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1.
Daniel J. D. Natusch Jessica A. Lyons 《Biological journal of the Linnean Society. Linnean Society of London》2012,107(2):269-276
We describe a 15‐year study of the loss of reproductive fitness and population decline in Adenostoma sparsifolium, a rosaceous shrub endemic in the fire‐prone chaparral vegetation of southern California (USA) and adjacent northern Baja California, Mexico. Our studies of background extinction concentrated on small relict populations occurring in the eastern Santa Monica Mountains where reproduction is genetically compromised by uniquely high rates of embryonic/endosperm abortion (97–99%) resulting largely from self‐pollination in highly heterozygous populations. Environmental factors further reduce reproductive fitness. The relatively few viable seeds produced are not well adapted to survive wildfires that are a regular (approximately 21 years) occurrence in chaparral. Seedling recruitment after burning is rare and any established seedlings ultimately die from the annual 4–9‐month summer droughts typical of Mediterranean climates. Adult mortality is manifest from wildfire (approximately 6%) and occasional multiple‐year droughts (approximately 15%). Given the virtual absence of new post‐fire reproduction and a low but persistent rate of adult mortality, slow population demise resulting in background extinction is inevitable. We posit that A. sparsifolium is ecologically ‘out of place’ in the present chaparral environment and appears best adapted to a moister climate with summer rains and few wildfires that prevailed before the increasing aridity and warming from mid‐Holocene to the present. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105 , 269–292. 相似文献
2.
Eight new species of Hieracium sect. Tridentata (Asteraceae) from southern and northern Sweden
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Eight new species of Hieracium sect. Tridentata, namely H. antrorsum, H. quercifolium, H. stenianum, H. vestrogothicum, and H. vetlandaënse are described from the Götaland region (southern Sweden), H. grothii from Norrbotten in the Norrland region (northeast Sweden), and H. sparsifolium var. suppansum Johanss. and H. adampliatum var. pilosius Ohlsén are raised to specific rank as H. suppansum and H. gothiciferum respectively. 相似文献
3.
The flavonoid and phenolic acid pattern of Adenostoma fasciculatum and A. sparsifolium, two dominant, endemic species of the Californian chaparral, was analysed qualitatively and quantitatively. Adenostoma sparsifolium was found to secrete large amounts of lipophilic, unusually substituted flavonoids onto the leaf surface; A. fasciculatum produces five hydrophilic flavonol 3-O-glycosides of kaempferol, quercetin and isorhamnetin. The phenolic acid pattern differed quantitatively but not qualitatively between the species. The amounts of phenolic acids that could be detected within the leaves, leaf litter and soil beneath the shrubs seem too small to explain allelopathic effects as the main reason for the dominance of the two species. 相似文献
4.
Possible tradeoffs between efficiency of water transport and mechanical strength were examined in stems of two congeneric
pairs of co-occurring chaparral shrubs. First, since previously published results indicated that Adenostoma sparsifolium (Rosaceae) had greater specific conductivity (k
s or hydraulic conductivity per xylem transverse area) than A. fasciculatum, it was hypothesized that A. sparsifolium would have greater vessel lumen area per square millimeter of xylem area, and less mechanical strength, than A. fasciculatum. Secondly, since Ceanothus megacarpus (Rhamnaceae) is a non-sprouter (unable to sprout from the root crown following fire or other major disturbance) whereas C. spinosus is a sprouter and thus able to form new stems following disturbance, it was hypothesized that C. megacarpus would have greater mechanical strength, but lower k
s, than C. spinosus. Both hypotheses were supported. Based upon computer-aided image analyses, A. sparsifolum had significantly higher mean and maximum vessel diameters (16.4, 40.5 vs. 14.6, 35.7 μm), a 34% greater percent vessel lumen
area, and a two-fold greater measured and theoretical k
s than A. fasciculatum. This corresponded to 14% lower stem density (wet weight/volume) and less mechanical strength, with a 37% lower modulus of
elasticity (MOE) and a 30% lower modulus of rupture (MOR) than A. fasciculatum. Similarly, C.␣spinosus had a significantly higher maximum vessel diameter (52.7 vs. 41.8 μm) and a 92% higher theoretical k
s (and 43% higher measured k
s) than C. megacarpus. This corresponded to a 9% lower stem density and 20% lower MOR than for C. megacarpus. Thus, at least within these two congeneric pairs of chaparral shrubs growing together in the same habitat, there may be
tradeoffs between mechanical strength and conductive efficiency of the stem xylem which correspond to differences in transport
physiology and life history traits of sprouter versus non-sprouter species. 相似文献
5.
A new flavone 5,6-dimethoxy-3,7,4′-trihydroxyflavone was isolated from the external leaf resin of Adenostoma sparsifolium and identified by spect 相似文献
6.
Soili Stenroos Raquel Pino-Bodas Teuvo Ahti 《Cladistics : the international journal of the Willi Hennig Society》2019,35(5):603-603
A new generic name, Rexiella, is published to replace the recently published name Rexia S. Stenroos, Pino-Bodas and Ahti, which turned out to be an illegitimate later homonym of the cyanobacterial genus Rexia D. A. Casamatta, S. R. Gomez and J. R. Johansen. 相似文献
7.
Xiuguang Mao Vu D. Thong Paul J. J. Bates Gareth Jones Shuyi Zhang Stephen J. Rossiter 《Biological journal of the Linnean Society. Linnean Society of London》2013,110(2):346-361
Phylogenetic discordance among taxa can provide powerful insights into past episodes of introgressive hybridization, as well as lineage sorting. Previously, we showed that the taxonomically distinct taxon Rhinolophus sinicus septentrionalis has undergone historical introgression with its sympatric sister subspecies Rhinolophus sinicus sinicus. To examine in more detail the extent of gene flow between these two taxa, and also between these and their sister species Rhinolophus thomasi, we obtained new samples from China, Myanmar, and Vietnam, and combined new and published genetic data from these, Rhinolophus rouxii, and Rhinolophus indorouxii from India. Phylogenetic analyses revealed three separate cases of discordance: between R. s. septentrionalis and adjacent populations of R. s. sinicus, between R. s. septentrionalis and R. thomasi and between eastern populations of R. s. sinicus and a newly‐identified lineage. In both former cases, the mitochondrial DNA introgression appears to be asymmetric, which is likely to have resulted from mating between R. s. septentrionalis females with smaller R. s. sinicus and R. thomasi males, although we cannot rule out other scenarios completely. Further conflicts between genetic data and accepted species arrangements across the genus, with paraphyly of members of the rouxii‐group, suggest the need for a thorough systematic revision of relationships within this group. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110 , 346–361. 相似文献
8.
Lateral inhibition mediated by Delta/Notch (Dl/N) signaling is used throughout development to limit the number of initially equivalent cells that adopt a particular fate [1], [2] and [3]. Although adjacent cells express both Dl ligand and N receptor, signaling between them ultimately occurs in only one direction. Classically, this has been explained entirely by feedback: activated N can downregulate Dl, amplifying even slight asymmetries in the Dl or N activities of adjacent cells [1], [2], [3], [4] and [5]. Here, however, we present an example of lateral inhibition in which unidirectional signaling depends instead on Dl's ability to inhibit N within the same cell, a phenomenon known as cis-inhibition [6], [7], [8], [9], [10] and [11]. By genetically manipulating individual R1/R6/R7 photoreceptor precursors in the Drosophila eye, we show that loss of Dl-mediated cis-inhibition reverses the direction of lateral signaling. Based on our finding that Dl in R1/R6s requires endocytosis to trans-activate but not to cis-inhibit N, we reexamine previously published data from other examples of lateral inhibition. We conclude that cis-inhibition generally influences the direction of Dl/N signaling and should therefore be included in standard models of lateral inhibition. 相似文献
9.
Cun-Feng Zhao Ran Wei Xian-Chun Zhang 《Cladistics : the international journal of the Willi Hennig Society》2020,36(4):443-445
Here, we publish Lepisorus sect. Paragramma (Blume) C.F. Zhao, R. Wei & X.C. Zhang as a combinatio nova to replace the section name in Zhao et al. (2020), which was published as a status nova and turned out to be an invalid name, because we cited an incorrect basionym. A revised infrageneric classification of Lepisorus also is proposed. 相似文献
10.
Margareta Proksch Peter Proksch Gottfried Weissenboeck Eloy Rodriguez 《Phytochemistry》1982,21(7):1835-1836
Four flavonoids were identified from the external leaf extract of Adenostoma sparsifolium: the two new flavones 3, 7-dihydroxy-5, 6-dimethoxyflavone and 3, 5, 7-trihydroxy-8-methoxyflavone and the known compounds galangin and pinocembrin. 相似文献
11.
Morphological and Molecular Diversity of the Neglected Genus Rhizomastix Alexeieff, 1911 (Amoebozoa: Archamoebae) with Description of Five New Species
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Eliška Zadrobílková Pavla Smejkalová Giselle Walker Ivan Čepička 《The Journal of eukaryotic microbiology》2016,63(2):181-197
The genus Rhizomastix is a poorly known group of amoeboid heterotrophic flagellates living as intestinal commensals of insects, amphibians or reptiles, and as inhabitants of organic freshwater sediments. Eleven Rhizomastix species have been described so far, but DNA sequences from only a single species have been published. Recently, phylogenetic analyses confirmed a previous hypothesis that the genus belongs to the Archamoebae; however, its exact position therein remains unclear. In this study we cultured nine strains of Rhizomastix, both endobiotic and free‐living. According to their light‐microscopic morphology and SSU rRNA and actin gene analyses, the strains represent five species, of which four are newly described here: R. bicoronata sp. nov., R. elongata sp. nov., R. vacuolata sp. nov. and R. varia sp. nov. In addition, R. tipulae sp. nov., living in the intestine of crane flies, is separated from the type species, R. gracilis. We also examined the ultrastructure of R. elongata sp. nov., which revealed that it is more complicated than the previously described R. libera. Our data show that either the endobiotic lifestyle of some Rhizomastix species has arisen independently from other endobiotic archamoebae, or the free‐living members of this genus represent a secondary switch from the endobiotic lifestyle. 相似文献
12.
The P-group plasmids RP1, RP4, RK2, R68 and R68.45 were analyzed by the following restriction endonucleases:BamHI,BglII,EcoRI,HindIII,PstI,PvuII,SalI, andSmaI. No differences between RP1, RP4, and RK2 were found, and the plasmid R68.45 was found to contain a direct duplication of an existing DNA sequence in R68. Our map of RK2 differs from the published map of RK2 in the corresponding region of the R68 map that is duplicated in R68.45. 相似文献
13.
M. L. Levin L. Killmaster G. Zemtsova D. Grant K. Y. Mumcuoglu M. E. Eremeeva G. A. Dasch 《Experimental & applied acarology》2009,49(4):347-359
Rickettsia conorii, the etiologic agent of Mediterranean spotted fever is widely distributed in Southern Europe, the Middle East, Africa, India
and the Caspian region. In the Mediterranean region, the brown dog tick, Rhipicephalus sanguineus, is the recognized vector of R. conorii. To study tick-pathogen relationships and pathogenesis of infection caused in model animals by the bite of an infected tick,
we attempted to establish a laboratory colony of Rh. sanguineus persistently infected with R. conorii. Rhipicephalus sanguineus ticks of North American and Mediterranean origin were exposed to R. conorii isolates of African (R. conorii conorii strain Malish) and Mediterranean (R. conorii israelensis strain ISTT) origin. Feeding of ticks upon infected mice and dogs, intra-hemocoel inoculation, and submersion in suspensions
of purified rickettsiae were used to introduce the pathogen into uninfected ticks. Feeding success, molting success and the
longevity of molted ticks were measured to assess the effects of R. conorii on the survival of Rh. sanguineus. In concordance with previously published results, Rh. sanguineus larvae and nymphs from both North American and Mediterranean colonies exposed to R. conorii conorii Malish experienced high mortality during feeding and molting or immediately after. The prevalence of infection in surviving
ticks did not exceed 5%. On the other hand, exposure to ISTT strain had lesser effect on tick survival and resulted in 35–66%
prevalence of infection. Rh. sanguineus of Mediterranean origin were more susceptible to infection with either strain of R. conorii than those from North America. Previous experimental studies had demonstrated transovarial and transstadial transmission
of R. conorii in Rh. sanguineus; however, our data suggest that different strains of R. conorii may employ different means of maintenance in nature. The vertebrate host may be a more important reservoir than previously
thought, or co-feeding transmission between different generations of ticks may obviate or lessen the requirement for transovarial
maintenance of R. conorii. 相似文献
14.
丹霞柿,广东柿属(柿科)一新组合及其一新异名 总被引:1,自引:0,他引:1
通过查阅模式标本后发现丹霞南烛(Lyonia danxiaensis R. H. MiaoW. Q. Liu)具有聚伞花序,花部为4数,雄蕊16枚且成对着生,花丝非膝曲状等特征与珍珠花属(Lyonia)不符,而与柿科(Ebenaceae)柿属(Diospyros)一致,因此提出一新组合:丹霞柿[Diospyros danxiaensis (R. H. MiaoW. Q. Liu) Y. H. TongN. H. Xia]。且经标本比对后发现,新近发表的彭华柿(Diospyros penghuae W. B. Liao, Q. FanW. Y. Zhao)与丹霞柿实为同种,在此也予以合并。 相似文献
15.
Nodulation of Alnus rubra seedlings after inoculation with soil from under A. rubra, Betula papyrifera. Rubus lacianutus, R. spectabilis, and R.ursinus on 2 recently harvested sites was compared. Nodulation capacity was low compared to other published reports, ranging from 0 to 18.9 infective units cm-3 of soil and was significantly affected by the site and plant species. Nodulation capacity of soil under alder was significantly higher than under all other species except R. spectabilis, regardless of site. The lowest nodulation capacity was found in soil under B. papyrifera.Joint appointment with Dept. of Soil Science, Faculty of Agricultural Sciences 相似文献
16.
Cellulose acetate electrophoresis (CAE) was used to investigate enzyme polymorphism in two congeneric species of Acaridae,
Rhizoglyphus robini and R. echinopus. Using homogenates of individual mites, 27 enzymes were examined in two buffers. Five enzymes showed interspecific polymorphism,
15 exhibited intraspecific variation inR.robini and 12 in R.echinopus. Polymorphic PGDH was used to analyse paternity in progeny of R.robini females that had mated with two males. The second male sired on average 67% of progeny. Enzyme polymorphism can be used to
study poorly known aspects of acarid mites biology, such as their mating systems and population structure under natural conditions
and in stored foods.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
Tropaeolum austropurpureum (J.M. Watson & A.R. Flores) J.M. Watson & A.R. Flores, stat. nov., based on Tropaeolum hookerianum Barnéoud subsp. austropurpureum J.M. Watson & A.R. Flores, is described, and the new rank is published. Details of the discovery, ecology, and possible evolution of this species are discussed. Instructions for its cultivation are given. 相似文献
18.
Partial phase diagrams are of considerable utility in the development of optimized cryobiological procedures. Recent theoretical predictions of the melting points of ternary solutions of interest to cryobiology have caused us to re-examine measurements that our group made for the ethylene-glycol–sodium chloride–water phase diagram. Here we revisit our previous experiments by measuring melting points at five ethylene-glycol to sodium chloride ratios (R values; R = 5, 10, 15, 30, and 45) and five levels of concentration for each ratio. Melting points were averaged from three measurements and plotted as a function of total solute concentration for each R value studied. The new measurements differed from our original experimental values and agreed with predicted values from both theoretical models. Additionally, the data were fit to the polynomial described in our previous report and the resulting equation was obtained:Tm=(38.3-2.145×10-1R)w+(81.19-2.909×10-1R)w2,where w is the total solute mass fraction. This new equation provided good fits to the experimental data as well as published values and relates the determined polynomial constants to the R value of the corresponding isopleths of the three dimensional phase diagram, allowing the liquidus curve for any R value to be obtained. 相似文献
19.
Sebastiaan W. Rampen Stefan Schouten F. Elda Panoto Maaike Brink Robert A. Andersen Gerard Muyzer Ben Abbas Jaap S. Sinninghe Damsté 《Journal of phycology》2009,45(2):444-453
The phylogenetic position of diatoms belonging to the genus Attheya is presently under debate. Species belonging to this genus have been placed in the subclasses Chaetocerotophycidae and Biddulphiophycidae, but published phylogenetic trees based on 18S rDNA, morphology, and sexual reproduction indicate that this group of diatoms may be a sister group of the pennates. To clarify the position of Attheya, we studied the morphology, 18S rDNA, 16S rDNA of the chloroplasts, the rbcL large subunit (LSU) sequences of the chloroplasts, and the sterol composition of three different strains of Attheya septentrionalis (Østrup) R. M. Crawford and one strain of Attheya longicornis R. M. Crawford et C. Gardner. These data were compared with data from more than 100 other diatom species, covering the whole phylogenetic tree, with special emphasis on species belonging to the genera that have been suggested to be related to the genus Attheya. All data suggest that the investigated Attheya species form a separate group of diatoms, and there is no indication that they belong to either the Chaetocerotophycidae or the Biddulphiophycidae. Despite applying these various approaches, we were unable to determine the exact phylogenetic position of the investigated Attheya species within the diatoms. 相似文献
20.
A previously published DNA barcode survey of red macroalgae in Australia revealed significant cryptic and overlooked diversity for the genus Rhodymenia with recognition of R. novahollandica, R. prolificans, R. stenoglossa, R. wilsonis and an additional four uncharacterized genetic species groups. Since that study, increased sampling effort in Australia has warranted reassessment and reinvestigation of the number of genetic species groups attributed to Rhodymenia and their respective taxonomic affiliations. Using molecular-assisted alpha taxonomy employing the DNA barcode (COI-5P), the present study resolved 188 Australian specimens in 12 genetic species groups assignable to the genus Rhodymenia. Four of these groups were attributed to the previously recognized species (above), whereas some collections from Lord Howe Island were attributed to the New Zealand species R. novazelandica, expanding its biogeographic range. The following seven genetic groups were inconsistent with existing species of Rhodymenia and established as novel taxa: R. compressa sp. nov., R. contortuplicata sp. nov., R. gladiata sp. nov., R. insularis sp. nov., R. lociperonica sp. nov., R. norfolkensis sp. nov. and R. womersleyi sp. nov. Although morphological and biogeographic features were adequate for distinguishing some species of Rhodymenia from Australia, DNA sequencing in combination with morphology and biogeography provided the most reliable means of identification. 相似文献