Benefits Of Self Research Articles

ALTERNATIVE REPRODUCTIVE STRATEGIES IN THE PROGENETIC TREMATODE COITOCAECUM PARVUM: COMPARISON OF SELFING AND MATING WORMS

The progenetic opecoelid trematode Coitocaecum parvum can reproduce either precociously by selfing in its second intermediate amphipod host or by mating in its normal definitive fish host. In this study, we describe and compare the infection parameters and some life history traits of both egg-producing worms and non-egg producing worms in both their second intermediate and definitive hosts. We showed that 58% of worms start to produce eggs while still in the amphipod. The relative abundance of progenetic worms increased with amphipod size, and egg-producing worms achieved greater size in amphipods than in fish. These 2 findings support the reproductive insurance hypothesis. No difference in size was revealed between eggs produced in the amphipods and those produced in the fish. Although more information is needed to thoroughly assess the respective costs and benefits of selfing and mating in this species, our conclusion is that adopting progenesis may have few, if any, long-term negative consequences for the parasite.

Using a cost–benefit approach to understand the evolution of self‐fertilization in plants: the perplexing case of Aquilegia canadensis (Ranunculaceae)

AbstractPlants exhibit tremendous variation in whether mating occurs via self‐fertilization versus outcrossing, and many species practice a mixture of both. In theory, the evolution of selfing is influenced by a few large costs and benefits, and the benefits of selfing should be balanced by its costs at equilibrium. We have attempted a cost–benefit analysis of selfing, using population genetic surveys, experimental manipulations and quantitative genetics to a spring‐flowering, short‐lived perennial, Aquilegia canadensis. This species invests heavily in large, nectar‐rich flowers but achieves full seed set in the absence of pollinators by automonous autogamy, and selfs 76% of its seed in natural populations. Floral emasculations reveal that 75% of selfing occurs via autogamy, which increases per‐flower seed production (reproductive assurance), but pre‐empts ovules and resources that could be used to make outcrossed seed (seed discounting). This is costly because outcrossed progeny appear to survive to maturity 10‐fold more often than selfed progeny. Almost all the apparent nonautogamous selfing involves cross‐pollination between relatives (biparental inbreeding). This could facilitate the evolution of mixed mating, but not when inbreeding is so strong. Though selfing seems strongly disadvantageous, A. canadensis exhibits striking heritable variation in the separation between anthers and stigmas within flowers (herkogamy), which correlates negatively with selfing. This suggests that the mating system is at equilibrium. There is no applicable theoretical explanation for high selfing in the face of strong inbreeding depression, which occurs in a variety of plants. Understanding the evolution of these enigmatic mating systems remains a major challenge.

Interrelationships Among Inbreeding Depression, Plasticity in the Self-incompatibility System, and the Breeding System of Campanula rapunculoides L. (Campanulaceae)

Abstract The evolution of breeding systems in plants is often viewed as a balance between the adverse consequences of selfing (inbreeding depression and the loss of opportunities to sire seeds on conspecifics) and the benefits of selfing (a genetic transmission advantage and reproductive assurance when cross pollen limits seed production). In this paper we examine the genetic and environmental causes of variation in the expression of self-incompatibility (SI) in Campanula rapunculoides and explore the consequences of this variation on the breeding system. Campanula rapunculoides has an S-RNase based SI system similar to that described in the Solanaceae. However, our studies of plants from two natural populations have revealed that the flowers of most individuals are self-incompatible when they first open but become more self fertile as the flowers age. Moreover, when both cross and self pollen are deposited onto the stigmas of older flowers, the cross pollen tubes grow faster and sire a disproportionate number of the seeds. In short, self-fertilization occurs only after most opportunities for outcrossing have occurred. We also found that there is significant heritable genetic variation in the population for the strength of SI in young and old flowers and for the amount of breakdown in SI indicating that natural selection could operate on the strength of SI and its breakdown. In a multigenerational study, we used controlled crosses to create families of plants with a range of inbreeding coefficients (0, 0.25, 0.5 and 0.75). We found that fitness declined significantly over the range of inbreeding coefficients and that the decline in fitness was less for families derived from weak SI phenotypes. Consequently, it is only advantageous for C. rapunculoides to produce selfed seed when seed production is limited by the availability of cross pollen. Because of plasticity in the SI system,C. rapunculoides has a breeding system that combines the best of both worlds.

ROLE-WISHES AND GENERAL WISHES OF CHILDREN AND ADOLESCENTS

Wishing is a favorite pastime in our culture and is allowed considerable latitude. Children are permitted, even encouraged, to make and express wishes beyond the limits of allowable actions and demands, and beyond the limits of probable attainment. Wishes are goal-directed and express values. They indicate areas of dissatisfaction and levels of aspiration in the life-space of the wisher. They constitute an as yet insufficiently exploited resource for knowledge of child and adolescent development. Most studies of children's wishes been based on an essentially unstructured form of request in obtaining responses. The child is asked, in somewhat varying ways, to state what he would wish if his wishes could come true. In general, the analysis of responses has shown a high frequency of wishes for material objects and possessions, decreasing with age and being replaced by wishes for more general and inclusive benefits for self and others; a tendency for wishes to be predominantly extrovert rather than introvert, with a low incidence of wishes relating to personal shortcomings (4, 5); and a tendency for wishes to be concrete and realistic rather than abstract and irrealistic, but becoming more general with increasing age (4, 5, 9, 10, Ii). Sex differences been found indicating a higher interest among boys in personal achievement and possessions, and among girls in social and family relationships (4, Ii). It may be suspected, however, that wish responses are influenced by the form of request and by conditions under which responses are obtained. Boynton (i) and Gray (2), for example, asked the children what they would ask for if they could have anything they wanted. The responses were overwhelmingly in terms of material objects and possessions. Children's birthday wishes for their friends were collected by Wilson (6, 7), who interpreted these as projected wishes for self. His findings yielded significantly higher frequencies of wishes relating to vocations, activities and general benefits for self and fewer wishes for specific objects and possessions than were obtained from comparable groups in other studies (e.g., see Jersild, 4). Furthermore, the low frequency of some responses (e.g., relief from personal shortcomings, to be smarter, better looking, etc.) may not be indicative of the strength of these interests, but a function of the form of the request. This might hold in general with respect to the intro-