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Sex-biased inbreeding effects on reproductive success and home range size of the critically endangered black rhinoceros
Cain, W.S. ; Wandera, A.B. ; Shawcross, S.G. ; Ouma, B.O. ; Watts, P.C. - \ 2014
Conservation Biology 28 (2014)2. - ISSN 0888-8892 - p. 594 - 603.
heterozygosity-fitness correlations - wide genetic diversity - natural-populations - diceros-bicornis - multilocus heterozygosity - microsatellite markers - wild populations - south-africa - depression - reserve
A central premise of conservation biology is that small populations suffer reduced viability through loss of genetic diversity and inbreeding. However, there is little evidence that variation in inbreeding impacts individual reproductive success within remnant populations of threatened taxa, largely due to problems associated with obtaining comprehensive pedigree information to estimate inbreeding. In the critically endangered black rhinoceros, a species that experienced severe demographic reductions, we used model selection to identify factors associated with variation in reproductive success (number of offspring). Factors examined as predictors of reproductive success were age, home range size, number of nearby mates, reserve location, and multilocus heterozygosity (a proxy for inbreeding). Multilocus heterozygosity predicted male reproductive success (p<0.001, explained deviance >58%) and correlated with male home range size (p <0.01, r2 > 44%). Such effects were not apparent in females, where reproductive success was determined by age (p <0.01, explained deviance 34%) as females raise calves alone and choose between, rather than compete for, mates. This first report of a 3-way association between an individual male's heterozygosity, reproductive output, and territory size in a large vertebrate is consistent with an asymmetry in the level of intrasexual competition and highlights the relevance of sex-biased inbreeding for the management of many conservation-priority species. Our results contrast with the idea that wild populations of threatened taxa may possess some inherent difference from most nonthreatened populations that necessitates the use of detailed pedigrees to study inbreeding effects. Despite substantial variance in male reproductive success, the increased fitness of more heterozygous males limits the loss of heterozygosity. Understanding how individual differences in genetic diversity mediate the outcome of intrasexual competition will be essential for effective management, particularly in enclosed populations, where individuals have restricted choice about home range location and where the reproductive impact of translocated animals will depend upon the background distribution in individual heterozygosity. © 2013 Society for Conservation Biology.
Deciphering microbial landscapes of fish eggs to mitigate emerging diseases
Liu, Y. ; Bruijn, I. de; Jack, A.L.H. ; Drynan, K. ; Berg, A.H. van den; Thoen, E. ; Sandoval-Sierra, V. ; Skaar, I. ; West, P. van; Diéguez-Uribeondo, J. ; Voort, M. van der; Mendez, R. ; Mazzola, M. ; Raaijmakers, J.M. - \ 2014
ISME Journal 8 (2014). - ISSN 1751-7362 - p. 2002 - 2014.
saprolegnia-parasitica - rhizosphere microbiome - aphanomyces-invadans - virulence factors - maternal transfer - wild populations - sp nov. - fungi - bacteria - molds
Animals and plants are increasingly suffering from diseases caused by fungi and oomycetes. These emerging pathogens are now recognized as a global threat to biodiversity and food security. Among oomycetes, Saprolegnia species cause significant declines in fish and amphibian populations. Fish eggs have an immature adaptive immune system and depend on nonspecific innate defences to ward off pathogens. Here, meta-taxonomic analyses revealed that Atlantic salmon eggs are home to diverse fungal, oomycete and bacterial communities. Although virulent Saprolegnia isolates were found in all salmon egg samples, a low incidence of Saprolegniosis was strongly correlated with a high richness and abundance of specific commensal Actinobacteria, with the genus Frondihabitans (Microbacteriaceae) effectively inhibiting attachment of Saprolegniato salmon eggs. These results highlight that fundamental insights into microbial landscapes of fish eggs may provide new sustainable means to mitigate emerging diseases.
Varying disease-mediated selection at different life-history stages of Atlantic salmon in fresh water
Eyto, E. de; McGinnity, P. ; Huisman, J. ; Coughlan, J. ; Consuegra, S. ; Megens, H.J.W.C. - \ 2011
Evolutionary Applications 4 (2011)6. - ISSN 1752-4563 - p. 749 - 762.
major histocompatibility complex - class-i locus - salar l. - genetic-variation - pathogen resistance - balancing selection - natural-selection - wild populations - local adaptation - climate-change
Laboratory studies on associations between disease resistance and susceptibility and major histocompatibility (MH) genes in Atlantic salmon Salmo salar have shown the importance of immunogenetics in understanding the capacity of populations to fight specific diseases. However, the occurrence and virulence of pathogens may vary spatially and temporally in the wild, making it more complicated to predict the overall effect that MH genes exert on fitness of natural populations and over several life-history stages. Here we show that MH variability is a significant determinant of salmon survival in fresh water, by comparing observed and expected genotype frequencies at MH and control microsatellite loci at parr and migrant stages in the wild. We found that additive allelic effects at immunogenetic loci were more likely to determine survival than dominance deviation, and that selection on certain MH alleles varied with life stage, possibly owing to varying pathogen prevalence and/or virulence over time. Our results highlight the importance of preserving genetic diversity (particularly at MH loci) in wild populations, so that they have the best chance of adapting to new and increased disease challenges as a result of projected climate warming and increasing aquaculture
Chemical diversity in Brassica oleracea affects biodiversity of insect herbivores
Poelman, E.H. ; Dam, N.M. van; Loon, J.J.A. van; Vet, L.E.M. ; Dicke, M. - \ 2009
Ecology 90 (2009)7. - ISSN 0012-9658 - p. 1863 - 1877.
arthropod community structure - primrose oenothera-biennis - plant defense - genetic-variation - generalist herbivores - genotypic variation - feeding stimulants - barbarea-vulgaris - wild populations - pieris-rapae
Intraspecific variation in plants plays a major role in the composition and diversity of the associated insect community. Resistance traits of plants are likely candidates mediating community composition. However, it is debated whether total concentrations of chemical compounds or specific compounds determine herbivore resistance, and how chemical diversity among plant genotypes in turn affects the composition of the associated herbivore community. To study the role of specific chemical compounds in affecting the herbivore community, we used cultivated Brassica oleracea. The cultivars differ qualitatively in glucosinolate profile, i.e., foliar composition of different glucosinolate compounds, and only a little in total concentration of glucosinolates, the secondary metabolites specific for the Brassicaceae family. In field and laboratory experiments, we tested whether individual compounds explained differences in herbivore community composition, and whether herbivores with a similar degree of host plant specialization responded in a similar way to variation in glucosinolate profiles. In the field B. oleracea cultivars differed widely in species richness and composition of the herbivore community, as well as in the density of insects they harbored. Plants with high concentrations of the short side chain alkenyl glucosinolate, glucoiberin, harbored low herbivore diversity. Higher biodiversity was found when plants had glucosinolate profiles containing high concentrations of glucosinolates with elongated side chains, which are biosynthetically linked to glucoiberin. Although glucosinolates are known to have differential effects on generalist and specialist herbivores, all herbivore species exhibited similar responses to the intraspecific variation in foliar glucosinolate profiles of the B. oleracea cultivars. This observation is supported by the correspondence between oviposition preferences of the specialist herbivore Pieris rapae and the generalist Mamestra brassicae in the field and the laboratory, using the same cultivars, and may be due to the relatively low concentrations of glucosinolates in cultivars. Our results show that variation in the concentration of short side-chain glucosinolates affects the composition of the herbivore community associated with brassicaceous plants
Performance of specialist and generalist herbivores feeding on cabbage cultivars is not explained by glucosinolate profiles
Poelman, E.H. ; Galiart, R.J.F.H. ; Raaijmakers, C.E. ; Loon, J.J.A. van; Dam, N.M. van - \ 2008
Entomologia Experimentalis et Applicata 127 (2008)3. - ISSN 0013-8703 - p. 218 - 228.
rape brassica-napus - oilseed rape - phytophagous insects - plutella-xylostella - wild populations - diamondback moth - pieris-rapae - resistance - mustard - responses
Plants display a wide range of chemical defences that may differ in effectiveness against generalist and specialist insect herbivores. Host plant-specific secondary chemicals such as glucosinolates (GS) in Brassicaceae typically reduce the performance of generalist herbivores, whereas specialists have adaptations to detoxify these compounds. The concentration of glucosinolates may also alter upon herbivory, allowing the plant to tailor its response to specifically affect the performance of the attacking herbivore. We studied the performance of three Lepidoptera species, two specialists [Pieris rapae L. (Pieridae), Plutella xylostella L. (Yponomeutidae)] and one generalist [Mamestra brassicae L. (Noctuidae)], when feeding on eight cultivars of Brassica oleracea L. and a native congener (Brassica nigra L.) and related this to the GS content. We tested the hypotheses (i) that a generalist herbivore is more affected by high GS concentrations, and (ii) that generalist feeding has a stronger effect on GS levels. Although performance of the three herbivores was different on the B. oleracea cultivars, M. brassicae and P. xylostella had a similar ranking order of performance on the eight cultivars. In most of the cultivars, the concentration of indole GS was significantly higher after feeding by P. rapae or M. brassicae than after P. xylostella feeding. As a consequence, the total concentration of GS in the cultivars showed a different ranking order for each herbivore species. The generalist M. brassicae performed equally well as the specialist P. xylostella on cultivars with high concentrations of GS. Our findings suggest that secondary metabolites other than GSs or differences in nutrient levels affect performance of the species studied.
Beyond induced mutants: using worms to study natural variation in genetic pathways
Kammenga, J.E. ; Philips, P.C. ; Bono, M. de; Doroszuk, A. - \ 2008
Trends in Genetics 24 (2008)4. - ISSN 0168-9525 - p. 178 - 185.
quantitative trait loci - life-history traits - genotype-environment interactions - single-nucleotide polymorphisms - nematode caenorhabditis-elegans - c-elegans - linkage disequilibrium - genus caenorhabditis - wild populations - expression
Induced mutants in the nematode Caenorhabditis elegans are used to study genetic pathways of processes ranging from aging to behavior. The effects of such mutations are usually analyzed in a single wildtype background: N2. However, studies in other species demonstrate that the phenotype(s) of induced mutations can vary widely depending on the genetic background. Moreover, induced mutations in one genetic background do not reveal the allelic effects that segregate in natural populations and contribute to phenotypic variation. Because other wildtype Caenorhabditis spp., including C. elegans, are now available, we review how current mapping resources and methodologies within and between species support the use of Caenorhabditis spp. for studying genetic variation, with a focus on pathways associated with human disease.
Development of an insect herbivore and its pupal parasitoid reflect differences in direct plant defense
Harvey, J.A. ; Gols, R. ; Wagenaar, R. ; Bezemer, T.M. - \ 2007
Journal of Chemical Ecology 33 (2007)8. - ISSN 0098-0331 - p. 1556 - 1569.
4 trophic levels - host-plant - specialist herbivore - phytophagous insects - plutella-xylostella - brassica-oleracea - wild populations - trichoplusia-ni - manduca-sexta - pieris-rapae
In nature, plants defend themselves by production of allelochemicals that are toxic to herbivores. There may be considerable genetic variation in the expression of chemical defenses because of various selection pressures. In this study, we examined the development of the small cabbage butterfly, Pieris rapae, and its gregarious pupal ectoparasitoid, Pteromalus puparum, when reared on three wild populations (Kimmeridge, Old Harry, Winspit) of cabbage, Brassica oleracea, and a Brussels sprout cultivar. Wild plant populations were obtained from seeds of plants that grow naturally along the south coast of Dorset, England. Significant differences in concentrations of allelochemicals (glucosinolates) were found in leaves of plants damaged by P. rapae. Total glucosinolate concentrations in Winspit plants, the population with the highest total glucosinolate concentration, were approximately four times higher than in the cultivar, the strain with the lowest total glucosinolate concentration. Pupal mass of P. rapae and adult body mass of Pt. puparum were highest when reared on the cultivar and lowest when developing on Kimmeridge plants, the wild strain with the lowest total glucosinolate concentration. Development of male parasitoids was also more negatively affected than female parasitoids. Our results reveal that plant quality, at least for the development of 'adapted' oligophagous herbivores, such as P. rapae, is not based on total glucosinolate content. The only glucosinolate compound that corresponded with the performance of P. rapae was the indole glucosinolate, neoglucobrassicin. Our results show that performance of ectoparasitoids may closely reflect constraints on the development of the host.