Reproductive Fitness of Descendants of Mice Exposed to Spermatogonial Irradiation

1968 ◽  
Vol 35 (2) ◽  
pp. 263 ◽  
Author(s):  
Earl L. Green
Keyword(s):  
Author(s):  
Richard Frankham ◽  
Jonathan D. Ballou ◽  
Katherine Ralls ◽  
Mark D. B. Eldridge ◽  
Michele R. Dudash ◽  
...  

The harmful impacts of inbreeding are generally greater in species that naturally outbreed compared to those in inbreeding species, greater in stressful than benign environments, greater for fitness than peripheral traits, and greater for total fitness compared to its individual components. Inbreeding reduces survival and reproduction (i.e., it causes inbreeding depression), and thereby increases the risk of extinction. Inbreeding depression is due to increased homozygosity for harmful alleles and at loci exhibiting heterozygote advantage. Natural selection may remove (purge) the alleles that cause inbreeding depression, especially following inbreeding or population bottlenecks, but it has limited effects in small populations and usually does not completely eliminate inbreeding depression. Inbreeding depression is nearly universal in sexually reproducing organisms that are diploid or have higher ploidies.


1978 ◽  
Vol 27 ◽  
pp. 51-56 ◽  
Author(s):  
Fiorella Shabtai ◽  
Shlomo Bichacho ◽  
Isaac Halbrecht

The negative influence of some insecticides on male fertility has been noted. We report our cytogenetic observations on a group of infertile insecticide workers. Increased chromosomal breakage was a constant finding and the Y chromosome was especially damaged. This may account for impaired spermatogenesis. Furthermore, the involvement of heterochromatic chromosomal variants both in the individual susceptibility to the chemically induced damage and in the reproductive fitness is emphasized.


1996 ◽  
Vol 45 (2) ◽  
pp. 1-9 ◽  
Author(s):  
M. L. HAHN ◽  
J.‐L. SARAH ◽  
M. BOISSEAU ◽  
N. J. VINES ◽  
D. J. WRIGHT ◽  
...  
Keyword(s):  

2015 ◽  
Vol 282 (1815) ◽  
pp. 20151421 ◽  
Author(s):  
Göran Arnqvist ◽  
Ahmed Sayadi ◽  
Elina Immonen ◽  
Cosima Hotzy ◽  
Daniel Rankin ◽  
...  

The ultimate cause of genome size (GS) evolution in eukaryotes remains a major and unresolved puzzle in evolutionary biology. Large-scale comparative studies have failed to find consistent correlations between GS and organismal properties, resulting in the ‘ C -value paradox’. Current hypotheses for the evolution of GS are based either on the balance between mutational events and drift or on natural selection acting upon standing genetic variation in GS. It is, however, currently very difficult to evaluate the role of selection because within-species studies that relate variation in life-history traits to variation in GS are very rare. Here, we report phylogenetic comparative analyses of GS evolution in seed beetles at two distinct taxonomic scales, which combines replicated estimation of GS with experimental assays of life-history traits and reproductive fitness. GS showed rapid and bidirectional evolution across species, but did not show correlated evolution with any of several indices of the relative importance of genetic drift. Within a single species, GS varied by 4–5% across populations and showed positive correlated evolution with independent estimates of male and female reproductive fitness. Collectively, the phylogenetic pattern of GS diversification across and within species in conjunction with the pattern of correlated evolution between GS and fitness provide novel support for the tenet that natural selection plays a key role in shaping GS evolution.


2021 ◽  
Vol 118 (45) ◽  
pp. e2109381118
Author(s):  
Marcela Nouzova ◽  
Marten J. Edwards ◽  
Veronika Michalkova ◽  
Cesar E. Ramirez ◽  
Marnie Ruiz ◽  
...  

Methyl farnesoate (MF) plays hormonal regulatory roles in crustaceans. An epoxidated form of MF, known as juvenile hormone (JH), controls metamorphosis and stimulates reproduction in insects. To address the evolutionary significance of MF epoxidation, we generated mosquitoes completely lacking either of the two enzymes that catalyze the last steps of MF/JH biosynthesis and epoxidation, respectively: the JH acid methyltransferase (JHAMT) and the P450 epoxidase CYP15 (EPOX). jhamt−/− larvae lacking both MF and JH died at the onset of metamorphosis. Strikingly, epox−/− mutants, which synthesized MF but no JH, completed the entire life cycle. While epox−/− adults were fertile, the reproductive performance of both sexes was dramatically reduced. Our results suggest that although MF can substitute for the absence of JH in mosquitoes, it is with a significant fitness cost. We propose that MF can fulfill most roles of JH, but its epoxidation to JH was a key innovation providing insects with a reproductive advantage.


2003 ◽  
Vol 81 (2) ◽  
pp. 152-163 ◽  
Author(s):  
Humberto Fabio Causin ◽  
Renata D Wulff

Morphological shade-avoidance responses have been hypothesized to be a form of adaptive plasticity to improve competition for light; however, little is known about their intraspecific variability and their effect on reproductive fitness. To compare plant responses either at a common age or at a common phenological stage, two experiments were conducted with early- and late-flowering Chenopodium album plants exposed to different red (660 nm) to far red (730 nm) ratios. In the first experiment, plant height and number of leaves were recorded at several times during the vegetative stage, and at the onset of flowering, each plant was harvested and other growth traits were measured. In the second experiment, three destructive harvests were performed across the whole plant cycle. Plant growth and development markedly differed between early- and late-flowering plants in all of the conditions tested. Light treatments significantly affected stem length, total leaf number, total leaf area, and relative allocation to leaf biomass. In all families, the response of stem elongation to light treatments decreased later in the development, while changes in the other plastic responses were mostly due to variations in plant growth. No significant treatment effect was found on relative biomass allocation to reproductive structures. However, individual seed mass significantly differed between certain groups, indicating that light quality can affect reproductive fitness through changes in traits other than fruit or seed set.Key words: Chenopodium album, fitness, intraspecific variability, phenotypic plasticity, red to far red ratio, shade-avoidance responses.


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