Symbiotic Harpellales (Trichomycetes) in Tasmanian aquatic insects

Surveys for symbiotic fungi in the guts of aquatic insect larvae (Trichomycetes: Harpellales) in Tasmania, Australia, resulted in the discovery of four new species: two in Gripopterygidae (Plecoptera) nymphs, Plecopteromyces leptoperlarum and P. trinotoperlarum, and two associated with Diptera larvae, Smittium magnosporum in Thaumaleidae and Stachylina dolichospora in Chironomidae. Previously described species of Harpellales from other localities are reported and new host records summarized. A key to all Tasmanian species of Harpellales is provided.     

Prevalence of Harpellales from Chironomidae larvae in phytotelmata from punta Lara Forest, Argentina

Harpellales (Zygomycota: Trichomycetes) fungi are cosmopolitan obligate inhabitants of the gut of immature insects. A biweekly survey of gut fungi associated with chironomid (Chironomidae: Diptera) larvae living in the impounded water from Eryngium cabrerae (Apiaceae) phytotelmata from Punta Lara forest, Argentina, was done Jan 2003-Dec 2004. Two species of Harpellales were associated with chironomid larvae, Smittium phytotelmatum in the hindgut of Polypedilum sp. and Stachylina lentica in the midgut of both Polypedilum sp. and Metriocnemus eryngiotelmatus. No statistically significant differences were recorded in the prevalence of these Harpellales between seasons. Environmental variables (temperature, rainfall and relative humidity), impounded water volume, pH and chironomid larval density did not have an effect on the prevalence of the Trichomycetes.     

Trichomycetes (Zygomycota) in the digestive tract of arthropods in Amazonas, Brazil

Eight species of Harpellales and three species of Eccrinales (Zygomycota: Trichomycetes) were found associated with the digestive tract of arthropods from terrestrial and aquatic environments in the central Amazon region of Brazil. New species of Harpellales include: Harpella amazonica, Smittium brasiliense, Genistellospora tropicalis in Simuliidae larvae and Stachylina paucispora in Chironomidae larvae. Axenic cultures of S. brasiliense were obtained. Probable new species of Enterobryus (Eccrinales), Harpella, and Stachylina (Harpellales) are described but not named. Also reported are the previously known species of Eccrinales, Passalomyces compressus and Leidyomyces attenuatus in adult Coleoptera (Passalidae), and Smittium culisetae and Smittium aciculare (Harpellales) in Culicidae and Simuliidae larvae, respectively. Comments on the distribution of some of these fungi and their hosts in the Neotropics are provided.     

Life history strategies of cladocerans: comparisons of tropical and temperate taxa

We review recent works on different life history variables of cladoceran taxa in tropical and temperate freshwater bodies, comparing the strategies that cladocerans have evolved to adapt to contrasting environmental conditions in the two geographical regions. These life-history parameters relate to age and size at maturity, survival, fecundity, life-expectancy at birth, lifespan, gross, and net reproductive rates, generation time, the rate of population increase, peak population density and day of peak abundance. We also discuss the role of photoperiod and temperature on some of these life history parameters. We found a general paucity of experimental work and field data in tropics on cladocerans. There is very limited information on the few Daphnia species found in the tropics. The misconception of low species diversity of cladocerans in the tropics arose due to several reasons including lack of extensive and intensive field collections. Higher water temperatures apparently promote permanent infestation of tropical waters with toxic cyanobacteria, which reduce the zooplankton diversity. In addition to higher temperatures in the tropics, the year-round high predation pressure of planktivorous fish probably causes the tropical species, particularly in pelagic habitats, to reach maturity earlier (< 3 days) than in temperate regions. Species of Daphnia in temperate regions are particularly adapted to living at food concentrations that are much lower and seasonably more variable than those for tropical genera such as Diaphanosoma. This is further corroborated by the more than an order of magnitude higher threshold food concentration (TFC) for tropical Cladocera than for their temperate counterparts. Fecundity patterns differ between tropical and temperate cladoceran taxa: cultured under optimal temperature regimes, tropical taxa have fewer eggs than temperate species of a comparable body size. Predation pressure may act differently depending on the size of the cladoceran neonates and thus on their population size structure. Global warming and climate changes seem to affect the behaviour (migration), distribution, and abundance of cladocerans. Apparently, in direct response to these changes, the possibility of encountering the tropical cladocerans in the northern, temperate hemisphere (bioinvasions) is on the rise.     

Dacryodiomyces, a new genus of Harpellales in Chironomidae larvae

A new genus of gut fungus in the Harpellales (Trichomycetes) with the type species Dacryodiomyces oklahomensis, found in Chironomidae larvae, is described from northeastern Oklahoma, USA. The most distinguishing characters are the elongate-ovoid zygospores attached to their zygosporophore at one end (Type IV), together with trichospores bearing a collar and a single appendage.     

A new species of Legeriomyces and other Harpellales reported for the first time in larval insects from Hungary

Trichomycetes from the guts of aquatic insects have been surveyed for the first time in Hungary. Legeriomyces hungaricus sp. nov. is described along with two new geographic records, L. ramosus and Stachylina grandispora, all of them Harpellales (Kickxellomycotina). The new species is distinguished from others by having smaller zygospores and a characteristic bell-shaped (campanulate) holdfast, unknown so far in other species of Legeriomyces. An unidentified species of Paramoebidium was also observed along with L. ramosus in nymphs of Baetis rhodani (Ephemeroptera). This preliminary report adds to the existing data on gut fungi and we hope will encourage further research on these cryptic endosymbionts in Hungary and its vicinity.     

Trifoliellum bioblitzii, a new genus of trichomycete from mayfly nymphs in Nova Scotia, Canada

Trichomycetes are an ecological group of fungi and protists that colonize the gut lining of invertebrates in aquatic and moist terrestrial habitats. The diversity of this group appears to be high with many new species discovered each year. A new genus of fungal trichomycete, Trifoliellum (Harpellales), is described here with the type species T. bioblitzii. This genus is characterized by having unique, trefoil-shaped asexual spores (trichospores). Another new species, Legeriosimilis halifaxensis, also is described from the same mayfly host, Eurylophella temporalis, collected from the same site near Halifax, Nova Scotia.     

Harpellales in the digestive tracts of Ephemeroptera and Plecoptera nymphs from Veracruz, Mexico

This is the first report of Harpellales (Zygomycota) from Mexico, including herein only the endosymbiotic species of gut fungi in the digestive tracts or shed exuviae of Plecopteran and Ephemeropteran nymphs. Four new species are described: Allantomyces zopilotei, Bojamyces olmecensis, Gauthier-omyces viviparus and Graminella ophiuroidea. Among previously known Harpellales, Lancisporomyces nemouridarum and Zygopolaris ephemeridarum are southern range extremes and new records for Mexico. All species are illustrated and discussed relating to biogeographic implications of the new reports from Mexico, as well as the particular environmental circumstances of the Harpellales in the tropics.     

Latitude, elevational climatic zonation and speciation in New World vertebrates

Many biodiversity hotspots are located in montane regions, especially in the tropics. A possible explanation for this pattern is that the narrow thermal tolerances of tropical species and greater climatic stratification of tropical mountains create more opportunities for climate-associated parapatric or allopatric speciation in the tropics relative to the temperate zone. However, it is unclear whether a general relationship exists among latitude, climatic zonation and the ecology of speciation. Recent taxon-specific studies obtained different results regarding the role of climate in speciation in tropical versus temperate areas. Here, we quantify overlap in the climatic distributions of 93 pairs of sister species of mammals, birds, amphibians and reptiles restricted to either the New World tropics or to the Northern temperate zone. We show that elevational ranges of tropical- and temperate-zone species do not differ from one another, yet the temperature range experienced by species in the temperate zone is greater than for those in the tropics. Moreover, tropical sister species tend to exhibit greater similarity in their climatic distributions than temperate sister species. This pattern suggests that evolutionary conservatism in the thermal niches of tropical taxa, coupled with the greater thermal zonation of tropical mountains, may result in increased opportunities for allopatric isolation, speciation and the accumulation of species in tropical montane regions. Our study exemplifies the power of combining phylogenetic and spatial datasets of global climatic variation to explore evolutionary (rather than purely ecological) explanations for the high biodiversity of tropical montane regions.     

Harpellales (Trichomycetes); mycobionts of insecta

Summary

Species of fungi assigned to the Harpellales, Trichomycetes, occur obligately associated with Insecta. Their possession of monosporous merosporangia (trichospores), zygospores, and crosswalls flared around a plugged central pore augurs for close phyletic affinity with the Kickxellales (Zygomycota). Somatic and reproductive thalli occur attached to the cuticle lining the mid- and hindguts of aquatic dipteran larvae and hindguts of ephemeropteran and plecopteran nymphs. This stage is considered commensalistic. In some species a pathogenic stage of the Harpellales is associated with the ovaries and reduces fecundity. At oviposition fungal spores are deposited by the imago at the sites of new larval populations and provide the primary inoculum.     

Large-scale phylogenetic analyses reveal the causes of high tropical amphibian diversity

Many groups show higher species richness in tropical regions but the underlying causes remain unclear. Despite many competing hypotheses to explain latitudinal diversity gradients, only three processes can directly change species richness across regions: speciation, extinction and dispersal. These processes can be addressed most powerfully using large-scale phylogenetic approaches, but most previous studies have focused on small groups and recent time scales, or did not separate speciation and extinction rates. We investigate the origins of high tropical diversity in amphibians, applying new phylogenetic comparative methods to a tree of 2871 species. Our results show that high tropical diversity is explained by higher speciation in the tropics, higher extinction in temperate regions and limited dispersal out of the tropics compared with colonization of the tropics from temperate regions. These patterns are strongly associated with climate-related variables such as temperature, precipitation and ecosystem energy. Results from models of diversity dependence in speciation rate suggest that temperate clades may have lower carrying capacities and may be more saturated (closer to carrying capacity) than tropical clades. Furthermore, we estimate strikingly low tropical extinction rates over geological time scales, in stark contrast to the dramatic losses of diversity occurring in tropical regions presently.     

Phylogenetic tests of community assembly across regional to continental scales in tropical and subtropical rain forests

Aim To measure and quantify community phylogenetic structure to evaluate how evolutionary, ecological and biogeographic processes have shaped the distributions and assemblage of tropical and subtropical rain forest tree species across local, regional and continental scales. Location Australia. Methods We used 596 assemblage‐level samples and 1137 woody species in rain forest vegetation sampled across two latitude regions (tropics and sub‐tropics) and five distinct areas. Based on this dataset, we obtained and analysed species‐level trait values (for leaf size, seed size, wood density and maximum height at maturity), measures of community phylogenetic structure and species turnover across space (beta) and evolutionary time (phylobeta). Results Phylobeta values showed that at continental scales (i.e. across the latitude regions combined) species replacement, as turnover in assemblages through time, was by more phylogenetically distant (i.e. less closely related) taxa. Within latitude regions replacement was by more closely related taxa. Assemblages of species were more phylogenetically clustered across the whole phylogeny (net relatedness index) and with respect to more recent divergences (nearest related taxon index) where the effects of historic disturbance (climatic oscillations) had been greater, and less clustered in long‐term stable (refugial) locations. Local species composition in the stable wet tropics showed significant phylogenetic evenness, but there was no corresponding evenness in distributions of the ecological traits measured. Main conclusions Despite a shared evolutionary and biogeographic history, the two regions diverged from each other before the development of internal divergences. Phylogenetic evenness is more evident in long‐term stable habitats (refugia) where species interact in conserved niches. Phylogenetic clustering is more evident where recolonization of more highly disturbed areas from historically reduced species pools reflects filtering of species into phylogenetically preferred habitats.     

Ecological Diversity in South American Mammals: Their Geographical Distribution Shows Variable Associations with Phylogenetic Diversity and Does Not Follow the Latitudinal Richness Gradient

The extent to which the latitudinal gradient in species richness may be paralleled by a similar gradient of increasing functional or phylogenetic diversity is a matter of controversy. We evaluated whether taxonomic richness (TR) is informative in terms of ecological diversity (ED, an approximation to functional diversity) and phylogenetic diversity (AvPD) using data on 531 mammal species representing South American old autochthonous (marsupials, xenarthrans), mid-Cenozoic immigrants (hystricognaths, primates) and newcomers (carnivorans, artiodactyls). If closely related species are ecologically more similar than distantly related species, AvPD will be a strong predictor of ED; however, lower ED than predicted from AvPD may be due to species retaining most of their ancestral characters, suggesting niche conservatism. This pattern could occur in tropical rainforests for taxa of tropical affinity (old autochthonous and mid-Cenozoic immigrants) and in open and arid habitats for newcomers. In contrast, higher ED than expected from AvPD could occur, possibly in association with niche evolution, in arid and open habitats for taxa of tropical affinity and in forested habitats for newcomers. We found that TR was a poor predictor of ED and AvPD. After controlling for TR, there was considerable variability in the extent to which AvPD accounted for ED. Taxa of tropical affinity did not support the prediction of ED deficit within tropical rainforests, rather, they showed a mosaic of regions with an excess of ED interspersed with zones of ED deficit within the tropics; newcomers showed ED deficit in arid and open regions. Some taxa of tropical affinity showed excess of ED in tropical desert areas (hystricognaths) or temperate semideserts (xenarthrans); newcomers showed excess of ED at cold-temperate latitudes in the Northern Hemisphere. This result suggests that extreme climatic conditions at both temperate and tropical latitudes may have promoted niche evolution in mammals.     

Fungal symbionts (Harpellales) in Norwegian aquatic insect larvae

Collections of aquatic insect larvae in Norway, over a 40 d period in May and Aug 2002, resulted in finding more than 25 species and one new genus of Harpellales (Trichomycetes). Nine new fungal symbionts are described and named: Ephemerellomyces aquilonius (a new monotypic genus), Glotzia stenospora and Legeriosimilis europaeus in mayfly nymphs (Ephemeroptera); Genistelloides amplispora and G. communis in stonefly nymphs (Plecoptera); and Smittium biforme, Sm. precipitiorum, Stachylina acutibasilaris and St. lentica in midge larvae (Diptera: Chironomidae). Two possibly new species of Smittium in Chironomidae larvae are described but not formally named. New hosts and biogeographical distributions are recorded for 14 previously described species, including the rare occurrence of Smittium simulii in mosquito larvae.     

Secondary spore formation in <Emphasis Type="Italic">Orchesellaria mauguioi</Emphasis> (Asellariales,Trichomycetes) and its taxonomic and ecological implications

Orchesellaria (Orc.) mauguioi (Asellariales) was detected from the hindguts of Isotomurus palustris (Collembola, Hexapoda) collected in Japan. The secondary spore formation on the exuviae of its host is described. When the host molted, its exoskelton including the ectoderm-originated hindgut cuticle to which Orc. mauguioi mycelia attaches was shed. Arthrospores of Orc. mauguioi germinated and penetrated the molt skin and produced secondary spores terminally. The secondary spore is a narrowly ovoid monosporangious sporangium accompanied by a capitate-lageniform terminal cell; these fall off together as a dispersive unit. The terminal cell is sterile and bears one to three fine filamentous extensions seven times as long as the length of the cell. In contrast to the appendages produced endogenously by other harpellids, the filament is produced exogenously and is similar to those of the genus Orphella (Harpellales). The taxonomic and ecological implications of the secondary spore formation of Orc. mauguioi are discussed by comparison with those of other Trichomycetes.     

Climatic zonation drives latitudinal variation in speciation mechanisms

Many groups of organisms show greater species richness in the tropics than in the temperate zone, particularly in tropical montane regions. Forty years ago, Janzen suggested that more limited temperature seasonality in the tropics leads to greater climatic zonation and more climatic barriers to organismal dispersal along elevational gradients in the tropics relative to temperate regions. These factors could lead to differences in how species arise in tropical versus temperate regions and possibly contribute to greater tropical diversity. However, no studies have compared the relationships among climate, elevational distribution and speciation in a group inhabiting both tropical and temperate regions. Here, we compare elevational and climatic divergence among 30 sister-species pairs (14 tropical, 16 temperate) within a single family of salamanders (Plethodontidae) that reaches its greatest species richness in montane Mesoamerica. In support of Janzen's hypothesis, we find that sister species are more elevationally and climatically divergent in the tropics than in the temperate zone. This pattern seemingly reflects regional variation in the role of climate in speciation, with niche conservatism predominating in the temperate zone and niche divergence in the tropics. Our study demonstrates how latitudinal differences in elevational climatic zonation may increase opportunities for geographical isolation, speciation and the associated build-up of species diversity in the tropics relative to the temperate zone.     

Minimal effects of latitude on present-day speciation rates in New World birds

The tropics contain far greater numbers of species than temperate regions, suggesting that rates of species formation might differ systematically between tropical and non-tropical areas. We tested this hypothesis by reconstructing the history of speciation in New World (NW) land birds using BAMM, a Bayesian framework for modelling complex evolutionary dynamics on phylogenetic trees. We estimated marginal distributions of present-day speciation rates for each of 2571 species of birds. The present-day rate of speciation varies approximately 30-fold across NW birds, but there is no difference in the rate distributions for tropical and temperate taxa. Using macroevolutionary cohort analysis, we demonstrate that clades with high tropical membership do not produce species more rapidly than temperate clades. For nearly any value of present-day speciation rate, there are far more species in the tropics than the temperate zone. Any effects of latitude on speciation rate are marginal in comparison to the dramatic variation in rates among clades.