On the use of large marker panels to estimate inbreeding and relatedness: empirical and simulation studies of a pedigreed zebra finch population typed at 771 SNPs

In recent years there has been a dramatic increase in the availability of high density genetic marker data for both model and non‐model organisms. A potential application of these data is to infer relatedness in the absence of a complete pedigree. Using a marker panel of 771 SNPs genotyped in three generations of an extensive zebra finch pedigree, correlations between pedigree relatedness and seven marker‐based estimates of relatedness were examined, as was the relationship between heterozygosity and inbreeding. Although marker‐based and pedigree relatedness were highly correlated, the variance in estimated relatedness was high. Further, the correlation between heterozygosity and inbreeding was weak, even though mean inbreeding coefficient is typical of that seen in wild vertebrate pedigrees; the weak relationship was in part due to the small variance in inbreeding in the pedigree. Our data suggest that using marker information to reconstruct the pedigree, and then calculating relatedness from the pedigree, is likely to give more accurate relatedness estimates than using marker‐based estimators directly.     

Dieback and mortality of South African fynbos shrubs is likely driven by a novel pathogen and pathogen‐induced hydraulic failure

We examined whether extensive dry season dieback and mortality in a South African fynbos community were due to drought or pathogen attack. Plant dieback and mortality have been reported elsewhere in similar plant communities suggesting potential for a widespread climatic or biotic threat to this community. We collected tissue samples from Brunia noduliflora, the dominant plant in the community, and cultured them for potential plant pathogens. We also measured dry season predawn and midday water potentials of healthy and stressed plants and constructed pressure‐volume curves to assess turgor loss point. Plant stress and mortality were monitored over a 2‐year study period. Both healthy plants and plants that displayed moderate signs of stress had dry season predawn water potentials well above their turgor loss point suggesting plants were not water stressed. However, plants displaying >60% crown dieback had much lower water potentials (as low as ?12 MPa). A previously undescribed fungus (Pythium sp.) was isolated from the root vascular tissue of all stressed plants and was not present in healthy plants. The proximate cause of plant stress was likely pathogen‐induced, while the ultimate cause of plant death appears to be extreme water stress. The present study suggests that Brunia (Bruniceae), Leucadendron (Proteaceae) and Erica (Ericaceae), all emblematic and dominant genera within the diverse fynbos community, may be susceptible to Pythium infection. This may pose a serious threat to communities already threatened by climate change.     

The value of georeferenced collection records for predicting patterns of mosquito species richness and endemism in the Neotropics

Abstract.  1. Determining large-scale distribution patterns for mosquitoes could advance knowledge of global mosquito biogeography and inform decisions about where mosquito inventory needs are greatest.
2. Over 43 000 georeferenced records are presented of identified and vouchered mosquitoes from collections undertaken between 1899 and 1982, from 1853 locations in 42 countries throughout the Neotropics. Of 492 species in the data set, 23% were only recorded from one location, and Anopheles albimanus Wiedemann is the most common species.
3. A linear log–log species–area relationship was found for mosquito species number and country area. Chile had the lowest relative density of species and Trinidad-Tobago the highest, followed by Panama and French Guiana.
4. The potential distribution of species was predicted using an Ecological Niche Modelling (ENM) approach. Anopheles species had the largest predicted species ranges, whereas species of Deinocerites and Wyeomyia had the smallest.
5. Species richness was estimated for 1° grids and by summing predicted presence of species from ENM. These methods both showed areas of high species richness in French Guiana, Panama, Trinidad-Tobago, and Colombia. Potential hotspots in endemicity included unsampled areas in Panama, French Guiana, Colombia, Belize, Venezuela, and Brazil.
6. Argentina, The Bahamas, Bermuda, Bolivia, Cuba, and Peru were the most under-represented countries in the database compared with known country species occurrence data. Analysis of species accumulation curves suggested patchiness in the distribution of data points, which may affect estimates of species richness.
7. The data set is a first step towards the development of a global-scale repository of georeferenced mosquito collection records.     

Rapid In Vitro Prescreen for Chelators as Potential Trypanocides Based on Growth of Crithidia fasciculata1

A rapid in vitro prescreen for Fe-binding chelators has been developed with growth of Crithidia fasciculata and the sparing of its heme requirement in a defined medium as a test system. The prescreen functions as an index of chelator-mediated Fe transport and as an index of growth inhibition, presumably by the interference with Fe and/or heme metabolism at intracellular chelatable sites. Of 161 chelators examined, 84 were active heme-sparers; 32 of these inhibited growth at low chelator concentrations. Twenty-eight other chelators inhibited growth and another 49 were inactive. Such chelating activity directed at Fe and heme targets in hemoflagellates may provide leads for chemotherapy.     

Piecing together an integrative taxonomic puzzle: microsatellite,wing shape and aedeagus length analyses of Bactrocera dorsalis s.l. (Diptera: Tephritidae) find no evidence of multiple lineages in a proposed contact zone along the Thai/Malay Peninsula

Bactrocera dorsalis (Hendel) and B. papayae Drew & Hancock represent a closely related sibling species pair for which the biological species limits are unclear; i.e. it is uncertain if they are truely two biological species, or one biological species which has been incorrectly split taxonomically. The geographical ranges of the two taxa are thought to abut or overlap on or around the Isthmus of Kra, a recognised biogeographic barrier located on the narrowest portion of the Thai Peninsula. We collected fresh material of B. dorsalis s.l. (i.e. B. dorsalis s.s.+ B. papayae) in a north–south transect down the Thai Peninsula, from areas regarded as being exclusively B. dorsalis s.s., across the Kra Isthmus, and into regions regarded as exclusively B. papayae. We carried out microsatellite analyses and took measurements of male genitalia and wing shape, both used previously to separate the taxa. No significant population structuring was found in the microsatellite analysis, consistent with one, predominantly panmictic population. Both morphological datasets showed consistent, clinal variation along the transect, without disjunction. No evidence supported historical vicariance driven by the Isthmus of Kra, and no dataset supported the current taxonomy of two species. Rather, within and across the area of range overlap or abutment between the two species, only continuous morphological and genetic variation was recorded. Recognition that morphological traits previously used to separate these taxa are continuous, and that there is no genetic evidence for population segregation in the region of suspected species overlap, is consistent with a growing body of literature that reports no evidence of biological differentiation between these taxa.     

Genetic diversity of Philaenus spumarius and P. tesselatus (Hemiptera,Aphrophoridae): implications for evolution and taxonomy

The meadow spittlebugs Philaenus spumarius and P. tesselatus are closely related taxa with uncertain taxonomic position in the light of previous morphological, ecological, cytological and molecular research. Despite morphological homogeneity of P. spumarius (with the exception of high colour and pattern polymorphism) across its wide Holarctic range, it is possible that additional taxa (species or subspecies) exist. Philaenus spumarius is a potentially important pest in parts of its range where it was introduced. We used DNA markers to describe the genetic diversity of P. spumarius and P. tesselatus and to verify the taxonomic status of P. tesselatus and remote populations of the former species. The mitochondrial (cytochrome B) data showed that there are two main groups encompassing a northeastern (Asia and north‐central Europe) and a southwestern (Mediterranean area and western Europe, including North American specimens) clade. According to the elongation factor‐1α gene, there are three main clades: northeastern (Eurasiatic clade, E1), southeastern (east Mediterranean – Caucasus clade, E2) and southwestern (Iberian clade, E3). These two or three mitochondrial and nuclear clades could be considered as separate taxonomic units. On the other hand, all studied individuals of both species possessed the same internal transcribed spacer 2 haplotype. American specimens most probably originated from some western European populations. All studied specimens of P. tesselatus belong to the southwestern clade and western Mediterranean cluster. Therefore, together with cytological data, its species status is doubtful. To definitively solve the taxonomic status of P. tesselatus and populations of P. spumarius, further research using more samples and more genetic markers are needed.