Brian Keane

When Should Animals Tolerate Inbreeding

We compare, in an initially outbred population, the number of offspring equivalents expected by an individual that avoids all inbreeding with that expected by an individual that tolerates one inbred mating. The model suggests that for most mating systems, the sole factor determining whether inbreeding tolerance spreads is the cost of inbreeding avoidance. Specifically, most forms of polygyny do not increase the payoff to inbreeding; the critical parameter is not the number of matings an individual engages in but rather how many outbred matings are forfeited when an individual chooses to mate with a relative. The model also suggests that dispersal is unlikely to have arisen primarily as a mechanism to avoid inbreeding, and that father-daughter inbreeding should be more common than mother-son inbreeding.

The effect of relatedness on reproductive success and mate choice in the white-footed mouse, Peromyscus leucopus

A unique means for automatic closed-loop speed and power factor regulation, both below and above synchronous speed, using electronically derived, rotor injected EMFs for rotating electrical machinery, with no power pulsations, and smooth continuous control is described. EMFs of the correct frequency are electronically derived and modulated to the appropriate amplitude, without the use of a current transformer and its associated saturation problems, using feedback signals from a speed transducer for comparison with a reference signal for master control. This arrangement allows independent setting of the speed and rotor power factor angle. Speed regulation at the desired setting is maintained through feedback controls. Unlike previous art this technique allows speed control beyond synchronous speed, with no torque pulsations, minimum rotor power loss and also allows elimination of slip rings.

Dispersal and inbreeding avoidance in the white-footed mouse, Peromyscus leucopus

Abstract The effects of inbreeding depression on dispersal tendencies in white-footed mice were investigated by experimentally measuring the reproductive success of females that artificially ‘dispersed’ various distances. Observed natal dispersal distances were also compared against those predicted by a model in which competition for home range sites is the sole factor determining dispersal distance. In the population studied, the majority of juveniles of both sexes remained as adults on or adjacent to their natal home range. In artificial dispersal experiments, all measures of reproductive success for females mated with males that occupied home ranges located 1 inter-activity-centre distance away from their natal centre of activity were similar or superior to that of females mated to males from 2 to 3 or 10 inter-activity-centre distances away. Though a significant inbreeding depression has been demonstrated in this population for full-sibling and half-sibling matings, high juvenile and adult mortality makes it probable that individuals dispersing even to an adjacent home range will rarely risk close inbreeding. Comparison of the probabilities of philopatry with a null model suggests that females are moving only as far as forced to by competition to find a vacant home range. Males seem to avoid settling in their natal home range, even if the resident adult male has disappeared. Males may be dispersing to avoid inbreeding, but other evidence suggests that females avoid mating with close kin and male dispersal is a consequence, not a cause of inbreeding avoidance.

Polymorphism at the avpr1a locus in male prairie voles correlated with genetic but not social monogamy in field populations

Integrative studies of genetics, neurobiology and behaviour indicate that polymorphism in specific genes contributes to variation observed in some complex social behaviours. The neuropeptide arginine vasopressin plays an important role in the regulation of a variety of social behaviours, including social attachment of males to females, through its action on the vasopressin 1a receptor (V1aR). In socially monogamous prairie voles (Microtus ochrogaster), polymorphism in the length of microsatellite DNA within the regulatory region of the gene (avpr1a) encoding the V1aR predicts differences among males in neural expression of V1aRs and partner preference under laboratory conditions. However, understanding the extent to which V1aR mediates variation in prairie vole social and reproductive behaviour observed in nature requires investigating the consequences of avpr1a polymorphism and environmental influences under ecologically relevant conditions. We examined the relationship between avpr1a length polymorphism and monogamy among male prairie voles living in 0.1 ha enclosures during a time similar to their natural lifespan. We found no evidence that avpr1a genotype of males predicts variation in social monogamy measured in the field but some indices of social monogamy were affected by population density. Parentage data indicated that a male’s avpr1a genotype significantly influenced the number of females with which he sired offspring and the total number of offspring sired. Total brain concentrations of V1aR mRNA were not associated with either male behaviour or avpr1a genotype. These data show that melding ecological field studies with neurogenetics can substantially augment our understanding of the effects of genes and environment on social behaviours.

avpr1a length polymorphism is not associated with either social or genetic monogamy in free-living prairie voles

Recent discoveries of single-gene influences on social behaviour have generated a great deal of interest in the proximate mechanisms underlying the expression of complex behaviours. Length polymorphism in a microsatellite in the regulatory region of the gene encoding the vasopressin 1a receptor (avpr1a) has been associated with both inter- and intra-specific variation in socially monogamous behaviour in voles (genus Microtus) under laboratory conditions. Here, we evaluate the relationship between avpr1a length polymorphism and social associations, genetic monogamy, and reproductive success in free-living prairie vole (M. ochrogaster) populations. We found no evidence of a relationship between avpr1a microsatellite length and any of our correlates of either social or genetic monogamy in the field. Our results, especially when taken in conjunction with those of recent experimental studies in semi-natural enclosures, suggest that avpr1a polymorphism is unlikely to have been a major influence in the evolution or maintenance of social monogamy in prairie voles under natural conditions.

Intraspecific variability in the social and genetic mating systems of prairie voles, Microtus ochrogaster

Intraspecific variability in mating systems has been documented previously, but there are few studies where investigators have used intraspecific comparisons to investigate the influence of ecological or demographic factors on social and genetic mating systems. We studied two populations of prairie voles, Microtus ochrogaster, one near Lawrence, Kansas, U.S.A., and the other in Bloomington, Indiana, U.S.A. We examined differences in spatial structuring of vegetation between sites, which might contribute to intraspecific variation in social and genetic mating patterns. Since space use is often related to the mating system, we calculated home range size of a subset of adult males and females in both populations and used live trapping to examine the number of same- or opposite-sex conspecifics sharing capture locations. We applied social network analysis to live-trapping data to quantify the number and strength of social ties with opposite-sex conspecifics. Genetic parentage analysis provided an estimate of the number of mates per individual. We found that space use and overlap with members of the same and opposite sex were best explained by effects of site and sex. The relative strength of social associations with opposite-sex conspecifics was best predicted by site, density and sex. The genetic mating system was best explained by population density. Although we cannot disentangle population density from ecological variables related to site (e.g. distribution of vegetation) that may have affected social monogamy in our study populations, our study shows that extrinsic variables do affect differences in social and genetic mating systems between populations.

Genetic variation across VNTR loci in central North American Taraxacum surveyed at different spatial scales

Dandelions (Taraxacum officinale Weber(sensu lato); Asteraceae) have been introduced to NorthandSouth America with human migration from Europe. While potential sourcepopulations have both sexually and obligate asexually (agamospermous)reproducing lineages, apparently only the latter have successfully colonizedtheAmericas. The consequences of obligate agamospermy on dandelion populationgenetic diversity in North America remain little explored. Here we use fourdifferent synthetic DNA probes that reveal genetic markers at multiplevariable-number-tandem-repeat (VNTR) loci to examine patterns of geneticvariation among plants collected along three different central North Americantransects with plants (21 to 22 individuals per transect) separated by: 1) >2 m and < 60 m (short transect); 2) > 5km and < 30 km (medium transect); and 3) > 30km and < 340 km (long transect). The mean numberofVNTR markers revealed per plant was 59.3. Co-clonal individuals (proportion ofbands shared exceeding 90%) were found in each transect, with the indexof clonality (the percent of co-clonal individuals detected in a transect)ranging from 34.12% for the short transect to 18.65% for the longtransect. Co-clonal individuals were separated by up to 200 km.With redundant examples of co-clonal individuals removed, mean similarity(proportion of band sharing) of distinct genotypes within transects was 0.426,and no statistical differences in level of similarity between transects, norindication of genetic differentiation between transects, was detected (meanFst between transect levels with all individuals included =0.05). These results indicate: 1) that dandelion genetic diversity ofcolonizinglineages in central North America is moderately high and does not reflectextreme bottleneck effects shown by some colonizing species; and 2) thatdandelion seed dispersal can be very effective in maintaining similar levels ofgenetic diversity at the different scales of sampling in this study, withcertain clones maintaining numerous, widespread individuals. Evidence that VNTRmutation is detectable within dandelion clonal lineages is presented,demonstrating that “clonal families” with lines increasinglydifferentiated from one another will continually evolve, and that Mullersrachet is, in all likelihood, turning for asexual lines.

DNA extraction from plants: The use of pectinase

Several earlier protocols for extracting plant DNA or RNA do not work well for a variety of plants because contaminating substances coprecipitate with the nucleic acids and, thus, are present even at the last DNA-hydration step. While DNA extraction protocols have been published in which pectinase is employed to break down these contaminating substances, here we present an alternative modified pectinase protocol that potentially uses fewer steps and avoids the use of ethylene glycol monoethyl ether and phenol. DNA analyses results are described for 6 plant species demonstrating that the method works across distantly related plant taxa.

Female prairie voles show social and sexual preferences for males with longer avpr1a microsatellite alleles

In socially monogamous mammals, male behaviour can have important consequences on production and survival of offspring. Therefore, females in these species could enhance their reproductive success by discriminating among potential male social partners and mates on the basis of phenotypic cues correlated with male fidelity and paternal behaviour. Prairie voles, Microtus ochrogaster, are socially monogamous rodents that typically form pair bonds and show extensive biparental care. In male prairie voles, variation in the length of microsatellite DNA in the regulatory region of the avpr1a gene encoding the vasopressin 1a receptor (V1aR) underlies differences in V1aR neural expression and is correlated with significant differences in partner preference and paternal behaviour. Previous laboratory studies demonstrated that males possessing longer avpr1a microsatellite alleles spend more time with their female social partner, sire offspring with fewer females and provide more paternal care relative to males with shorter avpr1a microsatellite alleles. Our results from laboratory preference trials showed that female voles from populations in Illinois and Kansas displayed significant social and sexual preferences for males that possessed longer avpr1a microsatellite alleles. These findings are consistent with the hypothesis that females are using phenotypic cues whose expression is correlated with a male’s avpr1a microsatellite genotype to discriminate among potential mates. These social and sexual preferences for males with longer avpr1a microsatellite alleles may result in increased female reproductive success.

Productivity differences between dandelion ( Taraxacum officinale ; Asteraceae) clones from pollution impacted versus non-impacted soils

Common dandelions (Taraxacum officinale Weber, sensu lato; Asteraceae) introduced to North America form an assemblage of asexual (agamospermous), clonal lineages derived from Eurasian mixed sexual and asexual populations. We investigated whether selection for more pollution tolerant clonal lineages occurs at polluted sites and selection for more pollution intolerant lineages occurs at unpolluted sites. We tested the above hypothesis by performing reciprocal greenhouse productivity experiments in which unique dandelion clones (12 clones, identified by DNA fingerprinting, from each site type) sampled from two unpolluted and two polluted (moderately enhanced Cu, Pb and Zn soil concentrations) sites were grown pairwise in both unpolluted (nutrient solution only) and polluted (nutrient solution + Cu, Pb and Zn) media (n = 48 paired tests for each media type). Dandelion clones from polluted sites produced fewer and smaller leaves, shorter roots and smaller root diameters, reduced shoot and root dry weights, and reduced total biomass compared to clones from unpolluted sites when clones were grown in unpolluted-media (P ≤ 0.05). In contrast, clones taken from unpolluted sites were shown to produce significantly fewer and shorter leaves, shorter roots and smaller root diameters, reduced shoot and root dry weights, reduced total biomass, a reduced shoot : root biomass ratio, and have much lower survival compared to clones from polluted sites when both were grown in polluted-media (P ≤ 0.05). These results reveal that there was increased selection against unpolluted-site clonal lineages in polluted-media and against polluted-site clonal lineages in unpolluted-media. Across all treatments, clones from unpolluted sites growing in unpolluted-media had the highest proximate measures of fitness. Overall, these findings provide insight into the relationships among anthropogenic environmental contamination and the consequent effects of selective forces acting on dandelion clones and their population genetic architecture.