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Systematic studies were undertaken on the Caloglossa continua (Okammura) King et Puttock complex from Japan, Singapore, and Austriala, based on morphology and reproductive compatibility. Specimens from Japan had two to six cell rows derived from a nodel axial cell, at the margin opposite the branch, whereas those from Austraila possessed only a single cell now. Specimens from Singapore formed one to four cell rows per nodal axial cell and always contained at least one single cell row on any one thallus. These differences were maintained in cultural materials over a range of temperagtures or salinities. Type material of C. continua had the same morphology as the Japanese specimens in this study. Carpospores discharged from the Japanese isolate germinated at 10°C, whereas those from Singapore and Australia died at this temperature. In hybridization experiments, the Japanese entity was completely nonfertile with both the Singaporean and Australian isolates. Many pseudocystocarps were produced in the crossing between the make from Australia and the female from Singapore, although the reciprocal combination did not produce any such structures. On the basis of the discontinuous morphology coupled with the complete reproducture isolation, the entiries from Singapore and Australia are described here as C. monosticha sp. nov. The entiries with multiple cell rows likely expanded their geographic range from tropical regions, where the majority of Caloglossa species are now distributed, to high-latitude regions, and such an expansion would be associated with acquining low-temperature tolerance. [ABSTRACT FROM AUTHOR]

Fallacia is distinguished morpho‐anatomically from Navicula sensu lato based on the possession of an H‐shaped chloroplast, lateral sterna and a finely porous conopeum, but whether this genus is monophyletic is still in question. Three new Fallacia species are described based on morphology and SSU rRNA and rbcL gene sequences: Fallacia tateyamensis sp. nov., Fallacia bosoensis sp. nov. and Fallacia laevis sp. nov. We performed the first comprehensive molecular and morphological phylogenetic analyses of 31 Fallacia species based on 11 new sequences from six species and 23 morphological characters. We also documented the detailed morphogenesis of Fallacia for the first time. Fallacia is not monophyletic. Both morphological and DNA sequence data supported the separation of Rossia from Fallacia, while the phylogenetic position of Pseudofallacia is uncertain. We recognized four morphogroups in Fallacia by morphological and molecular phylogenetic analyses. Ancestral character reconstruction indicated that diatoms in Sellaphoraceae evolved from the possession of two lateral narrow parallel depressions covered by narrow nonporous conopea, to lyre‐shaped canals covered by wide porous conopea. Lanceolate canals and the presence of areolae in canals evolved multiple times independently. [ABSTRACT FROM AUTHOR]

Many of the genes that control photosynthesis are carried in the chloroplast. These genes differ among species. However, evidence has yet to be reported revealing the involvement of organelle genes in the initial stages of plant speciation. To elucidate the molecular basis of aquatic plant speciation, we focused on the unique plant species Chara braunii C. C. Gmel. that inhabits both shallow and deep freshwater habitats and exhibits habitat-based dimorphism of chloroplast DNA (cpDNA). Here, we examined the 'shallow' and 'deep' subpopulations of C. braunii using two nuclear DNA (nDNA) markers and cpDNA. Genetic differentiation between the two subpopulations was measured in both nDNA and cpDNA regions, although phylogenetic analyses suggested nuclear gene flow between subpopulations. Neutrality tests based on Tajima's D demonstrated diversifying selection acting on organelle DNA regions. Furthermore, both 'shallow' and 'deep' haplotypes of cpDNA detected in cultures originating from bottom soils of three deep environments suggested that migration of oospores (dormant zygotes) between the two habitats occurs irrespective of the complete habitat-based dimorphism of cpDNA from field-collected vegetative thalli. Therefore, the two subpopulations are highly selected by their different aquatic habitats and show prezygotic isolation, which represents an initial process of speciation affected by ecologically based divergent selection of organelle genes. [ABSTRACT FROM AUTHOR]

Reports on the use of morphological comparisons, hybridization experiments and molecular phylogenetic analyses using the RUBISCO spacer region on 12 populations of red algae Caloglossa leprieurii and C. apomeiotica in order to identify their relationships. Indication that the asexual species was derived from sexual plants of the multiple cell row type; Correlation of reproductive compatibility with genetic distance rather than geographical distance.