Beatriz Martín

Natal dispersal in great bustards: the effect of sex, local population size and spatial isolation

1. We investigated the causes of natal dispersal in four Spanish areas where 35 breeding groups of the polygynous great bustard Otis tarda were monitored intensively. A total of 392 juveniles were radio-tracked between 1991 and 2006 by ground and via aeroplane to avoid potential biases derived from the non-detection of long-distance dispersers. 2. We explored 10 explanatory variables that were related to individual phenotypic features, habitat and conspecific traits in terms of group size and breeding performance, and spatial distribution of available breeding groups. Probability of group change and natal dispersal distances were investigated separately through multifactorial analyses. 3. Natal dispersal occurred in 47.8% of the birds and median natal dispersal distance of dispersers was 18.1 km (range 4.97-178.42 km). Sex largely determined the dispersal probability, with 75.6% of males being dispersers and 80.0% of females being philopatric, in contrast to the general pattern of female-biased dispersal found in most avian species. 4. Both the frequency of natal dispersal and dispersal distances were affected by the spatial distribution of breeding groups. More isolated groups showed a higher proportion of philopatric individuals, the effect being more evident in males than in females. This implies a reduction in gene flow in fragmented populations, as most genetic exchange is achieved through male dispersal. Additionally, dispersers hatched in more isolated groups tended to exhibit longer dispersal distances, which increases the associated energetic costs and mortality risks. 5. The dispersal decision was influenced by the number of conspecifics in the natal group. The individual probability of natal dispersal was related inversely to the size of the natal group, which supports the balanced dispersal model and the conspecific attraction hypothesis. 6. Overall, our results provide a good example of phenotypic plasticity and reinforce the current view that dispersal is an evolutionary complex trait conditioned by the interaction of individual, social and environmental causes that vary between individuals and populations.

A high-density collection of EMS-induced mutations for TILLING in Landsberg erecta genetic background of Arabidopsis.

BackgroundArabidopsis thaliana is the main model species for plant molecular genetics studies and world-wide efforts are devoted to identify the function of all its genes. To this end, reverse genetics by TILLING (Targeting Induced Local Lesions IN Genomes) in a permanent collection of chemically induced mutants is providing a unique resource in Columbia genetic background. In this work, we aim to extend TILLING resources available in A. thaliana by developing a new population of ethyl methanesulphonate (EMS) induced mutants in the second commonest reference strain. In addition, we pursue to saturate the number of EMS induced mutations that can be tolerated by viable and fertile plants.ResultsBy mutagenizing with different EMS concentrations we have developed a permanent collection of 3712 M2/M3 independent mutant lines in the reference strain Landsberg erecta (Ler) of A. thaliana. This population has been named as the Arabidopsis TILLer collection. The frequency of mutations per line was maximized by using M1 plants with low but sufficient seed fertility. Application of TILLING to search for mutants in 14 genes identified 21 to 46 mutations per gene, which correspond to a total of 450 mutations. Missense mutations were found for all genes while truncations were selected for all except one. We estimated that, on average, these lines carry one mutation every 89 kb, Ler population providing a total of more than five million induced mutations. It is estimated that TILLer collection shows a two to three fold higher EMS mutation density per individual than previously reported A. thaliana population.ConclusionsAnalysis of TILLer collection demonstrates its usefulness for large scale TILLING reverse genetics in another reference genetic background of A. thaliana. Comparisons with TILLING populations in other organisms indicate that this new A. thaliana collection carries the highest chemically induced mutation density per individual known in diploid species.

Analysis of the Effects of Daunorubicin and WP631 on Transcription

The proficiency with which anthracyclines and other DNA-binding drugs target certain sequences in eukaryotic promoters offers a potential approach to interfere with the mechanisms that regulate gene expression in tumor cells. An in vitro transcription assay has been used to compare the ability of the bisintercalating anthracycline WP631 and the monointercalating anthracycline daunorubicin in terms of their ability to inhibit initiation of transcription of the adenovirus major late promoter linked to a G-less transcribed DNA template. Both drugs inhibit basal transcription by RNA polymerase II. However, WP631 is approximately 15 times more efficient at inhibiting transcription initiation from an adenovirus promoter containing an upstream Sp1-protein binding site. The differences in the ability of each drug to inhibit transcription initiation appear to be related to the competition between Sp1 and the anthracyclines for binding to the same site. To see whether WP631s strong effect on transcription can also be observed in cells, we compared the effects of WP631 and other anthracyclines on the transcription of the c-myc gene, which promoter contains Sp1 binding sites. The resulting data suggest that WP631 might circumvent some kinds of tumor resistance at rather low drug concentrations, inhibit c-myc expression in some cell lines, and exert its antitumoral effect by inducing apoptosis.

The Most Extreme Sexual Size Dimorphism Among Birds: Allometry, Selection, and Early Juvenile Development in the Great Bustard (Otis tarda)

ABSTRACT. n The Great Bustard (Otis tarda) is one of the heaviest flying birds and the most sexually dimorphic living bird. Adult males weighed 2.48x more than females, and their linear measurements were 18–30% larger. Weight increased between the prebreeding and breeding seasons by 16% in females and 20% in males. Sexual size dimorphism emerges very early in development and explains why growth in males is so costly. Weight and central toe length were hyperallometric when related to wing length in males but isometric in females and varied more in males, as compared with females and with other male traits. Although hyperallometry and high variability have frequently been used to invoke sexual selection as a driving force, our results support different functional hypotheses for the evolution of each trait. Male—male competition is intense in this lekking species, and high rank among males and access to females are weight-dependent. Thus, sexual selection has likely pushed male weight close to the limit imposed by powered flight. Because Great Bustards are mostly cursorial, the hyperallometry of the central toes of males in relation to wing length most likely evolved for support and balance.

Environmental and genetic interactions reveal FLOWERING LOCUS C as a modulator of the natural variation for the plasticity of flowering in Arabidopsis

The timing of flowering initiation depends strongly on the environment, a property termed as the plasticity of flowering. Such plasticity determines the adaptive potential of plants because it provides phenotypic buffer against environmental changes, and its natural variation contributes to evolutionary adaptation. We addressed the genetic mechanisms of the natural variation for this plasticity in Arabidopsis thaliana by analysing a population of recombinant inbred lines derived from Don-0 and Ler accessions collected from distinct climates. Quantitative trait locus (QTL) mapping in four environmental conditions differing in photoperiod, vernalization treatment and ambient temperature detected the folllowing: (i) FLOWERING LOCUS C (FLC) as a large effect QTL affecting flowering time differentially in all environments; (ii) numerous QTL displaying smaller effects specifically in some conditions; and (iii) significant genetic interactions between FLC and other loci. Hence, the variation for the plasticity of flowering is determined by a combination of environmentally sensitive and specific QTL, and epistasis. Analysis of FLC from Don identified a new and more active allele likely caused by a cis-regulatory deletion covering the non-coding RNA COLDAIR. Further characterization of four FLC natural alleles showed different environmental and genetic interactions. Thus, FLC appears as a major modulator of the natural variation for the plasticity of flowering to multiple environmental factors.

Great Bustard (Otis tarda) nest locations in relation to leks

We investigated the spatial arrangement of Great Bustard Otis tarda nests relative to leks in 55 females captured at four lek sites and radio-tracked through 1–6xa0years in a protected area in central Spain. Although females showed a tendency to nest close to the lek centers where they were observed during the mating season (29% did it at <2xa0km), lek-to-nest distances ranged between 0.22 and 53.82 km. This resulted in most nest-sites (64%) being outside the lek areas where the female had mated, often closer to nearby leks, and sometimes far from any lek, in areas used only for nesting, outside the protected area (25%). The distribution of nest-to-nearest-lek distances did not differ from that of randomly distributed control sites, indicating that nest-sites were not aggregated, but dispersed over the whole suitable habitat within a large area around leks. Females with and without hatching success did not differ in their mean lek-to-nest distance. These results suggest that females used the whole suitable habitat available for nesting, and did not base nest-site selection on factors related to density-dependent disturbances or predation risks at leks (lek avoidance hypothesis). In this and other lekking birds, managers have often restricted conservation efforts to lek areas, under the wrong assumption that these would include most nest-sites. If a much larger region including most nesting habitat is not protected, Great Bustards in our study population might eventually be forced to nest at higher densities within the protected area, with a consequent density-dependent reduction in the mean breeding success of the population.ZusammenfassungFür 55 Großtrappen-Weibchen, die an 4 Balzplätzen gefangen und mittels kleiner Sender über 1–6 Jahre in einem Naturschutzgebiet in Zentralspanien verfolgt wurden, untersuchten wir die räumliche Verteilung der Nester in Beziehung zu den Balzplätzen. Zwar zeigten die Weibchen eine Tendenz, nahe desjenigen Balzplatzes zu nisten, an dem sie während der Balzzeit beobachtet worden waren (weniger als 2xa0km entfernt bei 29% der Tiere), aber die Entfernungen der Nester von den Balzplätzen reichten von 0,22 bis 53,82xa0km. 64% aller Nistplätze lagen außerhalb der Balzplatz-Areale, in denen die Weibchen begattet worden waren, manchmal näher zu anderen Balzplätzen und gelegentlich (in 25% der Fälle) weit entfernt von irgendwelchen Balzplätzen, außerhalb des Naturschutzgebietes, und nur zum Nisten ausgewählt. Die Verteilung der Entfernungen „Nest zum nächstgelegenen Balzplatz“ unterschied sich nicht signifikant von derjenigen der zufällig ausgesuchten Kontroll-Areale, was den Schluss nahe legt, dass die Nester nicht irgendwo gehäuft auftraten, sondern sich über das gesamte geeignete Habitat innerhalb eines weiten Gebietes um die Balzplätze herum verteilten. Auch zwischen Weibchen mit und ohne Bruterfolg konnte kein Unterschied in den Entfernungen ihrer Nester von den Balzplätzen festgestellt werden. Diese Ergebnisse lassen vermuten, dass die Weibchen bei der Wahl des Nistplatzes das gesamte, zum Nisten geeignete Habitat nutzten, ohne Berücksichtigung von Faktoren wie Nistplatzdichte oder spezielles Beute-Risiko (Balzplatz-Vermeidungs-Hypothese). Bei dieser und anderen Arten mit vergleichbarem Balzverhalten wurden Schutzmaßnahmen oft auf die Balzplätze begrenzt, in der irrigen Annahme, diese enthielten die meisten Nistplätze. Aber wenn nicht ein größeres Gebiet, inklusive der meisten Nistplätze, geschützt wird, könnten die Großtrappen der von uns untersuchten Population einmal gezwungen sein, innerhalb des geschützten Gebiets in größerer Dichte zu nisten, mit dem im Mittel durch die Dichte verursachten geringeren Bruterfolg der Population.

RISK-SENSITIVE FORAGING IN COAL TITS

Current theory of risk-sensitive foraging predicts that foragers should choose feeding sites on the basis of variation in as well as mean reward rate when there is a shortfall in their food supply or a decrease in their energy budget. For a given mean reward delay, they should choose high variance feeding sites if they are running below energy requirement, but low variance sites if they are running above. It has been suggested that the smaller the animal size, the stronger the preference reversion between high and low variable feeding sites. Previous tests of the energy budget rule when there was time variability have used bird species heavier than 80 g. Hence we tested energy budget rule predictions with coal tits Parus ater, a bird of 9 g of body mass, foraging at two feeding sites with high or low variability in food delivering delay. We manipulated energy budgets by controlling air temperature in the laboratory. In one treatment (positive budget), individuals were allowed to eat at the level of their own ad-libitum daily consumption and the air temperature was set to 24°C, while for the other treatment (negative budget), temperature was set to 14°C, and food availability was limited to the maximum daily intake observed in the positive budget treatment. When air temperature was low, daily intake increased but body mass decreased. Birds were also less active in the low temperature treatment, hopping less times every day. Latency to peck decreased as well, pecking for food when it was available sooner than in the high temperature treatment. These results show that coal tits were living in a negative energy budget when air temperature was set to 14°C. Preference for the variable feeding site was greatest in the negative energy budget, as it was predicted by the energy budget rule. Contrary to the energy budget rule, coal tits consistently preferred the variable option also in the positive energy budget. Possible explanations for these results are explored, including alternative foraging models to the energy budget rule.

Parental physiological condition and reproductive success in chinstrap penguins (Pygoscelis antarctica)

Recent studies suggest that parental resource allocation may be the most important factor explaining differences in reproductive output among parents. That said at least two different hypotheses of balance between parental foraging effort and resource allocation have been proposed. First, parents with high foraging effort have high reproductive success. Second, parents with higher allocation of resources to offspring have high reproductive success. We tested the second hypothesis using chinstrap penguins (Pygoscelis antarctica) as a model. We evaluated nutritional condition of the parents using blood urea, uric acid, creatine kinase, and cholesterol levels. We evaluated reproductive success according to total mass of the brood and asymmetries inside the brood. We measured the degree of asymmetry using weight and culmen length. Generalized linear models were used to examine relationships between adult plasma urea levels with year, nest position, and degree of asymmetry in chicks. Our results demonstrate that lighter broods were more asymmetric and associated with lower values of adult plasma urea, uric acid, and creatine kinase. We interpret these findings as evidence that the birds allocate fewer resources to their chicks than adults with more symmetric broods are.

Variable Shifts in the Autumn Migration Phenology of Soaring Birds in Southern Spain

While alteration of the migratory habits of birds is widely regarded as one of the most evident ecological effects of climate change, studies reporting shifts in migration phenology for long-lived, long-distance migrants have been few. Using time series of count data collected in southern Spain during autumn migration, we examined the magnitude and direction of phenological shifts for six common species of soaring birds. Many current methods for investigating phenological change rely on continuous data sets; however, these data may be unavailable for a variety of reasons. We used a cross-correlation analysis, which allowed us to compare recent data on the timing of migration from 1999–2011 to a historic data set collected during 1976–1977. The direction of phenological shifts for autumn migration was species-specific. White Storks Ciconia ciconia and Black Kites Milvus migrans appeared to have delayed passage, Black Storks Ciconia nigra and European Honey Buzzards Pernis apivorus have advanced their migratory timing, and we found no clear phenological change for Short-toed Eagles Circaetus gallicus or Booted Eagles Hieraaetus pennatus.