Tool use and social homophily among male bottlenose dolphins.

Homophilous behaviour plays a central role in the formation of human friendships. Individuals form social ties with others that show similar phenotypic traits, independently of relatedness. Evidence of such homophily can be found in bottlenose dolphins ( Tursiops aduncus) in Shark Bay, Western Australia, where females that use marine sponges as foraging tools often associate with other females that use sponges. 'Sponging' is a socially learned, time-consuming behaviour, transmitted from mother to calf. Previous research illustrated a strong female bias in adopting this technique. The lower propensity for males to engage in sponging may be due to its incompatibility with adult male-specific behaviours, particularly the formation of multi-level alliances. However, the link between sponging and male behaviour has never been formally tested. Here, we show that male spongers associated significantly more often with other male spongers irrespective of their level of relatedness. Male spongers spent significantly more time foraging, and less time resting and travelling, than did male non-spongers. Interestingly, we found no difference in time spent socializing. Our study provides novel insights into the relationship between tool use and activity budgets of male dolphins, and indicates social homophily in the second-order alliance composition of tool-using bottlenose dolphins.

Population genomic signatures of divergent adaptation, gene flow and hybrid speciation in the rapid radiation of Lake Victoria cichlid fishes.

Adaptive radiations are an important source of biodiversity and are often characterized by many speciation events in very short succession. It has been proposed that the high speciation rates in these radiations may be fuelled by novel genetic combinations produced in episodes of hybridization among the young species. The role of such hybridization events in the evolutionary history of a group can be investigated by comparing the genealogical relationships inferred from different subsets of loci, but such studies have thus far often been hampered by shallow genetic divergences, especially in young adaptive radiations, and the lack of genome-scale molecular data. Here, we use a genome-wide sampling of SNPs identified within restriction site-associated DNA (RAD) tags to investigate the genomic consistency of patterns of shared ancestry and adaptive divergence among five sympatric cichlid species of two genera, Pundamilia and Mbipia, which form part of the massive adaptive radiation of cichlids in the East African Lake Victoria. Species pairs differ along several axes: male nuptial colouration, feeding ecology, depth distribution, as well as the morphological traits that distinguish the two genera and more subtle morphological differences. Using outlier scan approaches, we identify signals of divergent selection between all species pairs with a number of loci showing parallel patterns in replicated contrasts either between genera or between male colour types. We then create SNP subsets that we expect to be characterized to different extents by selection history and neutral processes and describe phylogenetic and population genetic patterns across these subsets. These analyses reveal very different evolutionary histories for different regions of the genome. To explain these results, we propose at least two intergeneric hybridization events (between Mbipia spp. and Pundamilia spp.) in the evolutionary history of these five species that would have lead to the evolution of novel trait combinations and new species.

Food production: technology and the resource base.

Despite a growing population and increasing demands of that population for improved diets, it appears that the world is not close to universal famine (3, 53). There is enough food now produced to feed the world's hungry (54). That people are malnourished or starving is a question of distribution, delivery, and economics, not agricultural limits. The problem is putting the food where the people are and providing an income so that they can buy it. As to the future, there are clouds on the far horizon. Only increased scientific and technological innovation, coupled with a change in human behavior and in national policy with regard to increased investments in agricultural research, can avert a growing food and population crisis. Only scientists develop new technology. Only farmers produce food. Motivation and incentives are important both for scientific discovery and food production. Agricultural research is also a process. There is no finite beginning or end. It is a continuing search to unravel mysteries. We must force the pace of agricultural development, but technology must be tailored to local conditions. Thiscan be done by scientists who also know how to farm. Individual dedication and sustained government commitments are important. Rapidity of information transfer and of acceptance of technology is also crucial (55). There is a wide gap between progress in research and the point of application for human benefit (Table 5). What accounts for the vast time differences in rapidity of technology acceptance? The current avalanche of new knowledge coupled with problems of food, feed, and fiber supplies, and issues of availability, preservation, protection, renewability, and costs of resources should bring to the front the urgency of rapid information transfer and reassessment of information systems for agricultural and other renewable resources.

Subcellular Localization of Zinc and Calcium in Bean (Phaseolus vulgaris L.) Tissues.

Two bean (Phaseolus vulgaris L.) cultivars differing in growth responses to zinc were examined for differences in uptake and subcellular localization of (65)Zn during a 15-day growth period. The zinc-sensitive cultivar Sanilac showed initially a much higher rate of absorption, which declined after 24 hours. The zinc-tolerant cultivar Saginaw showed a slow but steady rate of absorption for 10 days. In roots as well as in stem callus tissues of both cultivars, three-fourths of the absorbed (65)Zn was localized in the "cytoplasmic" supernatant fractions (containing ribosomes and vacuolar sap). Very little (less than 7%) (65)Zn was localized in the cell wall fraction. There was a much greater proportion of the absorbed (65)Zn localized in root mitochondria and nuclei of the zinc-sensitive Sanilac than in the zinc-tolerant Saginaw. Stem callus tissues, however, did not show such cultivar differences in zinc accumulation at the sub-cellular level.Calcium-45 distribution in the cultivar Redkote showed preferential affinity for cell walls both in roots and stem cellus tissue. The percentage of absorbed (45)Ca associated with cell wall fractions of roots gradually increased with a corresponding decline in the percentage of radioactivity associated with the cytoplasmic fraction. At 15 days, 57% of the total (45)Ca in the roots was localized in the cell walls. A similar, albeit less pronounced, preferential (45)Ca sorption on cell walls occurred for the callus tissue. Calcium-45 also accumulated at later stages in the nuclear fraction, but there was no mitochondrial accumulation.

Senescence inhibition and respiration induced by growth retardants and N-benzyladenine.

Senescence of Grand Rapids leaf lettuce was greatly reduced at 3 storage temperatures by post-harvest treatment with N,N-dimethylaminosuccinamic acid (Alar) and 2-chloroethyltrimethylammonium chloride (CCC), but not with (6)N-benzyladenine (BA). Conversely, Alar and CCC were inactive on broccoli while BA was markedly effective. The deterioration and discoloration of mushrooms was inhibited by Alar with no effect observed from BA or CCC.The inhibition of senescence by BA and the growth retardants was not always associated with a reduction in respiration (O(2) uptake, CO(2) evolution). BA stimulated respiration and hastened senescence in leaf lettuce accompanied by a diametrically opposite effect from Alar and CCC. Thus, BA cannot be considered a universal senescence inhibitor. The variability of senescence responses induced by different chemicals on a variety of plant tissues suggests a dissimilar mode of action or a complex interaction with native growth substances.

Growth of bean and tomato plants as affected by root absorbed growth substances and atmospheric carbon dioxide.

Bean and tomato plants were grown in solution culture root media containing pre-determined concentrations of gibberellin A3 (GA), 1-naphthaleneacetic acid (NAA), N(6)-benzyladenine (BA), (2-chloroethyl)trimethylammonium chloride (CCC), and at atmospheric levels of 300 and 1000 ppm of CO2. Net assimilation rates (NAR), relative growth rates (RGR), leaf area ratios (LAR), root to top dry weight ratios (R/T) and changes in dry weight, size, and form of each organ were recorded.Gibberellin had no effect on RGR of either plant species but increased the NAR of tomatoes at 1000 ppm CO2. Total dry weight was only slightly affected by GA but root growth and R/T were markedly depressed. CCC had no effect on NAR, but decreased RCR and LAR. Root growth of beans and R/T in both plants were promoted by CCC. NAR and RGR were strongly inhibited by BA and NAA. Inhibition of stem and leaf growth by CCC and NAA was greater than that for roots; thus, R/T ratios were increased. Root branching was promoted by NAA.High (1000 ppm), compared to the low (300 ppm), atmospheric levels of CO2 generally promoted root growth and produced an increase in the R/T, both in the absence and presence of chemical treatment. The multiplicity of effects of the rootabsorbed chemical growth substances and CO2 on growth and photosynthesis is discussed.