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Cobreeding in the Burying Beetle, Nicrophorus vespilloides: Tolerance Rather Than Cooperation
No full textUnder intra- and interspecific competition, cooperative behaviour can provide direct fitness benefits if individuals work together to expel intruders. In the burying beetle Nicrophorus vespilloides, a relatively small species, multiple unrelated pairs can breed together, and individuals are weak competitors in interactions when competing with larger individuals of the same species and with larger species of the same genus. In field and laboratory studies, we found that two pairs together attracted significantly fewer congeneric and non-congeneric competitors compared with single pairs. No other benefits were found. Communal breeding had large negative effects on fitness, as there were fewer offspring per pair and a higher chance of injuries. The higher chance of injuries reflected pairs fighting among themselves and not against competitors. These costs are much greater than the small benefit of fewer intruders. Why should a N. vespilloides breeding pair eventually allow another pair to join? A potential partial explanation is that these are not cooperative pairs in the traditional sense, but rather pairs have a higher tolerance for each other. From the resident's perspective, joining pairs are not expelled because the chance of injury makes the cost of fighting high. Joining others may have unusually low costs in this species because reproductive opportunities are rare, dependent on a resource that is unpredictable in time and space, and residents should be inclined to tolerating new pairs because of the cost of fighting. Thus, for N. vespilloides, communal breeding appears to be ‘making the best of a bad job’, providing some reproduction rather than none.
Ocean acidification reduces growth and calcification in a marine dinoflagellate
No full textOcean acidification is considered a major threat to marine ecosystems and may particularly affect calcifying organisms such as corals, foraminifera and coccolithophores. Here we investigate the impact of elevated pCO2 and lowered pH on growth and calcification in the common calcareous dinoflagellate Thoracosphaera heimii. We observe a substantial reduction in growth rate, calcification and cyst stability of T. heimii under elevated pCO2. Furthermore, transcriptomic analyses reveal CO2 sensitive regulation of many genes, particularly those being associated to inorganic carbon acquisition and calcification. Stable carbon isotope fractionation for organic carbon production increased with increasing pCO2 whereas it decreased for calcification, which suggests interdependence between both processes. We also found a strong effect of pCO2 on the stable oxygen isotopic composition of calcite, in line with earlier observations concerning another T. heimii strain. The observed changes in stable oxygen and carbon isotope composition of T. heimii cysts may provide an ideal tool for reconstructing past seawater carbonate chemistry, and ultimately past pCO2. Although the function of calcification in T. heimii remains unresolved, this trait likely plays an important role in the ecological and evolutionary success of this species. Acting on calcification as well as growth, ocean acidification may therefore impose a great threat for T. heimii.
Life expectancy of artists in the Low Countries from the fifteenth to the twentieth century
No full textWe investigated the role that urbanization and plague may have played in changes in life expectancy
amongst artists in the Low Countries who were born between 1450 and 1909. Artists can be considered to be representative of a middle-class population living mostly in urban areas. The dataset was constructed using biographical information collected by the Rijksbureau voor Kunsthistorische Documentatie in The Hague, the Netherlands. As early as the beginning of the sixteenth century, life expectancy at age 20 amongst the artists had reached 40 years. After a substantial decline in the late sixteenth and the early seventeenth centuries, when plague hit the region, life expectancy at age 20 began to rise again, and this upward trend accelerated after 1850. The life expectancy of female artists commonly exceeded that of males, and sculptors had better survival prospects than painters. In comparison with elite groups in the Low Countries and elsewhere in Europe, life expectancy amongst the artists was rather high.
keywords: Low Countries; Netherlands; Belgium; Golden Age; historical demography; life expectancy;
survival of middle classes; Gompertz curve; art history; painters and sculptors
Genetic consequences of breaking migratory traditions in barnacle geese
No full textCultural transmission of migratory traditions enables species to deal with their environment based on experiences from earlier generations. Also, it allows a more adequate and rapid response to rapidly changing environments. When individuals break with their migratory traditions, new population structures can emerge that may affect gene flow. Recently, the migratory traditions of the Barnacle Goose Branta leucopsis changed, and new populations differing in migratory distance emerged. Here, we investigate the population genetic structure of the Barnacle Goose to evaluate the consequences of altered migratory traditions. We used a set of 358 single nucleotide polymorphism (SNP) markers to genotype 418 individuals from breeding populations in Greenland, Spitsbergen, Russia, Sweden and the Netherlands, the latter two being newly emerged populations. We used discriminant analysis of principal components, FST, linkage disequilibrium and a comparison of geneflow models using migrate-n to show that there is significant population structure, but that relatively many pairs of SNPs are in linkage disequilibrium, suggesting recent admixture between these populations. Despite the assumed traditions of migration within populations, we also show that genetic exchange occurs between all populations. The newly established nonmigratory population in the Netherlands is characterized by high emigration into other populations, which suggests more exploratory behaviour, possibly as a result of shortened parental care. These results suggest that migratory traditions in populations are subject to change in geese and that such changes have population genetic consequences. We argue that the emergence of nonmigration probably resulted from developmental plasticity.
Nutrient pulse induces dynamic changes in cellular C:N:P, amino acids, and paralytic shellfish poisoning toxins in Alexandrium tamarense
No full textAlexandrium tamarense is a common harmful algal bloom species and can cause high concentrations of paralytic shellfish poisoning toxins (PSTs) in marine coastal waters. PSTs are nitrogen rich alkaloids and their production has been shown to depend on resource conditions as well as on growth rate. We hypothesized that PST content in A. tamarense depends on the nitrogen availability and will increase with cellular N:P ratios and arginine content. To test this hypothesis, we first grew A. tamarense cells under nitrogen starved, phosphorus starved and nutrient replete conditions. Subsequently, we transferred cells into nutrient rich medium and followed dynamic changes in growth, elemental stoichiometry, as well as the amino acid and PST content and composition. Our results illustrate that PST content was lowest under nitrogen starvation, intermediate under nutrient replete conditions, and highest under phosphorus starvation. As expected, PST content correlated well with cellular N:P ratios and arginine content. Upon transfer of cells into nutrient replete medium, PST content varied with growth rate, depending on the growth controlling resource. Specifically, PST content increased with growth when recovering from nitrogen starvation and decreased with growth when recovering from phosphorus starvation. Furthermore, PST composition shifted towards less hydroxylated analogues upon resumption of growth. Our findings also illustrate a high potential for luxury consumption of phosphorus by A. tamarense. The applied comprehensive approach will help to further elucidate the intriguing coupling between carbon, nitrogen and phosphorus assimilation and the synthesis of amino acids and PSTs.
