On dominance relations and the structure of animal societies: I. Effect of inherent characteristics

Societies are considered in which a non-transitive dominance relation exists between every pair of members, such as the peck-right in a flock of hens. A one-dimensional measure of the structure of such a society,h, is defined, withh=0 for equality andh=1 for the hierarchy. It is assumed that each member of the society is characterized by an ability vector whose components depend on individual characteristics such as size, concentration of sex hormone, etc., but not on social factors such as social rank. The distribution of abilities among members of the society is assumed to be given by a distribution function which is the same for all members, and the probability that one member dominates another is given by a function of the ability vectors of the two. On these assumptions formulas for the expected (mean) value and variance ofh are determined in terms of the distribution and dominance probability functions. Some special cases are calculated, especially that for normany distributed abilities and dominance probability given by the normal probability integral. Several conclusions are derived. If all members are of equal ability, so that dominance probability is 1/2, then any sizable society is much more likely to be near the equality than the hierarchy; and, as the size of the society increases, the probability that it will be near the hierarchy becomes vanishingly small. If the dominance probability is a weighted sum of several independent components, which make up the ability vector, then the society is less likely to be close to the hierarchy as the number of these components increases. The hierarchy is the prevalent structure only if unreasonably small differences in ability are decisive for dominance. From this it appears that the social factors, or psychological factors such as the previous history of dominance, which are not included in the present treatment, may be of great importance in explaining the observed prevalence of structures very close to the hierarchy in flocks of domestic hens.     

A cladistic analysis of interspecific relationships ofSaguinus

The dental and cranial morphologies of all species ofSaguinus, S. oedipus, S. geoffroyi, S. leucopus, S. nigricollis, S. fuscicollis, S. labiatus, S. mystax, S. imperator, S. bicolor, andS. midas are examined. The following hypotheses are developed by cladistic methodology, using only synapomorphic characters to assess the interspecific relationships ofSaguinus.Saguinus are divided into two main groups; one consists ofS. oedipus, S. geoffroyi, andS. leucopus, and the other includesS. inustus, S. nigricollis, S. fuscicollis, S. labiatus, S. mystax, S. imperator, S. bicolor, andS. midas. In the former group,S. oedipus is more closely related toS. geoffroyi than either is toS. leucopus. In the latter group,S. labiatus, S. mystax, andS. imperator are classified into one group, andS. bicolor andS. midas form one monophyletic group.     

The distribution of P-element sequences inDrosophila: Thewillistoni andsaltans species groups

Summary This report describes the distribution of P-element sequences among members of the closely relatedwillistoni andsaltans species groups of the subgenusSophophora. Gel-blotting analyses showed that many, but not all, species from each of these groups possess sequences with homology to the P transposable element ofDrosophila melanogaster, a sophophoran species belonging to themelanogaster species group. Furthermore, P-homologous fragments are present in lower numbers inwillistoni- andsaltans-group species than inD. melanogaster P strains, and, in some species of those two groups, exhibit species-characteristic hybridization patterns. On the basis of these results, it is proposed that P elements have had a long evolutionary history in thewillistoni andsaltans lineages.     

Preliminary analysis of numerical taxonomy of the genusSaguinus based on dental measurements

Although several investigations have been made from different viewpoints, the classification or interspecific relationships ofSaguinus still remain uncertain. In the present study, we applied multivariate analysis methods to dental measurements of part ofSaguinus populations of sufficient sample size and obtained the following conclusions.Saguinus can be classified into two main groups: one consists ofS. oedipus andS. leucopus, and the other ofS. fuscicollis, S. nigricollis, S. labiatus, andS. mystax. Concerning the former group, the two subspecies ofS. oedipus, S. o. oedipus, andS. o. geoffroyi, show a close affinity with each other and also a close relationship toS. leucopus, while the latter group consists of two subgroups of species, one includingS. fuscicollis andS. nigricollis, and the other includingS. labiatus andS. mystax. The biological distance betweenS. oedipus oedipus andS. o. geoffroyi is slightly larger than that between the pairs ofS. fuscicollis andS. nigricollis and ofS. labiatus andS. mystax. Factor analysis revealed significant factors which could explain the differences among the seven maleSaguinus populations. Taking all the results into account, it seems necessary to reconsider the phylogenetic relationships within the genusSaguinus.     

Further report on object manipulation in non-human primates: A comparison within 13 species of the genusMacaca

Thirteen captive species of the genusMacaca were presented with certain non-edible objects and the subsequent manipulation was observed. The following results were obtained: (1) Thefascicularis group species displayed a great variety in rolling the manipulandum, which has been reported to be one of the actions characterizing cercopithecine species; (2) manipulating the object with one finger was typical of thesilenus-sylvanus andsinica groups, whereas use of the fingers moving opposably was common to all species ofMacaca; (3) secondary manipulations in relation to the wire-mesh were observed only inM. silenus, M. sinica, andM. nemestrina, whereas those in relation to water were common to allMacaca species; and (4) within-subgroup differences were great in thesilenus-sylvanus andsinica groups as compared to thefascicularis group.     

Morphological variation inLolium (Poaceae) as a measure of species relationships

Analysis of morphological and phenological data for determining the genetic variation within sevenLolium species led to the recognition of two groups within this genus. One group, containing the two inbreeding speciesL. temulentum andL. persicum, was clearly distinct from all other species. Strong morphological and phenological intergradation was found between both species. The cross-breeding species,L. perenne, L. rigidum, andL. multiflorum, formed another group. Little differentiation was found between these species, though they were distinct. Two inbreeding species,L. loliaceum andL. remotum, were clearly distinct from each other and the two groups.L. loliaceum had an isolated position and was most related toL. rigidum. L. remotum had an intermediate position between the cross-breeding and inbreeding species, and was almost equally distant from all three cross-breeding species.Genetic variation inLolium spp. I.     

Phylogenetic relationships ofPseudopanax species (Araliaceae) inferred from parsimony analysis of rDNA sequence data and morphology

Sequence data from internal transcribed spacer (ITS) regions of rDNA and data from morphology, cytology and wood anatomy are used to study phylogenetic relationships inPseudopanax. The molecular and non-molecular data are analysed as independent data sets and in combination using parsimony. Results supported the conclusion that the genusPseudopanax is polyphyletic.Pseudopanax species emerge in two major monophyletic groups. The Anomalus group containsPseudopanax anomalus, P. edgerleyi, andP. simplex; these species share a common ancestor withCheirodendron trigynum and more distantly withPseudopanax gunnii. The second major group consists of two smaller groups: the Arboreus group, includingPseudopanax arboreus, P. colensoi, P. kermadecensis, P. laetus, andP. macintyrei, and the Crassifolius/Discolor group, includingP. chathamicus, P. crassifolius, P. discolor, P. ferox, P. gilliesii, P. lessonii, andP. linearis. Meryta species are close relatives of thePseudopanax Arboreus and Crassifolius/Discolor groups.     

Asian colobine social structure: Ecological and evolutionary constraints

Both ecological and phylogenetic factors and their interaction influence primate social structure. Food resources, in particular, affect social structure parameters such as sex/age composition, group size, home range size, and individual density. As a group, the Asian colobines may be partially buffered from the impact of food constraints on social structure, given their specialized digestive physiology. Asian colobines are able to subsist on mature foliage, a relatively abundant and non-patchily distributed resource, when preferred foods are not available. In food limited populations, increases in group size or density should cause increases in home range size. We did not find this relationship for Asian colobines, however, and thus it would appear that the majority of Asian colobine populations are below carrying capacity. Food may be less of a limitation to populations than other factors, such as social stress. The formation of bands (associations between relatively stable groups) has been documented for bothNasalis andRhinopithecus, and based on recent data for severalPresbytis andTrachypithecus species, we predict that band formation is the norm for the Asian colobines, includingPygathrix. Group home ranges forPresbytis andTrachypithecus species typically overlap and both intergroup tolerance and intergroup aggression are observed. This suggests that groups form differentiated relationships, tolerating some groups but not others. Such differentiated relationships are the foundation of band formation.     

A phylogenetic dissection of the family micrococcaceae

A comparative analysis of 16S ribosomal RNA sequences in the Micrococcaceae shows the family not to be a phylogenetically coherent unit. In fact, at least two of its three genera are themselves not valid phylogenetic units. Species, of the genusMicrococcus are phylogenetically inseparable from those ofArthrobacter. The genusPlanococcus groups specifically with certain members ofBacillus, andStaphylococcus is also related to the genusBacillus, though more peripherally. These findings question the validity of spherical shape as a valid indicator of phylogenetic relationships on all but the lowest levels.     

Spread of information through a population with socio-structural bias: I. Assumption of transitivity

A previously derived iteration formula for a random net was applied to some data on the spread of information through a population. It was found that if the axon density (the only free parameter in the formula) is determined by the first pair of experimental values, the predicted spread is much more rapid than the observed one. If the successive values of the “apparent axon density” are calculated from the successive experimental values, it is noticed that this quantity at first suffers a sharp drop from an initial high value to its lowest value and then gradually “recovers”. An attempt is made to account for this behavior of the apparent axon density in terms of the “assumption of transitivity”, based on a certain socio-structural bias, namely, that the likely contacts of two individuals who themselves have been in contact are expected to be strongly overlapping. The assumption of transitivity leads to a drop in the apparent axon density from an arbitrary initial value to the vicinity of unity (if the actual axon density is not too small). However, the “recovery” is not accounted for, and thus the predicted spread turns out to beslower than the observed.     

Morphological review ofPelvetia andSilvetia (Fucaceae, Phaeophyta) with an emphasis on phylogenetic relationships

We compared the morphology of all four members ofPelvetia andSilvetia (Fucaceae, Phaeophyta), with an emphasis on phylogenetic relationships.Silvetia is segregated fromPelvetia because it has two, longitudinally divided eggs in the oogonium. In contrast, the eggs of the genusPelvetia are transversally divided. A cladistic analysis, based on 17 morphological features, shows thatPelvetia is closely related toHesperophycus andPelvetiopsis, as are three species ofSilvetia. We can infer from the cladistic tree and biogeographic information that some silvetian ancestor populations from the northern Pacific region likely evolved toS. babingtonii in northern Japan and then moved to Korea and California (USA), whereS. siliquosa andS. compressa, respectively, diverged. Our morphological study corroborates the DNA-based phytogeny and the ensuing taxonomy for the two genera. These results demonstrate the necessity for systematically revising the family Fucaceae to emphasize egg development, rather than egg number, in the oogonium, as a diagnostic character.     

Mathematical biosociology of beliefs and prejudices

Following a suggestion made previously (Bull. Math. Biophysics,13, 61, 1951), it is assumed that every individual has both a tendency to behavearationally, by accepting everything on faith, and rationally, by subjecting everything to rational analysis. Arational behavior is characterized by various beliefs, prejudices, etc., which are considered to be conditioned reactions, learned by the individual before he completely develops his faculties for rational thinking. The two tendencies are assumed to be due to excitations of two different regions of the central nervous system, and are measured by the intensities ɛ _f and ɛ _r of those excitations. Those intensities are further assumed to increase linearly with time, the increases of the two beginning, in general, at different ages. The rates of increase are considered as normally distributed in the population. The relative frequency of arational and rational behavior is determined by the difference φ=ɛ _f =ɛ _r according to equations 0 developed previously (Bull. Math. Biophysics,11, 255, 1949). It is shown that with the above assumptions the majority of the population, which starts with arational behavior, will, within two or three of generations, either change to rational behavior or continue indefinitely to behave arationally. This will hold as long as imitative factors are present. Expressions for the numbers of individuals who behave rationally and arationally are derived. If the intensity of conditioning toward an arational behavior decreases with increasing size of the rationally behaving minority, or, if the rationally behaving individuals are not influenced by imitation, then a slow secular trend toward rational behavior may be present. An expression is also derived for the fraction of individuals who behave rationally as a function of age. This fraction increases with increase of the age at which the beginning conditioning toward any beliefs or prejudices begins.     

Systematic relationships of theSaxifragales revealed by serological characteristics of seed proteins

Comparative investigations of serological characters of seed proteins from taxa regarded as members of theSaxifragales result in the recognition of two distinct groups of related families. One consists of theSaxifragaceae, Grossulariaceae, andCrassulaceae; to itHamamelis, and possiblyPenthorum and theRosaceae may be connected. The second group contains theHydrangeaceae, Escalloniaceae, Roridulaceae, Cornaceae, andCaprifoliaceae; it is rich in iridoid compounds, has more derived morphological characters, and seems to represent a monophyletic line block. ThePittosporaceae were not found to be linked with either of the two groups, but rather show similarities with members of theApiales. All these data support systematic arrangements proposed byDahlgren (1975a).     

New perspectives on bacterial ferredoxin evolution

Summary Recent evidence indicates that a gene transposition event occurred during the evolution of the bacterial ferredoxins subsequent to the ancestral intrasequence gene duplication. In light of this new information, the relationships among the bacterial ferredoxins were reexamined and an evolutionary tree consistent with this new understanding was derived. The bacterial ferredoxins can be divided into several groups based on their sequence properties; these include the clostridial-type ferredoxins, theAzotobacter-type ferredoxins, and a group containing the ferredoxins from the anaerobic, green, and purple sulfur bacteria. Based on sequence comparison, it was concluded that the amino-terminal domain of theAzotobacter-type ferredoxins, which contains the novel 3Fe3S cluster binding site, is homologous with the carboxyl-terminal domain of the ferredoxins from the anaerobic photosynthetic bacteria.A number of ferredoxin sequences do not fit into any of the groups described above. Based on sequence properties, these sequences can be separated into three groups: a group containingMethanosarcina barkeri ferredoxin andDesulfovibrio desulfuricans ferredoxin II, a group containingDesulfovibrio gigas ferredoxin andClostridium thermoaceticum ferredoxin, and a group containingDesulfovibrio africanus ferredoxin I andBacillus stearothermophilus ferredoxin. The last two groups differ from all of the other bacterial ferredoxins in that they bind only one FeS cluster per polypeptide, whereas the others bind two. Sequence examination indicates that the second binding site has been either partially or completely lost from these ferredoxins.Methanosarcina barkeri ferredoxin andDesulfovibrio desulfuricans ferredoxin II are of interest because, of all the ferredoxins whose sequences are presently known, they show the strongest evidence of internal gene duplication. However, the derived evolutionary tree indicates that they diverged from theAzotobacter-type ferredoxins well after the ancestral internal gene duplication. This apparent discrepancy is explained by postulating a duplication of one halfchain sequence and a deletion of the other halfchain. TheClostridium thermoaceticum andBacillus stearothermophilus groups diverged from this line and subsequently lost one of the FeS binding sites.It has recently become apparent that gene duplication is ubiquitous among the ferredoxins. Several organisms are now known to have a variety of ferredoxins with widely divergent properties. Unfortunately, in only one case are the sequences of more than one ferredoxin from the same organism known. Thus, although the major features of the bacterial ferredoxin tree are now understood, a complete bacterial phylogeny cannot be inferred until more sequence information is available.     

Taxonomic separation ofKengyilia (Poaceae: Triticeae) in relation to nearest relatedRoegneria,Elymus, andAgropyron,based on some morphological characters

Based on 100 species representative of the four genera, we scored 290 herbarium specimens for a number of morphological characters. The data were subjected to canonical discriminant analysis using characters different from those in the identification key to these genera byBaum, Yen, andYang (1991). These characters collectively support the four groupsAgropyron, Kengyilia, Roegneria, andElymus as previously defined. The four groups are also supported by the linear discriminant function with an overall rate of 83% correct classification. Length of lemma awn was found to be an additional diagnostic character asAgropyron andKengyilia have lemma awns shorter than 5 mm, whereasRoegneria andElymus have longer lemma awns with very few exceptions. Length of glume awns is also a useful supplementary generic diagnostic.Agropyron andElymus have glume awns, whereas the majority of species ofKengyilia and more than half of the species ofRoegneria lack them. If a glume awn is present it is usually not longer than 1 mm.     

Gene duplication and polymorphism at the amylase loci ofMacaca fascicularis andMacaca mulatta

Plasma amylase obtained from twoMacaca species,M. fascicularis andM. mulatta, was investigated by isoelectric focusing. In contrast to recent works, extensive polymorphism at the amylase loci was detected in both species. It is assumed that unequal crossing over has generated two pancreatic loci. The phylogenetic relationship between the species is recalculated. The average identity value is calculated from data obtained byNozawa et al. (1977),I=0.93. If the polymorphic amylase loci are included the genetic identity decreases by at least 2% (I=0.91), meaning that the divergence time between both species would increase by about 30%. Furthermore, the mean degree of heterozygosity also increases by about 30% to 0.10 and the effective population size is underestimated by at least the same order of magnitude.     

The effect of three species of mites upon fungal growth on wheat

Every week, for 20 weeks, the growth of naturally occurring grain storage fungi on wheat infested with the three commonest British grain storage mites,Acarus siro, Glycyphagus destructor andTyrophagus longior, was compared with that on uninfested wheat.The number of colonies of theAspergillus glaucus group per gram were always less on grain infested with mites than on uninfested grain.Penicillium spp. were also less numerous on grain which was infested withA. siro but did not appear to be affected by the other mites. In contrast, two fungi which are pathogenic to mites,Aspergillus restrictus andWallemia sebi, were more abundant in the presence of certain mites. The former was associated withG. destructor, the latter withG. destructor andA. siro.The three species of mites either feed on theA. glaucus group andPenicillium spp., or inhibit them by an unknown secretion. Pathogenic fungi are probably avoided. Mites are therefore an important variable in studies on fungal growth during grain drying and storage.     

The effects ofTilapia introductions in Lake Luhondo,Rwanda

Synopsis Cyprinid fishes apparently constituted the major part of the original fish fauna in Lake Luhondo, Rwanda, at least until 1934. At that time only three species, all cyprinids, were known from the lake:Barbus neumayeri, a small barbel, very common in the lake (described from the lake asBarbus luhondo) and two larger cyprinid species:Barbus microbarbis andVaricorhinus ruandae. These two large species were probably not very common in the lake. Between 1935 and 1938 some youngTilapia were introduced into Lake Luhondo. Since then and certainly since 1952 the large cyprinids seem to have disappeared completely from the lake. The smallBarbus neumayeri has become extremely rare; at present it survives only in some small tributaries of the lake. In the lake itselfTilapia andHaplochromis species are now the dominant fauna. A survey of the available information is given.Africa-Museum, Steenweg op Leuven, B-1980 Tervuren, Belgium (mailing address)     

Interspecific relationships ofCallithrix based on the dental characters

The dental structure of all species ofCallithrix, C. argentata, C. humeralifer, C. aurita, C. flaviceps, C. geoffroyi, C. penicillata, andC. jacchus is examined.Callithrix are divided intoC. jacchus group andC. argentata group, based on the analysis of dental characters.C. jacchus group consists ofC. jacchus, C. penicillata, C. geoffroyi, C. flaviceps, andC. aurita, whileC. argentata andC. humeralifer are assigned toC. argentata group. InC. jacchus group,C. aurita andC. flaviceps were differentiated from the original stock of their common ancestor, followed byC. geoffroyi, last byC. penicillata, and finallyC. jacchus. Based on the relationships among species ofCallithrix, it is possible to infer the relative age of the formation of the refuges which caused their speciation. First, the forests in southeastern Brazilian coast were split from Amazonia. In southeastern Brazilian coast, the Paulista center separated, followed by the Rio Doce center, the Bahia center, finally by the Pernambuco center.     

The effect of a species-specific avoidance response to predatory starfish on the intertidal distribution of two gastropods

Summary The gastropodsAcmaea (Collisella) limatula andAcmaea (Notoacmea) scutum respond to water flowing over certain predatory starfish (i.e. to the scent of the starfish) by moving rapidly up a submerged, vertical surface. These limpets respond with upward movement to the scent ofPisaster ochraceus, Pisaster giganteus, Pycnopodia helianthoides, andLeptasterias aequalis. All of these starfish are predators on molluscs and at least occasionally inhabit the intertidal. In contrast, the limpets respond weakly or not at all to the scent ofPatiria miniata andPisaster brevispinus. Patiria is an omnivorous scavenger, andP. brevispinus is predaceous but strictly subtidal when it occurs on rocky shores. For the starfish tested, then, the limpets only give avoidance responses to starfish species naturally encountered as predators.The avoidance response ofA. limatula andA. scutum to predatory stafish can also be demonstrated in the field. When onePisaster ochraceus is placed beneath a population of limpets in the intertidal and confined so that contacts between the starfish and limpets are impossible, the limpet population is displaced significantly upward after one tidal cycle. In addition, the closer the limpets are to the starfish, the greater is their upward displacement.