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Results for “ecological speciation”

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PubMed1986

Hematocrit and hemoglobin concentration in four chromosomal species and some isolated populations of actively speciating subterranean mole rats in Israel.

Hematocrit (HCT) and hemoglobin (Hb) concentration were measured in four chromosomal species and some peripherally semi-isolated and isolated populations of the mole rat superspecies Spalax ehrenbergi in Israel. HCT was 52.0, 51.4, 50.9, and 47.8%, and Hb was 16.0, 16.6, 16.3, and 14.7 g/100 ml for 2n = 52, 58, 54, and 60, respectively. The species 2n = 60, which lives in arid habitats, had lower HCT and Hb than the other three species. HCT decreased as aridity increased between the species and within the species 2n = 60. Changes in HCT probably reflect clinal changes in both soil permeability to gases and ambient temperature.

Animals↗

PubMed1991

The behaviour of heavy metals in sewage sludge-amended soils.

Soils amended with sewage sludges generally contain elevated concentrations of a wide range of heavy metals and are therefore of interest with regard to their potential impact on human health. This review considers the concentrations of heavy metals in sewage sludges and in the soils amended with them. The effects of sludge amendments on soil properties, the speciation of heavy metals and their bioavailability are reviewed. Variations in heavy metal accumulation between crop species are considered, together with the effects of sludge-borne heavy metals on soil microorganism activity. Perhaps the most important questions to be addressed are the changes in the bioavailability of the heavy metals and their distribution in the soil profile during the residual period. The consequences of the application of sewage sludges to agricultural soils, with regard to the long-term bioavailability and movement of metals in soil profiles, are incompletely understood.

Animals↗

PubMedDate not supplied

Carbohydrate-based species recognition in sea urchin fertilization: another avenue for speciation?

Spawning marine invertebrates are excellent models for studying fertilization and reproductive isolating mechanisms. To identify variation in the major steps in sea urchin gamete recognition, we studied sperm activation in three closely related sympatric Strongylocentrotus species. Sperm undergo acrosomal exocytosis upon contact with sulfated polysaccharides in the egg-jelly coat. This acrosome reaction exposes the protein bindin and is therefore a precondition for sperm binding to the egg. We found that sulfated carbohydrates from egg jelly induce the acrosome reaction species specifically in S. droebachiensis and S. pallidus. There appear to be no other significant barriers to interspecific fertilization between these two species. Other species pairs in the same genus acrosome react nonspecifically to egg jelly but exhibit species-specific sperm binding. We thus show that different cell-cell communication systems mediate mate recognition among very closely related species. By comparing sperm reactions to egg-jelly compounds from different species and genera, we identify the major structural feature of the polysaccharides required for the specific recognition by sperm: the position of the glycosidic bond of the sulfated alpha-L-fucans. We present here one of the few examples of highly specific pure-carbohydrate signal transduction. In this system, a structural change in a polysaccharide has far-reaching ecological and evolutionary consequences.

Acrosome Reaction↗

PubMed2006

The evolution of Dactylorhiza (Orchidaceae) allotetraploid complex: insights from nrDNA sequences and cpDNA PCR-RFLP data.

Sequence data from a portion of the external transcribed spacer (ETS) and from the internal transcribed spacers (ITS1 and ITS2) of 18S-26S nuclear ribosomal DNA were used together with chloroplast DNA PCR-RFLP data to unravel patterns of allotetraploid speciation within the Western European Dactylorhiza polyploid complex. A maximum likelihood tree based on combined ETS and ITS sequences suggests that the Western European Dactylorhiza allotetraploids have evolved by hybridization between four main diploid lineages. Cloned sequences and the topology of the ITS plus ETS tree indicate that the allotetraploid species D. elata, D. brennensis, and D. sphagnicola have originated from the autotetraploid D. maculata together with the diploid D. incarnata, while D. majalis, D. traunsteineri, and D. angustata seem to have evolved by hybridization between the D. fuchsii s.str and D. incarnata lineages. Finally, the diploid D. saccifera lineage seems to have been involved together with the D. incarnata lineage in the formation of the allotetraploid D. praetermissa. The observed congruence between the chloroplast tree and the ITS/ETS tree suggests a directional evolution of the nrDNA after polyploidization in favor of the maternal genome. Considered together with morphological, biogeographical, and ecological evidence, the molecular analysis leads us to recognize four species within the investigated allotetraploid complex, namely D. majalis, D. praetermissa, D. elata, and D. sphagnicola.

Base Sequence↗

PubMed2004

An integrated biomarker-based strategy for ecotoxicological evaluation of risk in environmental management.

Environmental impacts by both natural events and man-made interventions are a fact of life; and developing the capacity to minimise these impacts and their harmful consequences for biological resources, ecosystems and human health is a daunting task for environmental legislators and regulators. A major challenge in impact and risk assessment, as part of integrated environmental management (IEM), is to link harmful effects of pollution (including toxic chemicals) in individual sentinel animals to their ecological consequences. This obstacle has resulted in a knowledge-gap for those seeking to develop effective policies for sustainable use of resources and environmental protection. Part of the solution to this problem may lie with the use of diagnostic clinical-type laboratory-based ecotoxicological tests or biomarkers, utilising sentinel animals as integrators of pollution, coupled with direct immunochemical tests for contaminants. These rapid and cost-effective ecotoxicological tools can provide information on the health status of individuals and populations based on relatively small samples of individuals. In the context of ecosystem status or health of the environment, biomarkers are also being used to link processes of molecular and cellular damage through to higher levels (i.e., prognostic capability), where they can result in pathology with reduced physiological performance and reproductive success. Complex issues are involved in evaluating environmental risk, such as the effects of the physico-chemical environment on the speciation and uptake of pollutant chemicals and inherent inter-individual and inter-species differences in vulnerability to toxicity; and the toxicity of complex mixtures. Effectively linking the impact of pollutants through the various hierarchical levels of biological organisation to ecosystem and human health requires a pragmatic integrated approach based on existing information that either links or correlates processes of pollutant uptake, detoxication and pathology with each other and higher level effects. It is further proposed here that this process will be facilitated by pursuing a holistic or whole systems approach with the development of computational simulation models of cells, organs and animals in tandem with empirical data (i.e., the middle-out approach). In conclusion, an effective integrated environmental management strategy to secure resource sustainability requires an integrated capability for risk assessment and prediction. Furthermore, if such a strategy is to influence and help in the formulation of environmental policy decisions, then it is crucial to demonstrate scientific robustness of predictions concerning the long-term consequences of pollution to politicians, industrialists and environmental managers; and also increase stakeholder awareness of environmental problems.

Animals↗

PubMed2004

Slight differences among individuals and the unified neutral theory of biodiversity.

The unified neutral theory of biodiversity provides a very simple and counterintuitive explanation of species diversity patterns. By specifying speciation, community size and dispersal, and completely ignoring differences among individual organisms and species, it generates biodiversity patterns that remarkably resemble natural ones. Here I show that adding even slight differences among organisms generates very different patterns and predictions. In large communities with widespread dispersal, heritable differences in viability among individual organisms lead to biodiversity patterns characterised by the overdominance of a single species comprising organisms with relatively high fitness. In communities with local dispersal, the same differences produce rapid community extinction. I conclude that the unified neutral theory is not robust to slight deviations from its most controversial assumption.

Algorithms↗

PubMed2026

Molecular identification and diversity assessment of Tyrrhenian Romulea species (Iridaceae).

Taxonomic assignments based only on morphology are often insufficient for delimiting species, particularly in complexes shaped by hybridization and polyploidy, where species boundaries are unclear. This limitation hinders progress in ecological, biogeographic and conservation research. The genus Romulea, distributed across Africa and the Mediterranean Basin, exemplifies this challenge. Despite its remarkable diversity, Mediterranean Romulea has not received much attention from genetic and molecular studies. Here, we present the first multilocus genotype analysis of Mediterranean Romulea taxa, focusing on the Tyrrhenian biogeographic province. Using target-capture sequencing with the universal Angiosperms353 kit, we generated genomic data for 272 individuals representing 18 putative taxa. Our findings reveal genetic groups that align with current taxonomy, the existence of cryptic divergence, and highlight the role of hybridization. Furthermore, analysis of intra-individual genetic diversity suggests one or several allopolyploid origins for Mediterranean Romulea. Four taxa (R. assumptionis, R. revelieri, R. ligustica, R. rollii) are consistently well differentiated across nuclear and plastid datasets, supporting their recognition as distinct species. In contrast, the widespread species R. ramiflora and R. columnae contain well-differentiated groups that may represent cryptic speciation. Several other taxa, including R. x melitensis, R. corsica, and R. bulbocodium, exhibit genomic signatures consistent with hybrid origins. Plastid and nuclear variation patterns are consistent with a hypothesis of rapid radiation in the Tyrrhenian region. These results provide a primary genomic framework for the integrative taxonomy of Romulea.

Genetic Variation↗

PubMed2025

A chromosome-level genome assembly and annotation of Cercis chuniana (Fabaceae).

The genus Cercis L., at the base of the subfamily Cercidoideae of Fabaceae, is known for its ecological adaptability and significant medicinal, ornamental, and economic value. However, the lack of a high-quality genome hinders the understanding of the evolution of Cercis and Fabaceae. In this study, we present a chromosome-level genome of Cercis chuniana by combining Illumina short reads, PacBio HiFi long reads, and Hi-C data. The final genome size is 355.53 Mb, consisting of 12 contigs with a N50 of 42.34 Mb. Notably, 344.24 Mb, corresponding to 96.82% of the genome, was anchored to seven chromosomes. The assembly comprises 24.83% repetitive sequences, including 19.32% long terminal repeats. Additionally, a total of 33,837 protein-coding genes were predicted in the genome, with 32,709 (96.67%) genes successfully annotated. The high-quality genome assembly of C. chuniana not only bridges the existing gap in genomic data and offers important resources for molecular studies of this species, but also provides essential insights for future studies on speciation, functional and comparative genomics within the Fabaceae family.

Genome, Plant↗

PubMed2005

Cryptic speciation in the cosmopolitan and clonal human pathogenic fungus Aspergillus fumigatus.

Microbes and other organisms smaller than one to a few millimeters in size are hypothesized to have global populations, in contrast to the geographically restricted ranges of larger organisms. However, fungi, which routinely have reproductive propagules no larger than 10 micrometers, challenge the generality of this hypothesis because recent studies have shown that globally distributed morphological species embrace two or more geographically restricted phylogenetic species. We used the concordance of gene genealogies to recognize phylogenetic species in the globally distributed opportunistic human pathogenic fungus, Aspergillus fumigatus. Based on DNA sequence data of five loci for each of 63 individuals collected from five continents, we have delineated two phylogenetic species in this single morphological species. Unlike all other fungi examined to date, both genetically isolated groups showed a global distribution with no evidence of a correlation between genotype and geographic location. Sexual reproduction has never been observed in A. fumigatus, but when the same data were used to explore the association of alleles at the five loci for one of the phylogenetic species, evidence was found to support recombination. The discovery of a cryptic species is medically relevant because different species are likely to differ in virulence or drug resistance. The discovery of a globally distributed A. fumigatus species clade highlights the need for ecological studies of the fungus to either document global dispersal or propose alternative mechanisms by which it persists as single, global phylogenetic population.

Aspergillus fumigatus↗

PubMed2003

Spatial grain and the causes of regional diversity gradients in ants.

Gradients of species richness (S; the number of species of a given taxon in a given area and time) are ubiquitous. A key goal in ecology is to understand whether and how the many processes that generate these gradients act at different spatial scales. Here we evaluate six hypotheses for diversity gradients with 49 New World ant communities, from tundra to rain forest. We contrast their performance at three spatial grains from S(plot), the average number of ant species nesting in a m2 plot, through Fisher's alpha, an index that treats our 30 1-m2 plots as subsamples of a locality's diversity. At the smallest grain, S(plot), was tightly correlated (r2 = 0.99) with colony abundance in a fashion indistinguishable from the packing of randomly selected individuals into a fixed space. As spatial grain increased, the coaction of two factors linked to high net rates of diversification--warm temperatures and large areas of uniform climate--accounted for 75% of the variation in Fisher's alpha. However, the mechanisms underlying these correlations (i.e., precisely how temperature and area shape the balance of speciation to extinction) remain elusive.

Animals↗

PubMed2007

Resource-based adaptive divergence in the freshwater fish Telmatherina from Lake Matano, Indonesia.

Adaptive radiations are an important source of biodiversity, but resolving which ecological pressures seed these processes in natural systems remains difficult. Here the adaptive radiation among Telmatherina, a genus of freshwater fish endemic to an ancient lake in central Sulawesi, Indonesia, was examined to determine its causal root. We demonstrate that all Telmatherina in this lake can be categorized into three lineages each possessing specialized skull shapes and pharyngeal jaw bones allowing them to exploit different resources. These data demonstrate a natural example of how resource partitioning has likely initiated adaptive radiation in a resource limited environment.

Adaptation, Biological↗

PubMed2005

Current evidence and research needs to support a health claim for selenium and cancer prevention.

Selenium was recognized as a nutritional essential only in the late 1950s. That it might also be anticarcinogenic was first suggested a decade later based on ecological relationships of cancer mortality rates and forage crop Se contents in the United States. Since that time, a substantial body of scientific evidence indicated that Se can, indeed, play a role in cancer prevention. This is supported by a remarkably consistent body of findings from studies with animal tumor and cell culture models, and by some, but not all epidemiologic observations. The body of clinical trial data is less extensive, yet also supportive. The consistent findings from this evidence are that both inorganic and organic Se-compounds can be antitumorigenic at doses greater than those required to support the maximal expression of the selenoenzymes that are generally regarded as discharging the nutritional effects of the element. Although the plausibility of Se as a cancer-protective factor is clear, other research is required to support evidence-based evaluation of this hypothesis. In addition to further, well-planned clinical trials, that research must include the development of analytical tools for speciating Se in foods and biological tissues; the development of better means of assessing Se status in ways that are relevant to cancer prevention; and the determination of the minimal dose of Se that is both safe and effective in reducing cancer risk.

Clinical Trials as Topic↗

PubMed2003

Comparative bioavailability of selenium to aquatic organisms after biological treatment of agricultural drainage water.

Selenium (Se) is naturally abundant in the soils of the western San Joaquin Valley, California, USA. Intense agricultural activity in this region requires irrigation which leaches Se into surface waters draining to the San Joaquin River. Se water contamination and subsequent accumulation in wildlife is a serious problem in the Central Valley of California, and the subject of increasingly intensive regulatory action. Algal-bacterial selenium reduction (ABSR) is a potential new treatment approach to reduce Se in agricultural drainage, and an ABSR demonstration facility was examined with respect to its Se removal efficiency and effect on Se bioavailability and bioaccumulation. Water samples were taken to study treatment effects on Se speciation. Invertebrate tissue Se concentrations in the ABSR ponds were monitored for 2 years. Laboratory-based algal bioaccumulation tests and in situ microcosms with a variety of invertebrates were also used to address differences in Se bioavailability before and after ABSR treatment. The ABSR system removed about 80% of the total influent Se; however, microbial and algal activity produced selenite and organic Se, the combined concentration of which increased 8-fold during treatment. As a result of the greater bioavailability of selenite and organic Se, relative to the selenate of the influent, treatment contributed to greater Se concentrations in effluent-exposed organisms. ABSR-treated water produced Se concentrations in biota 2-4 times greater than organisms exposed to untreated water. The bioavailability of Se in the treated water was 2-10 times greater than Se in the influent. The shift to more bioavailable Se forms due to biological treatment is inherent in system design, and makes it difficult to weigh the ecological benefits of a reduction in total Se loadings from a regional perspective against the greater toxicological risk to biota in the vicinity of the effluent.

Animals↗

PubMed1992

Symbiotic interactions in the EVOLVE III ecosystem model.

Parasitic feeding mechanisms were introduced into the EVOLVE III ecosystem model. The modified system exhibited a number of interesting behaviors, including obligative and facultative parasitism, transient facultative mutualism and nonsymbiotic feeding. Speciation and massive die-offs were also observed. The introduction of a symbiotic capability altered the co-evolutionary development of traits that exhibited an arms race when the symbiotic capability was not present. Stable mutualisms were not possible in the present version of the model due to the restriction that organisms were not allowed to feed both on other organisms and from the environment at the same time. The ecosystem biomass increased with increased symbiotic activity. Biomass was influenced by the balance of virulence and resistance traits in the population and decreased as these traits became more disparate.

Animals↗

PubMed2001

Loss of speciation rate will impoverish future diversity.

Human activities have greatly reduced the amount of the earth's area available to wild species. As the area they have left declines, so will their rates of speciation. This loss of speciation will occur for two reasons: species with larger geographical ranges speciate faster; and loss of area drives up extinction rates, thus reducing the number of species available for speciation. Theory predicts steady states in species diversity, and fossils suggest that these have typified life for most of the past 500 million years. Modern and fossil evidence indicates that, at the scale of the whole earth and its major biogeographical provinces, those steady states respond linearly, or nearly so, to available area. Hence, a loss of x% of area will produce a loss of about x% of species. Local samples of habitats merely echo the diversity available in the whole province of which they are a part. So, conservation tactics that rely on remnant patches to preserve diversity cannot succeed for long. Instead, diversity will decay to a depauperate steady state in two phases. The first will involve deterministic extinctions, reflecting the loss of all areas in which a species can ordinarily sustain its demographics. The second will be stochastic, reflecting accidents brought on by global warming, new diseases, and commingling the species of the separate bio-provinces. A new kind of conservation effort, reconciliation ecology, can avoid this decay. Reconciliation ecology discovers how to modify and diversify anthropogenic habitats so that they harbor a wide variety of species. It develops management techniques that allow humans to share their geographical range with wild species.

Animals↗

PubMed2002

Refinement and field validation of a biotic ligand model predicting acute copper toxicity to Daphnia magna.

A previously developed biotic ligand model (BLM) was validated for its capacity to predict acute 48-h EC(50) values of copper to Daphnia magna in 25 reconstituted media with different pH values and concentrations of artificial dissolved organic carbon, Ca, Mg and Na. Before the BLM validation, fitting of measured (with a copper ion-selective electrode) and calculated (with the BLM) Cu(2+)-activity was performed by adjusting the WHAM model V (i.e. the metal-organic speciation part of the BLM) copper-proton exchange constant to pK(MHA)=1.9. Using this value, the 48-h EC(50) values observed agreed very well with BLM-predicted EC(50) values for tests performed at pH<8, but not at all for tests performed at pH>8. Additional experiments demonstrated that this was due to toxicity of the CuCO(3) complex, which is the most abundant inorganic copper species at pH>8. This was incorporated into the initial BLM by allowing the binding of CuCO(3) (next to Cu(2+) and CuOH(+)) to the biotic ligand of D. magna. The affinity of CuOH(+) and CuCO(3) for the biotic ligand was approximately five- and 10-fold lower than that of Cu(2+), respectively. With the refined BLM, 48-h EC(50) values could be accurately predicted within a factor of two not only in all 25 reconstituted media, but also in 19 natural waters. This validated and refined BLM could support efforts to improve the ecological relevance of risk assessment procedures applied at present.

Animals↗

PubMed2003

Vicariance and dispersal across Baja California in disjunct marine fish populations.

Population disjunctions, as a first step toward complete allopatry, present an interesting situation to study incipient speciation. The geological formation of the Baja California Peninsula currently divides 19 species of fish into disjunct populations that are found on its Pacific Coast and in the northern part of the Gulf of California (also called the Sea of Cortez), but are absent from the Cape (Cabo San Lucas) region. We studied the genetic makeup of disjunct populations for 12 of these 19 fish species. Phylogeographic patterns for the 12 species can be separated into two major classes: a first group (eight species) showed reciprocal monophyly and high genetic divergence between disjunct populations. A second group (four species) displayed what appeared to be panmictic populations. Population structure between Pacific Coast populations, across the Punta Eugenia biogeographic boundary, was also evaluated. While dispersal potential (inferred by pelagic larval duration) was a poor predictor of population structure between Gulf of California and Pacific populations, we found that population genetic subdivision along the Pacific Coast at Punta Eugenia was always positively correlated with differentiation between Pacific and Gulf of California populations. Vicariant events, ongoing gene flow, and ecological characteristics played essential roles in shaping the population structures observed in this study.

Animals↗

PubMed2026

The Evolutionary Significance of Leaf Nodulation: Evidence from Ardisia and Its Relatives (Primulaceae: Myrsinoideae).

Interactions between plants and microorganisms have long been a central topic in biological research. Bacterial symbiosis on leaf surfaces represents a distinctive and mutually beneficial system within the phyllosphere microbiome. Leaf nodules are the visible manifestation of the symbiosis and confer ecological advantages to host plants by enhancing host resistance against pathogens and herbivores. It has been hypothesized that these advantages promote higher diversification rates in host lineages, but this remains uncertain. Ardisia subg. Crispardisia and its close relatives (Amblyanthopsis and Amblyanthus) within Primulaceae are typical plant groups with leaf nodule symbiosis, making them an ideal system for testing this hypothesis. In this study, we conducted extensive sampling of "Ardisioids" (Ardisia and its allies) and reconstructed their phylogenetic relationships and evolutionary history using plastid genomes and nuclear datasets (i.e., nuclear ribosomal DNA (nrDNA) and genome-wide single nucleotide polymorphisms (SNPs)). We clarified the phylogenetic positions of several "Ardisioids" genera (e.g., Sadiria, Tapeinosperma, Amblyanthus, and Amblyanthopsis) and multiple subgenera within Ardisia. We further detected a rapid radiation during the middle Miocene in Ardisia and its allies. Notably, we found that the leaf-nodulated clade appears to have originated during this period, approximately 11-8 Ma. BAMM (Bayesian Analysis of Macroevolutionary Mixtures) analyses revealed elevated diversification rates in leaf-nodulated lineages, while HiSSE (Hidden State Speciation and Extinction) analyses indicated that leaf nodule symbiosis might have increased speciation rates without significantly affecting extinction rates. These results provide strong evidence that leaf nodule symbiosis, together with other abiotic and biotic factors, represents a key evolutionary innovation that has promoted diversification in Ardisia and its close relatives.

diversification rate↗