Variation In Population Abundance Research Articles

Long-term responses of sandy beach crustaceans to the effects of coastal armouring after the 2010 Maule earthquake in South Central Chile

Earthquakes and tsunamis are large physical disturbances frequently striking the coast of Chile with dramatic effects on intertidal habitats. Armouring structures built as societal responses to beach erosion and shoreline retreat are also responsible of coastal squeeze and habitat loss. The ecological implications of interactions between coastal armouring and earthquakes have recently started to be studied for beach ecosystems. How long interactive impacts persist is still unclear because monitoring after disturbance generally extends for a few months. During five years after the Maule earthquake (South Central Chile, February 27th 2010) we monitored the variability in population abundances of the most common crustacean inhabitants of different beach zones (i.e. upper, medium, and lower intertidal) at two armoured (one concrete seawall and one rocky revetment) and one unarmoured sites along the sandy beach of Llico. Beach morphology changed after the earthquake-mediated uplift, restoring upper- and mid-shore armoured levels that were rapidly colonized by typical crustacean species. However, post-earthquake increasing human activities affected the colonization process of sandy beach crustaceans in front of the seawall. Lower-shore crab Emerita analoga was the less affected by armouring structures, and it was the only crustacean species present at the three sites before and after the earthquake. This study shows that field sampling carried out promptly after major disturbances, and monitoring of the affected sites long after the disturbance is gone are effective approaches to increase the knowledge on the interactive effects of large-scale natural phenomena and artificial defences on beach ecology.

Global weather and local butterflies: variable responses to a large-scale climate pattern along an elevational gradient.

Understanding the spatial and temporal scales at which environmental variation affects populations of plants and animals is an important goal for modern population biology, especially in the context of shifting climatic conditions. The El Niño Southern Oscillation (ENSO) generates climatic extremes of interannual variation, and has been shown to have significant effects on the diversity and abundance of a variety of terrestrial taxa. However, studies that have investigated the influence of such large-scale climate phenomena have often been limited in spatial and taxonomic scope. We used 23 years (1988-2010) of a long-term butterfly monitoring data set to explore associations between variation in population abundance of 28 butterfly species and variation in ENSO-derived sea surface temperature anomalies (SSTA) across 10 sites that encompass an elevational range of 2750 m in the Sierra Nevada mountain range of California. Our analysis detected a positive, regional effect of increased SSTA on butterfly abundance (wetter and warmer years predict more butterfly observations), yet the influence of SSTA on butterfly abundances varied along the elevational gradient, and also differed greatly among the 28 species. Migratory species had the strongest relationships with ENSO-derived SSTA, suggesting that large-scale climate indices are particularly valuable for understanding biotic-abiotic relationships of the most mobile species. In general, however, the ecological effects of large-scale climatic factors are context dependent between sites and species. Our results illustrate the power of long-term data sets for revealing pervasive yet subtle climatic effects, but also caution against expectations derived from exemplar species or single locations in the study of biotic-abiotic interactions.

Influence ofOecophylla longinodaLatreille, 1802 (Hymenoptera: Formicidae) on Mango Infestation byBactrocera dorsalis(Hendel) (Diptera: Tephritidae) in Relation to Senegalese Orchard Design and Management Practices

Damage caused by the fruit fly Bactrocera dorsalis (Hendel) (syn. B. invadens Drew, Tsuruta & White) (Diptera: Tephritidae) on mangoes in Senegal leads to production losses. A potential biological control agent against this pest is the weaver ant Oecophylla longinoda Latreille (Hymenoptera: Formicidae). Senegalese mango-based orchards present a diversity in design and management practices that can influence the abundance of these two species in orchards. In this study we evaluated i) the ability of the O. longinoda ant to limit B. dorsalis damage in Senegalese orchards, and ii) variations in population abundance for these two species depending on orchard design and management practices. The study was conducted in Senegal in the Niayes area and the Thies plateau. Fifteen orchards were sampled among three out of four kinds of orchards identified in this area: (1) ‘No-input mango diversified orchards’, (3) ‘Medium-input citrus-predominant orchards’ and (4) ‘Medium-input large mango- or citrus-predominant orchards’. In one of the orchards we measured infestation rates and numbers of fly pupae that developed from mangoes collected from trees (cv. Kent) ‘with’ and ‘without’ O. longinoda colonies over three harvesting periods (May, July and August) in 2013. The abundance of O. longinoda and B. dorsalis was measured for two months in the dry season and two others in the rainy season in the 15 orchards in 2012. The presence of O. longinoda on trees reduced the proportion of mangoes attacked by B. dorsalis as well as the number of pupae that developed from infested mangoes. The abundance of O. longinoda and B. dorsalis was negatively correlated. The abundance varied depending on the orchard design and management practices. O. longinoda abundance was greater in orchard types 1 and 3 than in type 4. Conversely, B. dorsalis abundance in the rainy season tended to be greater in orchard type 4 than in types 1 and 3. This study showed that O. longinoda is effective in limiting mango infestations by B. dorsalis. It also showed that the abundance of these two species was influenced by the orchard design and management practices. Therefore, using O. longinoda to control fruit flies is possible in Senegalese mango-based orchards by promoting weaver ant preservation.

Aerial surveys to monitor bluefin tuna abundance and track efficiency of management measures

Conservation and management measures for exploited fish species rely on our ability to monitor variations in population abundance. In the case of the eastern stock of Atlantic bluefin tuna (ABFT), recent changes in management policies have strongly affected the reliability of fishery-dependent indicators due to drastic changes in fishing season/area, fisheries selectivity and strategy. However, fishery-independent indices of abundance are rare for large pelagic fish, and obtaining them is often costly and labor intensive. Here, we show that scientific aerial surveys are an appropriate tool for monitoring juvenile bluefin tuna abundance in the Mediterranean. We present an abundance index based on 62 aerial surveys conducted since 2000, using 2 statistical approaches to deal with the sampling strategy: line and strip transects. Both approaches showed a significant increase in juvenile ABFT abundance in recent years, resulting from the recovery plan established in 2007. Nonetheless, the estimates from the line transect method appear to be more robust and stable. This study provides essential information for fisheries management. Expanding the spatial coverage to other nursery grounds would further increase the reliability and representativeness of this index.

Seasonal Variation in Population Abundance and Chytrid Infection in Stream-Dwelling Frogs of the Brazilian Atlantic Forest.

Enigmatic amphibian declines were first reported in southern and southeastern Brazil in the late 1980s and included several species of stream-dwelling anurans (families Hylodidae and Cycloramphidae). At that time, we were unaware of the amphibian-killing fungus Batrachochytrium dendrobatidis (Bd); therefore, pollution, habitat loss, fragmentation and unusual climatic events were hypothesized as primary causes of these declines. We now know that multiple lineages of Bd have infected amphibians of the Brazilian Atlantic forest for over a century, yet declines have not been associated specifically with Bd outbreaks. Because stream-dwelling anurans occupy an environmental hotspot ideal for disease transmission, we investigated temporal variation in population and infection dynamics of three stream-adapted species (Hylodes asper, H. phyllodes, and Cycloramphus boraceiensis) on the northern coast of São Paulo state, Brazil. We surveyed standardized transects along streams for four years, and show that fluctuations in the number of frogs correlate with specific climatic variables that also increase the likelihood of Bd infections. In addition, we found that Bd infection probability in C. boraceiensis, a nocturnal species, was significantly higher than in Hylodes spp., which are diurnal, suggesting that the nocturnal activity may either facilitate Bd zoospore transmission or increase susceptibility of hosts. Our findings indicate that, despite long-term persistence of Bd in Brazil, some hosts persist with seasonally variable infections, and thus future persistence in the face of climate change will depend on the relative effect of those changes on frog recruitment and pathogen proliferation.

Diseases affecting livestock production mediate landscape scale of a changing pasture regime in Lake Mburo Conservation Area, Uganda

This study investigated whether spatial disparities in pastoral herd sizes across rangelands from Lake Mburo National Park (LMNP) boundary was responsible for a changing pasture regime. A midst growing concern that cattle diseases associated with wild ungulates outside the protected areas impose limitations on pastoralist household income, the affected communities respond by overstocking as an adaption to disease risks. Therefore, increasing cattle stock holding among pastoralists living at the park boundary was suspected to be facilitating the disappearance of forests in Lake Mburo Conservation Area (LMCA). We applied ecosystem approach in a cross-sectional survey design to assess whether impact of diseases transmitted at the nexus of wildlife and livestock play intermediary role in the emerging spatial pattern of pasture regimes in LMCA. Paired sample t-test was used to examine the mean differences of animal populations between managed and unmanaged pasture and interpreted with Geo-eye satellite data of a typical landscape of savanna ecosystem of LMCA. The results revealed a significant difference (p < 0.05) in the distribution of wild species of animals between managed and unmanaged pasture. Spatial variation in population abundance of wild animals between distance zones was also reflected in the distribution of average household stockholding as well as cattle mortalities along a distance gradient from LMNP boundary. These findings could guide evidence based monitoring of long term effects of changing pasture regimes on pastoralist livelihood systems around LMCA. For example, future research should consider complementarities and overlap of the diets of wild ungulates and cattle at the nexus of wildlife and livestock interface. This will provide an understanding of how wildlife presence in rangelands can lead to either favorable or adverse changes in the fauna as far as the domestic livestock species of cattle and small ruminants are concerned.

Abundance and Distribution of Overwintering Red-tailed Hawks and American Kestrels in an Agricultural Landscape in Northeastern Arkansas

Abstract Although Red-tailed Hawks (Buteo jamaicensis) and American Kestrels (Falco sparverius) are common raptors in the U.S.A., their wintering population abundance and distribution has not been studied recently in Arkansas. We assessed the temporal and spatial variation in population abundance of Red-tailed Hawks and American Kestrels over the winter in northeastern Arkansas. We conducted weekly surveys from an automobile in Craighead and Poinsett counties, Arkansas, October 2012–March 2013. Abundance of Red-tailed Hawks (n = 854 total observations) and American Kestrels (n = 165 total observations) along the transect increased during winter months. The overall abundance indices were 7.05 Red-tailed Hawks per 10 km (highest ever recorded) and 1.36 American Kestrels per 10 km. We found no significant differences in the utilization of the various cover types (i.e., short rice stubble, soybean stubble, and fallow areas/roadsides) for either species. However, both species differed in their use of perch...

Changes in the Abundance and Distribution of Black-necked Swans (Cygnus melancoryphus) in the Carlos Anwandter Nature Sanctuary and Adjacent Wetlands, Valdivia, Chile

Abstract. Recently, the Carlos Anwandter Nature Sanctuary (Sanctuary) at the Cruces River, Chile, has undergone important ecosystem changes. Brazilian waterweed (Egeria densa), the main food resource of Black-necked Swans (Cygnus melancoryphus), has greatly decreased in abundance. This disappearance may have affected the abundance of Black-necked Swans within the Sanctuary; however, the variation in the Black-necked Swan population is still poorly understood. Spatiotemporal variation in population abundance and feeding/breeding ecology of Black-necked Swans was analyzed in the Sanctuary and adjacent wetlands (non-protected areas outside the Sanctuary) from 2000 to 2010. Temporal fluctuations in Black-necked Swan abundance were recorded, with increases in population size from late December to early June and decreases from late June to late September. Five main feeding grounds that were devoid of Brazilian waterweed were identified. However, several other aquatic plants were recorded on these grounds, sugge...

Population structure of an endemic gastropod in Chinese plateau lakes: evidence for population decline

The highly endemic diversity of the Yun-Gui plateau lakes has decreased severely in recent decades. Protecting these native species is a challenge, in part because their biology and population ecology remain unexplored. We investigated 1 focal endangered gastropod species (Margarya melanioides) in 1 plateau lake: 1) to quantify spatiotemporal variation in population abundance and size structure, and 2) to identify the key variables influencing these variations. Density was 0.068 individuals/m(2) with an estimated total population size of 2.1 x 10(7) individuals. The size-frequency distribution was skewed toward larger, mature individuals (40.0-60.0 mm), a result indicating that the population is aging. Population size structure showed high spatial heterogeneity, and density was highest in the north-central region of the lake. Redundancy analysis indicated that human-induced environmental degradation strongly controlled the spatial patterns in size-structure. This species has experienced a remarkable decrease in range and population size over the past 50 y, and the population probably will collapse by 2015. The decline could be attributed to demographic drift, environmental filtering, human harvesting, and its limited dispersal ability. Our studies should give useful information for building efficient conservation strategies for M. melanioides and other threatened plateau gastropods. Further studies are needed on the population ecology and reproductive biology of M. melanioides, particularly on its reproductive behavior and size-specific survivorship.

Somatic and molt production in Euphausia mucronata off central-southern Chile: the influence of coastal upwelling variability

Seasonal and inter-annual variability in population abundance, biomass, and somatic and molt production of the Humboldt Current krill Euphausia mucronata were studied during a monthly time series (August 2002 to June 2007) at Stn 18 (36° 30' S, 73° 07' W) off central-southern Chile. Experimental measurements in krill were performed at Stn 18 (in 2007 and 2008) and north- ern Chile (2010) in order to estimate vital rates for use in E. mucronata secondary production calculation at Stn 18. Coastal upwelling intensity was the main oceanographic process found to control E. mucronata population abundance and biomass production on seasonal and inter-annual time scales. Spawning peaks and population structure indicate that E. mucronata produces at least 2 generations per year. The main spawning period occurs during the austral spring when phytoplankton concentration is high. A second, less intense spawning period occurs at the end of the austral summer and early autumn. E. mucronata had a mean biomass of 100 mg C m �3 and an integrated annual secondary production of 2432 mg C m �3 yr �1 , with an overall production/ biomass ratio (P/B) ratio of 24. In May 2007, a maximum daily integrated biomass of 5 g C m �3 and total daily secondary production of 63 mg C m �3 d �1 were observed. These estimates are consider- ably higher than those reported for other krill species in coastal upwelling regions. Multivariate analyses indicate that upwelling-favorable winds promote high E. mucronata biomass and sec- ondary production, but higher abundance and biomass were found during the transition periods from upwelling to downwelling conditions. Results suggest that E. mucronata has a highly effi- cient behavioral strategy to attain high production rates and recover rapidly from potential off- shore losses due to advective processes in a highly productive coastal upwelling ecosystem.

Long-term trajectory of some elasmobranch species off the Tuscany coasts (NW Mediterranean) from 50 years of catch data

The time series of elasmobranch catch rates off the Tuscany coasts (NW Mediterranean) were investigated by means of min/max auto-correlation factor analysis in order to estimate variations in population abundance and evaluate the influence of environmental and anthropogenic factors. The analyses highlighted a general decreasing trend in the catch rates of sharks and skates from 1961 to the mid-1990s, mainly influenced by the increase in fishing effort. Since the 1990s, the EU Common Fishery Policy for the Mediterranean has promoted the reduction of fishing fleets through incentives to vessel demolition. The Porto S. Stefano trawl fleet has decreased by about 50%, leading to a decrease in fishing effort which seemed to be the most relevant factor affecting the increasing trend shown by the catch rates of Galeus melastomus, Scyliorhinus canicula and skates from 1991 to 2009. The elasmobranch assemblage did not undergo major shifts but the weighted frequency of occurrence shows that elasmobranchs were more frequent in the past. Particular caution should be paid in interpreting the recent rebound of some species as an early sign of recovery: trawl survey data and landing data show that over the last 50 years elasmobranch fauna have undergone a drastic decline and that recent rebounds are still far from a recovery to historical levels.

Linking patterns and processes across scales: the application of scale-transition theory to algal dynamics on rocky shores

Understanding how species and environments respond to global anthropogenic disturbances is one of the greatest challenges for contemporary ecology. The ability to integrate modeling, correlative and experimental approaches within individual research programs will be key to address large-scale, long-term environmental problems. Scale-transition theory (STT) enables this level of integration, providing a powerful framework to link ecological patterns and processes across spatial and temporal scales. STT predicts the large-scale (e.g. regional) behavior of a system on the basis of nonlinear population models describing local (e.g. patch-scale) dynamics and the interaction between these nonlinearities and spatial variation in population abundance or environmental conditions. Here we use STT to predict the dynamics of turf-forming algae on rocky shores at Capraia Island, in the northwest Mediterranean. We developed a model of algal turf dynamics based on density-dependent growth that included the effects of local interactions with canopy algae. The model was parameterized with field data and used to scale up the dynamics of algal turfs from the plot scale (20×20 cm) to the island scale (tens of km). The interaction between nonlinear growth and spatial variance in cover of turfing algae emerged as a key term to translate the local dynamics up to the island scale. The model successfully predicted short-term and long-term mean values of turf cover estimated independently from a separate experiment. These results illustrate how STT can be used to identify the relevant mechanisms that drive large-scale changes in ecological communities. We argue that STT can contribute significantly to the connection between biomechanics and ecology, a synthesis that is at the core of the emerging field of ecomechanics.

Maximum sustainable yield estimates of Ladypees, Sillago sihama (Forsskål), fishery in Pakistan using the ASPIC and CEDA packages

Using surplus production model packages of ASPIC (a stock-production model incorporating covariates) and CEDA (Catch effort data analysis), we analyzed the catch and effort data of Sillago sihama fishery in Pakistan. ASPIC estimates the parameters of MSY (maximum sustainable yield), F msy (fishing mortality), q (catchability coefficient), K (carrying capacity or unexploited biomass) and B1/K (maximum sustainable yield over initial biomass). The estimated non-bootstrapped value of MSY based on logistic was 598 t and that based on the Fox model was 415 t, which showed that the Fox model estimation was more conservative than that with the logistic model. The R 2 with the logistic model (0.702) is larger than that with the Fox model (0.541), which indicates a better fit. The coefficient of variation (cv) of the estimated MSY was about 0.3, except for a larger value 88.87 and a smaller value of 0.173. In contrast to the ASPIC results, the R 2 with the Fox model (0.651–0.692) was larger than that with the Schaefer model (0.435–0.567), indicating a better fit. The key parameters of CEDA are: MSY, K, q, and r (intrinsic growth), and the three error assumptions in using the models are normal, log normal and gamma. Parameter estimates from the Schaefer and Pella-Tomlinson models were similar. The MSY estimations from the above two models were 398 t, 549 t and 398 t for normal, log-normal and gamma error distributions, respectively. The MSY estimates from the Fox model were 381 t, 366 t and 366 t for the above three error assumptions, respectively. The Fox model estimates were smaller than those for the Schaefer and the Pella-Tomlinson models. In the light of the MSY estimations of 415 t from ASPIC for the Fox model and 381 t from CEDA for the Fox model, MSY for S. sihama is about 400 t. As the catch in 2003 was 401 t, we would suggest the fishery should be kept at the current level. Production models used here depend on the assumption that CPUE (catch per unit effort) data used in the study can reliably quantify temporal variability in population abundance, hence the modeling results would be wrong if such an assumption is not met. Because the reliability of this CPUE data in indexing fish population abundance is unknown, we should be cautious with the interpretation and use of the derived population and management parameters.

Hierarchical Bayesian estimation of the population viability of an epixylic moss

Summary1. Understanding the variation in population abundances requires accounting for the environmental variability and uncertainty on different scales. We developed and evaluated a Bayesian hierarchical model for the inter‐annual variation in population abundance of the epixylic bryophyte Buxbaumia viridis. The model accounts for spatio‐temporal variability on two spatial scales. We used data on population abundance and on the weather variables at regional level collected between 1996 and 2003, and data on dead wood amount collected between 1996 and 2008. We also provide a Bayesian estimate of the population viability, specifically the population stochastic growth rate (log λS), which accounts for natural variability and uncertainty.2. Previous estimates of population viability did not account for uncertainties in a satisfactory way. First, point estimates of log λS cannot, by definition, express variation. Second, the commonly used approach to estimate log λS and its confidence interval underestimates uncertainties. The approach aims to estimate the mean of log λS, with the confidence interval representing the uncertainty in the estimate of this mean. The interval does not reflect the natural variation and uncertainty.3. We estimated a probability distribution of log λS, where the probability distributions of the year‐specific growth rates (log λy) are accounted for. The species is likely to decline under current environmental conditions. Based on the probability distribution of log λS, we estimated this risk to be 81%.4. We found support for the hypotheses that the population dynamics are driven by autumn frosts, by spring precipitation and temperature (regional variables), and by the preceding year’s population abundance (local variable).5. Synthesis. Statements about the viability of populations should not be based on point estimates of log λS. Instead, the full probability distribution of log λS should be used, which explicitly accounts for the hierarchically structured natural variability and uncertainty. This distribution allows estimating the risk for a population decline, or providing an estimate of the confidence in a statement about a decline. This quantitative information can be weighed against other interests. We expect this Bayesian approach to be especially useful in the viability analysis of natural populations experiencing environmental variability.

Variability in Population Abundance and the Classification of Extinction Risk

Classifying species according to their risk of extinction is a common practice and underpins much conservation activity. The reliability of such classifications rests on the accuracy of threat categorizations, but very little is known about the magnitude and types of errors that might be expected. The process of risk classification involves combining information from many sources, and understanding the quality of each source is critical to evaluating the overall status of the species. One common criterion used to classify extinction risk is a decline in abundance. Because abundance is a direct measure of conservation status, counts of individuals are generally the preferred method of evaluating whether populations are declining. Using the thresholds from criterion A of the International Union for Conservation of Nature (IUCN) Red List (critically endangered, decline in abundance of >80% over 10 years or 3 generations; endangered, decline in abundance of 50-80%; vulnerable, decline in abundance of 30-50%; least concern or near threatened, decline in abundance of 0-30%), we assessed 3 methods used to detect declines solely from estimates of abundance: use of just 2 estimates of abundance; use of linear regression on a time series of abundance; and use of state-space models on a time series of abundance. We generated simulation data from empirical estimates of the typical variability in abundance and assessed the 3 methods for classification errors. The estimates of the proportion of falsely detected declines for linear regression and the state-space models were low (maximum 3-14%), but 33-75% of small declines (30-50% over 15 years) were not detected. Ignoring uncertainty in estimates of abundance (with just 2 estimates of abundance) allowed more power to detect small declines (95%), but there was a high percentage (50%) of false detections. For all 3 methods, the proportion of declines estimated to be >80% was higher than the true proportion. Use of abundance data to detect species at risk of extinction may either fail to detect initial declines in abundance or have a high error rate.

The usefulness of field data and hunting statistics in the assessment of wild rabbit (Oryctolagus cuniculus) conservation status in Portugal

Context. The wild rabbit (Oryctolagus cuniculus) is a keystone species from the Iberian Peninsula that has suffered a strong decline in Spain during the past decades. Data on historical and current population trends in Portugal are virtually non-existent. Aims. To investigate changes in rabbit abundance at the national level so as to inform conservation status assessments, and to evaluate the usefulness of hunting bags as a rabbit abundance index. Methods. Field surveys based on latrine counts in linear transects were performed in two periods (1995 and 2002) to assess variation in population abundance. Hunting bags were also analysed for the same period to verify whether these data showed the same trends. General trends of rabbit abundance were estimated using TRIM software. Key results. Field data revealed that most of the sampling units across Portugal have low abundances, despite the observation of local high-density spots. A population reduction of 27% was estimated. Although some fluctuations were observed in hunting bags, global results obtained from these data suggest a slightly increasing trend in rabbit abundance. Conclusions. A discrepancy between field data and hunting statistics was observed. Because hunting bags may be influenced by sporadic management operations undertaken by hunters and the lack of systematic procedures in data collection, we believe that hunting statistics are not representative of real changes in rabbit populations. Thus, observed reduction in rabbit abundance estimated by field data, combined with the high initial morbidity due to rabbit haemorrhagic disease (RHD) after 1988 and the potential for continuing decline in population trends because of other factors, led to an inference of a reduction of &gt;30% in rabbit abundance in Portugal during the past decade. Implications. Taking into account the estimated reduction, the species’ biology and socioeconomic implications, wild rabbit in Portugal was listed in 2005 in the Near Threatened category under IUCN criteria. Because of its ecological and economic importance, this classification prompted the definition of several conservation actions aimed at the recovery of the species in Portugal.

An Ecosystem Perspective on Re‐establishing Native Deepwater Fishes in the Laurentian Great Lakes

AbstractHerein we examine scientific questions related to successful re‐establishment of native deepwater fish communities in the Laurentian Great Lakes, and we (1) propose a conceptual model for native deepwater fish communities; (2) review current research and identify research hypotheses for lake trout Salvelinus namaycush, pelagic ciscoes Coregonus spp., and sculpins (Cottus spp. and Myoxocephalus spp.); (3) pose research questions emerging at community and ecosystem levels; and (4) identify high‐priority research topics related to population re‐establishment. The conceptual model is based on a generalized life cycle nested within processes at the population, metapopulation, community, and ecosystem levels. The conceptual model assumes that variation in population abundance is a natural phenomenon and that biodiversity contributes to ecosystem stability. Key research topics related to lake trout re‐establishment include understanding recruitment variation over space and time, identifying sources of early life history mortality, determining the level of genetic differentiation among morphotypes and populations, and comparing the life history and ecology of lean lake trout with those of other lake trout morphotypes. Key research topics related to re‐establishing deepwater species of cisco include resolving uncertainties in species identifications, understanding processes maintaining distinctiveness among species, understanding processes leading to cyclic and erratic recruitment, and developing effective propagation methods. Key research topics related to re‐establishment of sculpin species include comparing spawning ecology and early life history of each species, determining population structure, and evaluating the feasibility of live‐transfer methods. Key research topics related to community‐ and ecosystem‐level interactions include understanding large‐scale directional influences on community function, expanding current views on ecological succession in large lakes, and determining the evolutionary role of diel vertical migration in phenotypic diversification of deepwater fishes. Finally, we propose that research in four topical areas are most pertinent to re‐establishing native deepwater fishes: life history bottlenecks, population and metapopulation dynamics, matching fish phenotypes to stocking sites, and propagation and stocking methods.

Spatial scales of variance in abundance of intertidal species: effects of region, dispersal mode, and trophic level

Determination of the pattern of variation in population abundance among spatial scales offers much insight into the potential regulating factors. Here we offer a method of quantifying spatial variance on a range of scales derived by sampling of irregularly spaced sites along complex coastlines. We use it to determine whether the nature of spatial variance depends on the trophic level or the mode of dispersal of the species involved and the role of the complexity of the underlying habitat. A least-cost distance model was used to determine distances by sea between all pairs of sites. Ordination of this distance matrix using multidimensional scaling allowed estimation of variance components with hierarchical ANOVA at nested spatial scales using spatial windows. By repeatedly moving these spatial windows and using a second set of spatial scales, average variance scale functions were derived for 50+ species in the UK rocky intertidal. Variance spectra for most species were well described by the inverse power law (1/fbeta) for noise spectra, with values for the exponent ranging from 0 to 1.1. At higher trophic levels (herbivores and carnivores), those species with planktonic dispersal had significantly higher beta values, indicating greater large- than small-scale variability, as did those on simpler coastlines (southwestern England and Wales vs. western Scotland). Average abundance and proportional incidence of species had the strongest influence on p values, with those of intermediate abundance and incidence having much greater large-scale variance (beta approximately 0.5) than rare or ubiquitous species (beta approximately 0).

Seasonal effects of density on territory occupation by males of the satyrine butterfly Paryphthimoides phronius (Butler 1867)

Territorial defense in butterflies may be related to both population density and climatic conditions. If these factors change throughout the year, males are expected to adaptively adjust their behavior in order to maximize reproductive success. In this study, we analyzed the annual dynamics of territory occupation by males of the satyrine butterfly Paryphthimoides phronius at a mildly seasonal subtropical site in southeastern Brazil. We investigated the relationship between the number of defended sites, number of males disputing mating areas, proportion of males adopting alternative mate-locating tactics, and the proportion of time invested in territorial disputes with annual variations in temperature and male density. We found little support for the influence of temperature on the dynamics of territory occupation. On the other hand, the number of defended sites increased with male density, whereas the number of males inside each territory, the proportion of satellite males, and the proportion of time spent in territorial disputes were unrelated to variations in population abundance. Territory defense seems to be adopted whenever possible. We conclude that, instead of increasing the number of individuals disputing the same territory during months of high population abundance, males apparently opt to colonize and defend new and, maybe, suboptimal areas.

Variability in Population Abundance is Associated with Thresholds between Scaling Regimes

Discontinuous structure in landscapes may result in discontinuous, aggregated species body- mass patterns, reflecting the scales of structure available to animal communities within a landscape. The edges of these body-mass aggregations reflect transitions between available scales of landscape structure. Such transitions, or scale breaks, are theoretically associated with increased biological variability. We hypothesized that variability in population abundance is greater in animal species near the edge of body- mass aggregations than it is in species that are situated in the interior of body-mass aggregations. We tested this hypothesis by examining both temporal and spatial variability in the abundance of species in the bird community of the Florida Everglades sub-ecoregion, USA. Analyses of both temporal and spatial variability in population abundance supported our hypothesis. Our results indicate that variability within complex systems may be non-random, and is heightened where transitions in scales of process and structure occur. This is the first explicit test of the hypothetical relationship between increased population variability and scale breaks.