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PubMed2002

Variation in female mate choice within guppy populations: population divergence, multiple ornaments and the maintenance of polymorphism.

The evolutionary significance of variation in mate choice behaviour is currently a subject of some debate and considerable empirical study. Here, I review recent work on variation within and among guppy (Poecilia reticulata) populations in female mate choice and mating preferences. Empirical results demonstrate that there is substantial variation within and among populations in female responsiveness and choosiness, and much of this variation is genetic. Evidence for variation in preference functions also exists, but this appears to be more equivocal and the relative importance of genetic variation is less clear cut. In the second half of this review I discuss the potential significance of this variation to three important evolutionary issues: the presence of multiple male ornaments, the maintenance of polymorphism and divergence in mate recognition among populations. Studies of genetic variation in mate choice within populations indicate that females have complex, multivariate preferences that are able to evolve independently to some extent. These findings suggest that the presence of multiple male ornaments may be due to multiple female mating preferences. The extreme polymorphism in male guppy colour patterns demands explanation, yet no single satisfactory explanation has yet emerged. I review several old ideas and a few new ones in order to identify the most promising potential explanations for future empirical testing. Among these are negative frequency dependent selection, environmental heterogeneity coupled with gene flow, and genetic constraints. Last, I review the relative extent of within and among-population variation in mate choice and mating preferences in order to assess why guppies have not speciated despite a history of isolation and divergence. I argue that variation within guppy populations in mate choice and enhanced mating success of new immigrants to a pool are major impediments to population divergence of the magnitude that would be required for speciation to occur.

Animals↗

PubMed2005

Paternal genetic effects on offspring fitness are context dependent within the extrapair mating system of a socially monogamous passerine.

Avian extrapair mating systems provide an interesting model to assess the role of genetic benefits in the evolution of female multiple mating behavior, as potentially confounding nongenetic benefits of extrapair mate choice are seen to be of minor importance. Genetic benefit models of extrapair mating behavior predict that females engage in extrapair copulations with males of higher genetic quality compared to their social mates, thereby improving offspring reproductive value. The most straightforward test of such good genes models of extrapair mating implies pairwise comparisons of maternal half-siblings raised in the same environment, which permits direct assessment of paternal genetic effects on offspring traits. But genetic benefits of mate choice may be difficult to detect. Furthermore, the extent of genetic benefits (in terms of increased offspring viability or fecundity) may depend on the environmental context such that the proposed differences between extrapair offspring (EPO) and within-pair offspring (WPO) only appear under comparatively poor environmental conditions. We tested the hypothesis that genetic benefits of female extrapair mate choice are context dependent by analyzing offspring fitness-related traits in the coal tit (Parus ater) in relation to seasonal variation in environmental conditions. Paternal genetic effects on offspring fitness were context dependent, as shown by a significant interaction effect of differential paternal genetic contribution and offspring hatching date. EPO showed a higher local recruitment probability than their maternal half-siblings if born comparatively late in the season (i.e., when overall performance had significantly declined), while WPO performed better early in the season. The same general pattern of context dependence was evident when using the number of grandchildren born to a cuckolding female via her female WPO or EPO progeny as the respective fitness measure. However, we were unable to demonstrate that cuckolding females obtained a general genetic fitness benefit from extrapair fertilizations in terms of offspring viability or fecundity. Thus, another type of benefit could be responsible for maintaining female extrapair mating preferences in the study population. Our results suggest that more than a single selective pressure may have shaped the evolution of female extrapair mating behavior in socially monogamous passerines.

Animals↗

PubMed2005

Relative abundance and the species-specific reinforcement of male mating preference in the Chrysochus (Coleoptera: Chrysomelidae) hybrid zone.

Most studies of reinforcement have focused on the evolution of either female choice or male mating cues, following the long-held view in sexual selection theory that mating mistakes are typically more costly for females than for males. However, factors such as conspecific sperm precedence can buffer females against the cost of mating mistakes, suggesting that in some hybrid zones mating mistakes may be more costly for males than for females. Thus, the historical bias in reinforcement research may underestimate its frequency. In this study, we present evidence that reinforcement has driven the evolution of male choice in a hybrid zone between the highly promiscuous leaf beetles Chrysochus cobaltinus and C. auratus, the hybrids of which have extremely low fitness. In addition, there is evidence for male choice in these beetles and that male mating mistakes may be costly, due to reduced opportunities to mate with conspecific females. The present study combines laboratory and field methods to quantify the strength of sexual isolation, test the hypothesis of reproductive character displacement, and assess the link between relative abundance and the strength of selection against hybridization. We document that, while sexual isolation is weak, it is sufficient to produce positive assortative mating. In addition, reproductive character displacement was only detected in the relatively rare species. The strong postzygotic barriers in this system are sufficient to generate the bimodality that characterizes this hybrid zone, but the weak sexual isolation is not, calling into question whether strong prezygotic isolation is necessary for the maintenance of bimodality. Growing evidence that the cost of mating mistakes is sufficient to shape the evolution of male mate choice suggests that the reinforcement of male mate choice may prove to be a widespread occurrence.

Animals↗

PubMed2006

Assortative mating for fitness and the evolution of recombination.

To understand selection on recombination, we need to consider how linkage disequilibria develop and how recombination alters these disequilibria. Any factor that affects the development of disequilibria, including nonrandom mating, can potentially change selection on recombination. Assortative mating is known to affect linkage disequilibria but its effects on the evolution of recombination have not been previously studied. Given that assortative mating for fitness can arise indirectly via a number of biologically realistic scenarios, it is plausible that weak assortative mating occurs across a diverse set of taxa. Using a modifier model, we examine how assortative mating for fitness affects the evolution of recombination under two evolutionary scenarios: selective sweeps and mutation-selection balance. We find there is no net effect of assortative mating during a selective sweep. In contrast, assortative mating could have a large effect on recombination when deleterious alleles are maintained at mutation-selection balance but only if assortative mating is sufficiently strong. Upon considering reasonable values for the number of loci affecting fitness components, the strength of selection, and the mutation rate, we conclude that the correlation in fitness between mates is unlikely to be sufficiently high for assortative mating to affect the evolution of recombination in most species.

Animals↗

PubMed1993

Optimizing management of natural and artificial matings in swine.

A successful mating involves the coordination of many physiological events including insemination, gamete transport and ovulation. As more basic information about these processes becomes available, it is apparent that there are opportunities for manipulating these physiological events and enhancing the reproductive success of natural and artificial matings. The primary intent of this review is to examine the effectiveness of several of these strategies, as determined by their influence on farrowing rate and litter size. It is evident that the timing, duration and pattern of ovulation in pigs are extremely variable. Thus, increasing the frequency and changing the timing of matings during oestrus has received renewed interest. In general, if a female exhibits oestrus for more than 1 day, then increasing the frequency of matings has a greater influence on reproductive performance than does altering the timing of matings. In addition, litter size is more responsive to increased mating frequencies than is farrowing rate. Increasing the number of matings per oestrus via the use of combinations of natural service and artificial insemination, compared with the use of either alone, appears to enhance reproductive performance. It has been well documented that several aspects of the mating process itself can advance the onset of ovulation and enhance sperm transport and storage in the female reproductive tract. As a result, the use of these stimuli in conjunction with natural and artificial matings provide opportunities for enhancing fecundity. Pre- and post-breeding treatments with vasectomized boars, nonviable semen, oestrogens and seminal plasma have all been reported to increase farrowing rate and litter size. With artificial insemination, additions of prostaglandins, oxytocin, oestrogens and leucocytes to semen have been reported to enhance reproductive performance, albeit with varying degrees of success. Personnel and boar needs are important components in optimizing breeding management. Estimates of these needs for artificial and natural matings are discussed.

Animal Husbandry↗

PubMed1995

Hot and cold mate drinking and esophageal cancer in Paraguay.

A hospital-based case-control study, including 131 cases of esophageal cancer and 381 controls, was carried out in Paraguay to investigate the role of hot and cold mate drinking in esophageal cancer risk. Detailed information on mate drinking and on tobacco smoking, alcohol consumption, and dietary habits was obtained by interview. Amount and duration of cold or hot mate drinking were not associated with esophageal cancer risk. However, temperature at which mate was drunk was significantly associated with risk. As compared to drinkers of warm or hot mate, drinkers of very hot mate had an increased risk for esophageal cancer even after adjusting for the strong effects of alcohol and tobacco consumption (adjusted odds ratio = 2.4; 95% confidence interval = 1.3-4.3). This effect seemed to be mainly due to the temperature at which mate cocido (one of the two ways in which hot mate is prepared) was drunk (odds ratio = 6.5; 95% confidence interval = 3.2-12.2). As expected, very strong dose-response associations were found for alcohol consumption and cigarette smoking. After correcting for these and the consumption of other food groups, diets rich in fats and red meats, especially beef, were associated with esophageal cancer risk. In conclusion, the findings from this study suggest that cold mate drinking does not increase the risk of esophageal cancer. This study identifies the very hot temperature at which mate is drunk, and not the amount or the duration, as an important risk factor for esophageal cancer in this population. Alcohol drinking and tobacco smoking remain, nevertheless, the main risk factors for esophageal cancer in Paraguay.

Adult↗

PubMed2001

Mating-type genes for basidiomycete strain improvement in mushroom farming.

Mushroom production is dependent on the quality of the spawn used to inoculate the cultures. In order to produce high-quality spawn, breeding programs for strains resistant to certain diseases and able to form high-quality fruit bodies under standard growth conditions are necessary. The investigation of the molecular basis for mating provides access to the use of mating-type genes in order to facilitate breeding. For research purposes, two mushroom-forming homobasidiomycetes have been used due to their easy cultivation and sexual propagation on defined minimal media: Schizophyllum commune and Coprinus cinereus. The mating-type genes control formation of the dikaryon from two haploid strains. Only the dikaryon is fertile and able to form mushrooms under the right environmental conditions. These genes are now used in mating-type-assisted breeding programs for economically important mushrooms, especially the white button mushroom, Agaricus bisporus, and the oyster mushroom, Pleurotus ostreatus, aiming at high-yield and high-quality standard mushroom production. Most mushroom species posses two mating-type loci that control their breeding. The genes encoded in the A loci lead to the formation of transcription factors that belong to the class of homeodomain proteins. Active transcription factors are formed by heterodimerization of two proteins of different allelic specificities. In nature, this is only the case if two cells of different mating type have fused to combine the different proteins in one cytoplasm. While fusion in homobasidiomycetes is found irrespectively of mating type, exchange of nuclei between mating mycelia is dependent on the products of the B mating-type loci. The B genes form a pheromone and receptor system that enables the fungi to initiate nuclear migration. The molecular details of the two genetic systems controlling breeding in basidiomycetes are presented in this review.

Basidiomycota↗

PubMed2001

The mating system of the fungus Cryphonectria parasitica: selfing and self-incompatibility.

Although the genetic components of mating systems in fungi are well understood as laboratory phenomena, surprisingly little is known about their function in nature or about their role in determining mating patterns and population genetic structure. Our study of the mating system of the haploid ascomycete fungus, Cryphonectria parasitica, resulted in the following. (1) Laboratory crosses among 20 isolates, chosen randomly from North America and China, resolved into two incompatibility groups (occurring on both continents), confirming that C. parasitica has a diallelic, bipolar sexual self-incompatibility system, typical of other self-incompatible Ascomycetes, in which mating is only successful between isolates of opposite mating type. (2) PCR-based markers for mating-type alleles correlated perfectly with mating-type phenotypes of individual isolates. (3) Three genotypes, isolated from natural populations in Virginia and West Virginia, were inoculated onto chestnut trees in two sites in West Virginia and were confirmed to have self-fertilized and outcrossed in both sites. (4) Ten isolates, of a total of over 200 assayed, were confirmed to have self-fertilized in the laboratory, albeit at very low frequency. Five of these 10 isolates were ramets of a single genet, suggesting a genetic basis underlying the proclivity to self-fertilize in the laboratory. (5) Self-fertilization could not be induced in the laboratory with exudates (ostensibly containing pheromones) from isolates of opposite mating type. These results demonstrate that, a sexual self-incompatibility system notwithstanding, self-fertilization occurs under both laboratory and field conditions in C. parasitica. The disparity between observations of frequent selfing in nature and rare selfing in the laboratory suggests that the mating system is under ecological as well as genetic control.

Ascomycota↗

PubMed1979

A mutation that permits the expression of normally silent copies of mating-type information in Saccharomyces cerevisiae.

Studies of heterothallic and homothallic strains of Saccharomyces cerevisiae have led to the suggestion that mating-type information is located at three distinct sites on chromosome 3, although only information at the mating-type (MAT) locus is expressed (Hicks, Strathern and Herskowitz, 1977). We have found that the recessive mutation cmt permits expression of the normally silent copies of mating-type information at the HMa and HM alpha loci. In haploid strains carrying HMa and HM alpha, the cmt mutation allows the simultaneous expression of both a and alpha information, leading to a nonmating ("MATa/MAT alpha") phenotype. The effects of cmt can be masked by changing the mating-type information at HMa or HM alpha. For example, a cell of genotype MATa hma HM alpha cmt has an a mating type, while a MAT alpha hma HM alpha cmt strain is nonmating. Expression of mating-type information at the HM loci can correct the mating and sporulation defects of the mata* and mat alpha 10 alleles. Meiotic segregants recovered from cmt/cmt diploids carrying the mat mutations demonstrate that these mutants are not "healed" to normal MAT alleles, as is the case in parallel studies using the homothallism gene HO.--All of the results are consistent with the notion that the HMa and hm alpha alleles both code for alpha information, while HM alpha and hma both code for a information. The cmt mutation demonstrates that these normally silent copies of mating-type and sporulation information can be expressed and that the information at these loci is functionally equivalent to that found at MAT. The cmt mutation does not cause interconversions of mating-type alleles at MAT, and it is not genetically linked to MAT, HMa, HM alpha or HO. In cmt heterozygotes, cmt becomes homozygous at a frequency greater than 1% when the genotype at the MAT locus is mata*/MAT alpha or mat alpha 10/MATa.

Alleles↗

PubMed1984

Mating pheromone-induced alteration of cell surface proteins in the heterobasidiomycetous yeast Tremella mesenterica.

Mating pheromone-induced alteration of the cell surface proteins of haploid cells, presumed to play crucial roles in the specific cell-cell interactions during sexual conjugation of Tremella mesenterica , was investigated. Exposed surface proteins were revealed by lactoperoxidase-catalyzed iodination in combination with polyacrylamide gel electrophoresis and autoradiography. From comparison of the molecular species of 125I-labeled surface proteins of the vegetative and the gamete (mating pheromone-treated) cells of the two compatible mating types (ab and AB), it was suggested that a striking change in cell surface structure occurs during the differentiation; although labeled protein species of the vegetative cells of the two mating types were indistinguishable, several new species, both mating type specific and nonspecific, appeared in the gamete cells. Turnover of the labeled proteins of the vegetative cells was negligible, whereas that of the gamete cells was rapid with release of low-molecular-weight labeled proteins in the medium. A role for the labeled surface proteins of the gamete cells in the cell-cell interactions during sexual conjugation was suggested by the following: the surface changes were induced by mating pheromone; the labeled proteins were preferentially localized on the surface of the mating tube; the labeled species appeared sequentially during the differentiation; and mating type-specific species were present in both mating types.

Animals↗

PubMed2002

Geographic distribution of mating type alleles of Cryptococcus neoformans in four areas of the United States.

To better understand the epidemiology and population structure of Cryptococcus neoformans, we determined mating types for 358 C. neoformans strains isolated through the active surveillance program from 1992 to 1994 in four geographic areas in the United States: San Francisco, California; Georgia; Texas; and Alabama. Two assays were used to determine mating types: (i) crossing with standard laboratory tester strains JEC20 and JEC21 on V8 agar medium; and (ii) PCR with the mating type alpha allele-specific primer of the STE12 gene and with serotype (A and D)- and mating type (a and alpha)-specific primers of the STE20 gene. Using these two methods, we found that this sample consisted of the following: (i) 324 serotype A, mating type (MAT) alpha (Aalpha) strains; (ii) 12 serotype D, alpha (Dalpha) strains; (iii) 14 serotype AD strains with mating type alleles Aa and Dalpha (AaDalpha); (iv) 2 serotype AD strains with mating type alleles Aalpha and Da (AalphaDa); (v) 3 serotype B, alpha (Balpha) strains; and (vi) 3 serotype AD strains but with only one mating type allele. No strain with MATa was found within serotype A, B, or D in this collection. Interestingly, 14 of the 19 serotype AD strains contained the Aa allele at the STE20 locus; 13 of these 14 were from San Francisco. Our results suggest that the environment in San Francisco might contain Aa strains capable of mating with Dalpha strains. In addition, our result demonstrate that the sample from San Francisco had a significantly higher proportion of self-fertile strains than those from the other three areas.

Alleles↗

PubMed1982

Mating-defective ste mutations are suppressed by cell division cycle start mutations in Saccharomyces cerevisiae.

Temperature-sensitive mutants which arrest in the G1 phase of the cell cycle have been described for the yeast Saccharomyces cerevisiae. One class of these mutants (carrying cdc28, cdc36, cdc37, or cdc39) forms a shmoo morphology at restrictive temperature, characteristic of mating pheromone-arrested wild-type cells. Therefore, one hypothesis to explain the control of cell division by mating factors states that mating pheromones arrest wild-type cells by inactivating one or more of these CDC gene products. A class of mutants (carrying ste4, ste5, ste7, ste11, or ste12) which is insensitive to mating pheromone and sterile has also been described. One possible function of the STE gene products is the inactivation of the CDC gene products in the presence of a mating pheromone. A model incorporating these two hypotheses predicts that such STE gene products will not be required for mating in strains carrying an appropriate cdc lesion. This prediction was tested by assaying the mating abilities of double mutants for all of the pairwise combinations of cdc and ste mutations. Lesions in either cdc36 or cdc39 suppressed the mating defect due to ste4 and ste5. Allele specificity was observed in the suppression of both ste4 and ste5. The results indicate that the CDC36, CDC39, STE4, and STE5 gene products interact functionally or physically or both in the regulation of cell division mediated by the presence or absence of mating pheromones. The cdc36 and cdc39 mutations did not suppress ste7, ste11, or ste12. Lesions in cdc28 or cdc37 did not suppress any of the ste mutations. Other models of CDC and STE gene action which predicted that some of the cdc and ste mutations would be alleles of the same locus were tested. None of the cdc mutations was allelic to the ste mutations and, therefore, these models were eliminated.

Cell Division↗

PubMed1997

Mating types and sexual development in filamentous ascomycetes.

The progress made in the molecular characterization of the mating types in several filamentous ascomycetes has allowed us to better understand their role in sexual development and has brought to light interesting biological problems. The mating types of Neurospora crassa, Podospora anserina, and Cochliobolus heterostrophus consist of unrelated and unique sequences containing one or several genes with multiple functions, related to sexuality or not, such as vegetative incompatibility in N. crassa. The presence of putative DNA binding domains in the proteins encoded by the mating-type (mat) genes suggests that they may be transcriptional factors. The mat genes play a role in cell-cell recognition at fertilization, probably by activating the genes responsible for the hormonal signal whose occurrence was previously demonstrated by physiological experiments. They also control recognition between nuclei at a later stage, when reproductive nuclei of each mating type which have divided in the common cytoplasm pair within the ascogenous hyphae. How self is distinguished from nonself at the nuclear level is not known. The finding that homothallic species, able to mate in the absence of a partner, contain both mating types in the same haploid genome has raised more issues than it has resolved. The instability of the mating type, in particular in Sclerotinia trifolorium and Botrytinia fuckeliana, is also unexplained. This diversity of mating systems, still more apparent if the yeasts and the basidiomycetes are taken into account, clearly shows that no single species can serve as a universal mating-type model.

Amino Acid Sequence↗

PubMed2003

Roles of sexual cell agglutination in yeast mass mating.

The agalpha1 mutant MAT alpha cells specifically lack the cell surface alpha-type sexual agglutination substance, which is also called alpha-agglutinin. Because the mutant cells (MATalpha agalpha1) can not form aggregates with MATa cells, MATalpha agalpha1 cells are unable to mate with MATa cells when they are co-inoculated in a liquid medium, and the mating is attenuated on solid medium. The attenuated mating ability shown in the previous studies gave us a vague idea about a physiological function of the sexual agglutinability. In order to solve the question, mating behavior of MATalpha agalpha1 cells was investigated here under conditions where the contact between MATa and MAT alpha cells is assisted by physical methods. A synthetic mutation agalpha1::URA3 was constructed and used as well as agalpha1-1 for this study to ensure the genetic defect. When a mixture of MATa and MAT alpha cells was kept on filter membrane placed on relatively dry agar medium, even agalpha1::URA3 mutant cells mated as efficiently as the wild type (AGalpha1) cells did. On filter membrane placed on moist agar medium, agalpha1 mutants mated 10-fold less efficiently than wild type cells did. The mutant cells mated 10000-time less efficiently than the wild type cells in a pellet formed by brief low speed centrifugation. In contrast, the wild type MATalpha cells mated well under all conditions tested. Under the pellet condition, a mixture of MATa and MATalpha AG alpha1 cells formed an extended and cotton-like pellet while a mixture of MATa and MATalpha agalpha1 cells formed a compact and tight pellet. These results suggest that sexual cell agglutination contributes not only to cell contact between MATa and MAT alpha cells thereby stabilizing a-alpha cell pairs, but also to construction of a uniquely organized ultra structure favorable for zygote formation and subsequent growth of diploid cells. The mating specific extended pellet formation was observed also in 4 pairs of a and alpha strains in ascosporogenous yeast genera Hansenula and Pichia.

Agglutination↗

PubMed1999

Cytofluorometry and fluorescence confocal laser scanning microscopy (CLSM) in the study of neutral lipid dynamics in Paramecium primaurelia mating types during cell line development.

BACKGROUND: In Paramecium primaurelia, an exconjugant cell can produce two lines with different mating capacities. Mating type II cells can form a higher food vacuole number and digest the nutrient taken up in a shorter time; thus, mating type II cells grow at a faster rate than do mating type I cells. The present study was done to determine whether cells that ingest more nutrients also have a larger amount of storage lipids. METHODS: Quantitative and qualitative determinations of neutral lipids were obtained by means of cytofluorometry and fluorescence confocal laser scanning microscopy (CLSM), respectively, by using nile red on cells in different physiologic states. RESULTS: Lipid droplet number and neutral lipid content were higher in mating type II cells than in mating type I cells in the early logarithmic growth phase (i.e., immature well-fed cells). These values were reversed during the middle and the late logarithmic phases and became equal in the stationary phase (i.e., mature starved cells). In well-fed cells maintained with food excess, differences in neutral lipid content between the two mating types also were present in mature cells. CONCLUSIONS: Although differences between mating type I and mating type II lines were not correlated to cell size, a relation was found between lipid content and food ingestion capacity. A depletion of bacteria in the culture medium could be responsible for the lack of differences in mature starved cells. CLSM allowed us to gather volume information about the lipid droplet distribution within the cell.

Animals↗

PubMed2000

A preliminary study of spatial distribution and mating system of pygmy mouse lemurs (Microcebus cf. myoxinus).

According to current hypotheses on the evolution of life history traits and social systems of Malagasy lemurs, nocturnality is associated with a solitary lifestyle and a polygynous or promiscuous mating system. Recent studies, however, have indicated that this may not be true of all lemurs. The goal of this study was to investigate the sociality and the mating system of pygmy mouse lemurs (Microcebus cf myoxinus), which are the smallest known primates, and which retain characteristics of the most primitive primates. I compared my findings with data on the sympatric Microcebus murinus and Cheirogaleus medius. Observational, morphometric and spatial distribution data were obtained by a radiotracking study in 1994, and from a capture-recapture study conducted during 1995/96. Pygmy mouse lemurs usually slept alone in a tangle of vegetation. During the mating season, sleeping sites of males were distributed over a much broader area than were female sites, indicating that male home ranges are larger than those of females. The home ranges of males overlapped during the mating season, and males occasionally roamed over long distances during a single night. Pygmy mouse lemurs forage primarily alone. Analysis of estrus stages indicate that female cycles are unsynchronized during the mating season. There was a lack of sexual dimorphism in body size but not in body mass. Males were heavier than females during the reproductive season but lighter than females the rest of the year. Testes of males varied in size seasonally and enlarged significantly during the mating season. The presence of a vaginal sperm plug in a female indicated the importance of preventing additional matings in this species. Thus pygmy mouse lemurs follow the predictions derived from sexual selection theory for multi-male mating systems with promiscuous matings and male sperm competition.

Animals↗

PubMed1997

Temporal aspects in the development of Belding's ground squirrels' litter-mate preferences

Four experiments were conducted to determine how experience around the time of natal emergence affected the development of litter-mate preferences in juvenile Belding's ground squirrels, Spermophilus beldingiSocial preferences were ascertained by observing six captive groups, each housed in outdoor enclosures beginning at natal emergence, and recording the frequency of dyadic play. Juveniles preferred their litter-mates as play partners on day 1 above-ground, demonstrating that pre-emergent interactions influenced social development. Whether cross-fostered young displayed play-partner preferences based on relatedness and rearing history depended on when young were exchanged with respect to natal emergence, which suggests that social development is especially sensitive to experience shortly before natal emergence. Juveniles do not display litter-mate preferences if they emerge into an environment from which dams have been removed, but in the present study, if juveniles interacted for 1 week before dams were withdrawn from enclosures, then litter-mate preferences were manifested both before and after dams were withdrawn. These results suggest that a foundation for litter-mate preferences is laid before natal emergence, and that preferences are solidified by interactions between litter-mates on their first few days above-ground. Finally, non-litter-mates that interacted with each other shortly after natal emergence were preferred social partners during later encounters compared with non-litter-mates denied the opportunity to interact shortly after emergence. Collectively, the four experiments demonstrate that social experience around the time of natal emergence is crucial to the developmental process that generates litter-mate preferences in S. beldingi1997 The Association for the Study of Animal Behaviour

Journal Article↗

PubMed1997

Straight-line movement and competitive mate searching in prairie rattlesnakes, Crotalus viridis viridis

Males compete in various ways for mating and reproductive success. Phylogenetic factors and local ecology affect female spatial and temporal distributions, which in turn influence the form of male competition, sexual selection and mating systems. In prairie rattlesnake, Crotalus viridis viridispopulations where (1) males seek females during a brief reproductive period, (2) females are relatively few, and (3) females are widely and unpredictably distributed spatially into small discrete clusters, males should show efficient mate searching more so than time-consuming 'handling' (e.g. fighting, mate persuasion). Natural history studies and computer and mathematical modelling generate this expectation. This long-term field study of prairie rattlesnakes in Wyoming indicated that straight-line (i.e. fixed-bearing) movement by males is critical for mate location and, thus, for mating success. Males that searched along straight-line paths located and mated with more females than those having less straight movement paths. Fighting was observed rarely, and no relationship was found between males' success at mate location and body mass and/or snout-vent length. Thus a range of traits may mediate competition and mating success among male snakes.

Journal Article↗