Patterns of hybrid formation among cryptic species of bird‐nest fern,Asplenium nidus complex (Aspleniaceae), in West Malesia

In order to clarify patterns of hybrid formation in the Asplenium nidus complex, artificial crossing experiments were performed between individuals of genetically differentiated groups based on the sequence of the rbcL gene, including A. australasicum from New Caledonia, A. setoi from Japan and several cryptic species in the A. nidus complex. No hybrid plants were obtained in crosses between nine of the 16 pairs. Even for pairs that generated hybrids, the frequency of hybrid formation was lower than expected given random mating, or only one group was able to act as the maternal parent, when the genetic distance (Kimura's two parameter) between parental individuals was at least 0.006. Sterile hybrids were produced by three pairs that were distantly related but capable of forming hybrids. Considering the results of the crosses together with the genetic distance between the parental individuals, it seems that the frequency of hybrid formation decreases rapidly with increasing divergence. The frequency of hybrid formation has not been previously examined in homosporous ferns, but it seems that a low frequency of hybrid formation can function as an important mechanism of reproductive isolation between closely related pairs of species in the A. nidus complex in addition to hybrid sterility. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 160 , 42–63.     

Effects of forestry on the thermal habitat of Dolly Varden (<Emphasis Type="Italic">Salvelinus malma</Emphasis>)

Forestry activities in riparian areas are known to affect stream communities considerably. Not only do riparian deforestation resulting from agriculture or urbanization developments affect stream communities but extensive commercial plantation and forestry practices can alter stream environments adjacent to remaining, intact or secondary forests. Because forestry often includes the construction of logging roads through the riparian zone, this can directly degrade stream environments. Twelve streams in the Shiretoko Peninsula, Hokkaido were investigated so as to determine the effects of forestry practices on stream temperature, periphyton biomass, grazer (benthic invertebrates) biomass and Dolly Varden (Salvelinus malma Walbaum) biomass. The greater the proportion of planted area in the catchment, the higher the stream temperature. Stream temperature directly affects periphyton biomass and Dolly Varden biomass negatively. Neither stream temperature nor periphyton biomass predicted grazer biomass, whereas a positive correlation was found between grazer biomass and Dolly Varden biomass that forage on invertebrates. The overall results indicated that Dolly Varden in the Shiretoko streams were negatively affected by forestry practices and the resultant stream temperature increases. Without effective future riparian forest management, the complex effects of both riparian disturbance and ongoing global warming could further reduce Dolly Varden populations in the region.     

The Differentiation of Contact Cells and Isolation Cells in the Xylem Ray Parenchyma of Populus maximowiczii

A histochemical analysis was made of the differentiation ofcontact cells and isolation cells in the xylem ray parenchymaof Populus maximowiczii. The contact cells formed secondarywalls at approximately the same time as adjoining vessel elements.The lignification of the cell walls of contact cells and vesselelements began earlier than that of wood fibres and isolationcells. Thus, the formation of the secondary wall, includinglignification, of the contact cells might occur at the sametime as that of the vessel elements to which they are directlyconnected. By contrast, the isolation cells began to form secondarywalls later than the vessel elements and wood fibres in thevicinity of the isolation cells. After the deposition of thesecondary wall, a protective layer was formed in contact cellsbut no isotropic layer was observed in isolation cells. Theresults suggest the importance of vessel elements in the determinationof the differentiation of adjoining ray parenchyma cells.Copyright1999 Annals of Botany Company Contact cell, isolation cell, vessel element, xylem differentiation, Populus maximowiczii Henry.     

Patterns of host utilisation by herbivore assemblages of the genus Caloptilia (Lepidoptera; Gracillariidae) on congeneric maple tree (Acer) species

1. The pattern of host utilisation by congeneric Caloptilia caterpillars on 14 different species of Acer (maple) was investigated in temperate mixed forests of central Japan. A multi‐filtering model of host plant utilisation was proposed to address how phylogenetically related herbivore assemblages are constructed on phylogenetically related host plant species. 2. Two hypotheses were examined. The first questioned whether a negative relationship exists between the phylogenetic distance of plants from the most suitable host species and the abundance of herbivorous insects on the host. Regarding the second, it was investigated whether the assemblage dissimilarity of herbivorous insects among host plant species increases with increasing distance of plant phylogeny and traits. 3. Mantel and partial Mantel tests were used to measure the relationship between assemblage dissimilarity of Caloptilia species and the distance of plant phylogeny and leaf traits. 4. Both hypotheses were confirmed, clearly suggesting that the utilisation and suitability of hosts for Caloptilia caterpillars were strongly influenced by phylogenetic relatedness and leaf trait similarity among Acer species. This implies that phylogenetic distance is an integrated measure of phenotypic and ecological attributes of congeneric Acer species that can be used to explain specialisation and constraints of host utilisation of congeneric herbivore species even on a short evolutionary timescale.     

LOCALIZATION OF LIGHT-INDUCED STRONTIUM ACCUMULATION IN SPINACH CHLOROPLASTS

Electron-microscopic evidence showing the location of strontiumand calcium deposits on the lamellae of spinach chloroplastsis presented. The chloroplast limiting membrane did not actas a barrier for this ion accumulation, since the chloroplastswere ruptured during the isolation and incubation, especiallyin the light. The grana stacks also were extensively swollen.The number of electrondense deposits attached on the lamellaewas greatly increased by light under conditions favoring thehydrolysis of ATP. The average diameter of the deposits aftera 6 minute illumination with 1 mM SrCl₂ was 14 mµ, after15 minutes with 1 mM SrCl₂ was 21 mµ, and after 15 minuteswith 20 µM SrCl₂ was 13 mµ. The findings are inharmony with the results of ion-uptake experiments using radioactivestrontium and calcium. ¹ United States National Science Foundation Postdoctoral Fellow.     

Histogenesis of the Os Penis and Os Clitoridis in Rats

The development of the os penis in normal male rats and the os clitoridis in the females treated with testosterone were studied histologically and histochemically. Alcian blue-positive materials, alkaline phosphatase activities and calcium deposit were detected. The os penis of the rats was composed of a proximal segment and a distal one. The proximal segment of the os penis was formed by the fusion of a membrane bone in its distal half and an ossifying hyaline cartilage in its proximal half. The distal segment of the os penis developed as a fibrocartilage bone.
Two steps were demonstrated in the development of the os penis: the formation of the rudiments, and the differentiation of the proximal and distal segments. The treatment of newborn females with testosterone induced an os clitoridis homologous to the proximal segment of the os penis. The development of the os clitoridis was compared with that of the os penis.