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Viable Offspring (viable + offspring)
Selected AbstractsOviposition preference and larval performance within a diverging lineage of lycaenid butterfliesECOLOGICAL ENTOMOLOGY, Issue 3 2004Matthew L. Forister Abstract. 1. The butterfly genus Mitoura in Northern California includes three nominal species associated with four host plants having parapatric or interdigitated ranges. Genetic analyses have shown the taxa to be very closely related, and adults from all host backgrounds will mate and produce viable offspring in the laboratory. Oviposition preference and larval performance were investigated with the aim of testing the hypothesis that variation in these traits can exist in a system in which non-ecological barriers to gene flow (i.e. geographic barriers and genetic incompatibilities) appear to be minimal. 2. Females were sampled from 12 locations throughout Northern California, including sympatric and parapatric populations associated with the four different host-plant species. Oviposition preference was assayed by confining wild-caught females with branches of all four host species and counting the number of eggs laid on each. Offspring were reared on the same host species and two measures of larval success were taken: per cent survival and pupal weight. 3. For populations associated with one of the hosts, incense cedar, the preference,performance relationship is simple: the host that females chose is the plant which results in the highest pupal weights for offspring. The preference,performance relationship for populations associated with the other hosts is more complex and may reflect different levels of local adaptation. The variation in preference and performance reported here suggests that these traits can evolve when non-ecological barriers to gene flow are low, and that differences in these traits may be important for the evolution of reproductive isolation within Mitoura. [source] THE EVOLUTION OF FILIAL CANNIBALISM AND FEMALE MATE CHOICE STRATEGIES AS RESOLUTIONS TO SEXUAL CONFLICT IN FISHESEVOLUTION, Issue 2 2000Kai Lindström Abstract., Filial cannibalism (the consumption of one's own viable offspring) is common among fish with paternal care. In this study, I use a computer simulation to study simultaneous evolution of male filial cannibalism and female mate choice. Under certain conditions, selection on parental males favors filial cannibalism. When filial cannibalism increases a male's probability to raise the current brood successfully, filial cannibalism also benefits the female. However, when egg eating is a male investment into future reproduction, a conflict between female and male interests emerges. Here I investigate how female discrimination against filial cannibals affects evolution of filial cannibalism and how different female choice criteria perform against filial cannibalism. The introduction of discriminating females makes the fixation of filial cannibalism less likely. I introduced three different female choice criteria: (1) females who could discern a male's genotype, that is, whether the male was going to eat eggs as an investment in future reproductive events; (2) energy-choosing females that preferred to mate with males who had enough energy reserves to live through the current brood cycle without consuming eggs; and (3) females that preferred to mate with already mated males, that is, males with eggs in their nest. Genotype choice never coexisted with filial cannibals at fixation and filial cannibals were unable to invade a population with genotype-choosing females. Energy choice was successful only when males had high energy reserves and were less dependent on filial cannibalism as an alternative energy source. The egg choosers frequently coexisted with the cannibals at fixation. When the female strategies were entered simultaneously, the most frequent outcome for low mate sampling costs was that both the cannibals and the egg choice was fixed and all other strategies went extinct. These results suggest that sexual conflicts may not always evolve toward a resolution of the conflict, but sometimes the stable state retains the conflict. In the present case, this was because the egg-preference strategy had a higher fitness than the other female strategies. The outcome of this simulation is similar to empirical findings. In fish with paternal care, male filial cannibalism and female preference for mates with eggs commonly co-occur. [source] Instinctive Incest Avoidance: A Paradigm Case for Evolutionary Psychology EvaporatesJOURNAL FOR THE THEORY OF SOCIAL BEHAVIOUR, Issue 4 2006JUSTIN LEIBER Westermarck proposed that humans have an incest avoidance instinct, triggered by frequent intimate contact with family members during the first several years of life. Westermarck reasons that (1) familial incest will tend to produce less fit offspring, (2) those humans without instinctive incest avoidance would hence have tended to die off and those with the avoidance instinct would have produced more viable offspring, and hence (3) familial incest would be, as indeed it is, universally and instinctively avoided (the desire simply does arise given early continuous intimate contact; the "potty principle" as some psychologists have succinctly termed it). Victorian Westermarck claimed this as a human adaptation. Evolutionary psychologists have generalized these claims to Pleistocene humans and their ancestors, to primates, and indeed to animals generally. Yet there is surprisingly little evidence for these claims of universal instinctive avoidance. Considerable inbreeding appears among large, territorial primates and may have been so with early humans and with their ancestors. While there is little reliable non-anecdotal evidence about incestuous behavior or the lack of it among humans, what little there is does not fit well with the Westermarck thesis. [source] Introgressive hybridization of human and rodent schistosome parasites in western KenyaMOLECULAR ECOLOGY, Issue 23 2008MICHELLE L. STEINAUER Abstract Hybridization and introgression can have important consequences for the evolution, ecology and epidemiology of pathogenic organisms. We examined the dynamics of hybridization between a trematode parasite of humans, Schistosoma mansoni, and its sister species, S. rodhaini, a rodent parasite, in a natural hybrid zone in western Kenya. Using microsatellite markers, rDNA and mtDNA, we showed that hybrids between the two species occur in nature, are fertile and produce viable offspring through backcrosses with S. mansoni. Averaged across collection sites, individuals of hybrid ancestry comprised 7.2% of all schistosomes collected, which is a large proportion given that one of the parental species, S. rodhaini, comprised only 9.1% of the specimens. No F1 individuals were collected and all hybrids represented backcrosses with S. mansoni that were of the first or successive generations. The direction of introgression appears highly asymmetric, causing unidirectional gene flow from the rodent parasite, S. rodhaini, to the human parasite, S. mansoni. Hybrid occurrence was seasonal and most hybrids were collected during the month of September over a 2-year period, a time when S. rodhaini was also abundant. We also examined the sex ratios and phenotypic differences between the hybrids and parental species, including the number of infective stages produced in the snail host and the time of day the infective stages emerge. No statistical differences were found in any of these characteristics, and most of the hybrids showed an emergence pattern similar to that of S. mansoni. One individual, however, showed a bimodal emergence pattern that was characteristic of both parental species. In conclusion, these species maintain their identity despite hybridization, although introgression may cause important alterations of the biology and epidemiology of schistosomiasis in this region. [source] Genetic characterization and gonad development of artificially produced interspecific hybrids of the abalones, Haliotis discus discus Reeve, Haliotis gigantea Gmelin and Haliotis madaka HabeAQUACULTURE RESEARCH, Issue 5 2008Faruq Ahmed Abstract Hybridization among abalone species has been suggested as a possible means to increase their growth rates for aquaculture. As a first step to test the usefulness of the hybrids of Japanese abalone species (Haliotis discus discus, Haliotis gigantea and Haliotis madaka) for aquaculture, we characterized the genetic background and gonad development of hybrids that were produced by artificial insemination. The hybrid status of the resulting offspring was confirmed by assaying 14 allozymes and by RFLP analysis of the 16s rRNA and cytochrome oxidase I (COI) regions of mtDNA using 13 restriction enzymes. Histological examination of the gonads of the hybrids was conducted in comparison with those of the parental species. Cross-breeding among the three species was conducted successfully in all combinations although with lower fertilization rates (means of 1.3,60.8%) than the parental species (34.3,90%). Crosses between H. discus discus and H. madaka had higher fertilization rates (22.4,60.8%) than those involving H. gigantea (1.3,19.9%). The hybrids were ascertained by the presence of both parental genotypes at the LDH-A, ME-A, MDH-A and GPI loci. The maternal origin of the hybrid mtDNA was confirmed by digestion with DdeI, TaqI, HpaII of the COI region. No polymorphism was observed in the 16S rRNA region. The hybrids had gonadal development and maturity stages similar to the parental species up to fully mature oocytes and sperm. They spawned upon stimulation and produced viable offspring with high fertilization rates and successful development to the juvenile stage in back- and homologous hybrid crosses. [source] Reproductive isolating barriers between colour-differentiated populations of an African annual killifish, Nothobranchius korthausae (Cyprinodontiformes)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010MARTIN REICHARD Allopatric populations separated by vicariance events are expected to evolve reproductive isolating mechanisms as a result of disparate selection pressures and genetic drift. The appearance of reproductive isolating mechanisms may vary across taxa with differences in the opportunity for mate choice, and may be asymmetrical. In addition, premating barriers may be affected by individual mating experience. We used choice and no-choice experiments to investigate reproductive isolation between two allopatric (island and mainland) and colour-differentiated populations of an African annual fish, Nothobranchius korthausae. Assortative mating under experimental conditions was limited and asymmetrical. Preference for sympatric males was only expressed in nonvirgin females from one population. Virgin fish from both populations mated indiscriminately. No difference in the number of eggs laid, fertilization rate and hatching success was detected in no-choice experiments. All mating combinations produced viable offspring and no postmating barriers were detected in terms of the performance and fertility of F1 hybrids. Overall, we found little evidence for significant reproductive isolation, which is in contrast with the related killifish taxa in which assortative mating can be strong, even among allopatric populations with no colour differentiation. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 62,72. [source] | ||||||||||