New small dictyostelids from seasonal rainforests of Central America

Abstract

Ten small dictyostelids isolated from samples collected from the surface humus layer of seasonal rainforests of Belize and Guatemala were studied morphologically, and nine were found to represent distinct species, all with an average height of < 2 mm (0.5-3.5 mm). Although their fruiting bodies (sorocarps) closely resemble one another, the nine species differ in their patterns of aggregation, stream pattern, branching development, formation of microcysts, spore shape, presence or absence of spore granules and their distribution, as well as in the shapes and behavior of their sorogens and myxamoebae. These stable morphological features were sufficient to recognize nine new species of small dictyostelids, one with two varieties. SSU rDNA sequences were generated for all these new isolates, and phylogenetic analyses of these sequences show these new isolates belong to Dictyostelid group 3. As a result of this and other recent studies, the concept of what constitutes a species in the dictyostelids has become much more restricted and well defined, in as much as some of the morphological and behavioral patterns now being observed were overlooked in the past. The extent, flow direction and conformation of streaming within the group varies from simple aggregation mounds with no streams to short streams, to somewhat longer streams and finally to well developed streams. Each of these is characterized by a particular set of distinguishing features.

Four New Species of Dictyostelids from Soil Systems in Northern Thailand

“…A similar situation was reported by Cavender et al [ 18 ] for several morphologically similar species collected in a single small collecting site located at higher elevations the Great Smoky Mountains National Park in the United States. As a general observation, the species composition and diversity of the assemblage of dictyostelids in northern Thailand are relatively similar to what has been reported in previous studies of both the dictyostelids of Southeast Asia [ 19 ] and the American tropics [ 15 ]. In both regions, those species that appear to be endemic are rare.…”

“…In little more than 50 years, the number of known species of dictyostelids has increased from about 40 to more than 160. Surveys for these organisms performed in regions of the world where previous investigations were either limited or completely lacking [ 14 , 15 , 16 , 17 ] largely account for this dramatic increase. However, more intensive studies in areas where previous records of dictyostelids already existed have yielded unexpected results.…”

Additional new species suggest high dictyostelid diversity on Madagascar

“…Distinguishing features: This species has a wide temperature tolerance, fruiting when grown at temperatures ranging from 15 to 30 C, but the optimal temperature for growth is 27-29 C. Culture remains alive for 3-4 wk without major changes, and sori remain hydrated and do not collapse for a relatively long period of time, then they slowly dry out. This species has affinities with other small species in the genus Raperostelium (formerly "Group 3 dictyostelids" sensu Romeralo et al 2011) described from Central America by Cavender et al (2013). It has radiate streaming aggregations as well as mound-like aggregations.…”

“…These three species are described from different localities around the world: R. monochasioides was described from the tropical Australasian island of New Guinea (Hagiwara 1973) and has since been found in multiple localities, including Japan, Mexico, and Ukraine (Cavender et al 2012;Liu and Li 2010). R. australe was described from the farsouth latitudes of New Zealand (Cavender et al 2002), whereas R. reciprocatum was first recovered in Central America (Cavender et al 2013). All four of these species are relatively small, usually with elliptical spores and prominent polar granules (although R. australe is a partial exception, as it often displays polar granules, but also alongside subpolar, consolidated or irregular granules).…”