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At least 595 records · Page 33Linked to original sources
PubMed1998

Local mate competition, variable fecundity and information use in a parasitoid.

Experiments with sex allocation in parasitic wasps offer excellent opportunities for testing how the way in which organisms process information about their environment influences behaviour. If mating takes place in temporary patches, where only a small number of females produce offspring, then sex allocation theory predicts a female-biased sex ratio. When females lay different numbers of offspring in a patch, females that produce relatively fewer offspring should lay a less female-biased, or even male-biased, sex ratio. Recent theoretical models have predicted that the exact form of this relationship depends upon whether females know only their own clutch size (self knowledge) or also the clutch sizes laid by the other females on the patch (complete knowledge). We tested the predictions of these models by examining sex allocation when two females of the parasitoid wasp Nasonia vitripennis oviposited simultaneously on a patch. The offspring sex ratio (proportion of males) produced by a female was: (1) negatively correlated with the number of offspring that she laid; and (2) positively correlated with the body size of the other female on the patch. Larger females matured more eggs and laid more offspring in the experimental patch. This suggests that, as predicted by the complete knowledge model, the offspring sex ratio laid by a female became more female biased as she laid a greater proportion of the total offspring laid on the patch. Furthermore, females use the body size of other females to assess the clutch sizes that these will lay. Copyright 1998 The Association for the Study of Animal Behaviour

Journal Article↗
PubMed1994

The Booroola fecundity (FecB) gene maps to sheep chromosome 6.

The Booroola (FecB) mutation in sheep is linked to markers from a region of syntenic homology to human chromosome HSA4q, but the chromosomal location in sheep has not been determined. Analysis of linkage in Booroola half-sib pedigrees and 17 full-sib families identified genetic linkage between platelet-derived growth factor receptor-alpha (PDGFRA) and alpha s1-casein (CSN1S1) at 12 cM (Zmax = 9.14) and between PDGFRA and the microsatellite markers BM143 and OarHH55 (Zmax = 6.28 and 3.83, respectively). The microsatellite markers OarAE101 and BM143 and genes from the linkage group (PDGFRA, SPP1, and EGF) were mapped in a partial sheep x hamster somatic cell hybrid panel. All markers identified bands specific to somatic cell hybrids containing the sheep chromosome t1 (rob6;24) or t1q (chromosome 6). In sheep the casein genes alpha s1 (CSN1S1), alpha s2 (CSN1S2), beta (CSN2), and kappa (CSN3) are tightly linked, and CSN2 has been mapped to sheep chromosome 6q23-q31. We conclude that the Booroola mutation is located within a conserved syntenic group that maps to sheep chromosome 6.

Animals↗
PubMed1994

Genetic markers for the Booroola fecundity (Fec) gene in sheep.

Animals from the Booroola line of Australian Merino sheep are characterized by a high ovulation rate that can be attributed to the presence of a codominant allele (FecB). The specific function of the gene has not been identified. Effective use of the trait within the sheep breeding industry requires one or more genetic markers that can distinguish between alternative alleles at the locus Fec. With a combination of DNA minisatellite markers and polymorphic protein markers, a cluster of seven minisatellite fragments has been identified as being linked to the Fec gene and to the ovine A blood group locus. The minisatellite fragments have been derived from multilocus probes and hence cannot be used to define the chromosomal location of the Fec gene or to serve as diagnostic markers for Fec. The derivation of cloned single locus markers from the minisatellite fragments will enable finer scale mapping of the Fec and the A blood group locus in sheep.

Animals↗
PubMed1987

Residual influences on fecundity in drosophilid species.

A residual influence of males and females on oviposition has been examined in 7 drosophilids. There was evidence for oviposition deterrence in Drosophila funebris, with males as well as females producing the inhibitory effect. In contrast, male residues stimulated oviposition in Zaprionus tuberculatus. Male residues also stimulated oviposition and appeared to serve as an aggregation cue in D. melanogaster.

Animals↗
PubMed1985

Fecundity and longevity of houseflies after space flight.

After 7 days of space flight house flies, Musca domestica, exhibited similar longevity, but a reduction in reproductive output as compared to earthbound controls. This reduction was not observed in later generations. These data suggest that space flight directly alters the rate of ovarian development, but that this effect is not genetically transmitted.

Animals↗
PubMed1988

Fecundity in fat-tailed sheep at two different altitudes in East Java.

Ovulation rates, embryonic mortality and litter sizes at birth were studied in East Java fat-tailed sheep at two different altitudes: Pujon, 1,300 m above sea level and Malang, 500 m above sea level, over a period of one year. In both areas the number of ewes lambing each month was approximately the same. The average litter size at birth in Pujon and Malang was 2.37 and 1.60, respectively. Litters of three or more were almost exclusively found in November, December, January and February and in Pujon only. The relatively low ambient temperatures in Pujon in the period June to October may have influenced ovulation and embryonic survival rates positively. Abattoir data showed that ovulation rates of ewes with three or more foetuses alive 45 to 60 days after mating were much higher than in ewes with one or two foetuses alive. Embryonic mortality was very high in ewes with one live foetus.

Altitude↗
PubMed2004

Is there a trade-off between fecundity and egg volume in the parasitic copepod Lernanthropus cynoscicola?

Negative relationships between egg number and egg size are commonly seen in many animal taxa, supporting the idea that there is a trade-off between egg number and egg size resulting from the allocation of resources to either one or the other. In parasites, where availability of resources is presumably very high, there may be fewer energetic constraints acting on allocation strategies, and the trade-off may be weakened. We investigated the association between egg number and egg volume among females of the copepod Lernanthropus cynoscicola Timi and Etchegoin, 1996, parasitic on the fish Cynoscion guatucupa (Cuvier). Both egg number and egg volume were strongly correlated with female body size. After controlling for the effects of body size, we found absolutely no evidence of a trade-off, i.e. no negative relationship, between egg number and egg volume. For a given body length, females that produce many eggs do not tend to produce relatively small eggs, and vice versa. In contrast, under conditions in which resources are plentiful, large females produce large quantities of high-quality eggs, and have a marked fitness advantage over small females.

Animals↗
PubMed2004

The invasive shrub, Lonicera maackii, reduces growth and fecundity of perennial forest herbs.

Effects of invasive plant species on native plant species are frequently assumed or inferred from comparisons, but rarely quantified experimentally. Such quantification is important to assessing risks and impacts of invasives. We quantified the effects of Lonicera maackii, an exotic shrub invasive in many eastern North American forests, on survival, growth, and reproduction of three perennial herbs: Allium burdickii, Thalictrum thalictroides , and Viola pubescens. We predicted that the spring ephemeral, A. burdickii , would be most impacted, due to early leaf expansion of L. maackii. Field experiments were carried out in two deciduous forest stands, one (Gregg's Woodlot, GW) disturbed and the other (Western Woods, WW) relatively undisturbed. In each stand, individual herbs were transplanted into a blocked design of 60 plots where L. maackii was present, absent, or removed, and monitored for 5 growing seasons. Lonicera maackii did not affect survival of transplants, but reduced growth and final size of individuals of all three species. For two of the species, A. burdickii and V. pubescens, L. maackii reduced the proportion of live plants flowering in both stands, and reduced the seed or fruit number per flowering individual in GW. For T. thalictroides the proportion flowering was not affected, but seed number per flowering plant was reduced by L. maackii in both stands. For all three species, cumulative seed production over the course of the study was reduced by L. maackii. Overall, effects on the spring ephemeral, A. burdickii, were similar to effects on the other herbs. Because mortality of these established individuals was not affected, short-term studies might conclude forest herbs are unaffected by invasive shrubs. However, the growth and reproduction impacts documented here suggest that populations are impacted in the long-term.

Allium↗
PubMed2005

Fecundity limits in Frangula alnus (Rhamnaceae) relict populations at the species' southern range margin.

The geographic range of many temperate plant species is constrained by climate, but it remains little known how climate affects population performance at low-latitude range margins. This study investigated the reproduction of the Eurasian tree Frangula alnus in relict populations near its southwestern range limit in southern Spain. The aim was to identify the principal stages and causes of ovule loss experienced by these marginal populations. More than 6,800 flowers were monitored over 2 years, insect observations and different experiments were carried out to assess levels of pollen and resource limitation, as well as the influence of flowering phenology on seed production. Most ovule losses occurred during flower anthesis and were due to strong cross-pollen limitation. Fruit set was affected by tree size, light regime and flowering phenology, probably through their effects on pollinator behaviour. Fruit set was almost zero throughout the first half of the flowering season. Then it increased paralleling changes in pollinator abundance but was soon overridden by increasing ovule desiccation due to summer drought. Successful seed production was mostly confined to a brief period near the end of the flowering season. Adverse weather during this period in the second study year resulted in a threefold bud and flower mortality and a 50% decrease of fruit production. Spring rainfalls in southwestern Spain have diminished more than 30% through past decades leading to an earlier onset of summer drought. This trend and its adverse effects on seed production may contribute to explaining the recent decline of F. alnus at its southwestern range limit.

Analysis of Variance↗