992 resultados para triangular plots
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ABSTRACT Male gladiator frogs of Hypsiboas Wagler, 1830 build nests on available substrate surrounding ponds and streams where female spawn eggs during the breeding period. Although gladiator frogs seem to show plasticity in the way they construct their nests, there is no study reporting if these species present preferences about microhabitat conditions for nest-building (mainly under subtropical climate). Predation pressure and environmental conditions have been considered major processes shaping the great diversity of reproductive strategies performed by amphibians, but microhabitat conditions should explain where to build a nest as well as how nest looks. This study aimed to test nest site selection for nest-building by Hypsiboas faber(Wied-Neuwied, 1821), determining which factors are related to nest site selection and nest features. The survey was conducted at margins of two permanent ponds in Southern Brazil. Habitat factors were evaluated in 18 plots with nest and 18 plots in the surrounding without nest (control), describing vegetation structure and heterogeneity, and substrate characteristics. Water temperature was measured inside the nest and in its adjacency. Nest features assessed were area, depth and temperature. Habitat characteristics differed between plots with and without nest. Microhabitat selected for nest-building was characterized by great vegetation cover and height, as well as shallower water and lower cover of organic matter in suspension than in plots without nest. Differences between temperature inside nest and in its adjacency were not observed. No relationship between nest features and habitat descriptors was evidenced. Results revealed that Hypsiboas faber does not build nests anywhere. Males seem to prefer more protected habitats, probably avoiding predation, invasion of conspecific males and inclement weather. Lack of differences between temperature inside- and outside-nest suggest that nest do not improve this condition for eggs and tadpole development. Nest architecture was not related to habitat characteristics, which may be determined by other factors, as nest checking by females before amplexus. Nest site selection should increase offspring survival as well the breeding success of Hypsiboas faber.
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I - No Bradypus tridactylus foram encontrados 2 ganglios cervicaes e 13 thoracicos. II - O sympathico abdominal é constitutido inicialmente por um ganglio triangular que representa a fuzão do primeiro ganglio catenario lombar e do ganglio semi-lunar classico. Nota-se tambem na cadeia lombar uma massa ganglionar unica. III - A cadeia pelviana é representada por 7 ganglios, gradativamente reduzidos de tamanho. IV - No Bradypus tridactylus os dois ultimos ganglios pelvianos direito e esquerdo se reunem por uma anastomose transversal. V - No Bradypus tridactylus foi encontrada em dois exemplares origem thoracica rudimentar de um unico esplanchnico em cada lado; nos demais exemplares notou-se ausencia de individualisação anatomica dos nervos esplanchnicos. VI - No Bradypus tridactylus além de um ganglio triangular situado latero-ventralmente á aorta e caudalmente á emergencia da arteria celiaca, encontrou-se um ganglio aortico renal e um ganglio hypogastrico. VII - No Bradypus tridactylus verificou-se a existencia dos nervos esplanchnicos pelvianos de Delmas e do plexo inter-iliaco ou pré-sacro.
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Hyla claresignata Lutz & Lutz, 1939, is a large species apparently not closely allied to the other known Brazilian hylas. It is characterized by the very small tympanum; the head is short and the snout rounded; the legs are long, the hands and feet unusually large, the latter extensively webbbed. The specific name is derived from the insular, irregular, or roughly triangular, dark spots, with a light halo, found mostly in the dorso-lateral region and on the legs. It belongs to the rain-forest fauna of the Marítime Range. The adult is a bromeliad-dweller and the tadpole rhyacophilous. DESCRIPTION. Vomerine teeth in two separate, oblique, groups, behind the large choanae, parallel to the posterior half of their inner border. Tongue entire, short, very broad and hardly free behind. Snout short, rounded, with distinct canthus rostralis and gradually sloping loreal region. Eye very large and prominent, its horizontal diameter almost equal to the distance between its anterior corner and the tip of the snout. Tympanum very small, less than one third of the diameter of the eye, but distinct, partly covered by a short, heavy ridge. Lateral fingers less than one third webbed; fourth finger slightly longer than the second, just reaching the base of the disk of the third; subarticular tubercles well developed; an angular pollex rudiment, more noticeable in the males. Toes almost completely webbed, the edge of the web inserted at the base of the disk on the third and the fifth; an inner metatarsal tubercle. Skin smooth above, granular beneath, on the throat minutely so. No dermal appendage on the hell. Habit robust, head broader than long, body rather heavy, slightly narrowed in the postaxillary region. Legs long, the tibiotarsal articulation reaching beyond the tip of the snout when adpressed. Type (female): 61 mm. (Fig. 1.) DIAGNOSIS of TADPOLE (by G. Orton). "A large specialized, mountain-stream tadpole, with wide head an elongated, flattened snout, greatly enlarged lips and high tooth formula. Eyes dorsal. Spiracle sinistral, projecting, situated far back on side. Anus dextral. Tooth formula 8/12 to 9/14 in fully grown larvae. Tail with a prominent, vertical dark band across musculature and fins; a second concentration of dark pigment near tip of tail, may or may not form a similar but narrower band. Maximum known total length: 60mm.; head and body length 25mm. (Figs. 6 e 7). For further details see Lutz & Lutz, 1939 and Lutz B. & Orton G. 1946.
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Descreveu-se o mecanismo saltatório do Halticíneo Homophoeta sexnotata. O aparelho se encontra localizado no fêmur e consta de uma placa cuticular arqueada, em forma de S, e, de uma placa menor, triangular. Tôdas as placas representam modificações dos tendões do abdutor e flexor da tíbia e mantêm ainda ligação com os mesmos. Pela colaboração das duas placas acumula-se uma forte tensão no tendão do abdutor (músculo saltatório). A tíbia não se pode esticar pois a placa trinagular fica presa numa cavidade da parede do fêmur. Apenas no momento da maior contração do abdutor a placa curvada força a saida da placa triangular do seu ponto de apóio. Desta maneira o forte músculo abdutor da tíbia exerce tôda a sua força, de uma só vez, sôbre a articulação da mesma, dando ao Coleóptero um forte impulso para saltar. O órgão é encontrado em grande número dos Halticíneos. em homenagem ao grande entomólogo brasileiro PROF. DR. ANGELO DA COSTA LIMA dei ao órgão o nome de ÓRGÂO DE COSTA LIMA.
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The first case of Kala-azar in Colombia was discovered in Soledad, S. Vicente do Chucuri, Dept. Santander, by Gast-Galvis who viscerotomized a three year old girl deceased in December, 1943. In 1944, fifty-three Phlebotominae were collected in the chicken pen of the girl's house, two new species included. Mangabeira helped by A. Gast Galvis, Juan Antonio Montoya and E. Osorno Mesa, collected some Phlebotomus in that country. The geographical distribution of the species of Phlebotomus collected in Colombia (P. abonnenci, P. camposi, P. columbianus, P. dubitans, P. gasti, P. montoyai, P. saulensis, P. serranus, P. triramulus) and two species of Brumptomyia (B. beaupertuyi and b mesari), are included. our description of the male P. columbianus is based on some specimens found in association with females. However, doubts exist about such association of sexes. There is no correspondence between the length of the spicules and the ducts of spermathecae. Besides, the specimens were not obtained by raising. The following new species are described and compared with previously known ones: a) Phlebotomus gasti sp. n. differs from the other species by a protruding tubercle in the gubernaculum. It has also fewer setae in the tuft of the basistyle, a different length of the inferior gonapophyses, and a differently shaped clasper. b) Phlebotomus dubitans sp. n. differs from P. walkeri and P. deanei (according to personal information from O. Theodor, who examined the types, they are identical to P. williamsi and P. sericeus respectively), mainly because these species have the inferior gonapophyses larger than the basistyle and fewer setae in the basistyle. P. evandroi is separated by the shape of the claspers and by the tuft of setae of the basistyle. P. marajoensis is the closest relative to P. dubitans. There is a possibility of their being synonymous. On the other hand, they can be differentiated by the existence of three extra distal spines in P. marajoensis. There is also a difference in their palpal indexes: for marajoensis I - II - IV - III - V, and for dubitans I - IV (III - II) - V. We notice, too, that the inferior gonapophyses in P. marajoensis is a little shorter. P. marajoensis has a long seta in the basistyle (clearly shown in the original drawing), not found in the new species. c) Phlebotomus montoyai sp. n.: The closest relatives are P. noguchii, P. peruensis, P. pescei, P. quinquifer and P. rickardi. They differ from the new species by the number and length of the setae of the basistyle tuft which are more numerous and longer in the new species. The shapes of their claspers are also different. Other differences are: the basal portion of the basistyle in P. noguchii is very wide (in montoyai it is narrower); the intermediate spine of the dististyle is located on a protruding tubercle ( in the new species there is hardly a tubercle); the spicules are long, and the inferior gonapophyses is longer than the basistyle. P. quinquifer and P. rickardi have a shorter dististyle and narrower wings, with different venation. The main difference, however lies, in the M4, which ends almost at the level of the junction of M1 with M2 (in P. montoyai the M4 ends far behind). In P. peruensis and P. pescei the intermediary spine of the dististyle is closer to the distal spine than to the basal one, whereas in the new species it is situated between the two pairs. Their inferior gonapophyses is longer than the basistyle. d) Brumptomyia mesai sp. n. - Closest relatives are: B. hamatus, B. pentacanthus, B. beaupertuyi which are easily separated from the new species because the tufts of their basistyle have thin and differently shaped hairs. Also their claspers are shaped differently. B. avellari is also easily recognized on account of the twisted aspect of its clasper and because the basal tuft of the basistyle has few setae, B. brumpti tuft of setae arise directly from the basistyle; these setae are stronger than those of the new species. It has 8 blade-like setae located on the inner surface of the distal half, whereas the new species has only six setae. In B. brumpti, there are three median and two terminal spines in the dististyle; in the new species, there are two median and two terminal spines and one between them, which is closer to the two median spines. The comparison with B. galindoi is based in a specimen determined by Fairchild and deposited in the entomological collection of the "Faculdade de Higiene e Saúde Pública da Universidade de S. Paulo". The genitalia of the new species is much shorter, in galindoi the inferior gonapophyses is 0,8 mm long whereas in B. mesai it hardly reaches 0,6 mm. The shape of the clasper and the distribution of its setae are different. The sub-median lamellae, besides being longer in B. galindoi are also longer in comparison with the other parts of the genitalia. The gubernaculum of the new species is longer, thinner, and more pointed; in B. galindoi it is shorter and triangular. In the drawing published by Fairchild and Hertig 91947), the basistyle shows 8 blade-like setae on the distal half, whereas in the new species only six are found.
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Estudi elaborat a partir d’una estada a l’Associação para o Desenvolvimento da Aerodinânica Industrial (ADAI) de la Universitat de Coimbra, Portugal, entre març i juliol de 2006. Aquesta disposa d'un laboratori d'assaigs i té medis suficients per a cremar de manera controlada parcel•les prèviament delimitades en terreny forestal. Això permet observar el fenomen dels incendis forestals a dues escales de treball diferents. L’objectiu ha estat l’obtenció de dades experimentals sobre la propagació de fronts de flames que avancen sobre combustible tractat amb retardants sota l’efecte del pendent o el vent. S’ha participat en proves experimentals de camp i se n’han realitzat dues en instal•lacions de laboratori en què l’efecte del pendent o de la velocitat del vent podia ser variat. Degut a l’elevat nombre de variables que entren en joc l’anàlisi acurada de les dades encara està en procés.
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Estudi elaborat a partir d’una estada a l'Imperial College of London, Gran Bretanya, entre setembre i desembre 2006. Disposar d'una geometria bona i ben definida és essencial per a poder resoldre eficientment molts dels models computacionals i poder obtenir uns resultats comparables a la realitat del problema. La reconstrucció d'imatges mèdiques permet transformar les imatges obtingudes amb tècniques de captació a geometries en formats de dades numèriques . En aquest text s'explica de forma qualitativa les diverses etapes que formen el procés de reconstrucció d'imatges mèdiques fins a finalment obtenir una malla triangular per a poder‐la processar en els algoritmes de càlcul. Aquest procés s'inicia a l'escàner MRI de The Royal Brompton Hospital de Londres del que s'obtenen imatges per a després poder‐les processar amb les eines CONGEN10 i SURFGEN per a un entorn MATLAB. Aquestes eines les han desenvolupat investigadors del Bioflow group del departament d'enginyeria aeronàutica del Imperial College of London i en l'ultim apartat del text es comenta un exemple d'una artèria que entra com a imatge mèdica i surt com a malla triangular processable amb qualsevol programari o algoritme que treballi amb malles.
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Un dels principals problemes de la interacció dels robots autònoms és el coneixement de l'escena. El reconeixement és fonamental per a solucionar aquest problema i permetre als robots interactuar en un escenari no controlat. En aquest document presentem una aplicació pràctica de la captura d'objectes, de la normalització i de la classificació de senyals triangulars i circulars. El sistema s'introdueix en el robot Aibo de Sony per a millorar-ne la interacció. La metodologia presentada s'ha comprobat en simulacions i problemes de categorització reals, com ara la classificació de senyals de trànsit, amb resultats molt prometedors.
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A description of Physa marmorata Guilding, 1828, based on material collected at its type-locality, the Caribbean island of Saint Vincent, is presented. The shell is thin, horn-colored, surface very glossy, diaphanous. Spire acute, elevated; protoconch distinct, rounded-conical, reddish-brown; five not shouldered, broadly convex whorls with subobsolete spiral lines and thin growth lines. Aperture elongated, 1.4-2.0 times as long as the remaining shell length, narrow obovate-lunate; upper half acute-angled,lower half oval,narrowly rounded at the base, outer lip sharp, inner lip completely closing the umbilical region; a very distinct callus on the parietal wall; columellar lip with a low ridge gradually merging into the callus. ratios: shell width/shell length = 0.44 - 0.52 (mean 0.47); spire length /shell lenght = 0.33-0.41 (mean 0.39); aperture length/shell lenght = 0.59-0.67 (mean 0.62). Oral lappets laterally mucronate, foot spatulate with deeply pigmented acuminate tail. Mantle reflection with 6-10 short triangular dentations covering nearly half the right surface of the body whorl, and 4-6 covering a part of the ventral wall. Body surface with tiny dots of greenish-yellow pigment besides melanin. Renal tube tightly folded in toa zigzag course. Ovotestis diverticula acinous, laterally pressed against each other around a collecting canal. Ovispermiduct with well-developed seminal vesicle. oviduct highly convoluted, merging into a less convoluted nidamental gland which narrows to a funnel-shaped uterus and a short vagina. Spermathecal body oblong, more or less constricted in the middle and somewhat curved; spermathecal duct uniformly narrow, a little longer than be body. About 20 prostatic diverticula, simple, bifurcate or divided into a few short branches, distalmost ones assembled into a cluster. Penis long, nearly uniformly narrow; penial canal with lateral opening about the junction of its middle and lower thirds. Penial sheath with a bulbous terminal expasion the tip of which isinserted into the caudal end of the prepuce. Prepuce shouldered, much wider than the narrow portion of the penial sheath. Penial sheath/prepuce ratio about 2.08 (1.45-2.75). The main extrinsic muscles of the penial complex are a retractor, with a branch attached to the bulb, and another to the caudal end of the penial sheath; and a protractor, with a branch attached to the shoulder of the prepuce and adjoining area of the penial sheath, and another to the caudal end of the penial sheath. Egg capsule C-shaped, with 10-30 elliptical eggs (snails 10mm long) measuring about 1.10 mm (0.90-1.32) through the long axis and surrounded by an inner and an outer lamellate membranes. Jaw a simple obtusely V-shaped plate. radula will be described separately.
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We reviewed our surgery registry, to identify predictive risk factors for operative results, and to analyse the long-term survival outcome in octogenarians operated for primary isolated aortic valve replacement (AVR). A total of 124 consecutive octogenarians underwent open AVR from January 1990 to December 2005. Combined procedures and redo surgery were excluded. Selected variables were studied as risk factors for hospital mortality and early neurological events. A follow-up (FU; mean FU time: 77 months) was obtained (90% complete), and Kaplan-Meier plots were used to determine survival rates. The mean age was 82+/-2.2 (range: 80-90 years; 63% females). Of the group, four patients (3%) required urgent procedures, 10 (8%) had a previous myocardial infarction, six (5%) had a previous coronary angioplasty and stenting, 13 patients (10%) suffered from angina and 59 (48%) were in the New York Heart Association (NYHA) class III-IV. We identified 114 (92%) degenerative stenosis, six (5%) post-rheumatic stenosis and four (3%) active endocarditis. The predicted mortality calculated by logistic European System for Cardiac Operative Risk Evaluation (EuroSCORE) was 12.6+/-5.7%, and the observed hospital mortality was 5.6%. Causes of death included severe cardiac failure (four patients), multi-organ failure (two) and sepsis (one). Complications were transitory neurological events in three patients (2%), short-term haemodialysis in three (2%), atrial fibrillation in 60 (48%) and six patients were re-operated for bleeding. Atrio-ventricular block, myocardial infarction or permanent stroke was not detected. The age at surgery and the postoperative renal failure were predictors for hospital mortality (p value <0.05), whereas we did not find predictors for neurological events. The mean FU time was 77 months (6.5 years) and the mean age of surviving patients was 87+/-4 years (81-95 years). The actuarial survival estimates at 5 and 10 years were 88% and 50%, respectively. Our experience shows good short-term results after primary isolated standard AVR in patients more than 80 years of age. The FU suggests that aortic valve surgery in octogenarians guarantees satisfactory long-term survival rates and a good quality of life, free from cardiac re-operations. In the era of catheter-based aortic valve implantation, open-heart surgery for AVR remains the standard of care for healthy octogenarians.
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A description of Physa cubensis Pfeiffer, 1839, based on 15 speciments collected in Havana, Cuba, is presented. The shell, measuring 9.0 x 4,8mm to 12.3 x 6.4mm, is ovate-oblong, thin, diaphanous, horncolored, shining. Spire elevated, broadly conical; protoconch distinct, roundish, reddish-brown. About five moderately shouldered, roundly convex whorls, penultimate whorl expanded; spiral striation subobsolete; growth line faint on the intermediate whorls, clearly visible on the body whorl, crowded here and there. Suture well impressed. Aperture elongated 2.05 - 2.67 (mean 2.27) times as long as the remaining length of the shell, narrow obovulate-lunate; upper half acute-angled, lower half oval, narrowly rounded at the base; outer lip sharp, inner lip completely closing the umbilical region; a thick callus on the parietal wall; columellar plait well marked. Ratios: shell width/shell length - 0.52-0.61 (mean 0.55); spire length/shell length = 0.27 - 0.33 (mean 0.31); aperture length/shell length = 0.67 - 0.73 (mean 0.69). Oral lappets laterally mucronate; foot spatulate with acuminate tail. Mantle relection with 6 - 8 short triangular dentations in the right lobe (columellar side) and 4 - 6 in the left lobe (near the pneumostome). Renal tube tightly folded into a zigzag course. Ovotestis, ovispermiduct, seminal vesicle, oviduct, nidamental gland, uterus and vagina as in Physa marmorata (see Paraense, 1986, Mem. Inst. Oswaldo Cruz, 81: 459-469). Spermathecal body egg-shaped or pear-shaped; spermathecal ducta uniformly narrow with expanded base, a little longer than the body. Spermiduct, prostate and vas deferens as in P. marmorata (Paraense, loc. cit.). Penis wide proximally, narrowing gradually apicad; penial canal with subterminal outlet. Penial sheath following the width of the penis and ending up by a bulbous expansion somewhat narrower than the proximal portion. Penaial sheath/prepuce ration = 1,25 - 1,83 (mean 1.49). Prepuce much wider than the bulb of the penial shealth, moderately shouldered owing to the intromission of the bulb, and with a large gland in one side of its proximal half occupating about a third of its length. Extrinsic muscles of the penial complex as in P. marmorata. Jaw a simple obtusely V-shaped plate. Radula to be described separetely.
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Introduction: Several scores are commonly used to evaluate patients' postoperative satisfaction after lateral ankle ligament repair, including: AOFAS, FAAM, CAIT and CAIS. Comparing published studies in the literature is difficult, as the same patient can have markedly different results depending on which scoring system is used. The current study aims to address this gap in the literature by developing a system to compare these tests, to allow better analysis and comparison of published studies. Patients and methods: This is a retrospective cohort study of 47 patients following lateral ankle ligament repair using a modified Broström-Gould technique. All patients were operated between 2005 and 2010 by a single surgeon and followed the same post operative rehabilitation protocol. Six patients were excluded from the study because of concomitant surgery. Patients were assessed by an independent observer. We used the Pearson correlation coefficient to analyse the concordance of the scores, as well as scatter plots to assess the linear relationship between them. Results: A linear distribution between the scores was found when the results were analysed using scatter plots. We were thus able to use the Pearson correlation coefficient to evaluate the relationship between each of the different postoperative scores. The correlation was found to be above 0.5 in all cases except for the comparison between the CAIT and the FAAM for the activities of daily living (0.39). We were, therefore, able to compare the results obtained and assess the relative concordance of the scoring systems. The results showed that the more specific the scale is, the worst the score is and inversely. So the CAIT and the CAIS appeared to be more severe than the AOFAS and the FAAM measuring the activities of daily living. The sports subscale of the FAAM demonstrated intermediate results. Conclusion: This study outlines a system to compare different postoperative scores commonly used to evaluate outcome after ankle stabilization surgery. The impact of this study is that it makes comparison of published studies easier, even though they use a variety of different clinical scores, thus facilitating better outcome analysis of operative techniques.
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Els incendis forestals són una pertorbació amb un paper decisiu en l’estructura i dinàmica dels ecosistemes mediterranis. La majoria de les seves espècies vegetals presenten mecanismes de resposta al foc, com la germinació de llavors i la rebrotada d’individus cremats. Les masses forestals regenerades a partir de rebrots assoleixen densitats massa altes i una baixa producció, i, per tant, és fonamental dur a terme una gestió mitjançant tractaments silvícoles. El principal objectiu d’aquest projecte és quantificar l’efecte de la selecció de rebrots i la selecció de rebrots més la desbrossada sobre el creixement de l’Arbutus unedo. S’han estudiat 12 parcelles en regeneració després dels incendis de 1985, 1986 i 1994 al terme municipal d’Esparreguera. Els resultats mostren que els dos tractaments afavoreixen de la mateixa manera el creixement dels peus d’Arbutus unedo, a causa de la disminució de la competència intraespecífica i interespecífica. La desbrossada (a nivell de parcella, no d’individu), no obstant, provoca un increment probablement perjudicial de l’alçada dels rebrots, per la major disponibilitat de llum. Per tal de proposar un model de gestió forestal, s’ha realitzat una anàlisi multicriterial dels diferents escenaris, on s’han considerat altres criteris, com són el model de combustible, la possibilitat de pastura i el cost econòmic. L’alternativa preferida en els boscos d’Arbutus unedo és la selecció de rebrots i la desbrossada.
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BACKGROUND AND PURPOSE: Surgical clipping of unruptured intracranial aneurysms (UIAs) has recently been challenged by the emergence of endovascular treatment. We performed an updated systematic review and meta-analysis on the surgical treatment of UIAs, in an attempt to determine the aneurysm occlusion rates and safety of surgery in the modern era. METHODS: A detailed protocol was developed prior to conducting the review according to the Cochrane Collaboration guidelines. Electronic databases spanning January 1990-April 2011 were searched, complemented by hand searching. Heterogeneity was assessed using I(2), and publication bias with funnel plots. Surgical mortality and morbidity were analysed with weighted random effect models. RESULTS: 60 studies with 9845 patients harbouring 10 845 aneurysms were included. Mortality occurred in 157 patients (1.7%; 99% CI 0.9% to 3.0%; I(2)=82%). Unfavourable outcomes, including death, occurred in 692 patients (6.7%; 99% CI 4.9% to 9.0%; I(2)=85%). Morbidity rates were significantly greater in higher quality studies, and with large or posterior circulation aneurysms. Reported morbidity rates decreased over time. Studies were generally of poor quality; funnel plots showed heterogeneous results and publication bias, and data on aneurysm occlusion rates were scant. CONCLUSIONS: In studies published between 1990 and 2011, clipping of UIAs was associated with 1.7% mortality and 6.7% overall morbidity. The reputed durability of clipping has not been rigorously documented. Due to the quality of the included studies, the available literature cannot properly guide clinical decisions.
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Trioecy is an uncommon sexual system in which males, females, and hermaphrodites co-occur as three clearly different gender classes. The evolutionary stability of trioecy is unclear, but would depend on factors such as hermaphroditic sex allocation and rates of outcrossing vs. selfing. Here, trioecious populations of Mercurialis annua are described for the first time. We examined the frequencies of females, males and hermaphrodites across ten natural populations and evaluated the association between the frequency of females and plant densities. Previous studies have shown that selfing rates in this species are density-dependent and are reduced in the presence of males, which produce substantially more pollen than hermaphrodites. Accordingly, we examined the evolutionary stability of trioecy using an experiment in which we (a) indirectly manipulated selfing rates by altering plant densities and the frequency of males in a fully factorial manner across 20 experimental plots and (b) examined the effect of these manipulations on the frequency of the three sex phenotypes in the next generation of plants. In the parental generation, we measured the seed and pollen allocations of hermaphrodites and compared them with allocations by unisexual plants. In natural populations, females occurred at higher frequencies in denser patches, a finding consistent with our expectations. Under our experimental conditions, however, no combination of plant densities and male frequencies was associated with increased frequencies of females. Our results suggest that the factors that regulate female frequencies in trioecious populations of M. annua are independent of those regulating male frequencies (density), and that the stable co-existence of all three sex phenotypes within populations is unlikely.