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1.
In many fishes, individuals prefer to associate with phenotypically similar or conspecific individuals (conspecific cueing). Such phenotypic segregation can be an important evolutionary driver, for example, in intralacustric sympatric speciation processes. I examined conspecific cueing in two species of sympatric pupfish from Laguna Chichancanab in southern Mexico: the little shoaling and highly territorial Cyprinodon beltrani and the highly shoaling but non-territorial C. simus. Females were tested for shoal species preferences in two testing scenarios: (1) a sequential choice test where shoals of four conspecific or four heterospecific (Cyprinodon sp. or Poecilia reticulata) females were presented in succession, and (2) a simultaneous choice test where female shoals of both Cyprindon species were presented concurrently. Overall, higher shoaling in C. simus was corroborated in this study. In the sequential test, no effect of the type of stimulus shoal (con- or heterospecific) on shoaling behavior was detected. In the simultaneous tests, C. beltrani, but not C. simus females showed a preference for the conspecific shoal. It seems possible that C. simus females did not evolve species recognition mechanisms because no other Cyprinodon species in the Laguna Chichancanab shows equally high shoaling, which automatically leads to the formation of single-species (i.e., C. simus-) shoals. C. simus males do not establish long-term territories, but rather spawn within shoals, whereas C. beltrani females approach males in their breeding territories to spawn. I discuss that this behavioral difference still provides a powerful reproductive isolation mechanism even in the absence of conspecific cueing in C. simus.  相似文献   

2.
Summary  Three new species are described in Barleria L. sect. Stellatohirta M. Balkwill from tropical Africa: B. aristata from south-central Tanzania, B. aenea from south-western Tanzania and northeast Zambia, and B. purpureotincta from south-western Zambia. Their affinities and conservation status are discussed.  相似文献   

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The present paper focuses on the results of taxonomic, faunistic and chorologic investigations on Argestidae Por, 1986 (Copepoda, Harpacticoida). All argestid species collected during the cruise M42/3 of RV “Meteor” (1998) are new to science. In the present contribution, two species are described and united within Bodinia gen. nov.: Bodinia meteorensis sp. nov. and Bodinia peterrummi sp. nov. The new genus is placed as incertae sedis in Argestidae in light of uncertainty concerning the phylogenetic relations within this group and even its status as a monophylum. The question is discussed how members of Argestidae, previously seen as a deep-sea taxon, may have colonized the shallow-water habitat of the Great Meteor Seamount plateau.  相似文献   

5.
Summary  A key is presented to the Nepenthes group Montanae in Peninsular Malaysia, Thailand and Cambodia. Nepenthes bokor Cheek is described from Cambodia and Nepenthes thai Cheek from peninsular Thailand. The affinities of both taxa are discussed and their conservation status assessed.  相似文献   

6.
Seagrasses are well known ecosystem engineers that can significantly influence local hydrodynamics and the abundance and biodiversity of macrobenthic organisms. This study focuses on the potential role of the seagrass canopy structure in altering the abundance of filter-feeding organisms by modifying the hydrodynamic driven food supply. We quantified the effect of two ecosystem engineers with contrasting canopy properties (i.e. Zostera noltii and Cymodocea nodosa) on the food intake rate of a suspension-feeding bivalve Cerastoderma edule living in these seagrass meadows. Field experiments were carried out in two seagrass beds (Z. noltii and C. nodosa) and bare sediment, located on sandflat characterised by a relatively high hydrodynamic energy from waves and currents. Results demonstrated that the filter-feeding rate was almost twofold increased when C. edule was inhabiting Z. noltii meadows (1.10 ± 0.24 μg Chl g Fresh Weight−1) when compared to cockles living on the bare sediment (0.65 ± 0.14 μg Chl g FW−1). Intermediate values were found within C. nodosa canopy (0.97 ± 0.24 μg Chl g FW−1), but filter feeding rate showed no significant differences with values for Z. noltii meadows. There were no apparent correlations between canopy properties and filter-feeding rates. Our results imply that food refreshment within the seagrass canopies was enough to avoid food depletion. We therefore expect that the ameliorated environmental conditions within vegetated areas (i.e. lower hydrodynamic conditions, higher sediment stability, lower predation pressure…) in combination with sufficient food supply to prevent depletion within both canopies are the main factors underlying our observations.  相似文献   

7.
The larch bark beetle (Ips subelongatus), which occurs in larch plantations over a vast area of eastern Asia, infects both dying and fallen trees. When its population reaches a high density, the beetle may also infect healthy trees, resulting in tree decline and, eventually, death. Leptographium spp., in both their sexual and asexual states, are mainly associated with conifer-infesting bark beetles; some species are important tree pathogens. The aims of this study were to identify the Leptographium spp. associated with I. subelongatus infestations of Larix spp. in northern China and to examine their pathogenicity towards the tree. Morphological studies and phylogenetic approaches based on multilocus DNA sequence data (ITS2- partial r28S, partial β-tubulin, and EF-1α gene regions) showed that three Leptographium species occur in association with I. subelongatus in the areas investigated: Leptographium taigense, which is recorded in China for the first time, and two new species, namely L. innermongolicum sp. nov. and L. zhangii sp. nov. Leptographium innermongolicum is closely related to L. taigense, whereas L. zhangii belongs to the Grosmannia piceaperda species complex. The pathogenicity of these Leptographium species towards mature Larix spp. was tested by stem inoculation in forests. All inoculations only resulted in small lesions on the inner bark; therefore, the three Leptographium species were not considered to be pathogenic.  相似文献   

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Five isolates of a species of Colletotrichum were collected from Japanese barnyard millet (Echinochloa utilis) in Japan. Although the fungus had once been identi-fied as C. graminicola sensu lato, it was clearly different from C. graminicola isolated from maize (Zea mays) in its falcate and short conidia, 18.0–22.2 μm in length, cultural characteristics, and specific pathogenicity to E. utilis. Moreover, molecular phylogenetic analyses using sequences of rDNA-ITS, HMG, and SOD2 indicated a monophyly of the isolates. A new species, Colletotrichum echinochloae, is then proposed based on the morphological, pathological, and molecular characteristics.  相似文献   

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11.
Gymnopilus ombrophilus sp. nov., growing on rotten wood of conifers and hardwoods from Niigata, Japan is described and illustrated. It is characterized by its medium-sized, brownish-orange basidiocarps with a finely squamulose pileus, stipe lacking an annulus, and mild taste, and microscopically by dextrinoid, small, broadly ellipsoid basidiospores. The new species belongs to the section Microspori. The differences between the taxon and similar species are briefly discussed.  相似文献   

12.
Summary The biology of the invasive Polistes dominulus and the native P. fuscatus was compared at a field site in Rochester, Michigan over a two-year period. Colonies nesting semi-naturally in plywood nestboxes were studied using videography, extensive surveys, and colony-specific marking of gynes.Both single- and multiple-foundress colonies of P. dominulus were significantly more productive than comparable colonies of P. fuscatus. The disparity in productivity was significantly more pronounced in single-foundress colonies than in multiple-foundress colonies. P. dominulus had significantly shorter larval and pupal development times than P. fuscatus, which allowed P. dominulus to produce its first workers about a week earlier than P. fuscatus. P. dominulus had a number of additional advantages over P. fuscatus that contributed to its productivity including (1) significantly less parasitism by Strepsiptera, (2) significantly greater probability of renesting after predation by raccoons, (3) significantly lower usurpation pressures, and (4) possibly longer foraging days . The recovery of colony-marked foundresses indicated that gynes of P. dominulus suffered significantly greater mortality than gynes of P. fuscatus during winter diapause and that foundresses of both species were equally, strongly philopatric.P. dominulus is likely replacing P. fuscatus in many areas of southeastern Michigan via indirect or exploitative competition. The two species may be competing for nest sites.Received 7 July 2003; revised 10 October 2003; accepted 3 November 2003.  相似文献   

13.
Cortinarius breviradicatus sp. nov., found in deciduous forests, is described and illustrated from Niigata, Japan. It is characterized by its medium-sized to large dark brown basidiocarp, acutely conical pileus, and rooting stipe, and by subglobose to broadly ellipsoid basidiospores. In addition, the extracting solution from its basidiocarps exhibits a strong fluorescence around 400–430 nm in ultraviolet radiation (250 nm), which was observed in a species of Cortinarius sect. Orellani. The new species belongs to the section Orellani. The differences between the new taxon and similar species are briefly discussed.  相似文献   

14.
Paraliparis adustus sp. nov., a snailfish species from the Bering Sea near the Aleutian Island Archipelago, Alaska, is described based on a single mesopelagic specimen. This new species is clearly distinguished by a combination of several morphological features and meristic counts, including long pointed gill rakers with 0–3 spinules at or near the tip, anus positioned forward near the pectoral symphysis, and color uniform brown. Paraliparis bullacephalus sp. nov. from Shelikof Strait, Gulf of Alaska, is also described. This new species is very similar in meristic characters and general body shape and size to P. holomelas Gilbert, but differs primarily in morphological features of the head, particularly in the shape of the dorsal contour of the head, snout, and opercular flap, mouth size, and eye position.  相似文献   

15.
Two new species of Lirula (L. japonica and L. exigua) on Abies mariesii collected in subalpine areas of northern Japan are described as members of Rhytismatales, Discomycetes. Lirula japonica causes needle cast in fir, but L. exigua seems to occur on the needles of physically damaged twigs. Morphological characteristics of both species are discussed.  相似文献   

16.
Summary  A new and probably endemic species of Cambessedesia DC. is described from campo rupestre vegetation, as part of a floristic survey of Melastomataceae from the S?o José mountain range, Tiradentes District, Minas Gerais State, Brazil. Miscellaneous  Accepted for publication April 2008.  相似文献   

17.
Polygala pauciramosa, a new species from the Federal District and the state of Goiás is described, illustrated, and compared with related species of Polygala subgenus Hebeclada. The new species is an herb that grows in seasonally to permanently wet savannas. A key to the species of Polygala subgenus Hebeclada from Goiás state, Brazil is provided.  相似文献   

18.
In littoral zones of aquatic systems, submerged macrophytes have marked structural variation that can modify the foraging activity of planktivores. Swimming and feeding behavior of Pseudorasbora parva and Rasbora daniconius (Cyprinidae) on their prey Daphnia pulex and Artemia salina, respectively, was studied in a series of laboratory experiments with varying stem densities. A range of stem densities was tested for each of the two species to compare the effect of simulated macrophytes on prey attack rates and swimming speed, average stem distance (D) was measured in fish body lengths for each of the two fish species. We found that, with reducing average stem distance, the attack rate decreased in the similar trend and this trend was similar for both fish species. However, the species differed in the degree to which swimming activity was hindered at increased stem densities, and this was due to species-specific differences in the distance moved with one tail beat. Therefore, we conclude that the reductions in swimming speed with reduced average stem distance are due to the differences in fish movement per tail beat.  相似文献   

19.
First year ontogenetic diet patterns and size-dependent diet partitioning of two coexisting piscivorous percids, pikeperch and Volga pikeperch were analysed in Lake Balaton. Diet patterns of the two pikeperches followed a common trend, catching larger preys at larger sizes, but in details they were different. Until 20–30 mm size age-0 pikeperch fed on planktonic microcrustaceans and were found only in the pelagic zone. After this size, from the end of May, a part of the stock shifted habitat and moved to the littoral zone to feed on Limnomysis benedeni. Majority of the stock stayed in the pelagic zone and shifted to Leptodora kindtii. In the pelagic group early piscivory, mainly cannibalism, occurred only sporadically. However, the few individuals that reached 100 mm size during the first year were typically piscivorous. Volga pikeperch stayed in the pelagic zone during the first year and shifted from planktonic microcrustaceans to benthic macroinvertebrates. General patterns of the first year diet ontogeny were similar in the different areas of Lake Balaton in both pikeperches with only some differences in the secondary food resources, especially in the share of chironomids. Chironomids were eaten at highest ratio by the two fish species in the Keszthely basin in accordance with their abundance pattern. Maximum prey sizes increased significantly with predator size in both pikeperch and Volga pikeperch. However, pikeperch ate much larger prey than did Volga pikeperch at the same size although they have a similar mouth gape to length ratio. These two, closely related pikeperches, although occur in the same habitat and have similar patterns of diet ontogeny, effectively partition food resources in Lake Balaton during the first growing season, except in the very beginning of their ontogeny at L = 5–10 mm size. It appears that age-0 Volga pikeperch is not a significant competitor for the economically highly rated pikeperch in Lake Balaton. On the other hand, it is age-0 pikeperch that might affect Volga pikeperch during its early ontogeny, in the planktivorous stage.  相似文献   

20.
The present paper reports a protocol for minimum growth conservation of Drosophyllum lusitanicum (L.) Link. in vitro. Double-node cuttings were maintained for 4, 8 and 12 months at 5 or 25 °C in the dark. The effects of sucrose either alone at 5, 20, 30, 40 and 60 g dm−3 or at 20, 40 and 60 g dm−3 in combination with 20 g dm−3 mannitol, on survival and post-storage shoot multiplication efficiency were investigated. The cultures could effectively be conserved under minimum growth at 5 °C for 8 months on Murashige and Skoog’s medium supplemented with 60 g dm−3 sucrose, 20 g dm−3 mannitol and 0.91 μM zeatin. Following extended conservation, the cultures could be successfully regenerated into new shoots, and they were morphologically similar to those of non-stored controls.  相似文献   

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