Altitudinal variation of resin ducts in Pinus taiwanensis Hayata (Pinaceae) needles
The variation of resin ducts in needles of Pinus taiwanensis along an altitude gradient (700 m- 3,100 m) in central Taiwan is revealed for the first time in this study, including position type, number, size, arrangement pattern and anatomical structural variation. Three types of resin ducts-medial, external and septal-were found according to their relative positions in the mesophyll. All needles sampled showed combinations of these three resin duct types. Mostly, 3-7 resin ducts were found in the mesophyll per needle, and the number of resin ducts was significantly greater at mid altitudes than at high and low altitudes. Septal ducts decreased in number with an increase in altitude; however, needles from mid altitudes had more external ducts. Eight patterns (basic and patterns I-VII) of resin ducts in the mesophyll of needles were delineated to present the arrangement variations. In addition to the primary ducts found in the mesophyll, we found the rare bundle sheath ducts in some needles, and their frequencies decreased obviously with an increase in altitude. The consistent combination feature of medial, external, and septal ducts in needles of P. taiwanensis from Taiwan could be easily distinguished from those with medial ducts from mainland China. However, this difference has unrecognized before, and it should be considered in future taxonomic work.
Comparative leaf anatomy of native and cultivated Pinus (Pinaceae) in Korea: implication for the subgeneric classification
Comprehensive comparative anatomy of Pinus leaves was carried out. Some anatomical features were found to be quite useful and supported the classification of genus to subgenus and section level. The number of needles per fascicle, number of vascular bundles, position of resin ducts, shape of leaf in cross section, and distribution of stomata on the leaf surface showed remarkable variation between different species and facilitated the classification of Pinus into minor groups: subgenus, section, and subsection. The members of subgenus Pinus had two vascular bundles whereas members of subgenus Strobus had only one vascular bundle. The position of resin ducts was more consistent in subgenus Strobus than in subgenus Pinus. Interestingly, the species of subsection Strobus included in this study lacked stomata on the abaxial surface. The results indicate that the number of needles per fascicle and needle size are inversely related, and more importantly that a greater numbers of needles per fascicle lead to a more angular shape.
Spatial distribution patterns of pine sawflies (Hymenoptera: Diprionidae) in Arizona, US and Sichuan, PR of China
Abstract In a comparison study of sawfly distribution patterns in the western US and southwestern China, we found that defoliation and oviposition were limited to certain forest stand characteristics. Both species (Neodiprion autumnalis Smith in Arizona, US and N. xiangyunicus (Xiao and Huang) in Sichuan, P.R. China) were restricted to pure stands of their hosts at specific elevations. Defoliation of ponderosa pine (Pinus ponderosa Dougl. ex Law.) by N. autumnalis was limited to a narrow elevational band (2410–2440 m) within the range of its host at the study site (approximately 2350–2650 m). Defoliation of and oviposition on yunnan pine (P. yunnanensis Franch.) by N. xiangyunicus was confined to a specific but wider elevational band (1850–2050 m) within the host range of the area studied (1650–2050 m). The density of ponderosa pine trees (measured as basal area (m2 ha−1)) also appears to play a role in the distribution of N. autumnalis. Defoliation by this species was limited to stand basal areas of less than 4.6 m2 ha−1. Stand density does not appear to have a significant influence on N. xiangyunicus defoliation patterns. However, a significant interaction between stand density and vertical crown position on oviposition by N. xiangyunicus was detected. Proportionately more egg clusters were found in the top of crowns at low stand densities, while egg clusters were located in the middle and bottom of crowns equally at all stand densities. Significant differences in defoliation intensity were not detected between crown level for either species. In addition to discerning these distribution patterns, we established that foliage characteristics varied across stand density and elevation gradients in both Arizona and Sichuan. Needles in low density compared with high density stands in Arizona were longer, wider, tougher, and had less water. Pine needles in Sichuan followed this same general pattern when comparing the foliage from low elevations with foliage from high elevations. We propose that longer needles of open-grown trees in Arizona allow ovipositing females to lay more eggs per needle which in turn benefits larval performance through increased feeding and defense against natural enemies. The 20% more tough needles of yunnan pine at low elevations in Sichuan may confine oviposition and larval feeding to higher elevations.