Search results for "ACEA"
showing 10 items of 2814 documents
Native and subunit molecular mass and quarternary structure of the hemoglobin from the primitive branchiopod crustacean Triops cancriformis
2006
Many branchiopod crustaceans are endowed with extracellular, high-molecular-weight hemoglobins whose exact structural characteristics have remained a matter of conjecture. By using a broad spectrum of techniques, we provide precise and coherent information on the hemoglobin of one of the phylogenetically ‘oldest’ extant branchiopods, the tadpole shrimp Triops cancriformis. The hemoglobin dissociated under reducing conditions into two subunits, designated TcHbA and TcHbB, with masses of 35 775 ± 4 and 36 055 ± 4 Da, respectively, determined by ESI-MS. Nonreducing conditions showed only two disulfide-bridged dimers, a homodimer of TcHbA, designated D1 (71 548 ± 5 Da), and the heterodimer D2 (…
Effects of defoliation on male and female reproductive traits of a perennial orchid, Dactylorhiza maculata
2000
1The effects of defoliation on male reproductive traits of plants have received little attention. We conducted two field experiments with Dactylorhiza maculata (L.) Soo to examine the effects of defoliation on both male and female reproductive traits. We removed 0, 50 or 100% of leaves prior to flowering. The quality of pollen was tested by transferring pollen from the differently treated plants to untreated plants of the same population. 2The non-defoliated plants did not differ from the defoliated plants in mass of pollinia. No differences were found in the weight of seed capsules or in the proportion of embryonic seeds raised by flowers receiving pollen from differently treated pollen do…
Reproductive success ofDactylorhiza incarnatassp.incarnata(Orchidaceae): the effects of population size and plant visibility
2007
Reproduction of plants pollinated solely by flower-visiting animals depends on the ability of the population and each of its flowering member to attract pollinators. Factors affecting the pollination of nectarless species differ somewhat from those affecting the pollination of rewarding species due to the avoidance behaviour of pollinators after visiting empty flowers. We studied a non-mimic food-deceptive orchid, Dactylorhiza incarnata ssp. incarnata, in 16 populations in central Finland to examine if population properties and plant size affected reproductive success of plants. We found that the number of flowering plants increased total pollinia removal and seed production of the populati…
RAPD evidence for a sister group relationship of the presumed progenitor-derivative species pairSenecio nebrodensis andS. viscosus (Asteraceae)
1998
The phylogenetic and phenetic analysis of 109 RAPD polymorphisms inS. nebrodensis, a perennial and self-incompatible endemic of four mountain ranges in Spain, andS. viscosus, a self-compatible annual widespread in Europe, as well asS. lividus, S. sylvaticus andS. vulgaris revealed a sister group relationship between the first two species. This result contrasts sharply with the earlier hypothesis based on isozyme variation thatS. viscosus originated from within a paraphyleticS. nebrodensis and that the two species represent a progenitor-derivative pair. After considering possible reasons for the sister group relationship found, including the possibility of rooting artefacts, it is concluded …
Growth and production of three macrozoobenthic species in the Gulf of Riga, including comparisons with other areas
1999
Three soft-bottom stations in the southern part of the Gulf of Riga were studied during the period December 1993 to January 1995. The amphipods, Monoporeia affinis and Pontoporeia femorata, and the poychaete Marenzelleria viridis, were analysed for production, using the cohort growth method. Animals were also analysed for carbon and nitrogen content in a CHN-analyser. Based on size measurements, the quantitative data were divided into age-classes and the growth of each cohort was calculated first as wet weight and then converted into carbon and nitrogen content. Total annual production of each species was calculated as well as turnover ratios. The turnover ratio for Monoporeia affinis was e…
Distribution, frequency and diversity of Bacillus thuringiensis in olive tree environments in Spain
1997
Summary Bacillus thuringiensis was isolated from samples collected from olive tree related habitats (olive groves, olive storage facilities and oil mills) of different olive producing regions in Spain. This bacterium was found in a high percentage (92%) of samples. From 72 samples analysed, 2244 sporulating colonies were selected and observed under phase contrast microscopy. From these, 414 colonies (18%) were classified as B. thuringiensis based on the production of parasporal crystals. A great variability of spore, crystal size and morphology was observed. The results indicate that olive groves are as rich as soil olive mills and olive storage facilities regarding the B. thuringiensis pop…
The effectiveness of pre- and post-zygotic barriers in avoiding hybridization between two snapdragons (Antirrhinum L.: Plantaginaceae)
2014
Reproductive barriers play an important role in the maintenance of species boundaries. However, to date, few studies have provided a detailed analysis of reproductive isolation barriers between species or examined their importance in maintaining species identity. This is the first detailed study into pre- and post-zygotic reproductive isolation barriers in Antirrhinum, based on a mixed population with two species that rarely co-occur. The study revealed that pollinator constancy and preference and poor hybrid seed viability were the most important reproductive isolating mechanisms. Reproductive isolation was practically complete by both pre- and post-zygotic barriers. Average pre-zygotic is…
Late Quaternary history ofHippophaë rhamnoidesL. (Elaeagnaceae) inferred from chalcone synthase intron (Chsi) sequences and chloroplast DNA variation
2006
Fossil pollen records indicate that Hippophae rhamnoides (Sea Buckthorn) was widespread on late- and early postglacial raw soils throughout much of central and northern Europe, but that Early Holocene reforestation restricted populations to northern coastal habitats, or along mountain streams in the Alps, Pyrenees, and Carpathians. We used sequence variation at the nuclear chalcone synthase intron ( Chsi ), in conjunction with chloroplast DNA–restriction fragment length polymorphism data, to investigate the intraspecific phylogeny, phylogeographic structure, and expansion demographic history of this dioecious and wind-pollinated shrub at its range-wide scale in Europe and Asia Minor. Four m…
A newCentaureaspecies (Asteraceae) from Mt Sakar, South-eastern Bulgaria
2013
A new species of Centaurea, C. sakarensis, known from a single locality north-east of the village of Lessovo on Mt Sakar, is described and illustrated. It belongs to C. sect. Acrolophus, and its morphologically closest relative is C. cariensis Boiss., a Turkish endemic from western and south-western Anatolia. The new species is currently known from a single population of about 1000 individuals, growing on open stony calcareous places, at 475 m a.s.l., and should be classified as Critically Endangered, (B1ab[i, ii, iii]+2ab [i, ii, iii]).
Detection of ephemeral genetic sub-structure in the narrow endemic Abies nebrodensis (Lojac.) Mattei (Pinaceae) using RAPD markers
2004
A. nebrodensis (Nebrodi fir, Sicilian fir) is restricted to a small area of the Madonie Natural Park in Sicily. According to recent estimates, its only population consists of 30 adult individuals and a fluctuating number of juveniles derived from natural regeneration; besides, some hundreds of cultivated plants are preserved as ex situ collection. We used RAPD data from six 10-mer primers to examine the consequences of extensive historical clearance and human pressures on the extant population. Data from multiple life stages and different habitat conditions were considered, affording an opportunity to ascertain for the first time the structure of genetic variation in the extant uneven-aged …