Population ecology of the temperate reef fish Pseudolabrus celidotus Bloch & Schneider (Pisces: Labridae). I. Factors influencing recruitment

Recruitment of Pseudolabrus celidotus Bloch & Schneider was measured at 10 reef areas over four seasons (1977–1980) in north-eastern New Zealand. These encompassed six different habitat types, defined on the basis of their major physical and biological features. Recruitment differed among habitats and years, but spatial differences were more pronounced than temporal changes. Shallow broken rock (SBR) habitats dominated by macrophytic brown algae consistently had the highest recruitment. Six areas within SBR habitats were censused over three seasons (1979–1981). Even within this one habitat type, most of the variation in numbers was explained by spatial effects. Furthermore, the differences in recruitment between sites remained fairly constant because changes between years were similar in magnitude and direction.An adult removal experiment established that recruitment was independent of adult numbers. Macroalgae affected recruitment as was demonstrated by an algal removal experiment, which resulted in a marked reduction in recruitment, and an algal addition (via urchin removal) experiment which resulted in an increase. Juvenile densities increased as an exponential function of algal biomass per unit area, but the relationship was dependent on depth. Recruitment reached higher levels in shallow habitats (< 8 m) than deeper ones, despite a similar range of algal biomass.It is suggested that there are several factors operating at the time of or shortly after settlement, which result in spatial differences in recruitment on a very small scale. The observed temporal variation may be due to a different set of factors operating prior to settlement, and may have effects measurable over a considerably broader spatial scale.     

Recruitment limitation in a tropical intertidal barnacle: Tetraclita panamensis (Pilsbry) on the Pacific coast of Costa Rica

On the central Pacific coast of Costa Rica, populations of Tetraclita panamensis (Pilsbry) were studied to determine the relative importance of pre- and postrecruitment processes in determining patterns of distribution and abundance. Populations at 12 sites on two shores were censused photographically from 1983 to 1985 at 1–3-months intervals, yielding data on recruitment, growth, and mortality. During the 2.5-yr study, recruitment replaced < 24% of the number dying at 10 of the 12 sites. Most populations were sparse and declining. Preemption of settlement was unlikely because bare space was always abundant and recruitment occurred mostly on the shells of adults. Individuals reached a maximum size in 1–3 yr, after which there was little growth. Estimated longevity ranged from 3.6 to 14.7 yr among sites. Mortality was unrelated to submergence, density or the abundance of an important predator, the gastropod Acanthina brevidentata (Wood). Patterns of distribution and abundance among the 12 sites and along the central coast of Costa Rica are probably a function of past variation in recruitment. Many apparently suitable habitats are unoccupied.     

Foraging conditions, tooth wear and herbivore body reserves: a study of female reindeer

Several aspects of the life history of reindeer (Rangifer tarandus) are related to the nutritional condition of the animals. Moreover, compensatory growth and fattening in summer decreases with age. The interaction of tooth wear and the standing crop of lichens on age-related variation in body size and tissue reserves was examined to evaluate the proximate causes of density-dependent food limitation on life history parameters in female reindeer. Studies in nine semi-domesticated free-ranging reindeer herds showed that molar height depended on the mean standing crop of terrestrial lichens in winter habitats. The extent of tooth wear had the strongest effect on body reserves among the oldest females (11–14 years). This indicates that severe tooth wear limits the animals′ ability to process food efficiently and, hence, to maintain their body reserves. Both tooth wear and the biomass of lichens influenced body mass in old females, probably because on heavily exploited winter ranges reindeer had to use higher proportions of lower-ranking coarser foods, especially dwarf shrubs. Received: 1 December 1997 / Accepted: 13 July 1998     

The maintenance of shore-level size gradients in an intertidal snail (Littorina sitkana)

Summary The size of many intertidal animals varies with tidal height. These size gradients could be produced by growth or survival varying with tidal height, or by animals moving to a preferred tidal level. The body size of the snail, Littorina sitkana, increases steadily with tidal height in rocky high intertidal habitats of British Columbia. To determine how size gradients were maintained in L. sitkana, I quantified how growth, survival, and snail movement varied with tidal height. I studied populations of L. sitkana found on sheltered pebble beach and exposed basaltic shelf habitats. Mark-recapture studies and experimental transplants showed that growth could not have produced the size gradients because snail growth rates in both habitats were as fast or faster at low tidal levels (where the snails were the smallest) than at high tidal levels. However, survival rates were lowest at low tidal levels. On pebble beaches, this was due to size selective predation on large snails by the pile perch, Rhacochilus vacca. On basaltic shelves, heavy wave action at low tidal levels may have caused the poor survival rates. Transplanted snails moved homeward on pebble beaches, but not on basaltic shelves. Reduced survival rates at low tidal levels cause size gradients in both habitats, and snail movement helps to maintain size gradients on pebble beaches.     

Recruitment of shore crabsCarcinus maenas on tidal flats: Mussel clumps as an important refuge for juveniles

During the late summer and early fall, juvenile shore crabs (Carcinus maenas L.) occurred in high abundances in mussel clumps scattered on tidal flats of the Wadden Sea. Abundances were much lower on bare tidal flats without mussel clumps and decreased substantially from July to November, whereas numbers in mussel clumps remained high. Large crabs left the tidal flats in early fall, whereas juveniles undertook tidal migrations only in the late fall. In March very few shore crabs were found in the intertidal area. The size of juvenile shore crabs living between mussels did not increase significantly during fall. On the bare tidal flats surrounding the mussels, a size increase was observed. Mussel beds and mussel clumps serve as a spatial refuge for the early benthic phases of juvenile shore crabs. Between mussels they can hide effectively from their epibenthic predators. Juvenile shore crabs do not leave the intertidal area and the mussel habitats before their major predators have left the area. Mussel clumps scattered over the tidal flats may be a critical refuge for juvenile shore crabs settling on tidal flats. Intensified efforts in mussel culturing in the European Wadden Sea during recent decades may have caused an increased abundance of mussel clumps on tidal flats, thus enhancing habitat availability for some mussel-clump inhabitants.     

Distribution and population dynamics of the limpet Patella aspera (Lamarck) in Bantry Bay

The population ecology of Patella aspera (Lamarck) was studied as part of an oil pollution baseline study. Contrary to earlier reports, P. aspera appears to be a protandrous hermaphrodite. Maturation of the gonads began in May-June and spawning took place in October. Variations in density, standing crop, and mean size were related to exposure to wave action and tidal level. The low shore in extreme exposure may be designated as the centre of P. aspera's range; abundance is high but biomass and mean size are reduced. Higher on the shore, and in reduced exposure to wave action, P. aspera attains a greater mean size and biomass, but is eventually replaced by P. vulgata L. Two main factors are adduced as being critical to competition between the two species. In terms of tidal level, P. aspera is less tolerant of desiccation than P. vulgata, while in terms of the exposure-shelter gradient, P. aspera appears to have a much less variable growth rate. P. aspera may be defined, therefore, as a non-migratory, low shore, specialist species, highly adapted to a specific set of environmental conditions, but lacking the ability to adapt to others.     

Benefits of adjacent habitat patches to the distribution of a crayfish population in a hydro-dynamic wetland landscape

Aquatic macrophyte patches are natural features of wetland ecosystems that serve as habitat for aquatic animals. Previous studies suggest animal densities in Everglades, USA, wetlands are generally less numerous in sawgrass ridges than in deeper lily sloughs. We studied the density distribution of a population of Procambarus fallax in ridge and slough habitat types over a 2-year period, spanning two wet–dry cycles and estimated growth and survival rates under flooded conditions to understand comparative value of each to the crayfish population. Procambarus fallax individuals inhabited and recruited in both marsh habitats. During periods of high water, crayfish densities were similar in both habitats; however, densities in both habitats varied seasonally, leading us to postulate some degree of population redistribution in response to fluctuating water depths. Analysis of size distributions over time revealed juveniles in both habitats and two major recruitment periods each year; distinct juvenile cohorts were present in early winter (Nov–Dec) and mid-summer (July–Aug). An in situ experiment of juvenile growth demonstrated that slough habitat type supported faster growth over ridge habitat. To understand habitat-specific mortality risk, a tethering study during flooded conditions indicated that relative predation risk by aquatic predators was greater in sloughs for all sizes and higher for smaller individuals in both habitats. The comparative importance of ridge and slough balances growth potential and survival probability during flooded conditions. This is the first study through time and across both habitat types analyzing the distribution and size structure of P. fallax population in the Everglades.     

Comparative benthic plant ecology by SCUBA-monitored quadrats

The feasibility of permanent benthic quadrats checked by SCUBA divers was tested. Stations were set up on the bottom of six representative aquatic habitats, both marine and inland, including oligotrophic and eutrophic ponds, river, coastal lagoon, estuary, and open marine coast. Data include physical-chemical factors, species composition, number and height of shoots, and general observations. From volume/length constants, the standing crops per quadrat were calculated. Seasonal changes in environmental factors and plant standing crop are parallel-plotted for the six habitats, thus providing comparative information on stations. Benthic diel periodicity and light intensity periodicity at various depths were investigated also. In all habitats, maximum standing crop occurred in July and August, but species composition varied considerably. Length of time the water temperature exceeded 15C did not correlate with standing crop. Dissolved oxygen was never deficient, even under ice; and diurnal changes were slight. Light was diminished under ice, but 4–60 ft-c were recorded in midwinter. Lenght of day is about 2 hours shorter at 20 ft than at 6 ft. Onset of vernal benthic growth seems correlated more closely with increase in light intensity than with temperature. The permanent quadrats monitored by divers proved feasible in all habitats tested, and directly comparable data were obtained.Supported in part by a grant from the National Science Foundation.     

Descriptive phenology and seasonality of a Canadian brown-water stream

A phenological-type synthesis was attempted for 10 years of limnological data of a brown-water stream of Alberta, Canada. The objectives were to predict the normal occurrence of seasonal events in the stream and to formulate indices upon which to base general stream management strategies. The stream supports a diverse chironomid fauna (109 species); and four taxa, chironomids, ostracods and the ephemeropteransLeptophlebia cupida andBaetis tricaudatus, account for 61% of the total yearly fauna by numbers. There are two obvious major seasons: a 7 month ice-free season (ca 15 April–15 November) and a 5 month winter season. Based on numerical classification of physical and chemical parameters, the ice-free season is separated into spring (April and May), summer (June, July and August) and autumn (September and October) seasons; and these four seasons can serve as the basis for describing biological seasonality. There are few detectable periodic events during the long, 5-month winter season: flow and water temperature are relatively constant and at minimum values. There are no reproductive periods for species studied; no new generations appear; drift densities are at minimum values; and for most taxa, little growth takes place in winter. Some of the important phenological events of the three ice-free seasons include: (1) a total emergence, hence reproductive, period of 6 months (April–September) for aquatic insects studied, with the largest number of taxa reproducing in late June and early July; (2) a 31/2 month period (late April–early August) when water temperatures are on the rise (log phase of total degree days curve), with maximum rate increase in May, maximum rate decrease in October, and maximum water temperature values in early August; (3) a completely green (trees and marsh grasses) watershed of less than 2 months (late June–early August); (4) a leaf-drop period of 11/2 months (September–mid October), with maximum litter-fall rate in early September; (5) maximum discharge in April; (6) minimum standing crop by numbers in April and maximum numbers in September; (7) maximum daily drift and drift densities (all taxa) in August; (8) maximum impounding effect of beaver dams in September; (9) maximum aquatic macrophyte standing crop in September; and (10) maximum ‘potential’ food resources (detritus of aquatic macrophyte and terrestrial leaf origin) in mid October.     

Das asymptotische Wachstum der Fische — ein Nonsens?

Considering an incomplete growth curve of the codGadus morhua,Knight (1968) questioned the asymptotic curvature of growth in fishes, which easily may be shown in complete growth curves illustrating the attainment of maximum size. It is also possible to calculate maximum size employing theFord-Walford formula. Maximum size, calculated in this manner, may also be used in theBertalanffy function. For other mathematical growth formulations different maximum sizes would be obtained. The numerical value of the maximum size depends upon the mathematical interpretation of the growth process. Therefore it always represents a mathematical parameter without biological meaning. It is shown that data ofKetchen (Forrester 1966) on growth in ♂ ♂ of the flat fishEopsetta jordani may be much better represented by the new growth formula (Krüger 1965) than by theBertalanffy function.     

Recruitment requirements of the rare and threatened Juncus atratus

The long-term persistence of populations and species depends on the successful recruitment of individuals. The generative recruitment of plants may be limited by a lack of suitable germination and establishment conditions. Establishment limitation may especially be caused by the competitive effect of surrounding dense vegetation, which is believed to restrict the recruitment success of many plant species to small open patches (‘safe sites’). We conducted experiments to clarify the roles of germination and seedling establishment as limiting processes in the recruitment of Juncus atratus Krock., a rare and threatened herbaceous perennial river corridor plant in Central Europe. Light intensity had a positive effect on germination. However, some seedlings emerged even in total darkness and the germination rate at 1% light intensity was more than half of that at 60% light intensity. Seedling establishment in the field after 10 weeks was 30% on bare ground, but it was close to zero in grassland. Establishment in the growth chamber after 8 weeks was close to 75% for seedlings that germinated underwater, but only about 35% for seedlings that germinated afloat. Furthermore, establishment decreased with flooding duration on bare ground, but increased with flooding duration in grassland. These data indicate that establishment, rather than germination, is a critical life stage in Central European populations of J. atratus. They furthermore indicate that the competition of surrounding vegetation for water limits seedling establishment under field conditions without flooding, largely restricting establishment success to bare ground habitats. In contrast, grassland is more suitable for the recruitment of J. atratus than bare ground under prolonged flooding. Grassland may facilitate the establishment of J. atratus seedlings during long-lasting floods by supplying oxygen to the soil through aerenchyma. The shift from competition to facilitation in grassland occurred after 30 days of flooding, i.e. within the ontogeny of individual plants. The specific recruitment requirements of J. atratus may be a main cause of its rarity in modern Central Europe. In order to prevent regional extinction of J. atratus, we suggest maintaining or re-establishing natural hydrodynamics in the species’ habitats.     

Succession stage variation in population size in an early-successional herb in a peri-urban forest

Urban and peri-urban forests incur high anthropogenic pressures (e.g. recreational activities, artificialization, and eutrophication). Plant species from early-successional, transient, forest habitats, often characterized by a short life span and a persistent seed bank in the soil may differ from late-successional species in key-factors for population persistence. This study investigated variation in population size and seedling recruitment for different forest succession stages and three consecutive years in Centaurium erythraea, an early-successional biennial herb, occurring in a peri-urban forest of Brussels urban zone (Belgium). Forest succession stage had a significant impact on C. erythraea population size and on its temporal fluctuation. Populations in closing vegetation (evolving to late-succession stages) showed small population sizes and a low number of recruits compared to populations from stable early-succession vegetation and clearcuts. The number of recruits was the highest after clearcutting, which can be related to the expression of the soil seed bank. Populations showed year-to-year variation in size (flowering individuals and recruits), even in stable (over three years) early-succession forest vegetation. In the absence of disturbance changing succession stage, population size is expected to depend on seed set of the previous years and subsequent seedling recruitment, which can be affected by environmental stochasticity. Opening gaps in the herbaceous vegetation may stimulate seedling recruitment, also in unoccupied patches where “cryptic” seed populations are present in the soil. Forest path and road verges, despite their potential negative impact on forests, can constitute refuge habitats for early-successional forest plant species. Their management should involve the preservation of these species.     

Invertebrate dispersal and habitat heterogeneity: Expression of biological traits in a seagrass landscape

Seagrass meadows harbour diverse faunal assemblages, but the relative importance of landscapes attributes, settlement processes and biological traits of individual species for recruitment patterns is poorly understood. To quantify the influence of habitat heterogeneity on larval, juvenile and adult post-larval dispersal, invertebrates (> 125 µm) were collected in benthic settlement traps at five occasions (June-August) in three habitats; continuous seagrass, seagrass patches and bare sand. The study was carried out by SCUBA diving in a subtidal (2.5 m depth) seagrass landscape dominated by Zostera marina L. in the Baltic Sea. Traps collected totally > 30 taxa, with non-significant effects of habitat on species richness and total abundance. Total number of invertebrates exhibited strong temporal variability, probably driven by wind-induced bedload and water column transport. Surprisingly, traps located in small (< 12 m²) patches contained on average almost twice as many individuals as traps located in the continuous vegetation. Dominating taxa such as nematodes, copepods, and oligochaetes were found in similar densities across the landscape. In contrast, location within the landscape had strong effects on bivalve settlement and redistribution patterns, resulting in significantly lower densities in continuous vegetation compared to patches and bare sand. A biological trait analysis indicated that semi-mobile taxa with annual protracted direct development, and short-distance dispersal are probably of higher importance for the community assembly process in this environment than long-distance larval dispersal. Results suggest that seagrass landscapes are highly dynamic environments, characterized by time and species-specific effects of landscape attributes on animal dispersal and recruitment. A conceptual model illustrating interactions between settling larvae and landscape heterogeneity is presented.     

Multiple processes regulate long-term population dynamics of sea urchins on Mediterranean rocky reefs

We annually monitored the abundance and size structure of herbivorous sea urchin populations (Paracentrotus lividus and Arbacia lixula) inside and outside a marine reserve in the Northwestern Mediterranean on two distinct habitats (boulders and vertical walls) over a period of 20 years, with the aim of analyzing changes at different temporal scales in relation to biotic and abiotic drivers. P. lividus exhibited significant variability in density over time on boulder bottoms but not on vertical walls, and temporal trends were not significantly different between the protection levels. Differences in densities were caused primarily by variance in recruitment, which was less pronounced inside the MPA and was correlated with adult density, indicating density-dependent recruitment under high predation pressure, as well as some positive feedback mechanisms that may facilitate higher urchin abundances despite higher predator abundance. Populations within the reserve were less variable in abundance and did not exhibit the hyper-abundances observed outside the reserve, suggesting that predation effects maybe more subtle than simply lowering the numbers of urchins in reserves. A. lixula densities were an order of magnitude lower than P. lividus densities and varied within sites and over time on boulder bottoms but did not differ between protection levels. In December 2008, an exceptionally violent storm reduced sea urchin densities drastically (by 50% to 80%) on boulder substrates, resulting in the lowest values observed over the entire study period, which remained at that level for at least two years (up to the present). Our results also showed great variability in the biological and physical processes acting at different temporal scales. This study highlights the need for appropriate temporal scales for studies to fully understand ecosystem functioning, the concepts of which are fundamental to successful conservation and management.     

The growth of Kandelia candel seedlings in mangrove habitats of the Zhangjiang estuary in Fujian, China

Propagules of Kandelia candel collected from the Zhangjiang estuary were planted in mangrove habitats along the intertidal gradient. The rooting rates of K. candel propagules varied spatially. The lowest rate occurred in Avicennia marina forest (69.7%). The rates were higher in K. candel forest (90.0%), at the fringe of the mangrove forest (89.3%) and on the bare tidal flat outside the mangrove forest (82.7%). After one year, the survival rates of seedlings planted under A. marina forest, K. candel forest, at the fringe of the mangrove forest, and on the bare tidal flat were 13.7%, 54.7%, 76.0%, and 34.7%, respectively. Among the surviving K. candel seedlings, those at the fringe of the mangrove forest and on the bare tidal flat had greater height, stem diameter, leaf number, leaf area, and biomass than those under A. marina and K. candel forests. These results demonstrated that establishment and growth of K. candel seedlings occurred successfully at the fringe of the mangrove forest, but were the worst under A. marina forest. The performance of K. candel seedlings was independent of physico-chemical characters of sediment. However, interspecies competition, propagule predation by insects and crabs, and the incident light had significant effects on seedling survival and growth.     

Autumnal Biomass and Potential Productivity of Salt Marsh Fungi from 29° to 43° North Latitude along the United States Atlantic Coast

It has been established that substantial amounts of fungal mass accumulate in standing decaying smooth cordgrass (Spartina alterniflora) marshes in the southeastern United States (e.g., in standing decaying leaf blades with a total fungal organic mass that accounts for about 20% of the decay system organic mass), but it has been hypothesized that in marshes farther north this is not true. We obtained samples of autumnal standing decaying smooth cordgrass from sites in Florida to Maine over a 3-year period. The variation in latitude could not explain any of the variation in the living fungal standing crop (as determined by ergosterol content) or in the instantaneous rates of fungal growth (as determined by acetate incorporation into ergosterol at a standard temperature, 20°C), which led to the conclusion that the potential levels of fungal production per unit of naturally decaying grass are not different in northern and southern marshes. Twenty-one percent of the variation in the size of the living fungal standing crop could be explained by variation in the C/N ratio (the higher the C/N ratio the smaller the fungal crop), but the C/P ratio was not related to the size of the fungal crop. Instantaneous rates of fungal growth were negatively related to the size of the living fungal crop (r = −0.35), but these rates were not correlated with C/nutrient ratios. The same two predominant species of ascomycetes (one Phaeosphaeria species and one Mycosphaerella species) were found ejecting ascospores from standing decaying smooth cordgrass blades at all of the sites examined from Florida to Maine.     

Anthropogenic subsidies mitigate environmental variability for insular rodents

The exogenous input of nutrients and energy into island systems fuels a large array of consumers and drives bottom-up trophic cascades in island communities. The input of anthropogenic resources has increased on islands and particularly supplemented non-native consumers with extra resources. We test the hypothesis that the anthropogenic establishments of super-abundant gulls and invasive iceplants Carpobrotus spp. have both altered the dynamics of an introduced black rat Rattus rattus population. On Bagaud Island, two habitats have been substantially modified by the anthropogenic subsidies of gulls and iceplants, in contrast to the native Mediterranean scrubland with no anthropogenic inputs. Rats were trapped in all three habitats over two contrasting years of rainfall patterns to investigate: (1) the effect of anthropogenic subsidies on rat density, age-ratio and growth rates, and (2) the role of rainfall variability in modulating the effects of subsidies between years. We found that the growth rates of rats dwelling in the non-subsidized habitat varied with environmental fluctuation, whereas rats dwelling in the gull colony maintained high growth rates during both dry and rainy years. The presence of anthropogenic subsidies apparently mitigated environmental stress. Age ratio and rat density varied significantly and predictably among years, seasons, and habitats. While rat densities always peaked higher in the gull colony, especially after rat breeding in spring, higher captures of immature rats were recorded during the second year in all habitats, associated with higher rainfall. The potential for non-native rats to benefit from anthropogenic resources has important implications for the management of similar species on islands.     

Phenology of annual kelp Eckloniopsis (Phaeophyceae,Laminariales) forest on a Diadema barren in Uchiura Bay,Central Pacific Coast of Honshu,Japan

On the southern coast of Uchiura Bay, central Pacific, Japan, Diadema barrens have expanded since the 1980s but Eckloniopsis radicosa (annual kelp endemic to Japan) has remained in deeper waters (>10 m in depth). Phenology of the kelp was studied on isolated boulders from December 2011 for a year. Young sporophytes appeared in December and rapid growth from April brought the maximum blade length (83.3?±?13.9 cm) and width (56.8?±?12.7 cm) and standing crop (7.4 kg m^?2) in May and June, respectively. Sorus formation began in June and spore release occurred from July to September. Blade length decreased from August and disappeared in November though holdfast remained. The unique holdfast-like spiny ball was found to provide habitats for mobile animals; its forests have an important role to maintain the biodiversity on barrens. During the period, water temperature was between 14.6 and 27.8 °C, salinity was stable around 34–35?‰, and nutrients were never depleted. Tolerance to large and frequent fluctuation of water temperature (7 °C in a day), rapid growth in winter to spring, and occurrence on limited boulders in soft substrata may be the reasons for the success in the maintenance of its forest in Diadema barrens.     

Positive relationship between fruit removal by animals and seedling recruitment in a tropical forest

Fleshy-fruited plants rely on animal frugivores to disperse their seeds, and seed removal by frugivores may leave an imprint on seedling recruitment. However, to what extent plant–frugivore interactions are related to seedling recruitment has rarely been quantified at the community level, especially in species-rich tropical forests. In this study, we tested the effect of different plant traits on fruit removal by frugivores and tested the relative importance of fruit removal, plant traits and abiotic factors for seedling recruitment. We quantified plant–frugivore interactions of 22 fleshy-fruited plant species consumed by 56 diurnal frugivore species, and counted the number of seedlings that emerged along an elevational gradient in the Colombian Andes. We measured a set of plant traits (i.e., crop size; fruit size; seed load and mass; fruit nutritional contents), estimated the density of adult plants and recorded relevant abiotic factors (light, temperature and humidity). We found that fruit removal by frugivores was positively associated with crop size, but negatively associated with fruit length and unrelated to seed load and fruit nutritional content. Seedling densities were positively related to the density of adult plants, seed mass and fruit removal by animals. We found no relationship between abiotic factors and seedling recruitment. Our results indicate that fruit abundance and morphology are important determinants of fruit removal and that fruit removal is positively associated with seedling recruitment accounting for effects of species abundance and plant traits. We conclude that plant traits shape fruit removal and seedling recruitment at the community level, while these two crucial processes of forest regeneration are directly linked by seed dispersal of animals.     

Mass release effects ofchlorohydra viridissima [Coelenterata] on field populations ofAedes nigromaculis andCulex tarsalis in Kern County,California

European green hydra,Chlorohydra viridissima (Pallas) were tested for adaptability and predation effectiveness in natural habitats ofAedes nigromaculis (Ludlow) andCulex tarsalis Coquillet in Kern County, California from June through December, 1973. Hydra were well adapted to all habitats except Kern River seepage where their adaptability was measured at only 55.6%.Aedes nigromaculis populations were reduced 67.2% in an irrigated pasture in July.Culex tarsalis densities were reduced 33.9% in standing Kern River seepage and 79.2% in duck club ponds from September through December, 1973. TheC. tarsalis larval density in hydra treated duck club ponds remained below an average of 0.5/dip after inoculation in September. Hydra density increased at inoculation sites and significant numbers overwintered at Riverside, California without food. The practical utilization of hydra and their attributes for mosquito control are discussed.