Evolutionary transition to complex population dynamic patterns in a two-age population

An evolutionary model of density-dependent selection in a two-age population is considered. The model is studied analytically and numerically; the parametric regions of its various dynamic behaviors are determined. An example is used to analyze how an evolutionary increase in the mean fitness results in a more complex population dynamics in a structured population.     

Temporal patterns of breeding and larval settlement in a temperate population of the tropical anemonefish,Amphiprion clarkii

The breeding of the anemonefish,Amphiprion clarkii, and the settlement of larvae were observed in temperate Japan. Spawning had two peaks near the first and the third quarter of the moon in 1983, but did not in 1984. The clutch size varied greatly during the breeding season, with a peak from the second half of June to the second half of July. Adult fishes inhibited larval settlement. The proportion of disappeared 0-year olds to the total was higher in 1984 than in 1983. This difference might be mainly due to the difference in the degree of crowding in each sea anemone. The period of larval settlement closely paralleled the breeding season. The larvae settled abundantly around the first quarter and the third quarter of the moon in 1983, and did from the third quarter to the first quarter in 1984. In both years, the number of settled larvae was more from the full moon to the new moon than the new moon to the full moon. The daily pattern of larval settlement did not reflect that of breeding.     

Temporal patterns of geographic parthenogenesis in a freshwater snail

Geographic parthenogenesis describes the observation that parthenogenetic organisms tend to occupy environments different from those of their close, sexually reproducing relatives. These environments are often described as extreme or disturbed habitats. We examined whether patterns of geographical parthenogenesis persist over time, by conducting a 3-year life-history survey and comparing two very proximate habitats of the freshwater snail Melanoides tuberculata : Nahal Arugot, a desert stream naturally disturbed by flash floods, and Or Ilan, a stable freshwater pond. Both sites occur in a xeric environment and are subject to otherwise similar biotic (e.g. parasites, predators) and climatic conditions. In the stable habitat, male frequencies and snail densities were significantly higher than in the disturbed one, whereas infection levels, mean embryo counts, and water temperatures were similar at both sites. Additionally, male frequencies declined after density decreased, thereby providing evidence for geographical parthenogenesis via reproductive assurance. Infection prevalence was very low regardless of reproduction mode. Although further genetic work is required, the apparent metapopulation structure of M. tuberculata in the Judean desert may be suitable for evaluating other possible explanations of geographical parthenogenesis.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 711–718.     

Identification and correlates of weight loss in adolescents in a national sample

Objective: Little is known about behaviors associated with successful weight loss during adolescence. The first objective of the current study was to identify meaningful weight loss, weight maintenance, and weight gain in male and female adolescents. The second objective of this study was to apply these methods to U.S. adolescents from the National Health and Nutrition Survey 1999 to 2002 data and to identify factors associated with these weight change outcomes. Research Methods and Procedures: The current analyses include 1726 (female, 836; male, 890) 16‐ to 18‐year‐old adolescents who completed the questionnaire components and interview for either the 1999–2000 or the 2001–2002 National Health and Nutrition Survey study. Dietary intake, physical activity, and dieting attitudes were compared across the weight loss (L), maintain (M), and gain (G) groups in the entire sample and in a subset of adolescents who are overweight and at‐risk‐for‐overweight (≥85th percentile). Results: The tested method for identifying weight L, M, and G groups has both theoretical and statistical validity and, when applied to the sample, showed the expected direction of changes in weight. Results suggest that more overall physical activity, more vigorous exercise, and less sedentary activity are associated with being in the L group in both the full sample and the overweight and at‐risk‐for‐overweight sample. In addition, fewer teens in the L groups endorsed efforts at trying to lose weight, compared with the M and G groups. Discussion: This study provides a method to determine successful adolescent weight loss for researchers and provides useful concrete information about successful weight loss for clinicians and others who work with adolescents.     

Leptin in a lean population of Filipino adolescents

To clarify the role of leptin as a signal of energy status in humans, this study investigated the relationship of leptin to measures of body composition, maturity, and lifestyle factors in a lean sample of 293 male and 303 female Filipino adolescents (age 14-16 years). Participants were selected from the Cebu Longitudinal Health and Nutrition Survey, a representative birth cohort study begun in 1983. Using IOTF criteria, the prevalence of overweight (2.2%) and obesity (0.3%) were extremely low, and leptin levels were among the lowest reported in any healthy population (mean: 0.78 and 3.57 ng/dl in males and females). As expected, adiposity was the strongest predictor of leptin, with triceps skinfold explaining 40.2 and 30.6% of leptin variance in males and females. In females, subscapular skinfold was a significant predictor of leptin independent of triceps, while no anthropometric measure predicted leptin independent of triceps in males. There were few relationships between lifestyle factors and leptin independent of adiposity. In males, leptin levels varied little across most of the triceps distribution, suggesting that the leptin-adipose regulatory system is sensitive to very small changes in leptin in lean populations, at least among males. These findings add to the small but growing list of studies documenting differences in leptin biology among chronically lean populations.     

Disease-modifying drug initiation patterns in commercially insured multiple sclerosis patients: a retrospective cohort study

Background  

The goal of this research was to compare the demographics, clinical characteristics and treatment patterns for newly diagnosed multiple sclerosis (MS) patients in a commercial managed care population who received disease-modifying drug (DMD) therapy versus those not receiving DMD therapy.     

Gene flow in a national cross-breeding beef population

Future progress in genetic improvement and the monitoring of genetic resources in beef cattle requires a detailed understanding of the population under selection. This study examines the gene flow in the UK beef population with an uncommon breeding structure involving interaction between the beef and dairy populations. British Cattle Movement Service records were used as the primary source of information, and these data were triangulated with UK government statistics, other industry information sources and existing literature to build up a profile of the UK beef industry. Estimates were made of the breed composition of suckler cows, breeding bulls and the prime slaughter population. Cross-bred animals made up 85% and 94%, respectively, of the commercial beef breeding cow and prime slaughter populations. Holstein/Friesian (through cross-breeding) made up the largest proportion of genes in both these populations with 33% and 28%, respectively. The next five most popular breeds were specialist beef breeds: Limousin (22% and 18%), Charolais (11% and 6%), Simmental (9% and 11%), Angus (7% and 8%) and Belgian Blue (6% and 6%). Combined, the top seven beef breeds accounted for 94% of beef genetics in the prime slaughter population, and 80% of this came from non-native breeds. The influence of dairy breeds in the commercial beef breeding population was highlighted by the fact that 44% of replacement commercial beef breeding females were sourced from beef-sired crosses in the dairy herd, and in total 74% of all maternal grand dams of prime slaughter animals were Holstein/Friesian. The use of selection index technology was also investigated by analysing breeding bull sale results, with the correlation between the terminal sire index and sale price of young breeding bulls being generally moderate but significant, ranging from 0.21 to 0.38 across the major beef breeds. The most influential source of genetics in the commercial suckler beef herd was natural service breeding bulls. These were mostly sourced from pedigree breeders, and accounted for 47.8% of the genetics in the prime beef population. Artificial insemination sires were responsible for 16.6% of prime beef genetics, with the remaining 35.6% coming from dairy breeds, 95% of which was Holstein/Friesian.     

Temporal increase in mtDNA diversity in a declining population

In small and declining populations levels of genetic variability are expected to be reduced due to effects of inbreeding and random genetic drift. As a result, both individual fitness and populations’ adaptability can be compromised, and the probability of extinction increased. Therefore, maintenance of genetic variability is a crucial goal in conservation biology. Here we show that although the level of genetic variability in mtDNA of the endangered Fennoscandian lesser white‐fronted goose Anser erythropus population is currently lower than in the neigbouring populations, it has increased six‐fold during the past 140 years despite the precipitously declining population. The explanation for increased genetic diversity in Fennoscandia appears to be recent spontaneous increase in male immigration rate equalling 0.56 per generation. This inference is supported by data on nuclear microsatellite markers, the latter of which show that the current and the historical Fennoscandian populations are significantly differentiated (F_ST = 0.046, P = 0) due to changes in allele frequencies. The effect of male‐mediated gene flow is potentially dichotomous. On the one hand it may rescue the Fennoscandian lesser white‐fronted goose from loss of genetic variability, but on the other hand, it eradicates the original genetic characteristics of this population.     

Headaches in overweight children and adolescents referred to a tertiary-care center in Israel

Objective: To assess the association between obesity and primary headaches in children and adolescents. Methods and Procedures: In a prospective study, the short‐questionnaire version based on existing International Headache Society diagnostic criteria was administered. Two hundred and seventy‐three children and adolescents (61% females) aged 9–17 years were assessed. One hundred and sixteen (42.5%) subjects were of normal weight, 45 (16.5%) were at risk for overweight (BMI >85th and <95th percentile for age and gender) and 112 (41%) were overweight (BMI ≥95th percentile). The outcome measures were prevalence of headaches, type of headaches, association between headaches and elevated blood pressure in overweight subjects. Results: Headache was reported in 39 (14.3%) subjects, with a similar rate in females (14.5%) and males (14%). Among 39 subjects with headaches, 20 (17.9%) were overweight, 7 (15.6%) were at risk for overweight and 12 (10.3%) were normal‐weight children. Among females, 7.7% of normal‐weight group suffered from headaches, compared with 14.8% of the at risk for overweight group and 20.3% of the overweight group (P for trend 0.04). Among males, the occurrence of headaches was similar in all three weight groups (P = 0.96). The occurrence of headaches increased from 10.6% among children aged 9–11 years to 21.8% in the 15–18 years age group (P < 0.05). In multivariate analysis, a significant independent risk for headaches was present in overweight females (odds ratio (OR) = 3.93, 95% confidence interval (CI) 1.28–12.1) and in adolescents aged 15–18 years (OR = 2.62, 95% CI 1.07–6.45). Elevated blood pressure was not independently associated with headaches. Of the 15 children with migraine, 12 were either at risk for overweight or overweight. Discussion: Overweight females had an almost fourfold excess risk of headaches when compared with normal‐weight girls.     

Temporal patterns of bird mortality due to road traffic collisions in a Mediterranean region

ABSTRACT

Capsule: There was significant variation on the incidence of road traffic mortality across bird species, due to seasonal and weather effects but also due to differences between years.

Aims: To assess patterns of mortality due to traffic collision for six common bird species over a period of nine years in relation to seasonality and weather.

Methods: Road mortality surveys were performed on four road sections from 2005 to 2013 in southern Portugal. The analysis controlled for survey frequency, and carcass persistence and detectability.

Results: Overall, bird mortality decreased over time and was generally higher during spring and summer months. The lack of strong relationships between the weather variables and the observed mortality patterns suggests the existence of additional factors important in explaining the observed trends.

Conclusions: Our study provides evidence that bird mortality due to collision with vehicles may change between years and was highest during the breeding season. This could have population consequences, and highlights the need to further address large temporal scales in roadkill research.     

Temporal analysis of clonal structure in a moss bdelloid population

Clonal structure of a population of Macrotrachela quadricornifera (Rotifera, Bdelloidea) from a terrestrial moss in Northern Italy, was investigated over a 16 month period. Every month, 40–60 specimens of M. quadricornifera were collected from about 0.1 m² of moss. The individual animals were homogenized and their isozyme phenotypes analyzed by electrophoresis on vertical polyacrylamide gel. One enzyme, phosphoglucose isomerase (PGI), was used as a marker to distinguish the different clones present in the sample. A few clones were established from the rotifers sampled and patterns of esterases and , and malic enzyme were studied. Nine electrophoretic patterns for PGI were seen. One was dominant, a second was almost always present, but in lesser amounts. The remainder were present occasionally.There seemed to be no seasonal replacement of the clones and the composition of the population appeared to be unaffected by variations in temperature. Relative humidity seemed to be the more important factor in regulating the number of electromorphs of the rotifer population.     

Temporal patterns in immune responses to a range of microbial insults (Tenebrio molitor)

Much work has elucidated the pathways and mechanisms involved in the production of insect immune effector systems. However, the temporal nature of these responses with respect to different immune insults is less well understood. This study investigated the magnitude and temporal variation in phenoloxidase and antimicrobial activity in the mealworm beetle Tenebrio molitor in response to a number of different synthetic and real immune elicitors. We found that antimicrobial activity in haemolymph increased rapidly during the first 48h after a challenge and was maintained at high levels for at least 14 days. There was no difference in the magnitude of responses to live or dead Escherichia coli or Bacillus subtilis. While peptidoglylcan also elicited a long-lasting antimicrobial response, the response to LPS was short lived. There was no long-lasting upregulation of phenoloxidase activity, suggesting that this immune effector system is not involved in the management of microbial infections over a long time scale.     

Temporal patterns in a fish assemblage of a semiarid mangrove zone in Madagascar

Gillnet sampling was conducted for a year in a tropical mangrove creek (SW Madagascar), characterized by a limited freshwater influence, a high turbidity and a tidal range up to 3 m. Sixty species of juvenile fishes were caught, 44 species being of commercial interest. Catches were dominated by Gerreidae (27% of total abundance), Teraponidae (16%), Carangidae (13%) and Sparidae (12%). The temporary resident fishes in the mangrove zone represented 50% of the species and 97% of the total abundance, the other species being rare (less than five individuals). The species richness, abundance and biomass per netting were low in the middle of the cool season (July-August). Monthly changes in the fish assemblage were particularly complex, with three species groups displaying a clear seasonal pattern, some species succeeding one another in a rather unstructured way, and three species abundant throughout the year. There was no clear structuring effect of temperature, salinity and turbidity on the fish assemblage. However, tidal, lunar and diel effects on the composition of the fish assemblage were evident. The species overlap between the Sarodrano mangrove fauna and the adjacent coral reef fauna is particularly weak with six species in common and shows that the mangrove plays only a very limited nursery role for coral reef species.     

Temporal patterns of seed use and availability in a guild of desert ants

ABSTRACT.

• 1 Temporal patterns of seed use were studied from late winter to autumn in three species of seed-harvesting ants in the Sonoran Desert. Measures of effective foraging activity, dietary niche breadth and dietary niche overlaps were obtained each month and were tested for correlation with estimates of the available seed resource.
• 2 Seeds were the only numerically important type of food in the diets of all species.
• 3 The ants partitioned the resource according to both seed species and seed size, although there was considerable overlap.
• 4 Pheidole xerophila had the smallest forager body size and is a specialist on small seeds because it harvested them in greater proportion than their rank in the soils and expanded its diet to larger seeds only when the abundance of small seeds declined.
• 5 When the abundance of the small seeds of Bouteloua barbata decreased, the middle-sized ant, Veromessor pergandei, showed a decrease in foraging activity, increase in niche breadth, and a decrease in overlap with P.xerophila.
• 6 Seed size preferences of V.pergandei did not vary seasonally, except that during the month of highest seed abundance, V.pergandei showed no size preference.
• 7 Pogonomyrmex rugosus was the largest ant; it preferred larger seeds and was inactive when small seeds were most abundant. Seasonal foraging activity and niche parameters were random in relation to seed abundance.
• 8 We suggest that nocturnal foraging by P.rugosus during the summer months was a response to interference with diurnal foraging by either predation frorn horned lizards or competition from V.pergandei.
• 9 Seasonal abundance of small seeds explains most of the seasonal foraging patterns of P.xerophila and V.pergandei. The summertime abundance of larger seeds during years of adequate precipitation may account for the seasonal activity patterns of P.rugosus.