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PubMed1991

Genetic effects for reproductive traits in beef cattle and predicted performance.

Reproductive data were collected on 4,595 cow exposures and subsequent calvings over four generations in a rotational crossbreeding study involving Angus, Brahman, Charolais and Hereford breeds. Direct and maternal additive (Ig and Mg) and nonadditive (Ih and Mh) genetic effects were estimated for calving rate, calf survival, weaning rate, calving assistance and calf birth date. Genetic effects were estimated by regressing individual animal response on the proportion of genes from breed of origin and gene combinations expected for the four breeds in offspring and in dams. Breed direct and maternal additive and nonadditive genetic effects were expressed as a deviation from the least squares mean. Brahman Ig effects decreased calving and weaning rate (-9.5 +/- 4.0 and -11.8 +/- 4.4%) but Mh effects for weaning rate that included Brahman were positive, ranging from 16.5 +/- 6.7% for Angus-Brahman to 27.8 +/- 6.9% for Brahman-Hereford. The Brahman Ig effect delayed calf birth date (9.8 +/- 2.1 d; P less than .01), whereas Angus and Hereford Ig effects influenced earlier calf birth dates (-4.3 +/- 1.9 and -4.1 +/- 1.9 d; P less than .05). Brahman combination Mh effects also influenced earlier calf birth dates (P less than .01). The Charolais Ig effect for calving assistance was positive (4.3 +/- 1.9%; P less than .05), whereas Angus-Brahman and Brahman-Charolais Mh effects for calving assistance were negative (-6.5 +/- 3.2 and -7.0 +/- 3.2%; P less than .05) and more desirable. Predicted reproductive traits for rotational mating systems were intermediate between predicted reproductive traits for two- and three-breed terminal crosses. Predicted calving and weaning rates were maximized when Brahaman first-cross and Charolais-Hereford cows were used in three-breed cross mating systems.

Animal Husbandry↗
PubMed2005

Marker-based quantitative genetics in the wild?: the heritability and genetic correlation of chemical defenses in eucalyptus.

Marker-based methods for estimating heritability and genetic correlation in the wild have attracted interest because traditional methods may be impractical or introduce bias via G x E effects, mating system variation, and sampling effects. However, they have not been widely used, especially in plants. A regression-based approach, which uses a continuous measure of genetic relatedness, promises to be particularly appropriate for use in plants with mixed-mating systems and overlapping generations. Using this method, we found significant narrow-sense heritability of foliar defense chemicals in a natural population of Eucalyptus melliodora. We also demonstrated a genetic basis for the phenotypic correlation underlying an ecological example of conditioned flavor aversion involving different biosynthetic pathways. Our results revealed that heritability estimates depend on the spatial scale of the analysis in a way that offers insight into the distribution of genetic and environmental variance. This study is the first to successfully use a marker-based method to measure quantitative genetic parameters in a tree. We suggest that this method will prove to be a useful tool in other studies and offer some recommendations for future applications of the method.

Australian Capital Territory↗
PubMed1995

Three experiments on mate choice in meadow voles (Microtus pennsylvanicus).

Species differences in selectivity with respect to mate choice have been hypothesized to be related to mating systems. Procedures used in 3 previous experiments on monogamous prairie voles (Microtus ochrogaster) and polygamous montane voles (M. montanus) were used with polygamous meadow voles (M. pennsylvanicus). The expectation was that meadow voles would show few preferences. Female meadow voles preferred mating with familiar versus unfamiliar males but displayed no preference for unmated versus mated males. Male meadow voles displayed no preference for unmated versus mated females. The results are partially consistent with the hypothesis that relates mate choice to social and mating system, as this polygamous species resembles polygamous montane voles species in 2 situations but is similar to monogamous prairie voles in the 3rd.

Animals↗
PubMedDate not supplied

Transfer of plasmid-mediated ampicillin resistance from Haemophilus to Neisseria gonorrhoeae requires an intervening organism.

Haemophilus species have been implicated as the source of plasmid-mediated ampicillin resistance in Neisseria gonorrhoeae. Previous attempts to transfer conjugally the resistance plasmids from Haemophilus species to N. gonorrhoeae have met with limited success. Using both biparental and triparental mating systems, it was found that transfer will occur if the commensal Neisseria species, Neisseria cinerea, is used as a transfer intermediate. This organism stably maintains resistance plasmids of Haemophilus and facilitates transfer of these plasmids to N. gonorrhoeae, in a triparental mating system, at a transfer frequency of 10(-8). Both Haemophilus ducreyi and N. gonorrhoeae carry mobilizing plasmids capable of mediating conjugal transfer of the same resistance plasmids. However, restriction endonuclease mapping and DNA hybridization studies indicate that the mobilizing plasmids are distinctly different molecules. Limited homology is present within the transfer region of these plasmids.

Ampicillin↗
PubMed2001

The effects of peptides on partner preference formation are predicted by habitat in prairie voles.

This study tested the hypothesis that intraspecific variations in mating systems are correlated with differences in the capacity of peripheral arginine vasopressin (AVP) to facilitate partner preferences. It has been hypothesized that differences in environmental conditions, Kansas being more xeric than Illinois, are responsible for some of the intraspecific differences in the mating systems between Kansas (KN) and Illinois (IL) prairie voles. We predicted that prairie voles from KN would be more behaviorally sensitive to peripheral AVP than prairie voles from IL. To test this hypothesis 60- to 120-day-old male and female, lab-reared, prairie voles originating from KN and IL received three subcutaneous injections of AVP or isotonic saline. Animals were then placed with an adult member of the opposite sex, designated a "partner," for a 1-hour period of cohabitation and subsequently tested for preference for the familiar partner versus a comparable stranger. Only KN males treated with AVP displayed a significant preference for the partner. Using the same experimental paradigm we also examined the ability of peripheral oxytocin (OT) to facilitate partner preference in KN prairie voles. OT facilitated partner preference in females, but not males. This finding was consistent with previous results describing the effects of peripheral OT in IL prairie voles. We also examined the hypothesis that the differential response of KN and IL males would be associated with differences in the distribution of AVP (V1a) receptors. However, there was no apparent difference in the distribution of V(1a) receptors between KN and IL males. The results of this study indicate that there is both intraspecific and intersexual variation in the regulation of social behavior in prairie voles. In addition, these findings suggest that the proximate causes of intraspecific variation may be predicted by knowledge of the habitat of origin.

Animals↗
PubMedDate not supplied

The evolution of alternative reproductive strategies: fitness differential, heritability, and genetic correlation between the sexes.

Paternity analyses using molecular markers have become standard in studies of mating systems, parentage, and kinship. In systems where individuals exhibit alternative mating strategies, molecular analyses have been productively used to estimate the reproductive success of each behavioral type and hence the fitness consequences to each individual. Here we review the fitness results in a system of five alternative mating strategies present in one population of side-blotched lizards (Uta stansburiana). Males in this population adopt one of three behavioral strategies that differ in their degree of territoriality and mate guarding. In contrast, females adopt one of two strategies that differ in offspring quantity and quality. We use paternity analyses to estimate the fitness of each morph, the heritability of reproductive strategy, and the correlation in strategy between the sexes and discuss the implications of our findings for the evolution and maintenance of reproductive polymorphism in this and other systems.

Animals↗
PubMed2003

Genetic evidence for female-biased dispersal in the bullfrog, Rana catesbeiana (Ranidae).

Sex-biased dispersal is an important but unexplored area of amphibian ecology. We predicted female-biased dispersal in the bullfrog (Rana catesbeiana) based on aspects of their mating system and tested this prediction using data from seven polymorphic DNA microsatellite loci. Allelic (F-statistics) and genotypic [assignment index, (AIc)] frequencies from nine Ontario populations support our prediction, although significant sex differences in inbreeding and variance of AIc were not detected. The diversity of mating systems found in amphibians represents an important avenue for investigating the relationship between reproductive systems, dispersal and phylogeny.

Animals↗
PubMed2006

A mixed-mating strategy in a hermaphroditic vertebrate.

Mixed-mating systems, in which hermaphrodites can either self-fertilize or outcross, are common in many species of plants and invertebrates and have been informative models for studying the selective forces that can maintain both inbreeding and outbreeding in populations. Here, we document a remarkable instance of evolutionary convergence to an analogous mixed mating system by a vertebrate, the mangrove killifish (Kryptolebias marmoratus). In this androdioecious species, most individuals are simultaneous hermaphrodites that characteristically self-fertilize, resulting in local populations that consist of (nearly) homozygous lines. Most demes are also genetically diverse, an observation traditionally attributed to de novo mutation coupled with high levels of inter-site migration. However, data presented here, from a survey of 35 microsatellite loci in Floridian populations, show that genotypic diversity also stems proximally from occasional outcross events that release 'explosions' of transient recombinant variation. The result is a local population genetic pattern (of extensive genotypic variety despite low but highly heterogeneous intra-individual heterozygosities) that differs qualitatively from the genetic architectures known in any other vertebrate species. Advantages of a mixed-mating strategy in K. marmoratus probably relate to this fish's solitary lifestyle and its ability to colonize new habitats.

Animals↗
PubMed2002

Anther-stigma separation is associated with inbreeding depression in Datura stramonium, a predominantly self-fertilizing annual.

Genetically based variation in outcrossing rate generates lineages within populations that differ in their history of inbreeding. According to some models, mating-system modifiers in such populations will demonstrate both linkage and identity disequilibrium with fitness loci, resulting in lineage-specific inbreeding depression. Other models assert that differences among families in levels of inbreeding depression are mainly attributable to random accumulation of genetic load, unrelated to variation at mating-system loci. We measured female reproductive success of selfed and outcrossed progeny from naturally occurring lineages of Datura stramonium, a predominantly self-fertilizing annual weed that has heritable variation in stigma-anther separation, a trait that influences selfing rates. Progeny from inbred lineages (as identified by high degree of anther-stigma overlap) showed equal levels of seed production, regardless of cross type. Progeny from mixed lineages (as identified by relatively high separation between anthers and stigma) showed moderate levels of inbreeding depression. We found a significant correlation between anther-stigma separation and relative fitness of selfed and outcrossed progeny, suggesting that family-level inbreeding depression may be related to differences among lineages in inbreeding history in this population. Negative inbreeding depression in putatively inbred lineages may be due in part to additive effects or to epistatic interactions among loci.

Datura stramonium↗
PubMed1990

The variance of sample heterozygosity.

The variance of sample heterozygosity, averaged over several loci, is studied in a variety of situations. The variance depends on the sampling implicit in the mating system as well as on that explicit in the loci scored and individuals sampled. There are also effects of allelic distributions over loci and of linkage or linkage disequilibrium between pairs of loci. Results are obtained for populations in drift and mutation balance, for infinite populations undergoing mixed self and random mating, and for finite monoecious populations with or without selfing. For unlinked loci in drift/mutation balance, variances appear to be lessened more by increasing the number of loci scored than by increasing the number of individuals sampled. For infinite populations under the mixed self and random mating system, however, the reverse is true. Methods for estimating the variance of sample heterozygosity are discussed, with attention being paid to unbalanced data where not all loci are scored in all individuals.

Alleles↗
PubMed2006

How seals divide up the world: environment, life history, and conservation.

Pinnipeds display a remarkable variation in life history adaptations while successfully inhabiting almost every marine environment. We explore how they have done this by grouping the world's pinniped species according to their environmental conditions, mating systems, lactation strategies, and timing of life histories. Next, we tested whether any of these clusters provide information about risk of extinction (using the International Union for Nature and the Conservation of Natural Resources status ranks). Seals at risk were not characterized by differences in lactation pattern (22% short vs. 46% long), mating system (24% multi-male vs. 35% harems), or timing of life history events (23% fast vs. 42% slow) but did differ based on four environmental groupings. Grouping traits (rather than seals) described two clusters: one that included the environmental trait, primary productivity, and a second one that included all other environmental variables (seasonality, latitude, and temperature). Based on this result and theoretical considerations, we plotted seals according to energy (primary productivity) and variation (seasonality) and found a pattern analogous to that of the same four groups determined by cluster analysis of all environmental variables. Of the two pinniped groups representing low variation (equatorial and high productivity), ten of 21 seal species have been designated at risk, in contrast to none of the 13 seal species adapted to high variation. We conclude that seals appear to be best adapted to seasonal environments and thus, conservation efforts may benefit by concentrating on species inhabiting less variable environments.

Animals↗
PubMed2006

Minimal selfing, few clones, and no among-host genetic structure in a hermaphroditic parasite with asexual larval propagation.

Little is known about actual mating systems in natural populations of parasites or about what constitutes the limits of a parasite deme. These parameters are interesting because they affect levels of genetic diversity, opportunities for local adaptation, and other evolutionary processes. We expect that transmission dynamics and the distribution of parasites among hosts should have a large effect on mating systems and demic structure, but currently we have mostly speculation and very few data. For example, infrapopulations (all the parasites in a single host) should behave as demes if parasite offspring are transmitted as a clump from host to host over several generations. However, if offspring are well mixed, then the parasite component population (all the parasites among a host population) would function as the deme. Similarly, low mean intensities or a high proportion of worms in single infections should increase the selfing rate. For species having an asexual amplification stage, transmission between intermediate and definitive (final) hosts will control the variance in clonal reproductive success, which in turn could have a large influence on effective sizes and rates of inbreeding. We examined demic structure, selfing rates, and the variance in clonal reproductive success in natural populations of Plagioporus shawi, a hermaphroditic trematode that parasitizes salmon. Overall levels of genetic diversity were very high. An a posteriori inference of population structure overwhelmingly supports the component population as the deme, rather than individual infrapopulations. Only a single pair of 597 adult individuals was identified as clones. Thus, the variance in clonal reproductive success was almost zero. Despite being hermaphroditic, P. shawi appears to be almost entirely outcrossing. Genetic estimates of selfing (<5%) were in accordance with the proportion of parasites from single infections. Thus, it appears that individual flukes outcross whenever possible and only resort to selfing when alone. Finally, our data support the hypothesis that aquatic transmission and the use of several intermediate hosts promotes high genetic diversity and well-mixed infrapopulations.

Animals↗
PubMed2000

The Bateman gradient and the cause of sexual selection in a sex-role-reversed pipefish.

As a conspicuous evolutionary mechanism, sexual selection has received much attention from theorists and empiricists. Although the importance of the mating system to sexual selection has long been appreciated, the precise relationship remains obscure. In a classic experimental study based on parentage assessment using visible genetic markers, more than 50 years ago A. J. Bateman proposed that the cause of sexual selection in Drosophila is 'the stronger correlation, in males (relative to females), between number of mates and fertility (number of progeny)'. Half a century later, molecular genetic techniques for assigning parentage now permit mirror-image experimental tests of the 'Bateman gradient' using sex-role-reversed species. Here we show that, in the male-pregnant pipefish Syngnathus typhle, females exhibit a stronger positive association between number of mates and fertility than do males and that this relationship responds in the predicted fashion to changes in the adult sex ratio. These findings give empirical support to the idea that the relationship between mating success and number of progeny, as characterized by the Bateman gradient, is a central feature of the genetic mating system affecting the strength and direction of sexual selection.

Animals↗
PubMed2005

Testosterone in females: mediator of adaptive traits, constraint on sexual dimorphism, or both?

When selection on males and females differs, the sexes may diverge in phenotype. Hormones serve as a proximate regulator of sex differences by mediating sex-biased trait expression. To integrate these perspectives, we consider how suites of traits mediated by the same hormone in both sexes might respond to selection. In male birds, plasma testosterone (T) varies seasonally and among species according to mating system. When elevated experimentally, it is known to enhance some components of fitness and to decrease others. We report that female T also varies seasonally and co-varies with male T. Female T is higher in relation to male T in sexually monomorphic species and is higher absolutely in females of species with socially monogamous mating systems, which suggests adaptation. We also consider the effect of experimentally elevated T on females and whether traits are sensitive to altered T. We hypothesize that sensitive traits could become subject to selection after a natural change in T and that traits with opposing fitness consequences in males and females could constrain dimorphism. Results from birds, including the dark-eyed junco (Junco hyemalis), reveal many sensitive traits, some of which appear costly and may help to account for observed levels of sexual dimorphism.

Animals↗
PubMed1994

Population genetic structure of the schistosome-vector snail Bulinus globosus: examining the role of genetic drift, migration and human activities.

Bulinus globosus, one of the intermediate hosts of the genus Schistosoma, is an hermaphrodite freshwater snail species. This species occupies different kinds of environments in Africa, which are generally subjected to large variations in water availability. The mating system of this species is outcrossing, although selfing has been suggested for one population. Here we investigate the genetic structure of populations of B. globosus in natural and human-modified environments from Niger and Ivory Coast using protein electrophoresis. Our goal is to analyse the respective role of the environment (genetic drift and gene flow), the mating system and human activities. Our results indicate a low intrapopulation polymorphism. A large differentiation among populations occurs on the scale of the whole study area whereas neighbouring populations can show little differentiation. These results point to the role of genetic drift and gene flow as the main factors shaping the genetic structure, with human activities playing a role occasionally.

Alleles↗
PubMed1990

Two-, three- and four-breed rotational crossbreeding of beef cattle: reproductive traits.

Reproductive data were collected on 4,596 cow exposures in a rotational crossbreeding study that spanned four generations (1970 through 1988). Angus (A), Brahman (B), Charolais (C) and Hereford (H) breeds were included in three two-breed (A-B, C-B and H-B), three three-breed (A-B-C, A-B-H and C-H-B) and one four-breed (A-B-C-H) rotational mating system. Contemporary straightbreds were produced each generation. Reproductive traits of interest were calving rate, calf survival, weaning rate, calf birth date and calving assistance. Overall means and standard errors for calving rate, calf survival, weaning rate, calf birth date and calving assistance were 82.1 +/- .6%, 92.8 +/- .4%, 76.2 +/- .6%, 50.4 +/- .3 d and 4.2 +/- .3%, respectively. Rotational mating systems had similar calving and calf survival rates that were greater (P less than .01) than those of straightbreds. Three- and four-breed rotation systems had similar weaning rates (81.5 +/- 1.1 and 80.8 +/- 2.0%) that were higher than those for two-breed rotations (77.1 +/- 1.2%). Two- and three-breed rotation systems had fewer assisted births (3.5 +/- .6 and 2.2 +/- .6%) than straightbreds (5.5 +/- .6%) and the four-breed rotation (5.4 +/- 1.0%). Three-breed rotation calves were born earlier in the calving season (46.8 +/- .6 d; P less than .05) than straightbred, two-breed or four-breed rotation calves (51.8 +/- .6, 52.1 +/- .6 and 51.1 +/- 1.0 d). Hereford-Brahman two-breed rotation cows had higher (P less than .05) calving and weaning rates than A-B or C-B two-breed rotation cows (87 +/- .4 vs 81.9 +/- 1.9 and 81.5 +/- 1.8%; 81.7 +/- 2.0 vs 76.4 +/- 2.1 and 74.1 +/- 2.0%). All three-breed rotation combinations had similar calving, calf survival and weaning rates, assistance at calving and calf birth dates. Rotational combinations tended to be more superior (P less than .05) to weighted purebred means for calving, calf survival and weaning rates than for calf birth date and calving assistance.

Analysis of Variance↗
PubMed2004

Multiple paternity in clutches of common lizard Lacerta vivipara: data from microsatellite markers.

The common lizard (Lacerta vivipara) is a small live-bearing lacertid that reproduces once a year. In order to document the poorly known mating system of this species, we present here an assessment of multiple paternity using microsatellite markers. Paternities were established within 122 clutches belonging to two wild populations from contrasted areas and to four seminatural enclosed populations. The proportion of multiply sired clutches was found to be very high (between 50.0% and 68.2%) and similar among populations, which suggests that the mating system of this species may be insensitive to environmental and population conditions.

Animals↗
PubMed2005

Mating patterns of a subdivided population of the andean oak (Quercus humboldtii Bonpl., Fagaceae).

Mating patterns play a critical role in the maintenance of genetic variation. We analyzed the mating system in a recently fragmented population of the Andean oak (Quercus humboldtii) using four microsatellite loci. Five fragments in northeastern Colombia, South America, were selected consisting of 30.4 trees on average. We sampled about 30 seeds from three target trees in each fragment and genotyped them with four microsatellite loci with a total of 40 alleles across loci. Progenies were analyzed under the mixed mating system model (MLTR program) and the TwoGener pollen pool structure analyses. The number of unshared pollen donors per family (Nu) was estimated using gametotypic counts with the program HAPLOTYPES. Low selfing (3%) is occurring at the population and fragment level. Biparental inbreeding is present (4.9%), but reduced, in the largest fragment. The average pollen neighborhood size (Nep = 5.1 to 6.1) appears comparable to other oak species in sparse landscapes. In contrast, Nu consists of 2 to 4 main donors, although up to 12 are possible, with the mode positively correlated with fragment size. The Andean oak appears to be a resilient species capable of tolerating population subdivision, provided landscapes include large fragments.

Colombia↗