Multicellular Propagules Research Articles

Vegetative reproduction and phylogeny of a new subtidal alga from Korea: Dipterocladia yongdeokkoi sp. nov. (Ceramiales, Rhodophyta)

ABSTRACTDipterocladia yongdeokkoi sp. nov. was collected at depths of 6–15 m at three locations at Jeju Island, Korea: Biyangdo, Hado and Shinchang. All plants were vegetative without reproductive structures. For two years in laboratory culture, plants were consistently vegetative. Cultured plants formed single-celled diaspores and multicellular propagules that grew into mature plants. Dipterocladia yongdeokkoi is distinguished by its flattened thallus arising from a thick, cylindrical stipe, compressed axes, irregular branches and alternately pinnate determinate adventitious laterals and pseudolaterals. Analyses of mitochondrial cox1, plastid rbcL, and nuclear small subunit (SSU) sequences support the monophyly of Dipterocladia and the distinctness of D. yongdeokkoi from other species of Dipterocladia.

Experimental evolution of multicellularity

Multicellularity was one of the most significant innovations in the history of life, but its initial evolution remains poorly understood. Using experimental evolution, we show that key steps in this transition could have occurred quickly. We subjected the unicellular yeast Saccharomyces cerevisiae to an environment in which we expected multicellularity to be adaptive. We observed the rapid evolution of clustering genotypes that display a novel multicellular life history characterized by reproduction via multicellular propagules, a juvenile phase, and determinate growth. The multicellular clusters are uniclonal, minimizing within-cluster genetic conflicts of interest. Simple among-cell division of labor rapidly evolved. Early multicellular strains were composed of physiologically similar cells, but these subsequently evolved higher rates of programmed cell death (apoptosis), an adaptation that increases propagule production. These results show that key aspects of multicellular complexity, a subject of central importance to biology, can readily evolve from unicellular eukaryotes.

Extirpation of macroalgae (Sargassum spp.) on the subtropical east Australian coast.

Populations of large brown algae of the Laminariales and Fucales (Phaeophyta) have declined or been extirpated from many locations on temperate coasts worldwide. We conducted field surveys and a literature review, and examined herbarium specimens, through which we discovered previously unreported extirpations of large brown algal species from a tropical and subtropical coastline. Sargassum amaliae, S. aquifolium, S. carpophyllum, S. polycystum, and S. spinifex were common habitat-forming macroalgae that supported diverse assemblages of invertebrates and smaller algae before urbanization began in 1970 along the 45-km length of Sunshine Coast in Queensland, Australia. Causes of these extirpations are not known, but are consistent with losses of other large brown algal species from coastal areas undergoing urbanization or eutrophication. Sargassum spp. do not have the characteristics thought to protect marine species from extinction (large geographical ranges, occurrence on many different substrata, long-distance dispersal). Some local Sargassum spp. are endemic to eastern Australia. Abundance of Sargassum is limited by suitable substrata on the sandy southern Queensland coast (370 km). These substrata are 12 rocky headlands separated by long (5-105 km) sandy beaches. Most multicellular propagules (the only motile stage in Sargassum) settle within 1-3 m of parental thalli, which restricts long-distance dispersal needed to maintain connectivity among populations and to recolonize areas of the headlands from which populations have been extirpated. Local Sargassum spp. could be categorized as data deficient by the International Union for Conservation of Nature (IUCN), but the IUCN vulnerable category is more accurate given extirpations, limited habitat, and the lack of connectivity among populations.

Vegetative reproduction by multicellular propagules in Rhodophyta: an overview

This paper deals with vegetative reproduction by multicellular propagules in Rhodophyta. An extensive examination of the relevant literature shows that this phenomenon in Rhodophyta is not well known. A propagule is here defined as a vegetative multicellular structure which spontaneously detaches from the parent thallus and gives rise to a new individual. The origin and morphological features of multicellular propagules are examined in the various known propagule-forming species. The importance of multicellular propagules as both overwintering and resting organs and as a taxonomic feature is also shown. Their role in increasing local populations and/or for long-distance dispersal is discussed. The relative abundance of vegetative reproduction by multicellular propagules versus sexual reproduction, as well as the advantages of this additional mode of reproduction, are shown and discussed. The production of multicellular propagules may contribute to the capacity of species to increase populations, to weather unpredictable environmental changes, to survive in conditions that would be lethal for entire thalli, and to reach new habitats. As resting organs, they may also be responsible for long-distance dispersal and may account for the introduction of some alien species. Accordingly, propagule-forming species are probably more competitive than taxa that do not produce such propagules. These considerations should be taken into account in future studies of the biology, ecology and demography of Rhodophyta.

Redheadia quercus gen. et sp. nov., the teleomorph of Mycopappus quercus, the frosty mildew fungus in Quercus acutissima

The teleomorph of Mycopappus quercus causing frosty mildew in Quercus acutissima is described as a new genus and species, Redheadia quercus, in the Sclerotiniaceae. Apothecia sprout from sclerotia on the fallen infected leaves kept for 10 months at 5°C and subsequent incubation at 15°C under diffused room light. Typical zonate lesions and multicellular propagules of M. quercus are produced on Q. acutissima, by mycelial inoculation using an isolate from a single ascospore, confirming the teleomorph–anamorphic connection. No significant differences are observed between cultured colonies of isolates from the ascospore and those from the propagule. Sclerotia and microconidia of the fungus are produced on culture media.

Mycopappus quercus sp. nov., causing frosty mildew in Quercus acutissima

The causal fungus of frosty mildew inQuercus acutissima was taxonomically studied. Brown spots with conical white to yellowish tufts of the causal, fungus developed on the leaves, followed by successive defoliation. The fungus was regarded as a new species ofMycopappus, M. quercus, from the morphology of the multicellular propagules. The ascogenous stage and true conidia of the fungus were not observed, although sclerotia were formed on the fallen diseased leaves.

New species of the aeroaquatic hyphomycete genus Clathrosporium and their relationship with Strumella Sacc.

Clathrosporium Nawawi & Kuthubutheen is found to be synonymous with Strumella Sacc. (lectotypified by Strumella olivatra (Sacc.) Sacc.), a later illegitimate homonym of Strumella Fr. Consequently, Strumella olivatra is redisposed in Clathrosporium, alongside the type species Clathrosporium intricatum Nawawi & Kuthubutheen. Two new species, Clathrosporium delicatum Hennebert sp.nov. and Clathrosporium compactum Hennebert n.sp., are described and illustrated. These hyphomycetes are aeroaquatic, growing on periodically submerged plant material, leaves, and rotten wood. They produce pigmented, multicellular propagules comprising coiled, branching hyphae that disarticulate into arthroconidia when mature.Key words: aeroaquatic, hyphomycete, Clathrosporium olivatra, Clathrosporium vinosa, Clathrosporium delicatula, Clathrosporium compacta, Strumella, Spirosphaera, taxonomy.

Mycodidymella aesculi gen. et sp. nov. and its synanamorphs Blastostroma aesculi gen. et sp. nov. and Mycopappus aesculi sp. nov. on Aesculus turbinata in Japan

A new disease was recognized on leaves of Aesculus turbinata in northeastern Japan. The disease is characterized by large concentric ring spots on which numerous multicellular and frequently non-sporiferous propagules are produced. The multicellular propagules are considered to be sporodochia because conidia of the fungus were found on artificially infected and naturally diseased leaves and culture experiments demonstrated that the propagules are conidiomata from which conidia are produced at low temperatures. The sporodochia may play a main role in secondary infection of the disease as infective bodies in summer because conidia only appeared in late autumn (October) on fallen diseased leaves. Conidia form in two ways, one on sporodochia, another from the stromatic sporodochia after the sporodochia detach themselves from the leaves. The teleomorph of the fungus is described as Mycodidymella aesculi, a new genus and species in the Phaeosphaeriaceae Barr. Mycopappus aesculi and Blastostroma aesculi are proposed as synanamorphs of Mycodidymella aesculi for the sterile sporodochial and conidial states, respectively. The teleomorph-anamorph connection and the sporodochial and conidial relationship of Mycopappus aesculi and Blastostroma aesculi were confirmed by inoculation and culture experiments.

Mycodidymella aesculi gen. et sp. nov. and Its Synanamorphs Blastostroma aesculi Gen. et sp. nov. and Mycopappus aesculi sp. nov. on Aesculus turbinata in Japan

A new disease was recognized on leaves of Aesculus turbinata in northeastern Japan. The disease is characterized by large concentric ring spots on which numerous multicellular and frequently non-sporiferous propagules are produced. The multicellular propagules are considered to be sporodochia because conidia of the fungus were found on artificially infected and naturally diseased leaves and culture experiments demonstrated that the propagules are conidiomata from which conidia are produced at low temperatures. The sporodochia may play a main role in secondary infection of the disease as infective bodies in summer because conidia only appeared in late autumn (October) on fallen diseased leaves. Conidia form in two ways, one on sporodochia, another from the stromatic sporodochia after the sporodochia detach themselves from the leaves. The teleomorph of the fungus is described as Mycodidymella aesculi, a new genus and species in the Phaeosphaeriaceae Barr. Mycopappus aesculi and Blastostroma aesculi are proposed as synanamorphs of Mycodidymella aesculi for the sterile sporodochial and conidial states, respectively. The teleomorph-anamorph connection and the sporodochial and conidial relationship of Mycopappus aesculi and Blastostroma aesculi were confirmed by inoculation and culture experiments.

Jania (Corallinales, Rhodophyta) in southern Australia

The coralline algal genus Jania Lamouroux (tribe Janieae, subfamily Corallinoideae, family Corallinaceae) contains six species on southern Australian coasts: J. micrarthrodia Lamouroux, J. pulchella (Harvey) comb. nov., J. pusilla (Sonder) Yendo, J. verrucosa Lamouroux, and two new species, J. minuta and J. parva. These species are segregated primarily on vegetative characters pertaining to fronds, intergenicula, branching, medullary organisation, and substrate preference, with reproductive features used in some cases. Four of the species are, as far as known, endemic to southern Australia: J. minuta, J. pawa, J. pulchella, and J. pusilla. Jania minuta and J. rnicrarthrodia have evolved a unique short-segmented morphology, with intergenicula containing only one or two tiers of medullary cells each. Jania micrarthrodia is a common and conspicuous epiphyte and variable in morphology depending on degree of water movement. In J. minuta, tetrasporangia are replaced by unusual sporangia, each comprised of a large two-nucleate cell, bracketed by small, uninucleate apical and basal cells. This species also forms distinctive multicellular propagules. Jania parva has delicate fronds with dichotomies that tend to diverge widely; only bisporangial and gametangial plants have been found. Jania pulchella has two types of intergenicula, 'janioid' intergenicula which in fertile plants contain conceptacles, and basal compressed and lobed 'cheilosporoid' intergenicula; it is transferred from Cheilosporum pulchellum Harvey. Jania pusilla is usually epiphytic on Cystophora spp., and has small fronds with broad intergenicula. Jania verrucosa, the most robust species, forms dense tufts on low intertidal rocks in southern Australia and in other subtropical or temperate regions.

Fungi in neotropical epiphyte roots

Roots of thirty-eight Ecuadoran vascular epiphytes, representing eleven angiosperm families, were examined for the presence of symbiotic microorganisms. Most orchid roots contained fungal endophytes like those that regularly infect terrestrial counterparts. Hyphae were also common in and on nonorchid roots, but assignments of these relationships to known mycorrhizal morphologies was not possible in all cases. Evidence of vesicular-arbuscular mycorrhizae (VAM) existed in a number of subjects while in Ericaceae and Campanulaceae a fungal association similar to the demateaceous surface fungi (DSF) described for alpine and prarie plants was usually present. Some associations were characterized by multicellular propagules on root surfaces. The significance of these findings and the factors likely to influence occurrence and consequences of root-fungus mutualisms in tropical forest canopies are discussed. Facts and considerations that could aid future inquiry on these systems are provided.

The genus Cristulariella

The generic description of Cristulariella is emended and the fungus C. depraedans is redescribed. Both C. depraedans and C. pyramidalis are characterized by multicellular propagules which are distinct from the phialides each produces in culture. Cristulariella is not a synonym of Myrioconium, but the combination M. depraedans (Cooke) von Arx, referring to the phialides, may be legitimate. Cristulariella depraedans is reported on Acer circinatum and Aruncus sylvester from British Columbia and on Acer pennsylvanicum, A. rubrum, A. saccharum, and A. spicatum from Ontario.