Isolation of polymorphic microsatellite markers in the sub‐Saharan tree,Acacia (Senegalia) mellifera (Fabaceae: Mimosoideae)

We isolated 11 polymorphic microsatellite markers from Acacia mellifera, a savannah woodland tree in sub‐Saharan Africa and southern Arabia. The loci were screened for polymorphism using 48 Kenyan individuals. Allelic diversity ranged from three to 19 per locus and the polymorphic information content varied from 0.287 to 0.893. These loci will be useful in studies of genetic structure, gene flow and breeding systems.     

A GIANT LUCINID BIVALVE FROM THE EOCENE OF JAMAICA – SYSTEMATICS, LIFE HABITS AND CHEMOSYMBIOSIS (MOLLUSCA: BIVALVIA: LUCINIDAE)

Abstract:  The giant bivalve Lucina megameris Dall, 1901 , from the late Eocene White Limestone Group of Jamaica and by far the largest known species of the family Lucinidae, is placed in a new genus Superlucina . Apart from its large size, with a shell height exceeding 310 mm, it is distinguished from other genera, such as Pseudomiltha and Eomiltha by external shell characters and the extremely long and narrow, anterior adductor muscle scar. Features preserved on internal moulds suggest that, in common with living Lucinidae, S. megameris was chemosymbiotic with sulphide – oxidizing bacteria housed in the gills. Palaeoenvironmental evidence suggests a habitat in oligotrophic, shallow waters, probably in seagrass beds, with an associated molluscan fauna including large cardiids that may have been photosymbiotic. Superlucina is considerably larger than any living lucinid that range in size from 3 to 150 mm with most encompassed within 5–30 mm. From the Jurassic onwards, a few other large lucinids are known from cold seep sites, with several other records from possible shallow water seagrass beds.     

Molecular phylogenetic biodiversity assessment of arctic and boreal ectomycorrhizal Lactarius Pers. (Russulales; Basidiomycota) in Alaska, based on soil and sporocarp DNA

Despite the critical roles fungi play in the functioning of ecosystems, especially as symbionts of plants and recyclers of organic matter, their biodiversity is poorly known in high-latitude regions. In this paper, we discuss the molecular diversity of one of the most diverse and abundant groups of ectomycorrhizal fungi: the genus Lactarius Pers. We analysed internal transcribed spacer rDNA sequences from both curated sporocarp collections and soil polymerase chain reaction clone libraries sampled in the arctic tundra and boreal forests of Alaska. Our genetic diversity assessment, based on various phylogenetic methods and operational taxonomic unit (OTU) delimitations, suggests that the genus Lactarius is diverse in Alaska, with at least 43 putative phylogroups, and 24 and 38 distinct OTUs based on 95% and 97% internal transcribed spacer sequence similarity, respectively. Some OTUs were identified to known species, while others were novel, previously unsequenced groups. Non-asymptotic species accumulation curves, the disparity between observed and estimated richness, and the high number of singleton OTUs indicated that many Lactarius species remain to be found and identified in Alaska. Many Lactarius taxa show strong habitat preference to one of the three major vegetation types in the sampled regions (arctic tundra, black spruce forests, and mixed birch-aspen-white spruce forests), as supported by statistical tests of UniFrac distances and principal coordinates analyses (PCoA). Together, our data robustly demonstrate great diversity and nonrandom ecological partitioning in an important boreal ectomycorrhizal genus within a relatively small geographical region. The observed diversity of Lactarius was much higher in either type of boreal forest than in the arctic tundra, supporting the widely recognized pattern of decreasing species richness with increasing latitude.     

Patterns in freshwater diatom taxonomic distinctness along an eutrophication gradient

1. A variety of species richness measures have been used to assess the effects of environmental degradation on biodiversity. Such measures can be highly influenced by sample size, sampling effort, habitat type or complexity, however, and typically do not show monotonic responses to human impact. In addition to being independent of the degree of sampling effort involved in data acquisition, effective measures of biodiversity should reflect the degree of taxonomical relatedness among species within ecological assemblages and provide a basis for understanding observed diversity for a particular habitat type. Taxonomic diversity or distinctness indices emphasize the average taxonomic relatedness (i.e. degree of taxonomical closeness) between species in a community. 2. Eutrophication of freshwater ecosystems, mainly due to the increased availability of nutrients, notably phosphorus, has become a major environmental problem. Two measures of taxonomic distinctness (Average Taxonomic Distinctness and Variation in Taxonomic Distinctness) were applied to surface sediment diatoms from 45 lakes across the island of Ireland to examine whether taxonomic distinctness and nutrient enrichment were significantly related at a regional scale. The lakes span a range of concentrations of epilimnic total phosphorus (TP) and were grouped into six different types, based on depth and alkalinity levels, and three different categories according to trophic state (ultra‐oligotrophic and oligotrophic; mesotrophic; and eutrophic and hyper‐eutrophic). 3. The taxonomic distinctness measures revealed significant differences among lakes in the three different classes of trophic state, with nutrient‐rich lakes generally more taxonomically diverse than nutrient‐poor lakes. This implies that enrichment of oligotrophic lakes does not necessarily lead to a reduction in taxonomic diversity, at least as expressed by the indices used here. Furthermore, taxonomic distinctness was highly variable across the six different lake types regardless of nutrient level. 4. Results indicate that habitat availability and physical structure within the study lakes also exert a strong influence on the pattern of taxonomic diversity. Overall the results highlight problems with the use of taxonomic diversity measures for detecting impacts of freshwater eutrophication based on diatom assemblages.     

A unique mode of parasitism in the conifer coral tree Parasitaxus ustus (Podocarpaceae)

Almost all parasitic plants, including more than 3000 species, are angiosperms. The only suggested gymnosperm exception is the New Caledonian conifer, Parasitaxus ustus , which forms a bizarre graft-like attachment to the roots of another conifer Falcatifolium taxoides . Yet, the degree of resource dependence of Parasitaxus on Falcatifolium has remained speculative. Here we show that Parasitaxus is definitively parasitic, but it displays a physiological habit unlike any known angiosperm parasite. Despite possessing chloroplasts, it was found that the burgundy red shoots of Parasitaxus lack significant photosynthetic electron transport. However unlike non-photosynthetic angiosperm parasites (holoparasites), tissues of Parasitaxus are considerably enriched in ¹³carbon relative to its host. In line with anatomical observations of fungal hyphae embedded in the parasite/host union, stable carbon isotopic measurements indicate that carbon transport from the host to Parasitaxus most likely involves a fungal partner. Therefore, Parasitaxus parallels fungus-feeding angiosperms (mycoheterotrophs) that steal carbon from soil mycorrhizal fungi. Yet with its tree-like habit, association with fungi residing within the host union, high stomatal conductance, and low water potential, it is demonstrated that Parasitaxus functions unlike any known angiosperm mycoheterotroph or holoparasite. Parasitaxus appears to present a unique physiological chimera of mistletoe-like water relations and fungal-mediated carbon trafficking from the host.     

Genetic assessment of species boundaries in the North American Daphnia longispina complex (Crustacea: Daphniidae)

Species boundaries in the North American Daphnia longispina group have proved difficult to establish on the basis of morphology alone. This confusion may be due to hydridization, phenotypic plasticity or the existence of sibling species. We therefore used genetic analysis to delineate species boundaries by examining 27 North American populations belonging to the longispina complex for variation at 15–26 allozyme loci. The populations consisted of Daphnia thorata from two western sites and two eastern sites, Daphnia galeata mendotae from its type location and seven sites across its range, and Daphnia rosea from eight temperate and seven arctic sites. Two populations from the Eurasian longispina complex were also included for reference. Populations assigned to D. galeata mendotae formed a genetically cohesive group, whereas a genetic dichotomy was found between temperate and arctic D. rosea , suggesting that this taxon includes two species. Genetic analysis also confirmed the distinctness of western D. thorata from other members of the longispina group. Unexpectedly, eastern populations resembling D. thorata were genetically more similar to temperate D. rosea than to any helmeted species ( D. galeata, Daphnia hyalina or D. thorata ). Our results suggest that the helmet character is a poor indicator of phylogenetic relationships, as the genetic ability to produce this feature has been lost or acquired several times in the evolution of the longispina group.     

Goldfish Tyrosinase Related Protein I (TRP-1): Deduced Amino Acid Sequence From cDNA and Comments on Structural Features

Previous workers have shown that mammals have tyrosinase and tyrosinase related proteins (TRPs) that share common structural domains, all of which are not present in microbial tyrosinases. We report here the deduced amino acid sequence of a TRP from fish that is highly homologous to mammalian TRP-1. Examination of the structures of these vertebrate tyrosinases and TRPs shows that, aside from the conserved cysteine-rich and histidine-rich domains previously noted, there are a large number of conserved prolines and glycines, leading to an abundance of turns and few conserved helical regions. These tyrosinases and TRP-1s also have in their cytosolic tails a consensus sequence that is not present in any other protein. It is proposed that this sequence may participate in directing these proteins to the melanosomes.