Frequency Distribution Of Species Research Articles

Accounting for differences in species frequency distributions when calculating beta diversity in the fossil record

Abstract Beta diversity is a measure of the taxonomic differentiation between habitats/localities within an assemblage, and is normally calculated as a set of pairwise taxonomic “distances” between the localities. Due to incomplete sampling, beta diversity estimates for fossil assemblages will always be higher than the true value. However, the difference between the observed and true distances will vary greatly depending on differences in the shape of the relative abundance distribution. Using simulations, it is shown that incomplete sampling of a homogenous fauna with more even relative abundances of taxa produces higher beta diversity than one with very few extremely common taxa. A new procedure is proposed for calculating beta diversity in the fossil record, whereby the observed distances are compared to the distance obtained by randomly resampling a homogenous fauna with the same abundance distribution. This procedure is named Relative Abundance Corrected beta diversity. Simulations indicate that this method outperforms raw beta diversity estimates, providing beta diversity estimates closer to the true values even when the assumptions of the method are violated. This method is applied to an empirical dataset: Permian–Triassic tetrapods from the Karoo Supergroup of South Africa. Increased provincialism is found across the Permian–Triassic boundary in contrast to uncorrected beta diversity patterns.

Annual variation of species richness and lorica oral diameter characteristics of tintinnids in a semi-enclosed bay of western Pacific

Much has been written on annual variation of tintinnid assemblages although the mechanism causing the annual variation has been poorly studied either in form of species richness or Lorica Oral Diameter (LOD) size-classes. In the present study, a 10-year (May 2003 to December 2012) survey on species occurrence, abundance, and LOD variation of the tintinnid ciliates was conducted in Jiaozhou Bay, western Pacific. In contrast to previous studies, we found summer peaks in tintinnid species richness in Jiaozhou Bay validated by multi-year investigations. We studied phenology of every tintinnid species and explored the mechanism causing the annual variation. The hypothesis was that tintinnid species richness has a winter baseline, to which warm water species added with the progress of the season. We defined the occurrence types of each species, and found there was only one cold occurrence type species. There was no overlap of cold occurrence type and warm occurrence type in the transitional period between winter and summer. The second aim of this study was to explore annual variations in tintinnid assemblages in form of LOD and redundant species. The species frequency distribution patterns among LOD size-classes were similar all year round. The abundance frequency distribution pattern in LOD size-classes could be divided into two phases: cold phase and warm phase with exception of May and September. The portion of redundant species was about 50% in every month. Our result help understand and predict annual variation of tintinnid assemblages in terms of species richness and LOD in world oceans.

Zoonotic and Molecular Aspects of Listeria Species Isolated From Some Farm Animals at Dakahlia Province in Egypt.

This study was performed in Dakahlia province, Egypt to investigate zoonotic and molecular aspects of Listeria species recovered from some farm animals and human. For this purpose, a total of 272 samples were collected from animals (146), milk (60) and man (66). Of which 146 fecal samples were collected from cattle (95), buffaloes (25), sheep (16) and goats (10). Meantime, 60 milk samples were taken from cattle (27), buffaloes (3) and sheep (30). Regarding human, 66 samples were included 54 stool samples from 30 adult, 9 previously aborted women and 15 preterm. Moreover, 12 vaginal swabs were collected from aborted women from patients admitted to Mansoura University hospitals and some private clinical laboratories. The results revealed that the occurrence of Listeria species was 17.1% in animal feces, 16.6% in milk samples. While, in human samples, it was 15.1%. Sheep feces showed higher occurrence (43.7%), buffalo’s milk was highest contamination rate (33.3%). The frequency distribution of Listeria species in stool of women, preterm, adults and vaginal swabs were 11.1%, 6.6%, 20.0% and 16.6%, respectively. Different Listeria species have been identified from animals, milk and humans, L. monocytogenes was the most identified strains (44.4%). Multiplex polymerase chain reaction (m. PCR) was used to detect the virulence genes (iap, hylA and actA) of 12 biochemically identified L. monocytogenes strains recovered from different sources using specific primers. The molecular characterization proved that m. PCR successfully amplified iap, hylA and actA virulence genes at specific base pair 131, 456 and 839 respectively. In conclusion, Listeria species were detected in the examined farm animals, its milk and humans, reflecting the zoonotic impact of such animals and its milk, moreover, same genotypes prevalent in farm animals, milk and humans suggesting that genotypes are transmissible between farm animals and man in the examined area, Egypt.

Floristic composition and vegetation: Environmental relationships of Wadi Fatimah, Mecca, Saudi Arabia

ABSTRACTThe present study aimed to determine floristic composition, the structure of the vegetation, and species distribution at 16 sample plots in Wadi Fatimah, Mecca, Saudi Arabia, highlighting the ecological factors that affect species distribution. The study revealed 100 plant species belonging to 34 families. Fabaceae and Poaceae were the dominant families, and chamaephytes and therophytes were predominant life forms, which demonstrate a typical desert life-form spectrum. Altitude showed a highly significant association with species frequency distribution. The highest species richness value of 23 species per plot was recorded in the coastal plain (Vegetation groups II & III). The lowest species richness value of 9 species per plot was recorded in the littoral salt marsh (Vegetation group I). Chorological analysis exhibited the Saharao-Arabian–Sudano-Zambezian chorotypes, 47% of the studied species were bi-regional. Using TWINSPAN, DCA, and CCA multivariate analysis, four major vegetation groups were classified into three main ecosystems (I) Halopeplis perfoliata, Suaeda fruticosa, Acacia tortilis, and Suaeda fruticosa, representing the littoral salt marsh; (II) Rhazya stricta and Haloxylon salicornicum, characterized by the coastal plain; and (III) Senna italica, Glinus lotoides, and Tribulus macropterus were the leading groups in the inland mountainous country. The CCA ordination showed that the separation of Vegetation group III along the axis was affected by Mg, K, and P concentration, and VG IV was significantly associated with silt, clay, and fine sand content. Furthermore, the Vegetation group I was significantly correlated with Na and Ca concentration, and VG II group was significantly correlated with heavy metal concentrations of elements as Fe, Pb, Zn, Ni, and Cu.

Measuring the change under compositional data analysis (CoDA): Insight on the dynamics of geochemical systems

Geochemical systems are complex and the analysis of the shape of the frequency distribution of elements and chemical species often informs about the variability and dispersion related to the underlying dynamics. However, when compositional data are used it is incorrect to investigate concentrations in the Euclidean space. Distribution analysis is aimed at focusing on real coordinates, which can be obtained by applying some appropriate log-ratio transformation. In particular, distributional analysis for compositional data can be applied to isometric coordinates, called balances, obtained through partition of a multi-element data set. As an alternative the same investigation can be performed on indices such as the robust Mahalanobis distance after having ranked log-ratio compositions with respect to some reference composition (i.e. average Earth crust) and having obtained a sort of “measure of change”. By considering this second new perspective, the chemical composition of topsoils of the Campania Region (Southern Italy) was investigated by analysing the concentrations of Al, As, B, Ba, Ca, Co, Cr, Cu, Fe, K, La, Mg, Mn, Mo, Na, Ni, P, Pb, Sr, Th, Ti, V and Zn, in mg/kg, determined on >3500 samples. Results reveal the presence of complex processes governed by interaction-dominant dynamics where self-organisation appears to play some role.

Deer‐mediated changes in environment compound the direct impacts of herbivory on understorey plant communities

Summary In forests of eastern North America, white‐tailed deer (Odocoileus virginianus) can directly affect, via herbivory, the presence, abundance and reproductive success of many plant species. In addition, deer indirectly influence understorey communities by altering environmental conditions. To examine how deer indirectly influence understorey plants via environmental modification, we sampled vegetation and environmental variables in‐ and outside deer exclosures (10–20 years old) located in temperate forests in northern Wisconsin and the Upper Peninsula of Michigan, USA. We assessed how excluding deer affected understorey community composition and structure, the soil and light environment, and relationships between direct and indirect effects, using non‐metric multidimensional scaling (NMDS), mixed linear models and nonparametric multiplicative regression (NPMR). Excluding deer altered sapling communities and several aspects of the understorey environment. Excluding deer from plots with lower overstory basal area increased sapling abundance, decreasing the amount of light available to groundlayer plants. Exclusion also reduced soil compaction and the thickness of the soil E horizon. The composition of understorey communities covaried in apparent response to the environmental factors affected by exclusion. In several common species and groups, E horizon thickness, compaction, openness, and/or total (sapling and overstory) basal area were significant predictors of plant frequency. Complementary analyses revealed that deer exclusion also altered the frequency distributions of several species and groups across environmental space. Synthesis. Deer alter many facets of the understorey environment, such as light availability, soil compaction and thickness of the soil E horizon, which, in turn, appear to mediate variation in plant communities. Those environmental modifications likely compound direct impacts of herbivory as drivers of understorey community change. Our results provide evidence that deer effects on the environment have important implications for forest composition. Thus, we suggest a re‐examination of the common assumption that understorey community shifts stem primarily from tissue removal.

The relative contributions of rare and common species to the patterns of species richness in plant communities

Understanding how overall patterns of spatial variation in species richness are affected by species distributional is one of the key questions in species diversity research. In the present study, we investigated the relative contributions of common and rare species to overall plant species richness in the Liaodong oak (Quercus wutaishanica) forest, which is located in the Ziwu Mountains of Loess Plateau, northwestern China. Based on species frequency distribution, we developed rank sequences of the most common to the most rare and the most rare to the most common species. We then correlated the rank sequences with cumulative species distributions. Our results showed that common species had a higher correlation with the cumulative species distribution in comparison with rare species. Moreover, common species had stronger effects on species α diversity and species β diversity as compared with rare species. Although the number of rare species was greater than that of common species, the overall species richness pattern was better predicted by common species than rare species. Therefore, common species were confirmed to be good indicators of species richness pattern and need to be protected priority.

Body sizes and diversification rates of lizards, snakes, amphisbaenians and the tuatara

AbstractAimSize is one of the most important and obvious traits of an organism. Both small and large sizes have adaptive advantages and disadvantages. Body size–frequency distributions of most large clades are unimodal and right skewed. Species larger than the mean or range midpoint of body sizes are relatively scarce. Theoretical models suggest evolutionary rates are higher in small organisms with short generation times. Therefore diversification rates are usually thought to be maximal at relatively small body sizes. Empirical studies of the rates of molecular evolution and clade diversification, however, have usually indicated that both are unrelated to body size. Furthermore, it has been claimed that because snakes are longer than lizards, the size–frequency distribution of all squamate species is bimodal overall. We examined the shape of the size–frequency distribution of nearly all Squamata and Rhynchocephalia species, and investigated how size affected diversification rates.LocationGlobal.MethodsWe collected data on maximum body length for 9805 lepidosaur (squamates and the tuatara) species (99.7% of all species) and converted them to mass using clade‐specific allometric equations. Using methods that test for relationships between continuous traits and speciation and extinction rates on a large, dated phylogeny (4155 species), we investigated the relationship between diversification rates and body size.ResultsLiving squamates span six orders of magnitude in body size, eight when giant extinct snakes and mosasaurs are included. The body size–frequency distributions of snakes and lizards separately, and of all lepidosaur species combined, are unimodal and right skewed. Nonetheless, we find neither linear nor hump‐shaped relationships between size and diversification rates, except in snakes, where speciation and diversification are hump shaped.Main conclusions Despite a clear modality and skew in the body sizes of lepidosaurs, we find little evidence for faster diversification of modal‐sized taxa, perhaps implying that larger‐sized clades are relatively young.

Mineral Species Frequency Distribution Conforms to a Large Number of Rare Events Model: Prediction of Earth’s Missing Minerals

A population model is introduced to describe the mineral species frequency distribution. Mineral species coupled with their localities conform to a large number of rare events (LNRE) distribution: 100 common mineral species occur at more than 1,000 localities, whereas $$34 \,\%$$ of the approved 4,831 mineral species are found at only one or two localities. LNRE models formulated in terms of a structural type distribution allow the estimation of Earth’s undiscovered mineralogical diversity and the prediction of the percentage of observed mineral species that would differ if Earth’s history were replayed.

Statistical analysis of the phytocoenose homogeneity. II. Species frequency distribution and frequency distribution of the standing biomass as a function of the area size

Homogeneity of the <em>Leucobryo-Pineium</em> phytocoenose was assessed on the grounds of the species frequency distribution and frequency distributions of the total ground-layer biomass and those of individual species. It was confirmed that: 1) species frequency distribution and frequency distribution of biomass, as well as their statistical characteristics depended on the area size and 2) for analysed phytocoenose the area at which frequency distributions of both measures were symmetrical could be determined. The studies showed that phytocoenose homogeneity was related only to the definite area size, i.e. to the definite scale of its spatial differentiation.

Species frequency distribution as a function of the surface area

Paper deals with the results of statistical analysis of the type of frequency distribution of species occuring in the field layers of two forest phytocoenoses. In the both cases frequency distributions were ranged out for the surface area of 1, 2, 4, 8, 16, 32 and 64 m<sup>2</sup>. The types of frequency distributions were determined on the grounds of the values of Fisher's and Pearson's K coefficients. Analysed distributions were classified into Pearson's system. Also the size of the sample plot at which the empirical frequency distributions were symetrical, from the statistical point of view, nad where they were U-shaped was determined.

The Role of Spatial Aggregation in Forensic Entomology: Table 1.

A central concept in forensic entomology is that arthropod succession on carrion is predictable and can be used to estimate the postmortem interval (PMI) of human remains. However, most studies have reported significant variation in successional patterns, particularly among replicate carcasses, which has complicated estimates of PMIs. Several forensic entomology researchers have proposed that further integration of ecological and evolutionary theory in forensic entomology could help advance the application of succession data for producing PMI estimates. The purpose of this essay is to draw attention to the role of spatial aggregation of arthropods among carrion resources as a potentially important aspect to consider for understanding and predicting the assembly of arthropods on carrion over time. We review ecological literature related to spatial aggregation of arthropods among patchy and ephemeral resources, such as carrion, and when possible integrate these results with published forensic literature. We show that spatial aggregation of arthropods across resources is commonly reported and has been used to provide fundamental insight for understanding regional and local patterns of arthropod diversity and coexistence. Moreover, two suggestions are made for conducting future research. First, because intraspecific aggregation affects species frequency distributions across carcasses, data from replicate carcasses should not be combined, but rather statistically quantified to generate occurrence probabilities. Second, we identify a need for studies that tease apart the degree to which community assembly on carrion is spatially versus temporally structured, which will aid in developing mechanistic hypotheses on the ecological factors shaping community assembly on carcasses.

Quantifying the woody component of savanna vegetation along a density gradient in the Kalahari Bushveld: a comparison of two adapted point-centered quarter methods

Bush encroachment is a serious problem in savanna rangelands of southern Africa. There is a strong interest in practical and reliable assessment methods to quantify related vegetation changes in the woody layer such as the widely applied point-centred quarter (PCQ) methods. Several variations of these distance methods exist but their results differ due to differences in sampling effort and methodological accuracy. The aim of this study was to compare the performance of two recently developed adapted PCQ methods. These methods were used to estimate density, productivity and diversity of the woody layer of a semiarid savanna along a degradation gradient in the Kalahari rangelands. It was found that both adapted PCQ methods (APCQ10 and APCQ20, with the APCQ20 method using less recording points but a larger sampling area and higher sampling intensity per recording point) provided similar results for density, phytomass, available browse and browsing capacity in open, dense and encroached savanna types. Significant differences between the methods were obtained in differentiating height classes, which were, however, largely restricted to the woody layer above 2 m in open savanna types. There, applying the APCQ20 method avoided an under-sampling of larger shrubs and trees and increased precision in data assessment. This was confirmed by a better representation of species frequency distributions, as well as the density, phytomass and diversity status of the woody layer. These differences disappeared as the woody vegetation became denser with the APCQ10 method providing similar results to that of the APCQ20 method in densely vegetated and encroached savanna types. From a practical point of view, the APCQ10 method has a range of advantages in dense vegetation, where restricted movement impedes effective data collection. It is concluded that the APCQ20 method should be used to quantify open savanna communities, whereas the APCQ10 method is more suitable in dense stands of >1200 tree equivalents ha–1. Overall, the two APCQ methods were effective for assessing and monitoring woody savanna layers for management purposes but, for research, their accuracy still needs to be investigated in comparison to other assessment methods.

Island biogeography of tropical alpine floras

AbstractAimWe analysed the effects of alpine area, geographical distance between mountains and isolation due to topography on mountain plant species richness, regional species turnover and patterns of species distribution.LocationEquatorial mountains of East Africa, South America and New Guinea.MethodsWe collated lists of alpine species and estimated the extent of alpine area for seven mountains in each geographical region to construct species–area curves. We tested the observed frequency distribution of species among mountains against the expected distribution (assuming random dispersal) by means of a log‐likelihood test. We compared species turnover among mountains using species accumulation curves. We expressed floristic similarity between mountain pairs as chi‐square distance between observed and expected numbers of shared species and tested its correlation with geographical distance using the Mantel test.ResultsSamples of East African, South American and New Guinean alpine floras contained 371, 489 and 279 species, respectively. Andean genera tended to be more species rich than genera in the other regions. Species richness of the mountains correlated with log‐transformed area except in East Africa. Species distributions among mountains significantly deviated from random in all regions. Species turnover was lowest among East African sites and highest among South American sites, and the slopes of the cumulative species–area relationship were significantly different. Floristic similarity between mountains significantly declined with log(distance) in all regions, and the slope of the relationship was steepest in South America.Main conclusionsThe flora of the Andean páramo is confirmed to be the most species rich of the tropical alpine regions. Páramo genera tend to be richer in species than afroalpine and tropicalpine Asian genera. There is higher species turnover in the Andes and the floras of individual mountains are therefore quite distinct. In contrast, the floras of the East African mountains are more uniform and possess a relatively large number of widespread species.

A breath test to assign carnivore diets to browsers or grazers

Cheetahs Acinonyx jubatus are important predators of herbivores in African ecosystems, and several methods to determine their diet have been used in the past. We applied a novel method to quickly assess the diet of cheetahs with respect to grazing and browsing herbivores, i.e. we analysed the stable carbon isotope ratio (δ13CV‐PDB) of cheetah breath to separate individuals feeding predominantly on browsers or grazers, respectively. Browsers and grazers are contrasting in their muscle δ13CV‐PDB, because of their isotopically distinct C3 or C4 plant diet, respectively. Muscle δ13CV‐PDB of six abundant local potential prey species of cheetahs confirmed that kudu Tragelaphus strepsiceros and springbok Antidorcas marsupialis browsed on C3 plants, whereas gemsbok Oryx gazella, hartebeest Alcelaphus buselaphus, warthog Phacochoerus africanus and cattle Bos taurus predominantly grazed on C4 plants. Breath δ13CV‐PDB of the cheetahs followed the bimodal frequency distribution of the prey species with six cheetahs being assigned to the C4 food web and three to the C3 food web. Breath tests may be a suitable method to delineate the trophic membership of carnivores to C3 and C4 food webs when animals are chemically immobilised for other purposes.

Are diatom diversity indices reliable monitoring metrics?

A biological survey was carried out in 640 stations spread over the Loire-Bretagne National Network (France) between 1996 and 2000. Epilithic diatom inventories were obtained following standard methods. A total of 934 diatom taxa were identified. Common diversity indices (species richness, Shannon’s diversity, equitability, dominance, etc.) were calculated and compared against abiotic factors verify their reliability as biomonitoring metrics. Sampling stations were classified according to their trophic status (TP concentration). Several theoretical predictions about the relationship between community structural parameters and limnological variables were tested. In general, diversity indices exhibited poor linear correlations with environmental factors indicating ecological status. No clear patterns were found concerning species accumulation curves, occurrence-abundance, frequency-abundance and frequency distribution of diatom taxa between different trophic levels, although assemblages from stations with lower TP levels were characterized by relatively high dominances of certain taxa, mainly Achnanthidium minutissimum. In the light of these findings, the use of diatom diversity indices in biological quality surveillance protocols in continental waters is discouraged. Results are compared and discussed with similar studies.

Carry over from previous year environmental conditions alters dominance hierarchy in a prairie plant community

Aims To determine if an experimentally applied anomalous weather year could have effects on species composition and community structure that would carry over into the following year. Methods We conducted a field experiment applying two levels of temperature (ambient and +4C) and two levels of precipitation (ambient and doubled) and followed cover of plant species during the treatment year and one post-treatment year. Data analysis included ordination analysis, examination of species frequency distributions and comparison of cover of functional groups and individual species. Important Findings A drought during the summer and fall of the treatment year resulted in significant differences in community structure between the 2 years. C3 and winter annual species were depressed in the spring of the second year following the dry autumn. Species richness and legume cover increased in the second, wetter, year. Treatments caused no overall differences in community structure but did alter the dominance hierarchy of species among treatments as well as years. Warming decreased relative cover of winter annuals and early spring-flowering species but increased other annuals. Warming and double precipitation together increased cover of C4 perennial graminoids. In particular, the warming and precipitation treatments both increased the abundance of Andropogon gerardii, not individually altering the dominance hierarchy but together nearly doubling the relative cover of A.gerardii, making it the most abundant species in the combined treatment, while the cover of Bromus arvensis, the former dominant, decreased by 25%. The following year, Andropogon relative cover increased further in the former warmed plots, becoming dominant in both the formerly warmed and warmed plus double precipitation treatments. The year following treatments also saw an increase in relative cover of summer-blooming species in the formerly warmed plots and differences among the former treatments in species richness of functional groups. If the effects of one anomalous year on plant abundance can carry over into the following year, several warm years could have a significant impact on plant community structure.

Alternative codends to reduce bycatch in Chilean crustacean trawl fisheries

This study was conducted to determine the reduction in bycatch and the loss of target catch in trawl hauls for three commercial crustacean species (yellow squat lobster, Cervimunida johni, nylon shrimp, Heterocarpus reedi, and red squat lobster, Pleuroncodes monodon) in central Chile. Two experiments were carried out using the covered codend method; the first used different mesh sizes (56 and 70 mm, knot-centre to knot-centre) and shapes (diamond and square), and the second tested different reduction devices (escape panel and sorting grid). We analysed the escape proportions of the species caught and the size frequency distributions of the target species and Chilean hake ( Merluccius gayi), the main commercial bycatch species. The results demonstrate that it is feasible to significantly reduce bycatch while keeping losses within acceptable ranges. In particular, the best option for yellow squat lobster was the combination of a 70-mm diamond mesh with an escape panel that reduced non-target and target catches by 48% and 7%, respectively. For nylon shrimp, the best option was the use of a 56-mm diamond mesh with a sorting grid that reduced non-target and target catches by 41% and 11%, respectively. Although the results for red squat lobster were not as promising, they will help to guide future research.

Suitability of calcein as an in situ growth marker in burrowing bivalves

The fluorochrome calcein has been used in numerous growth studies of molluscs to internally mark calcified structures. Because of interspecific variations in marking success and possible effects on growth performance, methodological assessments of the suitability of calcein as a growth marker, especially in field contexts, remain necessary. Here we report on the effects of different calcein concentrations (100, 200, 400 and 800 mg l −1) on fluorescent mark deposition, growth rate, density, body condition and size–frequency distribution of an intertidal infaunal bivalve species, Loripes lacteus (Linnaeus, 1758), using an outdoor immersion technique. To avoid stress caused by handling and transportation, in situ enclosures were placed at seagrass-covered patches during low tide, to which calcein solutions were added. After a 1.3- to 2.6-h period of exposure to calcein, the enclosures were removed. Sites were sampled three months later. All calcein concentrations produced live L. lacteus with a clear fluorescent shell mark, but the percentage successfully marked tended to increase with higher calcein concentrations. Furthermore, marking success and growth rate decreased significantly with shell size (i.e., age). Calcein concentration did not measurably affect shell growth rate, body condition and size–frequency distribution, but the numerical densities were lower for sites treated with calcein concentrations ≥ 400 mg l −1. Our results suggest that in situ calcein-marking of burrowing lucinid bivalves with low concentrations (100–200 mg l −1) is a non-invasive and rapid method to determine growth rate, provided that the lucinids are not too old.

Continuous recruitment underpins fish persistence in the arid rivers of far-western Queensland, Australia

Fish living in highly variable and unpredictable environments need to possess life-history strategies that enable them to survive environmental extremes such as floods and drought. We used the length–frequency distributions of multiple fish species in multiple seasons and highly variable hydrological conditions to infer antecedent breeding behaviour in rivers of far-western Queensland, Australia. Hypotheses tested were as follows: (1) recruitment of some or all species of fish would occur within waterholes during no-flow periods; (2) there would be seasonal recruitment responses in some fish species; (3) recruitment of some species would be enhanced by channel flows and/or flooding. Hydrology and the incidence of flooding were highly variable across the study area during 2006–2008. Flood-influenced recruitment was evident for Hyrtl's tandan, Barcoo grunter and Welch's grunter. Silver tandan, golden goby, Cooper Creek catfish and Australian smelt showed evidence of seasonal recruitment unrelated to antecedent hydrology. However, most species demonstrated continual recruitment in isolated waterholes, irrespective of antecedent flow conditions and season. Continual and seasonal recruitment capabilities have obvious advantages over flood-pulse recruitment in rivers with highly unpredictable flood regimes and underpin the persistence of many fish species in arid and semiarid rivers.