Temporal Patterns Of Recruitment Research Articles

Supply-side ecology, barnacle recruitment, and rocky intertidal community dynamics: Do settlement surface and limpet disturbance matter?

The supply of new recruits can be a critical determinant of community structure, but estimating recruitment density can be challenging due to variation in larval supply, settlement, substratum, species interactions and physical stresses. We evaluated the effect of surface type and limpet “bulldozing” on settlement and recruitment of barnacles, using replicated field experiments sampled monthly at each of four sites along the central Oregon coast in 2001, 2003, and 2008. A particular goal was to evaluate the efficacy of Saf-T-Walk, a widely used textured surface, in quantifying actual patterns and levels of recruitment. In 2001 and 2003 experiments, surfaces were bare rock (ROCK) and Saf-T-Walk (STW). In 2008 experiments, to further evaluate the influence of surface rugosity, we added two additional artificial substratum types — smooth PVC plates (no texture) and travertine plates (TRAV, low texture). Limpet activity was manipulated using barriers of anti-fouling paint. Results indicated the overwhelming importance of surface texture. Recruitment density was highest in 2001, lower in 2003, and lowest in 2008. Recruitment on STW, the most textured surface, ranged up to 87 times greater than on ROCK, and the rank order of surfaces for recruitment density was STW > ROCK > TRAV > PVC which matches that for texture. Settlement differences were even greater, with up to 1180-fold higher settlement on STW than ROCK. Limpets usually had a negative effect on recruitment of Balanus glandula on ROCK, likely due to bulldozing and direct consumption, but had a positive effect on STW. These impacts were reduced or negated when recruitment density was higher (e.g., 2001) or lower than average (e.g., 2008). Limpets had no consistent effect on Chthamalus dalli. Abundances of settlers and recruits on the different surfaces were positively correlated (explaining up to 71% of the variance), and correlations between STW and other surfaces generally were stronger in the absence of limpets. Although compared to bare rock, recruitment to STW overestimates absolute rates of recruitment, use of STW settlement plates provides an effective and relatively efficient means of determining spatial and temporal patterns of recruitment at local to geographic scales.

Lessons from long-term studies of harvest methods in southwestern ponderosa pine–Gambel oak forests on the Fort Valley Experimental Forest, Arizona, U.S.A.

The Fort Valley Experiment Station (now Fort Valley Experimental Forest) has contributed many long-term studies to forest research. This paper focuses on a “Methods of Cutting” study initiated in 1913 on the Coulter Ranch Unit of Fort Valley and how that long-term study yielded important ecological and management lessons. We quantified the historical and contemporary forest patterns at this ponderosa pine–Gambel oak site, which was harvested using three different harvesting systems in 1913 (seed tree, group selection, and light selection) and was partially excluded from livestock browsing in 1919. Using nine historically stem-mapped permanent plots for the following three stand structural scenarios: 1913 pre-harvest (modeled), post-harvest (actual), and 2003–2006 (actual) conditions, we examined the short- and long-term consequences of harvest and livestock grazing land-use and stand dynamics. We assessed changes in spatial pattern under each harvesting system and in each structural scenario, and lastly, we examined spatial and temporal tree recruitment patterns as observed in the contemporary (2003–2006) conditions. The seed tree harvests effectively converted the spatial patterns from aggregated to random and left few trees, while the group selection and light selection had varying effects, but consistently exaggerated the spatial patchiness of the stand. By 2003–2006, all plots were aggregated at all scales and were one large patch of predominately small trees. Sites that were harvested, but excluded from livestock browsing had 40% more trees in 2003–2006. Contemporary recruitment patterns were significantly aggregated under all harvesting systems, but were most strongly aggregated if the site received a group selection or light selection cut. For group and light selection, pine seedlings initially established in stump patches created by harvesting and then proceeded to fill-in the remaining area, with recruitment rarely found under the residual pine or oak trees. Long-term data sets, such as these established by the Fort Valley Experimental Forest in 1913, are essential for quantifying the impact of historical land-use practices on contemporary forest composition and structure. Ignoring land-use legacies may lead to the misinterpretation of stand dynamics and development, and therefore should be explicitly quantified and incorporated into future management and restoration activities.

Abstract 1514: Oncolytic viral therapy for glioblastoma induces robust natural killer cell activation

Abstract Oncolytic viral (OV) therapy is a promising treatment being tested for safety and efficacy. Natural killer cells (NK) limit viral infections, and previous work suggests they may similarly attenuate virotherapy. We used flow cytometry to evaluate the temporal pattern of NK recruitment in intracranial tumors (U87DEGFR glioma) treated with the oncolytic herpes virus, rQnestin 34.5, or PBS. Quantification of NK recruitment into intracranial tumors treated with rQnestin34.5 or PBS revealed significant enrichment of these cells into the tumor hemisphere at early timepoints and continuing through 72 hours (2.2-fold, p=0.02) following infection. Moreover, NK cells recruited to the site of inoculation exhibited an activated phenotype, including enhanced CD69, CD62L, CD27, NKG2D, and CD127 staining compared to PBS treated mice. This robust NK response was demonstrated to be detrimental to OV efficacy through the enhanced survival of NK depleted mice treated with OV compared to OV treated mice containing NK cells (median survival 31.6 days compared to median survival 23.6 days, p=0.04). Since NK cells are recruited into the tumor microenvironment following infection, we postulated that OV infection of glioma cells was also activating NK cells. We measured granzyme B and IFNg production by NK cells in the presence of infected or uninfected glioma. Our results indicate that glioma mediated activation of NK cells was augmented by OV infection. Additionally, these findings were corroborated with increased NK killing of OV infected glioma compared to uninfected glioma. Due to the enhanced NK cytotoxic properties induced by OV infection, we proceeded to investigate the expression of NK activating ligands on the surface of infected glioma cells that could potentially mediate this effect. Focusing on ligands for NKG2D and the natural cytotoxicity receptors (NKp30, NKp44, and NKp46), viral infection of cultured gliomas was shown to upregulate ligand expression for NKG2D (24%, p=0.004), NKp46 (41%, p=0.01), and NKp30 (2.75-fold, p=0.001) while selectively downregulating ligand expression for NKp44 (2.8-fold, p=0.005). These findings suggest that viral infection of gliomas is altering the ligand signature for NK activation. Since NK cells possess both antiviral and antitumor properties, further work will investigate if virus induced NK activating signals can be selectively blocked in order to enhance viral efficacy while maintaining NK antitumor efficacy. This is the first study investigating the changes in NK cell activation and recruitment in gliomas upon oncolytic HSV-1 treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1514.

Fire-driven oak regeneration in French Mediterranean ecosystems

Regeneration by seeds for cork oak ( Quercus suber) and companion oaks (holm oak Quercus ilex and downy oak Quercus pubescens) is likely to be poor in the fire-prone Maures massif (southern France) but the causes are poorly known. Our objective was to assess the effective recruitment for these three oak species and their temporal pattern of recruitment, in order to determine the main limitation factors and the regeneration window of each species. We studied oak recruits (height <3 m) in naturally regenerated populations according to a gradient of fire recurrence and in five main vegetation types including shrublands and mixed mature woodlands. Fire recurrence was the main explanatory factor of oak recruitment, either directly or through vegetation type and microsite characteristics. The results indicate nil to low recruitment for holm oak and downy oak in shrublands, especially those recurrently burned and dominated by Cistus species. Cork oak recruited better than the other oaks in medium and high shrublands dominated by Erica arborea. In contrast, recruitment was high for holm and downy oak in mixed oak stands and mixed pine-oak stands that have not burned for decades. Microsite conditions such as coverage by litter and shrubs influenced oak recruitment, whereas landscape configuration and stand basal area had no influence. Our results suggest that strategic shrub-clearing, oak planting and protection of mixed oak woodlands as seed sources would help maintaining oak populations in the woodland–shrubland mosaic.

Effects of Patch Size and Type of Coffee Matrix on Ithomiine Butterfly Diversity and Dispersal in Cloud‐Forest Fragments

Determining the permeability of different types of landscape matrices to animal movement is essential for conserving populations in fragmented landscapes. We evaluated the effects of habitat patch size and matrix type on diversity, isolation, and dispersal of ithomiine butterflies in forest fragments surrounded by coffee agroecosystems in the Colombian Andes. Because ithomiines prefer a shaded understory, we expected the highest diversity and abundance in large fragments surrounded by shade coffee and the lowest in small fragments surrounded by sun coffee. We also thought shade coffee would favor butterfly dispersal and immigration into forest patches. We marked 9675 butterflies of 39 species in 12 forest patches over a year. Microclimate conditions were more similar to the forest interior in the shade-coffee matrix than in the sun-coffee matrix, but patch size and matrix type did not affect species richness and abundance in forest fragments. Furthermore, age structure and temporal recruitment patterns of the butterfly community were similar in all fragments, independent of patch size or matrix type. There were no differences in the numbers of butterflies flying in the matrices at two distances from the forest patch, but their behavior differed. Flight in the sun-coffee matrix was rapid and directional, whereas butterflies in shade-coffee matrix flew slowly. Seven out of 130 recaptured butterflies immigrated into patches in the shade-coffee matrix, and one immigrated into a patch surrounded by sun coffee. Although the shade-coffee matrix facilitated movement in the landscape, sun-coffee matrix was not impermeable to butterflies. Ithomiines exhibited behavioral plasticity in habitat use and high mobility. These traits favor their persistence in heterogeneous landscapes, opening opportunities for their conservation. Understanding the dynamics and resource requirements of different organisms in rural landscapes is critical for identifying management options that address both animals' and farmers' needs.

Postfire Recovery of Two Shrubs in the Interiors of Large Burns in the Intermountain West, USA

ABSTRACT. Shrub canopy cover can take between 10 and >50 years to recover to predisturbance levels following fire in sagebrush communities. The high degree of unpredictability of shrub recovery following prescribed fires and wildfires makes it difficult to prioritize restoration efforts and develop long-term plans for restoring or maintaining the integrity of sagebrush communities. Our overall goal was to develop a hypothesis based on descriptive data that describes the temporal pattern of recruitment for 2 important shrubs, Artemisia tridentata Nutt. ssp. vaseyana (Rydb.) Beetle and Purshia tridentata (Pursh) DC., in the interiors of large burns where little seed input from surviving shrubs occurs. We had 2 primary questions: (1) are there distinct temporal patterns of recruitment in the interiors of large burns that determine the recovery rate of the shrub canopy layer for species largely dependent on seedlings for reestablishment and (2) can we generate hypotheses that explain this variation in shrub r...

A cross-ecosystem comparison of spatial and temporal patterns of covariation in the recruitment of functionally analogous fish stocks

Temporal and spatial patterns of recruitment ( R) and spawning stock biomass ( S) variability were compared among functionally analogous species and similar feeding guilds from six marine ecosystems. Data were aggregated into four regions including the Gulf of Maine/Georges Bank, the Norwegian/Barents Seas, the eastern Bering Sea, and the Gulf of Alaska. Variability was characterized by calculating coefficients of variation and anomalies for three response variables: ln( R), ln( R/ S), and stock–recruit model residuals. Patterns of synchrony and asynchrony in the response variables were examined among and between ecosystems, between- and within-ocean basins and among functionally analogous species groups using pair-wise correlation analysis corrected for within-time series autocorrelation, multivariate cross-correlation analyses and regime shift detectors. Time series trends in response variables showed consistent within basin similarities and consistent and coherent differences between the Atlantic and Pacific basin ecosystems. Regime shift detection algorithms identified two broad-scale regime shift time periods for the pelagic feeding guild (1972–1976 and 1999–2002) and possibly one for the benthic feeding guild (1999–2002). No spatial patterns in response variable coefficients of variation were observed. Results from multivariate cross-correlation analysis showed similar trends. The data suggest common external factors act in synchrony on stocks within ocean basins but temporal stock patterns, often of the same species or functional group, between basins change in opposition to each other. Basin-scale results (similar within but different between) suggest that the two geographically broad areas are connected by unknown mechanisms that, depending on the year, may influence the two basins in opposite ways. This work demonstrates that commonalities and synchronies in recruitment fluctuations can be found across geographically distant ecosystems but biophysical causes of the fluctuations remain difficult to identify.

Variable temporal relationships between environment and recruitment in coral reef fishes

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 379:225-240 (2009) - DOI: https://doi.org/10.3354/meps07886 Variable temporal relationships between environment and recruitment in coral reef fishes Henri Vallès1,*, Wayne Hunte2, Donald L. Kramer1 1Department of Biology, McGill University, 1205 Avenue Docteur Penfield, Montreal, Quebec H3A 1B1, Canada 2Department of Biological and Chemical Sciences, University of the West Indies, Cave Hill Campus, University Drive, Cave Hill, St. Michael, Barbados *Email: hevals@gmail.com ABSTRACT: Studies of coral reef fish recruitment have focused more on factors influencing the return of larvae to reefs and the process of settlement than on factors affecting survival in the plankton, despite the well-documented importance of the larval environment for temperate marine species. We examined the ability of environmental factors to explain temporal patterns of recruitment in 8 taxa of coral reef fishes, distinguishing variables associated with settlement from those associated with the pelagic larval stage. At 10 d intervals over a 17 mo period, we collected newly settled fishes from settlement units in Barbados (West Indies). We collected concurrent data on 3 settlement-associated variables, lunar darkness, wind speed, and tidal amplitude, and 5 larval environment variables, sea-surface temperature, cloud cover, salinity, chlorophyll a concentration, and normalized water-leaving radiance at 555 nm. The last 3 were associated with low-salinity intrusions originating in the Amazon. We used hierarchical partitioning and Mallow’s C(p) model selection to identify important variables for each taxon. Temporal patterns of recruitment differed among taxa of which 6 showed significant environmental correlations. Significant settlement variables included lunar darkness and tidal amplitude. Significant larval environment variables were diverse and varied in magnitude and sign across taxa. The effects of larval variables were generally strong relative to settlement variables. The temporal scale of the strongest environmental predictor differed across taxa. Our study supports the views that planktonic factors affecting larval survival substantially influence recruitment in coral reef fishes and that different species are affected differently by a common, temporally variable, planktonic environment. KEY WORDS: Settlement · SMURF · Rubble · Pomacentridae · Labridae · Serranidae · Scaridae · Gobiidae Full text in pdf format PreviousNextCite this article as: Vallès H, Hunte W, Kramer DL (2009) Variable temporal relationships between environment and recruitment in coral reef fishes. Mar Ecol Prog Ser 379:225-240. https://doi.org/10.3354/meps07886 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 379. Online publication date: March 30, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

108 years of change in spatial pattern following selective harvest of a Pinus ponderosa stand in northern Arizona, USA

AbstractQuestions: How did an initial tree harvest in 1894 influence the spatial and temporal patterns of Pinus ponderosa recruitment? How do these patterns compare to our understanding of P. ponderosa stand dynamics prior to Euro‐American settlement? How might spatial pattern information, particularly with respect to patch characteristics, inform current restoration and management practices?Location: A 2.59‐ha permanent sample plot in the Fort Valley Experimental Forest, Flagstaff, Arizona. The plot was selectively harvested in 1894 and measured in 1909 and 2002.Methods: We used historical stem‐map and ledger data, contemporary data, and dendrochronological techniques to reconstruct stand structure (tree size, age, location) in three scenarios: (1) unharvested (1909), (2) harvested (1909), and (3) contemporary (2002). We used Clark and Evans' R, Ripley's K(t) univariate analysis, and correlogram analysis to assess the spatial pattern in each scenario. We also used Ripley's K12(t) bivariate analysis and tree age data to examine spatial and temporal recruitment patterns as observed in the contemporary scenario.Results and Conclusions: The unharvested stand was aggregated at scales up to 28 m. The selective harvest accentuated the spatial patchiness of the stand in 1909 and changed spatial patterns by homogenizing tree size within patches. By 2002, the stand was a single patch dominated by small trees. Post‐harvest recruitment patterns were not spatially random; Pinus seedlings initially established in natural grass openings and then proceeded to fill‐in stump patches created by harvesting. Knowledge of spatial pattern should be explicitly incorporated into restoration activities in these forests.

Recruitment of Juvenile Red Drum in North Carolina: Spatiotemporal Patterns of Year‐Class Strength and Validation of a Seine Survey

AbstractSixteen years of data from a North Carolina Division of Marine Fisheries seining survey were analyzed to assess the validity of the survey, describe spatial and temporal patterns in recruitment of red drum Sciaenops ocellatus, and evaluate factors that potentially contribute to recruitment variation. Overall, 11,817 age‐0 red drum (total length = 11–104 mm) were collected in the survey during 1991–2006. Annual estimates of red drum recruitment were variable over time and showed no long‐term trend. The dome‐shaped catch‐per‐unit‐effort (CPUE) pattern of all annual cohorts indicated that the seine survey captured peak abundance levels each year; the spatial coverage of the survey also appeared to be adequate. Regional correlations within North Carolina were strongest for areas that were adjacent to one another, and the North Carolina statewide index was not correlated with indices from Florida or Texas, suggesting that factors controlling recruitment of red drum operate at a scale of tens to hundreds of kilometers. Age‐0 red drum were caught at temperatures ranging from 8.5°C to 33.5°C and at salinities from 0.0 to 34.7 practical salinity units (psu; 1 psu ≈ 1‰). A generalized additive model explained only 8.1% of the variation in age‐0 abundance, suggesting that early juvenile abundance cannot be predicted with these abiotic factors. Variation in loss rates of age‐0 red drum appeared to be independent of variation in cohort density. The CPUE of age‐0 red drum was correlated with harvest of age‐2 fish 2 years later, suggesting that additional modification of year‐class strength after the early juvenile stage is moderate or weak. Results of this study have improved our understanding of red drum recruitment patterns while simultaneously validating the seine survey.

Dispersal of black sea bass (Centropristis striata) larvae on the southeast U.S. continental shelf: results of a coupled vertical larval behavior – 3D circulation model

AbstractIn the marine environment, pelagic dispersal is important for determining the distribution and abundance of populations, as well as providing connections among populations. Estimates of larval dispersal from spawning grounds are important to determining temporal and spatial patterns in recruitment that may have significant influences on the dynamics of the population. We present a case study of the dispersal of Centropristis striata (black sea bass) larvae on the southeast U.S. continental shelf. We use a coupled larval behavior – 3D circulation model to compare the effects of the timing and location of spawning against that of larval vertical migration on larval dispersal. Using the results of field data on larval vertical distributions, we compare the dispersal of virtual ‘larvae’ which have ontogenetic changes in vertical behavior with that of particles fixed near the surface and near the bottom. Larvae were released at potential spawning sites four times throughout the spawning season (February through May) for 3 yr (2002–04) and tracked for the assumed larval duration (from 27 to 37 days including the egg stage). Results indicate that adult behavior, in the form of spawning time and location, may be more important than larval vertical behavior in determining larval dispersal on the inner‐ and mid‐ continental shelves of this region.

Recruitment of Heliozoa, rhizopods and rotifers from the sediments of an extremely acidic lake during spring and early summer

AbstractThe goal of this study was to investigate the recruitment of zooplankton from the littoral sediment of Lake 111, an acidic lake in north‐east Germany, in April (spring) and June (early summer), and its role in coupling the benthos and the pelagic. Maximum heliozoan and rhizopod recruitment occurred in early summer from sediment cores incubated at ambient water temperatures (20°C). Conversely, recruitment of the rotifer Cephalodella sp. was highest in spring at ambient spring temperatures of 12°C. A combination of passive and active recruitment processes is likely responsible. The seasonal abiotic and biotic sediment characteristics were relatively constant and therefore not likely responsible for the observed temporal recruitment pattern. The sediment water and carbon content ranged from 20 to 50% (mean = 29 ± 6% standard deviation) and 2–12% (mean = 5 ± 2% standard deviation), respectively. Similarly, there was little variation in the chlorophyll‐a (mean = 0.2 ± 0.2 µg Chl‐a g−1 dry weight ≡ 6.1 ± 3.9 mg Chl‐a m−2). The in situ sediment bacterial density (0.82 × 109 ± 0.26 × 109 g−1 dry weight ≡ 1.01 × 109 ± 0.34 × 109 cells cm−3) was high. In contrast, the abundance of zoobenthos and their resting stages was low (&lt; 25 individuals cm−3, and mean of 90 ± 75 cysts cm−3, respectively), with no temporal pattern being observed. Temperature was the only abiotic factor influencing recruitment.This study suggests that, even in relatively young, chemically extreme lakes, the benthos can play an important role in whole lake microbial processes and zooplankton community composition. Such benthic repositories of resting stages potentially provide protection against adverse environmental changes.

Mos 3′ UTR regulatory differences underlie species‐specific temporal patterns of Mos mRNA cytoplasmic polyadenylation and translational recruitment during oocyte maturation

The Mos proto-oncogene is a critical regulator of vertebrate oocyte maturation. The maturation-dependent translation of Mos protein correlates with the cytoplasmic polyadenylation of the maternal Mos mRNA. However, the precise temporal requirements for Mos protein function differ between oocytes of model mammalian species and oocytes of the frog Xenopus laevis. Despite the advances in model organisms, it is not known if the translation of the human Mos mRNA is also regulated by cytoplasmic polyadenylation or what regulatory elements may be involved. We report that the human Mos 3' untranslated region (3' UTR) contains a functional cytoplasmic polyadenylation element (CPE) and demonstrate that the endogenous Mos mRNA undergoes maturation-dependent cytoplasmic polyadenylation in human oocytes. The human Mos 3' UTR interacts with the human CPE-binding protein and exerts translational control on a reporter mRNA in the heterologous Xenopus oocyte system. Unlike the Xenopus Mos mRNA, which is translationally activated by an early acting Musashi/polyadenylation response element (PRE)-directed control mechanism, the translational activation of the human Mos 3' UTR is dependent on a late acting CPE-dependent process. Taken together, our findings suggest a fundamental difference in the 3' UTR regulatory mechanisms controlling the temporal induction of maternal Mos mRNA polyadenylation and translational activation during Xenopus and mammalian oocyte maturation.

Flow‐related patterns in abundance and composition of the fish fauna of a degraded Australian lowland river

Summary1. A 7‐year study was conducted in three hydrologically distinct sections within the highly regulated, lowland Campaspe River to investigate the influence of hydrology on temporal and spatial patterns in fish composition, abundance and recruitment. One section had 6 months, one section 2 months and one section no months of increased flow due to storage releases. The fish fauna of the less regulated, nearby Broken River served as a reference to which that of the Campaspe River was compared for the last 3 years of the study to allow insight into the relative effects of hydrology, barriers to movement and other environmental characteristics. The study included one high‐flow year, a moderate‐flow year and five low‐flow years.2. A total of 16 fish species – 10 native and six alien – were caught in the Campaspe River, although of the native species, only three are considered to have self‐sustaining populations. The remaining species are either itinerants or a result of stocking. Alien species comprised approximately 64% of the total biomass of all fish caught.3. Overall composition of the fish fauna did not differ significantly by year, but did by section of river. Species richness and the abundance of most of the dominant species also differed significantly by river section, but there was little inter‐annual variation in the abundance of any species, except for European perch and for common carp; the latter showing an increase in abundance following a high‐flow event during the spring of 2000 as a result of recruitment.4. Overall faunal composition was not influenced by hydrology. However, multiple regression indicated that species richness, abundance of the dominant species and abundance of young‐of‐year (YOY) of golden perch, European perch and common carp all were influenced significantly by hydrological variables. The nature of the relationships was dependent on river section and hydrological season (‘winter’ or ‘spring/summer’). Of note was the result that the total abundance of fish and that of YOY common carp were significantly positively related to the number of spells above the threshold for movement upstream through the lower two weirs in the Campaspe River. Only one significant relationship between hydrological and fish‐related variables was found for the upper river section, whereas seven and five were found for the lower and middle sections respectively.5. Comparisons with fish collected in the Broken River over 3 years suggest that the fauna of the Broken River is in a more natural state than that of the Campaspe River. Since the two rivers do not differ substantially in water quality, and since both contain significant weirs, which act as barriers to movement of fish, flow regulation is most likely to be the major reason for the poor state of the fauna in the Campaspe River.

Evaluating a seasonal, sex-specific size-structured stock assessment model for the American lobster, Homarus americanus

Many models of different complexities are developed for fisheries stock assessment, and yet few have been rigorously evaluated for their performance in capturing fisheries population dynamics. This causes confusion about when a model should be used or not in assessing fisheries resources. This is especially true for models with complex structures. The present study evaluated the performance of a seasonal, sex-specific and size-structured stock assessment model with respect to the temporal pattern of recruitment, observation errors associated with input data, process errors and violation of model assumptions for the American lobster Homarus americanus. Using an individual-based lobster simulator, a series of lobster fisheries with different characteristics were simulated and the model was applied to the simulated data to estimate key fisheries parameters. Estimated values were then compared with the true values in the simulated fisheries to evaluate the model’s ability to capture the temporal trend in stock abundance, biomass and recruitment, and to identify factors that might result in model failure. Results show that this newly developed lobster stock assessment model performs well in capturing the dynamics of the lobster population under a wide range of conditions. Temporal trends in natural mortality and biased estimates of growth parameters posed the most serious problems. The present study shows the importance of model evaluation.

Floods, fire, and ice: disturbance ecology of riparian cottonwoodsThe review is one of a selection of papers published in the Special Issue on Poplar Research in Canada.

Cottonwoods are poplar trees that are well adapted to dynamic riparian, or streamside, zones throughout the Northern Hemisphere. Here we assess the influences of three prominent physical disturbances, floods, fire, and ice, on cottonwood population ecology. We emphasize cottonwoods along rivers from the “Crown of the Continent”, the central Rocky Mountain zone around the Canada – United States border, where five Populus species overlap and four hybridize. Moderate to major floods scour banks and deposit bars, creating barren and moist colonization sites that are essential for cottonwood seedling recruitment. Floods also scarify shallow roots, thus promoting clonal suckering, especially for the section Tacamahaca species: narrowleaf cottonwood ( Populus angustifolia James), balsam poplar ( Populus balsamifera L.), and black cottonwood ( Populus trichocarpa Torr. &amp; A. Gray). Fire would naturally be less frequent in some riparian zones because of the moist conditions and firebreaks provided by the streams, but with human use, floodplain forest fires have probably increased. Following fire, regrowth through clonal root and shoot suckers can be prolific for the Tacamahaca species, but is limited for the section Aigeiros , prairie cottonwood ( Populus deltoides Bartr.). River ice, and especially ice drives that accompany winter or spring break-up, provide powerful riparian disturbances that have often been neglected. Ice drives generate barren sites for seedling colonization, shear shoots, and scarify roots promoting shoot and root suckering, and sever branches, enabling dispersive clonal branch propagation. Following studies along many regional rivers, we conclude that: (i) riparian cottonwoods are tolerant of, and dependent upon, occasional physical disturbance for population rejuvenation; (ii) differing disturbance responses contribute to niche differentiation across the Populus species; (iii) different disturbances enable varied spatial and temporal patterns of cottonwood establishment, including fringe, general, and patch recruitment; and (iv) natural disturbance regimes probably favor native cottonwoods and disfavor some invasive, woody plants. River damming and flow regulation often attempt to attenuate flood and ice disturbance, a management objective that may hinder the perpetuation of native floodplain forests. We recommend that river resource managers seek to allow flood and ice disturbance, and additionally, fire may provide a managed disturbance that could rejuvenate overmature cottonwood groves along some regulated rivers.

Response of Pinus uncinata Recruitment to Climate Warming and Changes in Grazing Pressure in an Isolated Population of the Iberian System (NE Spain)

ABSTRACTTo infer future changes in the distribution of tree species in response to climatic variability, we need an understanding of the recruitment dynamics and their climatic controls at the species’ distribution limit. We studied the recruitment processes in an isolated population of Pinus uncinata Ram. located at the southwestern limit of the species’ distribution in Europe (Iberian System, NE Spain). We assessed (1) the temporal patterns of pine recruitment, and (2) how climate influenced recruitment. To reconstruct the recent recruitment episodes and to assess the climatic influence on recruitment and radial growth we employed dendrochronological methods. We mapped, measured the size, and estimated the age of all P. uncinata individuals located within a 50 m × 40 m plot. Additional age data were obtained from individuals located in four nearby 20 m × 20 m plots. The main episodes of tree establishment (early 1960s, late 1980s) coincided with low radial growth during a period with reduced grazing pressure. Grazing pressure and tree recruitment were not related at the spatiotemporal scale of this study. High May, August, and September minimum temperatures and high April precipitation were positively associated with recruitment, whereas high maximum April and June temperatures were negatively associated with recruitment. The studied population was in equilibrium with climate until the late 1990s, one of the warmest decades in the 20th century, when recruitment decreased despite the availability of suitable sites for establishment and the presence of reproductive individuals. We suggest that late-summer temperatures might have a non-linear negative threshold effect on recruitment rather than a linear effect. Despite increasing evidence of climate-induced recruitment episodes in isolated cold mountain forests, threshold effects of temperature on recruitment may imply limited range shifts of these populations in response to climate warming.

Spatial and temporal patterns of abundance and recruitment of ghost shrimp Trypaea australiensis across hierarchical scales in south-eastern Australia

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 341:165-175 (2007) - doi:10.3354/meps341165 Spatial and temporal patterns of abundance and recruitment of ghost shrimp Trypaea australiensis across hierarchical scales in south-eastern Australia Douglas Rotherham1,2,*, R. J. West1 1School of Biological Sciences, University of Wollongong, New South Wales 2522, Australia 2Present address: NSW Department of Primary Industries, Cronulla Fisheries Research Centre, PO Box 21, Cronulla, New South Wales 2230, Australia *Email: douglas.rotherham@dpi.nsw.gov.au ABSTRACT: Spatial and temporal variation in abundance and recruitment of burrowing ghost shrimp Trypaea australiensis was examined across 3 south-eastern Australian estuaries using a hierarchical sampling design, over a 2 yr period. We tested the hypothesis that abundances of shrimp were different between plots (10s to 100s of metres apart), sites within estuaries (kilometres apart), estuaries (100s of kilometres apart) and through time. More frequent sampling at 1 site also examined temporal variation at scales of months, seasons and years. Another aim was to investigate the reliability of using counts of burrow openings to indirectly measure the relative abundance of T. australiensis. Significant and interactive variability was detected at the scale of plots for the mean numbers of shrimp and recruits. Components of variation, however, suggested there was patchiness in abundance at all spatial scales within estuaries, particularly between replicates separated by metres. Indeed, between-replicate variance was greater than for any of the temporal scales examined. Despite this small-scale patchiness, patterns of abundance and recruitment were generally consistent across broad geographic areas. Numbers of shrimp generally increased throughout spring and summer periods, and recruitment also occurred during these times. The patterns of variation observed in this study highlight the importance of including appropriate scales of sampling in future monitoring studies of T. australiensis and in experiments concerned with detecting the effects of bait harvesting on populations of shrimp. We also conclude that counting burrow openings is not a reliable predictor of the relative abundance of T. australiensis. KEY WORDS: Spatial variation · Temporal variation · Patchiness · Bait harvesting · Yabby pump · Estuaries · New South Wales Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 341. Online publication date: July 04, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Spatial and temporal patterns of recruitment of the tunicate Ciona intestinalis on a mussel farm in Nova Scotia, Canada

Although possibly indigenous to Nova Scotia, the ascidian Ciona intestinalis has become a problem for local mussel aquaculturists. The local population ecology of the ascidian was studied by recording the depth, distribution, and timing of recruitment of C. intestinalis at four different locations (high wave exposure, low wave exposure, recently fallowed, and historically heavily fouled with tunicates) on a mussel farm at Indian Point, Nova Scotia. Animals were collected weekly from 11 collectors deployed at a depth of 4.5 m over two seasons (June–December 2003 and 2004). Recruitment occurred in two peaks during both seasons: the first peak lasted from late June to late July while the second peak lasted from early September to mid-November. Recruitment was highest in the sheltered and historically fouled location, intermediate in the fallowed site, and lowest in the site with highest wave exposure. Collectors were also deployed at different depths. Recruitment was highest at 4.5 m and to a lesser extent at 8.5 m. Little recruitment was seen at the surface (0.5 m) or in deeper water (12.5 and 16.5 m), except during the second peak in 2004. Overall, these results seem to indicate an abbreviated larval dispersal phase with young recruits settling very close to the pool of adults located on the mussel lines.

Moderate exercise and chronic stress produce counteractive effects on different areas of the brain by acting through various neurotransmitter receptor subtypes: A hypothesis

BackgroundRegular, "moderate", physical exercise is an established non-pharmacological form of treatment for depressive disorders. Brain lateralization has a significant role in the progress of depression. External stimuli such as various stressors or exercise influence the higher functions of the brain (cognition and affect). These effects often do not follow a linear course. Therefore, nonlinear dynamics seem best suited for modeling many of the phenomena, and putative global pathways in the brain, attributable to such external influences.HypothesisThe general hypothesis presented here considers only the nonlinear aspects of the effects produced by "moderate" exercise and "chronic" stressors, but does not preclude the possibility of linear responses. In reality, both linear and nonlinear mechanisms may be involved in the final outcomes. The well-known neurotransmitters serotonin (5-HT), dopamine (D) and norepinephrine (NE) all have various receptor subtypes. The article hypothesizes that 'Stress' increases the activity/concentration of some particular subtypes of receptors (designated nts) for each of the known (and unknown) neurotransmitters in the right anterior (RA) and left posterior (LP) regions (cortical and subcortical) of the brain, and has the converse effects on a different set of receptor subtypes (designated nth). In contrast, 'Exercise' increases nth activity/concentration and/or reduces nts activity/concentration in the LA and RP areas of the brain. These effects may be initiated by the activation of Brain Derived Neurotrophic Factor (BDNF) (among others) in exercise and its suppression in stress.ConclusionOn the basis of this hypothesis, a better understanding of brain neurodynamics might be achieved by considering the oscillations caused by single neurotransmitters acting on their different receptor subtypes, and the temporal pattern of recruitment of these subtypes. Further, appropriately designed and planned experiments will not only corroborate such theoretical models, but also shed more light on the underlying brain dynamics.