bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in productivity of the saltmarsh mosquito, Aedes vigilax (Diptera: Culicidae), and vegetation cover following culvert removal
Authors: Turner P. A. , Streever W. J.
Published: March 2003

Changes following culvert removal in the production of the saltmarsh mosquito, Aedes vigilax (Skuse), and the cover and occurrence of halophytes were investigated on Kooragang Island, New South Wales, Australia. Mosquito eggshells were collected from saltmarsh soil and used as an index of mosquito production. Saltmarsh bordering each of four tidal creeks was sampled prior to the removal of culverts from two of these creeks in 1995. All creeks were resampled two years later. In most instances, eggshell densities decreased significantly at saltmarshes affected by culvert removal, with relatively small change at reference saltmarshes. However, oviposition by Ae. vigilax was initiated in upland areas following culvert removal at one site. Sarcocornia quinqueflora cover decreased significantly at sites affected by culvert removal relative to reference sites. The cover of Sporobolus virginicus and frequency of occurrence of Triglochin striata increased significantly at one modified site, while the frequency of occurrence of Avicennia marina seedlings increased significantly at the other modified site. We suggest that culvert removal and other alterations intended to increase tidal flushing will lead to vegetation patterns and mosquito eggshell densities that typically occur in the more frequently inundated saltmarsh–mangrove complex.
Plant communities, species richness and their environmental correlates in the sandy heaths of Little Desert National Park, Victoria
Authors: Hahs A. , Enright N. J. , Thomas I.
Published: March 2003

Plant community composition and its likely environmental controls were investigated for 200 sample plots (each 100 m2) from Mediterranean‐type vegetation in the Little Desert National Park, Victoria. TWINSPAN classification revealed four readily identifiable vegetation types; mallee‐broombush, heathland, stringybark open woodland, and an assemblage intermediate between mallee‐broombush and heathland referred to here as broom‐heath. Mallee‐broombush was found on Parilla Sands characterized by high Ca levels relative to heathland and stringybark open woodlands on unconsolidated Lowan Sands. The first axis of a 2 dimensional non‐metric MDS ordination also divided heathlands (high axis scores) from mallee‐broombush (low scores), while the second separated these vegetation types from stringybark woodlands and broom‐heath. Vector‐fitting revealed significant correlations between the locations of samples in ordination space and exchangeable soil Ca, soil colour, aspect and Shannon–Weiner diversity. Highest species richness/diversity was associated with the ecotonal area between Parilla and Lowan Sands (i.e. broom‐heath) where a number of species characteristic of different assemblages had overlapping ranges. The fire‐sensitive conifer, Callitris rhomboidea, was preferentially located in stringybark woodland and broom‐heath vegetation types. Its presence was positively associated with high species richness and aspects having a southerly component. Four Callitris stands sampled for population structure were all > 40 years old and showed evidence of interfire recruitment from seeds released by old, serotinous cones. Overall, results suggest that variations in plant community composition and structure in the eastern block of the Little Desert are primarily due to variations in soil properties associated with the distribution of the two dominant substrate types, Parilla Sand and Lowan Sand. However, the interplay of topography and fire behaviour has probably been more important than substrate type in determining the distribution and population structure of longer‐lived, fire‐sensitive species such as Callitris rhomboidea.
Quantifying observer heterogeneity in bird counts
Authors: Cunningham R.B. , Lindenmayer D. B. , Nix H. A. , Lindenmayer B. D.
Published: March 2003

An essential pilot study was designed to quantify observer heterogeneity and to compare observation methods for the detectability of forest birds in stands of Eucalyptus and Pinus radiata forest as a basis for a major research project on habitat fragmentation near Tumut, southern New South Wales. Twelve experienced observers participated in the investigation. Point interval counts, zig‐zag walks and strip transects were used to count birds in both eucalypt and pine forests. The 65 species of birds recorded in the study were assigned to one of nine groups classified by a set of attributes that characterized bird detection by field observers (e.g. body size, colour and calling patterns). Observer heterogeneity varied between groups of birds and was most apparent for small birds foraging in low shrubs (species such as the white‐browed scrub wren, assigned to group 2), frequent calling, active birds (species such as the golden whistler, assigned to group 7), and midstorey, undercanopy foragers with distinctive behaviour (species such as the grey fantail assigned to group 4). For bird groups 2, 4 and 7, additional variability due to observer differences resulted in an average increase of ~ 40% in the width of a 95% confidence interval for the logarithm of bird abundance generated from a 20 minute count. Our analysis shows that taking the average of counts obtained by two or more observers would negate the increase in variance of counts due to observer heterogeneity. Few differences between methods of field observation were found. However, for frequent calling, active birds (group 7) there was evidence that more birds were heard using the point interval count method. Our study clearly demonstrated a need to either control for observer differences or to assign at least two observers to individual sites when designing bird surveys for comparative studies. Failure to do so will result in a decrease in precision of bird counts.
Effects of herbivory on growth and survival of seedlings of a rainforest tree, Alphitonia whitei (Rhamnaceae)
Authors: Jackson Robyn V. , Bach Catherine E.
Published: March 2003

This study examined the effects of insect herbivory on growth and mortality of seedlings of a mid‐ successional rainforest tree, Alphitonia whitei Braid. Two experiments were conducted in which seedlings were exposed to 0% and 50% natural defoliation by insect herbivores and placed in light gaps in simple notophyll vine forest at Paluma, near Townsville, North Queensland. In the first experiment, insect herbivory significantly increased mortality of 2‐month‐old seedlings. Smaller seedlings had significantly greater mortality rates than larger seedlings, irrespective of herbivory. A significantly greater proportion of smaller seedlings died from being smothered by fallen leaves and soil as a result of digging by vertebrates than for larger seedlings. In the second experiment, the effects of seedling age were examined by comparing 2‐month and 4‐month‐old seedlings. Mortality rates were significantly influenced by seedling age, with eight times greater survival of older seedlings than of younger seedlings. Although insect herbivory was correlated with a significant decrease in shoot mass and a significant increase in root:shoot ratio, there was no effect of insect herbivory on seedling survival in the second experiment. Thus, mortality rates were greater for seedlings if they were young or small (which indirectly results from insect herbivory), because small, young seedlings were more susceptibile to other mortality factors, such as burial by fallen debris and digging by vertebrates.
Saltmarsh as habitat for fish and nektonic crustaceans: Challenges in sampling designs and methods
Authors: Connolly Rod M.
Published: March 2003

This is a review of research into the ecological role of saltmarsh as habitat used directly by fish and nektonic crustaceans such as shrimp (prawns) and portunid crabs. The quality of information about direct use of saltmarshes by nekton is poor, with even the most influential works suffering from obvious limitations. Attempts to generalize about nekton use of saltmarshes are hampered by sampling difficulties, poor sampling design, and inconsistent reporting of flooding regime and landscape structure. The difficulty in sampling nekton from shallow, vegetated marsh flats while inundated contributes to the fragmentary results of nekton work. A range of sampling methods have been described that vary in portability, size, amount of above‐ground structure, escape rates of nekton, and expense; none has yet become standard. Poor experimental design in studies of saltmarsh nekton includes lack of replication, limited spatial scale, and lack of baseline data before management changes are made. Attempts to determine effects on commercial fisheries of losses in area or quality of saltmarsh by correlations between catch data and marsh loss should use active adaptive management. A second type of study, aimed at understanding how the saltmarsh is important to fisheries, can be tackled usefully at a smaller scale. To assist in the comparison of results from different studies, flooding regime should be reported as a proportion of time the marsh is submerged, and landscape structure as proportions of the marsh that are covered by intertidal flats, pools and drainage creeks. Flooding regime and landscape structure at the sites and at the time of sampling should then be put in the context of the typical pattern for the marsh under study.
Estuarine benthic ecology: A European perspective
Authors: McLusky Donald S.
Published: March 2003

The study of benthic ecology within European estuaries is discussed. The history of estuarine science, and the definition of an estuary is briefly reviewed. Estuarine benthic ecology is considered with regard to its geographical, economic and political context. It is shown that much recent study has been motivated by attempts to clean up estuaries, which were polluted after decades, or even centuries of pollution. Much has been achieved in the control of pollution, and many estuaries show clear signs of recovery. Particular focus has been on the estuaries entering the North Sea, with the realization that it is not the North Sea that is polluted, but its estuaries. The scientific appraisal of the benthos of estuaries has been particularly assisted by the ecosystem approach, which has both aided our understanding of their function as well as answering some of the questions posed by the impact of mankind. The European Union is identified as a powerful factor in benthic ecology, either through legislation or through the encouragement of collaborative programs, some of which have been particularly important in identifying common factors across a wide geographical spread of estuaries. It is concluded that in general estuaries have got cleaner, but that many problems remain, ranging from eutrophication through to sea‐level change. The future of estuarine benthic ecology lies in meeting the new challenges.
The social organization of a sexually dimorphic honeyeater: the Crescent Honeyeater Phylidonyris pyrrhoptera, at Wilsons Promontory, Victoria
Authors: Clarke Rohan H. , Clarke Michael F.
Published: March 2003

The social organization of the sexually dimorphic and dichromatic Crescent Honeyeater Phylidonyris pyrrhoptera (Latham 1801) was studied at Wilsons Promontory National Park between January 1994 and January 1997. All breeding attempts at one site were followed during the spring and summer of 1996. Most pairs were multibrooded, with pair‐bonds maintained throughout the study. Breeding males held well‐defined territories. Females, although generally restricting their activities to within their mate’s territory, visited other males’ territories more frequently than did their mates and did so close to the time of egg laying. Males aggressively chased intruding males, but appeared to permit intrusions by non‐mate females. Circumstantial evidence suggests some males may kill neighbour’s nestlings. Female Crescent Honeyeaters are solely responsible for nest construction and incubation. While both sexes attended nestlings, males contributed to parental care significantly less than females. Males also provided significantly less parental care than has been reported for monomorphic species of honeyeater. Single syllable calls are given throughout the year. Peaks in the rate of double and multisyllable calls corresponded with peaks in breeding activity. Only males were observed uttering loud multisyllable calls. In contrast to predictions arising from sexual selection theory and observations of the mating system of sexually dimorphic hummingbirds, the population of Crescent Honeyeaters studied exhibited a socially monogamous mating system. However, the very limited male role in parental care and non‐observance of male territory boundaries by females suggest the genetic mating system may not be one of monogamy.
Litterfall from two eucalypt woodlands in central Queensland
Authors: Grigg Andrew H. , Mulligan David R.
Published: March 2003

The mean annual litterfall at two dry woodland sites in central Queensland was 1129 kg ha–1 for an open E. populnea F. Muell. woodland (n = 2 years), and 2318 kg ha–1 for a woodland dominated by E. cambageana Maiden (n = 1 year). Leaves formed the largest component of total litterfall, which varied seasonally with a spring–summer maximum. Annual litterfall at these sites conformed with a pattern of decreasing litter production with declining annual rainfall, consistent with a range of eucalypt‐dominated communities.
Using past and present habitat to predict the current distribution and abundance of a rare cryptic lizard, Delma impar (Pygopodidae)
Authors: Dorrough Josh , Ash Julian E.
Published: March 2003

We present logistic regression models predicting the distribution and abundance of a threatened cryptic lizard, Delma impar (Pygopodidae), in the Australian Capital Territory (ACT). The models incorporate current habitat and historical land use and habitat change (woodland clearance, ploughing, grazing, fertilizer application). Information on historical land use was acquired from land survey maps, aerial photographs and from floristic indices of land management. Floristic indices were developed from a survey of local agronomists who scored individual plant species, responses to grazing, ploughing and fertilizer application. Floristic indicies proved to be more informative than floristic ordination analyses. It emerged that historical factors were of key importance for predicting the distribution and abundance of D. impar. Since European settlement, D. impar has apparently spread from primary (naturally treeless grasslands) into secondary grasslands (grassland formerly with an overstorey of trees) and has been locally excluded by some farming activities such as ploughing. We conclude that a combination of current habitat and past changes in habitat may be necessary to understand the current distributions of plant and animal species that have limited dispersal ability and that are susceptible to local temporary habitat destruction. Active conservation strategies involving, for example, assisted dispersal, may be important for these species.
Arboreal arthropod biodiversity in woodlands. II. The pattern of recovery of diversity on Melaleuca linariifolia following defaunation
Authors: Azarbayjani Fathollah F. , Burgin Shelley , Richardson Barry J.
Published: March 2003

This study examines the level of isolation of arthropod faunas present on specimens of the endemic woodland tree Melaleuca linariifolia by investigating the recovery of faunas after defaunation using insecticide. One tree from each of 21 pairs of trees was sprayed at the beginning of the project (early April 1994). After predetermined periods, three test trees were resprayed along with matched control trees. A total of 95 154 arthropods were collected and sorted during the project. The number of species present on the trees recovered within 16 weeks of spraying, with common species recolonizing within a fortnight. The rarer species both of mobile (Diptera) and relatively sedentary (Araneae) taxa reappeared at similar rates. Complete recovery of numbers occurred by week 8 after spraying. Evenness (as Simpson’s D) recovered over the first 2 months; however, both the number of individuals and the evenness continued to diverge from the pattern seen on the control trees until the end of the study. While the rate of movement of individuals and species was such as to provide an apparently complete set of replacement species within several months of perturbation, the structure of the community found on the trees was still seriously disrupted after 1 year. Comparison of the suites of species originally found on the trees with those found in the respray samples and the control samples showed that the set of colonizing species was no more similar to the original fauna of the tree than it was to those on the control tree. The relatively rapid colonization of the trees by a suite of rare species – not necessarily those that were on particular trees before perturbation – indicates that rarity was due neither to inability of the species to colonize the trees nor to the suitability of the trees for these species. Recovery of rare species was to a level similar to that found on the control trees. That the divergences from the controls continued (in number of individuals and in evenness), implies a definite connection between the different faunas of a tree and their partial isolation from fauna communities on other trees. Whatever the forces that maintain suites of species on each tree, it is not the ability of the species to reach and colonize trees, nor certain attributes of a tree, that make it suitable only for a particular subset of the species available. Trees are not isolated entities but neither are they part of a fully integrated community, either chronologically or spacially, and issues of scale are also likely to be important in understanding and estimating the dynamics and factors regulating biodiversity levels.
Predicting home range size from the body mass or population densities of feral pigs, Sus scrofa (Artiodactyla: Suidae)
Authors: Saunders Glen , McLeod Steven
Published: March 2003

Telemetry studies of feral pigs (Sus scrofa, L.) in different habitats were used to predict home range size, from (i) body mass and (ii) population density. Geometric mean regressions of the loge transformed data indicated that body mass of male and female feral pigs and mean population density were good predictors of the home range size of feral pigs (r2 = 0.81, 0.77 and 0.85 respectively). There were no sexual differences in home range size of feral pigs once the effect of body mass was taken into account. Use of these variables in models that incorporate spatial aspects along with the practical application of the results to the management of feral pig populations are briefly discussed.
Regeneration after fire in Triodia R. Br.
Authors: Rice B. , Westoby. M.
Published: March 2003

Hummock grasses in the genus Triodia R. Br. were examined at 116 recently burned locations across mainland Australia, and were recorded as regenerating by resprouting, or by seed only. Prior to this survey it was known that the capacity to resprout varies considerably in Triodia, but it was unclear whether some species might be entirely resprouting and other species entirely fire‐killed; whether this might be associated with particular traits of species or particular landscape types; or whether resprouting might be more common in particular regions such as the northern monsoonal grasslands. Seven species had both fire‐killed and resprouting populations represented among the sites examined. Three species [T. basedowii E. Pritzel, T. marginata N.T. Burbidge and T. melvillei (C.E. Hubbard) Lazarides] were recorded as fire‐killed at all sites examined, and five species [T. bynoei (C.E. Hubbard) Lazarides, T. bunicola (S.W.L. Jacobs) Lazarides, T. intermedia Cheel, T. molesta N.T. Burbidge and T. spicata N.T. Burbidge] were recorded as resprouting at all sites. Another seven species were recorded at one site only. There was no clear overall trend for fire‐killed populations to be more prevalent in south rather than north, or east vs west, or coastal vs inland parts of the continent. No clear relationships were found between regeneration strategy and site attributes. Considered as a group, resprouting species were more likely to have an open growth form than a dense growth form, whereas the opposite was true for fire‐killed species. Given that no trait either of species or of landscape was found to be a consistent correlate of resprouting, a likely inference is that resprouting might vary between different fires, even for a given population at a given site. Against this inference, fire‐killed populations had substantial densities of seedlings much more often. Longitudinal studies would be needed to demonstrate directly whether resprouting varied between different fires at a site, and to investigate the implications of this for maintenance or extinction of local populations.
Cusps and pipis on a sandy ocean beach in New South Wales
Authors: James Rodney
Published: March 2003

The effect of small‐scale variation in beach morphology has been largely ignored in studies of beach macrofauna. This study examined the distribution and abundance of the large bivalve, Donax deltoides (commonly known as the ‘pipi’) in relation to beach cusps (rhythmically spaced undulations of the beachface consisting of scalloped bays and flanking horns on a scale of tens of metres). No differences were found in the abundance of pipis downshore of cusp horns versus cusp bays at any of three sites. In contrast, previous work on a relatively low‐energy (reflective) beach reported greater abundances of bivalves below cusp bays than below cusp horns. Results suggest that the swash climate on the higher‐energy (more dissipative) beach studied here produces weaker cusping and weaker patterns in the active or passive redistribution of beach fauna by swash action. Wider more dissipative beaches also allow beach macrofauna to remain on flatter parts of the beach, further below cusps than on reflective beaches. The more rigorous study design used here may also contribute to the difference in results between this study and previous studies. However, populations of pipis below cusp bays did contain a greater proportion of small individuals (≤20 mm length) than populations on cusp horns, suggesting some effect related to beach cusps. Small pipis live closer to the beach surface as they have shorter siphons and are subject to larger rates of dislodgement and movement from cusp horns to cusp bays by swash action than are large pipis. Future ecological studies of beaches with cusps should take beach cusps and the processes producing them into account as they may affect the distribution, abundance and the size distribution of beach invertebrates.
Gradient analysis of macropod distribution in open forest and woodland of eastern Australia
Authors: SOUTHWELL C. J. , CAIRNS S. C. , POPLE A. R. , DELANEY R.
Published: March 2003

Macropod communities are most diverse in eastern Australia. Patterns of macropod abundance along environmental gradients were examined from data collected on transects located in open forest, woodland, and pasture close to forest or woodland, throughout eastern Australia from latitudes 18–33??S. Nine species of macropod were recorded on the transects. Classification of the species by their abundance on transects grouped species in accordance with the latitudinal extent of their complete ranges. Three important environmental gradients were identified from 20 environmental variables measured at each transect: a climate–human influence gradient, contrasting heavily populated, temperate areas with sparsely populated, tropical/xeric areas; an elevation gradient, contrasting high, cold, sparsely vegetated areas with low, densely vegetated areas; and a physical–vegetation gradient, contrasting steep, rocky, densely vegetated areas with flat, sparsely vegetated areas. Most species showed significant variation in abundance across these gradients. Patterns of ecological separation of the species along the gradients are examined and discussed. Total macropod abundance, richness and diversity showed a unimodal pattern along the climate‐human influence gradient, with low levels at the gradient’s extremes and high levels mid‐way along the gradient. This pattern of richness and diversity is consistent with both productivity and structural diversity hypotheses. Abundance, richness and diversity varied linearly along the elevation and physical‐vegetation gradients, with values increasing as elevation and slope increased. Variation in macropod abundance, richness and diversity along the physical–vegetation gradient may be related to shelter availability.
The diet of the long‐footed potoroo (Potorous longipes)
Authors: GREEN K. , TORY M. K. , MITCHELL A. T. , TENNANT P. , MAY T. W.
Published: March 2003

The diet of the long‐footed potoroo Potorous longipes was studied at logged and unlogged sites in East Gippsland and northeastern Victoria. Most data were for two sites in East Gippsland, with the logged site (Bellbird) having the most samples. Faecal material collected between 1993 and 1995 at Bellbird comprised 91.2 ?? 4.4% fungal remains, with no significant seasonal variation, in contrast to all other dietary studies of Australian mycophagous mammals. There were, however, significant differences in the composition of the fungi consumed seasonally and between years. One genus of fungus, Mesophellia, constituted on average 40% of all spores found in scats at Bellbird and was the most seasonally variable. Mesophellia spores were least common in scats in winter 1993 and autumn/winter 1994 but most common in winter 1995. The high occurrence of Mesophellia in scats at Bellbird reflected the disturbed nature of the site. Fungal species requiring deep, friable soils and a deep litter layer were more commonly represented at comparatively undisturbed sites.
Physiological ecology of a tropical dragon, Lophognathus temporalis
Authors: CHRISTIAN KEITH , BEDFORD GAVIN , GREEN BRIAN , GRIFFITHS ANTHONY , NEWGRAIN KEITH , SCHULTZ TIMOTHY
Published: March 2003

Lophognathus temporalis is an arboreal lizard from the wet–dry tropics of Australia. During the wet season the field metabolic rate (FMR) of the lizards was 209 kJ kg−1 d−1, but during the dry season FMR was only 62 kJ kg−1 d−1. Similarly, water flux decreased from 73.6 mL kg−1 d−1 in the wet season to 18.5 mL kg−1 d−1 in the dry season. Body temperatures (Tb) were significantly lower in the dry season, and operative temperatures, calculated by incorporating microclimatic data with characteristics of the lizards, indicated that the seasonal shift was due to changes in thermoregulatory behaviour rather than limitations of the thermal environment. By combining field measurements of Tb and FMR with laboratory measurements of standard metabolic rate over a range of Tb, we were able to subdivide the FMR into its components and to determine which factors contributed to the seasonal reduction in energy expenditure. During the dry season, lizards used 147 kJ kg−1 d−1 less energy than during the wet season, and 24% of this decrease was estimated to be due to the passive effects of lower nighttime Tb, 14% was due to the active selection of lower daytime Tb, 27% was due to the physiological shift to lower standard metabolic rates, and 35% was due to reduced activity in the dry season. Although the population size remained relatively constant (107 lizards ha−1 during the wet season and 125 lizards ha−1 during the dry season), the population structure changed, reflecting the seasonal patterns of recruitment and mortality. The number of lizards active at any one time was much lower in the dry season, reflecting the lower levels of activity in this season. The energy expenditure of the population of L. temporalis was 612 kJ ha−1 d−1 during the wet season and 113 kJ ha−1 d−1 during the dry season.
Technique for washing nectar from the flowers of Tasmanian leatherwood (Eucryphia lucida Eucryphiaceae)
Authors: Mallick Stephen A.
Published: March 2003

The technique for extracting floral nectar using micropipettes is often unsuited to flowers where nectar is produced in very small volumes and/or where nectar is highly viscous. An alternative technique for washing the viscous nectar from the flowers of Tasmanian leatherwood, Eucryphia lucida (Labill.) is described. Here, two washes with a known volume of distilled water removed 95% of total floral sugar. Using such a washing technique on exposed and bagged E. lucida flowers provided information on nectar production in this species that could not have been obtained using a standard micropipette extraction method.
What are the relative costs, limits and correlates of increased degree of serotiny?
Authors: Midgley Jeremy
Published: March 2003

There is variability in the period that serotinous species retain seeds in protective closed cones and in the sizes of the cones. Seed predation and inter‐fire recruitment have been suggested to be reasons for this variability. I argue against these two reasons. Variation in annual rates of increase in fecundity and in numbers of flowering episodes before fire should be correlated with the degree of serotiny. These two attributes are a consequence of cone size, plant architecture and degree of serotiny.
Landscape fragmentation in South Coast Renosterveld, South Africa, in relation to rainfall and topography
Authors: Kemper Jessica , Cowling Richard M. , Richardson David M. , Forsyth Greg G. , McKelly David H.
Published: March 2003

The South Coast Renosterveld has been fragmented extensively by agriculture. The extent of this fragmentation in terms of overall habitat loss, fragment sizes and fragment numbers has not been described previously, thereby limiting the development of conservation strategies for this vegetation type. Patterns of renosterveld loss in three sectors along a west–east gradient were described using LANDSAT imagery and a Geographical Information System‐based program (FRAGSTATS) for spatial pattern analysis. These patterns were then correlated with rainfall and topography measures, which are indicators of agricultural potential. Over 80% of the South Coast Renosterveld has been cultivated. Fragmentation levels increased significantly from east to west, with 33% of natural vegetation remaining in the east and only 4% in the west. Topographical variables were the strongest predictors of patterns of renosterveld loss, with fragments being largely confined to slopes too steep for ploughing; they therefore face little risk of future cultivation. These results have implications for conservation planning options for the South Coast Renosterveld. There is the potential for large reserves in the east, as well as corridor reserves along major river valleys, but for only small, isolated reserves in the west.
What’s in a site? Variation in lotic macroinvertebrate density and diversity in a spatially replicated experiment
Authors: Downes Barbara J. , Hindell Jeremy S.
Published: March 2003

Few studies have tested whether a small‐scale, experimental difference in biotic density and diversity detected at one site has any predictive capacity at other locations, nor whether such experimental differences are significant relative to overall spatial variation. In this study, we tested textural differences between substrata– previously shown to be critical to macroinvertebrate density and diversity at one site on the Steavenson River in southeastern Australia–and replicated the experiment at this site and at two others on the same river, plus at three sites on each of two other rivers (the Acheron and Little Rivers) in the same catchment. Nine rough and nine smooth colonization substrata were set out at each site on 19 December 1995, and at the start of the experiment (26 and 27 February 1996), invertebrates were hand‐picked from substrata while leaving epilithon intact. We re‐collected substrata after 28 days. Substrate texture had a consistent and strong effect upon species richness at all sites, except one, and was also associated with compositional differences at the family level. Textural effects on macroinvertebrate densities were present and varied among sites and rivers somewhat, but only three of nine common species showed significant interactions between textural effects and one of the two spatial scales, and these interactions explained <10% of variance. In most but not all cases, textural effects were the same as that previously observed–higher numbers on rough surfaces compared to smooth. Most variation in species richness and densities was explained by site, which accounted for 30% of variation in species richness, 60% of total numbers of individuals, and 9–75% of variation in abundances in all nine common taxa. Site differences were also associated with large shifts in faunal composition at the family level. Differences between rivers explained 0% of the variance in most cases but it was significant in explaining the abundance of one common species (the beetle Simsonia wilsoni), where it accounted for 59% of the variance. Our results indicate that a small‐scale effect, such as textural differences between substrata, can produce a consistent effect on measures of community structure and have some predictive capacity at other locations. However, the large differences between sites, relative to those seen between whole rivers, suggest that efforts must be directed to discovering what factors cause such localized fluctuations. Sites cannot be reasonably used as ‘representative’ of larger spatial units, such as long sections of entire rivers. Additionally, rivers may not necessarily have signature variation that always overrides localized, site‐based differences.
Functional response and area‐restricted search in a predator: seasonal exploitation of anurans by the European polecat, Mustela putorius
Authors: Lode T.
Published: March 2003

A study of the feeding habits and movements of 11 radiotracked polecats Mustela putorius in western France revealed that seasonal predation upon agile frogs, Rana dalmatina, was directly influenced by prey abundance and distribution. Although dietary structure showed the importance of mammalian prey (71.5%), polecats exploited nocturnal, terrestrial anurans in spring (31.6%). The periodic activity of anurans at spawning sites led both to a maximum density in spring and to a patchy distribution. The monthly variations in anuran dietary occurrences were associated with changes in frog availability. The functional response of polecats to frog density was sigmoidal shaped (type 3 response). Frog consumption rate increased more slowly than prey density but frogs were actively removed at higher density. It is therefore suggested that frog populations were moderately affected by the predator and this density dependent effect tends to stabilise anuran populations. Predation upon anurans was also correlated with a prey dispersion index as revealed by a polynomial regression. Polecats concentrated their predation on spawning congregations of the breeding adult frogs. Movements were smallest in spring and polecats changed their track length by increasing the difference between a succession of small movements and of longer journeys towards profitable sites. Changes in movements correlated with the anuran dispersion index and the response was sigmoidal (polynomial regression) revealing an area‐restricted search. This response may be regarded as an ‘aggregative response’ according to the first part of the definition of
Begon et al. (1996)
. Functional and area‐restricted search responses to the frog abundance and dispersion constitute an original example of predator‐prey coexistence strategies among vertebrates. I suggest that such predation could be favoured by the individualistic habits of the mustelid.
Genetic relationship of myrmecophyte (Anthorrhiza caerulea) individuals within and among territories of the arboreal ant (Dolichoderus sp.) detected using random amplified polymorphic DNA markers
Authors: Maeyama T.
Published: March 2003

The polymorphic bands of random amplified polymorphic DNA (RAPD) markers of the population of epiphytic myrmecophyte, Anthorrhiza caerulea Huxley & Jebb (Rubiaceae: Hydnophytinae), and those of its obligatory occupant ant, Dolichoderus sp. (Formicidae: Dolichoderinae), were analyzed in this study in a Papua New Guinean secondary forest. All the reproducible polymorphic bands were used as RAPD markers. Euclidean distances were calculated as the similarity indices of the band patterns, and similarities of the band patterns were analyzed using cluster analysis (group average method). It was frequently observed that the occupant ants gathered the seeds of A. caerulea and buried them into their carton trails on the bark of host trees. The colony boundaries of Dolichoderus sp. were assessed using RAPD analysis, and were clearly detected by this method. From the analyses of genetic relationships in the population of A. caerulea, it was revealed that the myrmecophytes within a certain ant territory consisted of close relatives. Therefore, it was inferred that the descendants of A. caerulea were dispersed only within the territory of a certain ant colony.
Foraging strategies of an insectivorous marsupial, Sminthopsis youngsoni (Marsupialia: Dasyuridae), in Australian sandridge desert
Authors: Haythornthwaite Adele S. , Dickman Christopher R.
Published: March 2003

This study investigated the effects of predation risk, dune position and microhabitat on foraging of the Lesser Hairy‐footed Dunnart Sminthopsis youngsoni, a small insectivorous marsupial, in the Simpson Desert of western Queensland. The intensity of foraging was assessed by establishing feeding stations (dishes containing mealworms) in open and bush microhabitats at three levels on sand dunes, and recording the numbers of prey taken by dunnarts from the stations after nightly bouts of foraging. Risk of predation was manipulated by provision of artificial illumination at alternate feeding stations on each of five occasions when trials were run. The numbers of mealworms left after feeding bouts varied inconsistently across trials, providing little evidence that dunnarts respond to habitat or predation risk while foraging. These results contrast sharply with studies of arid zone rodents, where foraging is usually sensitive to both predation risk and resource distribution. We suggest that S. youngsoni forages equally in all habitats of its sandridge environment, and experiences relatively low risk of predation whilst doing so.
Estimating forest habitat complexity in relation to time since fire
Authors: Coops Nicholas C. , Catling Peter C.
Published: March 2003

Forest structure does not form an even distribution over forested landscapes; rather, it produces a mosaic or patchwork pattern. ‘Habitat complexity scores’ provide a method of describing changes in vegetation biomass and, when assessed at randomly located plots, a frequency distribution of habitat can be developed. The frequency distribution can be used to describe characteristics of the pattern of habitat complexity, such as the mean and heterogeneity of habitat over the whole forest. In the present paper, an historical sequence of habitat complexity scores collected from 99 sites over an 18‐year period was used. The frequency distribution of the habitat complexity scores was fitted using a binomial distribution and the parameters of the binomial distribution were modelled to provide a relationship between the frequency of different habitat environments across the landscape and the time since wildfire. In most cases, the binomial distributions fitted the observed data significantly. The relationship between the binomial parameters and the time since fire was found to be highly significant (P < 0.01). Habitat complexity scores were predicted from the model solely as a function of time since fire, allowing both retrospective and future predictions of the distribution of habitats to be undertaken.
Genetic variation in the life‐history traits of Epiphyas postvittana: population structure and local adaptation
Authors: Gu Hainan , Danthanarayana Wijesiri
Published: March 2003

The light brown apple moth, Epiphyas postvittana (Walker) shows high intraspecific variability in morphological, physiological, demographic and behavioural characters. To gain insight into the extent of adaptation and evolutionary changes in response to environmental heterogeneity in this species, quantitative genetic analyses of life‐history variation were conducted for two natural populations under two thermal conditions (23°C and 28°C). Paternal half‐sib heritability and genetic correlation in six life‐history traits (i.e. development time, adult body weight, adult lifespan, age at first reproduction, the number of eggs laid during the first 5 days after emergence, and total fecundity) were compared. Significant heritabilities were shown consistently in development time; this is also true for adult body weight, except for the Canberra population at 23°C. However, neither population differences nor the effect of temperature were statistically detectable for any of these heritabilities, confirming the genetically determined flexibility. Positive genetic correlations between development time and adult body weight, and negative genetic correlations between the number of eggs laid during the first 5 days and adult lifespan were present for these populations at both temperatures, indicating the presence of genetic constraints. Pairwise comparisons of genetic correlations revealed the heterogeneity of the two populations and across temperatures. These results suggest that the structure of genetic covariance might have changed significantly during the divergence of natural populations and in response to the alteration of environmental conditions in E. postvittana.
Impact of an exotic vine Clematis vitalba (F. Ranunculaceae) and of control measures on plant biodiversity in indigenous forest, Taihape, New Zealand
Authors: Ogle C. C. , Cock G. D. La , Arnold G. , Mickleson N.
Published: March 2003

The exotic vine, Clematis vitalba L. (F. Ranunculaceae), has been in forest reserves around Taihape in the Rangitikei Ecological Region of the central North Island, New Zealand, for about 70 years. Before this weed was abundant, Taihape forests were rich in species of indigenous vascular plants, especially woody species. Clematis vitalba and its control are contributing to a loss of forest structure and of indigenous biodiversity at the ecosystem and species levels, to a lack of recruitment of indigenous species, to an influx of other weeds and to changes in growth forms of indigenous shrubs. Species that have disappeared or become uncommon in forest with C. vitalba tend to be those that are nationally threatened or uncommon, have restricted distributions or are biogeographically significant. Current control of C. vitalba in the Taihape forest is piecemeal and long‐term. It is based on mechanical and chemical methods, followed by grazing with sheep to prevent regeneration. Recommendations are made for rapid removal of C. vitalba from all untreated parts of the reserve, followed by manual control or spot‐ spraying, permanent removal of sheep, control of other serious weeds and implementation of a restoration programme.
Small mammals as potential seed dispersers in New Zealand
Authors: Williams Peter A. , Karl Brian J. , Bannister Peter , Lee William G.
Published: March 2003

Weed invasion success is strongly influenced by availability of seed dispersal vectors, which may include animals. We examined the potential of several small introduced mammals (mice, kiore, ship rats and possums) to disperse germinable seeds in New Zealand. Captive animals were fed fleshy fruit of weeds (Berberis glaucocarpa, Cotoneaster spp., Crataegus monogyna, Ilex aquifolium, Leycesteria formosa, Ligustrum sinense, Lonicera japonica, Passiflora mollissima, Pyracantha angustifolia, Sorbus hupehensis) and native species (Coprosma spp., Prumnopitys ferruginea and Solanum aviculare). We recorded the percentage of fruit consumed, seed ingested and gut passage time. Faeces were collected and the seeds extracted and tested for germination potential in an unheated glasshouse (two weed species) or under controlled conditions (11 species). The smallest rodents (mice and kiore) generally destroyed all seeds eaten. Large numbers of viable seeds of the small‐seeded (<1 mg) species, L. formosa and S. aviculare, passed through ship rats. Possums consumed the seeds of all adventive and native fruits except P. ferruginea. The proportion of seeds recovered intact from possum faeces varied with plant species and ranged from 6 to 83%. The time required for 50% of all seeds to be passed by possums ranged from 2.5 to 5.5 days with an average of 3.7 days, and was generally unrelated to simple fruit parameters such as percentage pulp and moisture content. For seeds where germination also occurred in the uneaten controls, the germination of seed from possums ranged from 3 to 78%. Germination was mostly lower in seeds from possums than in the controls, where differences were significant. Possums have major potential to disperse a wide range of fleshy fruit‐producing native and introduced plant species. Ship rats have the potential to disperse those with very small seeds.
Urbanization and exotic plants in northern Sydney streams
Authors: King Scott A. , Buckney Rod T
Published: March 2003

The vegetation and sediment of urban and non‐urban streams in the northern Sydney region were compared to examine the possible effects of urbanization on within‐stream vegetation. Many sediment characteristics were significantly different in urban streams. At least one exotic plant species was found in each urban stream sampled, but none were found in the non‐urban streams. The presence of exotic species led to the overall number and abundance of plant species being significantly higher in urban streams. Interestingly, the number and abundance of native species at the urban sites were the same as non‐urban sites, but a different suite of species was usually present. This suggests that urban streams favour exotic plants and certain native plants that are adapted to the modified conditions. The differences between the plant communities in the urban and non‐urban streams appeared to be associated with the increased level of nutrients in the urban stream sediment. Several multivariate techniques were used to assess the relative importance of individual nutrients, but no nutrients were directly associated with the observed differences. In particular, total phosphorus levels were less important in explaining the vegetation patterns than a combination of nutrients. It is therefore likely that the general increase of nutrients in stream sediment has enhanced exotic invasion and altered stream plant communities in Sydney streams.
Soil‐mediated effects on germination and seedling growth of coastal wattle (Acacia sophorae) by the environmental weed, bitou bush (Chrysanthemoides monilifera ssp. rotundata)
Authors: Vranjic John A. , Woods Matthew J. , Barnard Julian
Published: March 2003

Bitou bush (Chrysanthemoides monilifera ssp. rotundata; Asteraceae) is a major woody weed that competes with the native legume Acacia sophorae in coastal ecosystems of eastern Australia. Three glasshouse experiments examined whether litter or soil from beneath bitou bush or Acacia plants could influence seed germination and seedling growth of A. sophorae. The presence of litter decreased seed germinability and this effect was greater for bitou bush litter than for Acacia litter. Shoot growth was increased by the addition of Rhizobium after 40 days, irrespective of soil type. After 78 days, shoot and root biomass were significantly lower for seedlings grown in bitou bush soil than for those grown in Acacia soil. There was a non‐significant trend towards a lower median population of Rhizobium in the soil beneath bitou bush than in that beneath Acacia. The results demonstrated a slight effect of bitou bush on the growth of A. sophorae, which could, however, be overshadowed by the judicious use of herbicides or fire for weed control and revegetation.