The large Branchiopoda (Crustacea) from temporary habitats of the Drakensberg region,South Africa

The Drakensberg forms part of the Escarpment which separates the coastal plain from the inland plateau in southern Africa. This mountain range runs for about 400 km along the KwaZulu-Natal/Lesotho border and into the Eastern Cape province of South Africa. Altitude ranges from 1500 to 3000 masl. Rock pools and tarns are the main type of temporary pool habitat in the Drakensberg. 90 different habitats were sampled over a four-year period and various physical and chemical characteristics of these pools are presented. Large branchiopods occurred in 26 of these habitats. Five Branchipodopsis and two Streptocephalus species composed the anostracan fauna, while Triops granarius was collected only from the summit of the Escarpment at one locality. Four genera of Spinicaudata are represented in the Drakensberg but the current state of the taxonomy of this group does not allow identification to species level. Absence of large branchiopods from a high percentage of temporary habitats could be attributed to predation or many pools may not be sufficiently ephemeral. Most pools were inhabited by a single species of large branchiopod. This could be a result of low levels of food resources in pools, as indicated by extremely low conductivities. Restricted food resources could also be the limiting factor in the distribution of Streptocephalus and Triops which are only found in pools with higher conductivities. Four of the five Branchipodopsis species are endemic to the Drakensberg pools. These habitats are also inhabited by a high diversity of ostracods and other micro-crustaceans. Most of the KwaZulu-Natal Drakensberg falls within conservation areas but the Lesotho and Free State localities could be threatened by future development.     

A note on chironomids (diptera) of temporary pools in the National Park of Circeo,Central Italy

Preliminary observations on chironomid assemblages in 9 temporary pools of the National Park of Circeo (Central Italy) are reported. A total of 15 genera or species groups (6 Orthocladiinae, 3 Tanypodinae, 1 Tanytarsini and 5 Chironomini) were recorded during March and April, 1986.Psectrotanypus varius, Polypedilum nubeculosum gr.,Chironomus thummi gr. andC. plumosus gr. were the most abundant and frequent taxa in the nine pools. Almost all chironomids collected are eurytopic and widely distributed in Europe, including Italian waters. Only the finding ofGymnometriocnemus is reported in this paper as a new record for Central Italy. Similarity among pools and among taxa (coefficient of Jaccard) shows a major occurrence of aquatic Orthocladiinae in smaller pools and of Chironomini in larger pools. This relationship between chironomid assemblages and pool sizes can be partly related to the duration of the wet phase which affects chironomid species according to their survival strategies.     

Urban rain pools: seasonal dynamics and entomofauna in a park of Buenos Aires

We describe the seasonal variations of the insect community of the rain pools in a park of Buenos Aires during a 1-year period, based on a weekly sampling programme. We also analyse the relationships between the observed biotic patterns and some physical and meteorological variables. Four periods, fairly coincident with the seasons of the year, were graphically identified as functions of temperature, rainfall, flooded area, number of rain pools, depth and taxonomic richness. A total of 45 insect taxa was identified: 18 Coleoptera, 15 Diptera, 9 Heteroptera, 1 Ephemeroptera and 2 Odonata. Culicidae represented 76% of the pooled abundance of insects, probably related to their rapid development before the pools dry up. Taxonomic richness was maximum at the end of the summer (32), in coincidence with maximum rainfalls and temperatures. Inversely, the minimum richness (2) was recorded during the spring drought. Richness was positively correlated to the flooded area and to the number of pools on each sampling date. The species recorded throughout the study period were: Aedes albifasciatus, Culex eduardoi, Culex pipiens, Liodessus sp., Rhantus signatus signatus, Tropisternus setiger, Tropisternus lateralis limbatus and Sigara platensis. Some of the species recorded are considered pioneer in temporary habitats. Both coleopterans and heteropterans are likely to persist in the park through repeated colonisation from more permanent habitats. Habitat duration and flooded area were positively correlated to richness in each one of the rain pools.     

Freshwater rock pools: a review of habitat characteristics,faunal diversity and conservation value

1. In the light of the recent surge of interest in small and often temporary wetlands as model systems for ecological and evolutionary research, this article reviews current knowledge on freshwater rock pools and their fauna. 2. Freshwater rock pools occur all over the globe in all major biomes and depend mainly on precipitation for filling. Rock pool clusters are some of the more persistent and oldest freshwater habitats worldwide. Interactions between climate and geology (e.g. limestone, sandstone, granite) generally determine the morphology and hydrology of rock pool habitats, with hydroperiods ranging from several days up to the whole year. Pool volume is usually small, resulting in strongly fluctuating environmental conditions, low conductivity and wide variations in pH (from 4.0 to 11.0) and temperature (from freezing point to 40 °C) often with well‐marked diel cycles. The highly variable environmental conditions, combined with the unpredictability of the flooding regime, require high stress tolerance of the inhabitants, with adaptations for surviving the dry phase such as the production of resistant stages and active emigration followed by recolonisation. 3. About 460 aquatic animal species have been recorded from freshwater rock pools around the world. Approximately 170 of these are passive dispersers, which mainly disperse as resting stages via wind and overflow of water between pools. Successful long distance dispersal seems limited. This group is composed mainly of rock pool specialists with a high degree of endemicity. The remaining taxa can be considered active dispersers, with migration usually restricted to the adult stage. Often these taxa are broadly distributed and occur in a wide range of temporary habitats in addition to rock pools. 4. The inherent characteristics of freshwater rock pools, such as their simple structure and occurrence on similar substrata all over the world, facilitate comparison of research results and promote rock pools as model systems for ecological and evolutionary research. Nevertheless, despite their potential as model systems, the unique fauna and their importance as sources of freshwater in dry countries, the ecology of freshwater rock pools remain virtually unexplored in large parts of the world.     

Habitat distribution and body size in rain-pool dwellers

Rain-pools differ from oceanic islands, essentially, in being ephemeral. Ability to disperse and reproduce is therefore a special priority among inhabitants.
Pupal exuviae of a principal inhabitant, Chironomus imicola , were collected from pools in tropical Africa. Length of pupal skin is positively related both to flight duration and ovule number in adult chironomids. Hence length of pupal skin can be related to fitness in this temporary pool dweller.
Predictably, therefore, remote pools are inhabited by large individuals while those in clusters have more small forms.
That duration of the habitat also influences body size is demonstrated by Polypedilum vanderplanki. These larvae are able to survive dry periods and therefore experience the habitat as permanent. In contrast to C. imicola, P. vanderplanki responds to isolation with a disproportionate number of small flies.
In addition to these differences in average size, variance in body size is affected by isolation of the habitat. Comparison with progeny of a single female shows increased variability to be determined not only by habitat location but also to be an inherent characteristic of animals perceiving the habitats as ephemeral.     

Survival strategies in tropical rain pools

Summary Adaptations of three larval diptera in central Africa, each inhabiting rain-filled rock pools of characteristic duration, have been studied by field observation and experiment.The duration of the pool is important in determining which of the three species is present. Large pools, lasting a few weeks after each rain, favour Chironomus imicola which has a larval life span of as little as twelve days. This species relies on egg laying female flies to re-invade newly filled pools. In cases where the pool lasts for a shorter time than the minimum larval life span a mechanism is needed to survive dry periods in situ. Such pools are inhabited by larvae of Polypedilum vanderplanki and Dasyhelea thompsoni. Larvae of P. vanderplanki are poor at invading newly flooded pools and are also poor at competing with other species. However they are able to tolerate virtually a complete loss of body water and are therefore able to survive drought in the dry mud. They are consequently always the first there after refilling, a factor that provides them with sufficient advantage to eventually become established in very small pools. D. thompsoni larvae, not quite so good at surviving drought, but better at invading, occupy pools of intermediate size. They probably inhabit a larger number of pools than either of the other two species.A hazard associated with surviving dry phases in situ is vulverability to attack by terrestrial scavengers. However the activity of scavengers such as pheidolid ants, although conspicuous, is confined to periods when standing water has evaporated but the mud is still moist. Once dry, predation stops. Losses from this cause are therefore likely to be associated with periodic dry phases throughout the rainy season rather than with the dry season itself.     

Resilience of anostracan cysts to fire

California's Mediterranean ecosystems include shrubland and grassland vegetation types that are fire-prone. Dotted within this landscape are ephemeral wetlands called vernal pools. Since surrounding upland vegetation is adapted to survive fire, it is expected that vernal pool organisms should be able to survive as well. One group of animals common to vernal pools are anostracan crustaceans that survive the pool's dry period as encysted embryos. We hydrated anostracan cysts from the soil of a recently burned pool and from soil samples intentionally burned in a prescribed fire. We also sampled burned pools when refilled the next rainy season. We found that anostracan cysts in the soil can survive fire and that shrimp occur in pools in the first post-burn season. This information is important from a management perspective concerning fire effects, controlled or natural, on vernal pools and their rare and endangered species. This revised version was published online in August 2006 with corrections to the Cover Date.     

Community structure in temporary freshwater pools: disentangling the effects of habitat size and hydroregime

1. Hydroregime (duration, frequency and predictability of the aquatic phase) is a key feature of temporary aquatic habitats that not only moulds community structure and diversity (species sorting) but also life history characteristics of the inhabitants (natural selection). However, since hydroregime is a complex multidimensional entity that cannot be estimated from short term observations, morphometric variables are commonly used as proxies for hydroregime, making it impossible to separate effects of habitat size and hydroregime on biota.
2. We have used a simple hydrological model, validated with recent (average r ² = 96%) and historic water level observations (average r ² = 81%), to accurately reconstruct hydroregime based on historical rainfall and evaporation data in a cluster of 36 temporary rock pools in central South Africa.
3. Using the model output, we demonstrated that both hydroregime and habitat size had unique and shared effects on temporary pool biota and that these effects depended on the dispersal modes of the taxa. Model-generated hydrological data explained more variation in community patterns than short-term observations of hydroperiod. Hydroregime was more important for passive dispersers than for active dispersers that can migrate when pools dry up. Basin morphometry was a relatively poor predictor of pool hydroregime. We concluded that simple modelling may greatly improve the resolution of studies linking hydroregime to biological variables.
4. An accurate account of hydrological variation provides a firm foundation to understand community and population structure and dynamics in temporary aquatic habitats. Since many of these habitats have been destroyed or degraded in recent decades, our findings and tools may contribute to the development of reliable conservation guidelines.     

Species richness and the proportion of predatory animal species in temporary freshwater pools: relationships with habitat size and permanence

The proportion of predatory animal species is often believed not to vary systematically across communities. However, we predict that larger temporary freshwater pools, and pools that are more permanent, will contain a higher proportion of predatory animal species. In 24 temporary rockpools in Northern Israel (supporting communities dominated by ostracods, copepods, cladocerans, flatworms, dipterans and amphibians), the mean proportion of macroscopic predatory species (averaged over a series of samples) increased with increasing pool area. For the highest possible proportion of predatory species (including microscopic species with uncertain diets), the relationship with pool area was not statistically significant. We did not find significant relationships between permanence and the proportion of either macroscopic or all possible predatory species. Larger pools and pools that were more permanent had more species. Species richness and the proportion of macroscopic predators were positively correlated. These patterns imply that species-poor ecosystems are likely to be functionally different from species-rich systems.     

Pathways for algal recolonization in seasonally‐flowing streams

1. In semi‐arid climates, seasonally‐flowing streams provide most of the water required for human use, but knowledge of how water extraction affects ecological processes is limited. Predicted alterations in stream flows associated with the impacts of climate change further emphasize the need to understand these processes. Benthic algae are an important base for stream food webs, but we have little knowledge of how algae survive dry periods or respond to altered flow regimes. 2. We sampled 19 streams within the Grampians National Park, south‐eastern Australia and included four components: a survey of different drought refuges (e.g. permanent pools, dry biofilm on stones and dry leaf packs) and associated algal taxa; a survey of algal regrowth on stones after flows recommenced to determine which refuges contributed to regrowth; reciprocal transplant experiments to determine the relative importance of algal drift and regrowth from dry biofilm in recolonization; direct measurement of algal drift to determine taxonomic composition in relation to benthic assemblage composition. 3. Algae showed little specificity for drought refuges but did depend on them; no species were found that were not present in at least one of the perennial pool, dry biofilm or leaf pack refuges. Perennial pools were most closely correlated with the composition of algal assemblages once flows resumed, but the loss or gain of perennial pools that might arise from stream regulation is unlikely to affect the composition of algal regrowth. However, regulated streams were associated with strong increases in algal density in dry biofilm, including increased densities of Cyanobacteria. 4. A model for algal recolonization in seasonally‐flowing streams identified three pathways for algal recolonization (drift‐dependent, dry biofilm‐dependent and contributions from both), depending on whether streams are diatom‐dominated or dominated by filamentous algae. The model predicted the effects of changes to stream flow regimes on benthic algal recolonization and provides a basis for hypotheses testable in streams elsewhere.     

Distribution of aquatic macroinvertebrates within peatland pool complexes in the Flow Country, Scotland

Stationary water traps were used to sample the aquatic invertebrates from both shallow, drought-sensitive pools and deeper, more permanent pools on blanket bog in the Flow Country, northern Scotland during 1994–1995, an area important for nature conservation. The differences in numbers of invertebrates trapped, and the differences in species composition and abundance of adult aquatic Coleoptera and Hemiptera (the two most abundant groups caught) between these two pool types, and spatially within the deeper pools, were investigated. Using the same trapping effort, seven times more invertebrates and five times more adult Coleoptera were taken in the deep (A4) pools compared to the shallow (A3) pools, and Hemiptera were almost exclusively trapped in the A4 pools (only 2% of the catch was from A3 pools). DECORANA showed that the Coleoptera species composition of the two pool types was different, although a small overlap existed, presumably because of the proximity of the pool types and of the continuous nature of the variation between them. There was little difference in the numbers taken or species composition of Coleoptera or Hemiptera from the edges or centre of the A4 pools. Smaller Coleoptera species were found in both pool types, although one species was more common in the centre of the larger pools. Larger Coleoptera with a body length of more than 11.6 mm were not found in the A3 pools, only in the deeper A4 type. The A4 pools were found to be more stable seasonally than the shallow pools with respect to invertebrate numbers trapped, and this may be linked to the chance of drying out of the latter in dry periods. The influence of pool stability (through water level) on invertebrate abundance, development and individual species size is discussed, as is the sampling method used, the significance of the peatland fauna and its importance to breeding bird life associated with peatland pool complexes. This revised version was published online in July 2006 with corrections to the Cover Date.     

Associations of Chironomidae (Diptera) of shallow,acid, humic lakes and bog pools in Atlantic Canada,and a comparison with an earlier paleoecological investigation

The composition of benthos in a series of 29 lake and peat pool sites is examined especially in relation to a successional gradient. The results indicate a sharp distinction between the fauna of peat pools and lakes. Chironomus, Psectrocladius, Monopsectrocladius, and Zalutschia are characteristic of bog lakes at the latter stages of their evolution and peat pools. Procladius and Tanytarsus dominate in most lakes. Between weakly acidic and strongly acidic lakes a sharp boundary exists for many other components of the benthos. Chaoborus occurs in strongly acidic lakes. Amphipoda, and Ephemeroptera are limited to weakly acidic or circum-neutral waters.A comparison of the results of this investigation with a parallel paleoecological study is made.     

Microclimate,developmental plasticity and community structure in artificial temporary pools

Solar radiation, which influences temperature and hydroperiod, should strongly influence colonization, development rate, development strategies and survival in temporary pools. We assessed these hypotheses at two spatial microscales with varying microclimate. One scale, ca. 200 m, was opposing slopes of a canyon on MT Carmel, Israel, referred to as 'Evolution Canyon' (Nevo, 1995). Due primarily to differential solar radiation, the warmer and drier South-facing slope (SFS) supports a savanna-like open park forest while the cooler, moister North-facing slope (NFS) is heavily forested, primarily with live oak. Using artificial pools, we assessed how these close but contrasting environments may influence developmental plasticity in the frog, Hyla savignyi, and colonization of insects. As expected, hydroperiod was considerably longer on the NFS. Hyla tadpole development was significantly faster on the SFS, while size at metamorphosis was greater on the NFS. Insect species richness was higher in NFS pools. The most common species, Culex pipiens, oviposited significantly more in NFS pools than in SFS pools. In the second scale, we placed pools only meters apart, but varying in shade and thus maximum temperature at Haifa University Campus, MT Carmel. Species richness and maximum temperature among pools were not correlated during winter and early spring (cool to mild temperatures), but were strongly and negatively correlated during early summer (hot temperatures). Thermal tolerance in the laboratory of selected species matched their thermal spatial distribution in the field. These results indicate that temperature can play a strong role in affecting developmental strategies, species′ distributions and community structure in temporary pools over a very small spatial scale. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analytical studies of the ultrastructure and movement of the spermatozoa of freshwater triclads

Fourteen phyllopod (Branchiopoda: Crustacea) species were collected from numerous temporary pools in north-eastern Natal, South Africa. Physical and chemical data for 10 pools, and results for hourly (over 41 hours) and 3-day interval (throughout periods when phyllopods were present) monitoring of 3 study pools are presented. Comparisons were made with other pools with phyllopods in Africa. The data reveal the broad tolerance to variation and extremes in both physical and chemical conditions in African temporary waterbodies. Species diversity appears to be related to pool size and vegetation. Phyllopod distribution does not follow a pattern associated with physical and chemical conditions.     

The ecology and mechanisms of overflow‐mediated dispersal in a rock‐pool metacommunity

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Flying with the birds? Recent large-area dispersal of four Australian Limnadopsis species (Crustacea: Branchiopoda: Spinicaudata)

Temporary water bodies are important freshwater habitats in the arid zone of Australia. They harbor a distinct fauna and provide important feeding and breeding grounds for water birds. This paper assesses, on the basis of haplotype networks, analyses of molecular variation and relaxed molecular clock divergence time estimates, the phylogeographic history, and population structure of four common temporary water species of the Australian endemic clam shrimp taxon Limnadopsis in eastern and central Australia (an area of >1,350,000 km(2)). Mitochondrial cytochrome c oxidase subunit I sequences of 413 individuals and a subset of 63 nuclear internal transcribed spacer 2 sequences were analyzed. Genetic differentiation was observed between populations inhabiting southeastern and central Australia and those inhabiting the northern Lake Eyre Basin and Western Australia. However, over large parts of the study area and across river drainage systems in southeastern and central Australia (the Murray-Darling Basin, Bulloo River, and southern Lake Eyre Basin), no evidence of population subdivision was observed in any of the four Limnadopsis species. This indicates recent gene flow across an area of ～800,000 km(2). This finding contrasts with patterns observed in other Australian arid zone taxa, particularly freshwater species, whose populations are often structured according to drainage systems. The lack of genetic differentiation within the area in question may be linked to the huge number of highly nomadic water birds that potentially disperse the resting eggs of Limnadopsis among temporary water bodies. Genetically undifferentiated populations on a large geographic scale contrast starkly with findings for many other large branchiopods in other parts of the world, where pronounced genetic structure is often observed even in populations inhabiting pools separated by a few kilometers. Due to its divergent genetic lineages (up to 5.6% uncorrected p-distance) and the relaxed molecular clock divergence time estimates obtained, Limnadopsis parvispinus is assumed to have inhabited the Murray-Darling Basin continuously since the mid-Pliocene (～4 million years ago). This means that suitable temporary water bodies would have existed in this area throughout the wet-dry cycles of the Pleistocene.     

Oviposition habitat selection by the mosquito Culiseta longiareolata in response to risk of predation and conspecific larval density

Abstract. 1. Most female Culiseta longiareolata (Diptera: Culicidae) avoid ovipositing in pools that contain the predatory backswimmer Notonecta maculata . Such oviposition habitat selection has been suggested to reflect a trade-off between the risk of predation on larvae and potential density-dependent fitness costs. This putative trade-off was examined. In particular, evidence was sought in support of direct female response to local heterogeneity in habitat quality.
2. Three habitat types were established using artificial outdoor pools: predator pools, and non-predator pools with either low or high densities of Culiseta larvae. During each experimental night, females were offered one of the three possible pair-wise treatment combinations.
3. The majority (≈88%) of females oviposited in low-density pools rather than in the predator- or high-density pools. Furthermore, a substantially higher proportion of females oviposited in predator pools when faced with the high-density alternative, however this was due largely to fewer females ovipositing in high- vs low-density pools.
4. Females of a second mosquito species ( Culex laticinctus ), the larvae of which are at a lower risk of predation, were predicted to exhibit weaker aversion to N. maculata ; this prediction was supported only weakly.
5. Oviposition habitat selection by female C. longiareolata does not appear to involve a behavioural response that is based on individual assessment of local heterogeneity in relative pool quality, at least not at the spatial scale examined here; alternative explanations are discussed.     

Life history adaptations of phyllopods in response to predators,vegetation, and habitat duration in north-eastern Natal

Phyllopod populations were monitored in three temporary pools differing in the amount of submerged, peripheral vegetation present, surface area and duration. The effects of these factors on the life history strategies employed by phyllopods were investigated. Triops granarius, various conchostracan species and the anostracan Branchipodopsis sp. inhabited the periphery of two pools where rooted, submerged vegetation was abundant while three Streptocephalus species dominated the central, unvegetated regions of the pools and the unvegetated pool. This distribution pattern appeared to be related to the animals' morphology and feeding habits. The peripheral regions of the pools were stressful habitats since they were colonized by large numbers of predators and competitors 30–40 days after inundation and they dried out sooner than the centre. The peripheral species exhibited typical r-selected life history strategies; they grew rapidly, reproduced early and had short lifespans and in this way they overcame the threats presented by their habitat. The central species took advantage of their predator-free, more stable habitat and exhibited life history patterns which tended towards the K-end of the r-K continuum. A degree of intraspecific variation in growth and reproduction was obvious and appeared to be related to differences in habitat duration of the three pools.     

Chemically-mediated interactions in benthic organisms: the chemical ecology of Crambe crambe (Porifera,Poecilosclerida)

Five temporary forest pools at Noxubee National WildlifeRefuge,Noxubee Co., Mississippi were surveyed monthly for three yearstogain a better understanding of the dynamics of temporaryaquatichabitats. The objective of this study was to characterize thephysicochemical and biological changes in temporary pools inorderto assess the temporal habitat diversity. These ecosystems,allwithin no more than 4 km of one another, were heterotrophicwith adetrital-based food web derived from allochthonous leaflitter.These pools were chosen because of their close proximity tooneanother, they historically filled and dried seasonally, andtheywere known breeding sites for resident amphibian populations.Only47% of the amphibian cohorts inhabiting the pools appeared tothrive and metamorphose prior to pool desiccation. Successfuldevelopment and dispersal of larvae was variable among poolsandyears. We found that the filling cycles differed amonghabitats andthat physiochemical and biological parameters were highlyvariable.Our data suggest that ephemeral pools in this central piedmontregion of Mississippi are each unique and represent habitatsof lowpredictability for amphibian breeding and success. We concludethatit is erroneous to draw generalizations regarding a typicaltemporary pool ecosystem within this region.     

Life cycle, growth and diet of Balston's pygmy perch in its natural habitat of acidic pools in south-western Australia

Nannatherina balstoni is found in a few acidic pools (pH 3.9–6.0) in the extreme south-western corner of Australia. Although many of these pools become dry during summer and early autumn, they are recolonized by fish from nearby pools that overflow during winter floods. N. balstoni spawns at the end of its first year of life, when, on average, the males and females have reached 60 and 63 mm t.l ., respectively, and then usually die within the next few months. The largest fish, which was one of only three in its third year of life, measured 90 mm and weighed 7.3 g. The von Bertalanffy growth curve parameters for L₀, K and t₀ were 71.2 mm, 1.69 and – 0.078 for males and 82.6 mm, 1.31 and – 0.095 for females. Fecundity ranged from 550 to 1600. N. balstoni. spawns during the middle of winter, after heavy flooding and when water temperatures are at, or close to, their annual minima. This enables the larvae and young juveniles to capitalize on those aquatic organisms, especially Cladocera, which are very abundant amongst the flooded riparian vegetation that surrounds the pools in winter and spring. Hence, the fish grow rapidly and attain an appreciable size before summer, when the increases that occur in the densities of the larger carnivorous fish species, as a result of marked declines in water levels, increases the chances of predation. By spring, when most N. balstoni exceed 25 mm t .l ., the diet changes markedly to one that consists almost exclusively of terrestrial fauna. In contrast, three of the six co-occurring native species of teleost feed on aquatic and terrestrial fauna throughout the year, while a further two feed only within the water column and the sixth feeds on benthic invertebrates. The pronounced shift in diet exhibited by N. balstoni as it increases in size, allied to dietary differences amongst the other six co-occurring species, reduces any potential for interspecific competition for food resources during the summer and autumn, when such resources are declining.