Photosynthesis in leaves of the juvenile and adult phase of ivy (Hedera helix)

Abstract Photosynthetic and anatomical parameters of leaves from the juvenile and adult part of an ivy plant (Hedera helix L.) have been determined and compared with each other. Light-saturated net photosynthesis (per unit leaf area) was about 1.5 times higher in adult leaves than in juvenile ones. The lower photosynthetic capacity of juvenile leaves was caused by a lower stomatal and especially a lower residual conductance to the CO₂-transfer. This corresponds with anatomical features of the leaves, i.e. lower stomatal frequency, fewer chloroplasts per cell, and – most important – thinner leaves, as well as with a less efficient photosynthetic apparatus measured as Hill reaction of isolated broken chloroplasts and activity of ribulose bisphosphate carboxylase. No differences in the respiration in light (relative to net photosynthesis) and in the CO₂-compensation concentration could be detected between the two leaf types. These observed anatomical and photosynthetic parameters of the juvenile and adult ivy leaves resemble those reported for shade and sun leaves, respectively, although the leaves investigated originated from the same light environment.     

Demonstration of a voltage dependent calcium current in follicles of the cockroach Nauphoeta cinerea

Summary

The electrical properties of vitellogenic cockroach follicles have been studied using a two-electrode voltage-clamp technique. The resting potential of freshly isolated follicles was usually between ?30 mV and ?45 mV. A voltage-dependent inward current could be activated when the follicles were placed in a medium containing high concentrations of either Ca²⁺ or Ba²⁺. Maximal current amplitudes were 0.8μA in a medium containing 30 mM Ca²⁺ and 2 μA in 30 mM Ba²⁺. Maximal amplitudes could be elicited with depolarizing pulses to about +15 mV. The steady-state inactivation curve indicated half maximal current at a holding potential of about ?20 mV. Co²⁺, Ni²⁺ and Mn²⁺ inhibited the divalent cation currents in a concentration dependent manner. Half maximal inhibition was observed at about 3 mM concentration for each of the inhibitory cations.     

Warming leads to higher species turnover in a coastal ecosystem

The responses of ecological communities and ecosystems to increased rates of environmental change will be strongly influenced by variation in the diversity of community composition. Yet, our understanding of how diversity is affected by rising temperatures is inconclusive and mainly based on indirect evidence or short‐term experiments. In our study, we analyse the diversity and species turnover of benthic epilithic communities within the thermal flume of a nuclear power plant at the Swedish coast. This flume covers the range of predicted future temperature rises. Species composition was significantly different between control sites and sites with higher temperatures. We found that temperature had little effect on the number of species in three functional groups (macroinvertebrates, benthic diatoms, and macrophytes, which here comprise multicellular algae and macroscopic colonies of unicellular algae and cyanobacteria), neither at single sampling dates nor summed for the entire observation year. However, species turnover significantly increased with increasing temperature for diatoms, macrophytes and invertebrates. Different temperature regimes resulted in significantly different species composition and indicator species. Thus, increasing temperatures in the thermal flume increased temporal beta‐diversity and decreased compositional stability of communities, although observed richness did not change at any point in time. We highlight the need to investigate the consequences of such declines in compositional stability for functional stability of ecosystem processes.     

Rediscovery of Paramecium nephridiatum Gelei, 1925 and its Characteristics

Paramecium nephridiatum Gelei. 1925, was rediscovered. It is a euryhaline brackish-water species that morphologically resembles Paramecium woodruffi . but with multiple contractile vacuole pores. The general morphology, morphometry. and random amplified polymorphic DNA (RAPD) fingerprint patterns are presented for a number of the stocks collected around the world.     

Phylogeny and biogeography of Zelkova (Ulmaceae sensu stricto) as inferred from leaf morphology, ITS sequence data and the fossil record

To address the evolution and geographical diversification of the genus Zelkova (Ulmaceae) a phylogenetic analysis of morphological data and the sequences of the internal transcribed spacers (ITS1 and ITS2) of nuclear ribosomal DNA were used. Cladistic analyses suggested that the Chinese species Z. schneideriana and Z. sinica are basal within Zelkova. The western Asian Z. carpinifolia either appears nested between the East Asian Z. schneideriana and Z. sinica and a clade formed by the Japanese Z. serrata and two Mediterranean species, Z. abelicea and Z. sicula (ITS), or forms a clade with Z. serrata that is sister to a clade Z. abelicea plus Z. sicula (morphology). Nucleotide data suggested that gene flow occurred between Z. schneideriana and Z. serrata, and Z. carpinifolia and a lineage ancestral to Z. abelicea/sicula. Character evolution in Zelkova appears to have gone from long leaves with numerous secondary veins, coarse to shallow teeth with blunt or slightly pointed apex and small stomata, to leaves that are either long or short with numerous or few secondary veins, coarse teeth with cuspidate or obtuse apex or conspicuously shallow teeth, and dimorphic stomata displaying ‘giant stomata’ surrounded by a ring of small stomata or uniform large stomata. These results are in agreement with fossil data. Early Cainozoic fossils attributed to Zelkova from North America and Central Asia closely resemble the modern Z. schneideriana and Z. carpinifolia. The genus could have originated in the northern Pacific area and migrated to Europe after the Turgai Strait was closed during the Late Oligocene. Geographical differentiation may have started with the isolation of Chinese populations (leading to modern Z. schneideriana and Z. sinica) from high‐latitude Eurasian (North American) populations. This widespread Early Cainozoic type may have diversified into the western Asian Z. carpinifolia and the more derived Japanese and Mediterranean species during the latest Cainozoic. The modern Japanese and European/western Asian species would have differentiated relatively late, while two locally endemic Mediterranean species are the result of the cooling and development of a Mediterranean climate belt in Europe during the Pleistocene. Fossils from the Miocene and Pliocene of Europe resemble modern Z. carpinifolia and Z. serrata. Differentiation of the two Mediterranean species Z. abelicea and Z. sicula in the Late Cainozoic cannot be traced by leaf morphology. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 147 , 129–157.     

Changes in the Organic Acid Content of some Cultivated Plants Induced by Mineral Ion Deficiency

Four plant species (Zea mays, Lolium italicum, Phaseolus vulgaris,and Pisum sativum) were grown either with full nutrient supplyor with calcium, potassium, or nitrogen deficiency. After 4–6weeks the shoots were analysed for their content of K⁺, Ca²⁺,Mg²⁺, and Na⁺, of total anions, and of organic acids. The qualitativepattern of organic acid components, characteristic of each species,remained, with few exceptions, unchanged by deficiency treatments.Striking differences were detected in the total acid contentand in the quantities of the respective main organic acid components,especially in potassium-deficient plants. These changes showedstrong correlations with alterations of cation excess and demonstratethat aconitate in Zea mays, malonate in Phaseolus vulgaris,and citrate in Pisum sativum contribute to charge balance.     

THE EVOLUTION OF REVERSED SEXUAL DIMORPHISM IN SIZE IN MONOGAMOUS SPECIES OF BIRDS

Reversed sexual dimorphism in size (RSD) occurs in most species of several taxonomic groups of birds. The hypotheses proposed to explain this phenomenon are examined theoretically, using inequalities to state selection in the most rigorous possible terms. The most pertinent empirical evidence is also examined critically. Proponents of hypotheses on the evolution of RSD have failed to consider the genetic constraints on the evolution of dimorphism. Selection for dimorphism can act on only that small portion of the genetic determination of body size that is sex limited. In general, selection for body size is much more likely to lead to a similar change (e.g. larger) in both sexes than to dimorphism. The most popular hypotheses involve selection for size-related differences in foraging ability. It is unlikely that there is variation in size-related foraging differences available for selection in a monomorphic, ancestral population. Foraging differences between the sexes cannot lead to the evolution of RSD; evolution of large and small morphs of both sexes is a more likely outcome. Selection for sex-role differentiation factors (e.g. large females lay larger eggs, small males are more agile in flight) can lead to the evolution of RSD, but only if the magnitudes of opposing selection for small males and for large females are equal. Combining selection for size-related foraging differences with selection for sex-role differentiation factors hinders the evolution of RSD until the sexes differ in size by 3 s.d . Empirical evidence supports this assertion: statistically significant differences between the sexes in the size of prey taken are found only in highly dimorphic species. The sex-role differentiation factors that have been proposed appear unlikely to provide the equal selection necessary for the evolution of RSD. Several authors have proposed that small size in males is selected for foraging ability and large size in females for some sex-role differentiation factor. Males cannot be more efficient foragers without females being less efficient and efficiency cannot be a factor only when the male is feeding his family. RSD cannot evolve in monogamous species if large females survive less well than small males. RSD might evolve as the result of sexual selection for small size in males and constraints on the reduction of size in females because of some factor associated with reproduction. Examination of seven studies indicating a relationship between female size and reproductive success shows very little unequivocal evidence for small size in females allowing breeding earlier in the season. Large size in females allows females to breed at a younger age in the sparrowhawk and pairs to form more rapidly in three species of sandpipers. Both of these may be the result of sexual selection. There are fewer theoretical problems with sexual selection as a cause for the evolution of RSD than with the other hypotheses. Empirical evidence for sexual selection is scarce but better than that for the other hypotheses. Evidence is contradictory for the selection of small size in males for agility in aerial displays for courtship or defence of territory. Large size in females does not appear to be the result of selection for competitive ability to obtain mates. Facilitation of female dominance and hence of the formation and maintenance of a pair bond is the most viable explanation of the evolution of RSD. It is most likely that all dimorphism (normal or reversed) is the result of sexual selection. RSD is correlated with birds in the diet in the Falconiformes and this is a central theme in the foraging hypotheses. This correlation may be because birds are abundant and available in a continuum of sizes, thus permitting but not causing the evolution of RSD or because species that prey upon birds are better equipped physically (and perhaps more likely behaviourally) to inflict damaging attacks on conspecifics and the greater RSD increases female dominance and the ease of pair formation.     

Dispersal of the thistle gallfly Urophora cardui and its endoparasitoid Eurytoma serraiulae (Hymenoptera: Eurytomidae)

Abstract. 1. The dispersal of the gall-forming tephritid Urophora cardui L. (Diptera: Tephritidae) and its endoparasitoid Eurytoma serratulae Latr. (Hymenoptera: Eurytomidae) from an experimental colony were investigated over a period of 4 years.
2. The dispersal rate for both fly and endoparasitoid was one to two magnitudes higher than in previous studies, which found 100 m per generation maximally. The dispersal rate of the endoparasitoid was not less than that of its host. Most newly founded colonies were small and had high extinction rates.
3. The viability of colonies of U. cardui did not correlate with the distance from the dispersal centre.
4. The dispersal rates observed are high enough to allow a multiple spread and extinction in mid-Europe in the post-pleistocene period.     

A paradox survival – report of a repaired syn vivo perforation in a nautiloid phragmocone

The nautiloid Trocholites depressus (Eichwald, 1840) from the Lasnamägi regional stage (Darrivillian, Middle Ordovician) of Vaike Pakri Island (North-West Estonia) is the only known ectocochleate cephalopod that survived and healed a perforation of the phragmocone. Two chambers of the specimen were broken during its lifetime. The injury is located on the venter of the conch directly above the peristomal opening of the body chamber. It is reconstructed that the peristomal mantle tissue carried out an initial sealing of the injured chambers. The complete calcified sealing and compensation of the irregular shell surface started late with the overgrowth of the septa of the preceding whorl. The position and diameter of the siphuncle were not disturbed by the regeneration showing that these characters allowed a low phenotypic variability. Despite the trauma in the midlife growth history of this specimen, it appears to have reached maturity.