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Life History Characteristics (life + history_characteristic)
Selected AbstractsPhenotypic Plasticity of Life History Characteristics: Quantitative Analysis of Delayed Reproduction of Green Foxtail (Setaria viridis) in the Songnen Plain of ChinaJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2008Hai-Yan Li Abstract Green foxtail (Setaria viridis L.) is a common weed species in temperate regions. Research on the effect of delayed reproduction on the phenotypic plasticity and regularity of the vegetative and reproductive growth is of vital significance for understanding population regulation and control of the weed in the growing season. Green foxtail seeds were sown every 10 days from 25 June to 24 August of 2004. The growth and production metrics were measured via harvesting tufts and statistical analysis was carried out. The results showed that the reproductive tillers, seed number, seed biomass and one thousand-seed weight of plants at the first sowing (25 June) approximately increased 28.8, 7 827.0, 1 104.0 and 12.3 times compared with that at the last sowing (24 August), respectively. Total tillers, reproductive tillers and height increased linearly as the reproductive period delayed, however, biomass increased exponentially. Quadratic equations best explained the relationships between the delayed reproductive period and seed number, inflorescence length, one thousand-seed weight, seed biomass. Based on the quantity and quality of seed production, weeding young seedlings emerging before July can be the most effective weed-control strategy in the Songnen Plain. [source] Life history characteristics of an invasive cyprinid fish (Carassius gibelio) in Chimaditis Lake (northern Greece)JOURNAL OF APPLIED ICHTHYOLOGY, Issue 2 2008I. D. Leonardos Summary The life history characteristics of an invasive cyprinid fish, the Prussian carp (Carassius gibelio) were examined in Lake Chimaditis (northern Greece). The population is dominated by females that are able to reproduce gynogenetically. Fish samples were collected using trammel nets from August 2004 to July 2005. Their total length (TL) ranged between 21.9 and 37.0 cm. The length,weight relationship was W = 0.0336TL2.81 (r2 = 0.92, n = 600) and the mean Fulton condition factor exhibited monthly variation from 0.172 (May) to 0.186 (August). According to the annual growth marks present, the lifespan of the Prussian carp in Lake Chimaditis is 6 years. The growth parameters were estimated as L, = 34.46 cm, K = 0.297 year,1, t0 = ,1.994 year. Absolute fecundity (FA) ranged between 26 000 and 176 600 oocytes (mean = 66990) and relative fecundity between 78 and 251 oocytes per gram of total weight (mean = 158). Absolute fecundity increased exponentially with length (FA = 0.286 × TL3.66, r2 = 0.66) and weight (FA = 17.93 × W1.36, r2 = 0.73) of the fish. [source] Stoichiometric relations in an ant-treehopper mutualismECOLOGY LETTERS, Issue 11 2004Adam D. Kay Abstract Carbon : nitrogen : phosphorus (C : N : P) stoichiometry can underlie physiological and life history characteristics that shape ecological interactions. Despite its potential importance, there is much to learn about the causes and consequences of stoichiometric variation in terrestrial consumers. Here we show that treehoppers (Publilia modesta) tended by ants (Formica obscuripes) contained lower N concentrations than treehoppers on plants from which ants were excluded. Ant presence also affected nutrient concentrations in host plants: on plants with ants, leaves contained uniformly low concentrations of N; on plants without ants, N concentrations were low only in the few leaves fed upon by treehoppers at the time of collection. We suggest treehopper feeding reduces leaf nutrient levels and ants positively affect treehopper abundance, producing a top,down effect on plant quality. Determining the causes of these stoichiometric changes should help elucidate factors guiding the dynamics of conditional mutualisms between ants and homopterans. [source] The life history of Salicaceae living in the active zone of floodplainsFRESHWATER BIOLOGY, Issue 4 2002S. KARRENBERG 1.,Exposed riverine sediments are difficult substrata for seedling establishment because of extremes in the microclimate, poor soil conditions and frequent habitat turnover. Various species of willows and poplars (Salicaceae) appear to be particularly successful in colonising such sediments and are often dominant in floodplain habitats throughout the northern temperate zone. 2.,In many Salicaceae regeneration seems to be adapted to regular disturbance by flooding. Efficient seed dispersal is achieved by the production of abundant seed in spring and early summer, which are dispersed by air and water. Seeds are short-lived and germinate immediately on moist surfaces. Seedling establishment is only possible if these surfaces stay moist and undisturbed for a sufficient period of time. 3.,Larger plants of Salicaceae have exceptional mechanical properties, such as high bending stability, which enable them to withstand moderate floods. If uprooted, washed away or fragmented by more powerful floods these plants re-sprout vigorously. 4.,While these life characteristics can be interpreted as adaptations to the floodplain environment, they may also cause a high genetic variability in populations of Salicaceae and predispose Salicaceae to hybridization. Thus, a feed back between adaptive life history characteristics and the evolutionary process is proposed. [source] Social biology of rodentsINTEGRATIVE ZOOLOGY (ELECTRONIC), Issue 4 2007Jerry O. WOLFF Abstract Herein, I summarize some basic components of rodent social biology. The material in this paper is summarized and condensed from a recent book "Rodent Societies: An Ecological and Evolutionary Perspective" edited by J. O. Wolff and P. W. Sherman (2007). I describe the four basic spacing patterns and illustrate how female territoriality is a function of offspring defense and male mating tactics are a function of female defensibility. The vulnerability of young to infanticide shapes female spacing and mating behavior. Food does not appear to be a defensible resource for rodents, except for those species that larder hoard nonperishable items such as seeds. Philopatry and the formation of kin groups result in genetic sub-structuring of the population, which in turn affects effective population size and genetic diversity. Dispersal is male biased and typically involves emigration from the maternal site to avoid female relatives and to seek unrelated mates. Scent marking is a major form of communication and is used in reproductive competition and to assess prospective mates, but it is also eavesdropped by predators to locate prey. Females do not appear to alter the sex ratio of litters in response to maternal condition but among arvicoline rodents daughters appear to be favored in spring and sons in autumn. Rodents are relatively monomorphic; however, females tend to be larger than males in the smallest species and smaller in the larger species. Predation risk results from an interaction among foraging time and vulnerability and in turn affects behavioral and life history characteristics. [source] Evolution of avian clutch size along latitudinal gradients: do seasonality, nest predation or breeding season length matter?JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2010E. M. GRIEBELER Abstract Birds display a latitudinal gradient in clutch size with smaller clutches in the tropics and larger in the temperate region. Three factors have been proposed to affect this pattern: seasonality of resources (SR), nest predation and length of the breeding season (LBS). Here, we test the importance of these factors by modelling clutch size evolution within bird populations under different environmental settings. We use an individual-based ecogenetic simulation model that combines principles from population ecology and life history theory. Results suggest that increasing SR from the tropics to the poles by itself or in combination with a decreasing predation rate and LBS can generate the latitudinal gradient in clutch size. Annual fecundity increases and annual adult survival rate decreases from the tropics to the poles. We further show that the annual number of breeding attempts that (together with clutch size) determines total annual egg production is an important trait to understand latitudinal patterns in these life history characteristics. Field experiments that manipulate environmental factors have to record effects not only on clutch size, but also on annual number of breeding attempts. We use our model to predict the outcome of such experiments under different environmental settings. [source] Nesting behavior and breeding success of HoatzinsJOURNAL OF FIELD ORNITHOLOGY, Issue 4 2007Antje Müllner ABSTRACT Hoatzins (Opisthocomus hoazin) are the only member of the family Opisthocomidae and are found only in forests in the Amazon and Orinoco river basin of South America. Although locally common in riparian habitats, information about their natural history is based almost exclusively on observations from gallery forests in the "llanos" (savannahs) of Venezuela. We investigated the nesting activities of Hoatzins in a primary rainforest in Amazonian Ecuador from 1995 to 2000. At our study site, Hoatzins live and breed in the inundated forests that surround lakes and river channels. Egg laying occurred from February to July and from September to November, but always peaked in April, May, and June. The mean clutch size was 2.4 ± 1.1 eggs (N= 291; range = 1,7), but 51% of all clutches contained two eggs. The mean duration of the incubation period was 32 ± 1.5 d (N= 20) and, overall, 17% of Hoatzin nests fledged at least one young. The main cause of nest failure was predation, with birds and snakes being the most frequent predators. Hoatzin reproduction was closely linked to the rainy season, and such timing may be influenced by increased food availability (high water levels cause leaf fall and the subsequent growth of new leaves coincides with the beginning of the feeding period of the young) and reduced risk of nest predation by mammalian predators when water levels are high. Our results indicate that the breeding biology of Hoatzins in tropical rainforest habitat, including small clutch sizes and low annual reproductive success, is similar to that of tropical passerines and provides further support for the existence of typical life history characteristics for tropical birds. SINOPSIS Las hipótesis relacionadas con la variación altitudinal en los ciclos de vida de aves están basadas en una gran cantidad de datos de aves de zona templada, mientras que para el trópico inclusive se desconoce la biología básica. Esto aplica en particular para aves que no son paserinos. Investigamos las actividades de anidamiento de Hoatzin (Opisthocumus hoazin) en un bosque pluvial primario de la amazonia ecuatorial. En nuestra área de estudio, los hoatzines viven y se reproducen en bosques inundados que bordean lagos y canales. Los intentos reproductivos estuvieron asociados a la época de lluvias y se agruparon en unos meses del año. Normalmente, estas aves anidan una vez al año. El reanidamiento solo ocurrio cuando hubo pérdidas durante la época de puesta. Los nidos fueron construidos en los árboles y arbustos más comunes en el hábitat. El número de huevos por camada vario de uno a siete, aunque el 51% de las camadas consistieron de dos huevos. El tiempo promedio de incubación fue de 32 días. El exito promedio de eclosionamiento (para todos los nidos) fue de 34% y el 50% de los pichones dejaron el nido, lo que dio un éxito de anidamiento en general de 17%. La causa principal de pérdida de nidos lo fue la depredación, en donde otras aves y culebras resultaron ser los principales depredadores. La pequeña ventana de tres meses para reproducirse parece ser el resultado de un fuerte constreñimiento para una reproducción exitosa, debido a una mejor protección de los nidos y mayor abundancia de alimentos durante la época de inundación. El hoatzin exhibe un ciclo de vida similar al de paserinos tropicales. Esto indica la efectividad de las presiones ambientales de selección que deben estar envueltas en la formación de dichos trasos. [source] CONFUSING CONVERGENT MORPHOLOGIES: DIVERSITY AND DIFFICULTIES IN NEW ZEALAND ERYTHROPELTIDALES AND BANGIALESJOURNAL OF PHYCOLOGY, Issue 2000W.A. Nelson An examination of New Zealand species of Porphyra and Bangia has led to the discovery of unexpectedly high diversity. In excess of 30 species of Porphyra and 5 species of Bangia can be distinguished, based on 18S rDNA sequence data. It is possible to develop a workable taxonomic framework to distinguish species of Porphyra found within this geographic region using a range of characters (morphological, anatomical, biochemical, physiological, life history characteristics). However, the taxonomic distinctions do not necessarily reflect phylogenetic relationships revealed by sequence analyses: convergence in character states is obscuring relationships. In the course of our work we have discovered that four species, originally described on the basis of traditional morphological and anatomical characters as Porphyra or Bangia, are more closely related to members of the order Erythropeltidales than to the Bangiales. These results are challenging us to consider new ways of describing and defining these organisms. We are finding convergence in character states, not only within Porphyra sens. lat. But spanning both the Bangiales and Erythropeltidales, which confounds both taxonomic distinctions and also phylogenetic hypotheses based on morphology and anatomy. This confusion could be countered effectively by the inclusion of molecular sequence data based on vouchered or type material in descriptions of taxa in the orders Bangiales and Erythropeltidales. This would allow conclusive identification of collected material by appropriate molecular tests, which are quicker and more direct identification tools than, for example, using characters drawn from the growth of these organisms under controlled culture conditions. [source] Seamount science scales undersea mountains: new research and outlookMARINE ECOLOGY, Issue 2010Thomas A. Schlacher Abstract Conventional wisdom suggests that seamounts harbour high levels of biodiversity and endemism, play important roles in marine biogeography, are hotspots of biological carbon processing, and support substantial fisheries. However, since fewer than 300 seamounts have been thoroughly sampled, these generalizations remain largely untested. This has provided the motivation for a number of seamount-focused research projects in recent years, including CenSeam, a field project within the Census of Marine Life. This issue presents some of the research output facilitated by CenSeam. Here we summarize the main findings and provide a précis of future research directions highlighted by contributors to the issue. Recent studies show that seamounts can have comparable levels of benthic diversity and endemism to continental margins, but their communities also include a distinct composition of species that can attain higher biomass. Reported geographic differentiation among seamount communities suggests limited larval dispersal, local speciation, geographic isolation, or a combination of these processes. Genetic studies contained in the issue address these themes explicitly, documenting complex patterns of connectivity that depend on spatial scale and life history characteristics. Globally, seamount ecosystems are also under pressure from bottom-contact fishing and ocean acidification. Contributions detailing the footprint of trawling and a risk assessment confirm what has long been suspected: seamount ecosystems are highly vulnerable to disturbance by bottom trawling and recovery from fishing impacts is a lengthy process, likely requiring decades at a minimum. A predicted shallowing of the aragonite saturation horizon caused by ocean acidification is predicted to place deep-water corals at risk, but seamounts may yet provide a spatial/chemical refuge from these impacts. The issue concludes with a ,myth-buster' synthesis that updates the status of the various seamount ecological paradigms. [source] Mandibular fractures in short-finned pilot whales, Globicephala macrorhynchusMARINE MAMMAL SCIENCE, Issue 1 2010Mollie Sue Oremland Abstract This study's objective was to investigate mandibular fractures in 50 short-finned pilot whales, Globicephala macrorhynchus, from two mass strandings. Based on current theories that this species is sexually dimorphic and polygynous, hypotheses were: (1) males should suffer more frequent or more substantial mandibular fractures than should females, and (2) fracture occurrence should increase with male reproductive maturity and potential correlates of maturity, such as age and length. Fractures were described and correlated with physical characteristics to infer possible explanations for injuries. Mandibular fractures were surprisingly common in males and females, being found in more than half of the animals examined (27/50, or 54% overall; 17/36 or 47% of females and 10/14 or 71% of males). Length was the only correlate of fracture presence; the proportion of animals showing evidence of fracture increased with length. These results offer some support to initial hypotheses, but there must be another set of consequences that contribute to mandibular fractures in females. A combination of intra- and interspecific interactions and life history characteristics may be responsible for fractures. Further research from a larger sample of this and other cetacean species are suggested to help elucidate both the causes and implications of mandibular fractures. [source] Selection for a dominant oncogene and large male size as a risk factor for melanoma in the Xiphophorus animal modelMOLECULAR ECOLOGY, Issue 15 2010ANDRÉ A. FERNANDEZ Abstract Adult height is a risk factor in numerous human cancers that involve aberrant receptor tyrosine kinase (RTK) signalling. However, its importance is debated due to conflicting epidemiological studies and the lack of useful in vivo models. In Xiphophorus fishes (Platyfishes/Swordtails), a functional RTK, Xiphophorus melanoma receptor kinase (Xmrk), serves as the dominant oncogene and has been maintained for several million years despite being deleterious and in an extremely unstable genomic region. Here we show that the Xmrk genotype is positively correlated with standard length in male and female wild caught Xiphophorus cortezi sampled throughout their phylogeographic distribution. Histopathology confirms the occurrence of malignant melanomas in both sexes; however, melanoma incidence was extremely male biased. Furthermore, males collected with malignant melanomas in the field were significantly larger than both Xmrk males collected without melanomas and wildtype (Xmrk deficient) males. These results not only provide a novel selective mechanism for the persistence of the germline Xmrk oncogene but also create an innovative avenue of melanoma research within the Xiphophorus fishes. Wildlife cancer in natural systems is a growing concern, therefore, future research investigating life history characteristics associated with certain phenotypes and genotypes that predispose an individual to cancer will be fundamental to increasing our understanding of the evolutionary biology of cancer in nature as well as in humans. [source] Distribution of the anther-smut pathogen Microbotryum on species of the CaryophyllaceaeNEW PHYTOLOGIST, Issue 1 2010Michael E. Hood Summary ,Understanding disease distributions is of fundamental and applied importance, yet few studies benefit from integrating broad sampling with ecological and phylogenetic data. Here, anther-smut disease, caused by the fungus Microbotryum, was assessed using herbarium specimens of Silene and allied genera of the Caryophyllaceae. ,A total of 42 000 herbarium specimens were examined, and plant geographical distributions and morphological and life history characteristics were tested as correlates of disease occurrence. Phylogenetic comparative methods were used to determine the association between disease and plant life-span. ,Disease was found on 391 herbarium specimens from 114 species and all continents with native Silene. Anther smut occurred exclusively on perennial plants, consistent with the pathogen requiring living hosts to overwinter. The disease was estimated to occur in 80% of perennial species of Silene and allied genera. The correlation between plant life-span and disease was highly significant while controlling for the plant phylogeny, but the disease was not correlated with differences in floral morphology. ,Using resources available in natural history collections, this study illustrates how disease distribution can be determined, not by restriction to a clade of susceptible hosts or to a limited geographical region, but by association with host life-span, a trait that has undergone frequent evolutionary transitions. [source] A reassessment of sexual dimorphism in human senescence: Theory, evidence, and causationAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 2 2006Brent M. Graves Age-specific mortality rates of men are higher than those of women, and men have shorter average life spans than women. This has been interpreted as evidence of sexual dimorphism in rates of senescence. However, because mortality can be caused by numerous factors in addition to senescence, higher mortality rates do not necessarily indicate more rapid senescence. In this paper, we (1) emphasize the necessity of decoupling mortality and senescence when considering sexual dimorphism in senescence, (2) present a theoretical framework for the hypothesis that selection affects senescence in human males and females differently due to different life history characteristics, (3) consider phenotypic evidence from the literature that human males show a later onset of senescence than human females, despite exhibiting higher mortality rates, and (4) discuss the potential roles of mutation accumulation and antagonistic pleiotropy in the evolution of sexual dimorphism in senescence. Am. J. Hum. Biol. 18:161,168, 2006. © 2006 Wiley-Liss, Inc. [source] Forest Regeneration in a Chronosequence of Tropical Abandoned Pastures: Implications for Restoration EcologyRESTORATION ECOLOGY, Issue 4 2000T. Mitchell Aide Abstract During the mid-1900s, most of the island of Puerto Rico was deforested, but a shift in the economy from agriculture to small industry beginning in the 1950s resulted in the abandonment of agricultural lands and recovery of secondary forest. This unique history provides an excellent opportunity to study secondary forest succession and suggest strategies for tropical forest restoration. To determine the pattern of secondary succession, we describe the woody vegetation in 71 abandoned pastures and forest sites in four regions of Puerto Rico. The density, basal area, aboveground biomass, and species richness of the secondary forest sites were similar to those of the old growth forest sites (>80 yr) after approximately 40 years. The dominant species that colonized recently abandoned pastures occurred over a broad elevational range and are widespread in the neotropics. The species richness of Puerto Rican secondary forests recovered rapidly, but the species composition was quite different in comparison with old growth forest sites, suggesting that enrichment planting will be necessary to restore the original composition. Exotic species were some of the most abundant species in the secondary forest, but their long-term impact depended on life history characteristics of each species. These data demonstrate that one restoration strategy for tropical forest in abandoned pastures is simply to protect the areas from fire, and allow natural regeneration to produce secondary forest. This strategy will be most effective if remnant forest (i.e., seed sources) still exist in the landscape and soils have not been highly degraded. Patterns of forest recovery also suggest strategies for accelerating natural recovery by planting a suite of generalist species that are common in recently abandoned pastures in Puerto Rico and throughout much of the neotropics. [source] Euplotespora binucleata n. gen., n. sp. (Protozoa: Microsporidia), a Parasite Infecting the Hypotrichous Ciliate Euplotes woodruffi, with Observations on Microsporidian Infections in CiliophoraTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 3 2008SERGEI I. FOKIN ABSTRACT. A new microsporidian species, Euplotespora binucleata n. gen., n. sp., from the brackish-water ciliate Euplotes woodruffi is described and defined on the basis of life history characteristics, light and electron microscopic features, and small subunit (SSU) ribosomal DNA (rDNA) sequencing. The life cycle of E. binucleata n. sp. probably has rather short merogonic and relatively long sporogonic phases. Some uninuclear meronts and sporonts, along with diplokaryotic sporoblasts and spores, were found in experimentally infected host cells. Such a peculiar life cycle has been induced experimentally in Euplotes eurystomus and constitutively microsporidian-free stocks of E. woodruffi. Spores of E. binucleata n. sp. are monomorphic, ovoid,cylindrical in shape, 3.44±0.17 × 1.65±0.22 ,m in size, and characterized by a diplokaryotic condition and a large posterior vacuole. The polar tube is isofilar, 4.5,5.5 ,m in length when ejected, and lacking a distinctive coiled region (half-coiled). The polaroplast is divided into two regions: the anterior part has a few lamellae close to the anchoring disc; and the posterior part is a rounded body (sack), about one-quarter of the spore length. Spores do not appear to cluster together as a group. Each spore is surrounded by a sporophorous membrane closely adjacent to the exospore layer. A phylogenetic analysis of SSU rDNA sequences by different methods placed E. binucleata n. sp. in a clade with representatives of the microsporidian genera Cystosporogenes and Vittaforma. Observations of microsporidia in several other ciliates are discussed in view of the microsporidian infection frequency in the phylum Ciliophora. 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