Introgressive hybridization in two southern California species of Rhus (Anacardiaceae)

Five populations ofRhus integrifolia andR. ovata were studied and, based upon morphological characteristics and pollen viability, a number of putative hybrids were found in those areas where the two species are sympatric. Diagnostic characteristics most useful for distinguishing the species and their hybrids are leaf morphology, sepal pubescence, petiole length, and petal size. Introgression was evident in at least three populations, which suggested that hybridization between the two species is an ancient phenomenon. Evolutionarily, hybridization between the two taxa has probably been of little consequence.     

Mechanisms for tolerating freeze-thaw stress of two evergreen chaparral species: Rhus ovata and Malosma laurina (Anacardiaceae)

The response to freeze-thaw stress was examined for two co-occurring evergreen species, Malosma laurina and Rhus ovata. Laboratory and field experiments on adults and seedlings were made in the spring and winter in 1996 and again on adults in 2003 and 2004. Laboratory and field results indicated that the stem xylem for adults of M. laurina and R. ovata were similarly susceptible to freezing-induced cavitation (percentage loss of conductivity = 92 ± 2.6% for R. ovata and 90 ± 4.2% for M. laurina at ≤ -6°C). In contrast, leaves of M. laurina were more susceptible to freezing injury than leaves of R. ovata. Among seedlings in the field, leaves of M. laurina exhibited freezing injury at -4°C and total shoot mortality at -7.2°C, whereas co-occurring seedlings of R. ovata were uninjured. Surprisingly, R. ovata tolerates high levels of freezing-induced xylem embolism in the field, an apparently rare condition among evergreen plants. Rhus ovata avoids desiccation when xylem embolism is high by exhibiting low minimum leaf conductance compared to M. laurina. These results suggest a link between minimum leaf conductance and stem hydraulics as a mechanism permitting the persistence of an evergreen leaf habit in freezing environments.     

Anatomy of two mechanisms of breaking physical dormancy by experimental treatments in seeds of two North American Rhus species (Anacardiaceae)

Anatomy of the endocarp was studied in relation to the physical dormancy-breaking mechanisms in experimentally treated Rhus aromatica var. aromatica and R. glabra germination units, which include seed plus endocarp (hereafter seeds). The endocarp has three distinct layers, with brachysclereids on the outside, osteosclereids in the middle, and macrosclereids on the inside. Brachysclereids in the carpellary micropyle region (i.e., region immediately adjacent to the integumentary micropyle) are shorter than those in other parts of the endocarp, and the macrosclereids in this region are not elongated. Thus, a weak point is formed in the endocarp. Concentrated sulfuric acid broke seed dormancy in R. aromatica by eroding the brachysclereids and osteosclereids in the carpellary micropyle region, whereas boiling water broke dormancy in seeds of R. glabra by inducing a blister adjacent to the carpellary micropyle.     

The Ericoideae and the southern African heathers

OLIVER, E. G. H., 1989. The Ericoideae and the southern African heathers. The subfamily Ericoideae (Ericaceae) containing the true heathers and heaths has been a group long recognized as a sound natural entity. With work on the southern African genera and species which comprise approximately 95% of the subfamily well in progress, a reassessment of the number of genera has become necessary because of the considerable variation recorded in, and the postulated polyphyletic origin of, the capsular genera. Changes envisaged will affect the whole concept of the heaths within Africa. The genus Philippia Klotzsch has been reduced to synonymy under Erica L. and it is shown that the case for a similar action is very strong for Blaeria L. and Ericinella Klotzsch. The position of the monotypic European genus, Bruckenthalia Reichb., is also affected but remains unresolved.     

Microsatellite loci for two East African tree species, Leptonychia usambarensis (Sterculiaceae) and Sorindeia madagascariensis (Anacardiaceae)

We isolated 20 trinucleotide microsatellites from two African tree species: Sorindeia madagascariensis (nine microsatellites) and Leptonychia usambarensis (11 microsatellites). Number of alleles ranged from three to seven in Sorindeia and two to 10 in Leptonychia. Observed heterozygosity ranged from 0.025 to 0.829 for Sorindeia and from 0.226 to 0.933 for Leptonychia. Two loci from each species departed from Hardy-Weinberg equilibrium. These microsatellite markers will be used to study how forest fragmentation affects pollination and seed dispersal processes of these tree species.     

A new species of the genus Hydrodroma Koch, 1837 (Acari, Hydrachnidia, Hydrodromidae), with a key to the hitherto known six species of the genus in Australia

The genus Hydrodroma Koch, 1837 in Australia consists of six species, the newly described Hydrodroma meridionalissp. n. included. The new species is described from 45 sampling sites from running waters in Queensland, Victoria, New Southern Wales, Western Australia, Northern Territory and South Australia. Furthermore, a key for the identification of species of Hydrodroma occurring in Australia is given.     

Metabolic adaptations to hypoxia of two species of polychaeta,Nephtys ciliata and Nephtys hombergii

Summary The respiratory responses to declining oxygen tension in Nephtys ciliata and N. hombergii were investigated using flow respirometry. N. hombergii showed a better regulation of oxygen uptake during declining oxygen tension than N. ciliata. N. ciliata showed no difference in regulatory ability when individuals of different sizes were compared. It is argued that the difference in regulating ability can partly explain the distribution pattern of these two species in Århus Bight, Denmark.Abbreviations B2 regulation index - B2 mean regulation index - C_eO2 excurrent oxygen concentration - C_iO2 incurrent oxygen concentration; dw dry weight - PO₂ partial pressure (oxygen) - VO₂ oxygen uptake - VO₂ relative oxygen uptake - V_W water flow     

Phylogenetic and biogeographic diversification of Rhus (Anacardiaceae) in the Northern Hemisphere

Sequences of internal transcribed spacers (ITS) of nuclear ribosomal DNA, the chloroplast ndhF gene, and chloroplast trnL-F regions (trnL intron, and trnL [UAA] 3' exon-trnF [GAA] intergenic spacer) were used for phylogenetic analyses of Rhus, a genus disjunctly distributed in Asia, Europe, Hawaii, North America, and Northern Central America. Both ITS and cpDNA data sets support the monophyly of Rhus. The monophyly of subgenus Rhus was suggested by the combined cpDNA and ITS data, and largely supported in the cpDNA data except that Rhus microphylla of subgenus Lobadium was nested within it. The monophyly of subgenus Lobadium was strongly supported in the ITS data, whereas the cpDNA data revealed two main clades within the subgenus, which formed a trichotomy with the clade of subgenus Rhus plus R. microphylla. The ITS and cpDNA trees differ in the positions of Rhus michauxii, R. microphylla, and Rhus rubifolia, and hybridization may have caused this discordance. Fossil evidence indicates that Rhus dates back to the early Eocene. The penalized likelihood method was used to estimate divergence times, with fossils of Rhus subgenus Lobadium, Pistacia and Toxicodendron used for age constraints. Rhus diverged from its closest relative at 49.1+/-2.1 million years ago (Ma), the split of subgenus Lobadium and subgenus Rhus was at 38.1+/-3.0 Ma. Rhus most likely migrated from North America into Asia via the Bering Land Bridge during the Late Eocene (33.8+/-3.1 Ma). Rhus coriaria from southern Europe and western Asia diverged from its relatives in eastern Asia at 24.4+/-3.2 Ma. The Hawaiian Rhus sandwicensis diverged from the Asian Rhus chinensis at 13.5+/-3.0 Ma. Subgenus Lobadium was inferred to be of North American origin. Taxa of subgenus Lobadium then migrated southward to Central America. Furthermore, we herein make the following three nomenclatural combinations: (1) Searsia leptodictya (Diels) T. S. Yi, A. J. Miller and J. Wen, comb. nov., (2) Searsia pyroides (A. Rich.) T. S. Yi, A. J. Miller and J. Wen, comb. nov., and (3) Searsia undulata (Jacq.) T. S. Yi, A. J. Miller and J. Wen, because our analyses support the segregation of Searsia from Rhus.     

African species of Chionanthus L.(Oleaceae) hitherto included in Linociera Swartz

Chionanthus L.(1753) and Linociera Swartz (1791) being considered congeneric.nine continental African species and three Madagascan species hitherto included in Linociera are transferred to Chionanthus .Synonymy, concise statements of distribution and a key are provided. Chionanthus richardsiae is a new species from Zambia; a biographical note on its collector, Mary Richards (1885–1977), is included.     

Genetic variation and evidence of hybridization in the genus Rhus (Anacardiaceae)

Rhus michauxii, a rare plant species endemic to the southeastern United States, was previously known only from central North Carolina and one site in Georgia. An additional site, which is now believed to represent the largest known concentration of R. michauxii, was recently discovered at Ft. Pickett near Blackstone, Virginia. Morphological characteristics in several of the Ft. Pickett Rhus populations appear to be intermediate between R. michauxii and the widespread R. glabra, a closely related congener that co-occurs at Ft. Pickett. Although morphological evidence of hybridization between R. michauxii and R. glabra in North Carolina has been provided previously, genetic marker data are lacking. In the present study we examined levels of allozyme variation at 11 polymorphic loci within and among seven populations of R. michauxii, one population of R. glabra, and four putative hybrid populations at Ft. Pickett. Overall, R. michauxii had typical levels of within-population genetic variation when compared to other species with similar life-history characteristics. In contrast, the proportion of genetic variation among populations (G(ST)) was considerably lower than expected. Finally, R. michauxii and R. glabra appear to have a fixed allelic difference at the Idh2 locus. This enabled us to confirm hybridization in all four of the putative hybrid populations and one of the R. michauxii populations.     

Comparative morphology and physiology of fruit and seed development in the two shrubs Rhus aromatica and R. glabra (Anacardiaceae)

Morphology and physiology of fruit and seed development were compared in Rhus aromatica and R. glabra (Anacardiaceae), both of which produce drupes with water-impermeable endocarps. Phenology of flowering/fruiting of the two species at the study site was separated by ∼2 mo. However, they were similar in the timetable and pattern of fruit and seed development; it took ∼2 mo and ∼1.5 mo for flowers of Rhus aromatica and R. glabra, respectively, to develop into mature drupes. The single sigmoidal growth curve for increase in fruit size and in dry mass of these two species differs from the double-sigmoidal one described for typical commercial drupes such as peach and plum. Order of attainment of maximum size was fruit and endocarp (same time), seed coat, and embryo. By the time fruits turned red, the embryo had reached full size and become germinable; moisture content of seed plus endocarp had decreased to ∼40%. The endocarp was the last fruit component to reach physiological maturity, which coincided with development of its impermeability and a seed plus endocarp moisture content of <10%. At this time, ∼50, 37, and 13% of the dry mass of the drupe was allocated to the exocarp plus mesocarp unit, endocarp, and seed, respectively. The time course of fruit and seed development in these two species is much faster than that reported for other Anacardiaceae, including Rhus lancea, Protorhus, and Pistacia.     

Floral structure and evolution in the Anacardiaceae

WANNAN, B. S. & QUINN, C. J, 1991. Floral structure and evolution in the Anacardiaceae. Carpel morphology and anatomy is investigated in 17 genera and carpellode morphology in 12 genera. There is an evolutionary sequence in the family from poorly differentiated, nearly apocarpous gynoecia towards syncarpous gynoecia with clearly defined stigmata, styles and ovaries. There has also been marked reduction culminating in pseudomonomery. The carpellodes of the male flowers appear more conservative, and provide evidence of affinities between genera with quite different fertile gynoecia. The characters have been polarized using Burseraceae as a sister group. Data from these sources, as well as from pericarp anatomy, wood anatomy and biflavonoid content indicate that the long standing intrafamilial classification into five tribes is artificial, and that the two small satellite families, Blepharocaryaceae and Julianiaceae should be included in the family. A large monophyletic group is recognized comprised of essentially four of the existing tribes (Anacardiëae, Dobineëae, Semecarpeae, Rhoëae), as well as the two satellite families. This group incorporates two subgroups of more closely allied genera. The remaining genera (mostly Spondiadeae) are very diverse, and for the present are placed in an artificial group characterised by a set of plesiomorphs. Relationships within this group must be resolved before a satisfactory taxonomy of the family can be achieved.     

A revision of Ifloga in southern Africa, with comments on the northern hemisphere species

Ifloga in southern Africa is revised and comments are offered on the northern hemisphere species, I. spicata (together with I. rueppellii ) and I. obovata. Twelve species are recognized in southern Africa, two being described as new. Two natural groups, based on floral characters, are recognized and the rank of subgenus is proposed for these. Ifloga spicata, I. obovata, I. glomerata, I. anomala, I. thellungiana and I. molluginoides constitute subgenus Ifloga; I. verticillata, I. polycnemoides, I. paronychioides, I. Candida, I. ambigua, I. repens, I. pilulifera, I. decumbens , subgenus Trichogyne. A key to the species is provided. The morphology and phytogeography of the genus are discussed.     

Taxonomy and variation of Vulpia ciliata Dumort.

The arguments lor the conspecificity of the tetraploid taxa in Vulpia section Vulpia sensu Cotton & Stace are discussed.     

Inflorescence structure and affinities of Laurophyllus (Anacardiaceae)

WANNAN, B. S. & QUINN, C. J., 1992. Inflorescence structure and affinities of Laurophyllus (Anacardiaceae). The inflorescence structure, pollen and floral anatomy are investigated in Laurophyllus . The inflorescence is a panicle sensu Briggs & Johnson, but with marked differences between the male and female. Sistergroup comparison with the Burseraceae indicates that the plesiomorphic inflorescence in the Anacardiaceae is a thyrsoid, the apomorph being the panicle. Laurophyllus has Rhus -type pollen and therefore has no close affinity with Dobinea or Campylopeialum . Floral anatomy reveals that Laurophyllus is unicarpellary with a dorsally attached style and an apically attached ovule. These characters suggest that rather than being related to Anacardium or Mangifera , it has some affinity with Blepharocarya or perhaps with one of the poorly known African or Madagascan genera.     

Review of the Chinese species of the genus Varma Distant (Hemiptera,Fulgoromorpha, Tropiduchidae), with description of two new species

Two new species of Varma Distant, 1906, V. falcata Chang & Chen, sp. n. (China: Guizhou) and V. lobata Chang & Chen, sp. n. (China: Guizhou) are described and illustrated. The female genitalia of four speices including two known species are described and illustrated for the first time. The diagnostic characters of this genus are redefined. A checklist to the species of Varma in China is given. The Keys on male and female genitalia to the Chinese species of Varma are provided.     

Seasonal conductivity and embolism in the roots and stems of two clonal ring-porous trees, Sassafras albidum (Lauraceae) and Rhus typhina (Anacardiaceae)

Seasonal xylem (wood) conductivity and embolism (air blockage) patterns were monitored in roots vs. stems of two clonal ring-porous tree species, Sassafras albidum and Rhus typhina, throughout 1996 and 1997. Stems of both species were 100% embolized in the early spring and became conductive by late June following leaf expansion and maturation of new earlywood vessels. Dyes indicated the stem conduction was restricted almost exclusively to the current year's growth ring. Stems became totally embolized again by early October, before the first freezing temperatures. In contrast, woody roots of both species maintained low embolism values, many conductive growth rings, and high conductivity values regardless of the season. No positive root pressures were detected in either species. The mean frost depth (204 ± 11 mm) was deeper than all sampled roots of Rhus and 47% of sampled roots of Sassafras. The roots that had been in frozen soil either avoided embolism altogether or they were able to reverse embolism by a mechanism other than positive root pressures.