Mating behavior in eight rotifer species: using cross-mating tests to study species boundaries

We characterized the mating behavior of eight freshwater rotifer species from five different families of Monogononts (Asplanchnidae, Brachionidae, Euchlanidae, Lecanidae, and Trichocercidae). Were corded the percentages of male-female encounters resulting in mating attempts and the number of completed copulations. The characterization of mating behavior also included data on: (1) duration of copulation, (2) female and male swimming speed, (3) sites of initial mating attempts, (4) sites of copulation, and (5) sizes of males and females. In the five families investigated, cross-mating tests may be used to assess the ability of males to discriminate conspecifics, establishing limits to gene flow. We also present data on two families, Brachionidae and Lecanidae where we used cross-mating tests to compare discrimination between conspecific females and those of other species. Brachionus calyciflorus males attempted mating with females of the closely related genus Plationus, but did not attempt mating with Keratella Americana females. Males of other three Brachionidae species only attempted mating with nonspecific females. Lecane quadridentata males attempted to mate with females of two different Lecane species besides their own. Percentages of mating attempts and completed copulations were quantified in all crosses. Lower percentages of copulation after a mating attempt were found among brachionids than among non-brachionids. These data demonstrate that male discrimination of females is an effective pre-mating reproductive barrier in several species of Monogonont rotifers. These results, further suggest that investigations of mating behavior are useful for determining species boundaries in rotifers and perhaps other zooplankters. This revised version was published online in August 2006 with corrections to the Cover Date.     

Micronutrient levels in some temperate European tree species: a comparative field study

Micronutrient concentrations in foliage and stemwood (including bark) of six European tree species (Betula pendula Roth., Quercus robur L., Fraxinus excelsior L., Fagus sylvatica L., Tilia cordata Mill. and Picea abies (L.) Karst.) planted on the same type of soil at six sites in three different countries were studied. Micronutrient concentrations in foliage were considerably higher than in stemwood for all elements and species studied, except for Fe in spruce. Interspecies comparisons revealed significant differences in concentrations both in foliar and stemwood biomass, as well as in stemwood:foliage nutrient ratios. Lime foliage showed a considerably higher concentration of B than all other species, while the stemwood concentration of this element was highest in ash. Mn concentration in both foliar and stemwood biomass of ash was extremely low compared with concentrations in other species. Birch stemwood showed nearly double the level of Zn in other species at all sites. Zn concentrations in the birch foliage were also higher than in other species, with the exception of the Lithuanian sites, which showed lower EDTA-extractable Zn concentrations in the soils. The concentration of Cu was lowest in spruce foliage, while Cu concentrations in stemwood were similar in all species. It was concluded that species-related differences in microelement nutrition must be taken into account when evaluating the nutrient status of common European forest tree species, and when using them as bio-indicators of the effects of environmental pollution.     

Water-stress-induced xylem embolism in three species of conifers

Abstract. The mechanism of water-stress-induced xylem embolism was studied in three species of conifers: Abies balsamea (L.) Mill., Picca rubens Sarg, and Juniperus virginiana L. Each species showed a characteristic relationship between xylem tension and the loss of hydraulic conductivity by air embolism. Abics balsamea and Picca rubens began to embolize at tensions between 2 and 3 MPa and were completely non-conducting between 3 and 4 MPa. Juniperus virginiana was least vulnerable, beginning to embolize at 4 and still retaining approximately 10% conductivity at 10 MPa. As with a previous study of the vessel-bearing Accr saccharum Marsh., a brief perfusion of branch segments with an oxalic acid and calcium solution (10 and 0.1 mol m⁻³. respectively) increased the vulnerability of the xylem to embolism; this was especially pronounced in Abies balsamea . In order to test whether embolism was caused by aspiration of air into functional tracheids from neighbouring embolized, ones (the 'air-seeding'hypothesis), hydrated branch segments were injected with air at various pressures and measured for embolism. Results supported the air-seeding hypothesis because the relationship between injection pressure and embolism for both native and oxalic-calcium-treated segments was essentially the same as for embolism induced by xylem tension. Structural and experimental evidence suggested the air seeding occurred through inter-tracheid pit membranes when the thickened torus region of the membrane became displaced from its normal sealing position over the pit aperture. Thus, the embolism-inducing tension may be a function of pit membrane flexibility. This tension is of ecological significance because it reflects to some extent the range of xylem tensions to which a species is adapted.     

Foliar carbon isotope discrimination in Larix species and sympatric evergreen conifers: a global comparison

Larches (Larix spp.), deciduous conifers, occur in the northern hemisphere in cold-temperate and boreal climates – an environment normally thought to favor evergreen tree species. We compare foliar carbon isotope discrimination (Δ), instantaneous water use efficiency, total foliar nitrogen concentration, and specific leaf area (for a subset of sites) between Larix spp. and co-occurring evergreen conifers at 20 sites throughout the natural range of larches. Except for Larix occidentalis in the xeric Intermountain West, USA, Δ is significantly (P < 0.05) greater for larches than co-occurring evergreen conifers at 77% of the sites, suggesting that larches use water less efficiently. At elevations greater than 3000 m, the Δ of Larix spp. and co-occurring conifers converge, suggesting that water is not the limiting resource. Foliar nitrogen concentration and specific leaf area are two ecophysiological characteristics that are positively correlated with high photosynthetic capacity. Foliar nitrogen concentration is significantly greater for larches than evergreen conifers at 88% of the sites and specific leaf area is approximately three times greater for larches than co-occurring conifers. Future studies should examine the potential effect that global warming may have on the distribution of larch forests because the water use efficiency of larches is commonly less than co-occurring evergreen conifers and the boreal and high-latitude environments are likely to experience the greatest climate warming. Received: 23 May 1997 / Accepted: 28 October 1997     

Quantitative variation in monoterpenes in four species of conifers

Eighteen monoterpenes found in bole and foliage volatiles of four sympatric species of conifers, Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, lodgepole pine, Pinus contorta var. latifolia Engelm., interior spruce, Picea engelmannii×glauca, and interior fir, Abies lasiocarpa×bifolia, in three locations in British Columbia, Canada, were analysed for quantitative variation (N=10 trees per sample) using standard and chiral gas chromatography. There was significant variation in monoterpene composition between bole and foliage in all four species. Principal components analysis revealed that the monoterpene profile of coastal Douglas-fir was significantly different from trees in the interior, supporting the hypothesis that coastal and interior populations represent distinct chemotypes. Although the four species did not differ qualitatively, there were significant differences in their quantitative monoterpene profiles in both bole and foliage. These differences were large enough to suggest that host selection by four species of coniferophagous bark beetles (Coleoptera: Scolytidae), specific to each of the above tree species, may depend in part on perception of, and behavioural response to quantitatively distinct blends of monoterpenes.     

Modified axillary branching in species of the fossil genus Frenelopsis: a new phenomenon among conifers

Shoots of the fossil species Frenelopsis alata (K. Feistmantel) Knobloch (Cheirolopidiaceae) from the Cenomanian of Bohemia and Portugal demonstrate a type of branching not hitherto reported among conifers. It has been interpreted as a modification of conventional axillary branching on the basis of detailed observations on external morphology with the help of comparative studies on living species of the family Cupressaceae (e.g., Callitris species) and other fossils of frenelopsid affinity. The probable nature of the growth pattern of the shoot is discussed.     

Relationships between functional traits and inorganic nitrogen acquisition among eight contrasting European grass species

Backgrounds and Aims Leaf functional traits have been used as a basis to categoize plants across a range of resource-use specialization, from those that conserve available resources to those that exploit them. However, the extent to which the leaf functional traits used to define the resource-use strategies are related to root traits and are good indicators of the ability of the roots to take up nitrogen (N) are poorly known. This is an important question because interspecific differences in N uptake have been proposed as one mechanism by which species’ coexistence may be determined. This study therefore investigated the relationships between functional traits and N uptake ability for grass species across a range of conservative to exploitative resource-use strategies.Methods Root uptake of NH4+ and NO3–, and leaf and root functional traits were measured for eight grass species sampled at three grassland sites across Europe, in France, Austria and the UK. Species were grown in hydroponics to determine functional traits and kinetic uptake parameters (I_max and K_m) under standardized conditions.Key Results Species with high specific leaf area (SLA) and shoot N content, and low leaf and root dry matter content (LDMC and RDMC, respectively), which are traits associated with the exploitative syndrome, had higher uptake and affinity for both N forms. No trade-off was observed in uptake between the two forms of N, and all species expressed a higher preference for NH4+.Conclusions The results support the use of leaf traits, and especially SLA and LDMC, as indicators of the N uptake ability across a broad range of grass species. The difficulties associated with assessing root properties are also highlighted, as root traits were only weakly correlated with leaf traits, and only RDMC and, to a lesser extent, root N content were related to leaf traits.     

Defense mechanisms of conifers : differences in constitutive and wound-induced monoterpene biosynthesis among species

Levels of monoterpene cyclase activity were determined in extracts from wounded and unwounded saplings of 10 conifer species to assess whether oleoresin biosynthesis is induced by stem wounding. Species of Abies and Picea, with low to moderate levels of constitutive monoterpene cyclase activity, exhibited a five- to 15-fold increase in cyclase activity 7 days after wounding relative to unwounded controls. In contrast, species of genera such as Pinus, with high levels of constitutive cyclase activity, did not significantly respond to wounding by alteration in the level of cyclase activity. The highest fold increase in monoterpene cyclase activity was consistently observed in Abies grandis, and the time-course of induction of activity following stem wounding in this species demonstrated a threefold increase at 2 days relative to unwounded controls, rising to a maximum increase in the response at 9 days (greater than 10-fold) followed by an apparent decline. The wound response was localized, and both bark (phloem) and wood (xylem) tissues displayed increased cyclase activity at the wound site. The magnitude of the increase in cyclase activity was dependent on the severity of the wound.     

One species in eight: DNA barcodes from type specimens resolve a taxonomic quagmire

Each holotype specimen provides the only objective link to a particular Linnean binomen. Sequence information from them is increasingly valuable due to the growing usage of DNA barcodes in taxonomy. As type specimens are often old, it may only be possible to recover fragmentary sequence information from them. We tested the efficacy of short sequences from type specimens in the resolution of a challenging taxonomic puzzle: the Elachista dispunctella complex which includes 64 described species with minuscule morphological differences. We applied a multistep procedure to resolve the taxonomy of this species complex. First, we sequenced a large number of newly collected specimens and as many holotypes as possible. Second, we used all >400 bp examine species boundaries. We employed three unsupervised methods (BIN, ABGD, GMYC) with specified criteria on how to handle discordant results and examined diagnostic bases from each delineated putative species (operational taxonomic units, OTUs). Third, we evaluated the morphological characters of each OTU. Finally, we associated short barcodes from types with the delineated OTUs. In this step, we employed various supervised methods, including distance‐based, tree‐based and character‐based. We recovered 658 bp barcode sequences from 194 of 215 fresh specimens and recovered an average of 141 bp from 33 of 42 holotypes. We observed strong congruence among all methods and good correspondence with morphology. We demonstrate potential pitfalls with tree‐, distance‐ and character‐based approaches when associating sequences of varied length. Our results suggest that sequences as short as 56 bp can often provide valuable taxonomic information. The results support significant taxonomic oversplitting of species in the Elachista dispunctella complex.     

Post‐zygotic hybrid viability in sympatric species pairs: a case study from European lampreys

Ecological speciation mechanisms are widely assumed to play an important role in the early stages of divergence between incipient species, and this especially true of fishes. In the present study, we tested explicitly for post‐zygotic barriers to gene flow between a sympatric, recently diverged lamprey species pair that likely arose through ecological divergence. Experimental in vitro hybridization between anadromous parasitic Lampetra fluviatilis and resident nonparasitic Lampetra planeri resulted in a high proportion of embryos capable of attaining the burrowing pro‐larval stage, strongly indicating no post‐zygotic barriers to gene flow between these species. A sympatric, locally‐adapted resident parasitic form of L. fluviatilis was also found to successfully hybridize with both members of this species pair. The consequences of these findings are discussed in the context of lamprey speciation. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 108 , 378–383.     

Cytomorphological spectrum in scar endometriosis: a study of eight cases

OBJECTIVE: Endometriosis due to ectopic endometrial tissue that responds to hormonal stimulation and is extremely rare in a surgical scar appearing in 0.1% of women who have undergone Caesarean section. Fine needle aspiration cytology (FNAC) can be a valuable diagnostic aid in the evaluation of these subcutaneous abdominal masses. METHODS: We present the cytomorphological spectrum in eight cases of abdominal wall endometriosis diagnosed by FNAC over a 6-year period (June 1998-June 2004) in Mubarak Al-Kabeer Hospital (Kuwait). The patients ranged from 27 to 56 years of age. Seven had a prior Caesarean section and one had a hysterectomy for fibroid. They presented 3-8 years later with nodules in/near the abdominal scar. Five cases presented with a painful nodule, fluctuant with the menstrual cycle. RESULTS: Cytological findings comprised epithelial clusters and fusiform stromal cells with numerous haemosiderin-laden macrophages. Mild to moderate epithelial atypia was observed in three cases. A diagnosis of endometriosis was rendered in all the eight cases and tissue was available in four cases. CONCLUSIONS: Endometriotic nodules need to be differentiated from other benign/malignant masses and evaluated for possible malignant transformation. FNAC provides a safe and effective tool for diagnosis thereby obviating the need for other procedures.     

Hunting as a source of alien species: a European review

Hunting activities are responsible for the translocation and restocking of millions of animals throughout Europe, including the introduction of alien species. In a context of the growing use of game translocations and of increasing concern about the impact of biological invasions, our goal is to review the role of alien species introduced primarily for hunting purposes on the European scale. In particular, we explore: (1) the relative importance of game species in the context of alien species introductions; (2) the temporal evolution of the number of species introduced for hunting purposes; (3) the contribution of different taxa; (4) the pattern of introduced game species composition across countries (in terms of similarity), and (5) the underlying human demographic factors driving the diversity of introduced game species per country. According to our results, 24.3% of the mammals and 30.2% of the birds introduced into Europe during the last century were released primarily for hunting purposes, in total, 93 species (63 birds and 36 mammals), the most important taxa being Artiodactyls, Anseriformes and Galliformes. The species composition differed among countries, with a higher diversity of introduced game species in larger countries and in those with a higher human population density and proportion of hunters. This review stresses that hunting was a significant pathway for the introduction of invasive species into Europe in the last century. Since some of the game species introduced have had severe environmental impacts on many European regions, and introductions of non-native game species are still occurring, it is essential to improve regulations and increase public awareness regarding invasive game animals. This will help to preserve biodiversity and improve the sustainability of current hunting schemes in increasingly managed European ecosystems.     

Mechanisms underlying fatigue: a voxel-based morphometric study of chronic fatigue syndrome

Background  

Fatigue is a crucial sensation that triggers rest, yet its underlying neuronal mechanisms remain unclear. Intense long-term fatigue is a symptom of chronic fatigue syndrome, which is used as a model to study the mechanisms underlying fatigue.     

Restocking a keystone species in a biodiversity hotspot: Recovering the European rabbit on a landscape scale

Rabbit populations in Iberia remain at low densities in several areas in which their endangered predators still coexist, and the recovery of these populations is therefore urgent if the integrity of Iberian Mediterranean ecosystems is to be maintained. The enhancement of wild rabbit populations has been attempted through the use of in situ extensive rabbit captive breeding enclosures (restocking plots), which reduce mortality caused by terrestrial predators and dispersal movements and permit the breeding of young individuals which can then naturally disperse to settle in the surrounding areas. However, their effectiveness, the role of its size, the optimal habitat management that should be promoted around them and the habitat features remains uncertain. Here, we show results from a four year study of an ambitious rabbit restocking plan on a landscape scale. We measured rabbit abundance in a vast area in which thirty-two restocking plots were built to create an initial rabbit population for further dispersion, in addition to an intensive habitat management program. We also compared rabbit abundance between managed and unmanaged UTM cells of 2.5 km × 2.5 km. Our results showed that rabbit abundance was three times higher in managed cells, but four years after restocking, rabbit abundances had only reached the threshold needed to support stable Iberian lynx presence (at least 10 latrines per km^?1) in 9 of the 23 managed cells. Rabbit abundance was strongly affected by habitat treatment and scrub coverage. The increase of shelter was useful in low cover areas but ineligible in places with high scrub cover, where the increase of refuge plus scrub clearing to create pastures improve rabbit abundance more effectively. In the light of our results, restocking plots should be built only in places with suitable habitat, whereas pastures should be created in dense scrublands and refuge in low cover areas.     

A study of the desiccation of egg capsules of eight gastropod species

The spawn of five Stylommatophora, one basommatophoran, one prosobranch and one opisthobranch were each desiccated at 25 °C and at various constant relative humidities, and in almost still air. The experimental apparatus incorporated glass "fishpole" balances and a time-lapse cine-camera. Differences in desiccation rates were found to be due to differences in size of the experimental objects, the larger egg-masses losing water at a relatively slower rate than the smaller.
At equilibrium with the atmosphere the marine spawn retained more water than those from other habitats. Different water-retaining capacities probably reflect interesting biophysical characteristics of the mucus of different species.     

Cavitation fatigue and its reversal in sunflower (Helianthus annuus L.)

"Cavitation fatigue" is the increased susceptibility of a xylem conduit to cavitation as a result of its prior cavitation. It was investigated whether cavitation fatigue induced in vivo could be repaired in intact plants. Sunflowers (Helianthus annuus L.) were subjected to soil drought in the greenhouse. Native embolism and vulnerability to cavitation was measured in well-watered controls and after 5 d and 10 d of controlled drought. A dramatic cavitation fatigue was observed where droughted xylem that was refilled in the laboratory developed up to 60 PLC (percentage loss of hydraulic conductivity) at -1 MPa versus only 5.2 PLC in non-droughted controls. Rewatered plants showed the complete reversal of cavitation fatigue over 4 d. Reversal of fatigue was correlated with the refilling of embolized vessels in the intact plants (r(2)=0.91, P<0.01), suggesting that xylem transport to fatigued vessels was required for their repair. The in vivo reversal of fatigue was partially duplicated in excised stem segments by perfusing them with root exudates from droughted (DR) and well-watered (WW) plants. The DR exudate had a greater effect, and this was associated with a greater pH in the DR versus WW saps, but there was no difference in total cation concentration. Perfusions with 2 mM CaCl(2) and KCl solutions also partially reversed cavitation fatigue as opposed to no effect with deionized water, suggesting a role of ions in addition to a pH effect. It is suspected that fatigue is caused by stretching and partial disruption of linkages between cellulose microfibrils in inter-conduit pit membranes during air seeding, and that the reversal of fatigue involves restoring these linkages by ingredients in xylem sap.     

DNA barcodes of eight species in genus Sebastes

DNA barcode is effective for biological taxonomy and is able to identify species from any life-history stage. In the present study, eight species which belong to four different subgenera of genus Sebastes found in China sea waters were identified by cytochrome c oxidase I (COI) barcode. The results indicated that the intra-species variation in DNA barcode was less than inter-species variation. When the phylogenetic trees were reconstructed by neighbor joining (NJ), maximum parsimony (MP), maximum likelihood (ML) and Bayesian methods, all the species clustered in their groups distinguishable by high bootstrap values, which proved that COI barcode is a powerful means to differentiate species of Sebastes and supports their identification. When the molecular tree was compared to the morphological tree, only Sebastes trivittatus in subgenus Sebastocles settled in the different positions. It is suggested that S. trivittatus is one of the shallowest occurring species in the Northwest Pacific due to its life characters.