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PubMed2004

Field transplants reveal summer constraints on a butterfly range expansion.

The geographic ranges of most species are expected to shift to higher elevations and latitudes in response to global warming. But species react to specific environmental changes in individualistic ways, and we are far from a detailed understanding of range-shifts. Summer temperature often limits the ranges of insects and plants, so many range-shifts are expected to track summer warming. I explore this potential range-limiting factor in a case study of a northwardly expanding American butterfly, Atalopedes campestris (Lepidoptera, Hesperiidae). This species has recently colonized the Pacific Northwest, USA, where the mean annual temperature has risen 0.8-1.8 degrees C over the past 100 years. Using field transplant experiments across the current range edge, I measured development time, survivorship, fecundity and predation rates along a naturally occurring thermal gradient of 3 degrees C. Development time was significantly slower outside the current range in eastern Washington (WA), as expected because of cooler temperatures there. Slower development would reduce the number of generations possible per year outside the current range, dramatically lowering the probability that a population could survive there. Differences in survivorship, fecundity and predation rate across the range edge were not significant. The interaction between summer and winter temperature appears to be crucial in defining the current range limit. The estimated difference in temperature required to affect the number of generations is greater than the extent of summer warming observed over the past century, however, and thus historically winter temperature alone probably limited the range in southeastern WA. Nonetheless, extraordinarily warm summers may have improved colonization success, increasing the probability of a range expansion. These results suggest that extreme climatic events may influence rates of response to long-term climate change. They also demonstrate that range-limiting factors can change over time, and that the asymmetry in seasonal warming trends will have biological consequences.

Age Factors↗
PubMed2004

Superparasitism of larval hosts by the walnut fly, Rhagoletis juglandis, and its implications for female and offspring performance.

The oviposition-preference-offspring-performance hypothesis predicts that female insects should prefer to deposit clutches on or in hosts that maximize offspring performance. An important assumption behind this prediction is that female fitness is tightly correlated with the fitness of any one offspring. In this study, we evaluate offspring performance in the walnut fly, Rhagoletis juglandis Cresson (Diptera: Tephritidae), in relation to a previously described oviposition preference for previously exploited host fruit. In particular, we examined how superparasitism of walnut hosts influences offspring survival and weight at pupation under field conditions. We found that superparasitism was common and that increases in larval densities within fruit were associated with reduced larval survival and weight at pupation. In a laboratory experiment, female size was correlated with lifetime fecundity. In this system, oviposition preference is therefore negatively, not positively, correlated with offspring performance. We argue that patterns of female preference in this system reflect direct benefits to females that are traded off against costs in terms of offspring fitness. Because female fitness is a product not only of offspring quality but also of the total number of offspring produced, female walnut flies may be optimizing their fitness by producing many less fecund offspring. Studies examining the preference-performance hypothesis should consider the reproductive conflicts between parents and offspring as potential factors that influence the congruence between parental preference and offspring performance.

Animals↗
PubMed2006

Invasion of an exotic forb impacts reproductive success and site fidelity of a migratory songbird.

Although exotic plant invasions threaten natural systems worldwide, we know little about the specific ecological impacts of invaders, including the magnitude of effects and underlying mechanisms. Exotic plants are likely to impact higher trophic levels when they overrun native plant communities, affecting habitat quality for breeding songbirds by altering food availability and/or nest predation levels. We studied chipping sparrows (Spizella passerina) breeding in savannas that were either dominated by native vegetation or invaded by spotted knapweed (Centaurea maculosa), an exotic forb that substantially reduces diversity and abundance of native herbaceous plant species. Chipping sparrows primarily nest in trees but forage on the ground, consuming seeds and arthropods. We found that predation rates did not differ between nests at knapweed and native sites. However, initiation of first nests was delayed at knapweed versus native sites, an effect frequently associated with low food availability. Our seasonal fecundity model indicated that breeding delays could translate to diminished fecundity, including dramatic declines in the incidence of double brooding. Site fidelity of breeding adults was also substantially reduced in knapweed compared to native habitats, as measured by return rates and shifts in territory locations between years. Declines in reproductive success and site fidelity were greater for yearling versus older birds, and knapweed invasion appeared to exacerbate differences between age classes. In addition, grasshoppers, which represent an important prey resource, were substantially reduced in knapweed versus native habitats. Our results strongly suggest that knapweed invasion can impact chipping sparrow populations by reducing food availability. Food chain effects may be an important mechanism by which strong plant invaders impact songbirds and other consumers.

Animal Migration↗
PubMed2006

Density-dependent regulation of population size in colonial breeders: Allee and buffer effects in the migratory Montagu's harrier.

Expanding populations offer an opportunity to uncover the processes driving spatial variation in distribution and abundance. Individual settlement decisions will be influenced by the availability and relative quality of patches, and by how these respond to changes in conspecific density. For example, conspecific presence can alter patch suitability through reductions in resource availability or territorial exclusion, leading to buffer effect patterns of disproportionate population expansion into poorer quality areas. However, conspecific presence can also enhance patch suitability through Allee effect processes, such as transmission of information about resources or improved predator detection and deterrence. Here, we explore the factors underlying the settlement pattern of a growing population of Montagu's harriers (Circus pygargus) in Spain. The population increased exponentially between 1981 and 2001, but stabilised between 2001 and 2004. This population increase occurred alongside a remarkable spatial expansion, with novel site use occurring prior to maximum densities in occupied sites being reached. However, no temporal trends in fecundity were observed and, within sites, average fecundity did not decline with increasing density. Across the population, variance in productivity did increase with population size, suggesting a complex pattern of density-dependent costs and benefits. We suggest that both Allee and buffer effects are operating in this system, with the benefits of conspecific presence counteracting density-dependent declines in resource availability or quality.

Animal Migration↗
PubMed2005

Sex allocation of a cosexual wind-pollinated tree, Quercus dentata, in terms of four currencies.

Sex allocation of a cosexual wind-pollinated species, Quercus dentata (Fagaceae), was analyzed using biomass, carbon, nitrogen and phosphorus as currencies based on data accumulated for 61 individuals from 1997-2004. Strongly female-biased sex allocation was indicated when measured in terms of biomass and carbon, but no significant bias was detected when measured in terms of nitrogen or phosphorus. From an adaptive viewpoint, there is little support for strong female-biased sex allocation, suggesting that sex allocation in terms of nitrogen or phosphorus is closer to the real picture. The relative sex allocation considerably varied from year to year, but the relative femaleness of individuals in the population was rather constant across years. No significant correlation was observed between relative sex allocation and fecundity or tree height, but individuals that showed very low fecundity tended to produce only acorns.

Carbon↗
PubMed2005

Correlation between olfactory responses, dispersal tendencies, and life-history traits of the predatory mite Neoseiulus womersleyi (Acari: Phytoseiidae) of eight local populations.

To investigate the relationship between foraging behavior and life-history traits of the predatory mite Neoseiulus womersleyi, the olfactory responses, dispersal ratios from a prey patch, predation rates, fecundity, and developmental times in eight local populations of N. womersleyi were investigated. Significant differences among local populations were found in all these traits except fecundity. None of the life-history traits correlated with foraging behavior. A significant positive correlation was found only between the olfactory response and the dispersal ratio. These results suggested that predatory mites with low olfactory responses would stay in a prey patch longer than predatory mites with high olfactory responses.

Animals↗
PubMed2006

Is the cereal rust mite, Abacarus hystrix really a generalist? - Testing colonization performance on novel hosts.

The majority of eriophyoid mites are highly host specific and restricted to a narrow range of acceptable host plant species. The cereal rust mite, Abacarus hystrix was considered to be one of a few exceptions among them and has been found to be using a relatively wide host range. Since this species is a vagrant, inhabiting short-lived plants and aerially dispersing, it has commonly been considered to be a host generalist. Here the opposite hypothesis is tested, that host populations of A. hystrix are specialized on their local host plants and may represent host races. For this purpose, females from two host populations (quack grass, Agropyron repens and ryegrass, Lolium perenne) were transferred, and subsequently reared, on their normal (grass species from which females came from) and novel (other grass species) hosts. The female's fitness was assessed by survival and fecundity on the normal and novel host. Females of both populations had no success in the colonization of the novel host. They survived significantly better and had significantly higher fecundity on their normal host than on the novel one. These findings correspond with observations on host-dependent phenotype variability and host acceptance. The presence of locally specialized host populations in A. hystrix may be evidence for high host specificity among eriophyoids and the viruses they transmit. The main conclusion is that A. hystrix, which so far has been considered as a host generalist, in fact may be a complex species consisting of highly specialized host races.

Agropyron↗
PubMed2005

Family size in white gay and heterosexual men.

There is some evidence for a genetic influence on sexual orientation. However, gay men have fewer children than heterosexual men. Increased fecundity in the biological relatives of gay men could offset this selection pressure. We measured family size in gay (n = 301) and heterosexual (n = 404) men, attending clinics for sexually transmitted infections. The main outcome measure was the number of each man's uncles and aunts, first cousins, siblings, nephews and nieces, and his own children. With the exception of the participants' own offspring, mean family size of each category of relatives was significantly larger for gay men (paternal and maternal total OR = 1.02, CI = 1.01-1.03). This remained the case after adjustment for other predictors of family size (paternal and maternal total OR = 1.02, CI = 1.00-1.03). We found increased fecundity in the relatives of gay men and this is one explanation of how a genetic influence might persist in spite of reduced reproductive fitness in the gay phenotype. There are, however, a number of alternative explanations for our finding, including unknown psychological and social factors, which might mediate the association between family size and sexual orientation.

Adult↗
PubMed2005

Water quality assessment by ecotoxicological and limnological methods in water supplies, southeast Brazil.

The quality of the water supplied to Araraquara city (São Paulo State, Brazil) was analyzed at four points: two reservoirs from which water is pumped and the water incoming and exiting a drinking-water treatment plant. Physical and chemical analyses of water were performed, as well as acute and chronic toxicity tests of the water from all four points, using Ceriodaphnia silvestrii (Cladocera, Crustacea) as test-organism. The study was carried out monthly in the period between December 2000 and November 2001. Water from the reservoirs caused neither acute nor chronic toxicity to test-organisms. On the contrary, it promoted an increase in the fecundity of cladocerans compared to control, suggesting greater availability of food. However, the water from exiting the treatment plant did cause chronic toxicity to C. silvestrii, regarding both fecundity and mortality. The toxicity was probably caused by residual chlorine, perhaps not completely removed by aeration, or by chlorine disinfection by-products (trihalomethanes) in the treated water, considering the level of organic matter present in the reservoir water.

Animals↗
PubMed2006

Effects of self-fertilization, environmental stress and exposure to xenobiotics on fitness-related traits of the freshwater snail Lymnaea stagnalis.

Genetic and ecological factors may interact in their effects on fitness. Such interactions are thus to be expected between inbreeding and exposure of a population to a toxicant. The magnitude of inbreeding depression is thought to increase in stressful environments. To test this hypothesis, we investigated the combined effects of environmental conditions and inbreeding on fitness in the self-fertile snail Lymnaea stagnalis, using a stress gradient (0-2) applied to a 100 isolated and paired lineages: laboratory control (0), outdoor microcosm control (1) and pesticide exposure under outdoor microcosm conditions (2). Outdoor stress conditions were maintained for 28 days prior to measurements of fitness traits (fecundity, hatching success, and size at hatching) under laboratory conditions, so that delayed environmental effects could be estimated. Under laboratory control conditions, we found significant initial family level heterogeneity for most measured traits, including physiological performances as assessed through energetic biomarkers. Whatever the environmental conditions, inbreeding depression was very low for progeny performances. Negative values of self-fertilization depression (SFD) were obtained. Unexpectedly, SFD showed a negative relationship with the assumed stress intensity, reflecting a higher sensitivity under pairing than under selfing, mostly due to parental fecundity. This suggests that stressful conditions may favour selfing. Stress intensity increased the distribution limits of both depression indices, suggesting that changes in fitness are less predictable in a population under stress. Implications of such findings for environmental risk assessment of pesticides are discussed.

Animals↗
PubMed2006

Restorative proctocolectomy and ileal pouch-anal anastomosis for familial adenomatous polyposis revisited.

Since restorative proctocolectomy (RPC) with ileal-pouch anal anastomosis (IPAA) removes the entire diseased mucosa, it has become firmly established as the standard operative procedure of choice for familial adenomatous polyposis (FAP). Many technical controversies still persist, such as mesenteric lengthening techniques, close rectal wall proctectomy, endoanal mucosectomy vs. double stapled anastomosis, loop ileostomy omission and a laparoscopic approach. Despite the complexity of the operation, IPAA is safe (mortality: 0.5-1%), it carries an acceptable risk of non-life-threatening complications (10-25%), and it achieves good long-term functional outcome with excellent patient satisfaction (over 95%). In contrast to the high incidence in patients operated for ulcerative colitis (UC) (15-20%), the occurrence of pouchitis after IPAA seems to be rare in FAP patients (0-11%). Even after IPAA, FAP patients are still at risk of developing adenomas (and occasional adenocarcinomas), either in the anal canal (10-31%) or in the ileal pouch itself (8-62%), thus requiring lifelong endoscopic monitoring. IPAA operation does not jeopardise pregnancy and childbirth, but it does impair female fecundity and has a low risk of impairment of erection and ejaculation in young males. The latter can almost completely be avoided by a careful "close rectal wall" proctectomy technique. Some argue that low risk patients (e.g. <5 rectal polyps) can be identified where ileorectal anastomosis (IRA) might be reasonable. We feel that the risk of rectal cancer after IRA means that IPAA should be recommended for the vast majority of FAP patients. We accept that in some very selected cases, based on clinical and genetics data (and perhaps influenced by patient choice regarding female fecundity), a stepwise surgical strategy with a primary IPA followed at a later age by a secondary proctectomy with IPAA could be proposed.

Adenomatous Polyposis Coli↗
PubMed2005

Unexpected effects of chitinases on the peach-potato aphid (Myzus persicae Sulzer) when delivered via transgenic potato plants (Solanum tuberosum Linné) and in vitro.

With the aim of producing insect-resistant potato plants, internode explants of Solanum tuberosum L. cv. Désirée were transformed with an Agrobacterium strain C58pMP90 containing an insect (Phaedon cochleariae: Coleoptera, Chrysomelidae) chitinase gene and the neomycin phosphotransferase (nptII) gene as selectable marker, both under the control of the viral CaMV 35S promoter. Three transformed potato lines (CH3, CH5 and CH25) exhibiting the highest chitinolytic activities were selected for feeding experiments with the peach-potato aphid, Myzus persicae (Sulzer), under controlled photoperiod and temperature conditions. Aphids fed on transgenic potato plants showed a reduced pre-reproductive period and an enhanced daily fecundity. Transgenic potato lines did not affect nymphal mortality, but improved several biological parameters related to aphid population's growth. Artificial diets were used to provide active (1, 10, 100 and 500 microg ml(-1)) and inactive (500 microg ml(-1)) bacterial (Serratia marcescens) chitinase to M. persicae. These compounds increased nymph survival at all active chitinase doses when compared to the control diet, while inactive chitinase did not. Although the pre-reproductive period was slightly shortened and the daily fecundity slightly higher, active and inactive chitinase provided as food led a reduction from 1 to 1.5 day population's doubling time. Therefore chitinase activity was responsible for the probiotic effects on aphids. Our results question the relevance of a chitinase-based strategy in the context of potato culture protection.

Animals↗
PubMed1982

Effects of prenatal exposure of mice to "low-dose" diethylstilbestrol and the development of adenomyosis associated with evidence of hyperprolactinemia.

The developing genital tract of the fetal mouse was exposed to diethylstilbestrol (DES) and the induction of noncyclic ovarian function in adult life was circumvented. Female mice of two inbred strains, BALB/c and C3H, were mated with BALB/c male mice and on the seventh day of pregnancy were fed a diet containing 0.2 micrograms of DES/gm continuously until the morning after delivery of the young. This regimen did not interfere appreciably with continuance of pregnancy, and offspring of normal body weight were delivered. When the mice reached maturity, the fertility and fecundity of the cycling exposed female mice were, however, reduced significantly. Virgin exposed BALB/c female mice, observed until 18 months of age, developed neoplasms with the same low frequency normally encountered in this strain, while the exposed hybrids developed mammary carcinomas almost twice as often as did an unexposed population. In addition, two benign lesions of the genital tract occurred frequently in the exposed hybrid female mice. The most extensive of these resembled adenomyosis as seen in the female human in that foci of nonneoplastic endometrium penetrated the muscular layers of the uterus, often forming small, fluid-filled blebs evaginating the serosal surface. This lesion was reproduced by grafting day-old female mice with a single ectopic hypophysis, indicating that chronic hyperprolactinemia was a major endocrine factor in its genesis. The second was an enlargement of the cervix with extensive mucoid alterations within the muscularis, a lesion that could be produced by the continuous estrogenization of adult animals. Both lesions occurred to a much lesser extent in BALB/c female mice, and neither was felt to contribute to the reduced fecundity noted in DES-exposed female mice.

Animals↗
PubMed1986

Factors affecting pregnancy rates in a donor insemination program using frozen semen.

The results of therapy of 226 women receiving frozen and fresh donor semen are reported. Overall, 45.6% of patients conceived with a monthly fecundability of 0.102. The effect of a variety of factors on fertility rates was analyzed in life-table analysis of 1000 cycles. Optimal pregnancy rates were obtained in couples with azoospermia (0.17) or no female infertility factors (0.2). Patients with ovulatory dysfunction treated with clomiphene also had optimal pregnancy rates (0.17 per cycle). Endometriosis reduced fecundability significantly (0.04 per cycle). There was no significant difference in pregnancy rates per cycle between fresh (0.12) and frozen (0.09) semen. Acceptable pregnancy rates were obtained with frozen semen therapy and in patients with treated ovulatory dysfunction.

Clomiphene↗
PubMed1989

Luteinizing hormone and ovulation timing in a therapeutic donor insemination program using frozen semen.

A series of 110 therapeutic donor insemination cycles was analyzed to determine the impact on fecundity when a urinary luteinizing hormone detection kit was used to plan inseminations. To prevent the transmission of human immunodeficiency virus, frozen semen, thawed after a 90-day quarantine, was used. The minimum standard for insemination with cryopreserved semen was a total of 24 x 10(6) motile sperm per milliliter after thawing. Fecundity was 0.12 when insemination timing was based on cervical mucus evaluation and basal body temperature charts and 0.13 when a urinary luteinizing hormone kit was also used to predict ovulation. Life table analysis with the log rank test showed no statistically significant difference in the number of cycles required to achieve conception between the group of patients using conventional methods of ovulation timing and the group of patients using the urinary luteinizing hormone kit. Urinary luteinizing hormone testing offers no advantage over conventional methods, such as cervical mucus examination and evaluation of basal body temperature, when ovulation is being timed for insemination with frozen donor semen.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Pregnancy rates with fresh versus computer-controlled cryopreserved semen for artificial insemination by donor in a private practice setting.

From late 1970 through December 1987, 580 women began 733 treatment programs (a total of 3405 insemination cycles) with fresh semen for artificial insemination by donor. The unadjusted pregnancy rate was 48.5% and the cumulative pregnancy rate after seven cycles by life-table analysis was 59.6% with a monthly fecundability of 11.9%. From 1988 to the present, 113 women have begun 115 treatment programs (a total of 371 insemination cycles) with cryopreserved semen for artificial insemination by donor. The unadjusted pregnancy rate to date is 18.3% and the cumulative pregnancy rate after seven cycles by life-table analysis is 48.6% with a monthly fecundability of 5.9%. This report shows that using cryopreserved semen for artificial insemination by donor will take somewhat longer to produce a pregnancy but the ultimate pregnancy rate will be similar to that with fresh semen for artificial insemination by donor.

Adult↗
PubMed1983

Trichinella spiralis: role of non-H-2 genes in resistance to primary infection in mice.

Two strains of mice which share identical H-2 genes but differ in their genetic backgrounds were compared for their ability to resist infection with Trichinella spiralis. The two strains of mice, C3HeB/FeJ and AKR/J, share the H-2k haplotype which is associated with susceptibility to primary infection with T. spiralis in H-2 congenic strains of mice. AKR/J mice, infected with 150 infective muscle larvae, harbored significantly fewer muscle larvae 30 days postinfection than did mice of the strain C3HeB/FeJ. Approximately equal numbers of worms establish in the small intestine of AKR and C3H mice, but the AKR mice expelled adult worms from the gut more rapidly than did mice of the C3H strain. By Day 9 postinfection, 50% of the worms had been expelled by the AKR mice whereas expulsion of worms from C3H mice was delayed beyond Day 9 and occurred primarily between Days 10 and 12. Over this same experimental period (Days 6-12), fecundity of female worms from AKR mice, measured as the mean newborn larvae/female/hour, was approximately one-half that of worms taken from C3H mice. These results support the conclusion that genes outside of the mouse H-2 complex regulate expulsion of adult worms from the gut. These background genes also markedly influence the fecundity of female worms.

Animals↗
PubMed1990

The role of helminths in the biological control of mammals.

Biological control of invertebrates has been successful while that of vertebrates has been, with the exception of myxomatosis in rabbits, unsuccessful; reasons for this are discussed. Demographic studies of small mammals suggest that population regulation occurs by several different mechanisms, more than one of which may be acting at the same time. Coevolution is an important phenomenon in host-parasite associations, nevertheless parasites may limit host population abundance. The basis of the regulatory effect on the host population is that parasite-induced host mortality or reduction in fecundity is density-dependent. Increasing evidence of the density-dependent effects of helminths on host survival and reproduction is forthcoming from laboratory studies but has not been confirmed in the field. The theory that a helminth parasite may regulate mammal population abundance has been verified recently in the laboratory. A multidisciplinary research programme aimed at understanding the mechanisms responsible for formation of house mouse (Mus domesticus) plagues and seeking strategies to reduce mouse numbers is discussed. One aspect of the work involves investigation of the potential of the nematode, Capillaria hepatica, as a biological agent in the control of wild mice in the cereal-growing regions of Australia. Biological control of mammals is viewed within the context of integrated pest management. A helminth species which reduces host survival or fecundity at an increasing rate as host abundance increases has a role in host population regulation. There is potential to capitalize on that role and apply the helminth as a biological agent in the control of mammals which have attained pest status.

Animals↗