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We investigated the roles of acclimation and different components involved in evolution (adaptation, chance and history) on the changes in the growth rate of the model freshwater microalga Chlamydomonas reinhardtii P. A. Dang. exposed to selective temperature and salinity. Three C. reinhardtii strains previously grown during one year in freshwater medium and 20 °C were exposed to 5 °C temperature increase and a salinity of 5 g L−1 NaCl. Cultures under each selective scenario and in combination (increase of salinity and temperature), were propagated until growth rate achieved an invariant mean value for 6 months (100–350 generations, varying as a function of scenario and strain). The changes of the growth rate under increased temperature were due to both adaptation and acclimation, as well as history. However, acclimation was the only mechanism detected under salinity increase as well as in the selective scenario of both temperature and salinity, suggesting that genetic variability would not allow survival at salinity higher than that to which experimental populations were exposed. Therefore, it could be hypothesized that under a global change scenario an increase in salinity would be a greater challenge than warming for some freshwater phytoplankton. This work was financially supported by the project CGL2017-87314-P (Ministerio de Economía, Industria y Competitividad, Spain) and the project PID2020-118045-GB-I00 (Ministerio de Ciencia e Innovación, Spain). Funding for open access charge: Universidad de Málaga/CBUA.

Se muestran los resultados obtenidos en dos Proyectos de Innovación Educativa de la Universidad de Málaga (PIE10-013 y PIE13-047), cuyos principales objetivos fueron la creación de Atlas Virtuales de Prácticas de Botánica, Flora y Vegetación, y su aplicación práctica mediante cuestionarios de autoevaluación a través del Campus Virtual. Estos atlas están publicados en la web del Departamento de Biología Vegetal de esta universidad. El Atlas de Prácticas de Botánica consta de 10 carpetas, cada una de ellas correspondientes a diferentes grupos vegetales, y un total de 482 páginas de composición de imágenes fotográficas. Actualmente, el Atlas de Flora cuenta con más de 1000 fotografías, y en él se incluyen índices alfabéticos de taxones (775) y familias (111), cada uno de ellos con su correspondiente enlace a la página de imágenes. Constituye, por tanto, un rápido y práctico buscador de imágenes de plantas, avalado además por profesores universitarios con experiencia, por lo que presenta garantía y calidad científica. El Atlas de Vegetación cuenta con cerca de 500 páginas de imágenes fotográficas, repartidas en cuatro bloques: Bosques (137), Arbustedas y Matorrales (86), Comunidades riparias (67) y Otras comunidades (103). En cada uno de ellos se incluye un índice ordenado y numerado, con objeto de facilitar la búsqueda de determinadas formaciones vegetales, así como de conocer su identidad y clasificación. Se ha creado también Atlas de Paisajes Vegetales y Atlas de Angiospermas-Flores. Todos contribuyen de manera sustancial a mejorar el proceso de enseñanza-aprendizaje en varias asignaturas de los grados de Biología y Ciencias Ambientales. Su uso y aplicación en pruebas de evaluación evita la sobrecarga de trabajo del profesorado.

La Alcarria is one of the most significant regions for honey production in Spain. Times series data of the annual Alcarria honey production from 2000 to 2013 revealed that the total production was highly variable ranging from ca. 60,000 kg in 2000 to almost three times as much in 2011, but without a remarkable trend through time. We hypothesized that these local fluctuations in honey production may be explained by broad-scale climatic patterns. Based on the multiple linear models, we found a significant positive relationship between honey production as a function of the overall means of the North Atlantic Oscillation (NAO) index and precipitation in January, which accounts for 80% of the variability in the Alcarria honey production. We propose that the effect of a negative phase of the NAO and precipitation in January could predict the Alcarria honey production a few months in advance.

Sulphide is proposed to have influenced the evolution of primary stages of oxygenic photosynthesis in cyanobacteria. However, sulphide is toxic to most of the species of this phylum, except for some sulphide-tolerant species showing various sulphide-resistance mechanisms. In a previous study, we found that this tolerance can be induced by environmental sulphidic conditions, in which two experimentally derived strains with an enhanced tolerance to sulphide were obtained from Microcystis aeruginosa, a sensitive species, and Oscillatoria, a sulphide-tolerant genus. We have now analysed the photosynthetic performance of the wild-type and derived strains in the presence of sulphide to shed light on the characteristics underlying the increased tolerance. We checked whether the sulphide tolerance was a result of higher PSII sulphide resistance and/or the induction of sulphide-dependent anoxygenic photosynthesis. We observed that growth, maximum quantum yield, maximum electron transport rate and photosynthetic efficiency in the presence of sulphide were less affected in the derived strains compared to their wild-type counterparts. Nevertheless, in 14C photoincoporation assays, neither Oscillatoria nor M. aeruginosa exhibited anoxygenic photosynthesis using sulphide as an electron donor. On the other hand, the content of photosynthetic pigments in the derived strains was different to that observed in the wild-type strains. Thus, an enhanced PSII sulphide resistance appears to be behind the increased sulphide tolerance displayed by the experimentally derived strains, as observed in most natural sulphide-tolerant cyanobacterial strains. However, other changes in the photosynthetic machinery cannot be excluded. This work was financially supported by the projects CGL2014-53862-P (Ministerio de Economía y Competitividad, Spain) and CGL2017-87314-P (Ministerio de Economía, Industria y Competitividad, Spain). EM-C was supported by grant BES-2015-072984 (Ministerio de Economía y Competitividad, Spain) and grant from Plan Propio de Investigación y Transferencia (Universidad de Málaga, Spain). Funding for open access charge: Universidad de Málaga / CBUA.

One of the most important anthropogenic impacts on freshwater aquatic ecosystems close to intensive agriculture areas is the cumulative increase in herbicide concentrations. The threat is especially relevant for phytoplankton organisms because they have the same physiological targets as the plants for which herbicides have been designed. This led us to explore the evolutionary response of three phytoplanktonic species to increasing concentrations of two herbicides and its consequences in terms of growth and photosynthesis performance. Specifically, we used an experimental ratchet protocol to investigate the differential evolution and the limit of resistance of a cyanobacterium (Microcystis aeruginosa) and two chlorophyceans (Chlamydomonas reinhardtii and Dictyosphaerium chlorelloides) to two herbicides in worldwide use: glyphosate and diuron. Initially, the growth rate of M. aeruginosa and D. chlorelloides was completely inhibited when they were exposed to a dose of 0.23 ppm diuron or 40 ppm glyphosate, whereas a higher concentration of both herbicides (0.46 ppm diuron or 90 ppm glyphosate) was necessary to abolish C. reinhardtii growth. However, after running a ratchet protocol, the resistance of the three species to both herbicides increased by an adaptation process. M. aeruginosa and D. chlorelloides were able to grow at 1.84 ppm diuron and 80 ppm glyphosate and C. reinhardtii proliferated at twice these concentrations. Herbicide-resistant strains showed lower growth rates than their wild-type coun- terparts in the absence of herbicides, as well as changes on morphology and differences on photosynthetic pigment content. Besides, herbicide-resistant cells generally showed a lower photosynthetic performance than wild-type strains in the three species. These results indicate that the introduction of both herbicides in freshwater ecosystems could produce a diminution of primary production due to the selection of herbicide-resistant mutants, that would exhibit ... This work was financially supported by the project CGL2017-87314- P (Ministerio de Economía, Industria y Competitividad, Spain). The acquisition of the FlowCAM by the University of Málaga was co-financed by the 2008-2011 FEDER program for scientific-technique infrastructure (Proposal number: UNMA08-1E005). Funding for open access charge: Universidad de Málaga/CBUA.

Here we show the state of the art about biodiversity of seaweeds and seagrasses from the Alboran Sea. For this purpose, we revised the origin and biogeographical history shaping the present biodiversity of seaweeds and seagrasses, as well as the littoral landscapes dominated by these organisms. Furthermore, the locations with relevant importance for conservation of the biodiversity are analyzed, with emphasis on future directions in the management and conservation biology. Finally, we identify the main threats to the benthic flora of macroalgae and marine angiosperms in the Alboran Sea.

Evolutionary rescue (ER) occurs when adaptation prevents extinction under lethal selection. However, the lack of empirical studies addressing the possible factors enabling ER limits our understanding of the current biodiversity crisis in the context of global change. Here we addressed the roles of environmental deterioration rate and dispersal of metapopulations on the dynamics of ER in the freshwater cyanobacterium Microcystis aeruginosa exposed to lethal salinity levels. We exposed M. aeruginosa to six combinations of two environmental deterioration rates (control = no deterioration, and progressive deterioration). Populations under progressive deterioration started with five different NaCl concentrations (from 0 to 4 g l���1 NaCl), with 2 g l���1 NaCl added twice at 4-week intervals, followed by a final increase of 4 g l���1 NaCl. Final concentrations in the experiment ranged from 8 to 12 g l���1 NaCl. Populations with no deterioration treatment spent 12 weeks in the initial concentration and were suddenly shifted to the final range concentration. To determine the effects of dispersal on the number of ER events, three dispersal modes were implemented: (i) populations were not mixed (no dispersal); (ii) six replicate populations of the same NaCl concentration were mixed together (local dispersal); and (iii) all populations of the same metapopulation were mixed together (global dispersal). Both dispersal mode and deterioration rate were very strong predictors of the ER outcome in each metapopulation. Specifically, dispersal among populations and prior stress exposure favoured the occurrence of ER events.

The pteridofloras of nine locations in the Gibraltar Arc were analyzed using a taxonomic distinctness index. We found that the index could be a proxy of historical biogeography of the pteridofloras from this area. Moreover, the value of the taxonomic distinctness index of the different locations showed relevant relationships with certain geographic variables. Finally, we hypothesize about the value of the information derived from taxonomic distinctness index for conservation of the pteridoflora in the Gibraltar Arc. La pteridoflora de nueve localidades singulares situadas en el Arco de Gibraltar ha sido analizada utilizando un índice de distinción taxonómica. Encontramos que el índice podría ser una aproximación a la historia biogeográfica de las pteridofloras de esta zona. Además, el valor del índice de distinción taxonómica de las diferentes localidades mostró relaciones relevantes con determinadas variables geográficas. Finalmente, discutimos el posible papel de la información derivada del índice de distinción taxonómica en la conservación de la pteridoflora del Arco de Gibraltar.

Intraspecific variation plays a key role in species’ responses to environmental change; however, little is known about the role of changes in environmental quality (the population growth rate an environment supports) on intraspecific trait variation. Here, we hypothesize that intraspecific trait variation will be higher in ameliorated environments than in degraded ones. We first measure the range of multitrait phenotypes over a range of environmental qualities for three strains and two evolutionary histories ofChlamydomonas reinhardtiiin laboratory conditions. We then explore how environmental quality and trait variation affect the predictability of lineage frequencies when lineage pairs are grown in indirect co-culture. Our results show that environmental quality has the potential to affect intraspecific variability both in terms of the variation in expressed trait values, and in terms of the genotype composition of rapidly growing populations. We found low phenotypic variability in degraded or same-quality environments and high phenotypic variability in ameliorated conditions. This variation can affect population composition, as monoculture growth rate is a less reliable predictor of lineage frequencies in ameliorated environments. Our study highlights that understanding whether populations experience environmental change as an increase or a decrease in quality relative to their recent history affects the changes in trait variation during plastic responses, including growth responses to the presence of conspecifics. This points towards a fundamental role for changes in overall environmental quality in driving phenotypic variation within closely-related populations, with implications for microevolution.

The cyanobacterium Microcystis aeruginosa causes most of the harmful toxic blooms in freshwater ecosystems. Some strains of M. aeruginosa tolerate low‐medium levels of salinity, and because salinization of freshwater aquatic systems is increasing worldwide it is relevant to know what adaptive mechanisms allow tolerance to salinity. The mechanisms involved in the adaptation of M. aeruginosa to salinity (acclimation vs. genetic adaptation) were tested by a fluctuation analysis design, and then the maximum capacity of adaptation to salinity was studied by a ratchet protocol experiment. Whereas a dose of 10 g NaCl L⁻¹ completely inhibited the growth of M. aeruginosa, salinity‐resistant genetic variants, capable of tolerating up to 14 g NaCl L⁻¹, were isolated in the fluctuation analysis experiment. The salinity‐resistant cells arose by spontaneous mutations at a rate of 7.3 × 10⁻⁷ mutants per cell division. We observed with the ratchet protocol that three independent culture populations of M. aeruginosa were able to adapt to up to 15.1 g L⁻¹ of NaCl, suggesting that successive mutation‐selection processes can enhance the highest salinity level to which M. aeruginosa cells can initially adapt. We propose that increasing salinity in water reservoirs could lead to the selection of salinity‐resistant mutants of M. aeruginosa.

This is the first record of the red alga Polysiphonia carettia Hollenberg (Rhodomeleaceae) in the Gulf of Gabes, Tunisia (Mediterranean Sea). This species was first described growing on the carapace of the loggerhead sea turtle Caretta caretta (L.) from Santa Catalina Island, California, USA. In the Mediterranean, it was reported only from two loggerhead turtles captured by a Spanish longline vessel. The morphology, habitat and geographical distribution of P. carettia were examined.

Se ha analizado la pteridoflora del Arco de Alborán mediante la aplicación de índices pteridoflorísticos y su correlación con variables ambientales. Asimismo se han realizado análisis de agrupamiento de taxones para definir corotipos y de componentes principales para delimitar unidades pteridogeográficas. Con todos estos datos se realiza un análisis de conservación de taxones amenazados y se valora desde un punto de vista territorial la posible declaración del área de estudio con alguna figura de protección especial.

The overall mean levels of different environmental variables are changing rapidly in the present Anthropocene, in some cases creating lethal conditions for organisms. Under this new scenario, it is crucial to know whether the adaptive potential of organisms allows their survival under different rates of environmental change. Here, we used an eco‐evolutionary approach, based on a ratchet protocol, to investigate the effect of environmental change rate on the limit of resistance to salinity of three strains of the toxic cyanobacterium Microcystis aeruginosa. Specifically, we performed two ratchet experiments in order to simulate two scenarios of environmental change. In the first scenario, the salinity increase rate was slow (1.5‐fold increase), while in the second scenario, the rate was faster (threefold increase). Salinity concentrations ranging 7–10 gL‐1 NaCl (depending on the strain) inhibited growth completely. However, when performing the ratchet experiment, an increase in salinity resistance (9.1–13.6 gL‐1 NaCl) was observed in certain populations. The results showed that the limit of resistance to salinity that M. aeruginosa strains were able to reach depended on the strain and on the rate of environmental change. In particular, a higher number of populations were able to grow under their initial lethal salinity levels when the rate of salinity increment was slow. In future scenarios of increased salinity in natural freshwater bodies, this could have toxicological implications due to the production of microcystin by this species., We used an eco‐evolutionary approach based on a ratchet protocol to investigate the effect of environmental change rate on the limit of resistance to salinity of three strains of the toxic cyanobacterium Microcystis aeruginosa. The limit of resistance to salinity that M. aeruginosa strains were able to reach depended on the strain and on the rate of environmental change.

Experimental evolution studies using cyanobacteria as model organisms are scarce despite the role of cyanobacteria in the evolution of photosynthesis. Three different experimental evolution approaches have been applied to shed light on the sulfide adaptation process, which played a key role in the evolution of this group. We used a Microcystis aeruginosa sulfide-sensitive strain, unable to grow above ~0.1 mM, and an Oscillatoria sp. strain, isolated from a sulfureous spa (~0.2 mM total sulfide). First, performing a fluctuation analysis design using the spa waters as selective agent, we proved that M. aeruginosa was able to adapt to this sulfide level by rare spontaneous mutations. Second, applying a ratchet protocol, we tested if the limit of adaptation to sulfide of the two taxa was dependent on their initial sulfide tolerance, finding that M. aeruginosa adapted to 0.4 mM sulfide, and Oscillatoria sp. to ~2 mM sulfide, twice it highest tolerance level. Third, using an evolutionary rescue approach, we observed that both speed of exposure to increasing sulfide concentrations (deterioration rate) and populations' genetic variation determined the survival of M. aeruginosa at lethal sulfide levels, with a higher dependence on genetic diversity. In conclusion, sulfide adaptation of sensitive cyanobacterial strains is possible by rare spontaneous mutations and the adaptation limits depend on the sulfide level present in strain's original habitat. The high genetic diversity of a sulfide-sensitive strain, even at fast environmental deterioration rates, could increase its possibility of survival even to a severe sulfide stress.

Benford's phenomenological law gives the expected frequencies of the first significant digit (i.e., the leftmost non-zero digit) of any given series of numbers. According to this law, the frequency of 1 is higher than that of 2; this in turn appears more often than 3, and so on decreasing until 9. Similarly, Benford's law can also be applied to the first two significant digits (i.e., from 10 to 99), and so on. We applied Benford's law to sets of taxonomic data sets consisting of the number of taxa included in taxa of higher rank. We chose the angiosperms (Magnoliophyta) as a model case, because they are very diverse, are monophyletic, and a consensus on taxonomy of orders and families has been achieved (classification APG III), and we used as sets of data the number of species, genera, families, and orders. Only the number of species per family and per order are Benford's sets, but the remaining data sets do not obey Benford. Furthermore, in the case of the analysis of the first two significant digits of ...

The cyanobacterium Microcystis aeruginosa is a mesophilic freshwater organism, which cannot tolerate sulphide. However, it was possible to isolate a sulphide-resistant (S r ) mutant strain that was able to survive in a normally lethal medium sulphide. In order to evaluate the cost of the mutation conferring sulphide resistance in the S r strain of M. aeruginosa, the morphology and the photosynthetic performance were compared to that found in the wild-type, sulphide-sensitive (S s ) strain. An increase in size and a disrupted morphology was observed in S r cells in comparison to the S s counterpart. Phycoerythrin and phycocyanin levels were higher in the S r than in the S s cells, whereas a higher carotenoid content, per unit volume, was found in the S s strain. The irradiance-saturated photosynthetic oxygen-production rate (GPR max) and the photosynthetic efficiency (measured both by oxygen production and fluorescence, α GPR and α ETR) were lower in the S r strain than in the wild-type. These results appear to be the result of package effect. On the other hand, the S r strain showed higher quantum yield of non-photochemical quenching, especially those regulated mechanisms (estimated throughout q N and Y(NPQ)) and a significantly lower slope in the maximum quantum yield of light-adapted samples (F v ′/F m ′) compared to the S s strain. These findings point to a change in the regulation of the quenching of the transition states (q T ) in the S r strain which may be generated by a change in the distribution of thylakoidal membranes, which somehow could protect metalloenzymes of the electron transport chain from the lethal effect of sulphide.

Mechanisms of inorganic carbon assimilation were investigated in the four deep-water kelps inhabiting sea bottoms at the Strait of Gibraltar; these species are distributed at different depths (Saccorhiza polysiches at shallower waters, followed by Laminaria ochroleuca, then Phyllariopsis brevipes and, at the deepest bottoms, Phyllariopsis purpurascens). To elucidate the capacity to use HCO3(-) as a source of inorganic carbon for photosynthesis in the kelps, different experimental approaches were used. Specifically, we measured the irradiance-saturated gross photosynthetic rate versus pH at a constant dissolved inorganic carbon (DIC) concentration of 2 mM, the irradiance-saturated apparent photosynthesis (APS) rate versus DIC, the total and the extracellular carbonic anhydrase (CAext), the observed and the theoretical photosynthetic rates supported by the spontaneous dehydration of HCO3(-) to CO2, and the δ(13)C signature in tissues of the algae. While S. polyschides and L. ochroleuca showed photosynthetic activity at pH 9.5 (around 1.0 µmol O2 m(-2) s(-1)), the activity was close to zero in both species of Phyllariopsis. The APS versus DIC was almost saturated for the DIC values of natural seawater (2 mM) in S. polyschides and L. ochroleuca, but the relationship was linear in P. brevipes and P. purpurascens. The four species showed total and CAext activities but the inhibition of the CAext originated the observed photosynthetic rates at pH 8.0 to be similar to the theoretical rates that could be supported by the spontaneous dehydration of HCO3(-). The isotopic (13)C signatures ranged from -17.40 ± 1.81 to -21.11 ± 1.73 ‰ in the four species. Additionally, the δ(13)C signature was also measured in the deep-water Laminaria rodriguezii growing at 60-80 m, showing even a more negative value of -26.49 ± 1.25 ‰. All these results suggest that the four kelps can use HCO3(-) as external carbon source for photosynthesis mainly by the action of external CAext, but they also suggest that the species inhabiting shallower waters show a higher capacity than the smaller kelps living in deeper waters. In fact, the photosynthesis in the two Phyllariopsis species could be accomplished by the spontaneous dehydration of HCO3(-) to CO2. These differences in the capacity to use HCO3(-) in photosynthesis among species could be important considering the increasing levels of atmospheric CO2 predicted for the near future.

Se realiza una recensión de los 38 volúmenes de Acta Botanica Malacitana, así como de los dos números de Trabajos y Monografías del Departamento de Botánica. Así mismo se realiza un análisis bibliométrico y se construyen varios índices de autores, temáticas y novedades corológicas, taxonómicas y sintaxonómicas.

The ecological factors driving the occurrence of harmful algal blooms (HAB) have been traditionally analysed from a hydrological point of view, whereas the interplay between atmospheric oscillations and HAB has been scarcely explored. Here we address the possible link between atmospheric oscillations in SW Europe, using as proxies the North Atlantic Oscillation (NAO) and the Arctic Oscillation (AO) indices and the interannual variability in HAB. The yearly series (1973–2005) of mortality of water birds and fish in Donana National Park (SW Spain) due to toxins associated with the cyanobacterium Microcystis aeruginosa, and the monthly incidence (January 1999 to December 2007) of the paralytic shellfish poisoning (PSP) toxin produced by the dinoflagellate Gymnodinium catenatum in the Rias Baixas (NW Spain), were selected as models of HAB in SW Europe. The incidences of both toxic algal events were fitted to a binary logistic regression as a function of the atmospheric oscillation indices (with different delays in accordance with each toxic event) and a favourability function was then computed. The favourability for the wildlife mortality in Donana National Park was as a function of the AO averaged for the summer period (June–August) whereas the favourability for the incidence of PSP in the Rias Baixas was a function of the NAO recorded 1 month before the event. Since HAB have a relevant impact on ecosystems and human health, there is great interest in deciphering the ecological conditions favouring these events. Here we show that the atmospheric oscillations could be drivers of ecological processes linked to the occurrence of HAB in SW Europe. Moreover, the favourability functions relating NAO and AO indices with algal toxic events in SW Europe could be used as a powerful tool to predict toxic events.

The continental sedimentary record of the Baza Basin (Guadix–Baza Depression, Betic Cordillera, SE Spain) shows six sedimentary units of lacustrine origin deposited from the latest Miocene to the Middle Pleistocene. Depending on the interval considered, the lacustrine deposits are mainly composed of marls, carbonates or gypsiferous evaporites, showing lithological, mineralogical and geochemical features (i.e., magnesium, strontium and sulfur contents, celestine deposits and travertine growths) that are evidence of intense, tectonically-induced hydrothermal activity. According to the high concentrations of strontium and sulfur as well as the abundance of travertines and magnesium clays, the supply of hot waters was greater during the Zanclean, the Gelasian and the Calabrian, as a result of tectonic activity. Hydrothermal activity has continued until the present time and is responsible of the hot springs that are nowadays active in the Guadix–Baza Depression. The paleoenvironmental consequences of these sublacustrine hot springs were that during some intervals the lakes maintained a relatively permanent water table, not subject to periodic desiccations in the dry season, and warmer temperatures throughout the year. This resulted in a high level of organic productivity, especially for the Calabrian, which allowed the development of a rich and well diversified mammalian community, similar to those of modern African savannas with tree patches. In this mild environment, the permanent water sheet favored the presence of drought intolerant megaherbivores such as the giant extinct hippo Hippopotamus antiquus. The high standing crop biomass of ungulates resulted in the availability of abundant carcasses for scavengers such as hyenas and hominins, which explains the very high densities of skeletal remains preserved in the sediments distributed along the lake surroundings.

English. The cyanobacterium Microcystis aeruginosa (Kützing) Kützing is notorious for forming extensive and toxic blooms but the genetic structure of natural populations, and in particular during blooms, remains to be explored. In order to add more knowledge about the genetic structure of M. aeruginosa, we compared phenotypic and genetic variabilities in seventeen strains of M. aeruginosa isolated from three adjacent water bodies in SW Spain (the consecutive reservoirs La Minilla and El Gergal, and small pools in Doñana National Park). For this purpose, a phenetic tree, based on six phenotypic traits (including morphology of cells, photosynthetic and respiratory performance, and toxin production) was compared with a phylogenetic tree built by using the 16S-23S rDNA Internal Transcribed Spacer sequence. Whereas the strains isolated from La Minilla showed a relatively homogeneous phenotype, the phenotypic traits of the remaining strains did not discriminate between the other two water bodies. On the other hand, only a strain isolated in Doñana National Park showed a slightly different ITS sequence, but the sequences from the remaining strains were similar. Possible explanations for this discrepancy between phenotypic and genetic diversities are discussed.Español. La cianobacteria Microcystis aeruginosa (Kützing) Kützing puede dar lugar a extensas floraciones tóxicas pero la estructura genética de las poblaciones naturales, y en particular durante las floraciones, ha sido escasamente estudiada. Con el objeto de profundizar en la estructura genética de M. aeruginosa, se han comparado las variabilidades fenotípica y genética de diecisiete cepas aisladas de tres cuerpos de agua adyacentes en el SW de España (los embalses consecutivos de La Minilla y El Gergal, y charcas en el Parque Nacional de Doñana). Para este fin, un árbol de similitud fenética basado en seis caracteres fenotípicos (que incluyen la morfología de las células, el rendimiento fotosintético y respiratorio y la producción de toxina) se comparó con un árbol filogenético construido mediante el uso de la secuencia de ITS 16S - 23S del ADNr. Las cepas aisladas en La Minilla mostraron un fenotipo relativamente homogéneo pero no se detectó un patrón de fenotipos que discriminase los otros dos cuerpos de agua. Por otro lado, sólo una cepa aislada en el Parque Nacional de Doñana mostró una secuencia ITS diferente, pero las secuencias de las cepas restantes fueron idénticas. Se discuten las posibles explicaciones para esta discrepancia entre la diversidad fenotípica y genética en M. aeruginosa.

Los Baños de Vilo (S Spain) is a natural spa characterized by extreme sulphureous waters; however, populations of chlorophyceans inhabit in the spa. The adaptation mechanisms allowing resistance by photosynthetic microorganisms to the extreme sulphureous waters were studied by using a modified Luria-Delbrück fluctuation analysis. For this purpose, the adaptation of the chlorophycean Dictyosphaerium chlorelloides and the cyanobacterium Microcystis aeruginosa (both isolated from non-sulphureous water) were analysed in order to distinguish between physiological adaptation (acclimation) and genetic adaptation by the selection of rare spontaneous mutations. Acclimation to the extreme water was achieved by D. chlorelloides; however, M. aeruginosa cells proliferated as a consequence of selection of favoured mutants (i.e. genetic adaptation). The resistant cells of M. aeruginosa appeared with a frequency of 7.1 × 10(-7) per cell per generation, and the frequency of the resistant allele, under non-selective conditions, was estimated to be 1.1 × 10(-6) per cells as a consequence of the balance mutation-selection. It could be hypothesized that the populations of eukaryotic algae living in the Los Baños de Vilo could be the descendants of chlorophyceans that arrived fortuitously at the spa in the past. On the other hand, cyanobacteria could quickly adapt by the selection of favoured mutants. The single mutation that allows resistance to sulphureous water from Baños de Vilo in M. aeruginosa represents a phenotypic burden impairing growth rate and photosynthetic performance. The resistant-variant cells of M. aeruginosa showed a lower acclimated growth rate and a decreased maximum quantum yield and photosynthetic efficiency, in comparison to the wild-type cells.

The cyanobacterium Microcystis aeruginosa forms blooms that can consist of colonies. We have investigated how M. aeruginosa acclimatizes to changing light conditions such as can occur during blooms. Three different strains were exposed to two irradiance levels: lower (LL) and higher (HL) than the irradiance-onset saturation parameter. We measured the photosynthetic pigment concentrations, PSII photochemical efficiency, electron transport rate (ETR), irradiance-saturated ETR and ETR efficiency. The relationship between ETR and photosynthetic oxygen production and the excess in PSII capacity were also studied for one strain. Higher values of chlorophyll a and phycocyanin and lower values of total carotenoids were found under LL conditions in the three strains. The strains showed clear differences in the irradiance-saturated ETR and in ETR efficiency under both LL and HL treatments. No differences were found in the linear relationship between ETR and photosynthetic oxygen production under both irradiance treatments. LL-acclimated cells showed higher PSII excess capacity than HL ones, possibly because their higher pigment content could result in a higher light stress than HL cells when forming surface blooms. The fact that the genetically different strains show different photosynthetic physiologies suggests that the very dynamic light climate observed in lakes may allow their coexistence.

The roles of adaptation, chance, and history on evolution of the toxic dinoflagellate Alexandrium minutum Halim, under selective conditions simulating global change, have been addressed. Two toxic strains (AL1V and AL2V), previously acclimated for two years at pH 8.0 and 20°C, were transferred to selective conditions: pH 7.5 to simulate acidification and 25°C. Cultures under selective conditions were propagated until growth rate and toxin cell quota achieved an invariant mean value at 720 days (ca. 250 and ca. 180 generations for strains AL1V and AL2V, respectively). Historical contingencies strongly constrained the evolution of growth rate and toxin cell quota, but the forces involved in the evolution were not the same for both traits. Growth rate was 1.5–1.6 times higher than the one measured in ancestral conditions. Genetic adaptation explained two-thirds of total adaptation while one-third was a consequence of physiological adaptation. On the other hand, the evolution of toxin cell quota showed a pattern attributable to neutral mutations because the final variances were significantly higher than those measured at the start of the experiment. It has been hypothesized that harmful algal blooms will increase under the future scenario of global change. Although this study might be considered an oversimplification of the reality, it can be hypothesized that toxic blooms will increase but no predictions can be advanced about toxicity.

We tested if different adaptation strategies were linked to a stress gradient in phytoplankton cells. For this purpose, we studied the adaptation and acclimation of Dictyosphaerium chlorelloides (Naumann) Komarek et Perman (Chlorophyta) and Microcystis aeruginosa (Kutz.) Kutz. (Cyanobacteria) to different water samples (from extremely acid, metal-rich water to moderate stressful conditions) of the Agrio River-Caviahue Lake system (Neuquen, Argentina). Both experimental strains were isolated from pristine, slightly alkaline waters. To distinguish between physiological acclimation and genetic adaptation (an adaptive evolution event), a modified Luria-Delbruck fluctuation analysis was carried out with both species by using as selective agent sample waters from different points along the stress gradient. M. aeruginosa did not acclimate to any of the waters tested from different points along the stress gradient nor did D. chlorelloides to the two most acidic and metal-rich waters. However, D. chlorelloides proliferated by rapid genetic adaptation, as the consequence of a single mutation (5.4 × 10(-7) resistant mutants per cell per division) at one locus, in less extreme water and also by acclimation in the least extreme water. It is hypothesized that the stress gradient resulted in different strategies of adaptation in phytoplankton cells from nonextreme waters. Thus, very extreme conditions were lethal for both organisms, but as stressful conditions decreased, adaptation of D. chlorelloides cells was possible by the selection of resistant mutants, and in less extreme conditions, by acclimation.

Toxic blooms of the cyanobacterium Microcystis aeruginosa affect humans and animals in inland water systems worldwide, and it has been hypothesized that the development of these blooms will increase under the future scenario of global change, considering eutrophication and temperature increase as two important consequences. The importance of genetic adaptation, chance and history on evolution of growth rate, and toxin production of M. aeruginosa was studied under these new conditions. The experiment followed the idea of "replaying life's tape" by means of the simultaneous propagation of 15 independent isolates of three M. aeruginosa strains, which were grown under doubled nutrient concentration and temperature during c. 87 generations. Adaptation by new mutations that resulted in the enhancement of growth rate arose during propagation of derived cultures under the new environmental conditions was the main component of evolution; however, chance also contributed in a lesser extension to evolution of growth rate. Mutations were selected, displacing the wild-type ancestral genotypes. In contrast, the effect of selection on mutations affecting microcystin production was neutral. Chance and history were the pacemakers in evolution of toxin production. Although this study might be considered an oversimplification of the reality, it suggest that a future scenario of global change might lead to an increase in M. aeruginosa bloom frequency, but no predictions about the frequency of toxicity can be made.

Aquatic ecosystems located close to agricultural areas are increasingly polluted by herbicides. We evaluated the capacity for adaptation of green microalgae to lethal concentrations of the herbicide simazine in one strain of Dictyosphaerium chlorelloides and two strains of Scenedesmus intermedius, as well as adaptation to the herbicide diquat in one of the strains of S. intermedius. A Luria–Delbruck fluctuation analysis was carried out in order to distinguish between resistant cells arising from physiological adaptation (acclimatization) or post-adaptive mutation (both events occurring after the exposure to the herbicides), and adaptation due to mutations before the exposure to the herbicides. Simazine-resistant cells arose by rare spontaneous mutations before the exposure to simazine, with a rate of 3.0 × 10−6 mutants per cell per generation in both strains of S. intermedius, and of 9.2 × 10−6 mutants per cell per generation in D. chlorelloides. Diquat-resistant cells in S. intermedius arose by pre-selective mutations with a rate of 17.9 × 10−6 per cell per generation. Rare, pre-selective mutations may allow the survival of green microalgae in simazine- or diquat-polluted waters, via herbicide-resistant selection. Therefore, human-synthesized pollutants, such as the herbicides simazine and diquat, could cause the emergence of evolutionary novelties in aquatic environments.

Benford’s phenomenological law gives the expected frequencies of the first significant digits of any given series of numbers. According to this law, the frequency of 1 is higher than that of 2; this in turn appears more often 3, and so on. Similarly, Benford’s law can also be applied to the first two significant digits (i.e., from 10 to 99), and so on. Here, we show that gross data sets of daily pollen counts from three aerobiological stations (located in European cities with different features regarding vegetation and climatology) fit Benford’s law for the first significant digits, but this is not always true for the data transformed by a correction factor used in aerobiological studies. That is to say, the biases introduced by rounding and lower and upper built-in limits in pollen counts are detected by Benford’s law analysis. The analysis of the first two significant digits from transformed data is better explained by a Power law than Benford’s law. We propose that Benford’s law could be used as a quality control tool for numerical aerobiological data sets.

SUMMARY Four species of eukaryotic algae proliferate in the sul- fureous, acidic (pH 3.1) water of the largest geothermal pond on Vulcano Island (southern Italy). Consequently, this pond constitutes a natural laboratory for analysis of adaptation by phytoplankters to extremely stressful conditions. To distinguish between the pre-selective or post-selective origin of adaptation processes allowing the existence of phytoplankters in the pond, a Luria- Delbruck fluctuation test was carried out with the chlorophycean Dictyosphaerium chlorelloides and the cyanobacterium Microcystis aeruginosa, both isolated from non-extreme waters; natural water from the Vulcano Island pond was used as selective factor. Pre- selective, resistant D. chlorelloides cells appeared with a frequency of 4.7 ¥ 10 -7 per cell per generation. We propose that the micro-algae inhabiting this stressful pond could be the descendents of chance mutants that arrived in the past or are even arriving at the present. The genetic adaptation of D. chlorelloides to Vulcano waters could help to explain the survival of photosyn- thesizers in very stressful geothermal waters during the Neoproterozoic 'snowball Earth', a period when primary production collapsed in the biosphere. On the other hand, adaptation to these conditions was not observed in M. aeruginosa, suggesting that cyanobacteria may not be able to develop any kind of adaptation to Vulcano pond water.

At least six species of eukaryotic microalgae inhabit the acidic (pH 2.4–2.7), metal-rich mine waters from ponds in the copper mine district of Mynydd Parys (N Wales, UK). Consequently, these ponds constitute interesting natural laboratories for analysis of adaptation by microalgae to extremely stressful conditions. To distinguish between the pre-selective and post-selective origin of adaptation processes that allow the existence of microalgae in these ponds, a Luria-Delbruck fluctuation analysis was performed with the chlorophycean Dictyosphaerium chlorelloides isolated from non-acidic waters. In this analysis, natural Mynydd Parys pond water (MPW) was used as selective factor. Pre-selective, resistant D. chlorelloides cells appeared with a frequency of 1.6 × 10−6 per cell per generation. MPW-resistant mutants, with a diminished Malthusian fitness, are maintained in non-extreme waters as the result of a balance between new MPW-resistant cells arising by mutation and MPW-resistant mutants eliminated by natural selection (equilibrium at ca. 19 MPW-resistant per 107 wild-type cells). We propose that the microalgae inhabiting these stressful ponds could be the descendents of chance mutants that arrived in the past or are even arriving at the present.

Several species of microalgae, closely related to mesophilic lineages, inhabit the extreme environment (pH 2.5, high levels of metals) of the Spain’s Aguas Agrias Stream water (AASW). Consequently, AASW constitutes an interesting natural laboratory for analysis of adaptation by microalgae to extremely stressful conditions. To distinguish between the pre-selective or post-selective origin of adaptation processes allowing the existence of microalgae in AASW, a Luria–Delbruck fluctuation analysis was performed with the chlorophycean Dictyosphaerium chlorelloides isolated from non-acidic waters. In the analysis, AASW was used as selective factor. Preselective, resistant D. chlorelloides cells appeared with a frequency of 1.1 × 10 −6 per cell per generation. AASW-resistant mutants, with a diminished Malthusian fitness, are maintained in non-extreme waters as the result of a balance between new AASW-resistant cells arising by mutation and AASW-resistant mutants eliminated by natural selection (equilibrium at c . 12 AASW-resistants per 10 7 wild-type cells). We propose that the microalgae inhabiting this stressful environment could be the descendents of chance mutants that arrived in the past or are even arriving at the present.

Evolutionary changes depend on adaptive evolution and two other components that traditionally have not been taken into account: chance and history. However, concepts in evolutionary biology are very often supported by descriptive studies but not by empirical approach. In order to disentangle the three components of evolutionary change, we have investigated the effects of long-term selection pressure on fitness and cell size in the bloom-forming dinoflagellate, Prorocentrum triestinum Schiller, under increased nutrient concentrations and temperature. Two strains of P. triestinum, previously adapted to grow under standard conditions (f/2 medium, 20 degrees C), were grown under increased nutrient concentrations and temperature (f medium, 25 degrees C) until fitness and cell size were invariant as a function of time (720 days, corresponding to c. 400 generations). The mean value for fitness of both strains of P. triestinum showed a significant increase whereas a decrease in mean cell size was found. The changes in fitness have adaptive value, but the changes in cell size were due to both adaptation and the contribution of chance-plus-history.

We tested if different adaptation strategies were linked to a stress gradient in phytoplankton cells. For this purpose, we studied the adaptation and acclimation of Dictyosphaerium chlorelloides (Naumann) Komárek et Perman (Chlorophyta) and Microcystis aeruginosa (Kütz.) Kütz. (Cyanobacteria) to different water samples (from extremely acid, metal-rich water to moderate stressful conditions) of the Agrio River-Caviahue Lake system (Neuquén, Argentina). Both experimental strains were isolated from pristine, slightly alkaline waters. To distinguish between physiological acclimation and genetic adaptation (an adaptive evolution event), a modified Luria-Delbrück fluctuation analysis was carried out with both species by using as selective agent sample waters from different points along the stress gradient. M. aeruginosa did not acclimate to any of the waters tested from different points along the stress gradient nor did D. chlorelloides to the two most acidic and metal-rich waters. However, D. chlorelloides proliferated by rapid genetic adaptation, as the consequence of a single mutation (5.4 × 10(-7) resistant mutants per cell per division) at one locus, in less extreme water and also by acclimation in the least extreme water. It is hypothesized that the stress gradient resulted in different strategies of adaptation in phytoplankton cells from nonextreme waters. Thus, very extreme conditions were lethal for both organisms, but as stressful conditions decreased, adaptation of D. chlorelloides cells was possible by the selection of resistant mutants, and in less extreme conditions, by acclimation.

Although populations of cyanobacteria are usually considered to be clonal, their capacity to survive environmental changes suggests intrapopulation genetic variation. We therefore estimated the genetic variability on the basis of two processes important for any photoautotroph - photochemical and nonphotochemical quenching - as well as photosynthetic pigment concentrations. For this purpose, two parameters related to photochemical and nonphotochemical quenching were measured using specific experimental and statistical procedures, in 25 strains of the cyanobacterium Microcystis aeruginosa, along with their contents of chlorophyll a, total carotenoids and phycocyanin. The experimental procedure allowed discrimination between genetic and nongenetic (or residual) variability among strains. The high genetic variability found in photosynthetic pigments and both photosynthetic parameters denotes large differences even among strains isolated from the same community. The high genetic diversity within a population could be important for the evolutionary success of cyanobacteria.

Adaptation of Microcystis aeruginosa (Cyanobacteria) to resist the herbicide glyphosate was analysed by using an experimental model. Growth of wild-type, glyphosate-sensitive (Gs) cells was inhibited when they were cultured with 120 ppm glyphosate, but after further incubation for several weeks, occasionally the growth of rare cells resistant (Gr) to the herbicide was found. A fluctuation analysis was carried out to distinguish between resistant cells arising from rare spontaneous mutations and resistant cells arising from other mechanisms of adaptation. Resistant cells arose by rare spontaneous mutations prior to the addition of glyphosate, with a rate ranging from 3.1 × 10−7 to 3.6 × 10−7 mutants per cell per generation in two strains of M. aeruginosa; the frequency of the Gr allele ranged from 6.14 × 10−4 to 6.54 × 10−4. The Gr mutants are slightly elliptical in outline, whereas the Gs cells are spherical. Since Gr mutants have a diminished growth rate, they may be maintained in uncontaminated waters as the result of a balance between new resistants arising from spontaneous mutation and resistants eliminated by natural selection. Thus, rare spontaneous pre-selective mutations may allow the survival of M. aeruginosa in glyphosate-polluted waters via Gr clone selection.

Inter-strain variability in pH compensation point (pH c ) in the cyanobacterium Microcystis aeruginosa has been investigated. The pH c allows one to discriminate whether the organism is able to take up HCO 3 − as inorganic carbon (C i ) source in photosynthesis. Eight subgroups were found according to the pH c value, ranging from 10.44 ± 0.22 to 11.67 ± 0.05. The high variability in pH c (and consequently, in the capacity to use HCO 3 − as C i source) suggested that different HCO 3 − use mechanisms could occur in M. aeruginosa and, from an evolutionary point of view, this trait is not under high natural selective pressure.

SUMMARY The aim of the present paper is to identify the possible existence of groups of species in the genera Audouinella (Rhodophyta), Cystoseira (Phaeophyceae) and Cladophora (Chloropyta) with significantly similar distribution patterns (chorotypes), in the western Mediterranean Sea and the Adriatic Sea. Of the 98 species studied, 59 were grouped into 11 chorotypes, whereas 39 species remained ungrouped. Thirty-eight species were included in a generalist chorotype, whereas 6 chorotypes were monospecific. The relationships with the environmental factors that could explain the chorotypes are discussed.

RESUMEN. Revisión crítica de los estudios sobre biogeografía de macroalgas marinas del Mediterráneo. Teniendo en cuenta los procedimientos metodológicos que se siguen en los estudios biogeográficos, se reconocen tres tipos básicos de aproximaciones: biogeografía descriptiva, biogeografía narrativa y biogeografía analítica. En este trabajo se analizan las aportaciones realizadas a la ficogeografía de las macroalgas marinas del mar Mediterráneo, atendiendo a cada una de las tres aproximaciones posibles. Existen escasas floras del Mediterráneo oriental y la costa africana, además de un estancamiento metodológico en los estudios narrativos y analíticos, impidiendo el avance de la ficogeografía. Se discuten las posibles líneas futuras de investigación con el objeto de incentivar un avance significativo en los conocimientos ficogeográficos del Mediterráneo.Palabras clave. Biogeografía analítica, biogeografía descriptiva, biogeografía narrativa, macroalgas, Mediterráneo.SUMARY. Critical review of the studies on biogeography of seaweeds from the Mediterranean Sea. Seaweed biogeography, like subdiscipline of the biogeography, could be divided on the basis of methodological approach used: descriptive biogeography, narrative biogeography and analytic biogeography. In this paper, we analyse the contributions to the biogeography of seaweeds from the Mediterranean Sea, in accordance with each one of these approaches. Scarce floras of the Mediterranean eastern and African coast exist, besides a methodological stagnation, impeding the advance of this science with regard to other branches of the biogeography. Possible future research lines are discussed and proposed.Key words. Analytical biogeography, descriptive biogeography, narrative biogeography, Mediterranean Sea, seaweeds.

Measurements of relative growth rates (RGR) of germlings of three species of Fucus (Fucales, Phaeophyceae) collected in Helgoland (North Sea, Germany) were carried out in the laboratory in order to determine the effects of different ultraviolet radiation (UVR, λ = 280–400 nm) conditions, UVR doses and temperatures. High ultraviolet-B radiation (UVBR, λ = 280–315 nm) levels and low temperature, as independent factors, led to a species-specific reduction in RGR which appears to be related to the vertical distribution of the species in the intertidal zone. The inhibition of RGR ranged from 10% to even death of the germling. For the most sensitive species, high temperature in combination with a high dose of UVBR caused the death of the germlings, whereas at low temperature germlings were able to survive. This suggest growth-related temperature dependence of sensitivity to UVBR. © 2002 Elsevier Science B.V. All rights reserved.

The increasing rates of global extinction due to human activities necessitate studies of the ability of organisms to adapt to the new environmental conditions resulting from human disturbances. We investigated the evolutionary adaptation of a microalga to sudden environmental change resulting from exposure to novel toxic chemical residues. A laboratory strain of Dictyosphaerium chlorelloides (Naum.) Kom. and Perm. (Chlorophyceae) was exposed to increasing concentrations of the modern contaminant 2,4,6-trinitrotoluene (TNT). When algal cultures were exposed to 30 mg.L - 1 TNT, massive lysis of microalgal cells was observed. The key to understanding the evolution of microalgae in such a contaminated environment is to characterize the TNT-resistant variants that appear after the massive lysis of the TNT-sensitive cells. A fluctuation analysis demonstrated unequivocally that TNT did not facilitate the appearance of TNT-resistant cells; rather it was found that TNT-resistant cells appeared spontaneously by rare mutations under nonselective conditions, before exposure to TNT. The estimated mutation rate was 1.4 X 10 - 5 mutants per cell division. Isolated resistant mutants exhibited a diminished fitness in the absence of TNT. Moreover, the gross photosynthetic rate of TNT-resistant mutants was significantly lower than that of wild-type cells. Competition experiments between resistant mutants and wild-type cells showed that in small populations, the resistant mutants were driven to extinction. The balance between mutation rate and the rate of selective elimination determines the occurrence of about 36 TNT-resistant mutants per million cells in each generation. These scarce resistant mutants are the guarantee of potential for adaptation.