Reviewing the consequences of genetic purging on the success of rescue programs

Genetic rescue is increasingly considered a promising and underused conservation strategy to reduce inbreeding depression and restore genetic diversity in endangered populations, but the empirical evidence supporting its application is limited to a few generations. Here we discuss on the light of theory the role of inbreeding depression arising from partially recessive deleterious mutations and of genetic purging as main determinants of the medium to long-term success of rescue programs. This role depends on two main predictions: (1) The inbreeding load hidden in populations with a long stable demography increases with the effective population size; and (2) After a population shrinks, purging tends to remove its (partially) recessive deleterious alleles, a process that is slower but more efficient for large populations than for small ones. We also carry out computer simulations to investigate the impact of genetic purging on the medium to long term success of genetic rescue programs. For some scenarios, it is found that hybrid vigor followed by purging will lead to sustained successful rescue. However, there may be specific situations where the recipient population is so small that it cannot purge the inbreeding load introduced by migrants, which would lead to increased fitness inbreeding depression and extinction risk in the medium to long term. In such cases, the risk is expected to be higher if migrants came from a large non-purged population with high inbreeding load, particularly after the accumulation of the stochastic effects ascribed to repeated occasional migration events. Therefore, under the specific deleterious recessive mutation model considered, we conclude that additional caution should be taken in rescue programs. Unless the endangered population harbors some distinctive genetic singularity whose conservation is a main concern, restoration by continuous stable gene flow should be considered, whenever feasible, as it reduces the extinction risk compared to repeated occasional migration and can also allow recolonization events.

     

Comparing methods for estimating the abundance of Western Capercaillie Tetrao urogallus males in Pyrenean leks: singing counts versus genetic analysis of non-invasive samples

ABSTRACT

Population estimates of male Western Capercaillies Tetrao urogallus were carried out during the mating season using two methods: counts of singing males and non-invasive genetic analysis. Estimates of male numbers were 50% lower using the singing counts compared to the estimates obtained through genetic analysis, and underestimates were greatest when the number of Capercaillies was lowest.     

Pregnancy reduces critical thermal maximum,but not voluntary thermal maximum,in a viviparous skink

Journal of Comparative Physiology B - Upper thermal limits are commonly measured in ectotherms; however, the effects of life-history stages, and in particular pregnancy in viviparous species, are...     

Effects of ajugarins and related neoclerodane diterpenoids on feeding behaviour of Leptinotarsa decemlineata and Spodoptera exigua larvae

Three naturally occurring ajugarins and seven semisynthetic derivatives of them, possessing different functionalities in the decalin part, together with two natural furoneoclerodane diterpenes, have been assessed as feeding behavior modifying agents of larvae of the generalist Spodoptera exigua and a specialist like Leptinotarsa decemlineata. Ajugarin I and some of its derivatives exhibited a significant antifeedant activity against larvae of S. exigua in both choice and no-choice assays. Conversely, the furoneoclerodane diterpenes only presented antifeedant activity against larvae of L. decemlineata. These results indicate that the biological action of the tested substances is strongly modulated by minimal structural variations, which are also responsible for the specificity of action.     

Synthesis and inotropic activity of hydroindene derivatives

A synthetic approach to hydroindenic inotropic agents has been developed, starting from enantiopure Hajos-Parrish (1). Hajos-Wiechert (2), and related diketones. Their transformation into C-1 formyl derivatives and other subsequent synthetic targets is described. The results of the thermodynamic equilibration between both epimers of each formyl derivative are analysed. The inotropic activities of selected compounds on right and left atrial preparations are also evaluated and discussed.     

Selection of a nucleopolyhedrovirus for control of Spodoptera frugiperda (Lepidoptera: Noctuidae): structural, genetic, and biological comparison of four isolates from the Americas

Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) is the principal pest of maize in tropical and subtropical regions of the Americas. Larvae of this species are susceptible to a nucleopolyhedrovirus (NPV) which has attracted interest as a potential biocontrol agent. Four strains of NPV isolated from infected S. frugiperda larvae in the United States, Nicaragua, and Argentina were subjected to a structural, genetic, and biological comparison to select a candidate isolate for use in biocontrol experiments in Mexico and Honduras. All isolates had an occlusion body polyhedrin protein of 32 kDa, but the virions of each isolate differed subtly in the pattern and abundance of certain structural polypeptides revealed by SDS-PAGE analysis. Restriction endonuclease analysis of viral DNA confirmed that these isolates were strains of a single virus species but showed that they were not genetically homogeneous; each isolate could be differentiated from the others using common restriction enzymes. Droplet feeding bioassays indicated that an isolate from Nicaragua (Sf-NIC) and an isolate from the United States (Sf-US) had the highest infectivity when tested against 2nd instars originating from a Honduran S. frugiperda colony. No significant differences were detected in the speed of kill of Sf-NIC (102.7 h), Sf-US (102.3 h) and Sf-AR (103.4 h), whereas that of Sf-2 (97.3 h) was significantly shorter. Additional bioassays of the Sf-NIC isolate against 2nd to 6th instars demonstrated that LC50 values increased with larval stage from 2.03 x 10(5) OBs/ml for 2nd instars to 1.84 x 10(8) OBs/ml for 5th instars. The concentration required to elicit a lethal infection of 6th instars was so high that a reliable estimate of LC50 could not be obtained. The mean time to death for each stage challenged with the Sf-NIC isolate increased with instar from an average of 102.7 h in 2nd instars to 136.9 h in 5th instars.     

Development of a SNP genotyping panel for genetic monitoring of the laboratory mouse

We have developed a genotyping system for detecting genetic contamination in the laboratory mouse based on assaying single-nucleotide polymorphism (SNP) markers positioned on all autosomes and the X chromosome. This system provides a fast, reliable, and cost-effective way for genetic monitoring, while maintaining a very high degree of confidence. We describe the allelic distribution of 235 SNPs in 48 mouse strains, thereby creating a database of polymorphisms useful for genotyping purposes. The SNP markers used in this study were chosen from publicly available SNP databases. Four genotyping methods were evaluated, and dynamic two-tube allele-specific PCR assays were developed for each marker and tested on a set of 48 inbred mouse strains. The minimal number of assays sufficient to distinguish groups consisting of different numbers of mouse strains was estimated, and a panel of 28 SNPs sufficient to distinguish virtually all of the inbred strains tested was selected. Amplifluor SNP detection assays were developed for these markers and tested on an extended list of 96 strains. This panel was used as a genetic quality control approach to monitor the genotypes of nearly 300 inbred, wild-derived, congenic, consomic, and recombinant inbred strains maintained at The Jackson Laboratory. We have concluded that this marker panel is sufficient for genetic contamination monitoring in colonies containing a large number of genetically diverse mouse strains and that reduced versions of the panel could be implemented in facilities housing a lower number of strains.     

Cell mediated immune response elicited in mice after immunization with the P64k meningococcal protein: epitope mapping

The P64k protein of Neisseria meningitidis has been reported as an immunological carrier for weak immunogens. This investigation was aimed at characterizing the T-cell response produced in primed mice and at identifying T helper cell epitopes within this molecule. BALB/c mice subcutaneously immunized with the recombinant antigen provided inguinal lymph node cells (LNC) that proliferated in the presence of P64k in a dose-dependent manner. Proliferating cells secreted IL-4 while the concentration of IL-12 remained unaltered in the culture supernatant. By testing a panel of 59 overlapping synthetic peptides spanning the entire sequence of the antigen a T-cell determinant was localized. Prime-boost and lymphoproliferation experiments, conducted with highly purified synthetic peptides, confirmed that the segment including amino acids 470-485 comprises a T-cell epitope within the P64k molecule.     

Survival and growth of goat primordial follicles after in vitro culture of ovarian cortical slices in media containing coconut water

The development of culture systems to support the initiation of growth of primordial follicles is important to the study of the factors that control the earliest stages of folliculogenesis. We investigated the effectiveness of five culture media, two supplements and three culture periods on the survival and growth of goat primordial follicles after culturing ovarian cortex. The media were based on minimal essential minimum (MEM) and coconut water solution (CWS) added in the proportion of 0, 25, 50, 75 or 100%. The two supplements were none versus supplemented with insulin-transferrin-selenium, pyruvate, glutamine, hypoxanthine, and BSA. Pieces of goat ovarian cortex were cultured in the media for 1, 3 or 5 days and representative samples were evaluated at day 0 as non-cultured controls. The replicates were the two ovaries of five mixed breed goats. The number of primordial, intermediate, primary and secondary follicles at each period of culture and the number of degenerated follicles were evaluated. Mitotic activity of granulosa cells was studied by immunolocalization of proliferating cell nuclear antigen (PCNA). The number of follicles in each stage and degenerated follicles were statistically analyzed by ANOVA using a factorial design and the significance of differences assessed using Tukey test. Chi-square test was used to compare the percentage of follicles with PCNA positive granulosa cells. As the culture period progressed, the number of primordial follicles fell and there was a significant increase in the number of primary follicles. The fall in the number of primordial follicles was particularly marked after 1 day culture. No effect of media on the number of primordial and primary follicles was observed after culture, but MEM as well as supplements increased the number of intermediate follicles. Follicular degeneration was kept at the same level after culture in the media tested, except for pure CWS that increased the number of degenerated follicles. In contrast, addition of supplements to culture media reduced follicular degeneration. In non-cultured tissue, PCNA was expressed in granulosa cells of 31.6% of the growing follicles. This percentage had not significantly changed after 5 days culture in the various media, indicating the maintenance of proliferation activity of granulosa cells during culture. In conclusion, it is shown that goat primordial follicles may be successfully activated after in vitro culture in all media tested. However, when pure CWS is used the follicular degeneration is enhanced, but the addition of supplements to culture media decrease follicular degeneration.