Larger Remnants Research Articles

THE FIRST EVIDENCE OF BIOEROSION IN CHITINOUS LACUSTRINE MICROFOSSILS FROM GLACIAL LAKES (LATE PLEISTOCENE AND HOLOCENE, BOHEMIAN FOREST)

ABSTRACT Microbioerosion structures are a common sign of microbial activity known mainly from marine environments and calcareous substrates, or from pollen records. However, the same phenomenon has been overlooked in animal fossils preserved in lake sediments. We studied 430 fragments of chitinous microfossils from three central European glacial lakes and detected microboring structures in approximately 10%. The microfossils belong to two size groups: (1) spherical objects with lengths ranging from 50 to 300 μm that are probably microturbelarian (Turbellaria: Rhabdocoela) cocoons, and (2) larger remnants (up to 2 mm long) of caddisfly (Insecta: Trichoptera) frontoclypeal apotomes. Four microbioerosion morphotypes were distinguished: (1) small holes (< 0.6 μm) oriented perpendicular to microfossil walls, likely produced by bacteria or fungi; (2) simple meandering tunnels and; (3) asterisk-like tunnel structures produced by fungi and/or fungus-like organisms; and (4) abrasions caused by biofilms. The maximum diameter of the simple holes and both tunnel structures depended on host-microfossil size: a higher diversity of microbioerosions was found on larger chitinous fragments. We propose that the good preservation of microfossils in the studied sediment samples might be due to rapid transport to the anoxic profundal zone or by rapid burial in anoxic sediments.

Gastric outlet and duodenal/ileal obstruction due to gastric phytobezoar

We herein present the case of an 83-year-old man, ASA status III, with a fragmented gastric phytobezoar causing obstruction in different parts of the gastrointestinal tract. The initial mass was obviously in the stomach, and due to continuing coughing and vomiting the bezoar was fragmented. The apex of the bezoar moved through the deformed pyloric channel, temporarily occluding first the duodenojejunal flexure and afterwards the ileus, while the larger remnants repeatedly sealed off causing gastric outlet obstruction. At emergent laparotomy, a gastrojejunostomy was created through which both bezoars were extracted, and the operation was completed with a vagotomy. The patient had an uneventful postoperative outcome and is doing well at 12-month follow-up. Complicated bezoars require emergent surgical removal.

Artefacts induced by coiled intracranial aneurysms on 3.0-Tesla versus 1.5-Tesla MR angiography—An in vivo and in vitro study

ObjectiveTo compare metal-induced artefacts from coiled intracranial aneurysms on 3.0-Tesla and 1.5-Tesla magnetic resonance angiography (MRA), since concerns persist on artefact enlargement at 3.0Tesla. Materials and methodsWe scanned 19 patients (mean age 53; 16 women) with 20 saccular aneurysms treated with coils only, at 1.5 and 3.0Tesla according to standard clinical 3D TOF-MRA protocols containing a shorter echo-time but weaker read-out gradient at 3.0Tesla in addition to intra-arterial digital subtraction angiography (IA-DSA). Per modality two neuro-radiologists assessed the occlusion status, measured residual flow, and indicated whether coil artefacts disturbed this assessment on MRA. We assessed relative risks for disturbance by coil artefacts, weighted kappa's for agreement on occlusion levels, and we compared remnant sizes. For artefact measurements, a coil model was created and scanned with the same protocols followed by 2D MR scans with variation of echo-time and read-out gradient strength. ResultsCoil artefacts disturbed assessments less frequently at 3.0Tesla than at 1.5Tesla (RR: 0.3; 95%CI: 0.1–0.8). On 3.0-Tesla MRA, remnants were larger than on 1.5-Tesla MRA (difference: 0.7mm; 95%CI: 0.3–1.1) and larger than on IA-DSA (difference: 1.0mm; 95%CI: 0.6–1.5) with similar agreement on occlusion levels with IA-DSA for both field strengths (κ 0.53; 95%CI: 0.23–0.84 for 1.5-Tesla MRA and IA-DSA; κ 0.47; 95%CI: 0.19–0.76 for 3.0-Tesla MRA and IA-DSA). Coil model artefacts were smaller at 3.0Tesla than at 1.5Tesla. The echo-time influenced artefact size more than the read-out gradient. ConclusionsArtefacts were not larger, but smaller at 3.0Tesla because a shorter echo-time at 3.0Tesla negated artefact enlargement. Despite smaller artefacts and larger remnants at 3.0Tesla, occlusion levels were similar for both field strengths.

Occurrence of dark septate endophytes in Nothofagus seedlings from Patagonia, Argentina

Temperate forests of southern Argentina and Chile cover a wide latitudinal and altitudinal range on both sides of the Andes, with Nothofagus species being one of the main tree species. Most of the larger remnants are protected within the limits of national parks and forest reserves. However, some of these are invaded by exotic conifers such as Pseudotsuga menziesii. In order to better understand the mycorrhizal condition within the Nothofagus–P. menziesii interaction, transects were established at six study sites along the effective recruitment area. Three treatments were established: Nothofagus forest without P. menziesii invasion (Forest), Nothofagus–P. menziesii matrix (Interface) and P. menziesii plantation lacking Nothofagus specimens (Plantation). A 2 kg mixed soil sample was taken at each treatment site and kept in brand-new plastic bags. A soil bioassay with Nothofagus seedlings acting as baits was set to evaluate the mycorrhizal inoculum potential and soil-fungi composition at each sampling treatment. Forty percent of the evaluated seedlings were found to be colonised by dark septate endophytes (DSE) fungi. Ectomycorrhizal colonisation percentage was significantly higher in plants growing in Forest soils (mean = 57.77%) when compared with Interface (mean = 42.53%) and Plantation (mean = 44.65%). The high incidence of DSE in young roots of Nothofagus seedlings in this study supports the hypothesis that DSE might be pioneering colonisers of young tree seedlings in secondary successional environments. For future interventions in the forest, either with productive or protective intentions, it should be taken into account the incidence of these fungi, which may have an important positive role in Nothofagus forest post-invasion recovery.

Community (re)organization in an experimentally fragmented forest landscape: insights from occupancy–scale patterns of common plant species

AbstractQuestionHow does experimental habitat fragmentation of a temperate Australian eucalypt forest affect local population patterns of common plant species 22 yr after landscape transformation to a pine plantation?LocationWog Wog Habitat Fragmentation Experiment, southeast Australia.MethodsWe use occupancy–scale relationships to examine the patterns of community organization of common understorey plant species in fragmented forests (small: 0.25 ha; large: 3.062 ha) relative to an intact native forest.ResultsOccupancy–scale patterns for intact forest and large‐sized remnants were isotropic; slope (z) values ranged across all values, from aggregated to scattered. In the smallest remnants, however, mean and median z values, as well as their interquartile range, were significantly lower than expected. The convergence in occupancy–scale relationships in small remnants hints that many of the commonest plant species have become even more common (i.e. aggregated).ConclusionsThe ecological assembly processes that influence common species in small‐sized remnants differ from those in larger remnants and intact forest. Fragmentation effects on assembly processes are greater at smaller patch sizes because these habitats are likely altered by changed environmental filters more so than large patches. Such shifts may have implications for habitat structure, ecosystem function and food web interactions in small remnant forests.

When more is less: Urban remnants support high bird abundance but diversity varies

Urban remnant vegetation, especially where it occurs in public parks, allows for relatively easy access for ongoing biodiversity monitoring. However, relatively little baseline information on bird species distribution and abundance across a range of identifiable urban remnants appears in the published literature. We surveyed the relative abundance and distribution of birds across urban and suburban remnant vegetation in Melbourne, Australia. One hundred and six species were recorded, of which 98 were indigenous. Red wattlebirds had the highest mean relative abundance with 2.94 birds/ ha, followed by rainbow lorikeets (2.51), noisy miners (1.93), brown thornbills (1.75) and spotted doves (0.96). There was no obvious trend between overall relative abundance and the size of the remnant, in contrast to species richness which was positively correlated with remnant size. The data revealed that some species were either totally restricted to, or more abundant in, larger remnants and generally absent from smaller remnants. Some of the more common birds (crimson rosella, superb fairy-wren, spotted pardalote and black-faced cuckoo-shrike) recorded during this study were detected at similar densities to those found in comparable vegetation to the east of Melbourne within a largely forested landscape. Other species occurred at much lower densities (e.g., white-browed scrubwren, brown thornbill, eastern yellow robin and grey fantail) or had habitat requirements or ecological characteristics that could place them at risk of further decline or local extinction in the urban area. We identify a suite of bird species of potential conservation concern within Melbourne’s urban landscape. The establishment of repeatable, fixed-point, and long-term monitoring sites will allow for repeat surveying over time and provide an early warning of population declines, or conversely an indication of population increase for other species.

Distribution and abundance of the south-eastern form of the greater long-eared bat Nyctophilus timoriensis.

In south-eastern Australia, the greater long-eared bat (Nyctophilus timoriensis) has been rarely captured and is considered uncommon, although large areas within its range have received little survey effort. We collate existing capture records and present new data on N. timoriensis captures from recent fauna inventory surveys across the western slopes and plains of New South Wales (NSW). From 1628 trap nights at 39 study areas, 118 N. timoriensis were captured out of a total of 8266 bats. In larger remnants in the Brigalow Belt South Bioregion, N. timoriensis was captured at a rate of 0.1 to 0.6 per trap night and made up 7 to 9% of bat captures. This was approximately an order of magnitude greater than in other study areas throughout western NSW. There were no captures from the Darling Riverine Plains Bioregion. These surveys show that the large vegetation remnants of Goonoo, Pilliga West and Pilliga East study areas are a distinct stronghold in the distribution of the south-eastern form of N. timoriensis.

The Habitat Quality of Private Land Box-Ironbark Remnant Vegetation in Southern Australia

ABSTRACT Approximately 75% of the Victorian Box-Ironbark ecosystem has been cleared since European settlement. There are few public land areas of high habitat quality, and significant Box-Ironbark remnant vegetation (BIR) is known to exist on private land. A landholder mail survey collected information about BIR to ascertain its size, use and habitat quality. Ground-truthing validated the landholder assessment of habitat quality. Livestock grazing had impacted 50% of BIR, and approximately 20–50% was of moderate to high quality. Fifty-four percent of BIR were less than 15 ha. Remnant size had the largest impact on quality, with larger remnants being of higher quality.

Diagnostic 123I and 131I activities and radioiodine therapy

Urinary iodine excretion (UIE) provides information about iodine supply and release. In the present study we investigated effects of the application of different radioiodine isotopes on UIE in patients with differentiated thyroid carcinoma (DTC). In 91 consecutive patients with DTC UIE, measured as iodine/creatinine ratio, was determined before and after application of 123I and 131I for diagnostic or therapeutic purposes. Additionally, remnant volume (V) was determined prior to therapy. Group A consisted of 33 patients with supposed successful ablation of DTC. These patients received 370 MBq 131I for diagnostic use and served as controls. 58 patients (group B) with remnants, relapses and metastases received 370 MBq 123I for diagnostics prior to therapy with 1.5-22.2 GBq 131I. Factors influencing individual changes in urinary iodine excretion (deltaUIE) were investigated by using non-parametric tests. In group A UIE did not change significantly after application of 131I. As well, UIE remained unchanged after diagnostic application of 123I in group B. In contrast, UIE increased significantly already 24 h after therapeutic application of 131I in this group. In patients with small remnants (V < 2.5 ml) a significant but only moderate increase of UIE could be observed (average increase: 47 microg I/g crea). In patients with larger remnants, with relapses or metastases increase of UIE values was significant and more pronounced. It was confirmed that UIE increased significantly during radioiodine therapy in patients with DTC and radioiodine-accumulating tissue. The increase of UIE after therapeutic administration of radioiodine can be explained by the disintegrated thyroid follicles in thyroid remnants. The radioiodine-induced iodine release may be one reason for thyroid "stunning" even after application of diagnostic amounts of 131I.

Colonization and extinction of ant communities in a fragmented landscape

Abstract In this paper we tested the assumption that smaller and more isolated remnants receive fewer ant colonizers and lose more species. We also tested hypotheses to explain such a pattern. We sampled ants in Brazil for 3 years in 18 forest remnants and in 10 grasslands between them. We tested the influence of remnant area and isolation on colonization rate, as well as the effect of remnant area on extinction rate. We tested the correlation between remnant area and isolation to verify the landscape design. Colonization rate was not affected by remnant area or isolation. Extinction rate, however, was smaller in larger remnants. Remnant area and isolation were negatively correlated. We tested two hypotheses related to the decrease in ant species extinction rate with increased remnant area: (i) small remnants support smaller and more extinction‐prone populations; and (ii) small remnants are more often invaded by generalist species, which suffer higher extinction inside remnants. The density of ant populations significantly increased with area. Generalist species presented a lower colonization rate in larger remnants, contrary to the pattern observed in forest species. Generalist species suffered more extinction than expected inside remnants. The lack of response of colonization rate to remnant area can be explained by the differential colonization by generalist and forest species. The decrease of ant population density in smaller remnants could be related to loss of habitat quality or quantity. The higher colonization by generalist ant species in the smaller remnants could be related to landscape design, because smaller remnants are more similar to the matrix than larger ones. Our results have important implications for conservation strategies because small remnants seem to be more affected by secondary effects of fragmentation, losing more forest species and being invaded more often by generalist species. Studies that compare only species richness between remnants cannot detect such patterns in species composition.

Repercussões da persistência de grandes remanescentes tireoideanos após tireoidectomia bilateral para carcinoma diferenciado de tireóide

Twenty-three patients submitted to thyroidectomy and before ablative therapy and with cervical uptake >10% were compared to 48 patients with uptake <2%. All but 3 patients with large remnants reached TSH levels >30 mIU/l after thyroxin withdrawal. Cervical pain requiring anti-inflammatory treatment after radioiodine was more frequent in patients with larger remnants (34.7% vs. 10.4%). Remnant ablation was successful in 56% of the individuals with uptake >10% and in 93.3% of those with uptake <2%. The sensitivity of diagnostic scanning for pulmonary metastases was similar (71.4% vs. 77.7%). The specificity of stimulated thyroglobulin at a cut-off of 5 ng/ml was 100% for patients with discrete remnants but only 37.5% for the others. We conclude that significant thyroid remnants (cervical uptake >10%) result in a lower efficacy of ablation, cause more local symptoms after radioiodine, and compromise the specificity of thyroglobulin measurements.

Simulating the Long-term Response of Tropical Wet Forests to Fragmentation

In the coming decades, a large fraction of the world’s tropical forests will be fragmented into remnants surrounded by secondary vegetation, landuse areas, or roads. It is important to develop integrative tools to monitor the evolution of these fragmented ecosystems. We used the individualoriented and process-based forest growth simulator FORMIND2.0 to investigate the spatial and temporal effects on standing biomass and functional diversity of various intensities and patterns of fragmentation within a forest landscape. The simulator was calibrated for an old-growth wet forest in French Guiana, South America. We found that the standing biomass of forest remnants was reduced significantly compared to a similar area of nonfragmented forest. When fewer but larger remnants were created rather than many small ones, the total loss in biomass and the increase in the abundance of earlysuccessional species were significantly reduced, confirming that edge effects dominate the functioning of forest remnants. We also performed simulations of secondary succession after the landscape had been abandoned. The simulated recovery time in those secondary forests depends on both the size of cleared area and the spatial pattern of the remnant forests.

Does variation in patch use among butterfly species contribute to nestedness at fine spatial scales?

A nested pattern occurs whenever the species observed in depauperate habitat patches are a subset of those found in more species‐rich patches. Ecologists have documented many instances of nestedness caused by population‐level processes such as colonization and extinction at biogeographic scales. However, few researchers have examined whether nestedness may exist at fine scales due to the ways in which individual organisms discriminate among potential habitat patches. In 1999, we experimentally fragmented an old‐field habitat into patches of varying size to test whether nestedness could exist on a fine spatial scale. Five treatments of differing patch size were replicated five times in a Latin square design by selectively mowing 15×15 m2 plots within an old‐field (patch areas: 225, 180, 135, 90, and 45 m2). Specifically, we tested whether butterflies foraging within a network of patches differing in area conformed to a nested subset structure. We also classified species according to (1) their flight height while foraging (high or low), and (2) their adult habitat breadth (ubiquitous, general, or restricted) to determine whether nestedness could be explained by difference in species’ tendency to discriminate among patches differing in area. We found significant evidence that a community of foraging Lepidoptera conformed to a nested subset structure based on the difference between the observed nestedness within the butterfly community and the nestedness obtained from randomly generated species presence/absence matrices. Poisson regression analyses demonstrated that high‐flying, habitat‐restricted species avoided the smallest patches (90 and 45 m2) in favor of larger remnants, whereas low‐flying, habitat generalists used all patch sizes. Thus, our study is one of the first to demonstrate that nestedness among species subsets can be observed at fine spatial scales (within a single 1.5 hectare field) and may be maintained by species behavioral differences: discriminating species (i.e. high‐flying, habitat restricted) avoided the smallest patches, and less discriminating species (i.e. low‐flying, ubiquitous) were distributed throughout the field without regard to patch size. Our results also suggest that nestedness should be viewed as yet another scalar pattern in ecology, generated by variation in patch use by individuals at fine‐scales as well as the more traditionally invoked processes of extinction and colonization of species at broad‐scales.

Dispersal and population dynamics of the blue-breasted fairy-wren, Malurus pulcherrimus, in fragmented habitat in the Western Australian wheatbelt

The blue-breasted fairy-wren, Malurus pulcherrimus, is a small, permanently sedentary, socially monogamous, co-operatively breeding, long-lived Australian passerine, whose core distribution is contained within the Western Australian wheatbelt. Little is known of their dispersal capabilities and population dynamics, knowledge of which are urgently needed as their preferred habitat becomes increasingly fragmented and degraded, due to clearing for agriculture. From 1993 to 1998, we studied a colour-banded population of blue-breasted fairy-wrens living in 13 small, 3 medium-sized and one large habitat remnant in an agricultural landscape at Wyalkatchem. Wrens in small remnants were more likely to disperse between remnants than were those in larger remnants. Females were likely to travel further and were more likely to disperse between remnants than were males. Dispersing females in the largest remnant moved a median straight-line distance of 400 m compared with 3 km for females in the smaller remnants. The furthest recorded movement was 9 km (straight-line distance) or about 14 km by the nearest corridor route. Females living in fragmented habitat may have to travel many times the distances travelled by females in unfragmented habitat. Demographic modelling shows that, over an average run of seasons, the wrens in the study population will produce sufficient yearlings to fill all breeding vacancies, provided none are lost during dispersal. However, in our study landscape, an estimated 11% of dispersers were lost to the population (i.e. either dispersed outside the study area or died during dispersal). We show that the remnants in the study landscape can be divided into neighbourhoods based on their relative connectivity. About 14% more potential dispersers were lost from the poorly-connected areas than from a core 'well connected' neighbourhood. This difference would be sufficient to cause population decline in a poorly connected neighbourhood. We conclude that, for species with poor dispersal capacity living in fragmented habitat, failure to maintain an adequate corridor network could be one of the most important factors contributing to a species' decline.

A prospective longitudinal study of landscape matrix effects on fauna in woodland remnants: experimental design and baseline data

The design of a longitudinal landscape-scale “natural experiment” of Australian woodland vertebrates is described. The experiment will allow the direct study of changes in fauna inhabiting woodland fragments as the surrounding grazed landscape is transformed into a radiata pine ( Pinus radiata) plantation. It will also provide data to enable the study of relationships between fauna and habitat and landscape variables, both over time and among sites. Data for terrestrial mammals, arboreal marsupials, and reptiles occurring in woodland remnants surrounded by newly planted radiata pine seedlings and pasture are presented. These data provide a reference set against which future changes in vertebrate fauna can be assessed and hence will be baseline data for the longitudinal study. Statistical analyses for several species showed that arboreal marsupials are more likely to be found in larger remnants that contain more trees with cavities and the four-fingered skink ( Carlia tetradactyla) is more likely to be found either where there are more exposed rocks or more dead trees. We predict that these responses will change as the surrounding landscape matrix is transformed, particularly for arboreal marsupials such as the common ringtail possum ( Pseudocheirus peregrinus), a species for which stands of radiata pine will provide suitable or partially suitable habitat.

Management of Thyroid Cancer: Radioiodine Ablation, “Stunning,” and Treatment of Thyroglobulin-Positive, 131I Scan-Negative Patients

To present an overview of three controversial issues in the management of thyroid cancerradioiodine ablation, "stunning," and treatment of thyroglobulin-positive, (131)I scan-negative patients. Pertinent studies from the literature and personal experience are reviewed. Radioiodine is commonly administered after thyroidectomy to destroy residual normal thyroid cells, a procedure known as thyroid ablation. Currently, use of radioiodine for ablation has been shown to decrease the risk of recurrence, increase the sensitivity of postablation whole-body scanning with radioiodine, and increase the sensitivity of serum thyroglobulin testing. With use of conventional criteria, administration of 30,000 rad to the thyroid remnant will successfully ablate approximately 95% of remnants that are 2 g or less, but the success rate is lower in patients with larger remnants. The same degree of success can be achieved by administration of 50 mCi of (131)I. The use of larger amounts of radioiodine does not increase the number of patients with successful thyroid ablation. If recurrence is used as the endpoint, no difference has been observed between patients who were given 29 to 50 mCi and those given 50 to 100 mCi for ablation. Stunning occurs when (131)I administered for preablation imaging causes a decrease in uptake of radioiodine subsequently given for ablation. Scanning doses of 2 mCi or less have not been shown to cause stunning, but the risk increases progressively with larger amounts. Therapeutic radioiodine is being given to patients with detectable thyroglobulin but negative (131)I whole-body scans with increasing frequency. Although posttherapy scans show abnormal uptake in most cases, no available evidence indicates that these patients benefit from treatment. Radioiodine ablation after thyroidectomy decreases the risk of recurrent thyroid cancer and facilitates subsequent radioiodine treatment. Stunning can be avoided by use of a maximal scanning dose of 2 mCi. It seems reasonable to treat patients who have progressively increasing thyroglobulin levels but to continue careful observation in those with stable or decreasing thyroglobulin concentrations.

HABITAT FRAGMENTATION, LANDSCAPE CONTEXT, AND MAMMALIAN ASSEMBLAGES IN SOUTHEASTERN AUSTRALIA

We examined relationships between mammalian assemblages and landscape context and habitat fragmentation in southeastern Australia. Data were gathered from spotlighting and hair sample surveys at 166 sites in 3 different spatial (landscape) contexts: remnant patches of native eucalypt forest surrounded by an extensive plantation of exotic radiata pine ( Pinus radiata—86 sites), the radiata pine plantation (40 sites), and large areas of continuous native eucalypt forest that occurred at the margins of the plantation (40 sites). Continuous eucalypt forest supported more species than eucalypt patches, although some species were more common in the patch areas. All assemblages in the radiata pine sites were substantially impoverished. There was a significant patch size effect for the total mammalian assemblage and for terrestrial native mammals but not for arboreal marsupials. Bigger remnants supported an assemblage different from (and more species rich) that found in smaller remnants, particularly those ,3 ha where many mammal species occurred less frequently. The landscape context and patch area effects recorded in this study have important implications for plantation design in southern Australia. Eucalypt remnants should be exempt from clearing during plantation development; larger remnants are the most important areas.

Postoperative hippocampal remnant shrinkage and memory decline: a dynamic process.

The severity of postoperative memory decline in unilateral temporal lobectomy patients has been associated both with the extent of hippocampal resection and MRI measures of preoperative hippocampal volume. Serial MRI of the hippocampal remnant suggest that further volume loss occurs in the immediate postoperative period. For the majority of patients, this process appears to stabilize within the first 3 months. The authors examined the relationship between the dynamic volume of the hippocampal remnant and postoperative memory decline. Seventeen adult temporal lobectomy patients (nine, left; eight, right) underwent a full neuropsychological assessment and a volumetric MRI scan preoperatively and 3 months postoperatively. Examination of the posterior hippocampal remnant on the postoperative scan revealed volume loss in this segment compared to the identical segment preoperatively in 16 of 17 cases. Spearman's correlations were used to examine the relationship between postoperative memory decline (postoperative - preoperative memory scores) and the postoperative/preoperative hippocampal remnant volume ratio. The volume of the hippocampal remnant left in situ was significantly correlated with postoperative memory change. Patients with smaller remnant volumes demonstrated more postoperative memory decline than those with larger remnants. In addition, extensive hippocampal remnant shrinkage was associated with postoperative memory decline in both the right and left temporal lobectomy groups. The absolute volume and subsequent volume loss in the hippocampal remnant following surgery can influence postoperative memory change. These findings suggest that postoperative processes should be considered in addition to preoperative pathology and surgical factors in the prediction of postoperative memory change.

In defence of small habitat islands: Termites (Isoptera) in the Western Australian central wheatbelt, and the importance of dispersal power in species occurrence

Ecological theory has long undervalued the contribution of small remnants of native vegetation to nature conservation. This study provides data on colony persistence of remnant-dependent wood-eating termites in 28 remnants of mature wandoo (Eucalyptus capillosa) trees in paddock situations in the agricultural south-west of Western Australia. Remnants ranged in size from 2 to 30 trees, and in spatial isolation from 50 to 650 m. All remnants have been exposed to livestockrelated disturbance for &gt;40 years. This study found that (1) Small remnants of eucalypt trees on farms retain important functional representatives, i.e., wood-eating termites for nutrient-cycling, and high species numbers. (2) Seventeen species have the capacity to establish and maintain colonies in remnants =5 trees. (3) Spatial isolation has no significant influence on the total number of termite species. (4) The number of trees (r = 0.60) and quantity of dead wood in the remnant (r = 0.86) were significant indicators of total termite species number. Larger remnants with low quantities of wood supported few termites, however. (5) Rare as well as common species persisted in small remnants. (6) Alate wing-size was a significant indicator of the occurrence of the six most common termite species in remnants (r = 0.84). The implication of isolation effects for rare species with limited powers of dispersal is self-evident, as is the need for the creation of habitat linkeages to reduce the effects of spatial isolation on the native fauna.

Effects of habitat fragmentation on carabid beetles: experimental evidence

1. We tested for effects of habitat fragmentation in a controlled, replicated, field experiment, in south‐eastern Australia. Our experimental subjects were eight carabid beetle species, and the carabid assemblage (45 species). Monitoring was by pitfall trapping in forest remnants and in adjacent continuous‐forest controls. Remnants were of three sizes (0·25, 0·875, 3·062 ha.). Monitoring commenced 2 years prior to habitat fragmentation. Here we present results for 6 years after habitat fragmentation (4 years for species richness). 2. We tested four hypotheses. Hypothesis one: habitat fragmentation reduces species richness in the remaining remnants. Carabid species richness was not different in habitat remnants compared to continuous forest, neither was carabid richness different for remnants of different sizes, or at monitoring sites close to remnant edges compared to sites in remnant interiors. 3. Hypothesis two: populations decline as a result of habitat fragmentation. Two species of eight were completely isolated on remnants and both declined in abundance on remnants compared to control plots in continuous forest. The other six species responded in various ways, which included relative increases and decreases in abundance and no change, but as they were not completely isolated on remnants, their responses could not be explained by isolation. 4. Hypothesis three: remaining subpopulations decline further on smaller habitat remnants than on larger remnants. Three species responded to remnant size; one was most abundant in small remnants, the second was most abundant in large remnants, and the third was equally abundant in small and large remnants and less abundant in medium‐sized remnants. 5. Hypothesis four: populations near to remnant edges decline further than populations in remnant interiors. Two species were more likely to occur in remnant interiors than at edges, whereas three species were equally likely to occur in remnant interiors and at edges. 6. The effects of habitat fragmentation may be the consequence of: (i) isolation; and (ii) habitat modification. In this study, we were able to consider effects of isolation for two carabid species. We tested only one aspect of the habitat modification hypothesis, edge effects. We discuss the possibility that other aspects of habitat modification in remnants may explain some of our results and suggest that this is where future research be directed.