Fluctuations In Abundance Research Articles

Resonance in Physiologically Structured Population Models.

Ecologists have long sought to understand how the dynamics of natural populations are affected by the environmental variation those populations experience. A transfer function is a useful tool for this purpose, as it uses linearization theory to show how the frequency spectrum of the fluctuations in a population's abundance relates to the frequency spectrum of environmental variation. Here, we show how to derive and to compute the transfer function for a continuous-time model of a population that is structured by a continuous individual-level state variable such as size. To illustrate, we derive, compute, and analyze the transfer function for a size-structured population model of stony corals with open recruitment, parameterized for a common Indo-Pacific coral species complex. This analysis identifies a sharp multi-decade resonance driven by space competition between existing coral colonies and incoming recruits. The resonant frequency is most strongly determined by the rate at which colonies grow, and the potential for resonant oscillations is greatest when colony growth is only weakly density-dependent. While these resonant oscillations are unlikely to be a predominant dynamical feature of degraded reefs, they suggest dynamical possibilities for marine invertebrates in more pristine waters. The size-structured model that we analyze is a leading example of a broader class of physiologically structured population models, and the methods we present should apply to a wide variety of models in this class.

Biotic and abiotic drivers of dispersion dynamics in a large-bodied tropical vertebrate, the Western Bornean orangutan.

Understanding of animal responses to dynamic resource landscapes is based largely on research on temperate species with small body sizes and fast life histories. We studied a large, tropical mammal with an extremely slow life history, the Western Bornean orangutan (Pongo pygmaeus wurmbii), across a heterogeneous natural landscape encompassing seven distinct forest types. Our goals were to characterize fluctuations in abundance, test hypotheses regarding the relationship between dispersion dynamics and resource availability, and evaluate how movement patterns are influenced by abiotic conditions. We surveyed abundance in Gunung Palung National Park, West Kalimantan, Indonesia, for 99 consecutive months and simultaneously recorded weather data and assessed fruit availability. We developed a Bayesian hierarchical distance sampling model to estimate population dispersion and assess the roles of fruit availability, rainfall, and temperature in driving movement patterns across this heterogeneous landscape. Orangutan abundance varied dramatically over space and time. Each forest type was important in sustaining more than 40% of the total orangutans on site during at least one month, as animals moved to track asynchronies in fruiting phenology. We conclude that landscape-level movements buffer orangutans against fruit scarcity, peat swamps are crucial fallback habitats, and orangutans' use of high elevation forests is strongly dependent on abiotic conditions. Our results show that orangutans can periodically occupy putative-sink habitats and be virtually absent for extended periods from habitats that are vitally important in sustaining their population, highlighting the need for long-term studies and potential risks in interpreting occurrence or abundance measures as indicators of habitat importance.

Ихтиофауна прибрежной зоны Чёрного моря в районе бухты Ласпинская (Крым)

В настоящее время в Чёрном море протекают процессы осолонения и изменения среднегодовой температуры, которые уже обусловили естественное расселение различных представителей фауны Средиземноморского бассейна и Индийского океана и привели к изменению видового состава и структуры сообществ рыб, населяющих прибрежную зону Крымского полуострова. Вследствие этого возникла необходимость в изучении современного состава ихтиофауны и в оценке показателей её видового богатства и разнообразия. Бухта Ласпинская выбрана в качестве модельного полигона на основании следующих причин: относительно невысокий уровень антропогенной нагрузки; принадлежность части её акватории к особо охраняемым природным территориям и отсутствие рыбопромысловой деятельности прибрежными ставными орудиями лова; постоянный свободный заход пелагических видов рыб; наличие разнообразных биотопов; плавный переход глубин. Вышеперечисленные особенности бухты позволяют оценить наличие рыб разных экологических групп и обеспечивают условия для проведения мониторинга. Исследование выполняли в весенне-осенние периоды 1990–1994 и 2017–2018 гг. Материал собирали сетными орудиями лова, крючковыми снастями и ловушками. Постановку сетей проводили на разных глубинах перпендикулярно и параллельно берегу в дневное (10:00–18:00) и ночное (18:00–06:00) время. Также осуществляли визуальные наблюдения. Всего зарегистрировано 70 видов рыб. Из них 14 ранее не были отмечены в данном районе; пять из них [сальпа Sarpa salpa (Linnaeus, 1758), красноротый бычок Gobius cruentatus Gmelin, 1789, лысун Бата Pomatoschistus bathi Miller, 1982, зелёная морская собачка Parablennius incognitus (Bath, 1968) и четырёхполосый хромогобиус Chromogobius quadrivittatus (Steindachner, 1863)] являются недавними вселенцами, активно распространяющимися в Чёрном море только на протяжении последних 15–20 лет. Бόльшая часть проанализированных видов (64) — морские эвригалинные рыбы. Солоноватоводная группа представлена тремя аборигенными для Чёрного моря видами — бычком-рыжиком Ponticola eurycephalus (Kessler, 1874), бычком-кругляком Neogobius melanostomus (Pallas, 1814) и бычком-мартовиком Mesogobius batrachocephalus (Pallas, 1814). Среди проходных рыб зарегистрированы севрюга Acipenser stellatus Pallas, 1771 и два вида семейства сельдевых — черноморский пузанок Alosa tanaica (Grimm, 1901) и сельдь черноморско-азовская проходная Alosa immaculata Bennett, 1835. Установлено, что сезонная динамика видового разнообразия рыб изучаемой акватории связана с изменением численности локальных скоплений ставриды Trachurus mediterraneus (Steindachner, 1868). В апреле — мае, во время подхода данного вида на мелководье для нагула и размножения, индексы имеют наименьшие значения; в августе, когда численность ставрид уменьшается, отмечены максимальные значения.

Drought effects on invertebrate metapopulation dynamics and quasi-extinction risk in an intermittent river network.

Ecological communities can remain stable in the face of disturbance if their constituent species have different resistance and resilience strategies. In turn, local stability scales up regionally if heterogeneous landscapes maintain spatial asynchrony across discrete populations-but not if large-scale stressors synchronize environmental conditions and biological responses. Here, we hypothesized that droughts could drastically decrease the stability of invertebrate metapopulations both by filtering out poorly adapted species locally, and by synchronizing their dynamics across a river network. We tested this hypothesis via multivariate autoregressive state-space (MARSS) models on spatially replicated, long-term data describing aquatic invertebrate communities and hydrological conditions in a set of temperate, lowland streams subject to seasonal and supraseasonal drying events. This quantitative approach allowed us to assess the influence of local (flow magnitude) and network-scale (hydrological connectivity) drivers on invertebrate long-term trajectories, and to simulate near-future responses to a range of drought scenarios. We found that fluctuations in species abundances were heterogeneous across communities and driven by a combination of hydrological and stochastic drivers. Among metapopulations, increasing extent of dry reaches reduced the abundance of functional groups with low resistance or resilience capacities (i.e. low ability to persist in situ or recolonize from elsewhere, respectively). Our simulations revealed that metapopulation quasi-extinction risk for taxa vulnerable to drought increased exponentially as flowing habitats contracted within the river network, whereas the risk for taxa with resistance and resilience traits remained stable. Our results suggest that drought can be a synchronizing agent in riverscapes, potentially leading to regional quasi-extinction of species with lower resistance and resilience abilities. Better recognition of drought-driven synchronization may increase realism in species extinction forecasts as hydroclimatic extremes continue to intensify worldwide.

Temporal consistency in interactions among birds, ants, and plants in a neotropical savanna

Interactions among animals and plants are key to understanding seed dispersal, plant regeneration and plant community patterns. These interactions can be dynamic, with changes of species and functional roles across space and time. Despite fluctuations in species abundances and resources over time being the rule in natural communities, most studies approach plant–frugivore interactions as temporally static. We documented changes in bird and ant species in interactions with plants producing carbohydrate‐ (Miconia rubiginosa) or lipid‐rich diaspores (Xylopia aromatica) comparing two fruiting seasons 15 years apart in a savanna in southeastern Brazil. We tested if abundance and body size of dispersal vectors (birds and ants) affected the frequency of interactions and the quantitative effectiveness of seed dispersal (QTC). Rich bird (26 species) and ant (18 genera) assemblages interacted with the diaspores. A core of bird and ant taxa was temporally consistent, and responsible for most seed removal across the two years for both plants. Temporal transience was more common for sporadic partners of interactions, and for species with similar functional roles. Abundance and body size of birds affected the interspecific contributions to QTC. Large‐bodied birds dispersed large quantities of seeds of our relatively small‐seeded plants, even if their visits were sporadic. For ants, variations in temperature and rainfall across time seems more important in driving variations in the contributions to QTC. The combined effect of birds and ants in the same system helps to stabilize the temporal fluctuations in the amount of seeds dispersed. However, ants alone are unlikely to replace the functional roles of vertebrate dispersers. Even though species in the assemblage change either their quantitative contribution to seed dispersal or their presence or absence in the interaction network, species persisting in interaction over time are the most important quantitative partners for plants.

RELATIONSHIP OF PRECIPITATION AND HABITAT TO THE SPATIAL AND TEMPORAL ABUNDANCE OF AEDES ATLANTICUS AND AEDES INFIRMATUS IN ST. JOHNS COUNTY, FLORIDA

The purpose of this study was to perform descriptive and inferential analyses to better understand the presence of the abundant mosquito species Aedes atlanticus and Aedes infirmatus in St. Johns County, northeastern Florida. Historical surveillance data (2010-2019) obtained from Anastasia Mosquito Control District of St. Johns County, St. Augustine, FL, was organized to graph temporal mosquito abundance trends and inverse distance weighted (IDW) interpolation was used to map spatial distribution patterns of mosquitoes. Precipitation and habitat composition were investigated as spatiotemporal predictors of mosquito abundance using Pearson’s correlation statistics. There were considerable and inconsistent fluctuations in the population abundance of Ae. atlanticus and Ae. infirmatus across and within individual surveillance seasons during the last decade. Precipitation was significantly associated with total county-wide mosquito population counts by season (Ae. atlanticus, R = 0.810, p = 0.005; Ae. infirmatus, R = 0.850, p = 0.002), while the association with weekly mosquito population trends was inconsistently significant across species, lag time, and years. The proportion of surrounding land covered by upland forest, water, and agriculture was associated with species abundance at the spatial level of individual trap sites. Overall, the results identify that Ae. atlanticus and Ae. infirmatus share a spatiotemporal relationship and are similarly impacted by rainfall and habitat type. Findings of the study might help to inform improved surveillance by integrating IDW estimation maps with current district resources and improved knowledge of species’ ecology.

Historical Demographic Processes Dominate Genetic Variation in Ancient Atlantic Cod Mitogenomes

Ancient DNA (aDNA) approaches have been successfully used to infer the long-term impacts of climate change, domestication, and human exploitation in a range of terrestrial species. Nonetheless, studies investigating such impacts using aDNA in marine species are rare. Atlantic cod (Gadus morhua), is an economically important species that has experienced dramatic census population declines during the last century. Here, we investigated 48 ancient mitogenomes from historical specimens obtained from a range of archeological excavations in northern Europe dated up to 6,500 BCE. We compare these mitogenomes to those of 496 modern conspecifics sampled across the North Atlantic Ocean and adjacent seas. Our results confirm earlier observations of high levels of mitogenomic variation and a lack of mutation-drift equilibrium—suggestive of population expansion. Furthermore, our temporal comparison yields no evidence of measurable mitogenomic changes through time. Instead, our results indicate that mitogenomic variation in Atlantic cod reflects past demographic processes driven by major historical events (such as oscillations in sea level) and subsequent gene flow rather than contemporary fluctuations in stock abundance. Our results indicate that historical and contemporaneous anthropogenic pressures such as commercial fisheries have had little impact on mitogenomic diversity in a wide-spread marine species with high gene flow such as Atlantic cod. These observations do not contradict evidence that overfishing has had negative consequences for the abundance of Atlantic cod and the importance of genetic variation in implementing conservation strategies. Instead, these observations imply that any measures toward the demographic recovery of Atlantic cod in the eastern Atlantic, will not be constrained by recent loss of historical mitogenomic variation.

Seasonal Abundance and Population Fluctuation of Leucaena Tree Beetle, Acanthoscelides macrophthalmus (Schaeffer) (Coleoptera: Chrysomelidae: Bruchinae) and its Accompaniment Parasitoids

The data presented in this study provide some basic information regarding seasonal abundance and population fluctuation, the influence of temperature and relative humidity, monthly population and emergence percentages, time and peacks number, and emergence ratios of population density of each leucaena pods and seeds beetle, Acanthoscelides macrophthalmus and its accompaniment parasitoids (Dinarmus basalis Rondani and Lyrcus sp.) emerged from infested Leucaena leucocephala trees. Insects are abundant throughout the year. The highest monthly population of beetles recorded during November, followed by May and December, the highest population of parasitoids observed during February, followed by March and January (D. basalis) also January and August (Lyrcus sp.).Nine peaks for beetles are recoded, the higher peak observed at 4th week Nov. followed by 3rd week of May, then 4th week of January, the same number of peaks recorded for D. basalis parasitoid, the highest peak noticed at 3rd week of Jan. and March, whereas Lyrcus sp. parasitoid has 8 peaks, the higher found at 3rd week of Jan.General ratio of insect’s emergence was 1:0.384:0.047 (beetles: Dinarmus: lyrcus). Highest ratios between beetles: parasitoids noticed during February (1:2), July (1:1.774) and March. (1:1.287). The dominant weather factors (MaxTemp., Min.Temp. & RH%.) evidently showed effective changes in the population density of beetles and parasitoids during annual activity months. The correlation between parasitoids and beetles population differed during the different seasons. The current work shows that Dinarmus basalis (26.8% seasonal emergence) and Lyrcus sp. (3.3% seasonal emergence) parasitoids develop within infested leucaena seeds with A. macrophthalmus beetle. Numerous numbers of each beetle (69.9% seasonal emergence) and parasitoids (31.3% seasonal emergence) were observed throughout the year, therefore A. macrophthalmus beetles can be used as a substitute host for mass rearing of D. basalisparasitoids, which are biological agent to control stored seed bruchids.

Influences of submerged plant collapse on diet composition, breadth, and overlap among four crane species at Poyang Lake, China

BackgroundInterannual variation in resource abundance has become more unpredictable, and food shortages have increasingly occurred in the recent decades. However, compared to seasonal fluctuations in resource abundance, the influences of interannual variation in resource abundance on the dietary niches of consumers remain poorly understood. Poyang Lake, China, is a very important wintering ground for the globally endangered Siberian Crane (Leucogeranus leucogeranus), White-naped Crane (Grus vipio), and Hooded Crane (G. monacha), as well as the non-endangered Eurasian Crane (G. grus). Tubers of Vallisneria spp., the dominant submerged macrophytes at Poyang Lake, is an important food for cranes. Nevertheless, submerged macrophytes have experienced serious degradation recently. In this study, we used metabarcoding technology to explore the consequences of Vallisneria tuber collapse on the diet compositions, breadths, and overlaps of the four crane species based on fecal samples collected in winter 2017 (a year with tuber collapse) and winter 2018 (a year with high tuber abundance).ResultsCompared to previous studies, our study elucidates crane diets in an unprecedented level of detail. Vallisneria tubers was confirmed as an important food source of cranes. Surprisingly, the grassland plant Polygonum criopolitanum was also found to be an important food source in the feces of cranes. Agricultural fields were important foraging sites for Siberian Cranes, White-naped Cranes, and Hooded Cranes, providing foods that allowed them to survive in winters with natural food shortages. However, the three crane species preferred natural wetlands to agricultural fields when the abundance of natural foods was high. The abundance of Vallisneria tubers, and probably P. criopolitanum, greatly influenced the dietary compositions, breadths and overlap of cranes. During periods of preferred resource shortage, White-naped Cranes and Hooded Cranes widened their dietary niches, while Siberian Cranes maintained a stable niche width. The dietary niche overlap among crane species increased substantially under conditions of plentiful preferred food resources.ConclusionsOur study emphasizes the superior quality of natural wetlands compared to agricultural fields as foraging habitats for cranes. To provide safer and better foraging areas for cranes, it is urgent to restore the submerged plants at Poyang Lake. While high dietary niche overlap is often interpreted as intense interspecific competition, our study highlights the importance of taking food abundance into account.

A nomadic avian predator displays flexibility in prey choice during episodic outbreaks of rodents in arid Australia.

In environments driven by unpredictable resource pulses, populations of many consumer species experience dramatic fluctuations in abundance and spatial extent. Predator-prey relationships in these acyclic systems are poorly understood in particular with respect to the level of prey specialisation shown by nomadic predators. To understand the dynamics of such a system I examined the response to rodent outbreaks by the letter-winged kite (Elanus scriptus) in the Simpson Desert, Australia; a region that experiences major pulses in primary productivity, driven by unpredictable rainfall events. The kite feeds on small mammals and is the only night-hunting species in the Accipitridae. Letter-winged kites irrupted in the area on only three occasions during 20years of sampling (1999-2019) and remained for a maximum of 20months. Each period of kite occupation occurred only during the increase and/or peak phase of rodent population cycles (which occurred three times during the study). During each period kite diet was dominated by small (10-50g body mass) quadrupedal rodents (Pseudomys australis, P. hermannsburgensis, Mus musculus). Abundance of these species varied across the three outbreaks and kites typically captured them in proportion to availability. The large body mass (134g) long-haired rat (Rattus villosissimus) was abundant during one outbreak but was infrequently consumed. The bipedal spinifex hopping-mouse (Notomys alexis) was within the kites' favoured prey size range (35g) but was consistently avoided. The flexibility in prey selection by letter-winged kites appears to be an important adaptation for survival and reproduction by species exploiting acyclic rodent outbreaks.

Hydrological controls on oviposition habitat are associated with egg‐laying phenology of some caddisflies

Abstract Seasonal variation in resource availability can have strong effects on life histories and population densities. Emergent rocks (ERs) are an essential oviposition resource for multiple species of stream insects. The availability of ERs depends upon water depth and clast size, which vary with discharge and river geomorphology, respectively. Recruitment success for populations may depend on whether peak egg‐laying periods occur at times when ERs are also abundant. For multiple species that oviposit on ERs, we tested whether seasonal fluctuations in ER abundance were concurrent with oviposition phenology. We also tested whether high discharge drowned ERs for sufficiently long periods to preclude egg laying, and whether this problem varied between rivers differing in channel morphology and particle size distribution. We obtained a continuous timeseries of water level (WL) measured every 30 min for 2 years at sites on three rivers in south‐eastern Australia with similar hydrology but different geomorphology. A relationship between WL and ER numbers was determined empirically at each site and these relationships were used to predict ER availability over the 2 years. Egg masses of 10 species of caddisflies were enumerated each month for a year in one river to establish oviposition phenology. Abundance of ERs was inversely related to discharge in all three rivers. ERs were most abundant during autumn and scarce during spring. Site‐specific geomorphology resulted in skewed or multimodal distributions of ER abundance each year. Between years, catchment‐scale hydrometeorology mediated patterns of ER availability, despite the close proximity of sites. Temporal variance in ER availability was not consistently correlated with mean WL or WL variance. ER variance increased with WL variance, when WL was below a threshold equivalent to mean annual WL. Above this threshold, most ERs were likely to be submerged. Oviposition phenology varied strongly among the 10 species of caddisflies, with egg‐laying ranging from 1–2 months to year‐round. Temporal variations in ER and egg mass abundance were not correlated for most species. Below a threshold minimum number of ERs, egg masses were highly crowded onto the few available ERs, which is evidence that ERs were in short supply. For five species, high egg mass abundance was positively associated with periods of the year when the time above the threshold number of ERs was high. Unusually, two species laid most egg masses during winter and when the time above this threshold was short. Three species showed no association between egg mass abundance and time above this threshold; two of these species laid eggs year‐round. Regional hydrometeorology controlled the availability of ERs, but between‐river differences were sufficient to deliver different outcomes in the availability of oviposition sites between years and seasons. Caddisflies were rarely prevented from laying eggs but periods when ERs were in short supply created crowding, which may be associated with negative fitness effects on hatching larvae. Geomorphological controls on availability of oviposition resources may have strong implications for the coexistence of species that overlap in egg‐laying phenology. ​

Pre-fledging quality and recruitment in an aerial insectivore reflect dynamics of insects, wetlands and climate.

Wetland systems, including shallow palustrine ponds, are hotspots for emergent aquatic insects but are globally threatened by land-use practices and climate change. Loss of insects is hypothesized as a key driver of population declines in aerial insectivores, but studies of climate-driven fluctuations in pond abundance during wet-dry periods and aerial insects on nestling quality and apparent recruitment are lacking. Using tree swallow (Tachycineta bicolor) data spanning 14-28years we evaluated: (1) whether nestling quality based on pre-fledging (~ 12days old) body mass changed over the time series; (2) how annual estimates of aerial insect biomass and variability, temperature, and pond abundance influenced nestling mass; and (3) whether the annual number of recruits produced was related to the annual mean mass of nestlings, aerial insects, and pond abundance in their year of hatching. Average nestling body mass varied annually but no long-term temporal trends were detected. Nestlings were heavier when raised during periods of stable insect biomass, warmer temperatures, and higher pond abundance. Pond abundance consistently had strong effects on nestling mass and inter-annual apparent recruitment, suggesting that this metric provides a complementary index of either higher prey abundance or higher-quality aquatic prey. Overall, pre-fledging quality and annual recruitment of nestling tree swallows reflects dynamic interannualchanges in climate, pond availability, and aerial insect food supply. Our findings further suggest the abundance of ponds in this semi-arid prairie landscape is likely a strong predictor of regional population stability in tree swallows and possibly other ecologically similar species.

Evolution and significance of clay minerals in the Esna Shale Formation at Dababiya area, Luxor, Egypt

The Esna Shale Formation is broadly distributed in Egypt and one of the most of its important clay deposits. These deposits in the Dababiya area, Luxor region were subjected to intensive laboratory investigations (XRD, IR, and SEM analyses). The bulk and clay mineralogy of this formation varies from one layer to the next and comprises the phyllosilicates, calcite as principal minerals with remarkable amounts of quartz, feldspars dolomites, and anhydrite. Fluorapatite, pyrite, schaurteite, despujolsite, goethite, and halite are present in some beds but minor quantities. The clay mineralogy consists of smectite (41%), sepiolite-palygorskite (28%), illite (13%), smectite/illite mixed layers (13%), and kaolinite (6%). Smectite was differentiated into three species: nontronite (21%), Na-and Ca-montmorillonites (13%), and beidellite (8%). Smectites are dioctahedral with a typical fully turbostratic stacking mode and crystallite sizes varying from 2 to 3 nm. The detrital input is the dominant aspect responsible for distributing clay minerals in these marine sediments. The presence of shallow Paleogene constrained basins between arose land areas in Egypt, favorable to the neoformation of palygorskite and sepiolite, It indicates that most of the fibrous clay minerals present in this part of the Tethys could have formed in these coastal basins and that their presence is an indication of aridity. By transcending global sea level that occurred at the end of the Paleocene, the nonappearance of kaolinite at the Dababiya area (southern Egypt) and its richness at the Wadi Nukhul Section (Sinai, Egypt) no relationship is shown between differences in kaolinite abundance and sea level fluctuations during this period. Six units of clay mineral species were distinguished throughout this formation reflecting their evolution.

Common bottlenose dolphin (Tursiops truncatus) interaction with fish farms in the Gulf of Ambracia, western Greece

Abstract Marine aquaculture, and its fast‐growing development, has the potential for wider environmental, ecosystem, and biodiversity impacts. This study assesses the impact of fish farming on a bottlenose dolphin (Tursiops truncatus) population within the Gulf of Ambracia (western Greece) between 2007 and 2018. Two different study areas were defined in order to investigate differences on occurrence, abundance, behaviour, and seasonal fluctuations between them: a ‘control area’, in the north‐western side of the Gulf; and a ‘fish farm area’, in the south west, where the highest density of fish farm cages is found. A total of 169 daily surveys were dedicated to the control area and 74 days were dedicated to the fish farm area, yielding 104 and 37 sightings, respectively. Both the probability of detecting dolphins (U = 6,763.000, P = 0.002) and the group sizes (U = 578.000, P < 0.001) were smaller around fish farms. Seasonality analyses were restricted to 2007–2008, as this was the period with year‐round effort. Results revealed that dolphins were more frequently seen around fish farms in the winter (Kruskal–Wallis test, P = 0.036). From the 40 identified individuals that were re‐sighted at least 10 times during the study period, 21 used the fish farm area less than expected according to sampling effort, and 10 of them were never observed in that area (binomial test, P < 0.05). The results revealed an impact of fish farms on the distribution of bottlenose dolphins in the Gulf of Ambracia. This information should be taken into consideration when defining ecosystem‐based management measures within the management plan, which is currently in preparation for this Natura 2000 site.

Quantifying abundance trends and environmental effects on a population of queen scallop Aequipecten opercularis targeted by artisanal fishers in a coastal upwelling area (Ría de Arousa, NW Spain) using a Bayesian spatial model

Queen scallop Aequipecten opercularis, is exploited by small-scale trawlers in separated aggregations along the east Atlantic coast and the Mediterranean Sea. However, population performance is poorly known. Here, we combine official information and on-board observers’ data over two decades to study the fishery ecology of an aggregation occurring in a coastal upwelling system (Ría de Arousa, NW Spain). Annual landings fluctuated around a mean of 170 tons while beam trawlers declined at a rate of 11 vessels per decade. A hurdle Bayesian spatial model fitted to observers’ catch and effort data showed that the probability of occurrence and abundance of the species increased with fishing effort and decreased in sandy bottoms. Moreover, abundance increased with upwelling intensity and decreased with continental runoff and along the fishing season. Furthermore, occurrence was higher in the inner part of the embayment while abundance increased in the central channel. The predicted index of standardized abundance correlated with the trend in landings, and year-to-year fluctuations in abundance were negatively and positively related to upwelling intensity and net primary production, respectively, during the spawning and settlement period.

Response of intertidal barnacles to air temperature: Long-term monitoring and in-situ measurements

A twenty-five year (1994–2018) survey at 10 rocky sites within Lough Hyne Marine Reserve (SW Ireland) showed that, despite considerable spatial and temporal patchiness, three barnacle species (Chthamalus stellatus, Semibalanus balanoides, and Austrominius modestus) declined in overall abundance in the early 2000s, particularly at three sites. There was no clear response of A. modestus or C. stellatus to the cold winters of 2010 and 2011. In 2004, however, S. balanoides declined suddenly, but showed a slight recovery after the cold winter of 2010 to maintain sparse populations in the lough, but remained abundant outside the lough. A fourth species, Chthamalus montagui, showed a different pattern, with wide fluctuations in abundance but no overall decline. Changes in the Atlantic Multidecadal Oscillation may have influenced the overall composition of barnacle populations. Rising maximum air temperatures, resulting in high body temperatures recorded for A. modestus even during mild days, are suggested to have impacted the barnacle populations as a result of the prolonged aerial exposure times caused by the lough's asymmetric tidal pattern.

Sequence stratigraphy of the Late Oligocene carbonate system on the Xisha Islands in the South China Sea

Sedimentological, paleontological, and mineralogical data from core XK-1 in the Xisha Islands allow for a detailed lithologic and sequence stratigraphical analysis on the Late Oligocene interval in the Xisha Islands. In this study, 13 facies are differentiated and a depositional model of a carbonate-dominated system is established. Variation in facies stacking patterns, changes in composition and grain size, and fluctuation in abundance of terrigenous matter are analyzed, and sequence division is interpreted at two different hierarchal levels. In the Late Oligocene interval of core XK-1, a total of thirteen small-scale sequences and three medium-scale sequences are divided out, with one medium-scale sequence mainly composed of four small-scale sequences. Based on the available timing constraints, the durations of the small- and medium-scale sequences are estimated to be 100 kyr and 400 kyr, respectively. These small-scale and medium-scale sequences are thus inferred to be primarily controlled by orbital forcing. The long-term evolution between 24.3 and 23.6 Ma was controlled by the eustatic sea level, while it was more influenced by a tectonic subsidence linked to the ridge jump event in the South China Sea after 23.6 Ma. Our study demonstrates that eustatic sea level fluctuations had a significant impact on the initial carbonate development at various scales in the northern South China Sea, while tectonic movement also played an important role in shaping the secular carbonate evolution.

«Wrong fish» or wrong hypotheses: what happens to nekton of the Pacific waters at Kuril Islands?

A phenomenon of undulating fluctuations of nekton abundance in the Kuroshio system is discussed on example of japanese sardineSardinops melanostictus, as the most abundant and the most fluctuating species. The so-called «sardine epochs» are distinguished according to this species abundance. The last such epoch ended in the early 1990s. Since 2014, structural changes occurred again in the nekton communities of the Pacific waters off Kuril Islands, caused by expansion of southern fish and squid species, primarily japanese sardine and chub mackerelScomber japonicus, and decreasing in abundance of japanese anchovyEngraulis japonicusand sauryCololabis saira. The scope of these changes allowed Russian fishermen to resume the fishery on japanese sardine and chub mackerel in the Russian exclusive economic zone since 2016. Annual catch of Japanese sardine increased steadily from 6,700 t in 2016 to 315,500 t in 2020. Over these 5 years, Russian fishermen landed 531,700 t of sardine and 167,900 t of chub mackerel. However, many Russian fishery forecasters believe that these reconstructions is only a «rehearsal» of the upcoming «sardine epoch», being based on formal climatic indices, without delving into the mechanisms of abundance fluctuations. The authors note that new «sardine epochs» cannot be predicted as completely similar to the previous ones. Several hypotheses on causes of the beginning and end of japanese sardine blooms are considered critically, and the conclusion is made that mechanisms which determine its year-classes strength are still unclear, as well as the reasons of undulating fluctuations of this species and some other nekton species abundance, because of high complexity of this problem.

EMBED: A Low Dimensional Reconstruction of Gut Microbiome Dynamics Based on Ecological Normal Modes

The gut microbiome is well-established to be a significant driver of host health and disease. Longitudinal studies involving high-throughput sequencing technologies have begun to unravel the complex dynamics of these ecosystems, and quantitative frameworks are now being developed to better understand their organizing principles. Dimensionality reduction can offer unique insights into gut bacterial dynamics by leveraging collective abundance fluctuations of multiple bacteria driven by similar underlying ecological factors. However, methods providing lower-dimensional representations of gut microbial dynamics both at the community and individual taxa level are currently missing. To that end, we develop EMBED: Essential Microbiome Dynamics. Similar to normal modes in structural biology, EMBED infers ecological normal modes (ECNs), which represent the unique set of orthogonal dynamical trajectories capturing the collective behavior of a community. We show that a small number of ECNs accurately describe gut microbiome dynamics across data sets that encompass dietary changes and antibiotic-related perturbations. Importantly, we find that ECNs often reflect specific ecological behaviors, providing natural templates along which the dynamics of individual bacteria may be partitioned. Collectively, our results highlight the utility of dimensionality reduction approaches to understanding the dynamics of the gut microbiome and provide a framework to study the dynamics of other high-dimensional systems as well.

Big bats binge bad bugs: Variation in crop pest consumption by common bat species

As generalist predators, insectivorous bats exploit fluctuations in prey distribution and abundance. A more nuanced understanding of the influence of bats on arthropod pests requires documentation of the pest species bats consume and of the conditions associated with variation in rates of pest consumption. Here, we used high-throughput metabarcoding of DNA extracted from bat feces to investigate diets of 180 bats representing three Vespertilionidae species common to the southeastern US, a region dominated by agriculture and pine plantations. We detected 23 species of agricultural pests in bat diets, including pests responsible for severe economic damage, such as Helicoverpa zea, Spodoptera frugiperda, Chloridea virescens and Chrysodeixis includens. Incidence of pest consumption was high: 61% of all bats had consumed at least one agricultural pest species, with each bat consuming an average of 1.7 pest species. The likelihood of consumption of pests to row crops and the average size of pests consumed varied by bat species, with a large foliage-roosting species (Lasiurus seminolus) consuming a greater variety of pest species and pest species larger in size than smaller crevice, cavity, and cave roosting bat species (Nycticeus humeralis, Myotis austroriparius). Likelihood of pest consumption also varied among sampling periods (season) and among bats of different sizes (as reflected by wing length and mass). Overall, likelihood of pest consumption was higher in the late summer season than during spring or early summer, and higher among larger bats than smaller bats. Bat characteristics and seasonality were generally more effective than geographic features and weather conditions in predicting pest consumption patterns. Strategies for enhancing pest consumption services by bats in agroecosystems should strive to maintain and enhance diverse bat populations on a landscape scale by protecting and augmenting roost structures appropriate for each species. Our finding of widespread pest consumption by bats contributes to mounting evidence worldwide of the important role bats play in agricultural systems and highlights the value of incorporating bat conservation into integrated pest management programs globally.