DNA barcoding using a partial region (648 bp) of the cytochrome c oxidase I (COI) gene is a powerful tool for species identification and has revealed many cryptic species in various animal taxa. In birds, cryptic species are likely to occur in insular regions like the Japanese Archipelago due to the prevention of gene flow by sea barriers. Using COI sequences of 234 of the 251 Japanese-breeding bird species, we established a DNA barcoding library for species identification and estimated the number of cryptic species candidates. A total of 226 species (96.6%) had unique COI sequences with large genetic divergence among the closest species based on neighbour-joining clusters, genetic distance criterion and diagnostic substitutions. Eleven cryptic species candidates were detected, with distinct intraspecific deep genetic divergences, nine lineages of which were geographically separated by islands and straits within the Japanese Archipelago. To identify Japan-specific cryptic species from trans-Paleartic birds, we investigated the genetic structure of 142 shared species over an extended region covering Japan and Eurasia; 19 of these species formed two or more clades with high bootstrap values. Excluding six duplicated species from the total of 11 species within the Japanese Archipelago and 19 trans-Paleartic species, we identified 24 species that were cryptic species candidates within and surrounding the Japanese Archipelago. Repeated sea level changes during the glacial and interglacial periods may be responsible for the deep genetic divergences of Japanese birds in this insular region, which has led to inconsistencies in traditional taxonomies based on morphology.

Summary1 Sasa spp., dwarf bamboo which dominate the undergrowth of temperate forests in Japan occur as clonal fragments in which ramets in light gaps to are connected to those in shaded understoreys by long rhizomes. We test whether persistence under shaded conditions is supported by translocation of assimilates from illuminated ramets. A dense population of Sasa palmata growing at an open site, was exposed to two light conditions (homogeneous: open-open and heterogeneous: open-shaded) and two rhizome connection treatments (intact and severed) in a full factorial design. 2 Ramet mass, and the mass of many parts of the clonal fragments, was much lower in the shade than in the open, but this effect was less marked when the rhizome connection was intact than when it was severed. Clone parts in shade may therefore be supported by translocation from connected clone parts in the open, with such physiological integration enhancing persistence where light supply is heterogeneous as in the gap -understorey continuum. 3 Above-ground biomass was reduced sooner than that below ground. Clonal fragments of S. palmata recover via dormant buds on rhizomes, whose longer persistence would therefore enhance performance of the clonal fragment. 4 Specific leaf area (SLA) was greater in shade than in the open, irrespective of rhizome connection, suggesting that individual leaves show morphological plasticity independently of only physiological integration.

This study clearly demonstrated that nitrogen is readily translocated between ramets, particularly under heterogeneous resource conditions. The translocation patterns were governed by functional 'division of labour' mechanisms that resulted in net nitrogen movement from understory sites to gaps, thereby enhancing the carbon acquisition of the whole fragment. Thus, physiological integration may provide benefits for S. palmata when it is growing under heterogeneous conditions in which there are deficits of certain environmental resources.

No abstract

No abstract