Biodiversity of palm fungi in the tropics: are global fungal diversity estimates realistic?

Two questions are addressed: 'How many species of fungi can occur on a single host palm?' and 'What are the implications of this for global estimates of fungal diversity?' Fungal diversity estimates found in the literature are reviewed. Data on the numbers of fungi occurring on the above-ground tissues of six individual palms in the genus Licuala in Australia and Brunei Darussalam (Borneo) are provided. A total of 189 species of fungi were isolated and/or collected from the six palms. In addition, 53 'morphospecies' of mycelia sterilia were isolated, giving a total of 242 taxa from the 2672 isolates/collections made. The three palms in Australia (sampled once) yielded 100 species (each palm supporting an average of 54.7 taxa), while the three palms in Brunei Darussalam (sampled three times) yielded 172 species in total (approximately 111.3 taxa each). The magnitude of global fungal diversity, estimated at 1.5 million species, is discussed. Our results indicate that 33 to 1 would be a more accurate estimate (than 5.7 to 1) of the ratio of host specific fungal to palm species in the tropics. We therefore propose that global estimates of fungal diversity, based on temperate studies, require revision upwards.     

Macromolecular composition of Palaeozoic scolecodonts: insights into the molecular taphonomy of zoomorphs

Dutta, S., Hartkopf‐Fröder, C., Mann, U., Wilkes, H., Brocke, R. & Bertram, N. 2010: Macromolecular composition of Palaeozoic scolecodonts: insights into the molecular taphonomy of zoomorphs. Lethaia, Vol. 43, pp. 334–343. Biogeochemistry and molecular taphonomy of biopolymers of marine zoomorphs are poorly known. In order to obtain insights into this issue we report on the biogeomacromolecular composition of hand‐picked, well‐preserved scolecodonts of Ordovician, Silurian and Devonian age using micro‐Fourier transform infrared (micro‐FTIR) spectroscopy, Curie point pyrolysis‐gas chromatography‐mass spectrometry (Cupy‐GC‐MS) and tetramethylammonium hydroxide (TMAH)‐assisted thermochemolysis‐GC‐MS. The present study reveals that scolecodonts are composed of both aliphatic and aromatic moieties. The micro‐FTIR spectra of scolecodonts are characterized by aliphatic CH_x (3000–2800 and 1460–1450/cm) and CH₃ (1375/cm) absorptions and aromatic C=C (1560–1610/cm) and CH (3050/cm and 700–900/cm) absorptions. The major pyrolysis products from the scolecodonts include aromatic hydrocarbons such as alkylbenzenes, alkylnaphthalenes and alkylphenols. Aliphatic hydrocarbons are represented by a homologous series of n‐alkenes and n‐alkanes. The compounds released upon thermochemolysis with TMAH are saturated and unsaturated fatty acids (as their methyl esters), n‐alkenes/alkanes and aromatic acids (as their methyl esters). No protein/amino acid‐derived compounds have been recognized in the pyrolysates or in the thermochemolysates, and it is concluded that protein/amino acid‐related compounds, which are commonly found in the jaws of extant polychaetes, were destroyed due to diagenetic processes. Obviously, excellent morphological preservation and low thermal alteration are not paralleled by a similar degree of chemical preservation. □Biogeomacromolecules, micro‐FTIR, pyrolysis‐GC‐MS, scolecodonts, thermochemolysis‐GC‐MS.     

A test of Rensch's rule in varanid lizards

In a model group of giant reptiles, we explored the allometric relationships between male and female body size and compared the effects of sexual and fecundity selection, as well as some proximate causes, on macroevolutionary patterns of sexual size dimorphism (SSD). Monitor lizards are a morphologically homogeneous group that has been affected by extreme changes in body size during their evolutionary history, resulting in 14‐fold differences among the body sizes of recent species. Here, we analysed data concerning the maximum and/or mean male and female snout–vent lengths in 42 species of monitor lizard from literary sources and supplemented these data with measurements made in zoos. There was a wide scale of SSD from nearly monomorphic species belonging mostly to the subgenus Odatria and Prasinus group of the Euprepriosaurus to apparently male‐larger taxa. The variable best explaining SSD was the body size itself; the larger the species, the higher the SSD. This pattern agrees with the currently discussed Rensch's rule, claiming that the relationship between male and female body size is hyperallometric, i.e. the allometric exponent of this relationship exceeds unity and thus SSD increases with body size in the case of male‐larger taxa. All our estimates of the reduced major axis regression slopes of this relationship ranged from 1.132 to 1.155. These estimates are significantly higher than unity, and thus unequivocally corroborate the validity of Rensch's rule in this reptilian group. In spite of our expectation that the variation in SSD can be alternatively explained by variables reflecting the strength of sexual selection (presence of male combat), fecundity selection (e.g. clutch size and mass) and/or proximate ecological factors (habitat type), none of these variables had consistent effects on SSD, especially when the data were adjusted to phylogenetic dependence and/or body size. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 293–306.     

Disentangling the impact of demographic factors on population differentiation of an endangered freshwater crayfish (Austropotamobius pallipes) using population density and microsatellite data

1. Habitat fragmentation of stream ecosystems often results in decreased connectivity between populations and lower population sizes. Hence, understanding how habitat fragmentation affects genetic erosion is important for the preservation of freshwater biodiversity, in particular, as small populations suffer from loss of genetic diversity through genetic drift and loss of fitness because of inbreeding, increasing the risk of extinction. 2. Here, we assess the impact of demographic factors on population differentiation in the endangered freshwater crayfish Austropotamobius pallipes by analysing population genetic structure, estimating effective population sizes and comparing levels of polymorphism at five microsatellite loci with density estimates of 10 populations within a small French catchment that has become progressively confined to headwaters over the last six decades. 3. Levels of expected heterozygosity and allelic richness per population were relatively low (0.214–0.396 and 1.6–2.6, respectively). We found strong genetic differentiation between these geographically close populations (F_ST = 0.283), with weak statistical evidence for a pattern of isolation by distance. Estimates of effective population size were low (<150) in most populations, but potentially reached several thousands in three populations. 4. Population density and allelic richness were strongly positively correlated. A robust relationship between population density and heterozygosity values was also noted, but only after discarding two populations for which significant genetic signatures of a recent bottleneck were found; these two populations displayed high expected heterozygosity compared with a very low density. Populations with the highest densities of individuals had the highest effective population size estimates and vice versa. 5. Our results clearly show the importance of demographic factors and genetic drift on A. pallipes populations. Furthermore, analysis of genetic and population density data is a pragmatic and efficient approach to corroborate inferences from genetic data and can be particularly useful in the identification of populations experiencing a bottleneck and therefore in conservation genetics studies aiming at identifying priority populations for conservation.     

Natural occurrence of aflatoxins and ochratoxin a in corn and barley from mazandaran and golestan in north provinces of I. R. Iran

Fourteen barley and nine corn samples, destined for animal feed, collected from Golestan and Mazandaran provinces in the north of Islamic Republic of Iran (I. R. Iran) were analysed for aflatoxins (AF) and ochratoxin A (OA) by high performance liquid chromatography. In corn samples, aflatoxin B₁ (AFB₁) and aflatoxin B₂ (AFB₂) were detected in 8 (88.8%) and 6 (66.6%) samples at a mean level of 15.83 and 2.99 ppb (median 1.72 and 1 ppb), respectively. None of the corn samples contained detectable amounts of aflatoxin G₁ (AFG₁) and aflatoxin G₂ (AFG₂). Only one of the AF-contaminated samples was co-contaminated with OA at a concentration of 0.35 ppb. This is the first report concerning natural occurrence of OA and co-occurrence with AF in corn samples of north of I. R. Iran.     

Life history consequences of larval foraging depth differ between two competing Anopheles mosquitoes

1. Anopheline larvae are surface feeders and allocate most of their time to search for food at the water surface. However, species of the Anopheles gambiae Giles complex may also show bottom feeding. The consequences of this foraging tactic for life history are unknown, yet may be relevant to understand inter‐specific competition patterns. 2. The diving ability and activity of larvae of the main African malaria vectors, An. coluzzii and An. gambiae, at two different water depths (14 and 30 cm) were assessed. We further explored the biological relevance of diving for food harvesting by monitoring key life history traits in two species treatments (single or mixed species) and two food treatments (surface or bottom feeding). 3. Overall, An. coluzzii larvae showed more diving activity than An. gambiae. When feeding at the bottom both species, and especially An. gambiae, showed a delayed emergence and a reduced emergence rate. Moreover, An. gambiae also suffered a reduced wing length. 4. Mixed‐species rearing had a detrimental effect on the life history traits of An. gambiae but not on An. coluzzii, suggesting a competitive advantage for the latter in our experimental conditions. 5. The present results confirm that anopheline larvae are able to forage for food at the bottom of their breeding site and that An. coluzzii shows a superior diving activity than An. gambiae and this at a lower cost. These behavioural differences probably reflect specific adaptations to different aquatic habitats, and may be important in shaping species distributions and the population biology of these important vector mosquitoes.     

The influence of a parasitoid's response to temperature on the performance of a tri‐trophic food web

1. Food web interactions are complex and can respond to environmental changes in unpredictable ways that do not necessarily equate to the individual responses of each of the components of the food web. 2. Biomass can be used to evaluate the productivity of the three individual trophic levels, in the form of the Net Generational Productivity (NGP) and the performance of the entire food web with the newly developed tri‐trophic food web performance ratio (?_3t). 3. These parameters were used to evaluate the performance of nine plant‐based tri‐trophic food webs composed of: potato, Solanum tuberosum L. and two cultivars of bell pepper Capsicum annuum L; three biotypes of the aphid Macrosiphum euphorbiae Thomas (Hemiptera: Aphididae) and the parasitoid wasp Aphidius ervi (Haliday) (Hymenoptera: Braconidae). 4. The NGP showed that the thermal window for biomass productivity for each trophic level is different and is reduced by approximately 4 °C with respect to the inferior level. Aphidius ervi had the smallest thermal window for biomass productivity and development. 5. The present results showed that the performance (?_3t) of the tested food webs is influenced in a top‐down fashion, where the intra‐specific variation of the food web, namely the host plant, played a major role in the productivity of each of the subsequent trophic levels. 6. The ?_3t suggested that exposure to high and low temperatures might severely affect the effectiveness of A. ervi as a biocontrol agent of the aphid M. euphorbiae in bell pepper and potato crops.     

Vertical transmission in feather mites: insights into its adaptive value

1. The consequences of symbiont transmission strategies are better understood than their adaptive causes. 2. Feather mites are permanent ectosymbionts of birds assumed to be transmitted mainly vertically from parents to offspring. The transmission of Proctophyllodes doleophyes Gaud (Astigmata, Proctophyllodidae) was studied in two European populations of pied flycatchers, Ficedula hypoleuca Pallas (Passeriformes, Muscicapidae). 3. The vertical transmission of this mite species is demonstrated here with an acaricide experiment. This study also compared (for two distant populations during 4 years) patterns in reductions in mite intensity in adult birds, from egg incubation to chick‐rearing periods, with the predictions of three hypotheses on how host survival prospects and mite intraspecific competition might drive feather mites' transmission strategy. 4. The results are in agreement with previous studies and show that feather mites transmit massively from parents to chicks. 5. The magnitude of the transmission was closer to that predicted by the hypothesis based on intraspecific competition, while a bet‐hedging strategy is also partially supported.