Stifled sex in sympatry: patterns of sexual incompatibility among desmognathine salamanders

Sexual incompatibility due to differences in mate-recognition systems can be an important factor in preventing hybridization and gene flow between animal populations in sympatry. We tested in the laboratory for sexual incompatibility between populations of two species of desmognathine salamanders that occur in sympatry in south-eastern Kentucky, North America, Desmognathus monticola and D. welteri (Caudata: Plethodontidae: Desmognathinae). Spermatophore deposition and insemination (two related measures of sexual success) were frequent in intraspecific encounters, but interspecific encounters never resulted in the deposition of spermatophores by males (Experiment 1). The sexual behaviour patterns of these two species are similar qualitatively, but all encounters staged between them failed to progress beyond the most preliminary of courtship interactions (Experiment 2), perhaps due to species differences in chemosensory communication. Our data on sexual incompatibility between D. monticola and D. welteri are similar to those available for other desmognathine taxa that occur in sympatry. Review of a broader data-set on patterns of sexual incompatibility both within and between species, and in allopatry and in sympatry, provides evidence for both divergence of mate-recognition systems in allopatry and enhancement of sexual incompatibility in sympatry for desmognathine salamanders. We hypothesize that diversification in allopatry may be a consequence of natural and/or sexual selection acting to promote sexual success within populations. Enhancement in sympatry may be a consequence of subsequent selection for accurate species recognition under the threat of hybridization or gene flow between species.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 367–375.     

Male-female interactions and socio-sexual isolation of Mus spicilegus toward two other species of east-European mice, M. macedonicus and M. m. musculus.

Social and sexual interactions were analysed as potential behavioural processes assessing reproductive isolation between the mound-building mouse, Mus spicilegus, and two other wild species, M. macedonicus and M. musculus. Dyadic encounters among strange M. spicilegus individuals and between M. spicilegus and the two other species members were conducted with females in an oestrus state. In intraspecific M. spicilegus encounters, there was a high incidence of close contact behaviours initiated by the females. In interspecific encounters M. musculus males and females and M. macedonicus females showed social interest toward their M. spicilegus protagonists, whereas the later behaved in an unfriendly or aggressive manner. Thus socio-sexual interactions shown by the different species seem to be sufficient to prevent any attempt to mate interspecifically. Arguments in favour of recognition against reinforcement hypothesis are discussed.     

Phylogenetic relationships of African killifishes in the genera Aphyosemion and Fundulopanchax inferred from mitochondrial DNA sequences

We have analyzed the phylogenetic relationships of 52 species representing all defined species groups (J. J. Scheel, 1990, Atlas of Killifishes of the Old World, 448 pp.) of the African aplocheiloid fish genera Aphyosemion and Fundulopanchax in order to examine their interrelationships and to reveal trends of karyotypic evolution. The data set comprised 785 total nucleotides from the mitochondrial 12S rRNA and cytochrome b genes. The molecular-based topologies analyzed by both maximum parsimony and neighbor-joining support the monophyly of most previously defined species groups within these two killifish genera. The genus Aphyosemion is monophyletic except for the nested position of Fundulopanchax kunzi (batesi group; subgenus Raddaella) within this clade, suggesting that this taxon was improperly assigned to Fundulopanchax. The remaining Fundulopanchax species sampled were supported as being monophyletic in most analyses. Relationships among the species groups in both genera were not as strongly supported, suggesting that further data will be required to resolve these relationships. Additional sampling from the 16S rRNA gene allowed further resolution of relationships within Fundulopanchax, more specifically identifying the nonannual scheeli group as the basal lineage of this otherwise annual genus. Chromosomal evolution within Aphyosemion has been episodic, with the evolution of a reduced n = 9-10 metacentric complement having occurred in multiple, independent lineages. Polarity of chromosomal reductions within the elegans species group appears to support previous hypotheses concerning mechanisms of karyotypic change within the genus Aphyosemion.     

The behavior of the African killifish,Aphyosemion gardneri: normative studies

Synopsis The behaviors of maleAphyosemion gardneri observed during interactions with female and maleA. gardneri are described. First order transition matrices based on data collected during these interactions were used to construct behavioral flow diagrams. These flow diagrams show that sequences of sexual behaviors are less variable than sequences of aggressive behaviors. The position of acts in a typical sequence may be used in determining the level of activation of the behavioral system associated with those acts. Complexity and energy expenditure of behaviors tends to increase within sequences.     

A study of Aphyosemion schmitti (Romand, 1979) and a survey of the Aphyosemion of Liberia (Pisces, Cyprinodontidae)

Aphyosemion schmitti can be separated from neighbouring species on the basis of colour pattern, crossing experiments, cytogenetics, genetics and zoogeographical distribution. Three groups of Aphyosemion can be distinguished, based on morphological and meristic characters, colour patterns and geographical distribution; i.e. the liberiense group, the guineense group and the occidentalis group. A differentiation of the Liberian Aphyosemion is proposed, and its possible phylogenetic relationships are discussed.     

Same-sex sexual behavior in birds: expression is related to social mating system and state of development at hatching

We report the findings of a phylogenetic comparative analysisexamining patterns and frequency of occurrence of same-sex courtshipand mounting behavior in birds. Our analysis has shown associationsbetween same-sex sexual behavior and both mating system anddegree of precociousness at hatching. The patterns of expressionand frequency of occurrence of same-sex sexual behavior differedmarkedly for males and females. Patterns of same-sex sexualexpression reflected the competitive sexes that actively solicitsexual interactions in heterosexual encounters. Male–male(MM) sexual behavior occurred across all mating systems, butMM mounting was significantly more prevalent in those specieswith facultative polygamy. The frequency of MM sexual behaviorincreased with degree of polygamy. Female–female (FF)sexual behavior (especially courtship) occurred most frequentlyin socially monogamous species and rarely occurred in speciesthat display obligate polygamy (predominantly polygynous species).Both expression and frequency of FF sexual behavior was stronglyrelated to the precocial state of development at hatching. FFsexual behavior is more likely to occur in species in whichmonogamy occurs together with the production of precocial offspring;that is, in monogamous species that are exceptions to the morecommon altricial mode of development. We suggest that requirementof biparental care in monogamous species may influence the greaterexpression of FF sexual behavior and longer term associations.Both spatial and behavioral dispersion of females and engagementin uniparental care may be important in explaining the lowerincidence of FF sexual behavior in polygynous species. Socialcontexts where males congregate at communal leks or displayareas may influence the greater expression and frequency ofMM sexual behavior in polygynous species.     

Aggression in shorebirds in relation to flock density and composition

The aggressive interactions of Turnstones and Purple Sandpipers feeding in wintering mixed-species wader flocks could be classified into those involving food and those involving space. All observed interspecific encounters were of short duration and were initiated and won by the larger species; the majority did not involve food and were resolved by low-intensity displays. Intraspecific interactions (a greater proportion of which involved food) were also resolved quickly and were usually won by the initiator. Space-related encounters between conspecifics were more likely to be resolved than food-related encounters just by threat displays. Aggression rates increased with flock densities. However, the increase in aggression with density was dependent on the species composition of the flock: both Turnstones and Purple Sandpipers were more likely to be involved in fights (both over food and over space) with conspecifics than with other species, indicating that the aggression costs of flocking were less in mixed-species flocks.     

Intergroup interactions in Tibetan macaques at Mt. Emei,China

Data on intergroup-interactions (I-I) were collected in 5 seasonally provisioned groups (A, B, D, D₁, and E) of Tibetan macaques (Macaca Thibetana) at Mt. Emei in three 70-day periods between 1991 April–June (P1), September–November (P2), December–1992 February (P3). The I-I were categorized as forewarning made by high-ranking males (including Branch Shaking and/or Loud Calls), long-distance interactions in space (specified by changes in their foraging movements), and close encounters (with Affinitive Behavior, Male's Herding Female, Sexual Interaction, Severe Conflict, Adult Male-male Conflict, Opportunistic Advance and Retreat, etc. performed by different age-sex classes). From periods P1 to P3, the I-I rate decreased with reduction in population density as a positive correlate of food clumpedness or the number of potential feeders along a pedestrian trail. On the other hand, from the birth season (BS, represented by P1 and P3) to the mating season (MS, represented by P2) the dominance relation between groups, which produced a winner and a loser in the encounters, became obscure; the proportion of close encounters in the I-I increased; the asymmetry (local groups over intruders) of forewarning signals disappeared; the rate of branch shaking decreased; and sometimes intergroup cohesion appeared. Considering that sexual interactions also occurred between the encountering groups, above changes in intergroup behaviors may be explained with a model of the way in which the competition for food (exclusion) and the sexual attractiveness between opposite sexes were in a dynamic equilibrium among the groups, with the former outweighing the latter in the BS, and conversely in the MS. Females made 93% of severe conflicts, which occurred in 18% of close encounters. Groups fissioned in the recent past shared the same home range, and showed the highest hostility to each other by females. In conspicuous contrast with females' great interest in intergroup food/range competition, adult male-male conflicts that were normally without body contact occurred in 66% of close encounters; high-ranking male herding of females, which is typical in baboons, appeared in 83% of close encounters, and showed no changes with season and sexual weight-dimorphism; peripheral juvenile and subadult males were the main performers of the affinitive behaviors, opportunistic advance and retreat, and guarding at the border. In brief, all males appeared to “sit on the fence” at the border, likely holding out hope of gaining the favor of females both within and outside the group. Thus, females and males attempted to maximize reproductive values in different ways, just as expected by Darwin–Trivers' theory of sexual selection. In addition, group fission was observed in the largest and highest-ranking group for two times (both in the MS) when its size increased to a certain level, and the mother group kept their dominant position in size and rank among the groups that might encounter, suggesting that fission takes a way of discarding the “superfluous part” in order to balance the cost of competition for food and mates within a group, and the benefit of cooperation to access the resources for animals in the mother group. Am J Phys Anthropol 104:459–470, 1997. © 1997 Wiley-Liss, Inc.     

Convergence of life-history phenotypes in a Trinidadian killifish (Rivulus hartii)

Convergent evolution is characterized by the independent evolution of similar phenotypes within similar selective environments. Previous work on Trinidadian killifish, Rivulus hartii, demonstrated repeatable life-history differences across communities that differ in predation intensity. These studies were performed in rivers located on the south slope of Trinidad's Northern Range Mountains. There exists a parallel series of rivers on the north slope of these mountains. As on the south slope, Rivulus is found across a gradient of fish predation. However, the predatory fish species in north-slope rivers are derived from marine families, whereas south-slope rivers contain a predatory fish fauna characteristic of the South American mainland. If predator-induced mortality and the associated indirect effects are the causal factors selecting for life-history patterns in Rivulus, and these are similar in north- and south-slope rivers, then the specific predatory species should be interchangeable and we would expect convergence of life-history phenotypes across slopes. Here, we characterize the life-history phenotypes of Rivulus from north-slope communities by measuring number of eggs, egg weight, reproductive allotment, reproductive tissue weight, and size at maturity. We find similar patterns of life-history divergence across analogous predator communities. Between slopes, minor differences in Rivulus life-history traits exist and one potential cause of these differences is the abundance of Macrobrachium prawns in north-slope rivers.     

Increased Frequency of Intergroup Encounters in Wild Bonobos (<Emphasis Type="Italic">Pan paniscus</Emphasis>) Around the Yearly Peak in Fruit Abundance at Wamba

Intergroup interactions in primates vary from nonagonistic to severely aggressive. Food resources and fertile females cause intergroup aggression when groups defend resources and mates from other groups. Peaceful intermingling during intergroup encounters is rare but has been reported in several primates, including bonobos (Pan paniscus). Although intergroup encounters in bonobos occur at both nonprovisioned and provisioned sites, provisioning may be one factor responsible for frequent intergroup encounters. We studied intergroup encounters between one bonobo group (PE) and its neighboring groups, one semihabituated and two habituated groups, under nonprovisioned conditions in 2010–2015 at Wamba, Democratic Republic of Congo. We examined whether fruit abundance and females with sexual swellings influenced encounter frequency. PE group encountered the other groups on 7.1 days (mean, range: 0–19) per month. Up to four different groups met simultaneously at one location. Encounter frequency was highest around the yearly peak in fruit abundance, suggesting that reduced food competition is linked to increased encounter frequency. During periods of relatively low fruit abundance, the probability of an encounter was higher when a higher number of adult females with maximum sexual swellings were present, suggesting that the attractiveness of females with sexual swellings promoted group encounters during periods of relatively low fruit abundance. These findings suggest that both competition for food and the availability of females with sexual swellings influence encounter frequency in bonobos.     

Mitochondrial DNA phylogeny of West African aplocheiloid killifishes (Cyprinodontiformes, Aplocheilidae)

African killifishes (Cyprinodontiformes, Aplocheilidae) historically associated with the genus Aphyosemion occur in two geographically distinct regions. One assemblage from far West Africa has been previously shown to be monophyletic and not closely related to the remaining eastern species of Aphyosemion (W. J. Murphy and G. E. Collier, 1997, Mol. Biol. Evol. 14, 790-799). This is supported by further analysis of mitochondrial DNA sequences from 19 species from 21 different localities, representing 19 of the putative 22 species of this western group. Phylogenetic analyses of these data corroborate the monophyly and sister-group relationship of two distinct groups of taxa: Callopanchax and Scriptaphyosemion. Many of the relationships within Scriptaphyosemion suggest that these taxa may have radiated within a short period of time relative to the rate of substitutions within these sequences. A third, and possibly paraphyletic group of species, Archiaphyosemion, is suggested to be the sister taxon to the first two groups. These three groups are elevated to generic rank and together represent the sister group to the genus Epiplatys. Biogeographic inference suggests that the ancestors of this group diversified westward through upland habitat and have only relatively recently entered the lowland habitats in which Scriptaphyosemion and Callopanchax have diversified, with the latter genus reacquiring a suite of traits collectively referred to as annualism.     

Vocal Signalling of the Great Crested Flycatcher,Myiarchus crinitus (Aves,Tyrannidae)

The singing and related vocalizing of great crested flycatchers, Myiarchus crinitus (Aves, Tyrannidae), included at least 12 different vocalizations. Each vocalization correlated with (and thus made information available about) a distinctive range of behaviour, from unassertive to more actively responsive, provocative or even confrontational. Four were used by individuals primarily when alone and not initiating close social encounters. The eight other vocalizations were uttered primarily in close encounters: one in preliminaries to such events, two predominantly in encounters with opponents, another in close associating of mates, two in duetting, and two infrequently, mostly in confrontations. The division of the repertoire into sets of vocalizations providing information about either low or elevated probabilities that a signaller will undertake the behavioural initiatives that precede, shape or sustain social interactions parallels a division found in other recently studied passerines. Such information is pertinent to individuals' decisions to forego or start close interactions with, for instance, competitors or mates. The information should be useful to a great many species, not just birds, but also mammals and various other animals — species in which individuals keep each other informed by singing when they are apart.     

Reactions of adult and immature squirrel monkeys to intergroup exposure

Initial encounters between unfamiliar animals raise the practical problem of controlling aggression and provide the opportunity to examine changes in social structure that may occur as groups merge. Social interactions and spatial grouping patterns were examined in newly formed squirrel monkey groups, in which a subgroup of familiar adults was introduced to a subgroup of familiar immature squirrel monkeys. Yearlings (10–11 months) and subadults (20–50 months) generally remained spatially distinct from adults, and intergroup interactions often consisted of adult-initiated antagonism. Adults exhibited sexual segregation in their spatial grouping patterns and interactions, whereas yearlings and subadults generally showed sexual integration. These data suggest that there is considerable adult resistance to integration of unfamiliar immatures into established adult social groups. Zoo Biol 17:519–524, 1998. © 1998 Wiley-Liss, Inc.     

Increased sexual activity during the midcycle portion of the human menstrual cycle

Daily sexual activity of sexually active lesbian couples was recorded over a 14-week period. Significant peaks in sexual encounters and orgasms were found during the midcycle portion of the menstrual cycle. These results demonstrate a pattern of increased midcycle sexual activity independent of interactions with males, type of contraceptive method, or fear of pregnancy.     

Coral reef fish assemblages: intra- and interspecific competition for shelter sites

Synopsis Observations were made on intra- and interspecific aggressive interactions among the fishes living in the rubble/sand coral reef habitat in St. Croix, U. S. Virgin Islands. Four species (beaugregory — Stegastes leucostictus; ocean surgeonfish — Acanthurus bahianus; doctor fish — A. chirurgus; common squirrelfish — Holocentrus rufus) which sheltered in holes on the reef all actively defended one to several shelter sites at dusk. Short-term shelter side fidelity was observed in three of these four species. Agonistic interactions over both food and shelter occurred during the daytime but much less frequently than agonistic interactions over shelter at dusk. Dominance in intraspecific aggression was determined almost completely by the relative sizes of the individuals involved, with the larger individuals dominating in 95–98% of all encounters. A similar, but less strong, relationship between size and dominance existed for interactions between closely related species. For aggressive encounters between unrelated species, however, both relative sizes and species identity determined the outcome. Species, both diurnal and nocturnal, which strongly defend several shelter sites may have a strong and disproportionate impact on the sheltering behavior of other fishes. Intraspecific and interspecific defense of shelter sites may determine the patterns of mortality that result from predation, thereby influencing population abundances and assemblage composition.     

Aspects of sound communication in the pearlfish Carapus boraborensis and Carapus homei (Carapidae)

Several species of Carapidae are known to have symbiotic relationships with marine invertebrates. The two most common species in Moorea (French Polynesia), Carapus boraborensis and Carapus homei, undergo conspecific and heterospecific encounters in the same holothurian host during which they produce sounds. Another characteristic of these fish lies in their abilities to produce sounds. The objective of this study was dual: (1) to seek if there was a sexual difference in the sounds produced by C. boraborensis; (2) to seek if there was a difference in the sound emissions between heterospecific and conspecific encounters. In each trial, sounds were only recorded when one individual entered the sea cucumber that was already occupied. In encounters, sounds were structured in regular pulse emissions whose pulse lengths and periods allowed to significantly distinguish each species, as well as both sexes in C. boraborensis. In the latter species, results show for the first time that temporal features of the emitted sounds can have a functional importance in sex identification. In heterospecific encounters, sounds were reduced 68% of the time to a single pulse emission and there was a modification in the pulse length of each species: it shortens in C. homei and it lengthens in C. boraborensis. It highlights that both carapids are able to adapt their sounds to the facing species. Because a modification of the sound appears to be done at the first emission, it is supposed that recognition precedes the sound emission.     

Sexual Interference in the Sword-tailed Newt,Cynops ensicauda popei (Amphibia: Salamandridae)

This paper describes competitive interaction between males of the salamandrid Cynops ensicauda popei. The sexual behaviour of the male is influenced by the presence of a second, rival, male. Competition for access to the female and other male interactions continuously interrupt ongoing courtships. Spermatophore pick-up success is lower than in encounters involving single pairs. During triad encounters, fewer spermatophores were deposited than in dyad encounters, due to interference during the creep stage of courtship. Two basic forms of male sexual interference were distinguished: ‘lure away’ during the creeping stage, from a position that is different from the direction of creep; and ‘female mimicry’, during which the male presses his snout alternately against the courting male's tail and the female's snout. In both forms, a rival male may shove one of the courting individuals away. The repertoire of sexual behaviour patterns of Cynops ensicauda popei appears to be less complex and varied than that of most Triturus species. The courtship of Cynops places less emphasis on display behaviour with tail and body, and a stronger emphasis on the creeping stage, where the male carefully leads the responsive female over a series of spermatophores, but during which rival males may interfere in a variety of ways.     

Migration strategy and divergent sexual selection on bird song

Migratory birds are assumed to be under stronger sexual selection pressure than sedentary populations, and the fact that their song is more complex has been taken as confirmation of this fact. However, this assumes that sexual selection pressure due to both male competition and female choice increase together. A further issue is that, in many species, songs become less complex during competitive encounters; in contrast, female choice selects for more complex song, so the two selection pressures may drive song evolution in different directions. We analysed song in two sedentary and two migratory populations of blackcaps (Sylvia atricapilla), a species in which different song parts are directed to males and females. We found that migratory populations produce longer, female-directed warbles, indicating sexual selection through female choice is the strongest in these populations. However, the part of the song directed towards males is shorter and more repetitive (as observed in individual competitive encounters between males) in non-migratory populations, indicating sedentary populations, are under stronger selection due to male competition. We show for the first time that the intensity of selection pressure from male competition and female choice varies independently between populations with different migratory behaviours. Rapid alterations in the migration patterns of species are thus likely to lead to unexpected consequences for the costs and benefits of sexual signals.     

Human Interactions with Free-Ranging and Captive Bottlenose Dolphins

ABSTRACT

The popular demand for encounters with dolphins has resulted in organized encounters around the world involving in-water interactions with both captive and free-ranging dolphins. Many concerns about these interactions have been raised with regard to the well-being of human and dolphin participants (e.g. Capaldo 1989; Iannuzzi and Rowan 1991). In this paper we (a) review existing information on human/dolphin interactions, (b) provide a qualitative comparison of such interactions in the captive and in the wild with the same species of dolphin (Tursiops truncatus), and (c) make suggestions regarding future research needs regarding the wellbeing of dolphins and humans in interactive programs.

This study found that the free-ranging dolphin/human interactions consisted primarily of basic elements of intraspecific interactions among free-ranging dolphins. Interactive dolphin behaviors in the captive environment consisted primarily of actions that had been signaled and then reinforced by humans. Potential indicators of disturbance in the dolphins were observed in both contexts, but most frequently in the captive environment. We conclude that future research is needed to assess the risks to human and dolphin participants during in-water encounters.     

Reproductive interference in two ground-hopper species: testing hypotheses of coexistence in the field

Similar to resource competition, reproductive interference may hamper the coexistence of closely related species. Species that utilize similar signal channels during mate finding may face substantial fitness costs when they come into contact and demographic displacement of the inferior species (sexual exclusion) is a likely outcome of such interactions. The two ground‐hopper species Tetrix ceperoi and Tetrix subulata broadly overlap in their ranges and general habitat requirements, but rarely co‐occur on a local scale. Results from laboratory and field experiments suggest that this mosaic pattern of sympatry might be influenced by reproductive interference. Here, we examine the significance of sexual interactions for these species in the field and test hypotheses on mechanisms of coexistence. Our results show that heterospecific sexual interactions also occur under field conditions, but in contrast to the experiments T. ceperoi was not the inferior species. The number of male mating attempts of both species was strongly correlated with encounter frequencies. Males discriminated between the sexes but not between the species, suggesting an incomplete mate recognition system in both species. The analysis of microhabitat preferences and spatial distribution revealed that habitat partitioning is not a suitable mechanism of coexistence in this system. Instead, the costs of reproductive interference are substantially mitigated by different niche breadths leading to different degrees of aggregation. Despite a considerable niche overlap T. ceperoi displayed a stronger preference for bare ground and occurred more aggregated than T. subulata, which had a broader niche. These differences may reduce the frequencies of heterospecific encounters and interactions in the field. Our results demonstrate that coexistence in the presence of reproductive interference is comparable to resource competition, being strongly influenced by ecological traits of the involved species, such as niche breadth and dispersion pattern.