Differences In Mating Systems Research Articles

Construction of a genetic linkage map in the wild plantMimulususing RAPD and isozyme markers

As a first step to mapping quantitative trait loci for mating system differences, a genetic linkage map was generated from an interspecific backcross between Mimulus guttatus and Mimulus platycalyx. The linkage map consists of 99 RAPD and two isozyme markers. Eighty-one of these markers were mapped to 15 linkage groups, spanning 1437 contiguous centiMorgans, and covering 58% of the estimated genome. The genome length of Mimulus is estimated at 2474 +/- 35 cM; bootstrapping indicates that only ca. 40 markers are needed to give an accurate estimate of genome length. Further statistical analyses indicate that many RAPD markers cannot be ordered with certainty and that uncertain linkage groups tend to map nonlinearly even under commonly used mapping functions. Strategies for speeding up the mapping process for a wild species and possible applications of a partial linkage map in evolutionary studies are discussed. Key words : linkage map, mating system, Mimulus, RAPD.

Intrasexual selection and phylogenetic constraints in the evolution of sexual canine dimorphism in strepsirhine primates

AbstractThe goals of this study were to analyze the origin and function of sex differences in the size of canine teeth among Malagasy lemurs and other strepsirhine primates. These analyses allowed me to illuminate interactions between different mechanisms of sexual selection and to elucidate constraints on this sexually‐selected trait. In contrast to central predictions of sexual selection theory, polygynous lemurs lack both sexual dimorphism in body size and male social dominance, but the degree of sexual dimorphism in the size of their canines is not known. A comparison of male and female canine size in 31 species of lemurs and lorises revealed significant male‐biased canine dimorphism in only 6 of 13 polygynous lemur species. This result is in contrast to predictions of a hypothesis that would explain the lack of size dimorphism in lemurs as a result of high viability costs because canine teeth presumably have low maintenance costs and because they are used as weapons in male‐male combat. Moreover, because females had significantly larger maxillary canines than males in only one lemur species, female dominance is not generally based on female physical superiority and selective forces favoring female dominance do not constrain sexual canine dimorphism in the sense of a pleiotropic effect. Contrary to predictions of sexual selection theory, species differences in canine dimorphism across strepsirhines were neither associated with differences in mating system, nor with the potential frequency of aggression. Variation in canine dimorphism was also unrelated to differences in body size, but there were significant differences among families, pointing to strong phylogenetic constraints. This study demonstrated that polygynous lemurs are at most subject to weak intrasexual selection on dental traits used in male combat and that traits thought to be under intense sexual selection are strongly influenced by phylogenetic factors.

Habitat Fragmentation and Habitat Alterations: Principal Threats to Most Animal and Plant Species

Many human activities, such as deforestation, urbanization, intensive agriculture, the building of roads and railways all reduce natural habitats to remnants of different size. In addition to the overall decrease in the area available for the organisms, the fragmentation of habitats leads to a division of existing populations into isolated subpopulations of small size and changes in habitat characteristics in the fragments. It is generally assumed that habitat fragmentation contributes significantly to the local extinction of animal and plant species. Unfortunately, inventories of animal and plant species in “natural” fragments do not allow a discrimination between different factors that cause local population extinction. This article outlines a long-term field experiment in which calcareous grassland in the Swiss Jura mountains is artificially fragmented into patches of different size. The experiment allows the investigation of extinction and (re)colonization processes of selected species of plants and animals in the newly-created fragments with respect to demographic traits, population sizes, levels of genetic variation and differences in mating systems.

A model of sympatric speciation by sexual selection

Quantitative genetic models have indicated that sexual selection may lead to speciation in isolated populations or to exaggeration of differences in male traits along a cline. We argue that where female mate preference and opposing natural selection against conspicuous males have produced a stable equilibrium in male trait genotype, a reversed female mate preference may invade the population, initially assisted by reduced male mortality. The consequent linkage disequilibrium may lead to rapid sympatric speciation. Assuming a four-locus quantitative male trait and single-locus female preference rule and overlapping generations, we present a simulation model which indicates that reversal of female mate preference in a single individual can lead rapidly to full reproductive isolation in a small population. Speciation may be produced by the proposed mechanism in allopatry, parapatry or full sympatry. We suggest that differences in mating system and its genetic bases may account for some of the differences in speciation rates among lineages.

The polygynandrous mating system of the alpine accentor, Prunella collaris. I. Ecological causes and reproductive conflicts

On the mountain tops of the French Pyrenees (1950–2410 m), alpine accentors bred in polygynandrous groups in which an alpha male, and from one to three unrelated and usually younger subordinate males, shared a large undefended range (mean 18 ha) within which from two to four unrelated females had overlapping ranges (mean 11 ha per female). Group size was not related to range size of males or females but was influenced by the temporal availability of fertile females; alpha males monopolized more mates when females were more asynchronous in their onset of breeding, which was related to age and habitat (snow melt). The diet, determined from prey remains in faeces, was mainly small invertebrates, particularly taxa that dominate the fallout fauna, swept up by the wind from the valleys below. The birds' unusually large ranges were necessary to exploit these prey, which sweep netting showed to be scarcer on the mountain tops than down by the tree line, and also more patchily distributed in space and time. Nestlings were fed either by the female alone or with the help of from one to three males. Male help varied depending on which males mated and on the activities of other females in the group (males preferred to compete for matings than to feed chicks). Chick mass increased with male help, but females could fledge all their young successfully with little or no help, even in severe weather. Sexual conflict is similar to that in dunnocks, Prunella modularis; females gain through increased male help by giving shared paternity to several males while alpha males do best by monopolizing all the matings. Differences in dunnock and alpine accentor mating systems are related to ecology, and it is suggested that the dunnock's variable mating system reflects its derivation from a mountain-living ancestor.

Food Quality Controls Sexual Selection in Mormon Crickets by Altering Male Mating Investment

Populations of several katydid species (Orthoptera: Tettigoniidae) show large differences in mating system; in some species males compete and females choose mates, whereas in others these courtship roles are reversed. Male katydids feed their mates during mating with a large, nutritious spermatophore. I hypothesized that courtship role reversal and increased sexual selection on females was a result of limitation in nutritious food items causing a decrease in the number of males available for mating (and thus in the spermatophore meals available). This hypothesis was tested by varying diet in field cages of Mormon crickets, Anabrus simplex. Results showed that, in contrast to a diet supplemented with proteinaceous food items, a poor diet resulted in: (1) a decrease in the number of sexually active males, (2) an increase in sexual selection for female body size, and (3) a reversal in the typical courtship roles. The experiment ruled out alternative explanations for variation in the mating system of this species,such as differences in population density and age. The conclusion from this study is that increased sexual selection on females due to such a change in diet is a result of an increase in the relative importance of male parental investment.

The effects of stress and parasites on the expression of dominance and secondary sexual characters

Male reproductive phenotypic plasticity related to environmental–social conditions is common among teleost fish. In several species, males adopt different mating tactics depending on their size, monopolizing mates when larger, while parasitizing dominant male spawns when smaller. Males performing alternative mating tactics are often characterized by a strong dimorphism in both primary and secondary reproductive traits. According to studies on sex-changing species and on species where only one male morph is reproductively active, male alternative phenotypes are expected to vary also in gonadotropin-releasing hormone (GnRH) neurons in forebrain preoptic area (POA). Here, we compared the intra- and inter-sexual variations in number and size of GnRH neurons, along with gonads and male accessory structure investment, in two goby species, the grass goby, Zosterisessor ophiocephalus, and the black goby, Gobius niger, characterized by male alternative mating phenotypes. In both species, older and larger males defend nests, court and perform parental care, while younger and smaller ones try to sneak territorial male spawning. We found that grass goby and black goby have different patterns of GnRH expression. Grass goby presents a clear intra-sexual dimorphism in GnRH expression, related to the occurrence of alternative mating tactics, while in the black goby, only inter-sexual differences are observed. The inter- and intra-specific variability in the GnRH neurons in these two goby species is discussed in light of the differences in migratory behavior, nest type, and mating system.

Influences of Life History Attributes on Formation of Local and Distant Fern Populations

Population biology of pteridophytes has attracted considerable attention over the last 20 years as documented in successive reviews by Klekowski (1969), Lloyd (1974b), Klekowski (1979), Page (1979), Haufler (1987), Klekowski (1988), and Cousens (1988). Yet much remains unknown, particularly with respect to species' specific differences in reproduction and the reflection of these differences in species' demographic and distribution patterns. Homosporous pteridophytes as a group are often considered to be equivalent to one another in their ability to disperse and migrate (Tryon, 1970, 1972, 1986) and superior to seed plants with regard to species' dispersability (Smith, 1972; Tryon, 1986). These views are based primarily upon the presumed ease of dispersal of pteridophyte spores in comparison with seeds and a potential of homosporous ferns to reproduce by single spores capable of producing self-fertile bisexual gametophytes. Indeed, some species have these capabilities; examples of longrange and recent disjunctions and of wide-ranging species are readily found among homosporous pteridophytes (Wagner, 1972; Tryon, 1970, 1972, 1986; Smith, 1972). However, to extrapolate from these species to generalizations encompassing all homosporous pteridophytes obscures significant differences among species imposed by differences in fecundity, habitat requirements, mating systems, and gametophyte ecology (Klekowski, 1969, 1972, 1979, 1988; Lloyd, 1974a, 1974b; Cousens, 1979, 1981; Cousens et al., 1985; Cousens et al., 1988; Schneller, 1975, 1979; Grime, 1985; Farrar, 1976; Farrar & Gooch, 1975; Crist & Farrar, 1983; J. Peck, 1980; C. Peck, 1985). Species-specific characteristics in combination with local habitat characteristics, in fact, determine geographic ranges of fern species that are generally comparable to those of seed plants (Wagner, 1972) and bryophytes (Anderson, 1971; Crum, 1972). In an attempt to elucidate factors differentiating species' abilities to disperse via gametophyte reproduction, we have conducted complementary field and laboratory studies on a number of co-occurring fern species in Central Iowa. For purposes of comparison, we have divided fern life history into a series of successive stages and processes (Table 1), each of which contributes in serial fashion to the species' overall reproductive potential. Most of our work has been conducted at a state preserve where sixteen pteridophyte species are

Species differences in response to conspecific intruders inCallithrix jacchus andSaguinus oedipus

In this study, the first performed on two species of callitrichid primates under identical conditions, the responses elicited in newly mated individuals by conspecific intruders were compared in four pairs of Callithrix jacchusand four pairs of Saguinus oedipus.Intruders were systematically varied in terms of sex and the social context in which they were met. Clear sexual dimorphism was observed in the behavior of Saguinus oedipus,but the behavior of males and females was less dimorphic in Callithrix jacchus.Males and females of both species showed an increase in agonistic and display behavior in the presence of same-sex intruders, but the mode of behavior varied both with sex and species. Social facilitation, as indicated by increased frequencies of agonistic and display responses in the presence of a mate, was observed only in males of both species. Neither C. jacchusnor S. oedipusdisplayed clear evidence of a monogamous mating system like that of Callicebusor of a polygynous mating system like that of Saimiri.Observed differences in the responses to conspecifics between these two species in the laboratory may be explained by facultative differences in mating systems resulting from differences in ranging and foraging behavior under freeranging conditions.

Reproductive correlates of mating system variation in Eichhornia paniculata (Spreng.) Solms (Pontederiaceae)

AbstractComparative studies of related plant species indicate that evolutionary shifts in mating systems are accompanied by changes in reproductive attributes such as flower size, floral morphology, and pollen/ovule ratio. Recent theoretical work suggests that patterns of investment in reproduction should also change with the mating system. In a glasshouse study, we investigated the extent to which mating system differences among populations of Eichhornia paniculata (Pontederiaceae) were correlated with changes in allocation to male and female function, floral display, and the regulation of investment in reproduction through fruit and ovule abortion.Significant differences in the amount of biomass allocated to reproductive structures were evident among six populations of E. paniculata. As predicted by sex allocation theory, the proportion of dry weight allocated to male function decreased with the outcrossing rate of populations. Six of the eight attributes used to characterize floral display also differed significantly among populations. However, with the exception of two attributes describing the number of flowers produced by inflorescences, these were not correlated with outcrossing rate. Levels of fruit and ovule abortion were determined in two populations with contrasting mating systems under different nutrient and pollination treatments. Virtually all fruits initiated by plants from a self‐fertilizing population were matured, while the amount of fruit abortion in an outcrossing population increased with flower production. Ovule abortion was low in both populations. Our results demonstrate that the evolution of self‐fertilization in E. paniculata is associated with changes in investment to reproduction that normally distinguish selfing and outcrossing species.

Female-to-male shift of mouthbrooding in a cichlid fish, Tanganicodus irsacae, with notes on breeding habits of two related species in Lake Tanganyika

Parental-care patterns and mating systems of three goby-like cichlids in Lake Tanganyika were investigated. In Tanganicodus irsacae females mouthbrooded eggs and small young for about two weeks and then males took over the role for about one week. Field observations of tagged fish suggest that this species is monogamous: a male's home range largely overlapped with that of its mate, while their home ranges were segregated from those of similar-sized consexual adults. Eretmodus cyanostictus also performed female-to-male shift of mouthbrooding and appeared to be monogamous. The third species, Spathodus marlieri, however, exhibited exclusively maternal mouthbrooding. The differences in parental care and mating system among the three species are discussed in relation to their feeding habits, and the pattern of monogamy in the goby-like cichlids is compared with those of other fishes.

Familiarity and female mate choice in two species of voles ( Microtus ochrogaster and Microtus montanus)

The effect of familiarity on female mate choice was examined in prairie voles ( Microtus ochrogaster) and montane voles ( M. montanus). In experiment I females were given simultaneous access to a male with which they had just mated and to a novel male. Prairie vole females mated preferentially and spent more time with the familiar males; montane voles showed no preference. Experiment II consisted of two tests in which familiarity was established by housing a female across a wire mesh barrier from a male for 2 weeks. Female prairie voles showed no preference based on familiarity. Overriding any effect of adjacent housing was a preference in the second test for the male from which they received their first ejaculate in test 1. Montane voles spent more time with the unfamiliar male. Therefore, in prairie but not montane voles, copulation and/or the receipt of an ejaculate appears to be responsible for the ‘stamping in’ of a preference for a particular male. These results suggest that finely tuned differences in a female's reproductive responses to familiar and unfamiliar males may be proximate behavioural processes underlying species differences in mating systems.

Social Behavior of Males and Simultaneous Hermaphrodites in the Lantern Bass

AbstractSerranus baldwini (Serranidae), the lantern bass, is a small, gleaning carnivore found in turtle grass and rubble substrates in the Caribbean. Small S. baldwini are simultaneous hermaphrodites, but large members of this species are males. The males patrol territories in which several hermaphrodites reside. Hermaphrodites spawn as females with the resident males and rarely spawn as males themselves. Unlike the pattern in reciprocating hermaphrodites, courtship is largely a male function in S. baldwini. Males are much more active and aggressive than are hermaphrodites. In reciprocally spawning species, interactions among mates are more symmetrical. The behavior patterns found in the serranines reflect the differences in mating systems in a manner similar to that found in other organisms and is consistent with current mating system theory.

Nesting Biology, Seasonality, and Mating System of Malaysian Fantail Warblers

The breeding biology of Fantail Warblers (Cisticola juncidis) in a rice field in northwestern peninsular Malaysia was studied. Data were collected on 38 nests found in rice plants on the 15-ha study area. Clutch size was three or four, incubation lasted 10-14 days, and fledging occurred 14-15 days after hatching. Two breeding seasons occurred annually, January-March and June-September, coinciding with the availability of suitable rice field nesting cover. The presence of several closely spaced, simultaneously active nests on plots occupied by single male birds indicated a polygynous mating system. This was based on the ability of some males to monopolize the limited available nesting habitat early in the rice-growing cycle. These findings differ from those of previous studies, presumably because of differences in the habitat types and mating systems examined. The Fantail Warbler (Cisticola juncidis) is a small sylviid widely distributed in tropical and temperate parts of Europe, Africa, Asia, and Australia. It chiefly inhabits wet grassy areas and rice fields and is rather secretive except during the breeding season when males perform conspicuous aerial displays (Lynes 1930, Givens and Hitchcock 1953). Recent studies in Japan (Motai 1973), France (Robert and Bellard 1975), and Australia (Ey 1977) indicate that the species may be regularly polygynous throughout a substantial part of its range. In this paper, I present results of a study of the nesting biology and mating system of the Fantail Warbler in a Malaysian rice field environment. This research was part of an investigation of the influence of rice cultivation on the breeding seasonality of certain common rice field birds (Avery 1980), and it is the first detailed account of Fantail Warbler breeding biology from the Malayan region since Gibson-Hill's (1950) study, which was conducted on Singapore during the mid-1940's. STUDY AREA AND METHODS The study area consisted of 15 ha of experimental rice fields at the Rice Research Center of the Malaysian Agricultural Research and Development Institute at Bumbong Lima, Northern Province Wellesley (5033'N, 100028'E). The fields were irrigated, and two crops of rice were harvested annually in March-April and September-October. The study period was June 1975-March 1977. Most nests were found by observing the movements of adult birds carrying nest material or food. Other nests were pointed out to me by field workers. I visit6d each nest site every second or third day and recorded the number of eggs or young and the presence or absence of adults. Several nests were observed using a spotting scope in order to monitor the foraging activity of female birds. Boundaries between breeding territories were estimated by observing encounters between males during aerial displays. I distinguished sexes of adult birds by plumage differences (Chasen 1939) and behavioral traits (during the breeding season, males make extended song flights whereas females make brief, low, usually silent flights). Recently fledged birds were easily distinguished from adults by the yellow wash on the pale feathers of the breast and abdomen. Throughout the study, I mist-netted and banded birds, but did ot uniquely mark them for sight identification. Thus, individual recognition in the field was not possible. Field counts of birds on the study area were made an average of three times weekly to obtain an indication of population levels.

Genetic variation inSolanum pennellii: Comparisons with two other sympatric tomato species

Genetic variation—primarily in 19 genetic loci of seven enzyme systems—was analyzed in accessions from various parts of the geographic range ofSolanum pennellii, which according to all tested biosystematic criteria behaves like a species ofLycopersicon. In comparison with the largely sympatricL. hirsutum andL. pimpinellifolium, this species exhibits the same trends of reduced allogamy and decreased genetic variation toward the north and south margins of its distribution, though to a much lesser degree; it does not exhibit their trends toward smaller flower size in the same peripheral regions. All three species agree to a considerable extent in the ranking of their tested loci in respect to degree of variablility; however, overall polymorphy is highest inS. pennellii. Except for the appearance of self-compatibility at its southernmost margin,S. pennellii is exclusively and rigidly self-incompatible. Alleles are distributed much more uniformly over the range than in the previously mentioned species, marginal and internal endemic mutants being much less abundant. A marked geographic disagreement is evident in regions of high and low variation. These differences in patterns of genetic variability are reconciled in terms of observed differences in mating systems, probable age of distributions, and adaptive strategies.

Genetic factors influencing atrophic rhinitis in the pig

ABSTRACTData from 1447 pigs from 438 litters were used to estimate heritability, breeding and mating system differences and heterosis of atrophic rhinitis. Yorkshire, Landrace and Lacombe breeds and their crosses were represented. Rhinitis was measured by necropsic examination of the degree of degeneration of the nasal turbinates. Two traits were considered: rhinitis incidence, based on whether or not pigs showed any nasal turbinate degeneration; and rhinitis score, which ranged from zero to four, based on the percentage of nasal turbinate degeneration exhibited. Heritabilities of rhinitis incidence and score were 0·12±0·09 and 0·03±0·02, respectively. Mating system differences were significant but differences between crosses within mating system were not. Estimates of heterosis of two-breed, backcross and three-breed cross pigs over purebreds were respectively, 1·1, 3·4 and 22·1% for rhinitis incidence and 10·1, 13·2 and 28·5% for rhinitis score.

COMPARISON OF DIFFERENT BREEDING PLANS FOR EVALUATING SIRES AND MATING SYSTEMS IN SWINE

The effects of sires and mating systems on growth and carcass traits were investigated using within-litter (double mating), within-dam (sequential mating) and between-litter (random mating) comparisons. All three breeding plans were studied at a research station and, in addition, random matings were studied in the field. The experimental data consisted of 80 double mating litters (697 pigs), 302 sequential mating litters and 718 random mating litters whereas the field data comprised 622 random mating litters. Sire effects were important for postweaning growth and carcass merit whereas mating system differences were important only for postweaning growth. Based on estimates of the number of litters required to detect significant differences between sires or mating systems, double mating was the most efficient breeding plan. This advantage was most pronounced for the early growth traits.