Search results for "Sexual Reproduction"
showing 10 items of 95 documents
Pollen-pollen interactions in Betula pendula in vitro
1998
Direct pollen interactions, as well as interactions mediated by a recipient, can have a remarkable influence on pollen fertilization ability. Under conditions of pollen competition it could be advantageous if pollen grains interfered with the germination of other pollen. The aim of this study was to find out if there are direct negative or positive pollen–pollen interactions between pollen grains from genetically slightly different donors. The in vitro germinability of the pollen from several Betula pendula Roth clones was investigated. The pollen interactions between the clones were examined pairwise by using equal pollen mixtures. In three of the eight cases the germination percentage of …
Salinity effects on asexual reproduction of Carybdea sp. (Cnidaria: Cubozoa)
2014
6 pages, 2 figures, 1 table, supplementary data http://plankt.oxfordjournals.org/content/36/2/585/suppl/DC1
Impact of polyploidy on fertility variation of Mediterranean Arundo L. (Poaceae)
2015
International audience; Failure of seed production in the genus Arundo L. (Poaceae) is often attributed to polyploidy. This study tested the impact of two ploidy levels (2n = 12 and 18x) on the fertility of four Mediterranean Arundo. Viable pollen was screened from its production to its germination, and seed occurrence was monitored in admixture or isolated conditions. In addition, insights on restructuration of polyploid genornes were analysed using molecular cytogenetics. Our results show that high ploidy levels do not automatically induce failure of sexual reproduction. The two ploidy levels are able to produce viable pollen and seed set depending on species and cultural conditions. The …
The red tooth hypothesis: A computational model of predator-prey relations, protean escape behavior and sexual reproduction
2009
This paper presents an extension of the Red Queen Hypothesis (hereafter, RQH) that we call the Red Tooth Hypothesis (RTH). This hypothesis suggests that predator-prey relations may play a role in the maintenance of sexual reproduction in many higher animals. RTH is based on an interaction between learning on the part of predators and evolution on the part of prey. We present a simple predator-prey computer simulation that illustrates the effects of this interaction. This simulation suggests that the optimal escape strategy from the prey's standpoint would be to have a small number of highly reflexive, largely innate (and, therefore, very fast) escape patterns, but that would also be unlearn…
Investigating the origin of parthenogenesis and ploidy level in Dahlica fennicella (Lepidoptera: Psychidae)
2013
The theories for the predominance of sexual reproduction predict that parthenogens should have no long-term evolutionary potential due to the lack of genetic recombination, despite short term advantages. Although parthenogenesis is rare among high order animals, true parthenogens can be found in various taxa. The intriguing question of the proliferation and persistence of parthenogenetic species needs investigation. An ideal species for such research is a parthenogenetic mont Dahlica fennicella that appears to be as equally successful as other coexisting sexual species. We investigated whether high ploidy level of D. fennnicella is due to hybridization between closely related sexual species…
Mating system variation inVeronica(Plantaginaceae): inferences from pollen/ovule ratios and other reproductive traits
2012
The pollen–ovule ratio (P/O) is commonly used to estimate the mode of sexual reproduction in flowering plants. In previous studies, a clear correspondence has been detected between this character and the degree of autogamy. We here investigate variation in this character and its expected correlates in the genus Veronica (Plantaginaceae). Pollen–ovule ratios of 45 species representing eleven percent of all the species in the genus were investigated and compared with results from crossing experiments from previous studies. In addition, multiple populations of 17 of the 45 studied species were sampled and a controlled-environment experiment was conducted to evaluate the extent of intraspecific…
Flowering and fruiting phenology and breeding system ofCistus albidusL.
1995
Summary The flowering and fruiting phenology and breeding system of Cistus albidus L. are studied. Four phases are established for the development of the flower, which remains open for a period of less than 14hrs, although this time—span can be further reduced if environmental conditions are unfavourable. Only 65.6 % flowers develop ripe fruits, the greatest losses occurring in the change from flower to unripe fruit. H is a xenogamous species with a PAD ratio of 5.426 ±816. Experimentally, fruits may be formed by autogamy through manual pollination, although this does not occur spontaneously. There is recognition by the plant of its own pollen tube, which reduced the production of fruits by…
Molecular characterization of Colletotrichum strains derived from strawberry
1999
Strains of Colletotrichum species derived from diseased strawberry plants from a wide geographical range were studied using mitochondrial and ribosomal DNA RFLPs, and acetyl and propionyl esterase isoenzymes. Two major species aggregates were detected, centred on C. acutatum and C. gloeosporioides respectively, with significant further subdivision. There were apparent discrepancies in the hierarchical nesting of some taxon groups based on the different molecular techniques. Strains assigned to C. acutatum fell into several rDNA RFLP groups, but there was less variation in mtDNA RFLP band patterns. There appears to be at least one probably clonal population in the U.S.A. which is also presen…
Sexual selection and intelligence: Does sexual reproduction drive the evolution of intelligence?
2009
Abstract The basal hypothesis discussed here is the idea that brain architecture could be plastic on a very basal, genetic level due to sexual recombination and reassortment of alleles of genes related to brain development, e.g., neuronal cell adhesion molecules (NCAMs) and others. The role of sexual reassortment leads the study of brain development, species behavior and intelligence to a new version of the so-called “Red Queen Hypothesis”: using the mechanism described here, a kind of runaway selection mechanism seems to arise. Even if NCAMs are almost constant within an individual, they seem to act very differently at the population level and so the role of reassorting polymorphic NCAM- (…
Differential competitive ability between sexes in the dioecious Antennaria dioica (Asteraceae)
2012
† Background and Aims Differences in competitive ability between the sexes of dioecious plants are expected as a result of allocation trade-offs associated with sex-differential reproductive costs. However, the available data on competitive ability in dioecious plants are scarce and contradictory. In this study sexual competition was eval- uated using the dioecious plant Antennaria dioica in a common garden transplantation experiment. † Methods Male and female plants were grown for 3 years either in isolation, or in competition with a plant of the same sex or the opposite sex. Flowering phenology, sexual and asexual reproduction, plant growth, nutrient content and arbuscular mycorrhizal col…