Diversification in a fluctuating island setting: rapid radiation of Ohomopterus ground beetles in the Japanese Islands

The Japanese Islands have been largely isolated from the East Asian mainland since the Early Pleistocene, allowing the diversification of endemic lineages. Here, we explore speciation rates and historical biogeography of the ground beetles of the subgenus Ohomopterus (genus Carabus) based on nuclear and mitochondrial gene sequences. Ohomopterus diverged into 15 species during the Pleistocene. The speciation rate was 1.92 Ma(-1) and was particularly fast (2.37 Ma(-1)) in a group with highly divergent genitalia. Speciation occurred almost solely within Honshu, the largest island with complex geography. Species diversity is highest in central Honshu, where closely related species occur parapatrically and different-sized species co-occur. Range expansion of some species in the past has resulted in such species assemblages. Introgressive hybridization, at least for mitochondrial DNA, has occurred repeatedly between species in contact, but has not greatly disturbed species distinctness. Small-island populations of some species were separated from main-island populations only after the last glacial (or the last interglacial) period, indicating that island isolation had little role in speciation. Thus, the speciation and formation of the Ohomopterus assemblage occurred despite frequent opportunities for secondary contact and hybridization and the lack of persistent isolation. This radiation was achieved without substantial ecological differentiation, but with marked differentiation in mechanical agents of reproductive isolation (body size and genital morphology).     

Different properties of SEK1 and MKK7 in dual phosphorylation of stress-induced activated protein kinase SAPK/JNK in embryonic stem cells

Stress-activated protein kinase/c-Jun NH(2)-terminal kinase (SAPK/JNK), belonging to the mitogen-activated protein kinase family, plays an important role in stress signaling. SAPK/JNK activation requires the phosphorylation of both Thr and Tyr residues in its Thr-Pro-Tyr motif, and SEK1 and MKK7 have been identified as the dual specificity kinases. In this study, we generated mkk7(-/-) mouse embryonic stem (ES) cells in addition to sek1(-/-) cells and compared the two kinases in terms of the activation and phosphorylation of JNK. Although SAPK/JNK activation by various stress signals was markedly impaired in both sek1(-/-) and mkk7(-/-) ES cells, there were striking differences in the dual phosphorylation profile. The severe impairment observed in mkk7(-/-) cells was accompanied by a loss of the Thr phosphorylation of JNK without marked reduction in its Tyr-phosphorylated level. On the other hand, Thr phosphorylation of JNK in sek1(-/-) cells was also attenuated in addition to a decreased level of its Tyr phosphorylation. Analysis in human embryonic kidney 293T cells transfected with a kinase-dead SEK1 or a Thr-Pro-Phe mutant of JNK1 revealed that SEK1-induced Tyr phosphorylation of JNK1 was followed by additional Thr phosphorylation by MKK7. Furthermore, SEK1 but not MKK7 was capable of binding to JNK1 in 293T cells. These results indicate that the Tyr and Thr residues of SAPK/JNK are sequentially phosphorylated by SEK1 and MKK7, respectively, in the stress-stimulated ES cells.     

Changes in the cellular localization of cytosolic glutamine synthetase protein in vascular bundles of rice leaves at various stages of development

Cellular localization of cytosolic glutamine synthetase (GS1; EC 6.3.1.2) in vascular bundles of leaf blades of rice (Oryza sativa L.), at the stage at which leaf blades 6 (the lowest position) to 10 were fully expanded, was investigated immunocytologically with an affinity-purified anti-GS1 immunoglobulin G. Strong signals for GS1 protein were detected in companion cells of large vascular bundles when blades 6–8 were tested. Signals for GS1 were also observed in vascular-parenchyma cells of both large and small vascular bundles. The results further support our hypothesis that GS1 is important for the export of leaf nitrogen from senescing leaves. The signals in companion cells were less striking in the younger green leaves and were hardly detected in the non-green portion of the 11th blade. In the non-green blades, strong signals for GS1 protein were detected in sclerenchyma and xylemparenchyma cells. When total GS extracts prepared from the 6th,10th, and the non-green 11th blades were subjected to anion-exchange chromatography, the activity of GS1 was clearly separated from that of chloroplastic GS, indicating that GS1 proteins detected in the vascular tissues were able to synthesize glutamine. The function of GS1 detected in the developing leaves is discussed.Abbreviations Fd-GOGAT ferredoxin-dependent glutamate synthase - GS1 cytosolic glutamine synthetase - GS2 plastidic glutamine synthetase - IgG immunoglobulin G     

Contrasting effects of habitat discontinuity on three closely related fungivorous beetle species with diverging host‐use patterns and dispersal ability

Understanding how landscape structure influences biodiversity patterns and ecological processes are essential in ecological research and conservation practices. Forest discontinuity is a primary driver affecting the population persistence and genetic structure of forest‐dwelling species. However, the actual impacts on populations are highly species‐specific. In this study, we tested whether dispersal capability and host specialization are associated with susceptibility to forest discontinuity using three closely related, sympatric fungivorous ciid beetle species (two host specialists, Octotemnus assimilis and O. crassus; one host generalist, O. kawanabei). Landscape genetic analyses and the estimation of effective migration surfaces (EEMS) method consistently demonstrated contrasting differences in the relationships between genetic structure and configuration of forest land cover. Octotemnus assimilis, one of the specialists with a presumably higher dispersal capability due to lower wing loading, lacked a definite spatial genetic structure in our study landscape. The remaining two species showed clear spatial genetic structure, but the results of landscape genetic analyses differed between the two species: while landscape resistance appeared to describe the spatial genetic structure of the specialist O. crassus, genetic differentiation of the generalist O. kawanabei was explained by geographic distance alone. This finding is consistent with the prediction that nonforest areas act more strongly as barriers between specialist populations. Our results suggest that differences in host range can influence the species‐specific resistance to habitat discontinuity among closely related species inhabiting the same landscape.     

Monoclonal Antibodies with Affinity to Self-Complementary Left-Handed DNA Containing Cyclonucleosides with High Anti Conformation

Abstract

Monoclonal antibodies specific for a self-complementary hexanucleotide with a high-anti conformation were found to bind another hexanucleotide with a high-anti conformation, but with a different sequence. A higher order structure seemed to be recognized in the reaction.     

Multiple speciation events in an arthropod with divergent evolution in sexual morphology

Sexual selection can facilitate divergent evolution of traits related to mating and consequently promote speciation. Theoretically, independent operation of sexual selection in different populations can lead to divergence of sexual traits among populations and result in allopatric speciation. Here, we show that divergent evolution in sexual morphology affecting mating compatibility (body size and genital morphologies) and speciation have occurred in a lineage of millipedes, the Parafontaria tonominea species complex. In this millipede group, male and female body and genital sizes exhibit marked, correlated divergence among populations, and the diverged morphologies result in mechanical reproductive isolation between sympatric species. The morphological divergence occurred among populations independently and without any correlation with climatic variables, although matching between sexes has been maintained, suggesting that morphological divergence was not a by-product of climatic adaptation. The diverged populations underwent restricted dispersal and secondary contact without hybridization. The extent of morphological difference between sympatric species is variable, as is diversity among allopatric populations; consequently, the species complex appears to contain many species. This millipede case suggests that sexual selection does contribute to species richness via morphological diversification when a lineage of organisms consists of highly divided populations owing to limited dispersal.     

Consequences of hybridization between Ohomopterus insulicola and O. arrowianus (Coleoptera, Carabidae) in a segmented river basin: parallel formation of hybrid swarms

A putative hybrid zone between flightless earabid beetles, (iambus (Ohomopterus) insulicola and C. (0.) arrowianus nakamurai in the Ina Valley, central Honshu. Japan, was studied using experimental hybridization and morphological analysis. The principal morphological character analysed was a functional part of the male genitalia (the eopulatory piece), which is also the key diagnostic character in taxonomy. The habitat of the earabid beetles is fragmented by the Tenryu River, which runs through the Ina Valley, and its tributaries. Ohomopterus insulicola and 0. a. nakamurai occur in the upstream and downstream areas of the river basin, respectively, and a putative hybrid swarm (0. insulicola ssp. pseiidinsulkola) is found in the boundary area on the cast side of the Tenryu River. Experimental hybridization between 0. insulicola and 0. a. nakamurai resulted in F₁ offspring that were morphologically similar to 0. i. pseudinsulicola. Pre‐zygotic reproductive isolation was incomplete, although the F₁ males had a dysfunction in sperm production and were almost sterile. Only a single F₁ pair produced F₂, Backcrosses of F₁ females of males of the parental species resulted in offspring that were similar to the parental species in genital morphology. Based on the discriminant function for the shape of the eopulatory piece resulting from the experimental hybridization, we demonstrate that similar hybrid swarms exist on both sides of the Tenryu River, but in locations 25 km apart. This demonstrates parallelism in hybridization events with similar consequences. The hybrid swarms consisted of beetles with intermediate morphological characters and did not contain obvious parental forms. The establishment of such intermediate populations may have been facilitated by selection for fertile hybrids in segregated local sites in the absence of frequent immigration of parental species. This study suggests that a segmented river basin provides an opportunity for establishing novel evolutionary lineages resulting from hybridization.     

Identification of elmid larvae (Coleoptera: Elmidae) from Sanin District of Honshu,Japan, based on mitochondrial DNA sequences

Larvae of Elmidae from the Sanin District, Honshu, Japan, were classified into 14 types based on morphological features, of which 11 types were unidentified for species. Species or genus of the unidentified types were determined by comparing their mitochondrial cytochrome oxidase subunit I gene sequences with those of identified adult specimens. A new key to species/genera of elmid larvae was proposed.