Miscellaneous mistletoe notes, 48–60: Descriptions of twelve new species of Loranthaceae and Viscaceae

Twelve new South American species of Loranthaceae (Aetanthus, Cladocolea, Oryctanthus, and Struthanthus) and Viscaceae (Dendrophthora and Phoradendron) are described and illustrated: Aetanthus trifolius, Cladocolea rostrifolia, Dendrophthora lanceolata, Dendrophthora rotundata, Dendrophthora tenuis, Dendrophthora werffii, Oryctanthus minor, Phoradendron pascoi, Phoradendron vasquezianum, Struthanthus apiculatus, Struthanthus schultesii, and Struthanthus sessiliflorus. Additionally, Cladocolea alternifolia, previously thought to be probably extinct, is reported to occur on Ilha Grande, just west of Rio de Janeiro, Brazil.     

Phoradendron olae Kuijt, a new species from Mexico pivotal in the taxonomy of the genus, with comments on P. californicum Nutt.

Materials are presented to the effect thatPhoradendron californicum Nutt., the nomenclatural type of the genusPhoradendron (Viscaceae), is related to southern, cataphyllous species, not to northern, acataphyllous ones. The evidence consists of the frequent occurrence of basal cataphylls in the species, variation in basal phyllotaxy, and a basically biseriate arrangement of flowers on fertile internodes. The suggestion of this southern, cataphyllous affinity is supported by the recent discovery of a strictly cataphyllous Mexican species,P. olae Kuijt, which shows median basal phyllotaxy and is in many features extremely similar toP. californicum. The nomenclatural consequences of this discovery would lead to subgen.Boreales (Trel.) Engler (and probably subgen.Aequatoriales (Trel.) Engler) being synonymized under subgen.Phoradendron, characterized by basal cataphylls (though not in all species). However, no generic subdivision of any sort is supported at this time.     

基于叶绿体DNA trnL内含子序列数据的檀香目科间系统发育关系的研究

应用叶绿体DNAtrnL内含子序列分析檀香目科间的系统发育关系。取样研究的檀香目个体的trnL内含子序列长度在科间呈现较大差异(从291bp到587bp)。最大简约性分析产生的严格一致树与以前已发表的基于其它基因的檀香目的分子系统学研究结果大体一致。香芙木属(铁青树科)是最早分支出的类群：桑寄生科、槲寄生科分别表现为单系类群,檀香科为并系;桑寄生科和槲寄生科并不具密切亲缘关系,槲寄生科从檀香科内衍生出来。本研究表明,具相对高的核苷酸替换率的叶绿体DNAtrnL内含子序列可为高等级类群系统发育关系的研究提供更多的信息位点。     

Occurrence of the lutein-epoxide cycle in mistletoes of the Loranthaceae and Viscaceae

The lutein-epoxide cycle (Lx cycle) is an auxiliary xanthophyll cycle known to operate only in some higher-plant species. It occurs in parallel with the common violaxanthin cycle (V cycle) and involves the same epoxidation and de-epoxidation reactions as in the V cycle. In this study, the occurrence of the Lx cycle was investigated in the two major families of mistletoe, the Loranthaceae and the Viscaceae. In an attempt to find the limiting factor(s) for the occurrence of the Lx cycle, pigment profiles of mistletoes with and without the Lx cycle were compared. The availability of lutein as a substrate for the zeaxanthin epoxidase appeared not to be critical. This was supported by the absence of the Lx cycle in the transgenic Arabidopsis plant lutOE, in which synthesis of lutein was increased at the expense of V by overexpression of -cyclase, a key enzyme for lutein synthesis. Furthermore, analysis of pigment distribution within the mistletoe thylakoids excluded the possibility of different localizations for the Lx- and V-cycle pigments. From these findings, together with previous reports on the substrate specificity of the two enzymes in the V cycle, we propose that mutation to zeaxanthin epoxidase could have resulted in altered regulation and/or substrate specificity of the enzyme that gave rise to the parallel operation of two xanthophyll cycles in some plants. The distribution pattern of Lx in the mistletoe phylogeny inferred from 18S rRNA gene sequences also suggested that the occurrence of the Lx cycle is determined genetically. Possible molecular evolutionary processes that may have led to the operation of the Lx cycle in some mistletoes are discussed.Abbreviations A antheraxanthin - - and -Car - and -carotene - Chl chlorophyll - -DM dodecyl--d-maltoside - DPS de-epoxidation state of the violaxanthin cycle (= [A+Z]/[V+A+Z]) - Lut lutein - Lx lutein epoxide - Caro total carotenoid concentration - V violaxanthin - VAZ pool size of the violaxanthin cycle (= V+A+Z) - VDE violaxanthin de-epoxidase - Z zeaxanthin - ZE zeaxanthin epoxidase     

Flange-type parenchyma cells: occurrence and structure in the haustorium of the dwarf mistletoeKorthalsella (Viscaceae)

Summary Flange cells are an unusual type of parenchyma cells with an open reticulate pattern of secondary wall thickenings. The cells superficially resemble tracheary elements but are otherwise fundamentally different. Flange cells were found in haustorial sucker tissue of the dwarf mistletoeKorthalsella. Such cells were previously unknown for a mistletoe, or other parasitic angiosperm. Flange cells are confined to the xylem of the sucker and occur as either diffuse aggregates amongst the ordinary parenchyma tissue lying between the tracts of vessels, or abut the vessels. Typical flange cells are absent at the parasite/host xylem interface. The cells contain a well differentiated protoplast, including chloroplasts with extensive granal stacks. Histochemical staining and fluorescence microscopy indicate lignification of the flange wall. In thin section, the flange wall is often stratified into dark and light staining layers. Flange cells inKorthalsella resemble contact cells, vessel associated cells and certain types of transfer cells reported in the literature. Based on morphological considerations, it is suggested that flange cells inKorthalsella are involved in absorption and transport between host and parasite. As host sap moves through the sucker apoplasm, substance might be selectively absorbed by the flange cell, before the remaining the sap passes into the vessels for long distance transport in the mistletoe.Dedicated to Prof. Dr. Rainer Kollmann on the occasion of his 65th birthday     

Evolution of larval food plant associations in Delias Hübner butterflies (Lepidoptera: Pieridae)

A review of larval food plants of the genus Delias is presented. Larvae specialize primarily on aerial‐stem and root hemiparasites (“mistletoes”) in the order Santalales. Although butterfly food plant associations have been recorded for only a small proportion of the genus (28 species or ～11%, representing 12/24 species‐groups), available data suggest that the family Loranthaceae is used most frequently (77%), followed by the Santalaceae sensu stricto (14%) and Viscaceae (8%). With the possible exception of Euphorbiaceae (1%), almost all non‐mistletoe records are considered to be erroneous and, in most cases, probably represent the mistletoe host tree on which the larvae sometimes pupate. Of the eight major clades recognized in Delias, food plants have been recorded for six of these, although the majority of records (89%) are for three clades (hyparete, belladonna, nigrina). Optimization of the larval food plant data in the context of recent phylogenetic hypotheses for both butterflies and plants revealed little evidence of cospeciation at the higher systematic levels. The most parsimonious reconstruction was an origin of larval feeding on Loranthaceae, followed by at least six independent colonizations to Santalaceae + Viscaceae. In contrast to related pierids in the Aporiina associated with mistletoes in which further shifts from aerial‐stem mistletoes to distantly related plants (e.g. host trees parasitized by mistletoes) have facilitated differentiation at the generic level, there is no firm evidence to indicate that such secondary, monomorphic shifts have evolved in Delias. However, larvae of D. henningia (pasithoe group of belladonna clade) from Palawan and Luzon, the Philippines, appear to be polymorphic, feeding on both Loranthaceae and Euphorbiaceae.     

Phylogenetic relationships within Korthalsella (Viscaceae) based on nuclear ITS and plastid trnL-F sequence

The nuclear encoded internal transcribed spacer (ITS) region and the plastid encoded trnL-F region were sequenced for 25 populations of Korthalsella, a genus of reduced, monoecious, Old World misletoes. The molecular study confirms the hypothesis that branch shape and cladotaxy (the arrangement of branches with respect to their parent axis) are unreliable indicators of relationship in the genus and demonstrates that many of the taxa previously recognized are not monophyletic. Both gene regions identify three major subgroups within the genus and find lower level relationships within these subgroups highly correlated with geographic distance. An analysis based upon 18S and rbcL sequences identifies Ginalloa as the sister group to Korthalsella, which together with the branching order within the genus, indicates that Korthalsella originated in Papuasia and aids in elucidating evolution of the peculiar inflorescence structure. There are problems associated with species delimitation when evolutionary units are more restricted than morphological lineages, and justification is offered for recognizing only morphologically diagnosable monophyletic lineages as species. Varying substitution rates and differing modes of inheritance in ITS and trnL-F result in complementary utility of the two regions for elucidating infrageneric relationships in Korthalsella.     

Charting the isophasic endophyte of dwarf mistletoe Arceuthobium douglasii (Viscaceae) in host apical buds

• Background and Aims Dwarf mistletoes (Arceuthobium; Viscaceae)are highly specialized dioecious angiosperms parasitic on manygymnosperm hosts in the northern hemisphere. Several dwarf mistletoespecies are capable of inducing an unusual form of isophasicinfection in which the internal (endophytic) system proliferateseven into the apical buds of its hosts. Studies of the internalendophytic system have, for the most part, focused on the parasitewithin secondary host tissues. The present anatomical and ultrastructuralstudy characterizes the growth pattern of the isophasic endophyticsystem of Arceuthobium douglasii within the dormant apical budsof Pseudotsuga menziesii. • Methods Semi-thin serial sections from dwarf mistletoe-infectedhost apical buds were mounted, stained and micrographed. Graphicfiles were created from the serial micrographs and these fileswere stacked. These stacked files were utilized to describethe pattern of growth of the endophyte within the host tissue.The interface between cells of the mistletoe and host was alsoexamined at the ultrastructural level by transmission electronmicroscopy. • Key Results By utilizing a novel technique of superimposedgraphics, the current study reveals an organized pattern ofmistletoe distribution that penetrates further into host tissuesthan previously known. A consistent pattern of growth occurringeven into the preformed leaves of the host is documented. • Conclusions The apparently non-intrusive growth of theparasite appears to be developmentally synchronized with thatof the host. No symplastic connections were observed in theultrastructural examination of the parasite/host interface withinthe apical buds of Pseudotsuga menziesii parasitized by A. douglasiior of Pinus contorta parasitized by A. americanum.