ALBERT

Notes: Random amplified polymorphic DNA (RAPD) analysis was applied to eight commercial cultivars of pineapple, two intergroup hybrids and two wild species. Morphologically, pineapple is divided into the Cayenne, Queen, Spanish, Maipure and Abacaxi groups. Members of the first three groups have been analysed in this study. The cultivars ‘Tradsithong’, ‘Phuket’, ‘Sawee’ and ‘Tainan’, with spiny leaves, form the Queen group. In ‘Pattavia’, ‘Nanglae’ and ‘Petburi no. 2’ (Cayenne group), spines are confined to the leaf tips. ‘Intrachitdang’ is normally placed in the Spanish group, which is morphologically similar to the Queen group, but with inferior quality fruit. DNA amplification products were compared from 16 arbitrary 10-mer primers from which a dendrogram was constructed. The results confirmed morphological classifications for seven of the eight commercial cultivars, with the Queen and Cayenne groups as separate clusters. However, the cv. ‘Intrachitdang’ was more closely related to the Cayenne group. Two hybrids from reciprocal Cayenne × Queen group crosses, were more closely allied to the Queen group. The two wild species were outside the groups. RAPD analysis can be exploited to investigate relationships within pineapple germplasm.

Notes: SUMMARY. Assimilation budgets (i.e. assimilation = respiration + excretion + production) are presented for cohorts of P. zietziana in two salt lakes. Shrimps in Pink Lake had an assimilation rate of 1631.6 kJ m−2 year −1, those in Lake Cundare 212.1 kJ m−2 year−1. In both lakes, respiration accounted for 60–80% of assimilation. Assimilation rates for individuals (derived as assimilation = ingestion minus faecal output) are also given and compared with respiratory rates of individuals. The comparisons indicated that energy was often consumed at a higher rate by respiration than it could be supplied by assimilation. Starvation due to a low assimilation efficiency was suggested as a cause of the consistent mortality, variable growth rate of individuals and unpredictable recruitment which were characteristic of the cohorts of P. zietziana in both lakes. An analysis of mortality showed that the young had the poorest survival, as predicted by a theoretical model of a starving zooplankter and a comparison of the increase with weight of ingestion and respiration. Gross growth efficiency (production: assimilation) was 15–30%, about the same as published data on Anostracans. Net growth efficiency (production : consumption) was 5–12% and generally lower than published values reflecting the difficulty P. zietziana has in balancing its budget.

Notes: SUMMARY. 1. Recolonization rates of benthic invertebrates were estimated at five sites in the catchment of the Acheron River, in spring (October) and in summer (January), The sites ranged from those that experience short floods and high shear stress at the streambed (upstream sites) to those that experience prolonged floods and low shear stress (downstream sites). We hypothesized that these differences should affect recolonization rate.2. In October, absolute rates of recolonization of taxa (number of taxa 0.05 m−2 d−1) onto 1-m2 patches of substratum, which had been raked to remove fauna, did not vary between the three sites studied, nor did the relative rates of recolonization of taxa (absolute rate/mean number of taxa in control samples, which were taken from adjacent undisturbed patches of substratum). Absolute rates of recolonization of individuals (number of individuals 0.05 m−2 d−1) were proportional to the mean number of individuals in control samples; relative rates of recolonization of individuals (absolute rate/mean number of individuals in control samples) did not vary between sites.3. In January, absolute rates of recolonization either of taxa or individuals were positively correlated with the mean densities of taxa or individuals in control samples; relative rates did not vary between the four sites studied.4. We conclude that the benthic invertebrate communities at the various sites do not adapt to variations in flooding regime by altering relative recolonization rates. Absolute recolonization rates are directly proportional to the prevailing number of taxa or individuals at a site.

Notes: SUMMARY. The population density of the univoltine amphipod Gammarus pseudolimnaeus was estimated monthly from April 1977 to June 1978 along a 600-m reach using a form of removal sampling at 0.5, 1.5 and 2.5 m from the bank. The probability of catching an amphipod with three sweeps over an area of 0.15 m2 was 0.95. Drift and upstream migration were measured for 24 h, also monthly. Population density varied from 1600 m−2 (newly-hatched young in July) to 26 m−2 (adults) within 3 m of the bank with 95% confidence limits of 40–60% of the mean; density was highest 〈 1 m from the bank and beyond 3 m it declined to insignificant levels. No significant difference could be shown between the total catches in the drift and upstream nets over a year and there appeared to be no net migration of amphipods. Mean drift was 2 amphipods day−1.Growth was estimated from the length composition of monthly samples. Annual production (P) was 29.4 kg ha−1 for one generation of the amphipod with a P/B ratio of 4.65. Egg production accounted for only 2% of this estimate. Recruitment was calculated from regressions relating female length to clutch size and egg development time to temperature in the laboratory; mean temperature was measured in the field.Mortality was greatest in July at the beginning of the generation. It was high again in September and during winter; at these later times it was suggested that starvation occurred in addition to predation. Annual consumption (C) of organic matter for the generation calculated from published data on feeding rate was 1547 kg ha−1 which results in a P/C ratio of 1.9%.

Notes: SUMMARY. The feeding rate of G. pseudolimnaeus was measured monthly for 7 months in the field by monitoring the decline in weight of gut contents when the amphipod was starved. This decline was modelled by an exponential regression of weight on time. As the amphipods appeared to be continuous feeders, feeding rate was calculated by multiplying the dry weight of a full gut by the specific rate of emptying, i.e., the slope of the exponential regression. Specific rate of emptying was independent of animal size, but increased with temperature. Therefore, food has a longer period in which to be digested at low temperatures, which suggests that assimilation efficiency may increase.However, the assimilation efficiency of amphipods feeding on decaying maple leaves in the laboratory was only 10% and did not vary with temperature. Ingestion and egestion rates were measured in the laboratory by weighing amounts eaten and defecated. The turnover time of the contents of a full gut in the laboratory often agreed very well with turnover time measured in the field, i.e., the reciprocal of the specific rate of emptying, thus confirming the use of an exponential regression.

Notes: SUMMARY. Oxygen consumption of P. zietziana was measured monthly in two saline (〉60‰ salinity) lakes from November 1973 to November 1975 with short (〈2 h) in situ incubations in BOD bottles. Tests in which oxygen decline was monitored continuously showed that there was no handling effect and respiratory rate was constant down to 1.8–1.9 mg O2 1−1, about 40% of the usual initial concentration. Incubations over 24 h demonstrated no diurnal fluctuations in oxygen consumption. Multiple regression analysis indicated that 90% of the variance in respiratory rate (R in mg O2x10−4h−1 individual−1) was accounted for by changes in salinity (3%; S in ‰), temperature (7%; T in °C) and dry weight (8%; W in mg × 10−3): log R =−1.123+0.0025+0.021 T+ 0.756 log W. From this equation and data on population density, population respiration was calculated: 91864.5 mg O2 m−2 year−1 in Pink Lake and 12367.5 mg O2 m−2year−1 in Lake Cundare.

Notes: 1. Sites immediately below seven dams in Victoria and 12 in southern New South Wales (NSW) were sampled for macroinvertebrates using rapid bioassessment techniques. Specimens were identified to the lowest taxonomic level. The dams had different operating and discharge regimes and thus potentially different downstream effects on this fauna.2. The AUStralian RIVer Assessment Scheme (AUSRIVAS) predictive models for macroinvertebrate composition were applied to the families and genera observed at Victorian sites and to the families only at the NSW sites. Lists of predicted taxa, their probabilities of occurrence and ratios of observed to expected taxa (O/E scores) were obtained from these models.3. The mean O/E score for Victoria was 0.46 at the genus level and 0.63 at the family level; for NSW the mean score at the family level was 0.62. There was no significant difference between family level scores for the two states. Thus about 40% of expected families were missing at all sites. Family level scores were highly correlated (r=0.84–0.86, P 〈 0.001) with numbers of families or species at a site.4. There was no correlation between family O/E scores (or family and species richness) and the degree to which current discharge levels below a dam differ from the natural patterns. Thus increased hydrological deviation did not result in greater biological degradation. In addition, there was no association between these biological characteristics and whether dams released surface or bottom water.5. All the dams seemed to cause much the same disruption to the fauna. Of the families predicted to have widespread occurrence, 9–12 were found at most sites (tolerant taxa), while a larger number (14–24) were missing (intolerant taxa). The limited recolonisation below dams may well be because of the fact that dams act as barriers to drift, the most prominent route for invertebrate colonists.

Notes: 1. The larval life spans of twelve species of aseasonal aquatic insects (eight Trichoptera, three Ephemeroptera, one Odonata) were investigated in two tropical streams with near constant water temperatures.2. Life spans were estimated from equations relating larval life span to the ratio between cohort production (estimated from the size–frequency technique) and annual production (estimated from regressions in the literature).3. Life spans varied from 40 to 250 days and were positively correlated with maximum larval dry weight (r = 0.73, P 〈 0.001). Ephemeroptera had the shortest larval life spans (40–110 days), Trichoptera intermediate (95–185 days) and Odonata the longest (250 days).

Notes: SUMMARY. 1. The contribution of drift to macroinvertebrate colonization was studied over 10 days using pairs of substratum-filled trays, one suspended above the streambed (and thus able to be colonized by drift only) and one buried flush with the streambed (and thus open to colonization from all directions). Trays were filled with sand, gravel or stones.2. Colonization of sand-filled trays was rapid, being completed within 24h (i.e. no subsequent change in numbers of individuals per tray); colonization of gravel or stone-filled trays was not completed by the end of the experiment.3. Drift contributed an average of 86% of the colonizing fauna of the sand-filled trays, 36% of the fauna of the gravel-filled trays and 25% of the fauna of the stone-filled trays. The low contribution of the drift to the gravel and stones is at odds with some studies which, using similar techniques, suggest that drift is the primary source of colonizing individuals.4. Most individual species showed low contributions by drift to colonization, with the majority having contributions under 66%.5. Distinct differences were noted between the fauna colonizing the sand-filled trays and those colonizing the gravel or stone-filled trays (which were similar).6. Several species common in the drift were rare in the colonizing fauna and several species which were common colonizers were absent or rare in the drift.

Notes: 1. Spatial scale may influence the interpretation of environmental gradients that underlie classification and ordination analyses of lotic macroinvertebrate communities. This could have important consequences for the spatial scale over which predictive models derived from these multivariate analyses can be applied.2. Macroinvertebrate community data (identified to genus or species) from edge and main-channel habitats were obtained for sites on rivers from 25 of the 29 drainage basins in Victoria. Trends in community similarity were analysed by carrying out separate multivariate analyses on data from the edge habitats (199 sites) and the main-channel habitats (163 sites).3. Hierarchical classification (UPGMA) showed that the edge data could be placed into 11 site groups and the main-channel data into 12 site groups.4. Ordination analysis (hybrid multidimensional scaling) showed no sharp disjunctions between site groups in either habitat; overlap was frequent. Correlation of the ordination patterns with environmental variables showed that edge communities varied longitudinally within a drainage basin and from the east to the west of Victoria. These two trends were superimposed on one another to form a single gradient on the ordination. The taxon richness of edge communities was also related to the species richness of macrophytes at a site. Main-channel communities also displayed a longitudinal and a geographic gradient, but these two gradients were uncorrelated on the ordination.5. Community similarity only weakly reflected geographic proximity in either habitat. A preliminary subdivision of Victoria into a series of biogeographic regions did not match the pattern of distribution of site groups for the edge habitat, illustrating the difficulties of applying to lotic communities a priori regionalizations based on terrestrial features of the landscape.6. The longitudinal gradients in the two data sets were commonly observed in data gathered at smaller spatial scales in Victoria. The other gradients (geographic, macrophyte), however, were either not consistently repeated or not evident at smaller spatial scales. At small spatial scales (i.e. within a single drainage basin) gradients were related to variables that varied over restricted ranges, e.g. mean particle size of the substratum.7. Species richness was very variable when plotted against river slope or distance of site from source; both of these are measures of position on the longitudinal gradients. In contrast to suggestions in the literature, species richness did not show a unimodal trend on these gradients, or any other trend.8. Environmental gradients (apart from longitudinal gradients) that underlie predictive models of macroinvertebrate distribution are reflections of the spatial scale on which the model has been constructed and cannot be extrapolated to different scales. Models must be suited to the spatial scale over which predictions are required.