Showing papers by "Universidade Federal de Minas Gerais published in 1996"

Characterizing reference locality in the WWW

Abstract: The authors propose models for both temporal and spatial locality of reference in streams of requests arriving at Web servers. They show that simple models based on document popularity alone are insufficient for capturing either temporal or spatial locality. Instead, they rely on an equivalent, but numerical, representation of a reference stream: a stack distance trace. They show that temporal locality can be characterized by the marginal distribution of the stack distance trace, and propose models for typical distributions and compare their cache performance to the traces. They also show that spatial locality in a reference stream can be characterized using the notion of self-similarity. Self-similarity describes long-range correlations in the data set, which is a property that previous researchers have found hard to incorporate into synthetic reference strings. They show that stack distance strings appear to be strongly self-similar, and provide measurements of the degree of self-similarity in the traces. Finally, they discuss methods for generating synthetic Web traces that exhibit the properties of temporal and spatial locality measured in the data.

Ages of detrital zircon from Archean-Paleoproterozoic sequences: Implications for Greenstone Belt setting and evolution of a Transamazonian foreland basin in Quadrilátero Ferrífero, southeast Brazil

Abstract: The Sao Francisco shield is one of the major cratonic units forming the backbone of the South American continent. The Quadrilatero Ferrifero area, in the south of the shield, is underlain by three major units: granitic-gneissic terrains with a minimum age of 2860 Ma; the Rio das Velhas greenstone belt, emplaced at 2772–2780 Ma; and the Minas Supergroup-Itacolomi Group Paleoproterozoic sedimentary sequences. The 207 Pb 206 Pb and UPb ages of more than 400 detrital zircons obtained by Laser ablation-ICPMS and isotope dilution lead to the following conclusions: (1) the Rio das Velhas greenstone belt contains exclusively cratogenic sediments and developed on, or proximal to, old, evolved continental crust with a minimum age of ca. 2.85 Ga; (2) the lower detrital sequence of the Minas Supergroup was supplied with sediments derived from both the granite-greenstone terrain and the surrounding older crust; (3) the upper unit of the Minas Supergroup (Sabara Formation) contains 2125 Ma zircon and the overlying Itacolomi Group contain zircons with minimum ages of ca. 2.06 Ga, identical to the ages of regional metamorphism. Together with other considerations, these ages lead to the novel proposal that the tectogenic sedimentation represented by these units occurred in a foreland basin of the Transamazonian orogen. Basin evolution was closely associated with the tectonic development of the orogen and uplift of basement complexes between 2125 Ma and 2030 Ma. The scarcity of 2.6-2.4 Ga zircons in the Proterozoic units of the Quadrilatero Ferrifero confirms previous results for the Sao Francisco shield and is symptomatic of the absence of magmatic-metamorphic activity in that period of time.

A belief network model for IR

Abstract: We introduce a belief network model for IR which is derived from probabilistic considerations over a clearly defined sample space. This model subsumes the classical models in IR and generalizes the inference network model of Turtle and Croft. Further, we show how to extend the model with information from other queries (which we call contexts) to yield improved retrieval performance.

Habitat and the evolution of social and reproductive behavior in callitrichidae.

Abstract: The numerous remarkable traits characterizing the ecology and behavior of callitrichids have inspired considerable research and discussion of the flexible mating system (cases of monogamy, polygyny, and polyandry), cooperative breeding, reproductive inhibition by dominant females, rapid reproductive rate, significance of dietary differences (gum feeding, frugivory, and insectivory), and demographics and social characteristics of the four genera, Cebuella, Callithrix, Saguinus, and Leontopithecus. The majority of functional explanations evaluate costs, benefits, and alternative strategies but do not address the critical selective forces that led to the behaviors in the first place. In this paper, it is argued that Callithrix and Saguinus evolved to occupy a small insectivore/frugivore niche in secondary growth forest patches (gaps arising from tree falls), and other successional forests and edge habitats; that Cebuella evolved to occupy a gum-feeding/insectivore niche in inundated forest; and that Leontopithecus is above all a small animal predator/frugivore and a mature forest genus. The keys to explanations concerning the evolution of the social and reproductive systems of these animals lie in an understanding of the resource base in these different habitats. Finally, it should be remembered that studies of callitrichids have in the main part been carried out in habitats highly altered by human activities (especially the Brazilian Atlantic forest, home to marmosets and lion tamarins) and are not the environments in which their social and breeding behavior evolved. © 1996 Wiley-Liss, Inc.

Critical Dynamics of the Contact Process with Quenched Disorder

Abstract: We study critical spreading in Monte Carlo simulations of the two-dimensional contact process (CP) with quenched disorder in the form of random dilution. In the pure model, spreading from a single particle at the critical point ${\ensuremath{\lambda}}_{c}$ follows power laws with the critical exponents of directed percolation. With disorder, critical spreading is logarithmic not power law. Below ${\ensuremath{\lambda}}_{c}$ there is a Griffiths phase in which the time dependence is governed by nonuniversal power laws. The effects of disorder are also apparent above ${\ensuremath{\lambda}}_{c}$, in the active phase, where the relaxation of the survival probability is algebraic, rather than exponential, as in the pure model. Our results support the conjecture by Bramson, Durrett, and Schonmann [Ann. Prob. 19, 960 (1991)], that in two or more dimensions the disordered CP has only a single phase transition.

Chemical composition, enzyme activity and effect of enzyme inactivation on flavor quality of green coconut water

Abstract: The chemical composition of green coconut water was determined. Both polyphenoloxidase and peroxidase were observed to be present and active in green coconut water. These enzymes showed optimum activity at pH 6.0 and 5.5 and at temperatures of 25 and 35C, respectively. Among chemical and physical treatments investigated, heating at 90C for 550 s and addition of ascorbic acid were, individually, the most efficient for enzyme inactivation. Addition of ascorbic acid did not affect sensory properties, however, heat treatment at 90C for longer than 100 s decreased flavor quality. Combinations of heat treatment with potassium metabisulfite, ascorbic acid or both additives did not affect flavor quality.

Effect of Saccharomyces boulardii against experimental oral infection with Salmonella typhimurium and Shigella flexneri in conventional and gnotobiotic mice.

Abstract: Saccharomyces boulardii was shown to be capable of inhibiting multiplication of enteropathogenic bacteria in vitro and is currently used for its anti-diarrhoea properties. We studied the capacity of this yeast to antagonize Salmonella typhimurium and Shigella flexneri in the intestinal tract of conventional or gnotobiotic NMRI mice. Conventional animals were given daily 10 mg doses of S. boulardii, whereas germ-free animals were given a single 10 mg dose. Both groups were challenged orally 5 d later with the pathogenic bacteria (10(8) or 10(2) viable cells, respectively). Control groups were treated with saline instead of S. boulardii. Mortality and/or histopathological data showed a protective effect against the pathogenic bacteria in yeast-treated mice. Saccharomyces boulardii colonized the digestive tract of gnotobiotic mice and the number of viable cells ranged around 10(10) g-1 of faeces. In experimental and control gnotobiotic animals, Salm. typhimurium and Sh. flexneri became rapidly established at a level of about 10(10) viable cells g-1 of faeces and remained at high levels until the animals died or were sacrificed. The protection against Salm. typhimurium and Sh. flexneri obtained in conventional and/or gnotobiotic mice previously associated with S. boulardii is not due to the reduction of the bacterial populations in the intestines.

Kinetoplast DNA signatures of Trypanosoma cruzi strains obtained directly from infected tissues.

Abstract: We report here a polymerase chain reaction (PCR)-based DNA profiling technique that permits Trypanosoma cruzi strain characterization by direct study of infected tissues This is based on application of a recently developed method of DNA fragment identification, called low-stringency single specific primer PCR (LSSP-PCR), to the study of the variable region of kinetoplast DNA (kDNA) minicircles from T cruzi Thus, we can translate the intraspecific polymorphism in the nucleotide sequence of kDNA minicircles into a specific and highly reproducible kDNA signature Comparison with the phenogram obtained by DNA fingerprinting analysis of a set of T cruzi strains showed good qualitative correlation between the degree of divergence of the LSSP-PCR profiles and the genetic distance between the strains kDNA signatures of heart tissue from acutely or chronically infected animals revealed perfect concordance with the patterns obtained from cultured parasites for the CL and Colombiana strains but not for the Y strain, which is known to be multiclonal However, the match was perfect for studies with two clones of the Y strain We take this as evidence that in some multiclonal strains there is heterogeneity among the clones in the degree of tropism for the heart tissue Finally, we showed that it is possible to obtain a T cruzi kDNA signature from the heart of a human patient with chronic Chagasic myocardiopathy kDNA signatures obtained by LSSP-PCR of sequences amplified from infected tissues constitute a new tool to study the molecular epidemiology of Chagas' disease

Comparison of the polymerase chain reaction with two classical parasitological methods for the diagnosis of Chagas disease in an endemic region of north-eastern Brazil.

Abstract: The sensitivities for Chagas disease diagnosis of haemoculture, xenodiagnosis, and polymerase chain reaction (PCR) amplification of Trypanosoma cruzi kinetoplast deoxyribonucleic acid (DNA) were compared for 101 patients living in an endemic region who were serologically positive for T. cruzi. PCR gave 60 positive results (59.4%), while a haemoculture was positive in 26 cases (25.7%) and xenodiagnosis in 36 (35.6%). Four xenodiagnosis-positive but PCR-negative patients were examined in detail. The discrepancies were not due to inhibition of the PCR reactions, as the samples were used successfully to amplify a human sequence. Nor were they due to a variation in kinetoplast DNA sequences, as the kinetoplast DNA of the parasite strains isolated from these patients after xenodiagnosis gave rise to the expected product when amplified by the PCR. We concluded that no parasite was present in the 5 mL of blood used for PCR, while probably a single T. cruzi cell was present in the blood volume ingested by the insects during xenodiagnosis (about 3 mL). This suggests that the total blood quantity collected for the PCR may be important with patients with low parasitaemia.

Helicobacter trogontum sp. nov., isolated from the rat intestine.

Abstract: A new Helicobacter species that colonizes the colonic mucosa of Wistar and Holtzman rats was isolated and characterized. This bacterium was gram negative, its cells were rod shaped with pointed ends, and its protoplasmic cylinder was entwined with periplasmic fibers. It was catalase and oxidase positive, rapidly hydrolyzed urea, and was susceptible to metronidazole and resistant to cephalothin and nalidixic acid. The new organism was microaerophilic and grew at 42°C, a feature that differentiates it from two other murine intestine colonizers, Helicobacter hepaticus and Helicobacter muridarum. On the basis of 16S rRNA sequence analysis data, the new organism was identified as a Helicobacter species that is most closely related to H. hepaticus. This bacterium is named Helicobacter trogontum. The type strain is strain LRB 8581 (= ATCC 700114).

Diet and vertical space use of three sympatric opossums in a brazilian atlantic forest reserve

Abstract: Few studies have investigated the ecological relationships between marsupials or their importance in community composition (Dickman 1984). The small size, nocturnal activity and arboreal habits of many species of didelphid marsupials present some difficulties in studying them. Vertical space use of vertebrates in tropical forests is difficult to examine, especially because of canopy height and great habitat complexity (sensu August 1983). However, this latter factor has a considerable importance in spatial separation of sympatric species, amplifying the possibilities of resource partitioning (Giller 1984). Previous studies on vertical space use of didelphid marsupials showed the importance of vertical stratification for this group (Charles-Dominique et al. 1981, Julien-Laferriere 1991, Malcolm 1991, Stallings 1989). Miles et al. (1981) stated that ecological segregation of Neotropical marsupials is not obviously determined by the species' diets, but is better related to spatial differentiation, which discards competition for food. However, these authors recognize the necessity to study the interactions between diet and space use for the comprehension of resource partitioning strategies. The purpose of this study was to examine the food habits and vertical space use in sympatric species of opossums in the Atlantic forest of Brazil. We hypo-

Chagasic patients lack CD28 expression on many of their circulating T lymphocytes.

Abstract: A balanced host-parasite interaction during Trypanosoma cruzi infection allows for the establishment of a chronic infection that can last for many years. T cells are a major element responsible for parasite specific and non-specific immunity during the complex immune response of the host. However, the subpopulations of T cells involved in the response, as well as the exact mechanisms through which those cells are activated or rendered unresponsive, are not well defined. It is known that co-stimulatory signals, some of which are mediated via CD28, are of critical importance in the triggering of appropriate T cell responses. In this study the authors performed double-labelling studies to determine the frequency of expression of CD28 by CD4+ and CD8+ T lymphocytes in the peripheral blood of patients with Chagas' disease. The results show that chagasic patients throughout the spectrum of chronic clinical forms of the infection have significantly higher mean frequencies of CD4+CD28- and CD8+CD28-T cells, as compared with non-chagasic individuals. Considering the importance of CD28 for T-cell activation, the observed down-regulation or loss of CD28 during infection may indicate a possible basis for observed immunoregulatory events or distinct stages of T-cell activation in this infection. Recent evidence from patients with HIV/AIDS indicates that CD28- cell populations are more likely to undergo apoptosis, and increased apoptosis has been observed in experimental Chagas disease.

Galling insects on neotropical species of Baccharis (Asteraceae)

Abstract: We report on the insect galls on neotropical species of Baccharis (Asteraceae) and describe new kinds of galls on Baccharis spp. of the cerrado and rupestrian fields of Brazil. Gall collections were made in several localities in Minas Gerais (Belo Horizonte, Caratinga, Lagoa Santa, Moeda, Ouro Preto, and Serra do Cipo). Baccharis may support the richest galling fauna of the neotropics (121 galling species on only 40 species of Baccharis). Nevertheless, gallers were not evenly distributed across host plant species. Four species of Baccharis alone supported 46% of the galling fauna. The most diverse fauna occurred on B. dracunculifolia (17 galls), B. concinna (15 galls), B. salicifolia (13 galls) and Baccharis sp. 1(11 galls). The most numerous galling taxa were, in decreasing order, Cecidomyiidae (Diptera), Lepidoptera (several Gelechiidae), Psyl- lidae (Homoptera), and Tephritidae (Diptera). The most diverse gall communities were on Baccharis species that inhabit harsh environments, such as B. concinna in...

Changes in the Baroreflex Control of Heart Rate Produced by Central Infusion of Selective Angiotensin Antagonists in Hypertensive Rats

Abstract: We have recently shown that an angiotensin-(1-7) [Ang-(1-7)] analogue, d-Ala 7 -Ang-(1-7) (A-779), is a selective Ang-(1-7) antagonist with no significant action on angiotensin type 1 or type 2 receptors. The availability of selective angiotensin antagonists prompted us to evaluate the role of Ang-(1-7) and Ang II on central modulation of the baroreflex control of heart rate in normotensive Wistar rats and spontaneously hypertensive rats (SHR). Blood pressure recording and reflex changes in heart rate elicited by intravenous bolus injections of phenylephrine were made before and within 1 and 3 hours of intracerebroventricular (ICV, lateral ventricle) infusion of saline (8 μL/h), A-779 (4 μg/h), DuP 753 (100 μg/h), or CGP 42112A (50 μg/h) in conscious rats. The slope of the relationship between changes in pulse interval versus changes in mean arterial pressure was used as an index of the baroreflex control of heart rate. ICV infusion of saline or any of the antagonists did not significantly change basal levels of mean arterial pressure and heart rate in SHR (170±6 mm Hg and 360±9 beats per minute, respectively; n=29) or Wistar rats (108±2 mm Hg and 377±6 beats per minute, respectively; n=29). Three hours of ICV infusion of A-779 markedly decreased baroreflex sensitivity in Wistar rats (from a basal slope of 1.09±0.3). In contrast, A-779 did not significantly alter the depressed baroreflex sensitivity of SHR (0.61±0.1). ICV infusion of DuP 753 produced a significant increase (60%) in baroreflex control of heart rate in both Wistar rats and SHR. Saline or CGP 42112A infusions did not significantly alter baroreflex control of heart rate. These results suggest that endogenous Ang II and Ang-(1-7) are differentially affecting central baroreflex modulation, acting probably through distinct receptor subtypes. Although the central Ang II inhibitory effect is mediated by the type 1 receptor subtype, the facilitatory effect of Ang-(1-7) might be mediated by a different, unidentified receptor.

Role of macrophage-derived cytokines in the induction and regulation of cell-mediated immunity to Toxoplasma gondii.

Abstract: In its intermediate hosts, infection with Taxoplasma gondii is characterized by an early phase when the tachyzoites (the rapidly multiplying stage of the parasite) can be found in different tissues accompanied by a mononuclear inflammatory reaction in small necrotic foci. Parasite multiplication during this stage of disease is most rapid in the liver, lymphoid tissues, lung, and brain. With development of immunity, the tachyzoites are cleared from the host tissues, the necrotic foci regenerate and bradyzoites (the dormant stage of T. gondii) form inside cysts mainly in the central nervous system without causing inflammatory reactions and necrosis (Frenkel 1988). This strong cell-mediated immunity (CMI) induced by T. gondii is maintained by Type 1 CD4+CD8- (Th1) and CD4-CD8+ T lymphocytes, as well as interferon (IFN)-γ and protects the host against rapid parasite growth and consequent pathology (Gazzinelli et al. 1993a). However, immunity is not able to eliminate the infection since the bradyzoites inside cysts can resist protective cell-mediated response. Nevertheless, spontaneous release of parasites from cysts occurs and may boost immunologic memory, thereby explaining the long-lasting immunity induced by this infection. In immunocompetent hosts, these released bradyzoites elicit a strong inflammatory response and are eventually destroyed by the immune system. However, in immunocompromised hosts, the bradyzoites released from cysts can transform into tachyzoites, resulting in rapid parasite proliferation, severe tissue damage, and a disease, toxoplasmic encephalitis, which, if left untreated, is usually fatal. In fact, T. gondii has emerged as the major opportunistic infection of parasitic origin in the current acquired immunodeficiency syndrome (AIDS) epidemic (Canning 1990; Kreiss and Castro 1990).

Carcinoid tumors frequently display genetic abnormalities involving chromosome 11.

Abstract: Carcinoid tumors are neuroendocrine neoplasms that are encountered either sporadically or as part of a familial syndrome, most notably-multiple endocrine neoplasia type 1 (MEN1). The MEN1 gene localizes to chromosome 11 (11q13) and presumably functions as a tumor suppressor gene. The molecular mechanisms underlying carcinoid tumor development and their clonal composition remain largely unknown. To establish whether carcinoid tumors develop via a mechanism similar to other MEN1-associated tumors, and indirectly determine their clonal composition, we analyzed 36 sporadically occurring carcinoid tumors with 16 chromosome 11 microsatellite markers, mostly from around the MEN1 region for loss of heterozygosity (LOH). Twenty one tumors (58%) displayed LOH of at least three markers, five lost almost an entire allele and the rest displayed a discontinuous pattern. Similar, but less extensive analysis was also carried out for 10 additional carcinoid tumors from Brazil, 6 of the 10 showed LOH with at least one marker. Overall, 36 of 46 tumors (78%) displayed LOH. In addition, 20 of 46 (43%) tumors exhibited a pattern of genomic instability. Thus, the majority of sporadically occurring carcinoid tumors are monoclonal whose tumorigenesis involves inactivation of a tumor suppressor gene on chromosome 11 and DNA mismatch repair genes mutations.

A new extinct primate among the Pleistocene megafauna of Bahia, Brazil.

Abstract: A nearly complete skeleton of a robust-bodied New World monkey that resembles living spider monkeys was recovered from undisturbed Pleistocene deposits in the Brazilian state of Bahia. The skeleton displays the highly specialized postcranial pattern typical of spider and woolly spider monkeys and shares cranial similarities to the spider monkey exclusively. It is generically distinct on the basis of its robustness (>20 kg) and on the shape of its braincase. This new genus indicates that New World monkeys nearly twice the size of those living today were part of the mammalian biomass of southern Amazonia in the late Pleistocene. The discovery of this specimen expands the known adaptive diversity of New World monkeys and demonstrates that they underwent body size expansion in the terminal Pleistocene, as did many other types of mammals.

Primates of the Atlantic Forest

Abstract: The Atlantic forest extends from the north-east of Brazil, state of Rio Grande do Norte, and including inland forests (brejos) in the state of Ceara, south along eastern Brazil, through the southernmost state, Rio Grande do Sul, into the northeastern tip of Argentina in the province of Misiones and between the Rios Parana, Uruguai and Iguacu. In contrast to the Amazon, the Atlantic forest (sensu strictu) is typically upland, stretching along the coastal mountain chain, known as the Serra do Mar in the south between the states of Santa Catarina and northern Rio de Janeiro where it is very close to the sea, and the Serra da Mantiqueira and eastern slopes of the Serra do Espinhaco inland. It comprises a complex of vegetation types, which could be referred to as the “Atlantic forest complex ”, and includes principally: 1) evergreen humid tropical forest, divided into a) cool, humid, montane forest (altitudes 800 to 1,500–1,700 m), and b) lower-montane forest (altitudes 300–800 m) with deeper soils, a marked dry season, and lower humidity (except in the valleys and near to the coast where they receive orographic rainfall); and 2) inland semideciduous or dry forests (Rizzini, 1979; Rizzini et al., 1988; Joly et al, 1991).

A complete skeleton of the giant South American primate Protopithecus

Abstract: A COMPLETE skeleton of a large-bodied New World monkey has been found in Pleistocene cave deposits in the Brazilian state of Bahia. It demonstrates an unprecedented combination of body size, locomotor and cranial morphology. Skeletal features indicate an animal of approximately 25 kg, more than twice the mass of any living South American monkey. We refer the specimen to Protopithecus brasiliensis Lund, 1838, a large Pleistocene primate originally represented by only a proximal femur and distal humerus1–4. The skeleton resembles species of two distinct New World monkey lineages. The cranium is modified for an enlarged vocal sac typical of living howler monkeys5–7, and the postcranium includes suspensory and brachiating components of locomotion as seen in living spider and woolly spider monkeys8. This skeleton confirms that adaptive diversity in neotropical primates was greater in the recent past, and that current interpretations of how their distinctive adaptations evolved should be revised.

Diet of the maned wolf, Chrysocyon brachyurus, in central Brazil

Abstract: Analysis of 105 scats of the maned wolf (Chrysocyon brachyurus) collected in central Brazil yielded 304 occurrences of food items of which fruits of Solanum lycocarpum, rodents, and birds accounted for 61.5%. By analysis of minimum number of individual animals, rodents and birds were 75% of a total of 156 prey. On the other hand, fruits of S. lycocarpum and armadillos (Dasypus spp.) were the bulk of the total estimated biomass consumption, yielding 63.7% in a total of 73.5 kg. Rodents were mostly captured during the dry season, while miscellaneous fruits were consumed mostly in the wet season. The consumption of S. lycocarpum fruits and armadillos was aseasonal. Small rodents were taken in about the ranks of abundance in the study area, but S. lycocarpum fruits were actively searched by maned wolves, for its occurrence is limited to secondary savanna. Prey and fruits typical of savanna (‘cerrado’) and grassland (‘campo’) were the bulk of species, occurrences, prey numbers, and biomass consumed. These findings reinforce the importance of conservation of cerrado and campo in central Brazil. Despite maned wolf being a vulnerable species, its feeding habits are opportunistic, and the main reasons for its decline are likely to be habitat destruction and human disturbance.

Sustained activation of phospholipase D via adenosine A3 receptors is associated with enhancement of antigen- and Ca(2+)-ionophore-induced secretion in a rat mast cell line.

Abstract: The adenosine analog, N-ethylcarboxamidoadenosine (NECA), causes transient activation of phospholipase C and an enhancement of antigen-induced secretion in a rat mast cell (RBL-2H3) line via adenosine A3-receptors (Ramkumar et al., J. Biol. Chem. 268:16887, 1993) by a mechanism that is inhibited by bacterial toxins and potentiated by dexamethasone (Ali et al., J. Biol. Chem. 265:745-753, 1990). Here we show that NECA synergizes the secretory response to Ca(2+)-ionophore as well as to antigen. The ability of NECA to synergize the secretory responses persisted for 10 to 20 min, long after the early phospholipase C-mediated reactions to NECA had subsided. NECA caused, however, a dose-dependent sustained activation of phospholipase D, as indicated by the formation of [3H]phosphatidic acid, or in the presence of 0.3% ethanol, [3H]phosphatidylethanol. This activation was associated with a sustained increase in diglycerides, in protein kinase C activity and in the phosphorylation of myosin light chains by protein kinase C. The generation of diglycerides was enhanced in dexamethasone-treated cells and suppressed in cells that had been treated with cholera toxin or pertussis toxin. Collectively, the studies suggested that the generation of diglycerides via phospholipase D and the associated activation of protein kinase C were, by themselves, insufficient signals for secretion in RBL-2H3 cells, but that these reactions synergized responses to stimulants such as antigen or A23187 that caused substantial increases in [Ca2+]i.

Distinguishing intrapopulational categories of plants by their insect faunas: galls on rabbitbrush.

Abstract: Within a population of rubber rabbitbrush, Chrysothamnus nauseosus, the subspecies C. nauseosus consimilis and C. nauseosus hololeucus, and a third unidentified group were better segregated by their insect galls, than by differences in plant morphology. This level of segregation was further increased when morphological measurements and counts of insect galls were analyzed simultaneously. We interpret this result to mean that plant morphology and insect distributions reflect two different, perhaps overlapping, portions of the host's genome. By using both sets of characters concurrently, rather than either set independently, we increased the portion of the plant's genome being sampled and increased the probability of detecting differences among host genotypes. Hence, knowledge of the distributions of insect galls may be useful for augmenting the level of separation, obtained by morphological measurements, among intrapopulational categories of plant genotypes. This application may be of greatest benefit when hybridization blurs morphological distinctions among plant taxa, when morphological traits are highly variable within genotypes, or when ephemeral morphological traits (e.g., leaves, flowers) are not available for measurements.