Chimpanzee predation in the Mahale mountains from August 1979 to May 1982

Fifty-four episodes of predatory behavior of wild chimpanzees were recorded in Mahale, western Tanzania, from August 1979 to May 1982. The chimpanzees most frequently hunt in two seasons, during May, and from August to December. Longer-term fecal analysis indicates that predation frequency is significantly higher in the dry than in the rainy season. The seasonality of predation might be the result of the sum of various ecological factors, at least one of which is the birth season of the prey species. Most of the prey are juvenile blue duiker, bushbuck, bushpig, red colobus, and red-tailed monkeys. Sex difference is recognized in the prey selection and in the hunting method employed. Apparent local difference in the predatory behavior between Mahale and Combe chimpanzees (in Mahale,females hunt more frequently, and blue duiker is the most frequent prey) can be understood in terms of the difference either in the observation methods or in the faunal diversity and density. Other aspects of predatory behavior also are reported.     

Substrate selection and seasonal variation in densities of invertebrates in stream pools of a tropical river

Spatial distribution and seasonal variation in densities of the invertebrates were investigated for a year in three stream pools of a South Indian river. The effects of season, substrate type and water depth on the distribution were analyzed. Substrate type and season influenced the invertebrate distribution the most. Leaf packs harboured most of the organisms followed by macro-algal substrate and sand. The lowest densities were observed on rocky substrates and in the water column. Rocky substrates in shallow water supported higher densities of total invertebrates than deeper areas. Chironomid larvae dominated all benthic substrates throughout the year. Of the 19 invertebrate taxa studied, 6 showed no seasonality in densities, and most of the rest showed their highest densities in the pre-monsoon period and lowest in the SW monsoon or post-monsoon periods. However, in two of the three pools, the densities of total invertebrates were highest during the post-monsoon period with secondary peaks in the pre-monsoon period.     

Climatic governance of the latitudinal cline in seasonality of freshwater phytoplankton production

Data on the intra-annual variation in phytoplankton production for 114 southern and northern hemisphere lakes (42°S to 75° N) were combined to examine broad-scale latitudinal trends. Much of the seasonal variation in production can be statistically explained through the climatic factors of mean annual range of atmospheric temperature and annual variance in incident solar radiation, of which the amplitude of both increases with distance from the equator. Quantification of this latitudinal-climatic trend is an important step in understanding the hierarchial regulation of variability in lake trophic dynamics.     

Seasonal and spatial patterns of S,Ca, and N dynamics of a Northern Hardwood forest ecosystem

Seasonal dynamics of S, Ca and N were examined at the Huntington Forest, a northern hardwood ecosystem in the central Adirondacks of New York for a period of 34 months (1985–1988). Solute concentrations and fluxes in bulk precipitation, throughfall (TF) and leachates from the forest floor, E horizon and B horizon were quantified. Both above and below-ground elemental fluxes mediated by vegetation (e.g. uptake, litter inputs, and fine roots production) were also determined. The roles of abiotic and biotic processes were ascertained based on both changes in solute concentrations through the strata of the ecosystem as well as differences between dormant and growing seasons. Concentrations of SO₄ ²⁻, NO₃ ⁻, NH₄ ⁺ and Ca²⁺ were greater in TF than precipitation. Forest floor leachates had greater concentrations of SO₄ ²⁻, NO₃ ⁻ + NH₄ ⁺ and Ca²⁺ (9, 6 and 77 μeq L⁻¹, respectively) than TF. There were differences in concentrations of ions in leachates from the forest floor between the dormant and growing seasons presumably due to vegetation uptake and microbial immobilization. Concentrations and fluxes of NO₃ ⁻ and NH; were greatest in early spring followed by a rapid decline which coincided with a demand for N by vegetation in late spring. Vegetation uptake (44.7 kg N ha⁻¹ yr⁻¹ ) could account for the low leaching rates of N0₃ ⁻. Within the mineral soil, changes with soil depth and the absence of seasonal patterns suggest that cation exchange (Ca⁺) or anion sorption (SO₄ ²⁻) are primarily responsible for regulating solute concentrations. The increase in SO₄ ²⁻ concentration after leachates passed through the mineral soil may be attributed to desorption of sulfate that was adsorbed during an earlier period when SO₄ ²⁻ concentrations would have been greater due to elevated S inputs.     

Seasonal variation in mother-daughter groupings in Siberian ibex (Capra ibex siberica)

The association of three pairs of mother-yearling Siberian ibex was recorded by noting the distance between the mothers and daughters at 5-min intervals for 1–2-h observation periods for 1 yr at the Brookfield Zoo. Monthly averages of climatological data were obtained. All three pairs showed a seasonal fluctuation of association, with a higher level during spring and fall-winter and a low degree of sociality in midsummer and late winter. Within the high social periods, short 1–3-wk periods of low association occurred, which were correlated to actual rut and calving times in individual females. The mother-daughter associations were most highly correlated to day length and sunrise of the climatological measures. These data seem to support the original hypothesis that these social periods, which began as developmental associations in the infant, aid in keeping the matrifocal herd structure together despite aggression at the times of rut and calving. It seems also that the social cycling, although linked to reproductive cycling, has its own physiological mechanism.     

A twofold role for global energy gradients in marine biodiversity trends

Explanations for major biodiversity patterns have not achieved a consensus, even for the latitudinal diversity gradient (LDG), but most relate to patterns of solar energy influx into Earth systems, and its effects on temperature (as biochemical activity rates are temperature sensitive) and photosynthesis (which drives nearly all of the productivity that fuels ecosystems). Marine systems break some of the confounding correlations among temperature, latitude and biodiversity that typify the terrestrial systems that have dominated theoretical discussions and large‐scale analyses. High marine diversities occur not only in warm shallow seas where productivity may be either low or high, depending on regional features, but also in very cold deep‐sea regions, indicating that diversity is promoted by stability in temperature and in trophic resources (nutrients and food items), and more specifically by their interaction, rather than by high mean values of either variable. The common association of high diversity with stable but low to moderate annual productivity suggests that ecological specialization underlies the similarly high diversities in the shallow tropics and deep sea. Recent work on shallow‐marine bivalves is consistent with this view of decreasing specialization in less stable habitats. Lower diversities in shallow seas are associated with either high thermal seasonality (chiefly in temperate latitudes) or highly seasonal trophic supplies (at any latitude), which exclude species that are adapted to narrow ranges of those variables.     

Body size clines in the European badger and the abundant centre hypothesis

Aim To test the abundant centre hypothesis by analysing the physical and climatic factors that influence body size variation in the European badger (Meles meles). Location Data were compiled from 35 locations across Europe. Methods We used body mass, body length and condylo‐basal length (CBL) as surrogates of size. We also compiled data on latitude, several climatic variables, habitat type and site position relative to the range edge. We collapsed all continuous climatic variables into independent vectors using principal components analysis (PCA), and used a general linear model to explain the morphometric variation in badger populations across the species’ range. Results Body mass and body length were nonlinearly and significantly related to latitude. In contrast, CBL was linearly related to latitude. Body mass changed nonlinearly along the temperature (PC1) gradient, with the highest values observed at mid‐range. Furthermore, body mass, body length and CBL differed significantly among habitats, with badgers showing larger size in temperate habitats and core areas relative to peripheral zones. Main conclusions Our analysis supports the nonlinear pattern predicted by the abundant centre hypothesis only for body mass and body length. These results imply that individuals are largest and heaviest at the centre of the climatic range of badger distribution. Variation of CBL with latitude follows a linear trend, consistent with Bergmann’s rule. Our results provide mixed support for the abundant centre hypothesis, and suggest food availability/quality to be the main mechanism underlying body size clines in this species.     

The ichthyoplankton of a seasonally closed estuary in temperate Australia. Does an extended period of opening influence species composition?

Fish eggs and larvae were collected monthly between September 1987 and April 1989 from sites throughout the main basin and within the saline regions of the two main tributary rivers of Wilson Inlet, a seasonally closed estuary in south-western Australia. Of the eggs, 43.7% belonged to Engraulis australis (Shaw) and the rest to unidentified teleosts. The larval fish assemblage comprised 17 families represented by 25 species. The Gobiidae contained the highest number of species (four) and contributed approximately 57% of all larvae caught. Pseudogobius olorum (Sauvage) and E. australis were the most abundant species, contributing 43.9 and 27.9% to the total larval catch, respectively. The larvae of species which breed within Wilson Inlet dominated the assemblage, both in terms of number of species (64%) and contribution to total catch (99.9%). The numbers of the eight marine species and one freshwater species represented in the ichthyoplankton were very low. Classification and multi-dimensional scaling ordination showed that the composition of the larval fish fauna at the various sites during a period when the estuary remained open to the sea (December 1988-April 1989) was similar to that of the corresponding sites during the same period in the previous year when the estuary had become closed (December 1987-April 1988). This can be attributed to the spatial distribution, time of occurrence and abundance of estuarine-spawned larvae being similar in the two periods and to the rarity of marine-spawned larvae, even in the spring and summer of 1988/1989 when the estuary was open for the whole time when most marine teleosts spawn in south-western Australia. The low occurrence of marine-spawned larvae in Wilson Inlet reflects the fact that tidal water movement within the basin of the system is so small that it is unable to facilitate the transport and dispersion of larvae. The ichthyoplankton of Wilson Inlet resembles that of other poorly-flushed estuaries in that it is low in species richness and dominated by estuarine-spawned larvae.     

Genome size evolution is associated with climate seasonality and glucosinolates,but not life history,soil nutrients or range size,across a clade of mustards

Background and AimsWe investigate patterns of evolution of genome size across a morphologically and ecologically diverse clade of Brassicaceae, in relation to ecological and life history traits. While numerous hypotheses have been put forward regarding autecological and environmental factors that could favour small vs. large genomes, a challenge in understanding genome size evolution in plants is that many hypothesized selective agents are intercorrelated.MethodsWe contribute genome size estimates for 47 species of Streptanthus Nutt. and close relatives, and take advantage of many data collections for this group to assemble data on climate, life history, soil affinity and composition, geographic range and plant secondary chemistry to identify simultaneous correlates of variation in genome size in an evolutionary framework. We assess models of evolution across clades and use phylogenetically informed analyses as well as model selection and information criteria approaches to identify variables that can best explain genome size variation in this clade.Key ResultsWe find differences in genome size and heterogeneity in its rate of evolution across subclades of Streptanthus and close relatives. We show that clade-wide genome size is positively associated with climate seasonality and glucosinolate compounds. Model selection and information criteria approaches identify a best model that includes temperature seasonality and fraction of aliphatic glucosinolates, suggesting a possible role for genome size in climatic adaptation or a role for biotic interactions in shaping the evolution of genome size. We find no evidence supporting hypotheses of life history, range size or soil nutrients as forces shaping genome size in this system.ConclusionsOur findings suggest climate seasonality and biotic interactions as potential forces shaping the evolution of genome size and highlight the importance of evaluating multiple factors in the context of phylogeny to understand the effect of possible selective agents on genome size.     

Mate guarding in relation to seasonal changes in the energy reserves of two freshwater amphipods (Gammarus fossarum and G. pulex)

1. We assessed sex‐specific seasonal changes in major energy storage compounds (triglycerides, glycogen) in Gammarus fossarum and Gammarus pulex collected from the field, with respect to their reproductive activity. 2. The dynamics of stored energy followed a seasonal pattern in both species and sexes. Moreover, over a 4‐year period, these changes were independent of the year in which they were investigated. Stored energy reached a peak in late winter, but was depleted in late summer and early autumn, coinciding with the reproductive periods. 3. Triglyceride (annual mean ± SD) accounted for 79.7 ± 11.9% of the total stored energy and was responsible for the seasonal pattern. In contrast, glycogen contributed a lesser percentage (20.3 ± 11.9%). Over the study period, the amount of stored energy ranged between 0.39 and 4.08 kJ g^?1 dry mass (triglyceride: 0.19–3.69 kJ g^?1 dry mass; glycogen: 0.14–0.80 kJ g^?1 dry mass). 4. In both species, the energy reserves of males were drastically depleted shortly before the cessation of precopulatory mate guarding in the field, thus offering a bioenergetic explanation for the reproductive period in these two widespread species.