Temporal Variation In Diversity Research Articles

Temporal variation in diversity, abundance and size class structure of planktonic copepods from a tropical estuary

Temporal variation in diversity, abundance and size class structure of planktonic copepods from a tropical estuary

DIVERSIDAD Y ECOLOGÍA DE ABEJAS, AVISPAS DEPREDADORAS Y MARIPOSAS: APORTACIONES DEL CCBA-UADY

<p><strong>Background.</strong> The diversity and ecology of various groups of insects has not yet been fully studied in Mexico. <strong>Objective.</strong> Present a review of the contributions to science, which have been made on the diversity and ecology of bees, predatory wasps and butterflies. <strong>Methodology.</strong> The contributions of scientific articles and book chapters (33) of the Department of Zoology of the Campus of Biological and Agricultural Sciences of the Autonomous University of Yucatán were reviewed. <strong>Main findings</strong>. There is greater knowledge about the diversity of species including new registers, complementary contributions include ecological topics of the species on the lifestyles or eating habits and nesting sites of the species and there are studies about floral fragrances. In addition, in bees, there are contributions on the temporal variation in diversity, the effects of natural and human disturbances on the diversity of species. <strong>Implications.</strong> The knowledge generated is essential to establish conservation strategies due to the importance of these insects as key species in ecosystems. <strong>Conclusion.</strong> The contributions to science are mainly studies on biodiversity, in addition to some contributions from the ecology of the species, which are important for proposals for the sustainable management and conservation of pollinators species, pest controllers, biondicators and for the study of species as a window to climate change.</p>

Temporal variation in diversity and community structure of preimaginal blackflies (Diptera: Simuliidae) in a tropical forest reserve in Malaysia

Blackflies (Diptera: Simuliidae) are ecologically and medically important insects but they have been understudied in Malaysia. Accordingly, a study on the temporal variation in diversity and community structure of preimaginal blackflies was conducted for the first time in Malaysia. A total of 865 preimaginal blackflies were collected in 120 samplings from five streams across three monsoon seasons from February 2018 until January 2019. Ten species were recorded and most frequently collected species were Simulium cheongi, Simulium vanluni and Simulium jeffreyi. Relatively common species were Simulium roslihashimi, Simulium tani complex and Simulium trangense. No significant changes of rainfall was observed between three monsoon seasons as well as the seasons with species and physiochemical parameters except acidity (pH) (P < 0.01). Species relative abundance was varied between seasons, as high value of Shannon index (H) was found in northeast monsoon and lowest in the southwest monsoon. Principal Component Analysis (PCA) of all stream variables revealed two PCs that accounted for 61.4% of the total variance of physicochemical characteristics. Regression analysis revealed that species richness was positively and significantly associated with wider, deeper, faster, low conductivity and larger streambed particle with less canopy cover. Forward logistic regression analysis on three frequently collected species (>20%) indicated that S. vanluni and S. jeffreyi were commonly associated with wider, deeper and fast-flowing streams with low conductivity and larger streambed particle. In contrast, S. cheongi was associated with smaller, slower and small streambed particle. This first extensive bimonthly study has uncovered the species community structure as well as the changes of stream physicochemical parameters over time although they were not greatly and significantly influenced by the monsoon seasons. Species distribution, richness and abundance, however, were highly determined by the stream width, depth and velocity, therefore, were vital in shaping diversity and community structure of preimaginal blackflies.

Importance of Lake Ashenge, a Small Important Bird Area in Northern Ethiopia, to Palaearctic and Other Migratory Birds

Tropical inland lakes harbour a variety of waterbirds and provide a wintering habitat for Palaearctic and other migratory birds. However, the importance of the lakes as a temporary site for migrant bird populations has not been adequately studied. The point count method was used to study waterbird species diversity and abundance in Lake Ashenge, in the semi-arid region of northern Ethiopia, with the main aim to underscore the lake's importance as a stop-over site for Palaearctic and other migratory birds. A total of 36 species belonging to 14 waterbird families were encountered. Fifteen of the species were resident birds, including the endemic Wattled Ibis (Bostrychia carunculata), and 14 of the species were Palaearctic migrants, including the globally Near-Threatened Ferruginous Duck (Ayithya nyroca) and Maccoa Duck (Oxyura maccoa). Significant temporal variation in diversity and abundance was observed during the study period; diversity was highest (Shannon-Wiener H′ = 1.98) in the dry season (December/J...

Temporal vegetation changes in a seasonally dry tropical forest enclave in an ecotonal region between savanna and semiarid zones of Brazil

Seasonally dry tropical forests (SDTFs) comprise a globally significant biome for biodiversity and conservation. Geographically, Brazilian SDTFs are primarily located within the country’s semiarid region (the Caatinga domain) in north-eastern Brazil. However, poorly studied and disjunct SDTF enclaves can occur within other regions, inside other Brazilian phytogeographical domains of vegetation such as savannas (i.e. the Cerrado domain) in central Brazil. These enclaves provide an opportunity to examine natural and non-anthropogenic edge effects on such vegetation. In 2007 and 2014, we studied a 120-ha SDTF enclave in the municipality of Januária in northern Minas Gerais, Brazil, to understand its (1) floristic composition and soil correlates, and (2) temporal variations in diversity, structure and dynamics. Three sets of 10 400-m2 plots were used to compare the vegetation at 0 m (edge), 100 m (middle) and 200 m (inner) into the forest. The edge plots were compositionally dissimilar from the interior plots because of soil fertility and soil textural gradients. Paradoxically also, the inner plots exhibited less stable vegetation-dynamic patterns than did both the middle and the edge plots, possibly owing to natural temporal fluctuations in vegetation dynamics. Overall, the SDTF enclave exhibited high diversity and structural complexity, likely because of its geographical setting within a matrix of savanna. These results highlight a conservation priority for further studies on such SDTF enclaves throughout their range.

The Link between Microbial Diversity and Nitrogen Cycling in Marine Sediments Is Modulated by Macrofaunal Bioturbation.

ObjectivesThe marine benthic nitrogen cycle is affected by both the presence and activity of macrofauna and the diversity of N-cycling microbes. However, integrated research simultaneously investigating macrofauna, microbes and N-cycling is lacking. We investigated spatio-temporal patterns in microbial community composition and diversity, macrofaunal abundance and their sediment reworking activity, and N-cycling in seven subtidal stations in the Southern North Sea.Spatio-Temporal Patterns of the Microbial CommunitiesOur results indicated that bacteria (total and β-AOB) showed more spatio-temporal variation than archaea (total and AOA) as sedimentation of organic matter and the subsequent changes in the environment had a stronger impact on their community composition and diversity indices in our study area. However, spatio-temporal patterns of total bacterial and β-AOB communities were different and related to the availability of ammonium for the autotrophic β-AOB. Highest bacterial richness and diversity were observed in June at the timing of the phytoplankton bloom deposition, while richness of β-AOB as well as AOA peaked in September. Total archaeal community showed no temporal variation in diversity indices.Macrofauna, Microbes and the Benthic N-CycleDistance based linear models revealed that, independent from the effect of grain size and the quality and quantity of sediment organic matter, nitrification and N-mineralization were affected by respectively the diversity of metabolically active β-AOB and AOA, and the total bacteria, near the sediment-water interface. Separate models demonstrated a significant and independent effect of macrofaunal activities on community composition and richness of total bacteria, and diversity indices of metabolically active AOA. Diversity of β-AOB was significantly affected by macrofaunal abundance. Our results support the link between microbial biodiversity and ecosystem functioning in marine sediments, and provided broad correlative support for the hypothesis that this relationship is modulated by macrofaunal activity. We hypothesized that the latter effect can be explained by their bioturbating and bio-irrigating activities, increasing the spatial complexity of the biogeochemical environment.

Heterogeneidad ambiental y su relación con la diversidad y abundancia de la comunidad de peces en un sistema costero del Golfo de México

The coastal lagoons of Veracruz, Gulf of Mexico, include a great variety of biological resources. These resources, especially fish communities, have been barely described and that require more ecological studies. With this aim, this investigation analyzed the spatial and temporal variation of diversity, abundance and assemblages of the fish community and its relationship with physical-chemical parameters of the Chica-Grande coastal system. For this, eight defined sites were monthly sampled for water characteristics and fish community composition (10min hauls of 1 500m2 a shrimp trawl net), between September 2005 and November 2006. The spatial-temporal variation of physical-chemical parameters, allowed the definition of two contrasting environments according to salinity, temperature, transparency, dissolved oxygen and depth gradients. A total of 1 947 fishes were collected for a total weight of 57.88kg. From these, 22 species, 20 genera and 14 families were identified; and four species were new records for the system. As it was detected for the physical-chemical conditions, the diversity of the fish community also showed a spatial gradient, with high values (H'=2.37, D=3.35, J'=0.82) in the brackish habitat, and low ones in freshwater environments. Fish abundance did not show such a marked gradient response, however, it was higher in the freshwater habitat. The highest diversity (H'=2.05) and species richness (D=2.99) was recorded during the North winds ("nortes") months (November-February), while density and biomass were higher (0.034 ind./m2, 1.42g/m2) during the rainy months (July-October). The Importance Value Index (IVI) defined six dominant species accounting for 77.8% of the fish abundance and 87.9% of total catch by weight. The Canonical Correspondence Analysis (CCA) showed that the fish-habitat relationship was explained by 68% of total variance for the two first axes, where salinity, transparency and temperature changes were the most important environmental variables in determining the fish community composition and distribution. In this study, spatial gradients of environmental variables explained the changes in fish species composition and abundance; while the temporal gradients, the fish community structure and its relationship with seasonal patterns of habitat use by the species during their life cycles.

Aquatic Invertebrate Communities of Perennial Pans in Mpumalanga, South Africa: A Diversity and Functional Approach

Perennial pans are a common feature of the Mpumalanga Highveld in South Africa and are increasingly under threat from mining and agricultural activities. Pans are endorheic wetlands that can be perennial or ephemeral in nature. They are widespread in arid and semi-arid regions throughout the world. Although phyllopod crustaceans dominate pan communities in arid regions, the invertebrate communities of perenni al pans have not been well studied. The aim of the current research was to characterise the invertebrate com munities of several pans (both natural and impaired). A combination of taxonomic and functional approaches was followed to study these communities. The macroinvertebrate species diversity of the pans was comparable to similar ecosystems in southern Africa and other parts of the world. Results indicate large spatial and temporal variations in diversity. This variation became less obvious when the analysis was based on biological traits. It was also evident that both coal mining and agricultural activities had an impact on the aquatic invertebrate community structures. These changes were apparent in both the diversity and the biological traits of the invertebrate communities of adjacent pans.

Temporal variation in methanogenic community structure and methane production potential of tropical rice ecosystem

Temporal variations in diversity of methanogenic community and CH4 production potential were analyzed in an Indian tropical rice ecosystem. Laboratory incubations showed that methane production varied from 20.86 to 134.11 μg CH4 g−1 d.w.s. during the two consecutive years, 2009 and 2010. CH4 production potential was high at the flowering stage of the rice crop followed by ripening, tillering, post-harvest and pre-plantation stage. Phylogenetic analysis of 16S rRNA genes of methanogenic community indicated that flowering and ripening stages comprised of Methanomicrobiaceae, Methanosarcinaceae, Methanosaetaceae and RC I methanogenic groups, while only the members of Methanomicrobiaceae and RC I were present in the remaining stages. Further, the dominance of RC I was observed in all stages. This study demonstrates that flowering and ripening stages of rice crop offer relatively favorable ecological niche for methanogenic community. The overall analyses suggest that the temporal change in diversity of methanogens regulates CH4 production potential in rice field soils.

Predicting the effects of increasing temporal scale on species composition, diversity, and rank-abundance distributions

Paleoecological analyses that test for spatial or temporal variation in diversity must consider not only sampling and preservation bias, but also the effects of temporal scale (i.e., time-averaging). The species-time relationship (STR) describes how species diversity increases with the elapsed time of observation, but its consequences for assessing the effects of time-averaging on diversity of fossil assemblages remain poorly explored. Here, we use a neutral, dispersal-limited model of metacommunity dynamics, with parameters estimated from living assemblages of 31 molluscan data sets, to model the effects of within-habitat time-averaging on the mean composition and multivariate dispersion of assemblages, on diversity at point (single station) and habitat scales (pooled multiple stations), and on beta diversity. We hold sample size constant in STRs to isolate the effects of time-averaging from sampling effects. With increasing within-habitat time-averaging, stochastic switching in the identity of species in living (dispersal-limited) assemblages (1) decreases the proportional abundance of abundant species, reducing the steepness of the rank-abundance distribution, and (2) increases the proportional richness of rare, temporally short-lived species that immigrate from the neutral metacommunity with many rare species. These two effects together (1) can shift the mean composition away from the non-averaged (dispersal-limited) assemblages toward averaged assemblages that are less limited by dispersal, resembling that of the metacommunity; (2) allow the point and habitat diversity to increase toward metacommunity diversity under a given sample size (i.e., the diversity in averaged assemblages is inflated relative to non-averaged assemblages); and (3) reduce beta diversity because species unique to individual stations become shared by other stations when limited by a larger but static species pool. Surprisingly, these scale-dependent changes occur at fixed sample sizes and can become significant after only a few decades or centuries of time-averaging, and are accomplished without invoking ecological succession, environmental changes, or selective postmortem preservation. Time-averaging results in less inflation of diversity at habitat than at point scales; paleoecological studies should thus analyze data at multiple spatial scales, including that of the habitat where multiple bulk samples have been pooled in order to minimize time-averaging effects. The diversity of assemblages that have accumulated over 1000 years at point and habitat scales is expected to be inflated by an average of 2.1 and 1.6, respectively. This degree of inflation is slightly higher than that observed in molluscan death assemblages at these same spatial scales (1.8 and 1.3). Thus, neutral metacommunity models provide useful quantitative constraints on directional but predictable effects of time-averaging. They provide minimal estimates for the rate of increase in diversity with time-averaging because they assume no change in environmental conditions and in the composition of the metacommunity within the window of averaging.

Diversity of Polychaeta (Annelida) and other worm taxa in mangrove habitats of Darwin Harbour, northern Australia

In this paper data on the diversity, distribution and abundance of polychaetes and other worm taxa in the mangroves of Darwin Harbour, northern Australia, are presented and compared with those of other tropical mangrove areas. Aspects of the feeding guild ecology and the effects of disturbance on mangrove worms are also examined. Data were collected over a period of four years, across four mangrove assemblages. Samples were obtained using three sampling techniques: 1 m × 1 m quadrat searches, epifauna searches and a new infaunal sampling technique, the anoxic mat. A total of 76 species (68 polychaetes, 1 oligochaete, 1 echiuran, 3 sipunculans, 2 nemerteans, 1 turbellarian) were recorded from the four main mangrove assemblages. Of these, 30 species are widespread, occurring in mangrove and non-mangrove habitats throughout the Indo-west Pacific. Only seven species (all polychaetes) appear to be restricted to the mangroves of Darwin Harbour and northern Australia. Polychaetes are predominant, comprising 80–96% of all worms sampled, with three families—Nereididae, Capitellidae and Spionidae—accounting for 46% of all species. The highest diversity and abundance was recorded in the soft, unconsolidated substrates of the seaward assemblage, with diversity and abundance decreasing progressively in the landward assemblages. Most of the worm fauna was infaunal (70%), but the intensive sampling regime revealed a hitherto unknown significant percentage of epifaunal species (18%) and species occurring as both infauna and epifauna (12%). Univariate analyses showed annual and seasonal differences in worm species richness and abundance—presumably associated with the intensity of the monsoon and recruitment success. The worm fauna differed between mangrove assemblages but the proportion of species in each feeding guild was relatively consistent across the four assemblages studied. Herbivores were the most species-rich and abundant, followed by carnivores and sub-surface deposit feeders. Multivariate analyses showed that the species composition of urbanised mangroves differed from that of undisturbed sites, with surface deposit feeders more numerous in urbanised habitats. Overall, the findings demonstrate a dynamic spatial and temporal variation in diversity and abundance, and provide insight on the range of microhabitats in which mangrove worms occur and their response to anthropogenic disturbance.

Temporal variation of diversity in Italian durum wheat germplasm

The aim of this work is to analyse the temporal change of genetic diversity in Italian durum wheat germplasm. The germplasm deployed in this study (158 accessions), belonging to 5 different historical classes, was characterised for its microsatellite and gliadin markers. The level of genetic diversity (He), based on gliadin and SSR markers results – on average – greater in indigenous landraces present in Italy before 1915, with the exception of pure line material which had been selected from landraces (showing highest level of heterozigosity for gliadin markers). Genotypes obtained from crosses or mutagenesis (referring to the 1950–1960 period) along with those resulting from crosses between CIMMYT lines and old materials (1970s and beyond) were also genetically more diverse. Forty-nine percent of indigenous landraces were genetically heterogeneous. Nine out of 53 landrace accessions were able to capture 4 different SSR private alleles. It is speculated that the reduction of allele richness is an indicator of the genetic erosion of the pre-breeding germplasm and it is pointed out that the implementation of appropriate methods of genetic conservation of this germplasm is a priority for breeding and food safety.

SPATIOTEMPORAL VARIATION IN THE DIVERSITY OF HYMENOPTERA ACROSS A TROPICAL HABITAT GRADIENT

Understanding global biodiversity patterns requires analyses at multiple spatial and temporal scales, across a variety of different habitat types. We used a highly replicated study in coastal Ecuador to examine simultaneously for the first time spatial and temporal species turnover and the contribution of five different habitat types (rice, pasture, coffee agroforests, abandoned coffee agroforests, and native forest fragments) to regional diversity in the tropics, using the experimental placement of standardized nesting structures for bees and wasps. There was notable overlap in the communities of different habitat types, indicating that even intensively managed land can provide a valuable contribution to the overall biodiversity of the landscape mosaic. Importantly, there was a significant effect of habitat type on temporal variation in diversity. While intensive cropping systems such as rice and pasture exhibited higher diversity in certain months, greater species turnover through time in the abandoned coffee and forest plots accounted for the higher overall diversity in these habitats. Overall, spatial and temporal turnover explained 38.6% and 23.1%, respectively, of partitioned regional species richness. A quantitative analysis revealed that the relative habitat specificity of Hymenoptera decreased with increasing habitat disturbance.

Temporal Variation in Diversity and Community Structure of a Semi-Isolated Neuston Community

Temporal variability in neuston diversity and community structure in Lough Hyne Marine Nature Reserve, Co. Cork, was studied over a two-year period. Neuston sampling was carried out at different time scales in order to make between-year, seasonal and monthly comparisons and, in May 2003, at midday and midnight for six consecutive days to make daily and twelve-hourly (diel) comparisons. Three sampling tracks were established in Lough Hyne, each corresponding to a basin subject to different hydrographical environments. Neuston abundance and diversity (Shannon-Wiener index, H′) were estimated for each timescale, and univariate analyses (ANOVA) revealed significant scales of temporal variation. There was significant monthly variation of neuston abundance within seasons, and this was dependent on site and year: summer months showed highest abundances, whereas lows were recorded in January of both years. Generally, higher concentrations of neuston were found at the two sites with reduced water circulation. Diversity maxima occurred during October and September of the consecutive years. The second sampling year showed greater diversity. At smaller temporal scales there was significant variation in neuston numbers and diversity, which was dependent on site, diel period and day. Higher abundances were generally found at night, whereas nocturnal neuston diversity was not always greater than that at midday. Multivariate analysis identified distinct nocturnal and diurnal assemblages, providing indirect evidence for vertical migration of certain taxa. Seasonal succession was evident, as was interannual variation. The community was dominated by 'temporary neuston' typical of neritic, boreal areas and was in a state of flux.

Temporal Variation in Diversity and Community Structure of A Semi-Isolated Neuston Community

Temporal variability in neuston diversity and community structure in Lough Hyne Marine Nature Reserve, Co. Cork, was studied over a two-year period. Neuston sampling was carried out at different rime scales in order to make between-year, seasonal and monthly comparisons and, in May 2003, at midday and midnight for six consecutive days to make daily and twelve-hourly (diel) comparisons. Three sampling tracks were established in Lough Hyne, each corresponding to a basin subject to different hydrographical environments. Neuston abundance and diversity (Shannon Wiener index, H') were estimated for each timescale, and univaniate analyses (ANOVA) revealed significant scales of temporal variation. There was significant monthly vanration of neuston abundance within seasons, and this was dependent on site and year: summer months showed highest abundances, whereas lows were recorded in January of both years. Generally, higher concentrations of neuston were found at the two sites with reduced water circulationi. Diversity maxima occurred during October and September of the consecutive years. The second samlpling year showed greater diversity. At smaller temporal scales there was significant variation in neuston numbers and diversity, which was dependent on site, diel penrod and dlay. Higher abundances were generally found at night, whereas nocturnal neuston diversity was not always greater than that at midday. Multivanrate analysis identified distinct nocturnal and diurmal assemblages, providing indirect evidence for vertical migration of certain taxa. Seasonal succession was evident, as was interannual vanation. The conimmunity was dominated by 'temporary neuston' typical of neritic, boreal areas and was in a state of flux. K.A. Rawlinson (corresponding author; e-mail: k.rawlinson@unh. edu), Department of Zoology, Rudman

Temporal Variation in Diversity and Community Structure of a Semi-Isolated Neuston Community

Temporal variability in neuston diversity and community structure in Lough Hyne Marine Nature Reserve, Co. Cork, was studied over a two-year period. Neuston sampling was carried out at different time scales in order to make between-year, seasonal and monthly comparisons and, in May 2003, at midday and midnight for six consecutive days to make daily and twelve-hourly (diel) comparisons. Three sampling tracks were established in Lough Hyne, each corresponding to a basin subject to different hydrographical environments. Neuston abundance and diversity (Shannon-Wiener index, H′) were estimated for each timescale, and univariate analyses (ANOVA) revealed significant scales of temporal variation. There was significant monthly variation of neuston abundance within seasons, and this was dependent on site and year: summer months showed highest abundances, whereas lows were recorded in January of both years. Generally, higher concentrations of neuston were found at the two sites with reduced water circulation. Diversity maxima occurred during October and September of the consecutive years. The second sampling year showed greater diversity. At smaller temporal scales there was significant variation in neuston numbers and diversity, which was dependent on site, diel period and day. Higher abundances were generally found at night, whereas nocturnal neuston diversity was not always greater than that at midday. Multivariate analysis identified distinct nocturnal and diurnal assemblages, providing indirect evidence for vertical migration of certain taxa. Seasonal succession was evident, as was interannual variation. The community was dominated by 'temporary neuston' typical of neritic, boreal areas and was in a state of flux.

Analysis of temporal variation in the diversity of a small mammal community

The validity of using single-sample surveys to measure small mammal diversity was assessed by measuring the effect of short-term, temporal variation in species diversity on the spatial diversity of small mammals occupying fencerow habitats. The diversity of small mammals varied seasonally. Interaction between changes in richness and evenness accounted for the temporal variation in diversity. Temporal variation was attributed to the response of the small mammals to seasonal changes in the vegetation, to the fluctuation in meadow vole (Microtus pennsylvanicus) captures among seasons, and to the appearance of small numbers of several mammal species during the summer. Significant spatial variation in species diversity existed, but was masked by the effect of seasonal changes in habitat on the small mammals. Erroneous conclusions could therefore be drawn from the pooling of many single-sample surveys of small mammal diversity.