Correlations between secondary-product chemistry and ecogeography in theRamalina siliquosa group (Lichens)

The increasing degree of oxidation of the major secondary products characterizing six sibling species of theRamalina siliquosa complex is directly correlated with the northern limits of the ranges of the chemotypes in Europe. In the telescoped environments on maritime cliffs, the zonation of sympatric chemotypes shows similarities to this correlation.     

Analysis of chemical and morphological variation in the Ramalina siliquosa species complex

In an attempt to clarify the taxonomy of the polymorphic maritime lichens of theRamalina siliquosa group in Europe, variation was analyzed in visible and chemical characteristics of 1042 specimens from four localities (one station each in Scotland, Wales, England, and Brittany). The plants belong to six major chemical types representing a replacement series of closely related medullary depsidones. There is a broad correlation of chemical and visible traits. The narrower-lobed often basally blackened individuals (corresponding approximately to the usual concept of “R. curnowii”) produce no medullary constituents nor norstictic or stictic acids. The broader-lobed unblackened ones (corresponding approximately to the usual concept of “R. siliquosa”) produce stictic, salazinic, protocetraric, or hypoprotocetraric acids. The proportion of each chemical type in the four populations studied varies markedly. The southern (English and French) populations together contain all six chemical variants in roughly similar proportions. However, to the north, in Wales and Scotland, the populations become simpler as some chemical races drop out and salazinic acid-producing plants predominate. These findings correlate well with the general geographic distribution of the chemical variants from a study of 117 herbarium specimens. The chemically distinct plants have different amplitudes of ecologic tolerance which appear to regulate niche selection in theRamalina zone, the conspicuous vegetational belt which these lichens form above the intertidal zone on the Atlantic and Baltic coasts of Europe. The complex is interpreted as a set of six species differing to an extent by visible traits but primarily by chemical, geographical, and ecological ones. Three of the species are new:Ramalina atlantica Culb.,R. stenoclada Culb., andR. druidarum Culb. A hypothetical scheme is suggested to explain the evolutionary origin of the species recognized.     

General review of tick species present in Portugal

At present, 24 species are known to occur in Portugal: Argas vespertilionis, Ornithodoros maritimus and Ornithodoros erraticus in Argasidae; Ixodes acuminatus, Ixodes bivari, Ixodes canisuga, Ixodes frontalis, Ixodes hexagonus, Ixodes ricinus, Ixodes simplex simplex, Ixodes ventalloi, Ixodes vespertilionis, Dermacentor marginatus, Dermacentor pictus', Haemaphysalis hispanica, Haemaphysalis inermis, Haemaphysalis punctata, Rhipicephalus bursa, Rhipicephalus pusillus, Rhipicephalus sanguineus, Rhipicephalus turanicus, Hyalomma lusitanicum, Hyalomma marginatum marginatum and Boophilus annulatus in Ixodidae. The more relevant diseases transmitted to cattle by ticks, particulary in Ribatejo and Alentejo regions, are the babesiosis due to Babesia bigemina and Babesia bovis, the theileriosis by Theileria annulata and the anaplasmosis due to Anaplasma marginale; the theileriosis by Theileria mutans2 may not be considered significant. The sheep and goats parasitoses transmitted by ticks are of less importance than the cattle diseases. However the babesiosis due to Babesia motasi and Babesia ovis and also theileriosis by Theileria hirci3 are present in some districts of the country.     

The evolution of oscillatory behavior in age-structured species

A major challenge in ecology is to explain why so many species show oscillatory population dynamics and why the oscillations commonly occur with particular periods. The background environment, through noise or seasonality, is one possible driver of these oscillations, as are the components of the trophic web with which the species interacts. However, the oscillation may also be intrinsic, generated by density-dependent effects on the life history. Models of structured single-species systems indicate that a much broader range of oscillatory behavior than that seen in nature is theoretically possible. We test the hypothesis that it is selection that acts to constrain the range of periods. We analyze a nonlinear single-species matrix model with density dependence affecting reproduction and with trade-offs between reproduction and survival. We show that the evolutionarily stable state is oscillatory and has a period roughly twice the time to maturation, in line with observed patterns of periodicity. The robustness of this result to variations in trade-off function and density dependence is tested.     

The species concept in a long-extinct fossil group,the conodonts

Conodonts are an extinct group of organisms, known from the Upper Cambrian to the Triassic. They have no extant representatives, and tooth-like buccal elements are usually the only remains of the animal found in the sediments. Therefore, most of their taxonomy rests on these elements that are good stratigraphic tools for these ancient periods, due to their rapid morphological evolution. Conodont species are usually described species that are based on either clusters of elements corresponding to an entire apparatus (natural assemblages), or on the most frequently preserved element. These described species are acceptable stratigraphic tools, but hardly consider the dimension of the variation that a biological species can encompass through time and space. In order to tackle temporal, environmental and biogeographical changes, recent studies have shown that morphological variation should be taken into account by quantitative analyses, aiming at getting at the closest of what the former species might have been.     

The sorediate, saxicolous species of the Lecanora subfusca group in Europe

The sorediate, saxicolous members of the Lecanora subfusca group, which include L. campestris ssp. dolomitica, L. caesiosora, L. pannonica , and L. umbrosa , although frequently misnamed, can be distinguished morphologically and chemically. Lecanora caesiosora is most variable, with a southerly form having a dark grey, thick thallus, and a more northerly, often shade-loving, morphotype having a very pale, thin thallus. The species are described, and a diagnostic key is presented including some confusable species. Lecanora pannonica and L. neglecta are neotypified.     

Encroachment of upland Mediterranean plant species in riparian ecosystems of southern Portugal

Riparian ecosystems have unique biodiversity, are highly sensitive to disturbance and anthropogenic influence. As world water resources become scarcer, scientists predict greater competition among species for water resources. Indeed, increased encroachment of upland plants into the riparian zone is already occurring, irreversibly changing riparian plant communities. Since semi-arid regions such as Mediterranean-type ecosystems are likely to follow this same trajectory, assessing the contributions of riparian versus upland (sclerophyllous) plants to community composition is important. A survey of seventy 2 km-long riparian transects on the Sado and Guadiana watersheds in southern Portugal assessed (1) the woody riparian plant community composition, (2) how much richness is due to strictly riparian plants versus sclerophyllous upland plants, and (3) which combinations of biotic and abiotic factors allow higher species richness in the strictly riparian, sclerophyllous, and overall plant communities. The survey detected 53 different woody plant species (28 endemic) across all communities. Riparian community richness was on average 16 species, seven of which were strictly riparian and the remainder being sclerophyllous, exotic species or fruit trees. Sclerophyllous plant species occurred consistently across sampling units (90% of transects). On average, 46% of the total woody plant community richness was due to strictly riparian plants and 28% was due to sclerophyllous plants. Community richness was positively affected by the area of shrubs in the riparian zone and by the absence of human activities and goats. Surrounding landscape pattern only affected the strictly riparian plant richness. These results suggest that natural and human-mediated disturbances in riparian ecosystems create gaps and clearings for which riparian and sclerophyllous plants compete. Establishment success seems to be related to the propagule pressure of the neighbouring landscape, its diversity and density, as well as the presence of herbivores. Preserving strictly riparian plants, removing exotic species, preventing grazing, and promoting riparian values (recreation, aesthetics and the provision of ecosystem services) will aid the future conservation of the unique biodiversity of riparian ecosystems.     

Patterns of inversion polymorphism in three species of the Drosophila melanogaster species group

In Drosophila, chromosomal polymorphism due to paracentric inversions is very common and constitutes an adaptive character. The degree of chromosomal variability varies in different species and also in different populations of the same species. Chromosomal polymorphism in Indian natural populations of three species, D. melaonogaster, D. ananassae and D. bipectinata which belong to the melanogaster species group has been studied and the quantitative data on frequency of inversions have been reported. Behaviour of chromosome inversions has also been studied in laboratory conditions. The present review summarises the work done on inversion polymorphism in Indian populations of three species which clearly demonstrates that these three species vary in their patterns of inversion polymorphism and have evolved different mechanisms for adjustment to their environments although they belong to the same species group.     

Phylogenetic incongruence in the Drosophila melanogaster species group

Drosophila melanogaster and its close relatives are used extensively in comparative biology. Despite the importance of phylogenetic information for such studies, relationships between some melanogaster species group members are unclear due to conflicting phylogenetic signals at different loci. In this study, we use twelve nuclear loci (eleven coding and one non-coding) to assess the degree of phylogenetic incongruence in this model system. We focus on two nodes: (1) the node joining the Drosophila erecta-Drosophila orena, Drosophila melanogaster-Drosophila simulans, and Drosophila yakuba-Drosophila teissieri lineages, and (2) the node joining the lineages leading to the melanogaster, takahashii, and eugracilis subgroups. We find limited evidence for incongruence at the first node; our data, as well as those of several previous studies, strongly support monophyly of a clade consisting of D. erecta-D. orena and D. yakuba-D. teissieri. By contrast, using likelihood based tests of congruence, we find robust evidence for topological incongruence at the second node. Different loci support different relationships among the melanogaster, takahashii, and eugracilis subgroups, and the observed incongruence is not easily attributable to homoplasy, non-equilibrium base composition, or positive selection on a subset of loci. We argue that lineage sorting in the common ancestor of these three subgroups is the most plausible explanation for our observations. Such lineage sorting may lead to biased estimation of tree topology and evolutionary rates, and may confound inferences of positive selection.     

Basal relationships in the Drosophila melanogaster species group

The Drosophila melanogaster species group is a popular model for evolutionary studies due to its morphological and ecological diversity and its inclusion of the model species D. melanogaster. However, phylogenetic relationships among major lineages within this species group remain controversial. In this report, the phylogeny of 10 species representing each of the well-supported monophyletic clades in the melanogaster group was studied using the sequences of 14 loci that together comprise 9493 nucleotide positions. Combined Bayesian analysis using gene-specific substitution models produced a 100% credible set of two trees. In the strict consensus of these trees, the ananassae subgroup branches first in the melanogaster species group, followed by the montium subgroup. The remaining lineages form a monophyletic clade in which D. ficusphila and D. elegans branch first, followed by D. biarmipes, D. eugracilis, and the melanogaster subgroup. This strongly supported phylogeny resolves most basal relationships in the melanogaster species group, and provides a framework that can be extended in the future to encompass more species.     

Systematics of yeast species in the Candida parapsilosis group

Summary The systematics ofCandida species that may or may not ferment carbohydrates and which assimilate trehalose, xylose, and mannitol, but do not assimilate lactose, melibiose, raffinose, inositol, dulcitol, or KNO₃ were examined. Included were:C. albicans, C. albicans var.stellatoidea, C. diddensii, C. bogoriensis, C. claussenii, C. lusilaniae, C. natalensis, C. obtusa, C. oregonensis, C. parapsilosis, C. parapsilosis var.querci, C. polymorpha, C. pulcherrima. C. reukaufii, C. solani, C. tropicalis, C. tropicalis var.lambica andC. viswanathii. The species were delimited and a basis for separation established.Contribution No. 800 from the Institute of Marine Science, University of Miami.This material was developed from a portion of a dissertation submitted in partial fulfillment of the requirements for the Ph. D. degree at the University of Miami, Coral Gables, Florida.Present address: Dept. of Food Science & Technology, University of California at Davis.     

The strategy of Myxococcus xanthus for group cooperative behavior

New evidence has been presented from our laboratory that the gliding bacterium, Myxococcus xanthus, does not home by chemotaxis toward a nutrient source. Our experiments, those of others, and the theory presented here combine to suggest a model, called the Pied Piper model. It hypothesizes a gene that has a high mutation rate forward and back (say something in excess 10^-4mutations per cell generation) which leads to switching between two motility states. Occasionally rare organisms become genetically, but reversibly, changed so that they move unidirectionally instead of mostly forward and back as do the bulk of the cells. When such a leader cell arises, it continues to move in its original orientation, and causes a cohort of cells to move together away from the bulk of the cells. That is, in the less common mutational state it counteracts the usual tendency to just move forward and backward achieving little net movement. The assumption of a genetic element that mutates in a reversible way is suggested by numerous cases of reversible switches now known in a wide range of bacteria serving a variety of functions. A second aspect of the model is that mechanisms exist that cause cells to move in the same direction as their nearby neighbors. This process results in a regular spacing of bands of cells to form mounds in the absence of a leader. The action of C-factor, a factor secreted by the cells which has been largely studied in the laboratory of Dale Kaiser, and extracellular fibrils, (rod-shaped protein and carbohydrate bodies) largely studied in the laboratory of Martin Dworkin, may be key elements in coordinating (or linking) the movements of neighboring cells. Based on the assumption of the absence of chemotaxis, computer simulations of pattern formation for gliding bacterial swarms and flares are consistent with observed behaviors and thus are additional evidence that chemotactic motility of the type exhibited by Escherichia coli, is not necessary for the group movements of M. xanthus. Some tests for this model are suggested.     

The causes of phylogenetic conflict in a classic Drosophila species group

Bifurcating phylogenies are frequently used to describe the evolutionary history of groups of related species. However, simple bifurcating models may poorly represent the evolutionary history of species that have been exchanging genes. Here, we show that the history of three well-known closely related species, Drosophila pseudoobscura, D. persimilis and D. p. bogotana, is not well represented by a bifurcating phylogenetic tree. The phylogenetic relationships among these species vary widely between different genomic regions. Much of this phylogenetic variation can be explained by the potential of different genomic regions to introgress between species, as measured in laboratory studies. We argue that the utility of multiple markers in species-level phylogenetic studies can be greatly enhanced by knowledge of genomic location and, in the case of hybridizing species, by knowledge of the functional or linkage relationships among the markers and regions of the genome that reduce hybrid fitness.     

Divergence in the ovipositional behavior of the Papilio glaucus group

This study contrasts the ovipositional profiles of four members of the Papilio glaucus group, P. glaucus , P. multicaudatus , P. canadensis , and P. rutulus. We used seven choice oviposition bioassays containing leaves from hosts in seven plant families utilized by members of the P. glaucus group. Specifically, we contrast the overall ovipositional profiles of these species and their acceptance of a host in a novel plant family ( Populus tremuloides : Salicaceae) and a host in a putatively ancestral host plant family ( Liriodendron tulipifera : Magnoliaceae). Significant differences were observed between the ovipositional profiles of P. glaucus and P. multicaudatus relative to each other and to P. canadensis and P. rutulus. In contrast, no significant differences were observed between the ovipositional profiles of P. canadensis and P. rutulus , which were also the only species that accepted P. tremuloides. Unlike the acceptance of P. tremuloides , the acceptance of L. tulipifera was present throughout the group despite the inability of the larvae of most species in the group to utilize this host. These results support the prediction of the "hierarchical threshold model" that ancestral host plants are likely to be retained in the ovipositional hierarchy while novel hosts should only be accepted by derived populations.     

The leader's role in controlling aggressive behavior in a monkey group

An established group of pigtailed monkeys (Macaca nemestrina) was evaluated for aggressive behavior. The four highest ranking members of the group were removed one-by-one. Aggression was higher during all periods when the leader was absent and it decreased when he was returned. The leader male of aM. nemestrina group plays the major role in the control of aggression within the group.This research was supported by Public Health Service Grant No. FR 00166 from the National Institutes of Health.Ruth A. Bobbitt provided statistical consultation.     

The spitting behavior of two species of spitting cobras

Spitting cobras defend themselves by spitting their venom in the face of a harasser. Although it is common belief that spitting cobras direct their venom at the eyes of an aggressor, this has never been investigated. Here, we show that the spitting act of cobras (Naja nigricollis and N. pallida) can readily be triggered by a moving human face or by a moving real size photo of a human face. In contrast, a stationary human face (real or photo) or a moving or stationary human hand does not trigger the spitting act. If threatened, spitting cobras aim their venom, ejected either in two distinct jets (N. pallida) or in a fine spray (N. nigricollis), either between the eyes or at one eye. In both cobra species investigated, the width and height of the area hit by the venom was independent of eye distance (test range 5.5 cm and 11 cm). During the spitting act the cobras performed fast undulating head movements that lead to a larger distribution of their venom. This behavior increases the probability that at least one eye of the aggressor is hit. Electronic Supplementary Material Supplementary material is available for this article at