Spatial and Temporal Variation in Abundance and Biomass of Different Sex Classes of the Estuary Prawn Macrobrachium equidens (Dana, 1852) (Decapoda, Palaemonidae) From the Mekong Estuaries, With Notes on Its Salinity Tolerance

Experimental decoupling of canopy opening and debris addition on tropical gastropod populations and communities

A central question in ecology is explaining spatial variation in the abundance of species. Patterns of spatial variation in abundance can often be explained by spatial variation in the environment, including resource availability, climatic variables, and other factors that influence a species’ reproduction and survival. We show that spatial patterns in abundance may also be driven by temporal environmental variation, in the absence of any fixed spatial environmental variation. To illustrate this, we build on work by J. H. Brown, D. W. Mehlman, and G. C. Stevens, who demonstrated spatial patterns in bird abundances that can be explained by fixed spatial variation in the environment. Using a pair of simple stochastic models of bird population dynamics, we show that similar patterns can be generated through temporal environmental variation that has no fixed spatial component. This occurs when population dynamics are characterized by very weak density dependence, so that population densities exhibit near-random-walk behavior. Because similar patterns of spatial variation in species’ abundances can be produced by either fixed spatial environmental variation or spatiotemporal environmental variation, we argue that interpreting spatial variation in abundance may sometimes require understanding temporal variation in abundance.

Understanding what drives variation in fish abundance at reference sites provides perspective for assessing the effects of human alterations to river flow and land use. We examined temporal variation in fish community abundance in a headwater tributary of a large river in the upper South Island (New Zealand) over 10 years. We were interested in the influence of natural flow variation and temperature on native fish abundance within the context of potential competition/predation pressure from juvenile introduced trout. Results from biannual sampling highlighted the dominating influence of floods on fish population dynamics, overriding biotic effects. We found no evidence for adverse effects of trout on native fish, and flow-related habitat performed more poorly in explaining variation in fish abundance than low- and median-flow statistics. Differences in temporal variation in abundance between species were largely consistent with life histories that provide resistance and (or) resilience to flood flows and relative insensitivity to low flows. Long-term data (≥10 years) are needed for detecting meaningful trends and quantifying the effects of human activities on fish community abundance.

-We examined temporal variation in abundance of understory birds and fruiting plants in young (5-7 yr) and old (25-35 yr) successional habitats and in intact, lowland rain forest at Estacion Biologica La Selva, Costa Rica, between January 1985 and May 1986. Fruit abundance varied seasonally in each habitat but was consistently greatest in the youngest site. Frugivores and nectarivores accounted for four (forest and older successional) or five (younger successional) of the five most frequently captured bird species in each habitat. Capture rates of arboreal frugivores and arboreal frugivore-insectivores were greatest in the youngest site and were not different between older habitats. Temporal variation in capture rates of frugivores resulted from habitat shifts by resident individuals and from arrival and departure of altitudinal and latitudinal migrants. Capture rates of frugivores correlated with fruit abundance in forest and the older successional habitat but not in the youngest site. Capture rates of nectarivores and insectivores varied over time and among habitats, but rates showed no correlation with capture rates of frugivores. The lack of positive correlations in seasonal capture rates among trophic groups and the correlation between frugivores and fruit abundance support the view that temporal and spatial variation in bird abundance in tropical bird communities is at least partially in response to variation in resource abundance. Received 3 November 1989, accepted 28 July 1990. BIRD populations vary in abundance over time and space in both temperate (e.g. Kendeigh 1982, Holmes et al. 1986, many others) and tropical habitats (e.g. Fogden 1972; Karr 1976; Leighton and Leighton 1983; Martin and Karr 1986a; Loiselle 1987a, 1988; Loiselle and Blake 1991; but see Greenberg and Gradwohl 1986). Fluctuations in abundance arise from variation in population processes (Orell and Ojanen 1983, Faaborg et al. 1984, DeSante and Geupel 1987) and from movement of individuals among habitats (Karr and Freemark 1983, Wheelwright 1983, Recher and Holmes 1985, Loiselle et al. 1989, Loiselle and Blake 1991). Such movements may represent random redistribution of individuals (Wiens and Rotenberry 1978, Wiens 1984), but such hypotheses often have been advanced in the absence of data on food abundance. Individual movements may instead reflect responses to changes in microclimatic conditions (Karr and Freemark 1983, Petit 1989) or to temporal and spatial variation in food (e.g. Leighton and Leighton 1983, Wheelwright 1983, 1 Present address: Department of Biology, University of Missouri-St. Louis, 8001 Natural Bridge Road, St. Louis, Missouri 63121 USA. Recher and Holmes 1985, Loiselle and Blake 1991). Most studies lack concurrent data on fluctuations in both bird population levels and food abundance (but see Wheelwright 1983; Stiles 1985a; Levey 1988a, b; Loiselle and Blake 1991). Consequently, a more direct examination of avian responses to variations in food supply is central to resolving the controversial role of food as an influence in organization of species assemblages (Wiens 1984, Martin 1986). To address this controversy, we used data from concurrent studies on temporal and spatial variation in abundance of tropical frugivores and fruit among three habitats in Costa Rica. We focus mainly on frugivores, but for comparison we examined seasonal rhythms of bird groups (nectarivores, insectivores) that rely on different resources. Tropical frugivores are particularly appropriate for the study of the influence of resource availability on consumer populations because their diets can be readily determined (e.g. Wheelwright et al. 1984, Loiselle and Blake 1990) and their resources (fruit) accurately measured (Blake et al. 1990). Fruit-eating birds also are a major component of many tropical communi114 The Auk 108: 114-130. January 1991 This content downloaded from 157.55.39.104 on Sun, 19 Jun 2016 05:47:31 UTC All use subject to http://about.jstor.org/terms January 1991] Birds and Fruits in Lowland Tropics 115 ties (e.g. Stiles 1985b, Loiselle 1988, Karr et al. 1990, Loiselle and Blake 1991), and frugivores disperse seeds from a large proportion of tropical shrubs and trees that produce fruits (e.g. Howe and Smallwood 1982, Stiles 1985b). Thus, it is important both from theoretical and practical standpoints to better understand the interactions between frugivorous birds and fruitproducing plants (Stiles 1985b, c). STUDY AREA AND METHODS

A central question in ecology is explaining spatial variation in the abundance of species. Patterns of spatial variation in abundance can often be explained by spatial variation in the environment, including resource availability, climatic variables, and other factors that influence a species’ reproduction and survival. We show that spatial patterns in abundance may also be driven by temporal environmental variation, in the absence of any fixed spatial environmental variation. To illustrate this, we build on work by J. H. Brown, D. W. Mehlman, and G. C. Stevens, who demonstrated spatial patterns in bird abundances that can be explained by fixed spatial variation in the environment. Using a pair of simple stochastic models of bird population dynamics, we show that similar patterns can be generated through temporal environmental variation that has no fixed spatial component. This occurs when population dynamics are characterized by very weak density dependence, so that population densities exhibit near-random-walk behavior. Because similar patterns of spatial variation in species’ abundances can be produced by either fixed spatial environmental variation or spatiotemporal environmental variation, we argue that interpreting spatial variation in abundance may sometimes require understanding temporal variation in abundance.

Population reinforcement, through translocations of individuals, aims to restore populations of threatened species. The increase in population size or geographic distribution is often used as positive facts when assessing the recovery of a species, making abundance monitoring a major criterion. Based on 8‐year monitoring of a reinforced population of North African Houbara bustard (Chlamydotis undulata undulata), over an area of 50 170 km² in the eastern region of Morocco, we assessed the success of management actions by assessing spatial and temporal variation in abundance as well as the factors driving this variation. We used count data to estimate and spatialize population abundance. We then assessed environmental (climate) and management covariates (release effort and hunting management) associated with temporal and spatial variation in abundance. The overall estimate of abundance in the study area was 16 918 individuals (95% CI = 13 629–21 027) over our study period, with strong variation between years (range = 10 409–32 401). Our results highlighted strong spatial heterogeneity over the study area, linked to spatial variation in local climate and management conditions. Local abundances were negatively associated with local temperature, were higher in hunting than in non‐hunting areas, and were positively influenced by the number of birds released around the focal point. In addition to describing the spatio‐temporal variation in the abundance of the species on a large scale, we estimated two major proxies of its conservation status: population size and population trend. The determination of these proxies and the comparison with the counterfactual state of the species confirms the beneficial impact of the restoration and protection program on the dynamics of the North African Houbara bustard, while underlining the dependence of these dynamics on ongoing management.

Spatial and temporal variations in the abundance, distribution, and aggregation of krill (Thysanoessa raschii and Meganyctiphanes norvegica) in the lower estuary and Gulf of St. Lawrence

The present study investigated the ecological status of Opa reservoir, Obafemi Awolowo University, Ile Ife, Nigeria, based on the spatial and temporal variations in abundance and distribution of zooplankton. 72 samples were collected monthly with a quantitative net zooplankton from both the surface and bottom levels in three stations established at the dam site (Lacustrine), mid-lake (Transition) and inflow (Riverine) over a period of an annual cycle. A total of fifty-four (54) species were recorded from the reservoir comprising Rotifera (57.41%) > Arthropoda (33.33%) > Protozoa (5.56%) > Ciliophora (1.85%) = Cnidaria (1.85%), in the order of abundance. The least number of species (47) was recorded at the Transition station, while the highest number of species (49) occurred at the Lacustrine zone. Of all the zooplankton recorded, four species had significant spatial variation, while nine displayed seasonal variations during the study period (p ≤ 0.05). The highest species richness was observed in Transition surface station (4.18), followed by Lacustrine surface station (3.80) and Riverine surface station (3.23). Shannon’s index showed that zooplankton species were more diverse during the rainy season than dry season. The highest Trophic State Index (TSICR) with respect to Rotifer abundance occurred in Transition surface, followed by Riverine surface and the least occurred in Transition bottom portion. The mean TSICR value obtained was 65.20, indicative of hyper-eutrophic, while the mean TSICL value with respect to cyclopoida-calanoida obtained was 58.07 also revealing eutrophic status of the study area. Opa reservoir comprises mainly Rotifers and its TSICR showed the lake as eutrophic, tending towards becoming hyper-eutrophic, which could speed up the aging of the lake.

Zooplankton have extensively studied in the Indian Ocean, but very few systematic studies have been carried out in the marine waters around Sri Lanka. This study aimed to understand the temporal variations in the abundance and diversity of surface zooplankton in the south coast of Sri Lanka. Surface zooplankton samples were collected at five different locations in the south coast of Sri Lanka in November 2015 (second inter monsoon), December 2015 (Northeast monsoon, NE) and May 2016 (Southwest monsoon SW) using R/V Samuddrika. The vertical hauls of zooplankton were collected from 5 m depth at each station using WP-2 net with 180 μm mesh size and samples were immediately preserved in 5% buffered formalin. At the laboratory, zooplankton were identified to the lowest possible taxon using existing guides, species diversity, abundance (ind/m3), evenness and richness were estimated with respect to three different sampling phases. The data were subjected to hierarchical cluster analysis to identify the similarity between temporal variation and zooplankton abundance. A total of 152 zooplankton species were identified during this study. Species belonging to phylum Arthropoda appeared be the most abundant group and their standing crop (whole time period and sites) was 1906±115 ind/m3. Arthropods occupied nearly 86% of total zooplankton community. Among arthropods, order Poecilostomatoida showed the highest abundance (858±8 ind/m3) followed by phylum Protochordata (~3% and average of 74 ind/m3) chetognaths (2.1%) and mollusks (~1.9%). The highest species abundance was recorded in Novemver (1392±5 ind/m3) and lowest was in May (360±2 ind/m3). Species diversity was also highest in November and lowest in May. Cluster analysis revealed two clearly visible abundance clusters with respect to time. The results indicated that there are significant temporal variations in zooplankton abundance (ANOVA, P<0.05) in the South coast of Sri Lanka. Keywords: Zooplankton, Abundance, Diversity, Cluster analysis

Temporal variations in the abundance of heterotrophic bacteria were studied from February 2005 to January 2007, in ground waters from Agricultural, Domestic and Industrial land use areas. The lowest mean abundance (AODG ml -1 ) of Free Living Bacteria (2.2 × 10 5 ), Particle Bound Bacteria (0.07 ×10 5 ) and Total Bacteria (2.28 ×10 5 ) was recorded in ground water of Agricultural area; and the highest (1.07 × 10 6 , 1.13 ×10 5 and 1.70 ×10 6 , respectively) in that of Domestic area. In this investigation, 2.79% of the total bacteria determined by Acridine Orange staining in the ground water of Agricultural area could be grown on the artificial nutrient agar media and the comparative proportion in groundwater under the industrial area was 3.60 and 4.69% in the domestic area. Statistical analysis of the data revealed that several Physico-chemical parameters (Lab pH, air temperature, water temperature, conductivity, rainfall, BOD, CO 2 , alkalinity, hardness, ca, Mg, PO 4 , CL 2 , NO 3 , SO 4 , Total Anion of Strong Acid, Total Solids, Total Dissolved Solids and Total Suspended Solids) (p < .05) were potentially responsible for some of the temporal variations in heterotrophic bacterial abundance, suggesting the influence of landusespecific environmental stressors on the biota in these ecosystems. Key words : Temporal variation, heterotrophic bacterial abundance, colony forming units, Acridine Orange Direct Count, Direct Epifluroscence Microscopic Technique, ground water, land use patterns.

To quantify the magnitude and pattern of spatial variation in local population density within a single species, we analyzed large numbers of samples, representing a large geographic area or a wide range of ecological conditions. Our analyses focused on, but were not limited to, censuses of birds recorded in the North American Breeding Bird Survey. Birds and other organisms exhibited a common pattern: each species was represented by only a few individuals in most of the sample sites where it occurred, but was orders of magnitude more abundant in a few "hot spots." The highly clumped frequency distributions of intraspecific abundance among sample sites resemble distributions, such as the negative binomial, canonical lognormal, and broken stick, that have been used to characterize the distribution of abundances among species within local ecological communities. We hypothesize that the spatial variation in abundance largely reflects the extent to which local sites satisfy the niche requirements of a species. Several results are consistent with this hypothesis. First, a computer simulation model in which abundance is determined by the multiplicative combination of several independent environmental variables produces ranked distributions of abundances similar to those observed empirically. Second, geographic patterns of abundance of bird species have been relatively stable over several decades, indicating that different abundances are associated with particular places on the landscape. Third, the abundance of bird species varies in a systematic way over the geographic range, exhibiting positive spatial autocorrelation at small distances and a tendency to increase from the edges toward the center of the range. The magnitude and pattern of spatial variation in local population density has important implications for basic ecology and biogeography, especially for the dynamics and regulation of abundance on both space and time, the limits and internal structure of the geographic range, and the interspecific variation in abundance observed within local communities. Patterns of spatial and temporal variation in abundance should be considered in the design of nature reserves and the conservation of biological diversity.

Understanding patterns of species abundance is essential for planning landscape‐level conservation. The complex hierarchies of dendritic ecosystems result in different levels of heterogeneity at distinct geographic scales. Species responses to dynamic environmental drivers may also vary spatially depending on their interactions with landscape features. Monitoring abundance by explicitly quantifying their spatial and temporal variation is important for strategic management. We analysed brook trout (Salvelinus fontinalis) count data collected from 173 sites in western North Carolina between 1989 and 2015. We developed a Bayesian hierarchical model that used single‐ and multi‐pass electro‐fishing data and characterized their respective capture probabilities. We quantified spatial variation using a multi‐scale process model representative of the nested stream habitats, and we investigated differences in population temporal trends and responses to seasonal weather patterns by space and life stage. Trout abundance was lower on the Atlantic slope of the Eastern Continental Divide than in the interior, on average, and the Atlantic slope juveniles were more adversely affected by high winter flows. However, Atlantic slope populations of both lifestages demonstrated positive temporal trends, whereas Interior juveniles demonstrated a negative trend. We found higher spatial variation than temporal variation in abundance when conditioned on the covariates, where the primary source of spatial heterogeneity was revealed at the segment level, compared to watershed or network levels. Our multi‐scale spatial model outperformed simpler models in abundance estimation and out‐of‐sample prediction. The inferred per‐pass capture probabilities indicated that single‐pass surveys were as efficient as multi‐pass surveys. Synthesis and applications. Our study suggested conservation priority should involve multiple criteria, including present‐day abundance, temporal trend and sensitivity to environmental drivers. Based on the inferred scale‐specific variations in trout abundance, we recommend that future surveys strategically combine single‐pass surveys with multi‐pass surveys to optimize abundance estimation. Our approach is widely applicable to other species and ecosystems occupying dendritic habitats.

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 158:111-119 (1997) - doi:10.3354/meps158111 Temporal and multiple scale spatial variation in juvenile and adult abundance of the brown alga Ascophyllum nodosum Per Åberg*, Henrik Pavia Department of Marine Botany, Göteborg University, Carl Skottsbergs Gata 22, S-413 19 Göteborg, Sweden *E-mail: per.aberg@marbot.gu.se Observation of spatial and temporal variation in the distribution and abundance of organisms is often the starting point from which questions and hypotheses about ecological processes arise. This study was designed to investigate spatial variability in abundance of macrorecruits and adults of the brown alga Ascophyllum nodosum using hierarchical sampling programs. Five spatial scales ranging from 10-1 to 106 m were used, where the largest scale was represented by the distance between 2 areas, Tjärnö on the Swedish west coast and the Isle of Man in the Irish Sea. Temporal variation was investigated separately over 3 spatial scales as comparisons among the years from 1992 to 1995. Significant variation in abundance of 1.5 yr old juveniles was found on 2 spatial scales, 0.1 to 1.5 m and 2 to 30 m. A large variation among replicates suggested substantial variation on a smaller scale (<0.15 m). There was no significant variation in the abundance of juveniles among years as suggested by earlier studies. The abundance of the adult population varied between areas but not on smaller spatial scales. There was a significant variation in the abundance of the adult population among years. The potential egg production in female individuals was also investigated as a means of relating the abundance of juveniles to fertility estimates. The number of eggs per conceptacle and the number of conceptacles per receptacle did not vary significantly among individuals and the mean number of eggs per receptacle was estimated to be 7 x 104. The potential egg production was estimated to be 2.5 x 109 eggs m-2, a value much higher than previously reported for fucoids. Given the mean value of 40 juveniles m-2, the transition probability from egg to juvenile was estimated to be 2 x 10-8. Ascophyllum nodosum · Spatial variation · Temporal variation · Hierarchical sampling · Juvenile abundance · Egg production · Seaweed Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 158. Publication date: November 17, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.

In marine environments, macrofauna living in or on the sediment surface may alter the structure, diversity and function of benthic microbial communities. In particular, microbial nitrogen (N)-cycling processes may be enhanced by the activity of large bioturbating organisms. Here, we study the effect of the burrowing mud shrimp Upogebia deltaura upon temporal variation in the abundance of genes representing key N-cycling functional guilds. The abundance of bacterial genes representing different N-cycling guilds displayed different temporal patterns in burrow sediments in comparison with surface sediments, suggesting that the burrow provides a unique environment where bacterial gene abundances are influenced directly by macrofaunal activity. In contrast, the abundances of archaeal ammonia oxidizers varied temporally but were not affected by bioturbation, indicating differential responses between bacterial and archaeal ammonia oxidizers to environmental physicochemical controls. This study highlights the importance of bioturbation as a control over the temporal variation in nitrogen-cycling microbial community dynamics within coastal sediments.

The causes and consequences of temporal variation in the abundance of organisms constitute central themes in ecological inquiry. Rapid evolution can occur over ecological time-scales, potentially resulting in altered temporal variation in abundance and complicating inferences about the consequences of temporal variation. We assessed whether evolution altered the temporal variability in species' abundances in simple assemblages of species. We then compared experimental results to predictions from two-species models to better understand our results in the context of competitive and predator-prey interactions. We compared founder populations and their evolved descendants in experimental communities of ciliates and rotifers. Using a series of orthogonal contrasts, we then evaluated whether: (a) evolutionary history of invaders or (b) residents, (c) co-evolution among invaders and residents, and (d) invasion itself altered temporal variability in species abundances following invasion by a novel species. Using two-species competition and predator-prey models, we also generated predictions to better understand the effects of evolution on temporal variation in the abundances of interacting species. Finally, we compared experimental and modelling results to aid in the interpretation of which interspecific interactions might be affected by ongoing evolution in our communities. In experimental populations, differing evolutionary histories resulted in significant differences among treatments in abundances and temporal variation in abundances of both resident and invading species. For the contrasts, we found evidence that evolutionary history of the invader and residents, co-evolution among invaders and residents, and invasion itself affected temporal variability in abundance, but the importance of each differed for the two communities and the species within those communities. When comparing experimental results to model predictions, the increased abundance and decreased temporal variation in one invader, Euplotes daidaleos, are potentially consistent with evolution resulting in reduced attack rates in the novel community. Evolutionary history alone can affect temporal variation in the abundances of species, generating important consequences for interspecific interactions among species and complicating inferences about the consequences of temporal variability in biological communities.