The Ecology and Evolution of Social Organization in the Kangaroo Family (Macropodidae)

Approximately 45 species of kangaroos and their smaller relativesoccupy virtually every terrestrial habitat in Australia. Themost social macropod is the whiptail wallaby, which lives inpermanent, discrete mobs of up to 50 individuals of mixed ageand sex. Group formation is facilitated by their grazing habits,open forest and pasture habitat, partly diurnal activity, andlow level of intraspecific aggressiveness. Pressure from cursorialpredators, plus the whiptail's non-seasonal breeding and briefestrus, make group living adaptive. Ancestral macropods arebelieved to have been rabbit-sized inhabitants of dense forest,omnivorous, nocturnal, and essentially solitary. The major evolutionarytrends in the family have been toward larger size and grazinghabits; the trends toward diurnality and group living have hadmore modest results. Progressive stages in macropod social evolutionmay be represented by the present-day musk rat-kangaroo, thequokka, and the whiptail wallaby.     

Home range dynamics of the yellow‐footed rock‐wallaby (Petrogale xanthopus celeris) in central‐western Queensland

Analyses of the interspecific differences in macropod home range size suggest that habitat productivity exerts a greater influence on range size than does body mass. This relationship is also apparent within the rock‐wallaby genus. Lim reported that yellow‐footed rock‐wallabies (Petrogale xanthopus xanthopus) inhabiting the semi‐arid Flinders Ranges (South Australia) had a mean home range of 170 ha. While consistent with the hypothesis that species inhabiting less productive habitats will require larger ranges to fulfil their energetic requirements, the ranges reported by Lim were considerably larger than those observed for heavier sympatric macropods. The aim of the current study was to document the home range dynamics of P. x. celeris in central‐western Queensland and undertake a comparison with those reported for their southern counterparts. Wallaby movements were monitored at Idalia National Park, between winter 1992 and winter 1994. Male foraging ranges (95% fixed kernel; 15.4 ha, SD = ±7.8 ha) were found to be significantly larger than those of female wallabies (11.3 ha, SD = ±4.9 ha). Because of varying distances to the wallabies' favoured foraging ground (i.e. an adjacent herb field), the direction in which the wallabies moved to forage also significantly affected range size. Mean home range size was estimated to be 23.5 ha (SD = ±15.2 ha; 95% fixed kernel) and 67.5 ha (SD = ±22.4 ha; 100% minimum convex polygon). The discrepancy between these two estimates resulted from the exclusion of locations, from the 95% kernel estimates, when the wallabies moved to a water source 1.5 km distant from the colony site. The observed foraging and home ranges approximated those that could be expected for a macropod inhabiting the semi‐arid zone (i.e. 2.4 times larger‐than‐predicted from body mass alone). Possible reasons for the disparity between the current study and that of Lim are examined.     

Genetic inference as a method for modelling occurrence: A viable alternative to visual surveys

Management and conservation require a comprehensive understanding of species distributions and habitat requirements. Reliable species occurrence data are critical in the face of climate change and other anthropogenic activity, but are often difficult to obtain, particularly for wide ranging species. This directly affects ecological models of occurrence and habitat suitability and, in turn, conservation and management decisions. We used generalized linear mixed‐effects models to identify ecological determinants of occurrence for four macropod species (across a region of tropical northern Australia) using a non‐invasive genetic scat approach with and without additional observation records from visual surveys. We show that genetically derived occurrence data, alone, can be used to develop informative ecological models that describe the inter‐specific habitat requirements of macropods. Furthermore, we show that genetic scat surveys of macropods are cheaper and less time consuming to conduct, and tend to provide more occurrence records (and less false absences) than visual surveys. We conclude that indirect surveys using molecular approaches have an important role to play in modelling species' occurrence, and developing future management practices and guidelines to aid species conservation.     

Carbon isotope analysis shows introduced bovines have broader dietary range than the largest native herbivores in an Australian tropical savanna

Australian savannas lack native megaherbivores (>500 kg body mass), but since the commencement of European colonisation in the 19th century bovine livestock, such as cattle (Bos sp.) and water buffalo (Bubalus bubalis), have established large feral populations that continue to geographically expand. The largest extant native herbivores are marsupials in the family Macropodidae (henceforth 'macropods': common wallaroo, Osphranter robustus [c. 40 kg]; antilopine wallaroo, O. antilopinus [c. 35 kg] and agile wallaby, Notamacropus agilis [c. 20 kg]). These species occur at low densities, with evidence that some species are in decline, the cause of which remains uncertain. We tested the hypothesis that bovines and macropods compete for nutritious forage in the North Kimberley, Western Australia by using carbon isotope analysis of feral cattle and native macropod dung (as a proxy for the relative contribution of C₄ grass to their diet) and nutrient analysis of standing herbaceous biomass. Grass consumption varied between macropod species and was highest in larger wallaroo species and lowest in the smaller agile wallaby reflecting its broader diet. Grass consumption by wallaroos was maximal on fertile sites. The relative abundance of grass in the diet of cattle was lowest in the middle of the dry season with an interaction between fire and substrate fertility where grass consumption was highest on fertile sites, particularly those recently burnt. Grass consumption by cattle and wallaroos was negatively correlated with fibre content of live biomass, which was lowest on fertile and burnt sites. Introduced bovines shift their diets to non‐grasses as quality of herbaceous biomass declines with increasing fibre content, and by contrast, the largest macropod herbivores do not have this dietary flexibility. We conclude a plausible mechanism for the success of bovines and the decline of large macropods in Australian savannas is competition for nutritious grass that is abundant immediately after fire.     

Invasive African big-headed ants, Pheidole megacephala, on coral cays of the southern Great Barrier Reef: distribution and impacts on other ants

Infestation of islands by exotic ants is widespread and increasing due to human activities throughout the world. Exotic ants, particularly the invasive African big-headed ant, Pheidole megacephala (Fabricius), are of great conservation concern for coral cays at the southern end of the Great Barrier Reef, Australia. Little is known, however, about the distribution and ecological impacts of invasive ants in this insular system. We surveyed the ants of 14 vegetated coral cays recording a total of 24 ant species, including at least nine exotics. Pheidole megacephala was by far the most abundant and widespread species, occurring on 11 of 14 islands, often in very large numbers. The inter-island distribution of P. megacephala was best explained by human activities, with frequently visited, and to a lesser degree disturbed islands, more likely to be infested. On large islands (≥?10?ha) P. megacephala exhibited distinct habitat preferences, occurring in significantly lower abundances within heavily-shaded Pisonia grandis forest in the centre of islands, compared to more open, fringing woodland or shrubland. On smaller islands (<10?ha) with less extensive Pisonia stands, P. megacephala penetrated throughout the forest where its abundance was similar to that in open woodland. Despite considerable differences in biotic (floristic composition) and abiotic factors (e.g. island size) as well as the spatial configuration among islands, the severity of infestation by P. megacephala best explained variation in species richness, abundance and assemblage composition of other ants. We suggest a number of strategies to manage P. megacephala infestations on these islands.     

Sampling design may obscure species–area relationships in landscape-scale field studies

We investigated 1) the role of area per se in explaining anuran species richness on reservoir forest islands, after controlling for several confounding factors. We also assessed 2) how sampling design affects the inferential power of island species–area relationships (ISARs) aiming to 3) provide guidelines to yield reliable estimates of area-induced species losses in patchy systems. We surveyed anurans with autonomous recording units at 151 plots located on 74 islands and four continuous forest sites at the Balbina Hydroelectric Reservoir landscape, central Brazilian Amazonia. We applied semi-log ISAR models to assess the effect of sampling design on the fit and slope of species–area curves. To do so, we subsampled our surveyed islands following both a 1) stratified and 2) non-stratified random selection of 5, 10, 15, 20 and 25 islands covering 1) the full range in island size (0.45–1699 ha) and 2) only islands smaller than 100 ha, respectively. We also compiled 25 datasets from the literature to assess the generality of our findings. Island size explained ca half of the variation in species richness. The fit and slope of species–area curves were affected mainly by the range in island size considered, and to a very small extent by the number of islands surveyed. In our literature review, all datasets covering a range of patch sizes larger than 300 ha yielded a positive ISAR, whereas the number of patches alone did not affect the detection of ISARs. We conclude that 1) area per se plays a major role in explaining anuran species richness on forest islands within an Amazonian anthropogenic archipelago; 2) the inferential power of island species–area relationships is severely degraded by sub-optimal sampling designs; 3) at least 10 habitat patches spanning three orders of magnitude in size should be surveyed to yield reliable species–area estimates in patchy systems.     

Mammals of Australian islands: factors influencing species richness

Distribution patterns of indigenous non-volant terrestrial mammals on 257 Australian islands were examined in relation to environmental parameters and the effects of human-induced disturbance during prehistoric and historic times on island species numbers. Species occurrence for individual species, for taxonomic and trophic groups, and for all species together was related to environmental parameters using regression analysis and the extreme-value function model. Patterns of occurrence were examined separately within three major biogeographic regions derived by pattern analysis. The number of species known to have occurred on these islands during historic times was adequately predicted from area alone. No statistically significant improvement in predicted species number was gained by including island elevation, mean annual rainfall, isolation from the mainland or the number of potentially competing species present on the island. Similarly, no single factor other than area was found to influence consistently the presence of individual species. We conclude that the occurrence of indigenous non-volant terrestrial mammal species on these islands indicates a relictual rather than equilibrial fauna. Visitation by Aboriginal people during prehistoric times did not significantly increase mammal extinctions on islands. Examination of patterns of species richness for a given area on a regional basis showed that islands in and around Bass Strait and Tasmania (Bass Region) were the most species-rich, islands off the northern coasts were slightly less rich, and islands off the south western coasts had fewest species. This is in contrast to the usual latitudinal gradient in species richness patterns. However, islands off the northern and eastern coasts had an overall greater number of different species. When considered in relation to the number of different species of mammals occurring within each region, islands of a given size in Bass Region typically bore a higher proportion of this species pool than other regions. The Bass Region was found to be particularly rich in macropoid herbivores and dasyurid carnivores and insectivores. Analyses indicated that there is a very strong relationship between the presence of exotics as a whole and the local extinction of native mammals. Many mammal species formerly widespread on the Australian mainland are now restricted totally to islands (nine species) or are threatened with extinction on the mainland and have island populations of conservation significance (ten species). In all, thirty-five islands protect eighteen taxa of Australian threatened mammals. The land-use and management of these islands is of considerable importance to nature conservation. The introduction of exotic mammals to these islands should be prevented; any introductions that occur should be eradicated immediately.     

Island shape,size, and isolation affect nest‐site selection by Little Terns

ABSTRACT Populations of many seabirds and other species that nest along coasts are declining due to habitat degradation and loss. An improved understanding of the species‐specific factors that determine nest density across a landscape is therefore critical for conservation efforts. We examined factors that affected the density (number per hectare) and abundance (number at a sampling site) of nests of Little Terns (Sternula albifrons) on the Sinai Peninsula, Egypt. Terns preferred to nest on islands rather than the mainland, with islands constituting 64% of the area surveyed, but containing 99% of the 439 tern nests we found. Nest densities were highest on islands that were small, located at moderate distances from the mainland, and irregularly shaped or elongated. Most nests (69%) were on islands with areas < 3 ha, although these islands represented < 5% of total island area, and islands with the highest nest densities were 80–300 m from the mainland. Terrestrial predators were more likely to occur on larger islands, visiting three of the largest four islands. Most tern nests were within 1 m of shorelines, causing island perimeter to be a strong influence on nest density. Island shape was the only factor that significantly affected nest abundance, with more nests on islands with relatively long perimeters for their size. Our results suggest that protection or creation of relatively small, slender islands at moderate distances from shore may be an effective means of increasing the number of breeding sites for Little Terns. Although not generally considered a potential determinant of nest site preferences for seabirds, island shape is likely to be important for species that prefer sites adjacent to water, including species that nest on beaches and seaside cliffs.     

Distributional patterning of terrestrial herpetofauna on the Wessel and English Company Island groups,northeastern Arnhem Land,Northern Territory,Australia

Forty-four species of terrestrial reptiles and eight species of frogs were recorded from 60 continental islands of the Wessel and English Company groups off northeastern Arnhem Land, Northern Territory. Two gecko species, Oedura rhombifer and Heteronotia binoei, were present on the most islands (34 and 31, respectively), and occurred on islands < 5 ha. In contrast, agamids, pygopodids and varanids were absent from islands < 18 ha, and snakes and frogs were not reported from islands < 240 ha. Island size explained 82% of the variation in species richness for terrestrial reptiles, and 84% of that for lizards. The relationship was less good for (i) groups with generally uncommon species (notably snakes), for which sampling effort explained more variation, and (ii) groups with species which had relatively specific habitat requirements (notably frogs), for which island size and isolation factors were not especially relevant. For most taxonomic groups considered, isolation factors added little to the relationship between species richness and island size. Across all reptiles, larger species were found on fewer islands, and had larger island size thresholds. This relationship broke down with analysis restricted to the single most species-rich family, Scincidae. Only 6 of the 20 most frequently recorded species showed significant variation in abundance among 8 vegetation types sampled by 226 quadrats across 40 islands. The number of species (alpha-diversity) and total abundance of herpetofauna within quadrats was generally unrelated to island size; however, (with analysis restricted to islands on which they occurred) six individual species were significantly more abundant on smaller islands than on larger islands, with no species showing the opposite pattern. The islands’ herpetofauna is largely a relatively depauperate subset of that of the far more complex sandstone massif and escarpment of western Arnhem Land, especially missing species associated with rugged sandstone gorges, riparian areas, open forests, swamps and clay soils. Patterns in species richness and composition are explained by greater range of environments on larger islands allowing better retention of species since isolation and/or richer tallies at the time of isolation. The evidence suggests that there has been relatively little colonization, although at least two gecko species and one varanid may have moved reasonably frequently.     

Colonization of Sphagnum on land uplift islands in the Baltic Sea: time, area, distance and life history

Aim To test whether species richness of Sphagnum mosses on islands in a land uplift archipelago is related to island age, area or connectivity, and whether the frequency of different species can be predicted by their life history and autecology. Location The northern Stockholm archipelago in the Baltic Sea, east‐central Sweden, with a current land uplift rate of 4.4 mm year^?1. Methods We sampled 17 islands differing in area (0.55–55 ha), height (3.6–18 m, representing c. 800–4000 years of age) and distance from mainland (1.6–41 km). For each Sphagnum patch we measured area, height above sea level, horizontal distance from the shore and shading from vascular plants. Factors affecting island species richness, species frequency and habitats on the islands were tested by stepwise regressions. Species frequency was tested on nine life history and autecological variables, including estimated abundance and spore output on the mainland, habitat preference and distribution. Results We recorded 500 patches of 19 Sphagnum species, distributed in 83 rock pools on 14 islands. Island species richness correlated positively with island area and with degree of shelter by surrounding islands, while distance from the mainland, connectivity, height or age did not add to the model. Species frequency (number of colonized islands and rock pools) was mainly predicted by spore output on the mainland and by habitat preference (swamp forest species were more frequent than others), while spore size, for example, did not add to the model. Species differed in mean height above and horizontal distance from the shore, area of occupied rock pools and in the degree of shading of patches. The mean horizontal distance from the shore and the area of occupied rock pools correlated positively with the normal growth position above the water table among species. Spore capsules were found in only 2% of patches, mostly in the bisexual Sphagnum fimbriatum. Main conclusions The presence of Sphagnum in the Stockholm archipelago seems to be governed by regional spore production and habitat demands. Sphagnum does not appear to be dispersal limited at distances up to 40 km and time spans of centuries. Species with a high regional spore output have had a higher colonization rate, which, together with the rarity of spore capsules on the islands, indicate the mainland as a source for colonization rather than dispersal among islands. Swamp forest species seem more tolerant to the island conditions (summer droughts and some salt spray) than open mire species. The different distances from the sea occupied by the species indicate a slow, continuous succession and species replacement towards the island interior as islands are being uplifted and thus expand in area. This partly explains why larger islands harbour more species. Our results thus support some of the island biogeographical theories related to the species–area relationship.     

Community Composition and Density of Methanogens in the Foregut of the Tammar Wallaby (Macropus eugenii)

The composition of the methanogenic archaeal community in the foregut contents of Tammar wallabies (Macropus eugenii) was studied using 16S rRNA and methyl coenzyme reductase subunit A (mcrA) gene clone libraries. Methanogens belonging to the Methanobacteriales and a well-supported cluster of uncultivated archaeon sequences previously observed in the ovine and bovine rumens were found. Methanogen densities ranged from 7.0 × 10⁵ and 3.9 × 10⁶ cells per gram of wet weight.Kangaroos and wallabies belong to the marsupial family Macropodidae and are native to Australia. Because of their geographical isolation, macropod marsupials have evolved separately from other herbivorous animals, such as ruminants, but like ruminants, macropods have a complex gut microbiome that includes fungi, archaea, bacteria, and protozoa to coordinate plant biomass breakdown (11). The macropod foregut is functionally analogous to the rumen, yet for reasons unknown, macropod species produce relatively low levels of methane compared to ruminants (5, 13, 30).New species of bacteria (21) and protozoa (2-4) have been indentified in the macropod foregut, and the presence of fungi has also been reported (5). Preliminary studies have shown that methanogens are present in the kangaroo foregut (1) but can be absent or at levels below detection limits (22). This study represents the first attempt to describe the diversity of methanogens residing in the macropod foregut by using 16S rRNA and methyl coenzyme reductase A (mcrA) clone libraries in combination with quantitative real-time PCR.     

Nested distribution of amphibians in the Zhoushan archipelago, China: can selective extinction cause nested subsets of species?

Because of their poor dispersal ability, amphibians are well suited for testing the selective extinction theory on islands. Amphibian fauna in the Zhoushan archipelago, China, exhibit a high level of nestedness (C = 0.893), and the species number is lower on islands than on similar sized areas on the mainland. No correlation was found between island-specific species richness and the nearest distance from a larger island, distance from the mainland or density of human population. These results suggest that no amphibian colonisation has occurred in the archipelago since island isolation 7000–9000 years ago. Furthermore, the results imply that selective extinction contributes to the nestedness of amphibians in the Zhoushan archipelago. The incidence of a species on the islands is significantly correlated with log area of the smallest island occupied by the species and the number of provinces on the Chinese mainland in which the species occur. However, there is no correlation with average body length of adults and island occurrence. It is concluded that (1) the area of the smallest island occupied by a species is a good estimate of the minimum area for a viable population of the species and a good predictor of species incidence on islands, (2) species with a restricted distribution range are more vulnerable to extinction from islands than those with a wide distribution range and (3) the effect of body size on occurrence on the islands is uncertain, and may be specific to the archipelago and taxa studied. The observed nestedness of amphibian assemblages has two implications for conservation: (1) not only can all the species found in several small reserves be found on a large reserve of the same total size, but additional species can be found on the single large reserve; (2) for a reserve to maintain viable populations of all species in a region it should be at least as large as the smallest island occupied by the most vulnerable species. Received: 16 December 1996 / Accepted: 22 September 1997     

Short‐term response of threatened small macropods and their predators to prescribed burns in subtropical Australia

Fire is an important ecological process that shapes vegetation structure and habitat for faunal assemblages globally. Prescribed burns are increasingly being used in conservation and management to restore fire regimes in fire‐suppressed vegetation communities. Small threatened macropods require structurally complex habitat that allows them to evade detection by predators. Given that fire can alter vegetation structure, it can be viewed as a strong ecological force in shifting the dynamics between predator and prey species. Previous studies in temperate Australia have shown that prescribed burns in the presence of European Red Fox (Vulpes vulpes) and feral Cat (Felis catus) can have negative impacts on small macropods and medium‐sized mammals. Post‐fire response of threatened small macropods and their predators has not been experimentally examined in subtropical Australia despite this region providing refugia for the Long‐nosed Potoroo (Potorous tridactylus) and Red‐legged Pademelon (Thylogale stigmatica). We conducted a before‐after‐control‐impact fire experiment at two paired sites after low–moderate intensity burns typical of cool season prescribed burns. We used camera trapping to investigate changes in activity of threatened small macropods and their predators. We also recorded vegetation change. Despite large reductions in ground and shrub cover, activity of small macropods and the Dingo (Canis dingo) did not change in response to fires. Therefore, the threat of dingo predation appears to have remained unchanged following the fires. Although feral cats and foxes were present, they showed negligible activity across our sites. Our study suggests that small‐scale patchy ecological burns may not lead to increased predation of small macropods in our landscape. We attribute this to sufficient post‐fire refugia and very low densities of foxes.     

A global comparison of plant invasions on oceanic islands

Oceanic islands have long been considered to be particularly vulnerable to biotic invasions, and much research has focused on invasive plants on oceanic islands. However, findings from individual islands have rarely been compared between islands within or between biogeographic regions. We present in this study the most comprehensive, standardized dataset to date on the global distribution of invasive plant species in natural areas of oceanic islands. We compiled lists of moderate (5–25% cover) and dominant (>25% cover) invasive plant species for 30 island groups from four oceanic regions (Atlantic, Caribbean, Pacific, and Western Indian Ocean). To assess consistency of plant behaviour across island groups, we also recorded present but not invasive species in each island group.We tested the importance of different factors discussed in the literature in predicting the number of invasive plant species per island group, including island area and isolation, habitat diversity, native species diversity, and human development. Further we investigated whether particular invasive species are consistently and predictably invasive across island archipelagos or whether island-specific factors are more important than species traits in explaining the invasion success of particular species.We found in total 383 non-native spermatophyte plants that were invasive in natural areas on at least one of the 30 studied island groups, with between 3 and 74 invaders per island group. Of these invaders about 50% (181 species) were dominants or co-dominants of a habitat in at least one island group. An extrapolation from species accumulation curves across the 30 island groups indicates that the total current flora of invasive plants on oceanic islands at latitudes between c. 35°N and 35°S may eventually consist of 500–800 spermatophyte species, with 250–350 of these being dominant invaders in at least one island group. The number of invaders per island group was well predicted by a combination of human development (measured by the gross domestic product (GDP) per capita), habitat diversity (number of habitat types), island age, and oceanic region (87% of variation explained). Island area, latitude, isolation from continents, number of present, non-native species with a known invasion history, and native species richness were not retained as significant factors in the multivariate models.Among 259 invaders present in at least five island groups, only 9 species were dominant invaders in at least 50% of island groups where they were present. Most species were invasive only in one to a few island groups although they were typically present in many more island groups. Consequently, similarity between island groups was low for invader floras but considerably higher for introduced (but not necessarily invasive) species – especially in pairs of island groups that are spatially close or similar in latitude. Hence, for invasive plants of natural areas, biotic homogenization among oceanic islands may be driven by the recurrent deliberate human introduction of the same species to different islands, while post-introduction processes during establishment and spread in natural areas tend to reduce similarity in invader composition between oceanic islands. We discuss a number of possible mechanisms, including time lags, propagule pressure, local biotic and abiotic factors, invader community assembly history, and genotypic differences that may explain the inconsistent performance of particular invasive species in different island groups.     

Morphological characterisation of Australian strains of Echinococcus granulosus

Kumaratilake L. M. and Thompson R. C. A., 1984. Morphological characterisation of Australian strains of Echinococcus granulosus. International Journal for Parasitology14: 467–477. Previous studies utilising biochemical and developmental criteria demonstrated the occurrence of three distinct strains of E. granulosus in Australia. In order to further characterise these strains, we studied metacestode and adult morphology of E. granulosus of various domestic and wild animal origin from different geographical areas of Australia. Morphological comparisons included specimens from natural infections as well as experimentally-derived adult worms of known age. Three morphologically distinct populations of E. granulosus were recognised in domestic and wild animals. These populations corresponded to the three strains described previously on the basis of biochemical and developmental criteria. One strain is common to all domestic intermediate hosts on the Australian mainland, the second is confined to macropods on the mainland and the third to sheep in Tasmania. No evidence was found that domestic animals on the mainland are susceptible to the sylvatic macropod strain, whereas 15% of macropods examined were infected with the mainland domestic strain. Natural infections with both mainland strains were found in dogs and dingoes. The practical value of morphology as a criterion in taxonomic and speciation studies is discussed. Suggestions as to the probable origin of the three Australian strains of E. granulosus are given.     

Review and analysis of Australian macropod translocations 1969–2006

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Composition,structure and diversity of cove forest stands in the Great Smoky Mountains: a patch dynamics perspective

Abstract. Cove forests of the Great Smoky Mountains are North American examples of old-growth temperate forest. Ecological attributes of seven stands were studied using one 0.6 - 1.0 ha plot per stand. Stand basal area (39 - 55 m²/ha) and biomass (326 - 471 Mg/ha) were high for temperate deciduous forest. Density ranged from 577 to 1075 stems/ha. All stands had a mixture of deciduous canopy species. Only rarely did a single species comprise more than half of the stand by density, basal area or biomass. Shade-intolerant species were present at low levels (1 - 5 % of total stand density). A wide range of stem diameters was characteristic of most species. However, some species lacked small stems, indicating discontinuous regeneration. Stands tended to have 10 - 20 tree species per ha and at least five species had biomass levels > 10 Mg/ha, indicating high evenness. Canopy gaps covered 10 % of the total area (2 - 21 % by stand). Gaps and conspecific patches of canopy trees > 0.05 ha in size were infrequent. Spatial analyses revealed a variety of patterns among species at inter-tree distances of 1 to 25 m. When all species were combined, juveniles showed aggregation, and adults were often hyperdispersed. Analyses for individual species confirmed that the mosaic of canopy species is influenced by non-random spatial processes. Adults of several species were aggregated at distances > 10 m. Juveniles of all major species exhibited aggregation. Several species exhibited regeneration near conspecific adults. This pattern suggested limited mobility for such species within the shifting mosaic. A diverse patchwork resulted despite the fact that many species did not exhibit segregation of adults and juveniles. Further understanding of patch dynamics and the potential for compositional steady state in cove forests requires long-term study with spatial data.     

Biogeography of grasses (Poaceae) on islands of southwestern Australia

Abstract The number of native grass species and exotic grass species present on 129 offshore islands of southwestern Australia is best predicted by island area and island disturbance, respectively. Isolation of islands and gull activity on islands only slightly improved these predictions. Species turnover on a subset of 30 islands indicated that exotic grass species were more prone to local extinction and more likely to immigrate than native grass species. The major conservation implication of this study is that habitat disturbance on these islands should be minimized to reduce establishment of exotic grass species.     

Mapping and characterization of mangrove plant communities in Hong Kong

Ecological surveys were carried out to investigate the distribution and characterization of remaining mangrove stands in Hong Kong. The field studies indicate that 43 mangrove stands, excluding Mai Po Nature Reserve, still remained along the coastline of Hong Kong despite tremendous reclamation and development which occurred in the past 40 years. Most mangrove stands were found in Deep Bay (western part)and Sai Kung District (eastern coasts). The total areas occupied by these mangrove stands were 178 ha,varying from a very small stand (with 1–2 mangrove shrubs) to fairly extensive mangroves in Deep Bay (> 10 ha). It appeared that mangrove stands located in Deep Bay area were larger than those in the eastern coasts. Twenty plant species were identified from these stands, with 13 being exclusive or associate mangrove species. The major constituent species were Kandelia candel, Aegiceras corniculatum, Excoecaria agallocha and Avicennia marina. Rare species such as Heritiera littoralis were only found in a few mangrove stands. Out of the 43remaining mangrove stands, 23 were more worthwhile for conservation and their plant community structures were further investigated by transect and quadrat analyses. The importance values (sum of relative abundance,frequency and dominance) show that K. candel was the most dominant species. Species richness and Simpson's indices together with tree height, tree density and canopy area fluctuated significantly between mangrove stands. These values were used to prioritize the conservation potential of the remaining mangrove stands in Hong Kong. This revised version was published online in August 2006 with corrections to the Cover Date.     

千岛湖片段化栖息地地栖哺乳动物的红外相机监测及最小监测时长

作为典型的陆桥岛屿, 千岛湖成为检验栖息地片段化理论的自然研究平台。2011年5月1日至2014年3月31日, 我们在千岛湖32个岛屿和1个大陆对照样点布设了60台红外相机, 对千岛湖体型较大的地栖兽类及其最小监测时长进行了监测和研究。在27,798个相机日的监测中, 共获得动物影像照片23,639张, 照片清晰、可进行物种鉴定的有2,414张, 占照片总数的10.2%; 其中体型较大的地栖兽类独立照片988张, 识别为9个物种: 穿山甲(Manis pentadactyla)、黄麂(Muntiacus reevesi)、野猪(Sus scrofa)、华南兔(Lepus sinensis)、马来豪猪(Hystrix brachyuran)、猪獾(Arctonyx collaris)、鼬獾(Melogale moschata)、花面狸(Paguma larvata)和豹猫(Prionailurus bengalensis), 平均独立照片拍摄率为40.9%。种-面积曲线研究表明, 岛屿上的地栖兽类物种丰富度随着岛屿面积的增大而增大, 曲线的z值为0.27。大岛(>10 ha)中, 最小监测时长随面积增加而增加, 而小岛没有明显趋势; 最小监测时长随隔离度增加而减小, 但关系不显著(d.f. = 20, F = 3.067, P = 0.095), 表明建湖后栖息地的片段化与岛屿化导致了一些对面积或栖息地较为敏感的大型兽类在小岛屿上的局部灭绝。因此, 我们建议对于面积较大的片段化栖息地, 红外相机应保证较长的最小监测时长, 而面积较小的片段化栖息地在监测中应根据隔离度、基质性质、物种种类适时调整调查强度, 以完整反映当地物种实际情况。