Vegetative diversification and radiation in subtribeDendrobiinae (Orchidaceae): Evidence from chloroplast DNA phylogeny and anatomical characters

The data derived from a chloroplast DNA restriction site analysis of subtribeDendrobiinae (Orchidaceae) indicate that extreme vegetative diversification is concentrated in two limited parts of this group. Overlaying the vegetative character states onto the chloroplast DNA cladogram suggests that several xeromorphic, vegetative characters evolved in the lines leading to the above-mentioned clades. Several anatomical characters are also associated with xeromorphy. These vegetative and anatomical characters facilitated the establishment of this group in various dry habitats. On the other hand, the modifications of size and number of parenchymatous cells substantially contributed to the vegetative diversification. This fact implies that a simple structural adjustment can result in a major modification of growth habits in theDendrobiinae.     

ÜberHydrianum viride (Characiaceae,Chlorophyceae), seine fortpflanzung und taxonomie

The little known epiphytic algaHydrianum viride was studied and pictured. The morphology and the variability of the vegetative cells are described in detail and compared with the observations of other authors. For the first time typical biflagellate zoospores of the chlorophycean-type have been recognized and the course of the asexual reproduction is studied. The residual protoplasm, that is the proximal half of the zoosporangium protoplast, growth up to the original size, typical for the genusHydrianum. The life cycle, especially the settling down of the zoospores, is described.Hydrianum viride belongs to the characteristic inhabitants of peaty waters; it belongs together with the host alga,Microspora loefgrenii, to the dominants of algal association of peat-springs. At last the taxonomic position and the synonyma of this organism are discussed.

     

Litter‐trapping plants: filter‐feeders of the plant kingdom

Litter‐trapping plants have specialized growth habits and morphologies that enable them to capture falling leaf litter and other debris, which the plants use for nutrition after the litter has decayed. Litter is trapped via rosettes of leaves, specially modified leaves and/or upward‐growing roots (so‐called ‘root baskets’). Litter‐trappers, both epiphytic and terrestrial, are found throughout the tropics, with only a few extra‐tropical species, and they have evolved in many plant families. The trapped litter mass is a source of nutrients for litter‐trapping plants, as well as food and housing for commensal organisms. Despite their unique mode of life, litter‐trapping plants are not well documented, and many questions remain about their distribution, physiology and evolution.–© 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 179 , 554–586.     

Comparative vegetative anatomy and systematics of Cymbidium (Cymbidieae: Orchidaceae)

The genus Cymbidium (Orchidaceae) exhibits distinctive ecological diversification and occurs in terrestrial, epiphytic, and lithophytic life forms. One species, Cymbidium macrorhizon , lacks foliage leaves and has a strongly mycoparasitic existence. Correlation between habitat differentiation and anatomical characters was tested for 21 species of Cymbidium and its putative sister groups. Although hypostomaty characterizes the genus, C. canaliculatum shows amphistomaty. Ecological preference of this species indicates that amphistomaty is likely adapted to intensive insolation. Four types of subepidermal foliar sclerenchyma were found. Two forest floor species, C. goeringii and C. lancifolium as well as the mycoparasitic C. macrorhizon , do not have this sclerenchyma. In this genus, development of sclerenchyma is correlated with the degree of epiphytism. Palisade mesophyll evolved in Cymbidium section Cymbidium . As members of this section grow on isolated trees in tropical lowland forests or on rocks, the differentiation of palisade tissue is probably correlated with immigration to high light habitats. With the exception of C. macrorhizon , stegmata were found in leaves and stems of Cymbidium . Furthermore, a few epiphytic species have stegmata in their roots; this is a curious feature rarely found in vascular plants. Subterranean rhizomes characterize terrestrial species, while ageotropic roots are found in some epiphytic species. Cymbidium macrorhizon shows peculiar features such as degeneration of stomata, anomocytic stomata, and lack of stegmata and sclerenchyma. This set of character transformations is probably correlated with the evolution of mycoparasitic existence. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 138 , 383–419.     

STUDIES OF MESOHERBIVORY IN AQUARIA AND IN AN UNBARRICADED MARICULTURE FARM ON THE CHINESE COAST1

The effects upon macrophytic and epiphytic algae of caprellid amphipods, including Caprella irregularis Mayer, and of gammarid amphipods, including Ampithoe lacertosa Bate, Jassa falcata (Montagu) and Pontogeneia rostrata Gurjanova, were studied in aquaria and in a coastal mariculture farm near Qingdao, People's Republic of China. The macrophytic species studied included Enteromorpha linza (L.) J. Agardh, Gracilaria asiatica Zhang & Xia, Gracilaria lemaneiformis (Bory) Weber-van Bosse and Scytosiphon lomentaria (Lyngbye) C. Agardh. These algae and amphipods were selected for study because of their local abundances. Aquarium experiments demonstrated that C. irregularis, J. falcata and P. rostrata feed on ephemeral/epiphytic algae. A. lacertosa (adults and juveniles) ate Gracilaria but preferred E. linza. The different species of amphipods had substantially different patterns of daily activity. Caprellids prevented epiphytic overgrowth of G. asiatica when added to plants in an experimental, openocean, mariculture farm, despite the presence of numerous amphipod predators (e.g. the fishes Hexagrammos otakii Jordan & Starks and Sebastes thompsoni Jordan & Hubbs). Periodic removals of all (naturally colonizing) amphipods from another group of plants in the farm resulted in heavy epiphytic overgrowth. Since these results were obtained in an unbarricaded mariculture farm, we conclude that mesoherbivores may have large effects upon algal community structure in temperate intertidal and subtidal habitats.     

The first fossil Microsoroid fern (Palaeosorum ellipticum gen. et sp. nov.) from the middle Miocene of Yunnan,SW China

The microsoroid ferns make up a large group in the family Polypodiaceae, easily characterized by the combination of at least partly clathrate rhizome scales and anastomosing reticulate venation. The diversification of this clade is poorly known, both because of unresolved generic delimitations and the lack of fossil records. In this work, we describe the first microsoroid macrofossil: Palaeosorum ellipticum sp. nov. F. M. B. Jacques & Z. K. Zhou. The fossil specimen, represented by part and counterpart, was found in the middle Miocene sediment of the Dajie Formation in Ailsohan, central Yunnan, southwest China. Epiphytic ferns belonging to Drynariaare found in different locations in Yunnan during the Pliocene. The fossil described in this study deepens the occurrence of epiphytic ferns in Yunnan back to the middle Miocene. It demonstrates that forests with complex ecological relationships have existed in southwest China for more than 10 million years.     

FACTORS ASSOCIATED WITH HOST SPECIFICITY IN SPOROCLADOPSIS NOVAE-ZELANDIAE (CHLOROPHYTA)1

This study tests the hypotheses that substrate stability and rugose microtopography are the main factors that determine the tissue-specific epiphytism in the chlorophyte Sporocladopsis novae-zelandiae Chapman. Both in vitro and field experiments showed that the epiphyte did not develop on stable algal surfaces nor on artificial (smooth or rugose) substrata. In field experiments, however, other macroalgae settled more abundantly on rugose substrata. Similarly, our field experiments did not support the hypothesis that the physical environment provided by the spatial location of the host in the intertidal or subtidal was a relevant factor associated with specificity. In contrast, our laboratory experiments suggested that some component of the host cell wall might trigger the formation of penetrating rhizoids. These did not develop in isolated cultures of the epiphyte but were detected when the epiphyte contacted its natural host. Also, preliminary results showed that rhizoid-like structures developed, although at very low frequency, only in plants grown in culture medium containing a crude extract of sorus cortical tissue.     

ROLE OF SURFACE WOUNDS AND BROWN ALGAL EPIPHYTES IN THE COLONIZATION OF ASCOPHYLLUM NODOSUM (PHAEOPHYCEAE) FRONDS BY VERTEBRATA LANOSA (RHODOPHYTA)1

Ascophyllum nodosum (L.) Le Jol. forms extensive beds in wave‐sheltered, rocky intertidal habitats on the northwestern Atlantic coast. This fucoid seaweed is host to an obligate red algal epiphyte, Vertebrata lanosa (L.) T. A. Chr. [=Polysiphonia lanosa (L.) Tandy], and two facultative brown algal epiphytes, Elachista fucicola (Velley) Aresch. and Pylaiella littoralis (L.) Kjellm. Although V. lanosa can occur throughout most of the length of host fronds, it largely predominates in midfrond segments. The two brown algal epiphytes are restricted to distal segments. Through field experiments conducted in Nova Scotia, Canada, we tested the hypothesis that surface wounds are required for the colonization of distal segments of host fronds by V. lanosa. Distal tissues normally have a smooth surface because of their young age (A. nodosum fronds grow apically). By creating small wounds that mimicked grazing wounds distributed elsewhere on host fronds, we demonstrated that V. lanosa can colonize distal frond segments during the growth and reproductive season (summer and autumn). Approximately half of the artificial wounds were colonized by V. lanosa during this time. The experimental exclusion of both brown algal epiphytes from distal frond segments did not affect colonization by V. lanosa. Thus, we conclude that the absence of surface irregularities on distal segments of host fronds, specifically small wounds, is the main factor explaining the absence of V. lanosa there. We propose that further experimental work clarifying epiphyte distribution in host beds will enhance our ability to understand the functional role of epiphytes in intertidal ecosystems.     

Epiphytic relationships of Pseudendoclonium submarinum Wille (Ulvophyceae) and Rhodymenia pseudopalmata (Rhodophyta) from the Patagonian coast of Argentina

The occurrence of the epiphyte alga Pseudendoclonium submarinum Wille (Ulvophyceae) on Rhodymenia pseudopalmata (Lamouroux) Silva (Rhodophyta) is reported. The present study describes a first line of evidence of an epidemiological study conducted with the purpose of comparing both the prevalence and effects of algal epiphytic organisms in R. pseudopalmata in the Patagonian coasts of Argentina. P. submarinum infected approximately 80% of R. pseudopalmata thalli and the frequency of infection was variable in connection with different areas of the host's thalli: 42% of R. pseudopalmata fronds presented P. submarinum thalli in the basal region, which presented a severity degree of infection from low to high. The median region presented an average frequency of infection of 30% and minor susceptibility to colonization. The covering varied from 1% to 70% representing a low to moderate degree of colonization. The apical region presented a cover frequency of 28% and the level of infection varied between low to moderate. The developmental morphology and the growth dynamics of the epiphyte were also investigated under unialgal as well as bialgal culture conditions. In nature, thalli of P. submarinum on R. pseudopalmata never invaded internal tissues of the host. Vegetative thalli of P. submarinum were inoculated on fronds R. pseudopalmata. Experimental infections confirmed that P. submarinum thalli did not penetrate the host's fronds. P. submarinum swarmers showed the capacity of settlement on a host's fronds and developed an epiphytic monostromatic thallus. The results allowed us to suggest that P. submarinum uses the R. pseudopalmata thalli as a proper substrate, since Pseudendoclonium thalli complete the entire life cycle. Culture experiments revealed that P. submarinum could develop without the presence of the host and evidenced the nutritional independence, being the relationship in nature, probably triggered by an ecological advantage since fronds of R. pseudopalmata offer a suitable substratum.