Each species is subject to various biotic and abiotic factors during growth. This paper formulates a deterministic model with the consideration of various factors regulating population growth such as age-dependent birth and death rates, spatial movements, seasonal variations, intra-specific competition and time-varying maturation simultaneously. The model takes the form of two coupled reaction–diffusion equations with time-dependent delays, which bring novel challenges to the theoretical analysis. Then, the model is analysed when competition among immatures is neglected, in which situation one equation for the adult population density is decoupled. The basic reproduction number $\mathcal{R}_0$ is defined and shown to determine the global attractivity of either the zero equilibrium (when $\mathcal{R}_0\leq 1$ ) or a positive periodic solution ( $\mathcal{R}_0\gt1$ ) by using the dynamical system approach on an appropriate phase space. When the immature intra-specific competition is included and the immature diffusion rate is neglected, the model is neither cooperative nor reducible to a single equation. In this case, the threshold dynamics about the population extinction and uniform persistence are established by using the newly defined basic reproduction number $\widetilde{\mathcal{R}}_0$ as a threshold index. Furthermore, numerical simulations are implemented on the population growth of two different species for two different cases to validate the analytic results.

Photosynthetic performance in lichens can vary throughout the year. We investigate the variation in the PSII quantum efficiency as a proxy for the physiological state of the photosynthetic apparatus in two umbilicate species from the genus Lasallia. Temporal variation in F v/F m in both species was monitored at a field site in Central Spain where both species coexist. Subsequent measurements were carried out in the laboratory after 48 h preconditioning. Both species showed clear variation during the year in PSII performance, with a marked depression in F v/F m during the summer. Lasallia pustulata consistently had higher F v/F m values than L. hispanica. Both species reached higher F v/F m values after 48 h of preconditioning in the laboratory and this recovery was particularly notable in the summer months. F v/F m was highly related to antecedent weather conditions during the two days prior to measurement.

Observer-based studies often underestimate key ecological parameters. Here a fresh approach was used to analyse six years (2006–11) of attendance cycles to estimate foraging trip lengths of a lactating flipper-tagged otariid: subantarctic fur seals at Marion Island. Multi-state mark-recapture models were used to calculate detection failures of females, correct estimates accordingly, and investigate the effects of year, season, pup sex and the presence of a telemetry device on attendance cycle parameters. There were no differences between corrected and uncorrected attendance data. This is attributed to the high capture probability across all seasons (range: 83–98%). This illustrates that observer-based studies are useful to augment telemetry studies. Only season and pup sex had a significant impact on female provisioning rates. In winter, foraging trip durations were longer (t-value=25.22, P<0.0001) and attendance durations shorter (t-value=-2.15, P=0.01) than during summer. Females with female pups spent a higher proportion of their time on land (χ2=6.6, P<0.05). Male pups have higher growth demands and are larger which suggests they can deplete female milk-stores faster.

An investigation of seasonal rates of litter production in a mixed forest, Hong Kong Island, was undertaken from October 1982 to January 1984. Total annual litterfall amounted to 1218.96 g m−2 yr−1, comprising 68.6% leaves, 18.9% woody material, and 12.5% fruits, seeds and insect frass. 398.70 g m−2 of litter was recorded immediately after a severe typhoon (9 September 1983). Rates of leaf-fall and organic debris production were correlated with prevailing temperature and rainfall. Leaf-fall peaked in January 1983, March to July 1983, and in September 1983 after the typhoon, while large amounts of insect faeces were collected in May and June. Woody litter production rates were correlated with temperature and rainfall recorded in previous months. Woody litterfall exhibited no obvious periodicity but was slightly increased during March and April. The seasonal distribution of litterfall is discussed in relation to climatic factors and habitat nutrient economy.

Effects of extreme environments on food intake in human subjects are analysed as behavioural and physiological adaptations to annual and circadian rhythms, temperature and altitude. Effects of the environment on food intake through food availability have direct consequences on energy balance and body weight. Different geographical regions show variations in the composition of dietary foods, i.e. the relative proportions of carbohydrate, protein and fat. In developing countries the annual cycle appears to affect body weight through dependence on food availability. In West-European countries this effect appears to depend on physical activity. Energy and macronutrient intakes appear to follow a circadian pattern, with breakfast being relatively high in carbohydrate and dinner being relatively high in fat. In cold conditions, maintaining an adequate food intake is important in sustaining normal physiological responses to cold. Evidence for a possible cold-induced increase in appetite is poor. A condition influencing level of intake is the palatability of the food. High altitude, i.e. hypobaric hypoxia, appears to reduce appetite, energy intake and body mass, irrespective of acute mountain sickness (AMS). Meal size is reduced and meal frequency increased. Under circumstances of AMS, dissociation between appetite and hunger occurs. Thus, spontaneous adaptation to extreme environments requiring increased energy intake occurs first by adaptation of body weight to a new energy balance. In general, prevention of a negative energy balance occurs by learning with respect to food intake. After return to normal, adjustment of energy intake to the original energy balance occurs with restoration of body weight.

As a solitary species, giant pandas Ailuropoda melanoleuca have a chemical communication system that allows for avoidance with conspecifics throughout most of the year and facilitates breeding during their brief reproductive period. To date, most studies have focused on adults during the breeding season, but much remains to be learned about developmental and seasonal effects on chemical communication. Here, using odour discrimination methodology, we examine these contextual influences on chemosignalling in giant pandas for the first time. During the breeding season both adult and subadult giant pandas overtly discriminated conspecific sex using chemical cues in urine. Male urine was consistently investigated more than female urine by pandas across all age–sex categories. This preference for male urine was observed for both adult and subadult urine donors, indicating that adult levels of reproductive hormones are not necessary for the production of sex-specific urinary odour cues. By contrast, giant pandas did not overtly discriminate sex during the non-breeding season. This finding underscores that negative results for discrimination studies need to be interpreted with caution, as many contextual factors may influence overt expression of this ability. Evidence points to seasonal changes in motivation, rather than in the availability of sex-specific chemical cues in urine, as the causal factor for changing odour discrimination patterns. These and other findings are discussed in the light of the potential role that discrimination of odour plays in the regulation of competitive and reproductive interactions in nature.