Correlated evolution of fig size and color supports the dispersal syndromes hypothesis

The influence of seed dispersers on the evolution of fruit traits remains controversial, largely because most studies have failed to account for phylogeny and or have focused on conservative taxonomic levels. Under the hypothesis that fruit traits have evolved in response to different sets of selective pressures by disparate types of seed dispersers (the dispersal syndromes hypothesis), we test for two dispersal syndromes, defined as groups of fruit traits that appear together more often than expected by chance. (1) Bird syndrome fruits are brightly colored and small, because birds have acute color vision, and commonly swallow fruits whole. (2) Mammal syndrome fruits are dull-colored and larger on average than bird syndrome fruits, because mammals do not rely heavily on visual cues for finding fruits, and can eat fruits piecemeal. If, instead, phylogenetic inertia determines the co-occurrence of fruit size and color, we will observe that specific combinations of size and color evolved in a small number of ancestral species. We performed a comparative analysis of fruit traits for 64 species of Ficus (Moraceae), based on a phylogeny we constructed using nuclear ribosomal DNA. Using a concentrated changes test and assuming fruit color is an independent variable, we found that small-sized fruits evolve on branches with red and purple figs, as predicted by the dispersal syndromes hypothesis. When using diameter as the independent variable, results vary with the combination of algorithms used, which is discussed in detail. A likelihood ratio test confirms the pattern found with the concentrated changes test using color as the independent variable. These results support the dispersal syndromes hypothesis.     

Cranial shape and correlated characters in crocodilian evolution

Crocodilians show a high degree of cranial variation and convergence throughout their 80 million-year fossil record that complicates their phylogenetic reconstruction. Conflicting phylogenetic results from different data partitions and character homoplasies typify crocodilian phylogeny, and differences between molecular and morphological phylogenetic hypotheses are believed to be associated with the slender-snout skull shape of Gavialis gangeticus and Tomistoma schlegelii. Slender-snout skulls are one of five identified eusuchian cranial ecomorph shape categories (ESCs) thought to reflect functional or ecological specialization. This paper tested the effect of transitions among general, blunt and slender ESCs on cranial character-state distributions in phylogeny using the concentrated changes test. In addition, 'tree-free' character compatibility analysis of character independence was conducted on the morphological character matrix to determine if character correlations are observed independent of specific tree topologies. Results suggest cranial ESCs do affect cranial character-state gains in phylogeny. Concentrated changes identify a broad suite of character-state changes that significantly correlate with transitions to slender, general and blunt ESCs on morphological, molecular and combined-data tree topologies, but numbers of correlated characters for each category differ according to topology. Character compatibility analysis results do not mirror the concentrated changes test results and reflect hierarchically distributed support throughout the data. As cranial ESCs affect character-state transitions, it is possible that nonphylogenetic variables could affect inferences of crocodilian phylogeny by affecting cranial morphology.     

Temporal patterns of microbial community structure in the Mid-Atlantic Bight

Although open ocean time-series sites have been areas of microbial research for years, relatively little is known about the population dynamics of bacterioplankton communities in the coastal ocean on kilometer spatial and seasonal temporal scales. To gain a better understanding of microbial community variability, monthly samples of bacterial biomass were collected in 1995-1996 along a 34-km transect near the Long-Term Ecosystem Observatory (LEO-15) off the New Jersey coast. Surface and bottom sampling was performed at seven stations along a transect line with depths ranging from 1 to 35 m (n=178). Microbial populations were fingerprinted using ribosomal 16S rRNA genes and terminal restriction fragment length polymorphism analysis. Results from cluster analysis revealed distinct temporal patterns among the bacterioplankton communities in the Mid-Atlantic Bight rather than grouping by sample location or depth. Principal components analysis models supported the temporal patterns. In addition, partial least squares regression modeling could not discern a significant correlation from traditional oceanographic physical and phytoplankton nutrient parameters on overall bacterial community variability patterns at LEO-15. These results suggest factors not traditionally measured during oceanographic studies are structuring coastal microbial communities.     

Seasonal activity of non-specific acid and alkaline phosphatases in beech (<Emphasis Type="Italic">Fagus sylvatica</Emphasis>) leaves

The activities of acid and alkaline phosphatases along with phosphorus content in leaves of European beech (Fagus sylvatica L.) were studied for a period from April to October. The phosphorus content of beech leaves was highest in April, at the beginning of the vegetation period; from May to October it was twofold lower than in April. Acid phosphatase activity (per unit fresh weight) in leaves collected from the middle part of the crown decreased significantly in May and July compared to the enzyme activity in April. In both the low and middle parts of the crown, the acid phosphatase activity had a peak in August, and thereafter decreased in September and October. No correlations between acid phosphatase activity and phosphorus concentrations were found. Alkaline phosphatase activity was very low and in some cases near the detection limit during the whole observation period.     

On humans and wildlife in Mediterranean islands

Aim To investigate the effects of human‐induced landscape changes in Mediterranean islands on the ecological and evolutionary responses of bird communities and populations. The combination of mass extinction of large mammals and massive deforestation by humans was hypothesized to produce new selection regimes to which organisms were likely to respond. Habitat selection and niche breadth have been investigated at the scale of species, and phenotypic variation at the scale of local populations. Location The study was carried out along habitat gradients and in habitat mosaics at different spatial scales on the island of Corsica and in areas of similar size and structure in continental France. Methods Two sets of gradients have been used for investigating habitat selection and niche breadth: gradients of altitude, and gradients of vegetation structure. Population studies focused on the blue tit, Cyanistes caeruleus. Large samples of breeding attempts by this species in 10 habitats provided detailed data on phenotypic variation of fitness‐related traits both on Corsica and on the mainland. Results The extent of niche space used by birds differed substantially depending on which habitat gradient was considered. Many species have been found to contract their habitat niche along the elevation gradient on Corsica compared with the mainland, whereas all species in the vegetation gradient broadened their niche on the island. Breeding patterns of the blue tit differed considerably depending on whether they settle in deciduous oaks (Quercus humilis) or in evergreen sclerophyllous oaks (Quercus ilex). Phenotypic variation of breeding traits was much higher on the island, where more populations were correctly timed for the best breeding period than on the mainland, a pattern that is likely to result from lower dispersal of organisms on the island. Main conclusions The differences in observed niche breadth between the two series of habitat gradients is explained both by the species‐specific ecology of the species and the human‐induced environmental history of Corsica. Large‐scale landscape changes provided new opportunities for island colonization by non‐forest species, which are isolated as small, ‘fugitive’ local populations. In both gradients, forest species that are typical components of the Corsican bird fauna definitely expanded their niche and occupied a wider range of habitats on Corsica than on the mainland. At the population scale, landscapes included habitat patches with contrasted selection regimes, which resulted in high phenotypic variation for many fitness‐related traits. Reduced dispersal of birds on the island resulted in a much higher degree of local differentiation on Corsica than on the mainland.     

Differential Contribution of L-, N-, and P/Q-type Calcium Channels to [Ca<Superscript>2+</Superscript>]<Subscript>i</Subscript> Changes Evoked by Kainate in Hippocampal Neurons

We investigated the contribution of L-, N- and P/Q-type Ca²⁺ channels to the [Ca²⁺]_i changes, evoked by kainate, in the cell bodies of hippocampal neurons, using a pharmacological approach and Ca²⁺ imaging. Selective Ca²⁺ channel blockers, namely nitrendipine, ω-Conotoxin GVIA (ω-GVIA) and ω-Agatoxin IVA (ω-AgaIVA) were used. The [Ca²⁺]_i changes evoked by kainate presented a high variability, and were abolished by NBQX, a AMPA/kainate receptor antagonist, but the N-methyl-d-aspartate (NMDA) receptor antagonist, D-AP5, was without effect. Each Ca²⁺ channel blocker caused differential inhibitory effects on [Ca²⁺]_i responses evoked by kainate. We grouped the neurons for each blocker in three subpopulations: (1) neurons with responses below 60% of the control; (2) neurons with responses between 60% and 90% of the control, and (3) neurons with responses above 90% of the control. The inhibition caused by nitrendipine was higher than the inhibition caused by ω-GVIA or ω-AgaIVA. Thus, in the presence of nitrendipine, the percentage of cells with responses below 60% of the control was 41%, whereas in the case of ω-GVIA or ω-AgaIVA the values were 9 or 17%, respectively. The results indicate that hippocampal neurons differ in what concerns their L-, N- and P/Q- type Ca²⁺ channels activated by stimulation of the AMPA/kainate receptors. Special issue article in honor of Dr. Ricardo Tapia.     

Growth characteristics of flagellated cells of Phaeocystis pouchetii revealed by diel changes in cellular DNA content

The present study reports on effects of different light:dark periods, light intensities, N:P ratios and temperature on the specific growth rate of flagellated cells of Phaeocystis pouchetii in culture. The specific growth rate was estimated by diel changes in cellular DNA content. The cellular DNA content and cell cycle of flagellated cells of P. pouchetii are shown, and the importance of light:dark period in cell division is demonstrated. Diel patterns of the cellular DNA content showed that cell division was confined to the dark period. The cells dealt with more than one division per day by rapid divisions shortly after each other.The specific growth rates (μ_DNA) based on the DNA cell cycle model were in close agreement with specific growth rates (μ_Cell) determined from cell counts. The temperature affected the specific growth rates (multiple regression, p < 0.01) and were higher at 5 °C (μ ≤ 2.2 d⁻¹) than at 10 °C (μ ≤1.6 d⁻¹). Increasing the light:dark period from 12:12 h to 20:4 h affected the specific growth rate of P. pouchetii at the lower temperature tested (5 °C) (multiple regression, p < 0.01), resulting in higher specific growth rates than at 10 °C. At 10 °C, the effect of light:dark period was severely reduced. Neither light nor nutrients could compensate the reduction in specific growth rates caused by elevated temperature. The specific growth rates was not affected by the N:P ratios tested (multiple regression, p = 0.21). The experiments strongly suggest that the flagellated cells have a great growth potential and could play a dominating role in northern areas at increased day length.     

Molecular-genetic systems of development: Functional dynamics and molecular evolution

This work for the first time compares results obtained with studies of parametric robustness of the Hh- and Dpp/BMP signal cascades responsible for morphogenesis and molecular evolution of the Hh- and Dpp/BMP cascade genes. There is a link between adaptive evolution of genes and those changes in kinetic parameters of the signal cascade models, which are critical for normal functioning of these cascades. Special attention is paid to events of the molecular evolution of the Hh- and Dpp/BMP cascade genes that matched with the emergence of the major taxonomic types and classes of Bilateria.     

不同穗型小麦品种旗叶光合作用日变化的研究

在大田条件下,对多穗型小麦品种豫麦49和大穗型小麦品种周麦13的旗叶净光合速率（Pn)及基影响因素,包括叶温（T1）、光合有效辐射（PAR）、蒸腾速率（Tr)、气孔导度（C）、细胞间隙CO2浓度（Ci)等日变化的测定结果表明,开花期2品种都存在光合“午休”现象,豫麦49Pn日变化呈双峰曲线,峰值出现在10：00和14：00,周麦13Pn日变化为单峰曲线,峰值在10：00。相关分析表明,开花期的温度和光照对豫麦49旗叶光合已造成一定程度的影响,此期的光温条件较有利于周麦13旗叶的光合作用。灌浆中期2品种均表现出一降不起型的严重“午休”现象,在强光、高温下,豫麦49旗叶Pn比周麦13降低明显。