Benthic assemblages,biodiversity and invasiveness in marinas and commercial harbours: an investigation using a bioindicator group

Fouling communities on artificial marine structures are generally different from benthic communities in natural rocky habitats. However, they may also differ among different types of artificial structures. Two artificial structures in direct contact with arriving vessels were compared: floating pontoons within recreational marinas, and sea-walls within commercial harbours. Natural rocky habitats were used as a reference, and the genus Eudendrium (Cnidaria, Hydrozoa) was chosen as a bioindicator. The assemblages were different among the three types of habitat studied, with different species characterising each habitat. The probability of finding an invasive Eudendrium species was significantly higher on pontoons. Diversity was the lowest on pontoons, but it was not significantly different between sea-walls and natural rocks. In general, a barrier to the spread of exotic species exists between harbours and natural rocky habitats. Floating pontoons seem to be a less suitable habitat for native fauna and a key element in marine biological invasions.     

Herbivore control in connected seascapes: habitat determines when population regulation occurs in the life history of a key herbivore

Herbivore outbreaks often trigger catastrophic overgrazing events in marine macrophyte ecosystems. The sea urchin Paracentrotus lividus, the dominant herbivore of shallow Mediterranean seascapes, is capable of precipitating shifts to barrens when its populations explode. Paracentrotus lividus is found ubiquitously in rocky macroalgal communities and in sandy seagrass meadows of Posidonia oceanica, two of the most important subtidal habitats in the Mediterranean. We explored if habitat‐specific regulation across the principal stages of the urchin life cycle could help explain the persistence of these populations in connected mosaics. We measured each of three relevant ecological processes (i.e. settlement, post‐settlement survival and predation) across a wide stretch of the Mediterranean coast (ca 600 km). Our results show that habitat‐specific regulation is critical in determining urchin populations: each habitat limited urchin sub‐populations at different life stages. Settlement was never limiting; urchins settled at similar rates in both habitats across the coast. Post‐settlement survival was a clear bottleneck, particularly in seagrass meadows where no juvenile urchins were recorded. Despite this bottleneck in seagrasses, adult urchin populations were very similar in both seagrass and macroalgal habitats indicating that other processes (potentially migration) could be key in determining adult distributions across the mosaic. The fact that population regulation is clearly habitat‐specific suggests that sea urchin populations may be significantly buffered from bottlenecks in mixed seascapes where both habitats co‐occur. Sea urchin populations can therefore persist across the seascape despite strong habitat‐specific regulation either by maintaining reproductive output in one habitat or by migrating between them. By affording these regulatory escapes to habitat‐modifying species, patchy mosaics may be much more prone to herbivore outbreaks and a host of cascading effects that come in their wake.     

Identifying key habitats for the conservation of Bonelli's Eagle Aquila fasciata using radiotracking

Identifying the priority habitats of endangered species is crucial to implementing effective conservation actions. We characterize the key habitats used by Bonelli's Eagle Aquila fasciata, an umbrella and flagship species that is endangered in Mediterranean countries. We radiotracked 17 breeding individuals (10 males and seven females) in Catalonia (NE Iberian Peninsula) and used compositional analysis to determine the key habitats in home‐ranges of both sexes. The main habitats identified within the home‐range area were scrubland, coniferous forests, cropland, sclerophyllous forests, rock outcrops and urban areas, with little difference in habitat use between the sexes. Bonelli's Eagles preferred rocky habitats as breeding areas and scrubland as foraging areas, as these hold the highest abundance of their main prey, Rabbits Oryctolagus cuniculus and Red‐legged Partridges Alectoris rufa. Habitat selection varied seasonally in foraging areas: scrubland was the most preferred habitat type during the breeding season, whereas rocky areas were preferred during the non‐breeding season (although scrubland was also highly selected). Urban areas were avoided both as breeding and as foraging areas. Home‐range size was inversely correlated with the proportion of scrubland, suggesting that this is a key habitat for Bonelli's Eagle. To conserve this species effectively, policies that ensure the preservation of the cliffs used as breeding sites, as well as suitable management of the scrubland used for foraging, should be implemented in the areas inhabited by this species. The promotion of traditional land uses and management techniques that will enhance open areas in Mediterranean landscapes should in the future play an essential role in the conservation of Bonelli's Eagle in Mediterranean habitats.     

Breeding phenology and larval distribution of amphibians in a Mediterranean pond network with unpredictable hydrology

Understanding spatial and temporal breeding patterns in Mediterranean amphibian communities is urgent considering the rate of habitat loss. Breeding phenology and breeding habitat selection by amphibians were analysed through the monthly occurrence of larvae in a mosaic of 198 Mediterranean temporary ponds during three years. A generalized linear model (GLM) coupled with principal component analysis showed that, for almost all species, occurrence was significantly positively correlated to pond depth. In addition, pond openness negatively affected the presence of some species. Temporal breeding patterns varied among species. Some species exhibited flexibility in their breeding date (Pelobates cultripes, Pelodytes punctatus, Hyla meridionalis, Rana perezi), while others did not (Triturus marmoratus, Triturus helveticus, Bufo calamita). When faced with inter-annual hydrological variability, the first group had a more constant breeding success than the second. Variable hydrological conditions caused differential larval occurrence of species between years. These fluctuations might favour long-term persistence of the whole amphibian community. We finally discuss the implications of our results for the management of amphibian habitats in the Mediterranean region.     

Habitat matters – Strong genetic and epigenetic differentiation in Linum catharticum from dry and wet grasslands

Plant species differ in their ecological amplitude, with some species occurring in very different habitats under strongly differentiated environmental conditions. We were interested in to what extent the occurrence of Linum catharticum in dry calcareous grasslands (Bromion) and wet litter meadows (Molinion), two habitats on opposing ends concerning, for example, moisture level, is reflected on the genetic and epigenetic level. Using AFLP (amplified fragment length polymorphisms) and MSAP (methylation sensitive amplification polymorphisms) analyses, we studied the genetic and epigenetic variation of L. catharticum from calcareous grasslands and litter meadows. From each habitat, we included five study sites with 16 individuals per sampling location. We observed lower genetic than epigenetic diversity, but considerable differentiation among habitats, which was stronger on the genetic than the epigenetic level. Additionally, we observed a strong correlation of genetic and epigenetic distance, irrespective of geographic distance. The dataset included a large portion of fragments exclusively found in individuals from one or the other habitat. Some epigenetic fragments even occurred in different methylation states depending on the habitat. We conclude that environmental effects act on both the genetic and epigenetic level, producing the clear differentiation among plant individuals from calcareous grasslands and litter meadows. These results may also point into the direction of ecotype formation in this species.     

马鞍列岛多种生境中鱼类群聚的昼夜变化

为了解岛礁水域鱼类群聚的昼夜变化特征,以便更全面地设计采样方法和掌握采样的时间尺度,于2009年9月对马鞍列岛7种生境进行了共计24网次的刺网昼夜采样,结合排序和聚类方法,从种类组成、相对生物量和丰度、种类丰富度、多样性和相似性等方面对研究海域鱼类群聚特征的昼夜变化作了探讨.在采获的55种鱼类中,昼夜出现的分别为41和46种,数量差别不大,但其昼夜组成却随栖息水层的变化而不同,底层鱼类更趋向于夜间在硬相生境集群活动;近底层鱼类的昼夜集群随生境变化而变化,在同一生境中既有偏向白天也有趋向夜间的;中上层鱼类更多地出现在白天的人工生境(AH).AH白天的丰度渔获率显著大于晚上,而天然生境(NH)昼夜差别不大;生物量渔获率无论NH还是AH皆无显著昼夜差异.具体到种类,仅有小黄鱼Larimichthys polyactis和赤鼻棱鳗Thryssa kammalensis等少数种类的数量在AH有显著的昼夜差别,其他多数种类虽然昼夜的出现率大多有别,但渔获率昼夜差异皆不明显.多样性差异更多的表现在不同生境之间,而同一生境的昼夜差异往往不甚显著.各个生境中鱼类的昼夜种类交替现象非常明显,形成了以褐菖(鲐)Sebastiscus marmoratus和鳗鲇Plotosus anguillaris为代表的夜间优势类群为主的硬相生境群聚格局、以丝背细鳞鲀Stephanolepis cirrhifer和细刺鱼Microcanthus strigatus为代表的白天优势类群为主的硬相生境群聚格局以及缺乏底层优势类群、以石首鱼科鱼类为代表的近底层鱼类为绝对优势类群的软相生境群聚格局.因此,采用被动性渔具在近岸典型生境进行鱼类等相关生物调查时,应使采样时间覆盖昼夜两个时段,且至少保证24h.     

Using Artificial Rocks to Restore Nonrenewable Shelter Sites in Human‐Degraded Systems: Colonization by Fauna

Many animals spend much of their time within retreat sites underneath loose surface rocks and may be highly selective in terms of the physical characteristics of the sites that they use. If such shelters are eliminated by anthropogenic activities, such as rock removal for landscaping, the only way to restore these nonrenewable habitats may be to replace them with artificial rocks. To construct artificial rock habitats, we need to understand which rock attributes are important for faunal use and develop methods to mimic these important natural retreat site characteristics. Based on our prior understanding of rocky retreat sites used by reptiles in sandstone outcrops of southeastern Australia, we constructed realistic‐looking artificial rocks from fiber‐reinforced cement and evaluated (1) the degree to which they mimicked natural retreat sites in both thermal regime and three‐dimensional crevice structure and (2) their colonization by fauna after deployment in the field. Our results demonstrate that thermal regimes and crevice structures beneath the artificial rocks were similar to those beneath natural rocks. In addition, 100% of the artificial rocks were colonized (by 45 invertebrate, six lizard, and two snake species, including the endangered Broad‐headed snake, Hoplocephalus bungaroides) after only 40 weeks. Together, these results suggest that restoring degraded habitats for rock‐dwelling species is feasible and can provide a rapid means of enhancing shelter‐site availability for such species.     

Effects of environmental factors on the ecology and survival of a widespread,endemic Cerrado frog

Understanding the mechanisms that affect habitat use by vertebrates is critical for understanding how species are distributed across landscapes and how they cope with habitat change. The Brazilian Savanna (the Cerrado) has vegetation ranging from grassland to woodland savannas and harbors a rich and diverse amphibian fauna impacted by accelerated habitat loss. Here, we test the influence of vegetation type (from grassy scrubland to woodland) and distance from breeding sites (ephemeral water bodies) on body size, abundance, and survival of the frog Physalaemus nattereri in a natural metapopulation system of south-central Brazil. We also test whether body size is a significant predictor of population abundance. We found that the abundance of P. nattereri varies according to the mean snout–vent length of each metapopulation (sampling unit), as well as a higher estimated mortality rate in woodlands compared with typical Cerrado. Furthermore, we found no difference in estimated mortality among sampling units located far or close to ephemeral water bodies. Thus, our results highlight variable responses of P. nattereri metapopulations to environmental factors, despite the observed high heterogeneity among sampled habitats and the importance of ephemeral water bodies for reproduction. These findings highlight that land cover and availability of breeding sites might not always interact to explain population persistence of Cerrado frogs.     

Analysis of macrofungal communities reveals a complex reciprocal influence between Mediterranean montane calcareous grassland and surrounding forest habitats

Fungi are essential components of all terrestrial ecosystems. Despite the crucial ecological role of soil fungi in grasslands, knowledge about fungal community diversity and structure in Mediterranean meadow habitats is still fragmentary. We analyzed macrofungal communities in three geographically distinct Mediterranean montane calcareous grasslands and surrounding forests, by means of fruit body surveys. We investigated a number of biotic and abiotic factors influencing the studied fungal communities, including plant species composition. Out of 6365 fruit bodies, a total of 268 species belonging to 84 genera were found. In general, there was a significant correlation between plant species richness and fungal richness. Variation in vegetation and plant community structure accounted for approximately 20% of variance in fungal community structure. Tree and shrub vegetation played a dominant role in shaping the analyzed fungal communities, both in meadows and surrounding forests, with particular influence on ectomycorrhizal, litter, and lignicolous saprotrophic fungi. Fungal biodiversity in the studied meadows was increased by the presence of tree and shrub species from the adjacent forests, but was reduced by the increasing vegetation cover.     

石漠化生境对三叶木通生长及生理特性的影响

石漠化生境土层浅薄、干旱贫瘠,许多植物难以生存。三叶木通作为石漠化生境适生物种之一,探究其对石漠化生境的应答机制对综合治理石漠化生境具有一定的理论和实际意义。在贵州省贵阳市花溪区和安顺市关岭县两地分别选取石漠化生境和普通生境(对照)种植三叶木通,并进行为期一年的观察,探究石漠化生境对三叶木通根、茎、叶等不同器官的生长和生理特性的影响,并利用主成分分析出三叶木通在石漠化生境的主要响应指标。结果显示,与对照相比,石漠化生境下的三叶木通表现出如下特征：(1)植株较矮、茎较细、叶片数较少等生物量的减少,使其适应石漠化生境;(2)叶片叶绿素a/b (Chla/b)和相对含水量(RWC)呈现降低趋势,从而使叶片净光合速率(Pn)、蒸腾速率(Tr)、气孔导度(Gs)和水分利用率(WUE)均呈下降趋势,胞间CO₂浓度(Ci)呈升高趋势,利于适应石漠化生境;(3)丙二醛(MDA)含量和叶片相对电导率(RC)呈现升高趋势,说明石漠化生境对三叶木通细胞膜系统造成损伤(氧化损伤和渗透损伤),而通过其根中过氧化氢酶(CAT)、茎中过氧化物酶(POD)和叶片中超氧化物歧化酶(SOD)活性升高...     

Importance of secondary habitats and need for ecological management for the conservation of Diphasiastrum tristachyum (Lycopodiaceae, Pteridophyta) in the Vosges Mountains (France)

Diphasiastrum tristachyum, which is a rare Pteridophyte under national protection in France, has been discovered in several places in the Vosges Mountains during the last two decades. With its 20 currently existing populations in these mountains, it appears to be the Diphasiastrum species with the largest current distribution in the Vosges. This species mainly occurs on Vosgian sandstone substrate, in northern or northeastern exposures up to 600 m a.s.l., corresponding to the lower and middle montane levels in the Vosges Mountains. The main habitat (16 sites) are forest track borders. Only in single cases could D. tristachyum be found in other habitats such as a skiing track, a heath submitted to regular fire, an abandoned quarry and a limit of a forest plantation weeded with herbicides. All of these sites are secondary places of young anthropic origin. No really natural and primary habitats of D. tristachyum in the Vosges Mountains could be found. All localities show fragments or beginnings of heath communities belonging to the Genistion alliance. Because of the progressive succession of these communities towards forests if no human regulation occurs, D. tristachyum may have only ephemeral existence in such secondary Vosgian sites. This shows the need for a conservation and management programme which comprises measures like keeping open growing sites by the removal of invading trees, controlled pruning of dwarf shrubs and removal of the soil vegetation and the humus layer. A long-term stabilisation of the Vosgian populations of D. tristachyum may only be possible in this way.     

Environmental and vegetation variables have a greater influence than habitat fragmentation in structuring lizard communities in remnant urban bushland

Abstract The expansion of urban areas and adjacent farming land into natural landscapes modifies habitats and produces small isolated pockets of native vegetation. This fragmentation of the natural habitat subdivides animal communities, reduces population sizes and increases vulnerability to extinction. In this paper we investigate whether fragmentation decreases lizard species richness, composition, overall abundance and abundance at the species level. Urban remnants consisting of five small (< 10 ha) and four large (> 10 ha) fragments of natural bushland were paired with continuous bushland areas located near Hobart, Tasmania, Australia. These remnants were surveyed six times, using pitfall traps, from November 2001 to March 2002. Lizard species richness and abundance were not significantly influenced by habitat fragmentation or fragment size. Egernia whitii was the only lizard species significantly influenced by fragment size, and was only present in large fragments and continuous bush. Vegetation type and structure as well as environmental variables (geology and aspect) influenced the structure of reptile communities. Lizard species that were able to use a number of different habitat types were found to persist at most sites, irrespective of fragment size. Edge environment did not significantly influence lizard species richness or abundance in remnant areas. Lizard species richness was significantly lower in sites that had a high ratio of exotic to native plant species. Therefore, if remnants continue to be invaded by exotic plants, lizard species that require native plant communities will become increasingly vulnerable to local extinction. Our results suggest that lizard species requiring specialized habitats, such as E. whitii, may persist in large urban remnants rather than small urban remnants because large reserves are more likely to encompass rare habitats, such as rocky outcrops. Habitat heterogeneity, rather than size, may be the key to their persistence.     

Persistence of a rare aquatic species along gradients of disturbance and sediment richness

Abstract. This study examines the capacity of establishment of a rare aquatic macrophyte, Luronium natans, within plant communities and habitat types in which it does not occur spontaneously. The species, generally limited to disturbed or nutrient‐poor habitats, was transplanted into a series of sites situated along natural gradients of disturbance (flush‐floods and intermittent sediment exposure) and sediment nutrient‐richness. The transplanted colonies were given a competition‐free establishment period. Colony dynamics of Luronium as well as size structure of the recolonizing macrophyte communities were monitored over three growing seasons. At the end of this period, transplanted colonies still persisted in five out of 12 transplantation sites. Apparently successful integration into the community occurred at both ends of the nutrient gradient, in periodically disturbed habitats. At intermediate to high nutrient richness Luronium maintained one of the highest cover values within the recolonizing community. The study supports previous presumptions that long‐term persistence of Luronium depends on processes limiting community biomass through occurrence of disturbance. But it also reveals the existence of suitable, yet not occupied habitats in which the species can persist as successfully as species from the local species pool. This finding modulates the presumption that Luronium's rarity is mainly caused by a weak competitive ability in the established phase. It thus rises questions about the species’ performance at other stages of its life cycle and on its dispersability.     

Habitat preferences and habitat restoration options for small‐bodied and juvenile fish species in the northern Murray–Darling Basin

Degradation of instream habitats in the northern Murray–Darling Basin has occurred through numerous stressors, including siltation, clearing of bankside vegetation, intrusion of livestock and impacts of pest species. A better understanding of habitat preferences of native fish species could help guide future instream habitat restoration actions. The habitat choices of seven native fish species, juvenile Murray Cod (Maccullochella peelii), juvenile Golden Perch (Macquaria ambigua ambigua), juvenile Silver Perch (Bidyanus bidyanus), adult Murray–Darling Rainbowfish (Melanotaenia fluviatilis), adult Olive Perchlet (Ambassis agassizii), adult Un‐specked Hardyhead (Craterocephalus stercusmuscarum fulvus) and adult carp gudgeons (Hypseleotris spp.) were tested in preference troughs to help inform potential habitat restoration actions in the Condamine catchment. Each species was given a choice between pair combinations of open sandy habitat, submerged macrophytes, emergent plants and rocky rubble. Habitat preferences varied between species. Murray Cod, Golden Perch, carp gudgeons and Olive Perchlets preferred structure over open sandy habitat, whilst juvenile Silver Perch, Un‐specked Hardyhead and Murray–Darling Rainbowfish did not avoid open sandy habitats. Juvenile Murray Cod preferred rocky rubble habitat over all other habitat choices. Use of complex rock piles to provide nursery habitat for Murray Cod populations is a potential restoration option. Introduction of rock could also benefit Golden Perch and carp gudgeons. Use of emergent plants, submerged macrophytes and rocky rubble for habitat restoration all appear to have merit for one or more species of small‐bodied fishes or juvenile stages of larger sized fishes. Rocky rubble or floating attached macrophytes could be viable restoration options in areas too turbid to establish submerged macrophytes. These habitat interventions would complement existing actions such as re‐snagging and provision of fish passage to assist with sustainable management of native fish populations.     

Ecological interactions in the provision of habitat by urban development: whelks and engineering by oysters on artificial seawalls

Abstract Increases in human population cause increased urbanization of most habitats, including the shoreline. This has many consequences for coastal environments, in particular the trend for artificial structures, such as seawalls, to replace natural habitats. Seawalls and natural shores support many of the common intertidal species, but others important on rocky shores are absent from or rare on many seawalls. The whelk Morula marginalba Blainville is an abundant and important predator on rocky shores of south‐eastern Australia, but is infrequently recorded on artificial substrata. In Sydney Harbour, where the Sydney rock oyster (Saccostrea glomerata Gould) was locally abundant, densities of M. marginalba on some seawalls appeared to be similar to those on rocky shores and to be larger than where there were few oysters. We sampled densities and sizes of whelks in four habitats, predicting and corroborating that: (i) on seawalls with many oysters, there would be more whelks than on seawalls with few oysters; (ii) where there are many oysters, densities of whelks would be similar on seawalls and rocky shores; and (iii) whelks would be larger where oysters were abundant. Growth and survival of whelks were measured to test hypotheses from the observed differences in size and density. Survival was greater in habitats with many oysters, which could explain differences in density, but size‐specific differences in survival could not explain differences in size among habitats. On seawalls but not on rocky shores, slower growth could explain the smaller size of whelks where there were few oysters. Seawalls provide important habitat for M. marginalba, but only via their indirect effects, mediated by oysters. These interactions cannot be predicted from those on natural rocky shores. Predicting how developed areas provide suitable habitat, either in management of conservation or in assessments of potential impacts clearly depends on understanding the roles of biogenic habitats.     

Successional phases and species replacements in freshwater rock pools: towards a biological definition of ephemeral systems

1. In temporary aquatic habitats, time is probably the dominant environmental factor affecting community composition, mainly by setting constraints on colonization success and the replacement of taxa over time. The mechanism and effect of a decreasing inundation period on community development, mostly in terms of truncation, are still poorly documented. The permanent and ephemeral components of temporary communities are expected to be differently influenced by the degree of persistence of the habitat. 2. To study the effect of time on invertebrate community assembly and dynamics in a short duration type of temporary aquatic habitat, we monitored 16 ephemeral rock pools which persisted from less than a week to about 1 month at two rock pool sites in semi‐arid south‐eastern Botswana. Data were collected every 2 days during a full inundation cycle. 3. All communities were initially assembled by permanent residents recolonizing the habitat from egg banks and were later joined by actively dispersing ephemeral taxa. Species replacements only occurred in two pools. Concurrent with a decrease in the densities of Branchipodopsis wolfi, population sizes of Leberis sp. and Culicidae (Aedes sp. and Anopheles sp.) increased in these pools. Although it was possible to distinguish two successive phases at one rock pool site, community assembly was generally a gradual process determined by dispersal strategies of the inhabitants. Additional rains after initial filling triggered dispersal by ephemeral taxa, mainly Micronecta youngiana and Hydroglyphus infirmus, and positively influenced colonization success. 4. Decreasing persistence shortens community development down to a critical point below which lack of time eliminates the possibility of species replacement. Based on these findings, we define ephemeral waters as aquatic habitats lacking species replacements. Other temporary water types have a relatively longer persistence, permitting successional replacement of species.     

Population Structure, Mobility and Habitat Preferences of the Violet Copper Lycaena Helle (Lepidoptera: Lycaenidae) in Western Germany: Implications for Conservation

We describe population structure, mobility and habitat preferences of the butterfly Lycaena helle using a survey of the populations in the Westerwald area (Western Germany) and mark-recapture techniques. Three out of 83 recorded populations were intensively studied in 1995. In all, 1596 individuals (537 females) were uniquely marked. The average adult residence time was 8 days, the maximum 34 days. L. helle is extremely sedentary. Average distances between first and subsequent captures were 37 and 61 meters for males and females respectively. Population-specific differences are interpreted as being caused by the influence of barriers and corridors. The potential for colonization is regarded as poor, and isolated populations seem to be under a higher risk of extinction than other ones. Preferred habitats were abandoned moist meadows with rich aspects of Polygonum bistorta on sheltered, warm, and humid stands. Owing to the destruction of natural habitats (moorland) L. helle now colonizes almost exclusively anthropogenic ephemeral habitats (abandoned moist meadows) in Central Europe. This results in serious conservation problems, as the biology of the species does not seem to be adapted to a high turn-over rate of habitats.     

Limiting factors of Striped Hyaena,Hyaena hyaena,distribution and densities across climatic and geographical gradients (Mammalia: Carnivora)

Few previous studies on the factors that affect Striped Hyaena (Hyaena hyaena Linnaeus, 1758) occurrence and densities were done on geographically unrelated populations using different methodologies. In Israel, hyaenas occur throughout the country's steep climatic and geographical gradients, presenting a unique opportunity to study densities and habitat use across adjacent ecosystems using a unified methodology and test previous conceptions regarding the species’ habitat selection. We collected hyaena abundance-absence data using 1440 camera traps placed at 80 sites (2012– 2016). Site location ranged from hyper-arid deserts to dense Mediterranean shrubland. We assessed the effect of climate, habitat structure, elevation, geomorphological attributes (proxy for den availability), and anthropogenic development (proximity to settlements and agriculture) on hyaena densities using N-mixture models. Hyaena densities were negatively affected by anthropogenic development, and were limited by den availability. Hyaena densities did not follow a climatic or geographic gradient. Densities were highest at hyper-arid deserts and Mediterranean coastal shrublands. Despite the former conception that hyaenas prefer semi-arid open habitats and avoid extreme deserts and dense vegetation, we show that hyaenas use and even thrive in these habitats when geomorphological conditions are suitable and resources are available.     

The influence of habitat structure and flow permanence on macroinvertebrate assemblages in temporary rivers in northwestern Zimbabwe

Temporary rivers within the Nyaodza-Gachegache subcatchment in northwestern Zimbabwe were investigated to examine the role of flow permanence and habitat structure on macroinvertebrate community composition. Macroinvertebrate communities of intermittent and ephemeral rivers displayed significant differences in the number of taxa, macroinvertebrate abundance, Shannon and Simpson diversity indices and in size class structure. Intermittent sites were characterised by higher numbers of taxa, diversity and Ephemeroptera and Trichoptera richness compared to ephemeral sites. The fauna of ephemeral sites was dominated by a single taxon (Afrobaetodes) (Ephemeroptera, Baetidae) whilst larger sized taxa (e.g. Elassoneuria (Ephemeroptera, Oligoneuriidae), Dicentroptilum (Ephemeroptera, Baetidae), Aethaloptera (Trichoptera, Hydropsychidae), Pseudagrion (Odonata, Coenagrionidae) and Tholymis (Odonata, Libellulidae) were exclusively restricted to intermittent sites. Clear differences were observed between sand, gravel, cobble and vegetation habitats. Vegetation and cobbles supported distinct communities, with some taxa exclusively restricted either to vegetation (e.g. Pseudagrion, Leptocerina (Trichoptera, Leptoceridae), Cloeon (Ephemeroptera, Baetidae), Afronurus (Ephemeroptera, Heptageniidae) and Povilla (Ephemeroptera, Polymitarcidae) or cobble (e.g. Aethaloptera and Dicentroptilum) habitats. In terms of ensuring optimum diversity within the subcatchment, we consider conservation of critical habitats (cobbles and vegetation) and maintenance of natural flows as the appropriate management actions. Handling editor: D. Dudgeon     

The Structures and Dynamics of Fish Communities in an Okinawan Coral Reef: Effects of Coral-based Habitat Structures at Sites with Rocky and Sandy Sea Bottoms

Although there have been many studies on ecological factors responsible for the organization of reef fish communities, most of the studies have focused on isolated habitats. However, findings from isolated habitats cannot necessarily be applied to fish communities in other habitats (e.g., a continuous habitat). In this study, therefore, we examined the structures of fish communities (abundance, species richness and species composition), and the dynamics of fish communities (seasonal changes in abundance, species richness and species composition) over a 2-year period in two different habitats (continuous habitat and isolated habitat) in an Okinawan coral reef. We established eight permanent quadrats (8m × 8m) on a rocky reef flat (continuous habitat) and rock reef patches surrounded by a sandy sea bottom (isolated habitat). The abundance and species richness of fishes such as pomacentrids, labrids, chaetodontids and acanthurids were greater in quadrats located in the continuous habitat, whereas those of blenniids, gobiids and mullids were greater in quadrats located in the isolated habitat. This caused marked differences between the fish community structure at the two sites. Seasonal and annual changes in fish community structure were relatively small at the continuous habitat site (>0.7 similarity based on C index) but were large at the isolated habitat site (C < 0.4), indicating that the fish community structure was relatively stable at the continuous habitat site but unstable at the isolated habitat site throughout the study period. Spatial differences between the fish community structures in the four quadrats at the continuous habitat site were small (C > 0.65 in most sites), but these differences were large at the isolated habitat site (C < 0.4). Our findings suggest that habitat structure (spatial arrangement of habitats) affects both spatial and seasonal differences in the reef fish community structure. The results also suggest that the main mechanisms underlying organization of reef fish communities in continuous and isolated habitats are different.