Detrended Correspondence Analysis Research Articles

Tracing last millennium cycles of Río de la Plata Plume Water input into the Southwestern Atlantic Ocean

Recent studies established a strong connection between instrumental hydroclimatic changes in the Río de la Plata (RdlP) watershed and the influx of continental terrigenous material and productivity changes. This correspondence was further validated for the last millennium. Here, we identified centennial, multi-decadal, and interannual changes in diatom composition, as a proxy for La Plata Plume Water (PPW) discharge into the inner shelf. Core GeoB13813-4 diatom data were revisited, and grouped into freshwater, marine, and brackish categories for multivariate, timeseries, and correlation analyses. Such record exhibits a noteworthy resemblance to paleoclimatic and paleoceanographic variations throughout the past millennium. A Detrended Correspondence Analysis (DCA) on the dominant taxa, and Axis-1 revealed a salinity gradient over the past millennium. DCA1-scores exhibited significant correlation with reconstructions of El Niño Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), and the Atlantic Multidecadal Oscillation (AMO) over the same period.By plotting DCA1-scores, we inferred time intervals with varying levels of PPW influence. During ∼936–1500 CE, the PPW influence was weak, as the record was dominated by marine taxa, indicating lateral transport from the Brazilian upwelled water and a stronger influence of the Subtropical Shelf Water. After 1500 CE, a well-developed plume was inferred, with the highest influence occurring after 1800 CE, as evidenced by an increased presence of freshwater/brackish taxa. This increased PPW influence after 1500 CE can be attributed to the onset of more humid conditions and associated increased river discharge, particularly under El Niño conditions, with further ENSO intensification after 1800 CE. We identified significant centennial (250 years) and multidecadal cycles (25–50 years) in diatom community composition. These cycles are related to solar forcing, PDO, and AMO. During the 20th Century, cycles of 2 to 7 years were associated with interannual ENSO variability, while 40-year cycles were linked to AMO and PDO variability.

FERNS RICHNESS ALONG ENVIRONMENTAL GRADIENTS IN AYER HITAM FOREST, PENINSULAR MALAYSIA

Fern species richness was assessed to ascertain the distributional pattern of the ferns as influenced by the environmental gradients in Ayer Hitam forest reserve, Peninsular Malaysia. The ferns were collected using a preferential non-random sampling technique. Temperature, humidity, light intensity and elevation data were obtained at each point of collection of the ferns. The influence of these environmental gradients on the distribution of the species was determined using Detrended Correspondence Analysis (DCA) and general linear model (GLM). A total of 67 ferns were identified at all the study sites. Two ferns namely Asplenium antiquum and Pteris longipinnula were first recorded in this study. In all the sites, light intensity ranges from 337.9 – 8098 lux, temperature ranges from 28.5 - 33oC, humidity ranges from 66.24 - 88.80%, and elevation ranges from 14–33m. Tectaria singaporeana and Nephrolepis biserrata are the only species that are widely distributed across all the study sites. The DCA revealed that the light intensity influences the distribution of the ferns species in this forest. However, the GLM showed that temperature had a positive influence on the distribution of the ferns while light intensity had a negative influence on them.

Trouble in the rice field: Distribution ecology and indicator value of weed species in the rice fields of Himalayan region

Field-based evaluation of indicator weed species in agriculture systems is effective for developing site-specific weed management. Because of anthropogenic activities and climate change, new weeds are invading agricultural fields. The current study examined the weed species in agricultural fields with a focus on diversity, distribution ecological patterns, and identification of indicator species, all of which might help in effective weed management practices. Following the calculation of the Importance Value Index for each weed species, ordination, and indicator species analysis were conducted. We collected vegetation data through random sampling, and the current study recorded 47 species, taxonomically distributed across 41 genera and 19 families. Asteraceae with 13% of species was the leading family followed by Poaceae, and Brassicaceae (11% each). Annual weed species with 49% were the dominant life span category. The phytogeographical analysis revealed that the highest number (28 species) recorded from the study area were native, while 19 species were alien. Of the total alien species, 4 were invasive, and 14 were naturalised and one species Bassia scoparia was casual. The diversity indices show significant differences (p ≤ 0.05) in weeds in rice fields recorded from the study area. Detrended correspondence analysis grouped the species Geranium rotundifolium, Sisymbrium loeselii, Mentha longifolia, Rumex dentatus, Amaranthus viridis on the extreme left side suggest a low score on axis 1 and a high score on axis 2. The analysis of indicator species revealed a significant difference (p ≤ 0.05) in agriculture fields across the sampled sites. According to the indicator species analysis, Poa annua, Persicaria hydropiper, Ranunculus sceleratus, and Echinochloa colona were the key weed species found in the study area. This investigation might aid weed management strategies to minimize crop losses and increase of rice production to fulfill the current food requirement.

Toward Sustainable Development Trajectories? Estimating Urban Footprints from High-Resolution Copernicus Layers in Athens, Greece

Land imperviousness reflects settlement growth and urban sprawl. Grounded on a comparative approach, a set of multidimensional statistical techniques were adopted here to quantify the evolution of land imperviousness from Copernicus High-Resolution Layers (HRLs) in a representative case study of Southern Europe (Athens, Greece). A two-way data matrix reporting the percent share of the surface land exposed to different sealing levels (101 classes ranging continuously from 0% to 100%) in the total municipal area was computed for two years (2006 and 2018) individually for 115 municipalities in metropolitan Athens. This matrix represented the information base needed to derive place-specific urban footprints and a comprehensive (global) profile of land imperviousness. Results of a Detrended Correspondence Analysis (DCA) delineated a metropolitan structure still organized along the density gradient, moving from dense settlements in central locations with dominant land classes sealed for more than 90% of their surface area to completely pervious land (0%) typical of rural locations. While the density gradient became less steep between 2006 and 2018, it continued to aliment a socioeconomic polarization in urban and rural districts with distinctive profiles of land imperviousness. Intermediate locations had more mixed imperviousness profiles as a result of urban sprawl. Differential profiles reflect place-specific urban footprints with distinctive land take rates.

Ecological and structural differentiation of the Sudanian woodlands in the Biosphere Reserve of Pendjari, Benin

Aims: This study aims to: i) differentiate the plant associations in the Biosphere Reserve of Pendjari (BRP), ii) determine the ecological characteristics of their habitats and iii) present distribution maps on different soil types. Study area: The BRP, located in the Sudanian Zone of Benin. Methods: 202 phytosociological relevés were sampled according to the Braun-Blanquet method within the BRP. Ordination was performed using Detrended Correspondence Analysis to evaluate vegetation patterns. Soil parameters were used to characterize the vegetation types. Results: The numerical analysis of 202 plots and 249 plant species showed two major floristic groups that correlated with a moisture gradient: drylands versus wetlands. The dryland group was a mixture of woodland and shrub savanna, the dominant ecosystems of the study area. The wetland group encompassed species primarily from riparian forest, tree savanna and grass savanna on floodplains. Syntaxonomical analysis of the dryland group showed rocky and gravelly soil associations (Burkeo africanae-Detarietum microcarpi) and soils associated with or without fine gravels (Andropogono gayani-Terminalietum avicennioidis, Andropogono gayani-Senegalietum dudgeonii and Terminalietum leiocarpae). Syntaxonomical analysis of the wetland group showed riparian forest associations on sandy-clay soil (Coletum laurifoliae, Borassetum aethiopi and Hyparrhenio glabriusculae-Mitragynetum inermis) and floodplain associations on silt-clay soil (Terminalio macropterae-Mitragynetum inermis, Brachiario jubatae-Terminalietum macropterae, Sorghastro bipennati-Vachellietum hockii). Conclusions: Eleven new associations were identified in this study. If the distribution of plant associations was determined by different soil properties, the soil humidity would be one of the main ecological factors determining the establishment of plant species and thus plant association development. Taxonomic reference: Akoègninou et al. (2006), Angiosperm Phylogeny Group classification for the orders and families of flowering plants (APG IV, 2016). Abbreviations: BRP = Biosphere Reserve of Pendjari; CBD = Convention on Biological Diversity; CCA = Constrained Correspondence Analysis; DCA = Detrended Correspondence Analysis; GPS UTM = Global Positioning System Universal Transverse Mercator.

A Ferroptosis-Related lncRNAs Signature Predicts Prognosis of Colon Adenocarcinoma.

(1) Ferroptosis is a type of cellular death caused by lipid-dependent iron peroxide, which plays a major role in cancer. Long noncoding RNAs (lncRNAs) are increasingly recognized as key regulating substances in ferroptosis; (2) RNA sequencing expressions and clinical data of 519 patients with colon adenocarcinoma (COAD) were downloaded from The Cancer Genome Atlas (TCGA) database. The expression levels of lncRNAs related to ferroptosis were screened with Pearson correlation analysis. Differential genes were enriched with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. LncRNAs related to ferroptosis were determined with univariate Cox regression and multivariate Cox regression analyses, and patients with COAD were classified into high- and low-risk subgroups according to their median risk score. The prognostic value was further examined, and the association between ferroptosis-related lncRNAs (frlncRNAs) and survival in patients with high and low risks of COAD was validated. A TCGA-COAD data set was used for receiver operating characteristic (ROC) analysis and detrended correspondence analysis (DCA) to assess prediction accuracy. Finally, a nomogram was constructed to predict survival probability; (3) We obtained a model consisting of a five-frlncRNAs signature comprising AP003555.1, AP001469.3, ITGB1-DT, AC129492.1, and AC010973.2 for determining the overall survival (OS) of patients with COAD. The survival analysis and ROC curves showed that the model had good robustness and predictive performance on the TCGA training set; (4) We found that a five-frlncRNAs signature may play a potential role in anti-COAD immunity. Risk characteristics based on frlncRNAs can accurately predict the prognosis and immunotherapy response of patients with COAD.

Phytolith assemblages reflect variability in human land use and the modern environment

Phytoliths preserved in soils and sediments can be used to provide unique insights into past vegetation dynamics in response to human and climate change. Phytoliths can reconstruct local vegetation in terrestrial soils where pollen grains typically decay, providing a range of markers (or lack thereof) that document past human activities. The ca. 6 million km2 of Amazonian forests have relatively few baseline datasets documenting changes in phytolith representation across gradients of human disturbances. Here we show that phytolith assemblages vary on local scales across a gradient of (modern) human disturbance in tropical rainforests of Suriname. Detrended correspondence analysis showed that the phytolith assemblages found in managed landscapes (shifting cultivation and a garden), unmanaged forests, and abandoned reforesting sites were clearly distinguishable from intact forests and from each other. Our results highlight the sensitivity and potential of phytoliths to be used in reconstructing successional trajectories after site usage and abandonment. Percentages of specific phytolith morphotypes were also positively correlated with local palm abundances derived from UAV data, and with biomass estimated from MODIS satellite imagery. This baseline dataset provides an index of likely changes that can be observed at other sites that indicate past human activities and long-term forest recovery in Amazonia.

Macrolichen Communities Depend on Phorophyte in Conguillío National Park, Chile.

The community composition of epiphytic macrolichens from two tree species (Araucaria araucana and Nothofagus antarctica) was conducted in temperate forests in the Conguillío National Park, Chile. The composition of lichen biota is influenced by phorophyte species, bark pH, and microclimatic conditions. A total of 31 species of macrolichens were found on A. araucana and N. antarctica. Most of the species showed phorophyte preference, with nine being exclusive to A. araucana and 10 to N. antarctica. The detrended correspondence analysis (DCA) indicated the formation of three communities: one representing macrolichens growing on N. antarctica and two others growing chiefly on A. araucana, either with north or south exposure. More work is needed to study the lichen biota of the forests of the Chilean Andes, which are under multiple threats, including clearing and climate change. In order to counteract such risks to native forests and to the biodiversity of the associated epiphytic lichens, conservation plans should be established that consider the factors that influence the composition of the lichen community.

Comparison of survey methods for fungi using metabarcoding and fruit body inventories in an altitudinal gradient.

Metabarcoding of environmental samples is nowadays an established method in biodiversity research. When it comes to studying fungal populations in various ecotypes, fruit body inventories are the traditional method to assess the diversity of fungal communities. In this study, both methods-metabarcoding of soil samples and a traditional fruit body inventory-were conducted on 144 sample plots in an altitudinal gradient in the Bavarian Forest (Germany) and the results were compared. Metabarcoding detected significantly more species than the traditional fruit body inventory. The majority of taxa recorded in the fruit body inventory belonged to the Basidiomycota, whereas in the metabarcoding data, the distribution of species between Basidiomycota and Ascomycota was approximately balanced. Species of several orders forming inconspicuous or hypogeous fruit bodies were detected only by metabarcoding, while several wood decomposers were recorded only in the fruit body inventory. The proportion of detected wood-colonising species with melanized spores was considerably higher with metabarcoding than with the fruit body inventory, where more than 70% of recorded wood-colonisers had hyaline spores. Based on the metabarcoding data, a decline of species richness with increasing altitude was evident, but this was not visible in the fruit body inventory data. Detrended correspondence analyses yielded similar results for relative species community similarities with both survey methods.

Ecological Assessment of the Native Flora of Matta Kharari Village, Swat, Khyber Pakhtunkhwa, Pakistan

Plant species composition, diversity and distribution is a hierarchical expression of vegetation determined by different environmental factors. A study was conducted to document the floristic composition and biological spectrum of plant species of the Matta-Kharari region, Swat. The region has not been ecologically explored yet. We used quantitative ecological techniques for sampling plant species. Sixty-seven quadrats of 1x1 m2 for herbs, 5x5 m2 for shrubs and 10x10 m2 size for trees were established. Plant species data were analyzed using multivariate statistical techniques. We evaluated 76 plant species belonging to 42 families. Asteraceae and Rosaceae were the leading families with 8 species each, followed by Ranunculaceae, Lamiaceae and Moraceae with 4 species each. Among life form classes i.e., geophytes were dominant (13 species, 17.10 %), followed by therophytes (12 species, 15.87 %), nanophanerophytes (11 species, 14.47 %), and chamaephytes (10 species, 13.58 %). Moreover, Mesophylls (36.84 %) were the dominant leaf spectra class followed by nanophyll (30.26 %), microphyll (27.63 %), and megaphyll (2.63 %). The two-way cluster analysis classified the vegetation into three clusters. The detrended correspondence analysis shows the distribution of plants in a mixed array because the locations explored are characterized by similar climatic factors and vegetation. We elucidate that the variation in climatic factors and topography brings variation in vegetation. Understanding these responses at the life form and leaf spectra level will provide a better understanding and knowledge that how plant species and their communities or associations respond to changes in climate in the future. The current study could be utilized as a baseline for large-scale studies in the future.

Graphical methods comparing living and dead assemblages, exemplified with benthic foraminifera from the Aveiro Lagoon, Portugal

This work introduces graphical methods documenting density, diversity (species richness combined with heterogeneity) and similarity in combined diagrams for estimating the influence of environmental and taphonomic factors in living (LAs) and dead (DAs) assemblages. In this paper, the diagrams compare: 1) densities per 1 g of sediment expressed in cubic squares; 2) diversities based on rarefaction species richness (x-axis) and Shannon H rarefaction (y-axis), both extended to infinity by the logistic Hull equation, and 3) similarity diagrams based on cosine measures (x-axis) and Spearman correlation coefficients (y-axis). Diagrams were exemplified for LAs and DAs found at 53 stations along channels and intertidal areas of the Aveiro Lagoon (Portugal). Eight ‘routes’ characterized by different trends in the distribution of the analyzed biotic parameters were recognized in six regions of the Aveiro Lagoon: ‘port area’, ‘central lagoon’, ‘northeast lagoon’, ‘northern and southern extremities of the lagoon’ and ‘city area’. In addition, Detrended Correspondence Analyses (DCA) based on diversity diagrams were performed to show the influence of environmental parameters, especially grain size, salinity, and pH, on the average species composition in each route. The comparative diagrams allow deduction about the impact of parameters that simultaneously affect LAs and DAs, such as hydrodynamics, post-mortem tests dissolution, physicochemical parameters, excessive contribution of organic matter, oxygen depletion, and pollution by metals. Based on these diagrams, the most favorable environments due to the most remarkable development and diversity of LAs and DAs are located in protected coves of the Aveiro Lagoon mouth.

Responses of arid plant species diversity and composition to environmental factors

An oasis is a unique natural landscape in arid and semi-arid areas, significant for regulating regional microclimates and hydrological processes in deserts. However, little is known regarding the response of natural oasis plants communities to various environmental factors. Nineteen sample plots (50 m × 50 m) were selected in the Daliyabuyi Oasis in the Taklimakan Desert hinterland based on the location of groundwater monitoring wells and 76 vegetation quadrats (25 m × 25 m) were established. A two-way indicator species analysis, Mantel test, detrended correspondence analysis, canonical correspondence analysis (CCA), and hierarchical partitioning were used to provide an in-depth analysis of community classification, species composition, and environmental interpretation of the oasis. A generalized linear model was used to verify the results which showed that the current oasis community could be divided into four types according to the dominant species, which is controlled by soil moisture. Measurement of species composition and distribution of communities showed significant differences between species diversity of individual community types. Variations in groundwater depth affects patterns of species diversity which is sensitive to richness, while the degree of surface water disturbance affects the pattern of species evenness. Moreover, the CCA ordination map showed that community distribution and diversity characteristics have their own preferences in habitat gradients. The study concluded that the species dominance of the community and the composition and distribution are not dominated by a single factor. There are differences in the scale and effect of different water resource types in maintaining community characteristics.

Nematode functional traits and community structure change from river to the terrestrial border in Segara Anakan Mangrove, Indonesia

Abstract. Maharning AR, Ardli ER, Prabowo RE. 2023. Nematode functional traits and community structure change from river to the terrestrial border in Segara Anakan Mangrove, Indonesia. Biodiversitas 24: 2434-2446. We intended to explore the spatial distribution of nematode functional traits and community structure in Segara Anakan Mangrove, Indonesia. Samples were retrieved from 14 stations, extending from the river to the area adjacent to terrestrial forest. We used taxonomic and functional trait identification, covering body shape, length, tail shape, feeding type, and life history as independent traits, and combined traits by collecting traits describing individual nematodes. The principal component analysis suggested that predatory or omnivorous or long-size nematodes mainly inhabited stations adjacent to the terrestrial forest but were unclear for the mid-stations. There were 29 combined traits and 38 genera of nematodes observed. The detrended correspondence analysis revealed that nematode compositional changes from the river to the terrestrial adjacent area were clearer for the combined traits and nematode genera. Seven combined traits and 12 genera inhabited only the particular stations of the study site. The common nematodes were slender, 1-2 mm long, elongated filiform tails, non-selective deposit feeders, and very tolerant to pollutants, which lived in almost all stations (92.86%). The genus relative abundance (>10%) included Anoplostoma, Eubostrichus, and Chromadorina. The results suggest that distance from the river might regulate the habitability of nematodes, in which nematode functional traits play roles.

Methodological aspects of synphytoindication analysis of topological differentiation of biotopes

The advantages and disadvantages of some most common methods of quantitative analysis used in processing of synphytoindication data were analyzed. These methods enabled reflection of important ecological characteristics of plant communities and assessment of the nature of their topological and regional differentiation characterizing α-, β-, γ-diversity. We also examined current debatable issues regarding the use of scales of ecological indicator values and methods of their correct comparison based on bringing to a single "denominator". The visual aspects of the gradient analysis used in assessment of topological differentiation of habitats based on the establishment of various types (vector, combinative and complex) of ecological and coenotic profiles are considered. We focused our attention on the application of optimal models of ordination methods (detrended correspondence analysis – DCA, non-metric multidimensional scaling – NMDS). The use of cluster analysis reflected in various methods of dendrogram constructing was evaluated. The analysis of the above methods allows us to evaluate the efficiency of their use in various aspects of synphytoindication techniques. This allows us to use such data for forecasting and modeling biocoenoses changes and development, for assessment and classification of biotopes, landscape structure (ecomer), zoning (ecochor), as well as for evaluation of the resistance of vegetation to the influence of external factors. The methods and approaches of mathematics and cybernetics are expected to be more widely used in geobotany in the future, since many pressing ecological issues related to non-linear development, emergent changes in the ecosystems properties and search for critical thresholds cannot be solved in a traditional way.

Effects of plant community and altitude on food composition of Cervus elaphus wallichii during the withered grass period on the Tibetan Plateau, China.

How Tibetan red deer (Cervus elaphus wallichii) acclimates to high altitude environment during the withered grass period is one of the challenges in maintaining their nutrient intake. It is an important basis to study the nutritional ecology of wild large ungulates in alpine ecosystems by investigating the changes in plant communities with altitude during the withered grass period and how these changes affect the food composition of Tibetan red deer. In this study, we selected the Tibetan red deer in Sangri County, Shannan region of Tibet as the research subject. We carried out field surveys on the altitude, plant communities, and feeding traces of the Tibetan red deer in March of 2021 and 2022 during the withered grass period on the Tibetan Plateau. Detrended correspondence analysis and canonical correspondence analysis were used to study altitudinal variations in plant communities and the regularity of food composition. The results showed that during the period of withered grass, Tibetan red deer ate primarily Salix daltoniana, Rosa macrophylla var. glandulifera and Dasiphora parvifolia. S. daltoniana accounted for more than 50% of the food composition, as the main food resources for red deer in withered grass period. In the low altitude area (4100-4300 m), plant community included Caragana versicolor, R. macrophylla and Berberis temolaica, and Tibetan red deer mainly ate R. macrophylla, C. versicolor and Artemisia wellbyi. In higher altitude area (4300-4600 m), plant community consisted of Rhododendron nivale, Rhododendron fragariiflorum, and Sibiraea angustata, and Tibetan red deer mainly fed on S. daltoniana, Salix obscura, and Carex littledalei. At different altitudes, the dominant plant species were the main food of Tibetan red deer. It is suggested that the changes of plant community composition with altitude directly affected food composition of Tibetan red deer, indicating different food composition patterns with altitude gradients.

Vegetation change in acidic dry grasslands in Moravia (Czech Republic) over three decades: Slow decrease in habitat quality after grazing cessation

AbstractAimsShallow soils on acidic bedrock in dry areas of Central Europe support dry grasslands and heathlands that were formerly used as extensive pastures. These habitats are of high conservation value, but their abandonment in the 20th century triggered slow natural succession that poses a threat to specialized plant species. We asked how this vegetation and its plant diversity have changed over the past three decades and whether protected areas have positively affected habitat quality.LocationSouthwestern and central Moravia, Czech Republic.MethodsIn 2018–2019, we resurveyed 94 vegetation plots first sampled in 1986–1991 at 47 acidic dry grassland and heathland sites. We compared the number of all vascular plant species, Red List species and alien species per plot using parametric and non‐parametric tests, life‐form spectra using the chi‐square test, species composition using detrended correspondence analysis, and indicator values using a permutation test. We also compared these changes between sites within and outside protected areas.ResultsVegetation changes over the past three decades have been relatively small. However, we detected a decrease in total species richness, the number of Red List species and the number of characteristic species of dry grasslands. Neophytes were infrequent, while archaeophytes increased slightly. The competitive tall grass Arrhenatherum elatius, annual species and young woody plants increased in abundance or newly established at many sites. Indicator values did not change except for a slight increase in nutrient values. These negative trends occurred both within and outside protected areas but were more pronounced outside.ConclusionsFormerly grazed acidic dry grasslands and heathlands in Moravia are slowly losing habitat specialists, including threatened plant species, and are increasingly dominated by Arrhenatherum elatius. Conservation management, especially cutting in protected areas, slows down the negative trends of decline in plant diversity and habitat quality but is insufficient to halt these processes completely.

Investigating the association between diet and infection with Trichomonas gallinae in the European turtle dove (Streptopelia turtur)

AbstractTrichomonas gallinae, a protozoan parasite infecting a wide range of birds, has been a cause for conservation concern since its recognition as an emerging infectious disease, having had notable impacts on several avian species, including causing widespread mortality in greenfinches (Chloris chloris), and chaffinches (Fringilla coelebs), and hindering the recovery of the endangered pink pigeon (Nesoenas mayeri). Horizontal transmission between birds congregating at feeding sites, such as those provided for conservation and species management purposes, is an important driver in the spread of T. galliane. Supplementary feeding is a key conservation intervention for the European turtle dove (Streptopelia turtur), which is declining across its range, driven at least partially by a loss of natural food resources. Due to the link between T. gallinae transmission and supplementary feeding, we consider the prevalence of this parasite among European turtle dove in relation to diet, in the first study to analyze these two factors in the decline of this species together. Using birds sampled from breeding and wintering grounds, the dietary composition of individuals was compared to the presence of T. gallinae, and specific T. gallinae strains. Dietary variation was summarized into two axes using detrended correspondence analysis; neither was associated with the presence of T. gallinae or any specific strains. The proportion of diet accounted for by cultivated seeds did not affect parasite presence, despite the spread of this parasite being associated with supplementary feeding due to an increase in contact between potentially infected and uninfected birds gathering at high densities at feeding sites. Significant dietary overlap was observed between infected and uninfected individuals in all sites, with almost complete dietary overlap being observed in one breeding site. The level of dietary overlap between individuals infected with specific strains fluctuated between sampling seasons, indicating no consistent relationship between diet and infection status.

Assessment of macroalgae coverage in a scarcely studied deep rocky reef in the tropical eastern Mexican Pacific

The biodiversity of epibenthic communities in rocky reefs in the Mexican tropical Pacific has been studied minimally during the past three decades. This study describes the abundance and distribution of algae and invertebrates in a deep rocky reef from this region. Samples were taken at 20 m depth in 2012 by randomly placing 50×50 cm quadrats. Also, photographs were taken of each quadrat to quantify the coverage of organisms. Throughout the study, the algae were the most abundant group (17748.5 cm m-2), of which encrusting calcified (6350.9 cm m-2), turf (3040.3 cm m-2), and larger-sized articulated corallines (2700.9 cm m-2) had the highest coverage. Regarding invertebrates, zoanthids (1153.3 cm m-2) and corals (746.7 cm m-2) had high coverage. All of the algal groups were found on vertical and horizontal substrates. The detrended correspondence analysis showed that larger-sized articulated corallines and encrusting not calcified groups were prevalent on the horizontal substrate and corals on the vertical substrate. These abundance and distribution patterns represent the first quantitative study of rocky reefs from the region. Considering the rapid influence of human activities in this coastal zone and the fact that rocky reefs have been minimally studied, there is a clear need for long-term monitoring programs to establish reef communities' patterns and processes, which are useful in conservation programs.

Response of diatom assemblages to orbital‐ and millennial‐scale climatic variability since the penultimate glacial maximum in the northern limit of the Neotropics

ABSTRACTLake Chalco, in Central Mexico, has a long diatom record which provides an excellent opportunity to document the biotic and hydrological responses of this ecosystem to orbital‐ and millennial‐scale climatic variability during the last 150 ka. Detrended correspondence analysis was used to evaluate the ecological turnover and to identify diatom species associations throughout the sequence. Millennial‐scale climatic fluctuations were identified as peaks in freshwater (mostly small Fragilariaceae spp.) or as peaks in salt‐tolerant species. At orbital scales, species turnover involved changes between freshwater assemblages dominated by Stephanodiscus spp. – small Fragilariaceae spp. – Cocconeis placentula, present during low‐evaporation, cool intervals [late Marine Isotope Stage (MIS)6, MIS5d, MIS2] against salt‐tolerant taxa, dominated by Stephanocyclus and Cyclotella spp., in higher evaporation, higher salinity conditions (MIS5e, MIS5c–a, MIS4, MIS3, early MIS1). Comparatively, MIS6 and MIS5d seem to have been cooler (~ −6 to −7 °C) and wetter than MIS2 (~ − 4 to −5 °C). In contrast, MIS5e and early MIS1 (11.5–6 ka) had similar warmer, low lake level, saline conditions. In addition, MIS5 was a period of intense climatic change associated with wide‐amplitude orbital forcing that favored a Stephanocyclus–Cyclotella spp. ecological succession (S. meneghinianus, C. tlalocii, C. poyeka, S. quillensis). In contrast, smaller temperature changes were inferred during MIS4 and MIS3.

Biogeographical Relationships and Diversity in the Peruvian Flora Reported by Hipólito Ruiz and José Pavón: Vegetation, Uses and Anthropology.

The Royal Spanish Botanical Expedition to the Viceroyalty of Peru in the 18th century was one of the most important European expeditions to American territories. Using the herbarium sheets of Ruiz and Pavón (Royal Botanical Garden of Madrid) and their edited works, manuscripts and expedition diaries, we have constructed a database of the collected and observed flora, which has served as the basis for a map containing all of the Peruvian localities of the expedition. Based on the method of bioclimatic belts and our own observations, we have deduced to which type of vegetation the flora studied in the expedition belongs. The uses of the flora per locality were studied, as well as the ethnic groups involved in the different localities. By using a Principal Component Analysis, we have obtained the distribution of the bioclimatic belts whose vegetation was the most explored. In order to observe the bioclimatic tendency of plant uses, a Detrended Correspondence Analysis (DCA) was conducted to identify the distribution of localities with the highest frequencies of plant uses. The expedition's explorations focused on the most humid areas of the thermo- and mesotropical belts, from where a large number of plants with practical uses were obtained.