A synthesis of the accumulated knowledge on myxomycetes recorded from the Neotropical region is presented in this paper. The biodiversity of these microorganisms in the Neotropics has been underestimated, and this paper shows that half the known species in the world have been recorded from the region. The monograph by M.L. Farr, for the series Flora Neotropica, published in 1976, has been taken as a baseline. The records produced after this date, some older obscure records, and data from recently published catalogues, monographs and other papers have been incorporated. The information is presented in a table format by species and countries. Species names are listed with synonyms that have been used in Neotropical literature and nomenclature has been updated. A comprehensive list of references by country has been included. A characteristic assemblage of myxomycetes from the Neotropics has been identified. The richness of myxobiota in different countries has been evaluated, and gaps in current information and unexplored areas have become evident from the results. Use of the compiled information to direct conservation plans, and to serve as a starting point to establish and develop future strategies for the study of myxomycetes in this area of the world, is discussed. The importance of prioritizing this research on microorganismal biodiversity, in view of accelerated habitat destruction, is stressed. Se realiza una síntesis sobre el conocimiento actual de los Myxomycetes en el Neotrópico. La biodiversidad de estos microorganismos en la región neotropical ha sido subestimada, pero este trabajo demuestra que la mitad de las especies conocidas en el mundo se han citado de esta región. La monografía que M.L. Farr publicó en 1976, para la serie Flora Neotrópica, se ha tomado como punto de partida para la realización de este trabajo. A ella se han incorporado las citas publicadas después de esta fecha, algunas más antiguas pero raras, y datos de catálo-gos, monografías y otros trabajos recientes. La información se presenta en una tabla de doble entrada, por orden alfabético de especies y por países. La nomenclatura de las especies se ha actualizado y se han añadido los sinónimos con los que han sido citadas en la bibliografía neotropical. También se incluye una lista de referencias bibliográficas por países. Se ha podido identificar un conjunto de especies de Myxomycetes que, por su abundancia de citas en los países neotropicales, parecen características de la región. Se evalúa, por países, la riqueza de su mixobiota y se ponen de manifiesto la falta de información y los escasos estudios que se han llevado a cabo en determinados territorios de esta región biogeográfica. Se discute y comenta el uso que se puede dar a esta información recopilada, como punto de partida para establecer y desarrollar estrategias de estudio sobre los Myxomycetes en esta parte del mundo. Por último, se llama la atención sobre la importancia y prioridad que se debe dar a la investigación sobre biodiversidad de microorganismos, a la hora de valor...

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Results obtained from the first survey for myxomycetes in the hyperarid areas of Peru are reported. Sampling over three consecutive years was carried out at 96 localities between 0 and 1500 m elevation. A total of 78 species from 23 genera in all 6 myxomycete orders were determined from 723 collections of myxomycetes. One new species, Didymium peruvianum, is described, 2 species new to the Neotropics, 4 new records for South America and 41 additional new species for Peru are reported, increasing the country catalogue by over 50%. Results show that arid areas are rich in myxomycetes, and that each area has a unique species assemblage. Endemic plants had a particular relevance as myxomycete substrates. The predominance of the order Physarales in arid areas is reinforced, and the ecological importance of coastal fogs (garúas) is evident from the results. Comments are included on interesting or rare collections, as are SEM micrographs of several species and statistical evaluation of the results. Se dan a conocer los resultados del primer estudio realizado sobre los Myxomycetes de las regiones hiperáridas de Perú. El muestreo, realizado en tres años consecutivos, se ha llevado a cabo en 96 localidades situadas entre 0 y 1500 m de altitud. En total se obtuvieron 723 colecciones de mixomicetes, pertenecientes a 6 órdenes, 23 géneros y 78 especies. Se describe una nueva especie, Didymium peruvianum, 2 especies se citan por primera vez en el Neotrópico, 4 son nuevos registros para América del Sur y 41 especies más son nuevos registros para Perú, con lo que el catálogo del país se incrementa en un 50%. Los resultados muestran que las zonas áridas son ricas en mixomicetes, y que cada area tiene un conjunto único de especies. Las plantas endémicas, dominantes en estos ambientes, tuvieron una relevancia especial como sustrato para los myxomycetes. Se pone de manifiesto el predominio de los representantes del órden Physarales en las zonas áridas, lo que refuerza resultados previos, así como la importancia ecológica de las nieblas costeras (garúas). Se incluyen comentarios de las especies más interesantes o poco comunes, así como fotografías realizadas con microscopio electrónico de barrido, y una evaluación estadística de los resultados.

A new stipitate species of myxomycete of the genus Licea is described based on material from arid areas in Argentina and Chile. It was isolated from moist chamber cultures and found fruiting on field collections, usually on the same substrate, Puya sp. (Bromeliaceae). It differs from all described species in the genus in that it has stipitate sporocarps with dehiscence by defined preformed platelets and a smooth inner peridial surface. The new species has polyhedral, yellow spores with a uniform thick spore wall and dense warts except on irregularly dispersed raised bands with fewer warts, visible by SEM, an ornamentation not previously observed in the genus. Life-cycle events are described and illustrated, from germination to sporulation, based on moist chamber and agar cultures. The morphology of the myxomycete specimens was examined with scanning electron microscopy and light microscopy, and both light and SEM micrographs of relevant details are included.

A new species of myxomycete, Didymium umbilicatum, isolated from the bark of Agavaceae, is described from arid zones of Mexico. This species was obtained from moist chamber cultures of Yucca spp. bark, collected in four different years from two states (Puebla and Querétaro) in central Mexico and found in the field from Hidalgo, Oaxaca and Puebla on the dead remains of Agave sp. The new species has small, flat, white sporocarps or short plasmodiocarps, 0.2-1.3 mm diam, and 0.15-0.4 mm tall. They are sessile on a reduced base or have a short, calcareous pale stalk and warted spores, warts fused in an irregular subreticulum by SEM. It is the sixth species of Didymium recently described from arid areas. The stability of the taxonomic characters of the species was confirmed by spore-to-spore culture on agar. Life cycle events are described from germination to sporulation. The morphology of the myxomycete specimens was examined with scanning electron microscopy and light microscopy, and micrographs of relevant details are included.

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A new species of Physarum (Myxomycetes), Physarum atacamense is described in this paper, and details are provided on its life cycle as observed in spore-to-spore culture in agar. The new species was collected during studies of the Atacama Desert in Chile. It has been collected directly in the field and isolated in moist chamber cultures prepared with material from an endemic cactus. The combination of characters that make this species unique in the genus are its large fusiform nodes of the capillitium, its long, bicolored stalk and the very dark brown and densely warted angular spores. The morphology of specimens of this myxomycete was examined with scanning electron microscopy and light microscopy, and micrographs of relevant details and life cycle stages are included in this paper. The importance of resistant stages in the life cycle of this myxomycete is stressed, and the close association of this myxomycete with its plant substrates is discussed.

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