Prox 1 in eye degeneration and sensory organ compensation during development and evolution of the cavefish Astyanax

We have investigated expression of the homeobox gene Prox 1 during eye degeneration and sensory organ compensation in cavefish embryos. The teleost Astyanax mexicanus consists of sighted surface-dwelling forms (surface fish) and several populations of blind cave-dwelling forms (cavefish), which have evolved independently. Eye formation is initiated during cavefish development, but the lens vesicle undergoes apoptosis, and the eye subsequently arrests and degenerates. The requirement of Prox 1 for lens fiber differentiation and γ-crystallin expression in the mouse suggests that changes in the expression of this gene could be involved in cavefish eye degeneration. Surface fish and cavefish embryos stained with a Prox 1 antibody showed Prox 1 expression in the lens, neuroretina, myotomes, heart, hindbrain, and gut, as reported in other vertebrates. We found that Prox 1 expression is not altered during cavefish lens development. Prox 1 protein was detected in the lens vesicle as soon as it formed and persisted until the time of lens degeneration in each cavefish population. The cavefish lens vesicle was also shown to express a γ-crystallin gene, suggesting that Prox 1 is functional in cavefish lens development. In addition to the tissues described above, Prox 1 is expressed in developing taste buds and neuromasts in cavefish, which are enhanced to compensate for blindness. It is concluded that the Prox 1 gene is not involved in lens degeneration, but that expansion of the Prox 1 expression domain occurs during taste bud and neuromast development in cavefish. Received: 31 July 1999 / Accepted: 8 November 1999     

Questioning the relevance of shifting cultivation to Neolithic farming in the loess belt of Europe: evidence from the Hambach Forest experiment

Despite widespread criticism, the shifting cultivation model continues to inform discussion of Neolithic farming in Europe, beginning with early Neolithic (Linearbandkeramik or LBK) communities concentrated in the loess belt of western-central Europe. Hundreds of LBK and later Neolithic sites have been excavated in this region and many of them sampled for charred plant remains. Archaeobotanical data on the weed floras harvested with crops provide the most direct archaeological evidence of crop husbandry practices, including the permanence of crop fields, but have played a limited role in the debate over shifting cultivation. The Hambach Forest experiment, conducted in the 1970s-80s near Cologne, Germany, provides valuable comparative data on the weed floras growing in newly cleared cultivation plots in an area of longlived mixed oak woodland on loess-based soil. Correspondence analysis of the Hambach weed survey data suggests that weed floras of fields managed under a shifting cultivation regime would be rich in perennial species, including woodland perennials. Comparison of these results with Neolithic weed assemblages from the loess belt of western-central Europe strongly suggests that Neolithic crop fields were not recently cleared of woodland vegetation but were long-established. Received September 5, 2001 / Accepted February 26, 2002     

Effects of below-ground insects, mycorrhizal fungi and soil fertility on the establishment of Vicia in grassland communities

 The effects of, and interactions between, insect root feeders, vesicular-arbuscular mycorrhizal fungi and soil fertility on the establishment, growth and reproduction of Vicia sativa and V. hirsuta (Fabaceae) were investigated in an early-successional grassland community. Seeds of both species were sown into plots where soil insecticide (Dursban 5G), soil fungicide (Rovral) and soil fertiliser (NPK) were applied in a factorial randomised block design. Fertiliser addition reduced growth, longevity and reproduction of both Vicia species, due to the commonly recorded increase in the competitive advantage of the non-nitrogen-fixing species when nitrogen is added to the plant community. However, in plots where fertiliser was not applied, a reduction in root feeders and mycorrhizal infection led to an increase in seedling establishment and fruit production of V. sativa, and to an increase in flower production for both Vicia species. The interaction between all three soil treatments explained much of the variation in growth and longevity of V. sativa. Plants grew larger and survived longer in plots where natural levels of mycorrhizal infection and root feeders were low compared with plots where all the treatments were applied. This suggests that, although soil nutrient availability was a strong determinant of the performance of these two leguminous species, at natural levels of soil fertility biotic factors acting in the soil, such as mycorrhizal fungi and soil-dwelling insects, were important in shaping the competitive interactions between the two Vicia species and the plant community. Our results indicate that non-additive interactions between ecological factors in the soil environment may strongly affect plant performance. Received: 18 July 1995 / Accepted: 14 August 1996     

Early stages of root and leaf decomposition in Hawaiian forests: effects of nutrient availability

We examined the effects of soil nutrient availability and tissue chemistry on decomposition of both fine roots (<2 mm diameter) and leaves in three sites along a forest chronosequence in the Hawaiian Islands. These sites form a natural fertility gradient, with the youngest and oldest sites having lower nutrient availability than the intermediate-aged site. Nitrogen (N) limits aboveground net primary productivity (ANPP) in the youngest site, while phosphorus (P) limits ANPP in the oldest site. Both root and leaf litter decomposed most slowly in the 4.1-Myear-old site. We also investigated root decomposition in fertilized plots at the youngest and oldest sites; when roots were produced and decomposed in fertilized plots, root decomposition rates increased with N and P additions at the 4.1-Myear-old site. At the 300-year-old site, however, root decomposition rates did not respond to N or P additions. Roots decomposed faster than leaves at the more infertile sites, in part because of lower lignin-to-nitrogen ratios in roots than in leaf litter. Decomposing roots immobilized more nutrients than did decomposing leaves, and may serve an important role in retaining nutrients in these forests. Received: 30 November 1998 / Accepted: 12 August 1999     

Genetic variation and productivity of Populus trichocarpa and its hybrids. X. Trait correlations in young black cottonwood from four river valleys in Washington

 A common-garden study of Populus trichocarpa Torr. & Gray was established in spring 1986 with 128 clones collected from sites along two mesic (Hoh and Nisqually) and two xeric (Dungeness and Yakima) river valleys in Washington. Two replicate plantations, one in Puyallup and the other in Wenatchee, Wash., were established with this material. Over 2 years data were taken on stem growth, leaf/crown characters, spring/autumn phenology, and the incidence of Melampsora occidentalis leaf rust. Combining clones from all four sources, correlation/regression analyses were used to examine clonal stability of traits between test sites and trait relationships with stem growth; broad-sense heritabilities (H ²) and genetic correlations revealed the genetic strength of these traits. At Puyallup, many leaf/crown traits predicted stem growth moderately to very well (r ²>0.50), e.g., total leaf area (TLA) to diameter gave an r ² of 0.91 and current-terminal leaf size, of 0.79. Some regressions were quadratic, suggesting a threshold level in a trait (e.g., leaf size) beyond which stem growth levels off. Upper-crown TLA was more closely related to height than TLA of the lower sylleptics, but the reverse was true for diameter. A decline in r ² values from upper to lower crown positions was sharper for correlations of TLAs with height than with diameter. Thus, leaf area allocation seems to differentially affect stem growth. When autumn leaf fall (LF) and rust incidence (R) were regressed with growth, r ² values ranged from 0.58 to 0.71, but those of spring flush (SF) were only 0.10 to 0.12. Early LF and high R, both negatively affecting growth, had a strong geographic component as it occurred mainly on lower-elevation Yakima clones. At Wenatchee, field conditions were harsher and microsites more variable, so trait/growth relationships were weaker. Genetic correlations with growth revealed similar trends as phenotypic analyses. Unlike leaf/crown traits, clonal scores of LF, SF, and R were fairly stable across the two test sites (r ²: 0.58–0.80). These traits also showed strong genetic control (H ²: 0.96–0.98). The trait/growth relationships as well as trait stability within clones have implications for selecting clonal stock in poplar culture and conservation. Received: 23 February 1998 / Accepted: 7 May 1998     

The generic placement of a morphologically enigmatic species in Asteraceae: evidence from ITS sequences

 Bidens cordylocarpa is a high polyploid species restricted in distribution to stream sides in the mountains of Jalisco, Mexico. The morphologically enigmatic species was originally described as a member of the genus Coreopsis, but later transferred to Bidens, largely because the involucral bracts appear most similar to Bidens. Characters of the cypselae, often useful in generic placement, are of no value for this species because the fruits have features not detected in either Bidens or Coreopsis. Sequences from the internal transcribed spacer region of nuclear ribosomal DNA (ITS) were used to assess the relationships of Bidens cordylocarpa. The molecular phylogeny places B. cordylocarpa in a strongly supported clade of Mexican and South American Bidens, and provides more definitive evidence of relationships than morphology, chromosome number, or secondary chemistry. Molecular, morphological, and chromosomal data suggest that B. cordylocarpa is an ancient polyploid, perhaps the remnant of a polyploid complex. Received August 28, 2000 Accepted February 11, 2001     

The importance of phenology for the evaluation of impact of climate change on growth of boreal, temperate and Mediterranean forests ecosystems: an overview

An overview is presented of the phenological models relevant for boreal coniferous, temperate-zone deciduous and Mediterranean coniferous forest ecosystems. The phenology of the boreal forests is mainly driven by temperature, affecting the timing of the start of the growing season and thereby its duration, and the level of frost hardiness and thereby the reduction of foliage area and photosynthetic capacity by severe frost events. The phenology of temperate-zone forests is also mainly driven by temperature. Since temperate-zone forests are mostly mixed-species deciduous forests, differences in phenological response may affect competition between tree species. The phenology of Mediterranean coniferous forests is mainly driven by water availability, affecting the development of leaf area, rather than the timing of phenological events. These phenological models were subsequently coupled to the process-based forest model FORGRO to evaluate the effect of different climate change scenarios on growth. The results indicate that the phenology of each of the forest types significantly affects the growth response to a given climate change scenario. The absolute responses presented in this study should, however, be used with caution as there are still uncertainties in the phenological models, the growth models, the parameter values obtained and the climate change scenarios used. Future research should attempt to reduce these uncertainties. It is recommended that phenological models that describe the mechanisms by which seasonality in climatic drivers affects the phenological aspects of trees should be developed and carefully tested. Only by using such models may we make an assessment of the impact of climate change on the functioning and productivity of different forest ecosystems. Received: 21 October 1999 / Revised: 10 May 2000 / Accepted: 10 May 2000     

Sectional relationships in the genus Rhododendron (Ericaceae): evidence from matK and trnK intron sequences

 Phylogenetic relationships among all eight subgenera and 12 sections in Rhododendron as well as its related genera were inferred from matK and trnK intron sequences. The results of this study provided the following insights: (1) Rhododendron is paraphyletic because Menziesia is nested within Rhododendron. (2) Subgenus Therorhodion forms a basal lineage of tribe Rhodoreae. (3) Subgenera Hymenanthes and Tsutsusi are monophyletic. (4) Subgenera Azaleastrum and Pentanthera are polyphyletic. (5) Subgenus Rhododendron is monophyletic, if section Rhododendron subsection Ledum is excluded. Received January 8, 1999, in definite form December 22, 2000 Accepted April 12, 2001     

Replenishment of fish populations in the enclosed lagoon of Taiaro Atoll: (Tuamotu Archipelago, French Polynesia) evidence from eggs and larvae

 Taiaro Atoll Lagoon is normally isolated from the ocean, but at least 125 marine fish species of 31 families are present there. We sampled fish larvae in Taiaro Lagoon and the nearby ocean in February 1994 with plankton net, neuston net and light trap to investigate which taxa were completing their life cycles in the lagoon. Concentrations of fish eggs and larvae were very high in the lagoon indicating intense spawning, but larvae of only 18 taxa of 10 families were present. Only six, a callionymid, gobiids, a hemiramphid, a microdesmid, and two pomacentrids, were present across a full range of pelagic sizes, and were clearly completing their pelagic stage in the lagoon. Four other taxa, an apogonid, two labrids and a scarid, were common, but the largest individuals were small (<5 mm) postflexion larvae. These may have been completing their pelagic stage in the lagoon. The remaining lagoonal larvae (eight taxa) were rare and at the preflexion stage, so we could only conclude that they hatched from eggs spawned in the lagoon. Nineteen taxa of 15 families found as adults in the lagoon were present outside the lagoon as larvae, but not inside, suggesting that they may not normally complete their life cycles in the lagoon. Horizontal distributions of larvae in the lagoon are apparently due to the interaction of larval vertical distribution behaviour with a wind-driven countercurrent system. Accepted: 16 October 1996     

No correlation between the diversity and productivity of assemblages: evidence from the phytophage and predator assemblages in various cotton agroecosystems

Biodiversity research has shown that primary productivity increases with plant species number, especially in many experimental grassland systems. Here, we assessed the correlation between productivity and diversity of phytophages and natural enemy assemblages associated with planting date and intercropping in four cotton agroecosystems. Twenty-one pairs of data were used to determine Pearson correlations between species richness, total number of individuals, diversity indices and productivity for each assemblage every five days from 5 June to 15 September 2012. At the same trophic level, the productivity exhibited a significant positive correlation with species richness of the phytophage or predator assemblage. A significant correlation was found between productivity and total number of individuals in most cotton fields. However, no significant correlations were observed between productivity and diversity indices (including indices of energy flow diversity and numerical diversity) in most cotton fields for either the phytophage or the predator assemblages. Species richness of phytophage assemblage and total individual numbers were significantly correlated with primary productivity. Also, species richness of natural enemy assemblage and total number of individuals correlated with phytophage assemblage productivity. A negative but not significant correlation occurred between the indices of numerical diversity and energy flow diversity and lower trophic-level productivity in the cotton-phytophage and phytophage-predator assemblages for most intercropped cotton agroecosystems. Our results clearly showed that there were no correlations between diversity indices and productivity within the same or lower trophic levels within the phytophage and predator assemblages in cotton agroecosystems, and inter-cropped cotton fields had a stronger ability to support the natural enemy assemblage and potentially to reduce phytophages.     

Spatial productivity variations during formation of sapropels S5 and S6 in the Mediterranean Sea: evidence from Ba contents

We investigated five time-equivalent core sections (180-110 kyr BP) from the Balearic Sea (Menorca Rise), the easternmost Levantine Basin and southwest, south, and southeast of Crete to reconstruct spatial patterns of productivity during deposition of sapropels S5 and S6 in the Mediterranean Sea. Our indicators are Ba, total organic carbon and carbonate contents. We found no indications of Ba remobilization within the investigated core intervals, and used the accumulation rate of biogenic Ba to compute paleoproductivity. Maximum surface water productivity (up to 350 g C/m²/yr) was found during deposition of S5 (isotope stage 5e) but pronounced spatial variability is evident. Coeval sediment intervals in the Balearic Sea show very little productivity change, suggesting that chemical and biological environments in the eastern and western Mediterranean basins were decoupled in this interval. We interpret the spatial variability as the result of two different modes of nutrient delivery to the photic zone: river-derived nutrient input and shoaling of the pycnocline/nutricline to the photic zone. The productivity increase during the formation of S6 was moderate compared to S5 and had a less marked spatial variability within the study area of the eastern Mediterranean Sea. Given that S6 formed during a glacial interval, glacial boundary conditions such as high wind stress and/or cooler surface water temperatures apparently favored lateral and vertical mixing and prevented the development of the spatial gradients within the Eastern Mediterranean Sea (EMS) observed for S5. A non-sapropel sediment interval with elevated Ba content and depleted ¹⁸O/¹⁶O ratios in planktonic foraminifer calcite was detected between S6 and S5 that corresponds to the weak northern hemisphere insolation maximum at 150 kyr. At this time, productivity apparently increased up to five times over surrounding intervals, but abundant benthic fauna show that the deep water remained oxic. Following our interpretation, the interval denotes a failed sapropel, when a weaker monsoon did not force the EMS into permanent stratification. The comparison of interglacial and glacial sapropels illustrates the relevance of climatic boundary conditions in the northern catchment in determining the facies and spatial variability of sapropels within the EMS.     

Systematics of the Dactylorhiza euxina/incarnata/maculata polyploid complex (Orchidaceae) in Turkey: evidence from allozyme data

 Material of Dactylorhiza were sampled from 49 localities in Turkey and investigated for allozyme variation at ten loci (nine enzyme systems). Among diploids, the Anatolian D. osmanica and D. umbrosa were allozymically variable, but not distinct from each other or from D. incarnata. Dactylorhiza saccifera contained the same alleles as the European D. fuchsii. Dactylorhiza iberica and D. euxina were distinct from each other and the other diploids. On basis of allozyme patterns three distinct allotetraploid genotypes were distinguished, and each of them could be treated as a separate species. Dactylorhiza nieschalkiorum is similar to European allotetraploids, and may have arisen from hybridization between D. incarnata s.l. and D. saccifera. Dactylorhiza urvilleana may have arisen from parents related to present-day D. saccifera and D. euxina, but it also contains additional alleles that have not been found in any of the diploids investigated. A third allotetraploid known from four populations in the Ardahan and Kars provinces of north-eastern Turkey combines the allozyme patterns found in material of D. incarnata s.l. from the same area with those from D. euxina. It is here described for the first time as D. armeniaca. Received November 14, 2000 Accepted June 20, 2001     

Escape of volcanic gas into shallow groundwater systems at Unzen Volcano (Japan): evidence from chemical and stable carbon isotope compositions of dissolved inorganic carbon

 Chemical and stable carbon isotopic analyses of dissolved inorganic carbon (DIC) were carried out for groundwater samples collected from cold springs and shallow wells in the Unzen volcanic region in 1999 and 2000. All of the data sets plotted on the carbon isotope ratio (δ¹³C) vs 1/DIC diagram can be explained by mixing of volcanic CO₂ with DIC equilibrated with soil CO₂. Groundwater DIC showing a high mixing ratio of volcanic CO₂ appears to have a tendency to distribute along two major faults near the activity center of the 1990–1995 eruption. This suggests that these faults are escape routes of volcanic CO₂ diffused into the volcanic edifice. The total flux of the volcanic DIC discharged from the cold springs is shown to be one to two orders of magnitude lower than the roughly estimated flux of volcanic CO₂ discharged from the summit during the eruptive period. Received: November 10, 2001 / Accepted: June 6, 2002 Acknowledgments The Unzen Scientific Drilling Project, Ministry of Education, Culture, Sports, Science and Technology (Japan), provided funding. We acknowledge G. Lyon and W. Gooley for stable carbon isotope measurement, K. Amita for DIC analysis, and students of Kyoto University and Okayama University of Science for assistance in field work. Correspondence to:S. Ohsawa     

Deformability of Fe(II)CO and Fe(III)CN groups in heme protein models: nonlocal density functional theory calculations

 High-quality nonlocal density functional calculations have been carried out on the deformability of Fe(II)CO and Fe(III)CN units in model compounds of heme proteins. The results confirm our previous finding with a local functional that the Fe(II)CO unit is significantly deformable with respect to tilting and bending. This deformability stems in large part from a large, negative interaction constant between the FeC tilt and FeCO bend coordinates. The Fe(III)CN unit is also significantly deformable, but in this case the deformability results from a very small Fe(III)CN bend force constant and the ability of the cyano nitrogen to act as a hydrogen bond acceptor. The prediction that the energetic penalty associated with deforming the Fe(II)CO unit is relatively modest indicates that such deformations are unlikely to be the dominant contributor to myoglobin's discrimation against CO in favor of O₂. Received, accepted: 16 June 1997     

Coexistence and niche segregation by field populations of the parasitoids Cotesia glomerata and C. rubecula in the Netherlands: predicting field performance from laboratory data

Field experiments with foraging parasitoids are essential to validate the conclusions from laboratory studies and to interpret differences in searching and host selection behaviour of parasitoid species. Furthermore, field experiments can indicate whether the parameters measured in the laboratory are relevant to elucidation of the ecological processes under study, such as adaptation or species interactions. In previous extensive laboratory studies we studied plant- and host-searching behaviour, host acceptance, host suitability; host plant preference, and learning of two congeneric parasitoids of Pieris caterpillars: the generalist Cotesia glomerata, which has been reported to attack several Pieridae species, and C. rubecula, a specialist of the small cabbage white Pieris rapae. In the present field study our aim was to verify the importance of these previous laboratory findings for explaining the performance of these two species in the field. We investigated experimentally whether parasitism on three Pieris species varied with parasitoid species and with food plant of the caterpillars. We exposed different types of host plants, infested with different Pieris species, to parasitism by natural populations of Cotesia species, by setting the experimental plants out in Brussels sprouts cabbage fields. Furthermore we made direct observations of parasitoid foraging in the field. In general, the field results confirmed our predictions on the range of host plant and host species used in the field. The two Cotesia species appear to coexist through niche segregation, since C. glomerata was mainly recovered from P. brassicae and C. rubecula from P. rapae. Although C. glomerata is a generalist at the species level, it can be a specialist at the population level under certain ecological circumstances. Our study shows the importance of variation in host plant attraction and host species acceptance in restricting host plant and host diet in the field. Furthermore the results suggest that, at least in the Netherlands, specialisation of C. glomerata on P. brassicae may occur as a result of C. rubecula outcompeting C. glomerata in P. rapae larvae. Received: 8 July 1999 / Accepted: 31 January 2000     

Mapping of intra-locus duplications and introgressed DNA: aids to map-based cloning of genes from complex genomes illustrated by physical analysis of the Rx locus in tetraploid potato

 We describe here novel approaches to high-resolution mapping of repeated and introgressed DNA which may prove generally useful in map-based cloning from complex genomes. These approaches were developed in order to clone the Rx locus in potato. First, we prepared a BAC library from a tetraploid plant carrying Rx in the duplex condition (Rx, Rx, rx, rx). BAC clones were then isolated with close markers on either side of Rx. However these clones did not extend across Rx: in the cloned DNA the closest markers to Rx were separated by single recombination events on either side of Rx. To bridge the gap we exploited the finding that the BAC clones on the right side of Rx contained resistance-gene homologues. Anticipating that there would be duplicated copies of these resistance gene homologues in the vicinity of Rx, we used low-stringency PCR conditions to identify additional markers. One of these markers was completely linked to Rx in our mapping population and was used to isolate a BAC (BAC77) that had not been previously identified by screening with Rx-flanking markers. Based on two criteria it was concluded that BAC77 spans Rx. There was a chromosomal recombination in one plant of our mapping population that separated the BAC77 right end from Rx. On the other side of Rx it was found that the BAC77 left end was outside the region of DNA carrying Rx that had been introgressed into potato cv Amaryl from a Solanum tuberosum ssp. andigena accession CPC1673. Received: 13 July 1998 / Accepted: 17 September 1998