Relative Abundance Of Individuals Research Articles

Airborne imagery does not preclude detectability issues in estimating bird colony size

Aerial images obtained by drones are increasingly used for ecological research such as wildlife monitoring. Yet detectability issues resulting from animal activity or visibility are rarely considered, although these may lead to biased population size and trend estimates. In this study, we investigated detectability in a census of Malagasy pond heron Ardeola idae colonies on the island of Mayotte. We conducted repeated drone flights over breeding colonies in mangrove habitats during two breeding seasons. We then identified individuals and nests in the images and fitted closed capture-recapture models on nest-detection histories. We observed seasonal variation in the relative abundance of individuals, and intra-daily variation in the relative abundance of individuals—especially immature birds—affecting the availability of nests for detection. The detection probability of nests estimated by capture–recapture varied between 0.58 and 0.74 depending on flyover days and decreased 25% from early to late morning. A simulation showed that three flyovers are necessary to detect a 5–6% decline in colonies of 50 to 200 nests. These results indicate that the detectability of nests of forest-canopy breeding species from airborne imagery can vary over space and time; we recommend the use of capture-recapture methods to control for this bias.

Keeping safe and fed: large heterospecific shorebird flocks to decrease intraspecific competition

Shorebirds join cohesive flocks for safety. The joining of individuals of several species in large heterospecific flocks can optimise individual vigilance and foraging. However, a large number of conspecific individuals in flocks may deplete food resources and increase intraspecific competition. In the present study, we argue that Nearctic–Neotropical migratory shorebird species join large heterospecific flocks in a balanced number as a way of controlling intraspecific competition. We recorded monospecific and heterospecific flocks in urban beaches from southeastern Brazil and annotated the species richness and the number of individuals per bird species per flock. Besides, we recorded the number of people around shorebird flocks to examine any relationship with flock size. We also recorded the foraging rate of the semipalmated plover Charadrius semipalmatus, a common migrant species in the region, as a species model to test competition and vigilance. We hypothesised that this species would exhibit a low foraging rate in scenarios with high intraspecific competition (i.e. large flocks with a high number of conspecifics) and high density of people, which may disturb birds. In the initial results, the density of people did not influence size of monospecific and heterospecific flocks; heterospecific flocks were larger than monospecific flocks, and heterospecific flocks increased in size by the addition of more species rather than more individuals of the same species. These data reflect a decrease in the relative abundance of individuals per species. Additionally, the semipalmated plover foraging rate was reduced in monospecific flocks, flocks with a high relative abundance (and total number) of the specific individuals and flocks surrounded by a high density of people. All these results indicate that shorebirds may adjust flock composition and size according to preferred foraging conditions, i.e. large and balanced heterospecific flocks with less intraspecific competition and less vigilance to potential predators in wintering areas.

Fluctuations in age structure and their variable influence on population growth

Abstract Temporal fluctuations in growth rates can arise from both variation in age‐specific vital rates and temporal fluctuations in age structure (i.e. the relative abundance of individuals in each age‐class). However, empirical assessments of temporal fluctuations in age structure and their effects on population growth rate are relatively rare. Most research has focused on understanding the contribution of changing vital rates to population growth rates and these analyses routinely assume that: (a) populations have stable age distributions, (b) environmental influences on vital rates and age structure are stationary (i.e. the mean and/or variance of these processes does not change over time), and (c) dynamics are independent of density. Here we quantified fluctuations in age structure and assessed whether they were stationary for four populations of free‐ranging vertebrates: moose (observed for 48 years), elk (15 years), tawny owls (15 years) and grey wolves (17 years). We also assessed the extent that fluctuations in age structure were useful for predicting annual population growth rates using models which account for density dependence. Fluctuations in age structure were of a similar magnitude to fluctuations in abundance. For three populations (moose, elk, owls), the mean and the skew of the age distribution fluctuated without stabilizing over the observed time periods. More precisely, the sample variance (interannual variance) of age structure indices increased with the length of the study period, which suggests that fluctuations in age structure were non‐stationary for these populations – at least over the 15‐ to 48‐year periods analysed. Fluctuations in age structure were associated with population growth rate for two populations. In particular, population growth varied from positive to negative for moose and from near zero to negative for elk as the average age of adults increased over its observed range. Non‐stationarity in age structure may represent an important mechanism by which abundance becomes non‐stationary – and therefore difficult to forecast – over time‐scales of concern to wildlife managers. Overall, our results emphasize the need for vertebrate populations to be modelled using approaches that consider transient dynamics and density dependence and that do not rely on the assumption that environmental processes are stationary. A free Plain Language Summary can be found within the Supporting Information of this article.

Fish assemblage structure and spatial gradients of diversity in a large tropical reservoir, Panchet in the Ganges basin, India.

Fish assemblage structure in Panchet, a large tropical reservoir along river Damodar, major tributary of river Ganga in India, was studied along the spatial gradient of the impoundment. Fish samples were collected bimonthly from October 2014 to September 2016. Fish community structure in terms of species composition, relative abundance, and trophic and conservation status was recorded. Spatial fish diversity was analyzed from riverine, transitional, and lacustrine zones. Sixty-two fish species were recorded wherein the family Cyprinidae dominated in number of species (26) followed by Bagridae (5). Shannon diversity index, evenness index, and species richness did not reveal significant variation (p > 0.05) across different zones. Relative abundance of individuals and species richness were maximum in the transitional zone and minimum in the lacustrine zone. Multi-dimensional scaling of fish assemblage revealed similar pattern in the riverine and transitional zones. Trophic guild of fishes indicated dominance of carnivorous species followed by planktivores. Conservation status (IUCN 2017.3) showed 4 fish species in Near Threatened category. The study suggests conservation of fish habitats to maintain diversity and sustained production. The baseline information generated in the study will be beneficial for monitoring the alteration in fish assemblage, conservation of fish diversity, and management planning.

Fusing Biodiversity Metrics into Investigations of Daily Life: Illustrations and Recommendations With Emodiversity.

Functionalist emotion and ecological systems theories suggest emodiversity-the variety and relative abundance of individuals' emotion experiences-is beneficial for psychological and physical health and may change with age. This paper examines and provides recommendations for operationalization of diversity-type intraindividual variability (IIV) constructs using intensive longitudinal data, and demonstrates the utility of emodiversity by examining its links to physical health moderated by mean levels of emotion and age. Using data from a daily diary study of 138 adults (age 40 to 65 years), we consider how item selection, response scale, choice of diversity index, and number of occasions enable/constrain mapping to theory, measurement reliability, and empirical inquiry. Item selection and response scale had limited influence on rank-order differences in diversity. Reliable measurement (r ≥ .8) required a minimum of 6 to 12 occasions depending on choice of index, theoretical conception, study design, and distribution of diversity scores. The empirical findings suggest mean level of negative affect, rather than age, moderates the relation between negative emodiversity and health. This study provides recommendations for the calculation of diversity-type IIV constructs and illustrates the potential for study of emodiversity to contribute to understanding of successful aging.

Composition and dynamics of the fungal population in a typical Phaeozem luvico in Argentina

AbstractThe decomposer soil community maintains the arable soil ecosystem for the nutrient turnover. Here, we studied the dynamics of the soil fungal populations in a typical Phaeozem luvico in Argentina and related it to the management practices. Soil samples (at 0–10 cm depth) were collected from a field cultivated with wheat, at different sampling times: at post-harvest, before sowing, and at tillering. The relative abundance of individuals in the population on Nash Snyder and Oxgall agar media was assessed as colony forming units (CFU). The fungal population was classified by numerical taxonomy at the different sampling times. The highest values of CFU g−1 of soil were found at post-harvest under reduced tillage and differed significantly from those at conventional tillage. The genera Trichoderma, Fusarium, Aspergillus, Penicillium, and Fusarium oxysporum were present in the largest number of samples and discriminated the fungal community between times. This discrimination could be related to alterati...

Sodium channel expression in the copepod Acartia hudsonica as a function of exposure to paralytic shellfish toxin (PST)

Local adaptation of the copepod Acartia hudsonica to toxic Alexandrium spp. is associated with degree of historical co-exposure. Recently, a novel mutation in the sodium channel in A. hudsonica was hypothesized to be the mechanism of adaptation to toxic Alexandrium; all copepods express both types of sodium channels. We tested the hypothesis that mutant sodium channel expression in A. hudsonica individuals corresponded to historical co-exposure to A. fundyense. Female A. hudsonica were sampled from historically exposed (Maine) and naïve (Connecticut and New Jersey) populations to A. fundyense, throughout the 2011 season of growth of A. hudsonica. There were no consistent differences in wild-type: mutant isoform ratios nor in the relative abundance of individuals that predominately express one type of isoform, either through time within a population or among populations or over time within each location. We also tested the hypothesis that expression of the mutant sodium channel isoform in A. hudsonica should increase during the progression of a toxic Alexandrium bloom. Sodium channel expression was compared before, during, and after the 2011 toxic Alexandrium spp. bloom in Northport Harbor, NY. Moreover, the relative expression of the mutant isoform increased slightly after the peak of the toxic Alexandrium spp. bloom; however, there was no simultaneous increase in individuals that predominately express mutant channel isoforms. Overall, there was little evidence in support of our hypotheses. Other mechanisms must be responsible for the observed geographic differences in adaptation of copepods to toxic Alexandrium.

Macro‐ and microenvironmental factors affecting tyre‐breeding flies (Insecta: Diptera) in urbanised areas

Abstract Urbanisation is often considered a main driver of changes in the structure of insect communities. To assess macro‐ and microenvironmental factors determining the occurrence and community structure of fly larvae in water‐filled artificial containers, a total of 13 848 individuals were collected among 1380 water‐filled tyres inspected along an urbanisation gradient in temperate Argentina. According to the best generalized linear mixed model obtained for fly occurrence, the probability of finding an occupied tyre was greater in large tyres with high water volume, containing organic matter and located in shaded conditions under high vegetation cover in backyards. Regarding macroenvironmental factors, fly occurrence decreased as the urbanisation level increased. The anova revealed a negative effect of urbanisation on all variables used to characterize the fly community structure. The number of occupied tyres, the relative abundance of individuals, the species richness, and the Shannon diversity index showed consistent patterns with significantly lower values at high urbanisation level. Community composition also varied along the urbanisation gradient, revealing three major groups of fly species: those found exclusively in highly urbanised areas, those found in the less urbanised sites, and those collected across the entire gradient.

Global patterns in predator–prey size relationships reveal size dependency of trophic transfer efficiency

Predator-prey body size relationships influence food chain length, trophic structure, transfer efficiency, interaction strength, and the bioaccumulation of contaminants. Improved quantification of these relationships and their response to the environment is needed to parameterize food web models and describe food web structure and function. A compiled data set comprising 29582 records of individual prey eaten at 21 locations by individual predators that spanned 10 orders of magnitude in mass and lived in marine environments ranging from the poles to the tropics was used to investigate the influence of predator size and environment on predator and prey size relationships. Linear mixed effects models demonstrated that predator-prey mass ratios (PPMR) increased with predator mass. The amount of the increase varied among locations and predator species and individuals but was not significantly influenced by temperature, latitude, depth, or primary production. Increases in PPMR with predator mass implied nonlinear relationships between log body mass and trophic level and reductions in transfer efficiency with increasing body size. The results suggest that very general rules determine dominant trends in PPMR in diverse marine ecosystems, leading to the ubiquity of size-based trophic structuring and the consistency of observed relationships between the relative abundance of individuals and their body size.

Responses in Bird Communities to Wildland Fires in Southern California

There is a growing body of literature covering the responses of bird species to wildland fire events. Our study was unique among these because we investigated the effects of large-scale wildland fires on entire bird communities across multiple vegetation types. We conducted avian point counts during the breeding seasons for two years before and two years after the Cedar and Otay Fires in 2003 in southern California. Our balanced sampling effort took place at two sites, one low-elevation and one high-elevation, each containing replicate stations (burned and unburned) within five vegetation types: chaparral, coastal sage scrub, grassland, oak woodland, and riparian. Although fire caused some degree of change in the vegetation structure at all of our impacted survey points, we found that the post-fire shrub and tree cover was significantly lower in only two of the vegetation types within the low-elevation site, coastal sage scrub and chaparral. We found no significant changes in cover at the high-elevation site. Using univariate and multivariate analyses, we tested whether the fires were associated with a change in bird species diversity, community structure, and the relative abundance of individuals within a species. We found that species diversity changed in only one circumstance: it increased in coastal sage scrub at the low-elevation site. Multivariate analyses revealed significant differences in the post-fire bird community structure in the low-elevation chaparral, low-elevation coastal sage scrub, and the high-elevation grassland communities. Vegetation characteristics altered by fire, such as decreases in shrub and tree cover, influenced the changes we observed in the bird communities. The relative abundance of some species (lazuli bunting [Passerina amoena] and horned lark [Eremophila alpestris]) significantly increased after the fires, while other species declined significantly (Anna’s hummingbird [Calypte anna], wrentit [Chamaea fasciata], and bushtit [Psaltriparus minimus]). We detected mixed results for the spotted towhee (Pipilo maculatus), which increased in burned chaparral and declined in burned coastal sage scrub within the low-elevation site. We suggest that the observed responses of birds to these fires may be attributed to: (1) the availability of nearby unburned refugia, (2) the continued suitability of post-fire vegetation at the study sites, and (3) the generally high mobility of this taxon.

Seasonal abundance of nonbreeding Piping Plovers on a Georgia barrier island

Although breeding populations of Piping Plovers are well studied, their winter distribution is less clear. We studied the seasonal abundance of nonbreeding Piping Plovers (Charadrius melodus) during the winters of 2003–2004 and 2004–2005 on Little St. Simons Island (LSSI), Georgia. Our objectives were to determine the relative abundance of individuals from three breeding populations at LSSI, and identify possible differences among populations in arrival time, winter movements, or departure time. We observed up to 100 Piping Plovers during peak migration, and approximately 40 plovers wintered at LSSI. From July 2004 to May 2005, approximately 20% of the Great Lakes breeding population used LSSI. Plovers were not present at LSSI during June. All breeding populations of Piping Plovers had similar patterns of temporal occurrence on LSSI, suggesting no need for population-specific management plans at this site. Our results suggest that LSSI is among the most important wintering sites on the Atlantic coast for Piping Plovers, especially for individuals from the endangered Great Lakes population. SINOPSIS Aunque las poblaciones reproductivas del chorlitejo picocorto (Charadrius melodus) son bien estudiadas, la distribucion invernal de esta especie es relativamente poco conocida. Estudiamos la abundancia estacional de Charadrius melodus durante los inviernos del 2003–2004 y 2004–2005 en Little St. Simons Island (LSSI) en Georgia. Nuestros objetivos fueron determinar la abundancia relativa de individuos de tres poblaciones reproductivas en LSSI e identificar las posibles diferencias entre poblaciones en fecha de llegada, movimientos durante el invierno, y fecha de salida. Observamos hasta 100 individuos de Charadrius melodus durante el pico de migracion y aproximadamente 40 individuos pasaron el invierno en LSSI. Desde Julio 2004 hasta Mayo 2005, aproximadamente 20% de la poblacion reproductiva “Great Lakes” utilizo LSSI. La especie no estuvo presente en LSSI en Junio. Todas las poblaciones reproductivas de esta especie tuvieron similares patrones temporales de ocurrencia en LSSI, cual es una posible indicacion de que este sitio no requiere de planes de manejo especificas a una poblacion. Nuestros resultados indican que LSSI es uno de los sitios mas importantes para esta especie en la costa Atlantica durante el invierno, especialmente para individuos de la poblacion “Great Lakes”, cual esta en peligro de extincion.

Diversity and Seasonality of Male Euglossine Bees (Hymenoptera: Apidae) in Central PanamÁ

Seasonal changes in species richness, composition, and abundance of male euglossine bees were determined by weekly censusing of individuals attracted to 16 chemical baits. Bee populations were monitored for >1 yr in the lowland tropical moist forest of seasonally dry Barro Colorado Island (BCI), Panama. Male euglossine bees were also censused one every 4 wk at three nearby mainland sites, two at low elevation, and one at a middle—elevation locality. Among the lowland sites the male euglossine bee communities varied little; species composition, dominance ranks, species' phenological profiles, and seasonal changes in bee abundance were similar. Male bee populations at these sites were probably influenced by factors of similar timing and magnitude. In contrast, the male bee community of the upland locality differed from lowlands in species composition and timing of seasonal fluctuations in bee abundance. At all census sites the male euglossine bee community had four genera (Eulaema, Euglossa, Eufriesia, and Exaerete), 33—44 censused species, and low evenness of species abundance. On BCI, the relative abundance of individuals in the four genera was not constant throughout the year. Species richness and bee abundance were correlated; both fluctuated seasonally, and peaked in the early wet season. However, species composition, evenness, and dominance ranks were virtually nonseasonal, so some structural continuity existed in the male euglossine bee community.

Seasonal and Diel Flight Periodicities of Rice Field Hydrophilidae

Seasonal flight patterns and diel flight periodicities of Berosus styliferus Horn, Cercyon praetextatus (Say), Enochrus cuspidatus (LeConte), E. hamiltoni (Horn), E. pygmaeus pectoralis (LeConte), Hydrophilus triangularis Say, Tropisternus columbianus Brown, and T. lateralis humeralis Mots. were monitored using a rotary net machine and a blacklight trap, in conjunction with measurements of temperature, wind speed, and time of sunrise and sunset. Seasonal variations in date of initiation of flight, relative abundance of individuals, and time of peak flight activity existed among the species. Peak flight typically occurred the hour following sunset, with a second, smaller peak at sunrise. Temperatures ranging from 11° to 34° C and wind speeds to 20 kph were extreme conditions under which flight occurred, although most flights were recorded during periods with a more narrow temperature range (20° – 22° C) and on calm nights. B. styliferus preferred the lower temperatures and later evening flight which is characteristic of an early season colonizer. H. triangularis demonstrated both a thermal dependence in relation to flight and a broader time of flight activity, possibly due to its size and range.

Ecology of Recent Foraminifera in Northern Florida Keys

Foraminifera live in the following environments in the Florida Keys area: Florida Bay, water 0-10 feet deep; the back-reef, water mostly 15-30 feet deep but ranging from 0 to 40 feet deep; the reef, locally awash at low tide but extending seaward to a depth of about 60 feet; and the fore-reef, water deeper than 60 feet. The boundaries between the back-reef and the reef and between the reef and the fore-reef environments are transitional. The Florida Bay environment is characterized by great variations in the abundance of the Miliolidae, Peneroplidae, Nonionidae, and Rotaliidae, and by the absence of the Amphisteginidae, Textulariidae, Lagenidae, and Buliminidae. Variations in the Florida Bay fauna suggest sorting. The Amphisteginidae and Buliminidae represent families present in the back-reef environment which are not found in Florida Bay. The Peneroplidae and Amphisteginidae are most abundant and the Nonionidae are least abundant on the outer reef patches. The fore-reef environment is characterized by the appearance of the Cassidulinidae and the rise of the Anomalinidae to a position of minor abundance. Angulogerina, Bulimina, Uvigerina, and Reusella do not occur at depths much shallower than 150 feet. These environments may be recognized and differentiated by noting the relative abundance of individuals belonging to the various families without regard to the species or genera involved.

The Omori Shell Mounds

IN NATURE, vol. xxi. p. 350, is a review of my memoir on “The Omori Shell Mounds” by Fredk. V. Dickins. I do not now heed the spirit in which it is written, nor would I deem it worthy of notice did it not occur in the pages of your widely-read magazine. One expects in a reviewer some knowledge of the subject he reviews. Mr. Dickins, by a series of mistakes, betrays his ignorance of the whole matter. The extraordinary blunder he makes regarding the Ainos has already been promptly corrected by a Japanese gentleman residing in London. It is charitable to assume that Mr. Dickins has not lived in Japan, otherwise he would not, in common with so many of his countrymen, commit the wilful blunder of calling the principal city of the empire by its wrong name. On the other hand, it is impossible he could have seen the Omori deposits, otherwise he would not make another blunder by expressing his belief that they have been completely swept away, when in truth but a small portion of them have been removed. He says: "These mounds consist for the most part of shells, little, if at all, distinguishable from what are still found in abundance along the shores of the Gulf of Yedo". Had he taken the trouble to read the memoir he attempted to review he would have seen that all the species occurring in the mounds vary in size, proportion of parts, and relative abundance of individuals from similar species living along the shores to-day. That some species extremely abundant in the mounds are scarcely met within the vicinity, while one species has never been found within 400 miles of Omori; indeed, it belongs to a different zoological province!