The relationship between temperature,competition and the potential for colonization of a subtropical pond by Daphnia magna

The role that temperature plays in excluding large daphnid species from subtropical and tropical ponds, and competitive relationships between Daphnia laevis and Daphnia magna, are explored. D. magna, a large temperate species is probably not excluded from subtropical or tropical systems by elevated temperatures. However, D. magna was a poorer competitor, under a restricted set of laboratory conditions, than D. laevis, the only pond dwelling daphnid in subtropical Florida. Competition is proposed as one mechanism that may limit the number of daphnid species in subtropical and tropical ponds and lakes. Reduced environmental fluctuations in subtropical and tropical systems (compared with temperate systems) may allow zooplankton populations to reach an environmental carrying capacity where competition limits the number of similar, coexisting species in a habitat.     

Daphnia (Cienodaphnia) menucoensis (Anomopoda; Daphniidae): a new species from athalassic saline waters in Argentina

Daphnia (Ctenodaphnia) menucoensis n. sp. is described from various localities in arid and semiarid Argentina. D. menucoensis has no ocellus, and a characteristic head, fornices, ephippium and denticular arrangement of postabdomen in females and males. The species belongs to a group, along with D. mediterranea, D. dolichocephala Negrea 1984, and D. salina, sharing ecological and morphological characteristics.     

New species in the rheophilous genus Nicsmirnovius Chiambeng & Dumont, 1999 (Branchiopoda: Anomopoda: Chydoridae) and reassignment of Alona eximia Kiser, 1948 and Alonella fitzpatricki Chien, 1970

A morphological comparison of specimens previously assigned to Alona eximia Kiser, 1948 from tropical Africa, Eastern Asia and the Americas shows that this species-group shares a number of morphological characters on the postabdomen, head pores, first antenna and second and fourth limb that separate them from Alona Baird, 1843 but unite them with Nicsmirnovius Chiambeng & Dumont, 1999. Alonella fitzpatricki Chien, 1970, formerly believed to be a junior synonym of A. eximia, is separated from the latter and assigned to the genus Nicsmirnovius. Two new taxa, from Africa and the Island of Socotra (Yemen) are added to the genus. The relationship between the specialised habitat of these chydorids and their morphology is discussed. The geographic range of all known populations is figured and a key to species is presented.     

Daphnia (Ctenodaphnia) hispanica sp. nov., a new daphnid (Cladocera) from Spain

Daphnia (C.) hispanica n. sp. has thoracic limbs of A D. (C.) atkinsoni type and is very similar toD. chevreuxi Richard, 1896. With this speciesD. (C.) hispanica shares the presence of a soft accessory seta on the outer side of the trunk of the first thoracic limb, apparently unique among the genusDaphnia. Although other morphological characteristics are very similar in this two species, a detailed comparison reveals that they can easily be separated as different species. The most useful features in differentiating both species are:D. (C.) hispanica has a dorsal crest in the head, its rostrum is longer, its accesory seta of the first thoracic limb is more developed, the juveniles are not helmeted and its male postabdomen lacks individual denticles on the anal and preanal margin.The new species is, up to now, restricted to Spain and inhabits the temporary and low mineralized waters of the steppe regions.     

Effects of food limitation and temperature on cladocerans from a tropical Brazilian lake

Food limitation was tested in the laboratory by individual growth and reproduction of two cladoceran species, Ceriodaphnia richardi and Daphnia gessneri, from the shallow tropical Brazilian Lake Monte Alegre. The cladocerans were fed cultivated green alga Scenedesmus spinosus in concentrations of 0.20, 0.10, 0.05, and 0.025 mg C l⁻¹. Higher biomass and growth rates occurred in the two highest-food concentrations; the two lowest ones negatively affected clutch size and first reproduction. The threshold food concentration is lower than 0.025 mg C l⁻¹ and the incipient limiting level is a value between 0.10 and 0.20 mg C l⁻¹. The largest species, D. gessneri, was more sensitive to low food concentrations. The effects of low and high temperatures (19 and 27°C) were evaluated by life table experiments with three cladocerans from the lake—Daphnia ambigua, D. gessneri, and Moina micrura—with no food limitation (1 mg C l⁻¹ of S. spinosus). Higher population growth rates for the three species were found at 27°C; better performance in most life table parameters was observed for the former two species at the highest temperature, D. gessneri being the most sensitive to the lowest temperature. There are indications that temperature is an important abiotic factor that constrains populations of cladocerans for a short period in winter in the lake, when temperature decreases to 18–19°C. However, its influence cannot be separated from a biotic factor such as food, whose effect is stronger in the cool season, when concentrations are lower and contribution of inedible algae is relatively higher.     

Development of tolerance against toxic cyanobacteria in Daphnia

We tested whether previous exposure to a toxic strain of cyanobacteria (Microcystis) affects survival, growth, and reproduction of a common herbivore, Daphnia magna. Samples from three natural populations of D. magna were each divided into two parts; one part was fed a mixture of toxic Microcystis and the non-toxic green alga Scenedesmus whereas the other part was fed only Scenedesmus. After four weeks, we compared the ability of these two populations to withstand the toxic Microcystis by assessing survivorship, growth, and reproduction. We found that the ability of D. magna to cope successfully with toxic Microcystis is improved if the animals have experienced previous exposure to toxic Microcystis. This suggests that the toxin may less affect the D. magna populations that are repeatedly exposed to toxic cyanobacteria in their natural habitat than populations lacking prior exposure. Since the ability to tolerate toxins is manifested in both improved survival and larger size of the animals, it may have considerable impact on zooplankton community composition in fresh-waters.     

Density and size distribution of Daphnia populations at different fish predation levels

Density and size structure changes of natural daphniids populations were studied in enclosures with a different level of fish predation. Daphnia pulicaria was totaly removed in high predation variants, and the differences of the mean body length both in adults and juveniles are apparent between low predation enclosure and enclosure without fish. Daphnia galeata was replaced by D. magna and D. pulicaria in the enclosure without fish. The decline of densities and the substantial (30–50%) and fast (during 12 days) shift of mean body length both in adults and juveniles of D. galeata was induced by the fish (carp fry) introduction to the high predation enclosures.     

Redescription of Diaphanosoma dubium Manuilova, 1964 (Branchiopoda: Ctenopoda: Sididae), and description of a new,related species

The poorly known D. dubium Manuilova is redescribed on extensive material from more than 80 populations from the Russian Far East, Central Asia, Mongolia, China, Japan, Vietnam, the Philippines, Thailand, Malaysia, Bangladesh, India and Sri Lanka. Its morphological variability and geographical distribution are analysed and supplemented by notes on biology. The conspecificity of morphologically different distant populations is discussed. In the northern part of its range, D. dubium was long confused with D. brachyurum or D. leuchtenbergianum, and in the south with D. modigliani. It seems that the recent appearance of D. dubium in fish ponds of Uzbekistan and Kazakhstan was an introduction, together with Far Eastern fish. D. pseudodubium sp.nov., close to but markedly different, is described from two lakes in the lower Amur river system. D. dubium, D. pseudodubium, D. tropicum and D. modigliani s. str. form a group of related species, widely distributed in Eastern and Southern Asia.     

Control of plant-parasitic nematodes by Paecilomyces lilacinus and Monacrosporium lysipagum in pot trials

The common soil inhabiting nematophagous fungus Paecilomyces lilacinus (Thom) Samson and the nematode trapping fungus Monacrosporium lysipagum (Drechsler) Subram were assayed for their ability to reduce the populations of three economically important plant-parasitic nematodes in pot trials. The fungi were tested individually and in combination against the root-knot nematode Meloidogyne javanica (Treub) Chitwood, cereal cyst nematode Heterodera avenae Wollenweber, or burrowing nematode Radopholus similis (Cobb) Thorne on tomato, barley and tissue cultured banana plants, respectively. In all cases, nematode populations were controlled substantially by both individual and combined applications of the fungi. Combined application of P. lilacinus and M. lysipagum reduced 62% of galls and 94% of M.␣javanica juveniles on tomato when compared to the experiment with no fungi added. Sixty five percent of H. avenae cysts were reduced on barley by combined application of fungi. Control of R. similis on banana, both in the roots and in the soil, was greatest when M. lysipagum was applied alone (86%) or in combination with P. lilacinus (96%), using a strategy where the fungi were inoculated twice in 18 weeks growth period. Overall, combined application of P. lilacinus and M. lysipagum was the most effective treatment in controlling nematode populations, although in some cases M. lysipagum alone was as effective as the combined application of fungi, particularly against M. javanica.     

On the plurality of Chydorus sphaericus (O. F. Müller) (Cladocera,Chydoridae), and designation of a neotype from Sjaelsø, Denmark

Two readily distinguishable species of Chydorus sphaericus sens. lat. occur in Salmon Lake, Montana, differing from each other in size and shape of rostrum, headpore configuration, frequency of doubling of teeth on the postabdomen, pattern of reticulation of the shell, and morphology of the mature male, especially the postabdomen, postabdominal claws, copulatory hooks, and rostrum. In any such comparisons, individual specimens are not sufficient; populations are needed to sort out morphological characters associated with instar and sex and character's that change with increasing body size. Comparison of population structure and stage of reproduction can be accomplished by a size-frequency distribution and by specific morphological characters that enable the three male instars to be recognized individually.One species, thought at first to be Chydorus herrmanni, is very close to Chydorus sphaericus sens. str. from Denmark. The other taxon with a short, generally blunt labrum, is described as the new species Chydorus brevilabris. Because of morphological diversity among the entities currently listed as Chydorus sphaericus from around the World, it is certain that a complex of species is represented. To facilitate the eventual resolution of this problem, the population in Sjaelsø, Sjaelland, Denmark has arbitrarily been selected as the standard of comparison, and from this population a neotype and several allotypes have been designated. Cursory examination of various available populations suggests that C. sphaericus sens. str. and C. brevilabris represent a major dichotomy in the sphaericus complex, each branch consisting of an unknown number of closely-related species. Cautions are voiced against assuming that Chydorus sphaericus is a single cosmopolitan and ubiquitous species.This study has been aided by grant GB-29725 for the work in Denmark in 1971–72 and by my present grant DEB 76-20237, both from the National Science Foundation. I am indebted to D. F. Brakke for the samples from Salmon Lake and neighboring localities in Montana and information concerning these localities, and to Brenda J. Hann for dissections and drawings of trunk limbs and help in their interpretation. I am also indebted to Geoffrey Fryer, whose innocent inquiry precipitated this study.     

A Field Experiment to Assess the Transplant Success of Salt Marsh Plants into Tidal Wetlands

Field plots were used to assess the restoration potential of three salt marsh species, Juncus maritimus, Leptocarpus similis and Schoenoplectus pungens, within an established salt marsh near Christchurch, New Zealand. A split-block design was used to asses the effects of soil type, (soil from a proposed marsh construction site or estuarine mud from a natural salt marsh), species and plant source (commercial nursery stocks or natural marsh stock). In December, after 9 months, there was no mortality in L. similis and a significant increase in the biomass compared with J. maritimus. S. pungens failed to regenerate following seasonal die-back. Plant biomass was unaffected by soil type, despite occasional higher salinities recorded in the reclamation soil. Natural stocks had significantly higher biomass than nursery stocks (p < 0.01). These results suggest that both L. similis and J. maritimus are appropriate species for transplanting in the Canterbury region and that the soil from the proposed area is suitable for the restoration and construction of tidal wetlands. The success of the transplants could be enhanced by sourcing hardy stock and management regimes may be necessary to reduce salinity extremes and herbivory by rabbits.     

Daphnia curvirostris Eylmann in Japanese high mountain waters (Cladocera: Daphniidae)

A species of Daphnia, Daphnia curvirostris Eylmann, found in high mountain lakes and ponds in central Japan is described. Although there were some differences in the shape of the male rostrum and the chromosome number between European populations as described by Johnson (1952) and Trentini (1980), and Japanese ones collected from high mountain waters, Japanese specimens had many characteristics similar to the taxon D. curvirostris of Europe.     

Differences in genetic structure and ecological diversity between parental forms and hybrids in a Daphnia species complex

Hybridization is a common phenomenon in Daphnia species complexes. Hybrids often dominate in Daphnia populations; therefore it is worthwhile to look for principal differences between parental and hybrid populations with respect to their genetic structure and clonal differentiation. We studied natural populations of members of the Daphnia galeata/hyalina/cucullata complex in three lakes. In one of these lakes, one parental species (D. galeata) and one hybrid (D. galeata × cucullata) were investigated more intensively. The frequency of sexual reproduction was higher in parental populations, whereas clonal diversity was higher in hybrid populations. Ecological differentiation among clonal groups was more pronounced in the D. galeata × cucullata hybrid compared to D. galeata, whereas selection intensity was weaker. These results are discussed with respect to stability of clonal groups, multiple hybridizations and selective constraints.     

A laboratory study of the feeding of Mesostoma lingua (Schmidt) (Turbellaria: Neorhabdocoela) on Daphnia magna Straus at four different temperatures

Mesostoma lingua eats 0.8 Daphnia magna at 15 °C, and 2.04 at 30 °C. Below 0.5 Daphnia per day (D d^–1) hunger occurs, at any temperature, and mortality increases sharply. The functional response curve appears to be linear, but saturation was not fully reached at 5 D d^–1, the highest food level applied in the present study. All food regimes (above hunger level) and temperature regimes differed significantly from each other; factor interactions were of increasing importance at higher temperatures.Longevity, above hunger level, decreased with temperature. Peak longevity at low temperature may be weakly associated with relatively low food levels.     

A light and electron microscopical study of the green flagellateSpermatozopsis similis spec. nova

The green flagellateSpermatozopsis similis spec. nova has been studied in culture by light and electron microscopy. The flagellate bears two flagella, is naked and has a characteristic crescent and spirally twisted cell shape. The two flagella are of subequal length, each with a prominent hair-point. Each cell contains two contractile vacuoles, a single chloroplast with an anterior eyespot but lacking a pyrenoid, an anteriorly located nucleus, a single dictyosome associated with the posterior end of the nucleus, a single mitochondrion posterior to the nucleus and associated with a small microbody, some conspicuous vacuoles, and a greater number of secondary cytoskeletal microtubules which probably are responsible for maintaining the peculiar shape of this species. SinceS. similis in culture is only biflagellate, it cannot be accommodated within the quadriflagellate, but otherwise very similar speciesS. exsultans. Spermatozopsis similis is compared with other green flagellates and is shown to share common ultrastructural characters withChlamydomonas-type green algae.     

四川省香薷属植物地理分布新记录

报道了四川省香薷属植物地理分布新记录1种——四方蒿(Elsholtzia blanda Benth.)。四方蒿主要分布于中国西南部（云南、贵州、广西）至东南亚及南亚的热带地区,在四川为新记录,且是该种分布区的北缘。凭证标本存放于上海辰山植物园标本馆（CSH）。     

Phylogeography of Wild Musk Shrew (Suncus Murinus) Populations in Asia Based on Blood Protein/Enzyme Variation

The musk shrew (Suncus murinus) is an insectivore species that inhabits tropical and subtropical Asia widely. To clarify the genetic relationship among wild musk shrew populations, we examined the electrophoretic variants of biparentally inherited genetic markers at 10 loci coding for eight blood proteins/enzymes in a total of 639 animals and compared the results obtained from the mitochondrial DNA data. The principal-component analysis performed using the allele frequency data revealed that the 17 populations could be divided into two major groups, a South Asian group and a Southeast Asian group that includes several island populations bound by Myanmar. The degrees of genetic divergence among populations were higher within the Southeast Asian group than within the South Asian group. This finding was incongruent with the mtDNA diversity. Analysis conducted at the individual level showed that a shrew from the central region in Myanmar that carries a South Asian type of mtDNA showed the electrophoretic variants specific to the Southeast Asian group, suggesting that this region is a contact zone between the two major groups.     

Daphnia (Ctenodaphnia) Mediterranea: A new species of hyperhaline waters,long confused with D. (C.) Dolichocephala Sars, 1895.

A very particular form of Daphnia (Ctenodaphnia), adapted to life in epicontinental hyperhaline waters of Mediterranean arid regions had long been confused with Daphnia (Ctenodaphnia) dolichocephala Sars, 1895. In this paper the morphological and ecological differences between the two taxa are pointed out and comparison is made with another closely related Rumanian form (Daphnia cf. mediterranea) and with the related Spanish species (D. atkinsoni and D. chevreuxi). The Daphnia of saline environments is described here as Daphnia (Ctenodaphnia) mediterranea. The most important differential characters of this new species are: 1) the short and widely rounded rostrum; 2) dorsal ridge of the female extends to the anteriormost part of the head; 3) elliptical ephippium with a ride anterior margin; convex shape and separate from the dorsal ridge; 4) males possessing a very long antennule base that reaches the distal limit of the head.     

Geographic partitioning of chloroplast DNA variation in the genusDatisca (Datiscaceae)

Datisca (Datiscaceae) is a ditypic genus with an intercontinentally disjunct distribution. Chloroplast DNA restriction site data was obtained from 23 populations and four 10–20 year old herbarium specimens ofD. glomerata and three populations ofD. cannabina from throughout their geographic ranges in western North America and southwest-central Asia, respectively. InD. glomerata, plastome diversity is partitioned geographically. All populations from southern California have a common plastome, while most populations north of this region share a relatively divergent plastome (0.49% sequence divergence). Likewise, these plastomes are highly divergent (0.87% mean sequence divergence) from those found inD. cannabina. Biogeographic processes dating to the Pleistocene and Late Miocene may be responsible for these intra- and interspecific patterns of chloroplast DNA divergence.     

Molecular phylogenetic analyses reveal a close relationship between powdery mildew fungi on some tropical trees and Erysiphe alphitoides, an oak powdery mildew

To investigate the phylogenetic relationships among the powdery mildew fungi of some economically important tropical trees belonging to Oidium subgenus Pseudoidium, we conducted molecular phylogenetic analyses using 30 DNA sequences of the rDNA internal transcribed spacer (ITS) regions and 26 sequences of the domains D1 and D2 of the 28S rDNA obtained from the powdery mildews on Hevea brasiliensis (para rubber tree), Anacardium occidentale (cashew), Bixa orellana, Citrus spp., Mangifera indica (mango), and Acacia spp. The results indicate that the powdery mildew fungi isolated from these tropical trees are closely related to one another. These powdery mildews are also closely related to E. alphitoides (including Erysiphe sp. on Quercus phillyraeoides). Because of the obligate biotrophic nature of the powdery mildew fungi, the relationship between powdery mildews and their host plants is conservative. However, the present study suggests that a particular powdery mildew species has expanded its host ranges on a wide range of the tropical trees. This article also suggests that a powdery mildew fungus distributed in temperate regions of the Northern Hemisphere expanded its host ranges onto tropical plants and may be a good example of how geographical and host range expansion has occurred in the Erysiphales.