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PubMed1996

Identification of major histocompatibility complex genes in the guppy, Poecilia reticulata.

The guppy, Poecilia reticulata, a teleostean fish of the order Cyprinodontiformes, has been used extensively in studies of host-parasite interactions, courtship behavior, and mating preference, as well as in ecological and evolutionary genetics. A related species was among the first poikilotherm vertebrates to be used in the study of histocompatibility genes. All these studies could benefit from the identification and characterization of the guppy major histocompatibility complex (Mhc) genes. Here, both class I and class II genes of the guppy are described. The number of expressed loci, as determined by representation of clones in a cDNA library, sequencing, and Southern blot analysis, may be low in both Mhc classes: combined evidence suggests that there may be one expressed class II locus only and one or two expressed class I loci. The variability of aquaristic guppy stocks is very low: only three and two genes have been detected at the class I and class II loci, respectively, in the stocks examined. This genetic paucity is most likely the consequence of breeding practices employed by aquarists and commercial establishments. Limited sampling of wild guppy populations revealed extensive Mhc polymorphism at loci of both classes in nature. Comparison of guppy Mhc sequences with those of other vertebrates has revealed the existence of a set of insertions/deletions which can be used as characters in cladistic analysis to infer phylogenetic relationships among vertebrate taxa and the Mhc genes themselves. These indels are particularly frequent in the regions coding for the loops of alpha 1 and alpha 2 domains of class I proteins.

Amino Acid Sequence↗

PubMed2005

Egg-laying preference of female fungus gnat Bradysia sp. nr. coprophila (Diptera: Sciaridae) on three different soilless substrates.

Fungus gnats, Bradysia spp., are major insect pests in greenhouses. Adult female fungus gnats prefer to lay eggs in growing medium that is microbially active or that contains high amounts of peat moss or hardwood bark. However, egg-laying preference has not been demonstrated quantitatively. This study was designed to determine whether fungus gnat Bradysia sp. nr. coprophila females prefer any of the three soilless growing media provided. The three soilless growing media tested were Metro-Mix 560 with Scott's Coir, Sunshine LC1 Mix, and Universal SB 300 Mix. Initially, the egg-laying potential of the fungus gnat species used in this study was assessed by dissecting mated females after 24, 48, and 72 h. For the egg-laying preference experiment, adults that emerged from pupae were aspirated into a plastic vial, sexed, and then allowed to mate for 24 h. Individual mated females were released into an experimental chamber (15 by 15 by 5-cm plastic container) consisting of four 6-cm petri dishes, three of which contained soilless growing media and one with filter paper (control). In total, there were 50 experimental chambers, with each chamber representing a replication. Females remained in the experimental chambers for 48 h after which the growing media were processed using a flotation/extraction method. The number of eggs laid by female fungus gnats ranged from 21 to 217 with most eggs recovered after 48 h (141.0 +/- 9.3). There were no significant differences among the three soilless growing media in terms of number of eggs laid, although all three growing media were significantly different from the filter paper with higher numbers of eggs laid in the soilless growing media than the filter paper. Despite no significant difference among the growing media in the number of eggs laid, fungus gnat females tended to lay eggs more often, based on the number of petri dishes in which at least one egg was laid, in Metro-Mix 560 (86%) than Sunshine LC1 (66%), Universal SB 300 (52%), or filter paper (18%). Based on the results of this study, female fungus gnats may not prefer a specific growing medium for oviposition. However, fungus gnat females may rely on other factors not tested in this study such as moisture content and volatiles emitted from growing media in their decision where to lay eggs.

Animals↗

PubMed2000

Reproductive character displacement and speciation in periodical cicadas, with description of new species, 13-year Magicicada neotredecem.

Acoustic mate-attracting signals of related sympatric, synchronic species are always distinguishable, but those of related allopatric species sometimes are not, thus suggesting that such signals may evolve to "reinforce" premating species isolation when similar species become sympatric. This hypothesis predicts divergences restricted to regions of sympatry in partially overlapping species, but such "reproductive character displacement" has rarely been confirmed. We report such a case in the acoustic signals of a previously unrecognized 13-year periodical cicada species, Magicicada neotredecim, described here as a new species (see Appendix). Where M. neotredecim overlaps M. tredecim in the central United States, the dominant male call pitch (frequency) of M. neotredecim increases from approximately 1.4 kHz to 1.7 kHz, whereas that of M. tredecim remains comparatively stable. The average preferences of female M. neotredecim for call pitch show a similar geographic pattern, changing with the call pitch of conspecific males. Magicicada neotredecim differs from 13-year M. tredecim in abdomen coloration, mitochondrial DNA, and call pitch, but is not consistently distinguishable from 17-year M. septendecim; thus, like other Magicicada species, M. neotredecim appears most closely related to a geographically adjacent counterpart with the alternative life cycle. Speciation in Magicicada may be facilitated by life-cycle changes that create temporal isolation, and reinforcement could play a role by fostering divergence in premating signals prior to speciation. We present two theories of Magicicada speciation by life-cycle evolution: "nurse-brood facilitation" and "life-cycle canalization."

Acoustic Stimulation↗

PubMed1987

Coincidence detection in auditory neurons: a possible mechanism to enhance stimulus specificity in the grassfrog.

It is still a matter of debate whether neurons in the higher central nervous system of anurans become progressively more sharply tuned to sounds that have a behavioral importance or that such coding is performed by (small) groups of neurons. The approach we have taken to investigate this matter comprises simultaneous single-unit recording using two microelectrodes in the auditory midbrain of the grassfrog. The present study deals with 96 pairs of units responding to an ensemble of natural and synthetic mating calls in which carrier frequency and pulse-repetition rate were varied. This ensemble was presented without noise and also with background noise of increasing intensity. The spike trains were analysed for correlations between their firings. In 34 pairs (35%) a functional connection, mostly common input, was present. By selecting one of the units of a pair as a trigger it was investigated which window for a coincidence analysis would result in enhanced specificity for the unit pair. Such an analysis based on a logical AND operation could be a model for the action of a neuron on which both units under study would converge, and which would then show an enhanced specificity in their response to a stimulus ensemble. It was found that in 20 pairs (21%) the logical AND operation was more selective than each of the component neurons. The largest time window for which the selectivity was found was evenly distributed over the values 8 ms, 32 ms and 128 ms, in one case selectivity was found only for a window of 2 ms. There was neither preference for selective pairs to be found for recordings with one electrode (45 cases) or dual electrodes (51), nor for independent (62) versus functionally connected (34) pairs. In some cases selectivity resulted in a preference for one specific call, in other cases it resulted in a loss of responsiveness to the masking noise effectively resulting in an enhanced signal-to-noise ratio. The analysis stresses the importance of spatiotemporal patterns of nervous activity for the representation of sounds in the auditory midbrain of anurans.

Animals↗

PubMed2004

Testosterone and chemosensory detection in male Syrian hamster.

Gonadal steroids stimulate both sexual motivation and performance. However, steroid facilitation of appetitive sexual behavior is poorly understood. The present study determined if castration impairs chemosensory detection in male hamsters. Chemosensory cues are the principal sensory modality to initiate mating in this species. We compared LiCl-induced conditioned taste avoidance to female hamster vaginal secretion (FHVS) in gonad-intact and castrated males. Following overnight water deprivation, males received FHVS for 15 min, followed by LiCl (2 ml of 0.15 M) or saline ip. The next day, fluid consumption in a two-bottle choice test was recorded for 5.5 h. Pairings were repeated 4x. Initially, discrimination of FHVS from estrous females (10 or 100 microg/ml) was compared with plain water. Subsequently, we determined if males could distinguish FHVS from Syrian vs. Djungarian females or from estrous vs. anestrous females. When 100 microg/ml FHVS was paired with saline, all gonad-intact and 86% of castrated males preferred FHVS over water. However, when 100 microg/ml FHVS was paired with LiCl, the preference was reversed: 12.5% of intact males and 25% of castrates preferred FHVS (P < 0.05 vs. saline pairing). When exposed to 10 microg/ml FHVS, neither gonad-intact nor castrated males expressed conditioned taste avoidance, suggesting that 10 microg/ml FHVS is below the threshold for detection. Comparing discrimination of FHVS from Syrian and Djungarian females, only castrated males developed a significant conditioned taste avoidance to Syrian FHVS paired with LiCl. While 71% of castrated males preferred Syrian FHVS after saline pairing, only 12.5% of castrates preferred Syrian FHVS after pairing with LiCl (P < 0.05). In gonad-intact males, 57% preferred Syrian FHVS after saline pairing, while 14% preferred Syrian FHVS following LiCl pairing (P > 0.05). Neither gonad-intact nor castrated males successfully discriminated between FHVS from estrous and anestrous females. These data demonstrate that castrated males perform as well as gonad-intact males in a test of LiCl-induced conditioned taste avoidance. Therefore, it is unlikely that steroids enhance detection of sexually relevant chemosensory cues.

Animals↗

PubMed1998

Sexual conflict and speciation.

We review the significance of two forms of sexual conflict (different evolutionary interests of the two sexes) for genetic differentiation of populations and the evolution of reproductive isolation. Conflicting selection on the alleles at a single locus can occur in males and females if the sexes have different optima for a trait, and there are pleiotropic genetic correlations between the sexes for it. There will then be selection for sex limitation and hence sexual dimorphism. This sex limitation could break down in hybrids and reduce their fitness. Pleiotropic genetic correlations between the sexes could also affect the likelihood of mating in interpopulation encounters. Conflict can also occur between (sex-limited) loci that determine behaviour in males and those that determine behaviour in females. Reproductive isolation may occur by rapid coevolution of male trait and female mating preference. This would tend to generate assortative mating on secondary contact, hence promoting speciation. Sexual conflict resulting from sensory exploitation, polyspermy and the cost of mating could result in high levels of interpopulation mating. If females evolve resistance to make pre- and postmating manipulation, males from one population could be more successful with females from the other, because females would have evolved resistance to their own (but not to the allopatric) males. Between-locus sexual conflict could also occur as a result of conflict between males and females of different populations over the production of unfit hybrids. We develop models which show that females are in general selected to resist such matings and males to persist, and this could have a bearing on both the initial level of interpopulation matings and the likelihood that reinforcement will occur. In effect, selection on males usually acts to promote gene flow and to restrict premating isolation, whereas selection on females usually acts in the reverse direction. We review theoretical models relevant to resolution of this conflict. The winning role depends on a balance between the 'value of winning' and 'power' (relating to contest or armament costs): the winning role is likely to correlate with high value of winning and low costs. Sperm-ovum (or sperm-female tract) conflicts (and their plant parallels) are likely to obey the same principles. Males may typically have higher values of winning, but it is difficult to quantify 'power', and females may often be able to resist mating more cheaply than males can force it. We tentatively predict that sexual conflict will typically result in a higher rate of speciation in 'female-win' clades, that females will be responsible for premating isolation through reinforcement, and that 'female-win' populations will be less genetically diverse.

Alleles↗

PubMed1999

Developmental exposure of rats to a reconstituted PCB mixture or aroclor 1254: effects on organ weights, aromatase activity, sex hormone levels, and sweet preference behavior.

Polychlorinated biphenyls (PCBs) are lipophilic industrial chemicals which are regularly detected in human breast milk, serum, and tissues. They possess hormone-modulating properties, and, when transferred transplacentally to the developing fetus, PCBs have been shown to induce persistent sex-specific neurobehavioral deficits. Interactions of PCBs with sex steroid-modulated neural differentiation could in part account for such effects. To test this hypothesis, female Long-Evans rats were exposed via food containing 40 mg/kg of either a reconstituted PCB mixture (RM), composed according to the congener-pattern in human breast milk, or the technical PCB mixture Aroclor 1254 (A1254). The exposure period started 50 days prior to mating and was terminated at birth (postnatal day 0: PND 0). Aromatase (CYP 19) activity was determined in hypothalamus/preoptic area (HPOA) brain-sections from newborn male pups. This enzyme converts testosterone (T) to 17beta-estradiol (E(2)) and plays a key role in sexual brain differentiation. Moreover, serum concentrations of T and E(2), physical development, organ weights, exposure levels, and sex-specific behavior were evaluated at different life stages. On PND 0, a reduced aromatase activity was detected in the HPOA of male RM-pups compared to controls. Female RM-weanlings exhibited significantly elevated uterine wet weights on PND 21, which is a marker for estrogenic activity. In the adult stage (PND 170), male offspring with maternal exposure to either PCB mixture showed markedly reduced testes weights and serum testosterone levels, thus demonstrating persistent antiandrogenic effects. On PND 180, male RM-rats exhibited a behavioral feminization in a sweet preference test, suggesting long-lasting changes in neuronal brain organization caused by the perinatally suppressed aromatase activity. The results suggest that maternal exposure to the RM, the pattern of which is similar to the PCB spectrum in human milk, results in more distinct effects on sex steroid-dependent processes and behavior than the technical PCB mixture A1254. PCB levels in brain and adipose tissue of the exposed offspring lay within 1-2 orders of magnitude above background concentrations in humans.

Aging↗

PubMed2001

"Electronic nose" detects major histocompatibility complex-dependent prerenal and postrenal odor components.

Mice prefer to mate with individuals expressing different MHC genes from their own. Volatile components presenting MHC-dependent odor types are present in urine and can be detected by mice, as shown by extensive behavioral studies. Similar odor types are suspected to influence human behavior as well. Although a recent report indicates that MHC expression influences the ratio of volatile compounds such as phenylacetic acid, so far no other means than studying the behavior of mice or rats has been available to assess odor types. Here, we report the ability of a gas sensor array (referred to as "electronic nose") to detect MHC-dependent odor types. The electronic nose consists of an array of chemophysical detectors, in our case quartz crystal microbalances and semiconducting metal-oxide sensors that change frequency or conductivity upon binding of very small numbers of individual molecules present in the gas phase of odorous fluids. The pattern of changes is characteristic for a particular smell. Our electronic nose distinguishes the urine odor types of MHC congenic mouse strains, MHC class I mutant mice, and HLA-A2 transgenic mice. In addition, MHC-dependent odor types can be detected in serum. The device also clearly differentiates between individual odor types of human sera from HLA homozygous individuals; however, HLA expression seems to have only a secondary influence. Thus, odor-type research can now be carried out with an objective and fast through-put system independent of behavioral studies.

Animals↗

PubMed1993

Conspecificity of the ticks Ixodes scapularis and I. dammini (Acari: Ixodidae).

Reciprocal crosses between Ixodes dammini Spielman, Clifford, Piesman & Corwin from Massachusetts and Ixodes scapularis Say from Georgia produced offspring through the F3 generation when the experiment was discontinued. Reciprocal I. dammini x Ixodes pacificus Cooley & Kohls (California) and I. scapularis x I. pacificus crosses produced F1 progeny; however, all progeny were sterile. Assortative mating experiments between I. dammini and I. scapularis indicated that males and females of both species mated with the opposite sex of heterospecific or conspecific ticks when there was a choice. Conventional discriminant analysis of morphometric measurements of ticks from Georgia, North Carolina, Maryland, Massachusetts, and two populations of F1 hybrids indicated that there were recognizable differences. However, size-free (sheared) discriminant analysis indicated that these differences were largely size-dependent, with much overlap of the four eastern and two hybrid populations but no overlap with I. pacificus from California. Analysis of chromosomes (morphology and C band) indicated no differences between the Georgia and Massachusetts populations but showed a difference between them and the California population of I. pacificus. Analysis of isozymes showed that the genetic identity value for the Georgia and Massachusetts populations was within the normal range for conspecific populations, whereas the California population indicated congeneric but not conspecific relatedness to the Georgia and Massachusetts populations. Life cycle data collected under similar laboratory conditions showed no differences in length of feeding and molting periods among Georgia, Massachusetts, and California populations. These data and results of the work of other authors on tick host preferences and vector competence indicate that I. dammini is not a valid species separate from I. scapularis. Because the name Ixodes scapularis Say, 1821, has priority over the name Ixodes dammini Spielman, Clifford, Piesman & Corwin, 1979, I. dammini is relegated to a junior subjective synonym of I. scapularis (based on Article 23 of the International Code of Zoological Nomenclature).

Animals↗

PubMed1991

The maternally expressed Drosophila gene encoding the chromatin-binding protein BJ1 is a homolog of the vertebrate gene Regulator of Chromatin Condensation, RCC1.

Using monoclonal antibodies I have identified a nuclear protein of Drosophila, BJ1 (Mr approximately 68 kd), and isolated its gene. Biochemical analysis demonstrates that the BJ1 protein is associated with nucleosomes and is released from chromatin by agents which intercalate into DNA, as previously shown for the high mobility group proteins (HMGs). On polytene chromosomes the protein is localized in all bands, with no preference for particular loci. Both the BJ1 protein and in particular the BJ1 mRNA are strongly expressed maternally. In early embryos all nuclei contain equal amounts of BJ1. During neuroblast formation, BJ1 mRNA becomes restricted to cells of the central nervous system, and higher protein levels are found in the nuclei of this tissue. In late embryonic stages, the mRNA almost completely disappears, but significant amounts of BJ1 protein persist until morphogenesis. The BJ1 gene encodes a 547 amino acid polypeptide featuring two different types of internal repeats. The sequence from amino acids 46 to 417 containing seven repeats of the first type has been highly conserved in evolution. 45% of the amino acids in this region are conserved in seven similar tandem repeats of the human gene Regulator of Chromatin Condensation, RCC1. The phenotype of a cell line carrying a mutation of RCC1 suggested a main function for this gene in cell cycle control. A yeast gene, SRM1/PRP20, also contains these repeats and shows 30% amino acid identity to BJ1 in this region. Mutations in this gene perturb mRNA metabolism, disrupt nuclear structure and alter the signal transduction pathway for the mating pheromone. Complementation experiments argue for a common function of these genes in the different species. I propose that their gene products bind to the chromatin to establish or maintain a proper higher order structure as a prerequisite for a regulated gene expression. Disruption of this structure could cause both mis-expression and default repression of genes, which might explain the pleiotropic phenotypes of the mutants.

Amino Acid Sequence↗

PubMed1993

Impact of DNA nucleotide excision repair on methyl methanesulfonate-induced mutations in Drosophila melanogaster.

To study the impact of DNA nucleotide excision repair (NER) on the spectrum of mutations induced by alkylating agents, postmeiotic male germ cell stages of Drosophila melanogaster were exposed to methyl methanesulfonate (MMS) and the males then mated with nucleotide excision repair deficient (exr-; mus(2)201) females. MMS (s value = 0.86) has a strong preference for alkylating the nitrogen positions in DNA, whereas < 1% of all DNA lesions are on oxygen. For genetic and molecular analysis of the types of mutations induced by MMS the vermilion locus was used as target gene. Mutation induction by MMS was increased 10-fold under the exr- conditions compared to a normal functioning repair system. The genetic analysis showed that < 15% of the mutants represented inter-locus mutations, which were classified as multi-locus deletions. Of the intra-locus mutations (18 F1 and 8 F2 mutants) 78% were transversions with a clear dominance of AT-->TA (11 in the F1, 3 in the F2) and few GC-->TA (2 in the F1, 3 in the F2) type of transversions. In comparison to the MMS spectrum produced under repair proficient (exr+) condition (Nivard, M.J.M., Pastink, A. and Vogel, E.W., 1992), the exr- spectrum shows a significant decrease in the percentage of deletions and a relative increase in transversions. These data are consistent with previously published papers suggesting that under normal repair conditions the nitrogen DNA adducts are efficiently repaired in Drosophila and that the hypermutability of MMS in the exr- strain is caused by an increased formation of apurinic sites either formed from 3-methyladenine or 7-methylguanine. This suggests that also in Drosophila 'the A-rule' is valid, indicating that during DNA replication an adenine (A) is preferentially incorporated opposite to non-instructive apurinic sites.

Animals↗

PubMed2005

Genetic quality and sexual selection: an integrated framework for good genes and compatible genes.

Why are females so choosy when it comes to mating? This question has puzzled and marveled evolutionary and behavioral ecologists for decades. In mating systems in which males provide direct benefits to the female or her offspring, such as food or shelter, the answer seems straightforward--females should prefer to mate with males that are able to provide more resources. The answer is less clear in other mating systems in which males provide no resources (other than sperm) to females. Theoretical models that account for the evolution of mate choice in such nonresource-based mating systems require that females obtain a genetic benefit through increased offspring fitness from their choice. Empirical studies of nonresource-based mating systems that are characterized by strong female choice for males with elaborate sexual traits (like the large tail of peacocks) suggest that additive genetic benefits can explain only a small percentage of the variation in fitness. Other research on genetic benefits has examined nonadditive effects as another source of genetic variation in fitness and a potential benefit to female mate choice. In this paper, we review the sexual selection literature on genetic quality to address five objectives. First, we attempt to provide an integrated framework for discussing genetic quality. We propose that the term 'good gene' be used exclusively to refer to additive genetic variation in fitness, 'compatible gene' be used to refer to nonadditive genetic variation in fitness, and 'genetic quality' be defined as the sum of the two effects. Second, we review empirical approaches used to calculate the effect size of genetic quality and discuss these approaches in the context of measuring benefits from good genes, compatible genes and both types of genes. Third, we discuss biological mechanisms for acquiring and promoting offspring genetic quality and categorize these into three stages during breeding: (i) precopulatory (mate choice); (ii) postcopulatory, prefertilization (sperm utilization); and (iii) postcopulatory, postfertilization (differential investment). Fourth, we present a verbal model of the effect of good genes sexual selection and compatible genes sexual selection on population genetic variation in fitness, and discuss the potential trade-offs that might exist between mate choice for good genes and mate choice for compatible genes. Fifth, we discuss some future directions for research on genetic quality and sexual selection.

Animals↗

PubMed2003

Sexual selection in female perceptual space: how female túngara frogs perceive and respond to complex population variation in acoustic mating signals.

Female preferences for male mating signals are often evaluated on single parameters in isolation or small suites of characters. Most signals, however, are composites of many individual parameters. In this study we quantified multivariate traits in the advertisement call of the túngara frog, Physalaemus pustulosus. We represented the calls in multidimensional scaling space and chose nine test calls to represent the range of population variation. We then tested females for phonotactic preference between calls in each pair of the nine test calls. We used statistics developed for paired comparisons in such "round robin" competitions to evaluate the null hypothesis of equal attractiveness, and to examine the degree to which females responded to calls as being different from or similar to one another in attractiveness. We then examined the attractiveness of each test call relative to all other test calls as a function of their location in multivariate acoustic space (the acoustic landscape) to visualize sexual selection on calls. Finally, we used methods from cognitive psychology to illustrate the females' perception of call attractiveness in multivariate space, and compared this perceptual landscape to the acoustic landscape of quantitative call variation. We show that correlations between individual call characters are not strong and thus there are few biomechanical constraints on their independent evolution. Most call variables differed among males, and there was high repeatability of call characters within males. Females often discriminated between pairs of calls from the population, and there were significant differences among calls in their attractiveness. Female preferences for calls were not stabilizing. The region of the acoustic landscape that was most attractive to females included the mean call but was not centered around it. The females' perceptual or preference landscape did not correlate with the call's acoustic landscape, and female perception of calls decreased rather than enhanced call differences.

Animal Communication↗

PubMed2003

Female sex pheromone-mediated effects on behavior and consequences of male competition in the shore crab (Carcinus maenas).

Exposure to receptive female pheromone elicits guarding behavior in shore crab males (Carcinus maenas), but little is known about the effects of sex pheromone on male competition or if the female plays an active role in mate choice. This study examined whether female pheromone enhanced agonistic behavior between males and what effects visual and chemical cues had on the rules and costs of such contests. We also investigated whether females exhibit a preference for males in terms of size. Under laboratory conditions, solitary male shore crabs engaged males who already had possession of a female. The visual and chemical presence of a receptive female had an impact on contest rules and costs. Fights were costly in terms of duration and of sustaining injury with either one or both crabs incurring injury in 40% of fights. To investigate the metabolic consequences of fighting over a perceived sexual resource (chemical cue only), fights were staged between pairs of size-matched males in the presence of water containing the female sex pheromone, water in which males had been kept, and untreated seawater. The duration and intensity of contests were greater when staged in the presence of the female pheromone compared with the two other treatments. Crabs that fought in the presence of female sex pheromone also had a greater accumulation of L-lactate and a reduction of glycogen stores. Fights were less costly in terms of injury with a single chemical cue compared with enhanced costs with a multiple sexual cue. The importance of female choice was determined by presenting postmolt females with different sized males. Males were kept in a fixed position, and the majority of females approached and performed courtship behavior to the largest males, demonstrating that females may be selective in terms of size.

Aggression↗

PubMed2005

Inheritance of song and stridulatory peg number divergence between Chorthippus brunneus and C. jacobsi, two naturally hybridizing grasshopper species (Orthoptera: Acrididae).

Knowledge of the genetic basis of divergence in mating signal characters that contribute to reproductive isolation is critical to understanding speciation. Here, we describe a semi-automated system for characterizing grasshopper acoustic signals. We used this system to study the genetic basis of divergence in three male calling song components [echeme (EL), syllable (SL) and phrase (PL) lengths] between Chorthippus brunneus and C. jacobsi, two species of grasshoppers that hybridize in northern Spain. We also studied the number of pegs in the stridulatory file. For all characters, additive effects accounted for most of the genetic differentiation between species. However, the three song components also showed small but significant epistatic effects. No sex linkage was detected. Wright-Castle-Lande estimates of the minimum numbers of genetic factors underlying song and peg number divergence were low: peg number (n(e)=5.87+/-5.84), SL (n(e)=2.37+/-4.79) and PL (n(e)=0.87+/-0.86). On the other hand, EL appeared to be controlled by many genes. These results suggest that divergence in SL and PL might be driven by sexual selection whereas EL might not be under selection. This is consistent with experimental results on female song preference in related species. However, the fact that few factors appear to underlie the differences in peg number is surprising. Peg number is not closely related to song characteristics. It often varies between closely related grasshopper species and it has been assumed to be a neutral character. The biometrical approaches used here tend to underestimate the number of factors influencing a trait but provide valuable background for subsequent quantitative trait loci analyses.

Animal Communication↗

PubMed1995

Altered sexual partner preference in male ferrets given excitotoxic lesions of the preoptic area/anterior hypothalamus.

Numerous experiments suggest that perinatal exposure of male vertebrates to testosterone (T), or its estrogenic metabolites, masculinizes aspects of coital function, including males' characteristic preference to seek out and mate with a female as opposed to another male conspecific. Other research has shown that this perinatal action of sex steroids also masculinizes aspects of neuronal morphology in the medial preoptic area/anterior hypothalamus (mPOA/AH). We asked whether neurons of the mPOA/AH contribute to males' preference to mate with a female. The ferret is an ideal species in which to ask this question. When tested in a T-maze after gonadectomy and treatment with estradiol benzoate (EB), female ferrets prefer to approach and receive neck grips from a stimulus male whereas males prefer to approach and neck grip an estrous female. In the minority of trials when EB-treated males approach a stimulus male, they occasionally receive a neck grip to which they display receptive postures as opposed to agonistic behaviors. In Experiment 1 castrated, EB-treated male ferrets which received bilateral infusions of the NMDA excitotoxin, quinolinic acid aimed at the dorsomedial POA/AH, preferred to approach a stimulus male significantly more often than groups of control males which either received a sham lesion, received a unilateral mPOA/AH lesion or in which bilateral infusions of quinolinic aci produced no histologically detectible excitotoxic damage to the mPOA/AH. Males with bilateral mPOA/AH lesions also displayed neck gripping on a significantly lower percentage of trials than control males when they approached the stimulus female. Ovariectomized, EB-treated female ferrets with bilateral mPOA/AH lesions, like control females, preferred to approach and receive neck grips from a stimulus male. The males used in Experiment 1 had never experienced circulating levels of T characteristic of the breeding season. Therefore, in Experiment 2 prepubertally gonadectomized males and females were treated chronically with a high dose of T propionate (TP) and tested several times with a receptive female prior to brain surgery. Males which received bilateral excitotoxic lesions of the mPOA/AH neck gripped and mounted stimulus females significantly less than control males. Again, when given EB followed by T-maze tests of partner preference, males with bilateral mPOA/AH lesions, like sham-operated female controls, preferred to approach the sexually active stimulus male significantly more often than control males, which preferred to approach the stimulus female. Our results suggest that neurons in the mPOA/AH play an important role in the integration of sensory cues which determine heterosexual partner preference in the male ferret, in addition to facilitating masculine coital performance.

Animals↗

PubMed2002

Developmental changes in responsiveness to parents and unfamiliar adults in a monogamous monkey (Callicebus moloch).

Titi monkeys (Callicebus moloch) are monogamous New World primates that are characteristically found in family-type groups consisting of a mated adult pair and one or two young. The factors maintaining the small size of these groups are not known. Based on observations of free-ranging and captive families, parental aggression toward older offspring seems unlikely to play a significant role. Maturing individuals themselves, however, could undergo behavioral changes that weaken ties to their natal group. These might include waning of affiliative relations with parents, or subtle forms of aversion. Independent of such changes, increasing interest in unfamiliar conspecifics could be a factor. We examined these possibilities in the present study by assessing changes in social behavior and social preferences from initial ambulatory independence (6 months) through reproductive maturity (24 months) in a combined cross-sectional/longitudinal study of 21 captive titi monkeys living with their parents. Responses to both parents and to an unfamiliar adult heterosexual pair, a single unfamiliar adult male, and a single unfamiliar adult female were observed when subjects were given a choice between parents and strangers presented simultaneously or as the only social incentive. Social stimuli were at opposite ends of a 16.8-m-long test corridor. Subjects could move freely about the corridor for 5 min with each configuration of social stimuli. They stayed closer to parents than to strangers at all ages. Responsiveness to strangers increased with age and suggested growing ambivalence, particularly toward the male stranger. As they approached 24 months of age, male subjects showed a dramatic increase in the frequency and intensity of agonistic behaviors toward male strangers, behaviors that were rarely directed toward female strangers or parents. Waning of attraction to parents may be less important in dispersal from the natal group than changing reactions to strangers.

Aggression↗

PubMed2006

Inheritance of olfactory preferences I. Pheromone-mediated behavioral responses of Heliothis subflexa x Heliothis virescens hybrid male moths.

Shifts in male preference for qualitatively different pheromone blends appear to have played a fundamental role in the divergence of olfactory communication and evolution of moth species. As an initial step in documenting the genetic complexity underlying such shifts, we characterized the behavioral responses of hybrid male moths created by mating two heliothine moth species, Heliothis subflexa and Heliothis virescens. Between 67 and 96% of hybrid males flew upwind and contacted the pheromone source when presented with a blend consisting of (Z)-11-hexadecenal (Z11-16:Ald), (Z)-9-hexadecenal (Z9-16:Ald), and (Z)-11-hexadecenol (Z11-16:OH) in a 1:0.5:0.1 ratio that has previously been shown to be attractive to H. subflexa males. In addition, an H. virescens blend of Z11-16:Ald and (Z)-9-tetradecenal (Z9-14:Ald) enhanced by the addition of Z11-16:OH (in a 1:0.05:0.1 mixture) was attractive to hybrid males (26-64% source contact), but significantly fewer males reached the odor source compared to the blend containing Z9-16:Ald. A blend in which the dosage of Z9-14:Ald was doubled, however, was equally attractive (75-77% source contact) as the Z9-16:Ald-containing blend. Consecutive presentation of two blends revealed that individual hybrid males responded equally well to blends containing either Z9-14:Ald or Z9-16:Ald. Together these results suggest that in addition to Z11-16:Ald, hybrid males: (1) required either Z9-16:Ald (likeH. subflexamales) or Z9-14:Ald (like H. virescens males); (2) required the presence of Z11-16:OH (H. subflexa dominant); (3) were not adversely affected by the presence of Z11-16:Ac (H. subflexa dominant). The behavioral response phenotype of hybrid males was therefore influenced by genetic factors inherited from both parental species.

Animal Communication↗