: (a) they contain an increasing array of potential mutualistic partners (e.g. generalist frugivores and pollinators, mycorrhizal fungi with wide host ranges, rhizobia strains with infectivity across genera); and (b) conditions conductive for the establishment of various alien/alien synergisms are becoming more abundant. Incorporating perspectives on mutualisms in screening protocols will improve (but not perfect) our ability to predict whether a given plant species could invade a particular habitat.

Pollen limitation of plant reproduction: Ecological and evolutionary causes and consequences

Abstract: 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...

The costs of reproduction in plants

Abstract: Contents Summary321 I. Introduction321 II. Theory on costs of reproduction322 III. Methodological aspects324 IV. Empirical evidence328 V. Plant size and costs of reproduction330 VI. Costs of reproduction in sexually dimorphic plants331 VII. Compensation of the costs333 VIII. Concluding comments and future perspectives336 Acknowledgements337 References337 Summary This review reports on the processes associated with costs of reproduction, including some theoretical considerations, definitions and methodological aspects, followed by a list of the situations where costs are difficult to find. Despite some exceptions, case studies, examined by trade-offs between reproduction and other life-history traits, generally support the predictions of the cost of reproduction hypothesis. The cost of reproduction as an evolutionary determinant of sexual dimorphism in life history traits in dioecious species was specifically tested, considering that the higher cost of reproduction in females has driven the life history traits related to sexual dimorphism. Females of woody dioecious species were consistently smaller than males supporting the costs of reproduction hypothesis. By contrast, females of herbaceous perennials were generally the larger sex, which did not fit the expectations of the hypothesis. Finally, the mechanisms that enable the compensation of the reproductive costs are detailed, including the plastic responses of photosynthesis and growth, the effects of the timing of investment, plant architecture and plant physiological integration.