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Life-history Traits (life-history + trait)
Kinds of Life-history Traits Selected AbstractsComparative life-history traits in a fig wasp community: implications for community structureECOLOGICAL ENTOMOLOGY, Issue 2 2010MAHUA GHARA 1. Whether life-history traits can determine community composition and structure is an important question that has been well explored theoretically, but has received scant empirical attention. Life-history traits of a seven-member community of galler and parasitoid fig wasp species (Chalcidoidea), developing within the inflorescences (syconia) of Ficus racemosa (Moraceae) in India, were determined and used to examine community structure and ecology. 2. Gallers were pro-ovigenic (all eggs are mature upon adult emergence) whereas parasitoids were synovigenic (eggs mature progressively during adult lifespan). Initial egg load was correlated with body size for some species, and there was a trade-off between egg number and egg size across all species. Although all species completed their development and left the syconium concurrently, they differed in their adult and pre-adult lifespans. Providing sucrose solutions increased parasitoid lifespan but had no effect on the longevity of some galler species. While feeding regimes and body size affected longevity in most species, an interaction effect between these variables was detected for only one species. 3. Life-history traits of wasp species exhibited a continuum in relation to their arrival sequence at syconia for oviposition during syconium development, and therefore reflected their ecology. The largest number of eggs, smallest egg sizes, and shortest longevities were characteristic of the earliest-arriving galling wasps at the smallest, immature syconia; the converse characterised the later-arriving parasitoids at the larger, already parasitised syconia. Thus life history is an important correlate of community resource partitioning and can be used to understand community structure. 4. This is the first comprehensive study of life-history traits in a fig wasp community. The comparative approach revealed constraints and flexibility in trait evolution. [source] Life-history traits of the edible stinkbug, Encosternum delegorguei (Hem., Tessaratomidae), a traditional food in southern AfricaJOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2009C. M. Dzerefos Abstract Little is known of the life history of the edible stinkbug, Encosternum delegorguei, although it is an important food for people living in north-eastern South Africa and southern Zimbabwe. The present study aimed to establish key elements influencing long-term sustainable harvesting. Outdoor insectaries of two sizes were constructed to observe: daily activity, utilization of plants, copulation, oviposition, eclosion and survival from May 2006 to February 2007. The rest of the annual life cycle was observed in the field in March and April 2007 and identified as univoltine. In autumn (May) E. delegorguei entered reproductive diapause and aggregated within the escarpment mist-belt where it survived the winter on vapour condensation without feeding. Monthly dissections showed that abdominal fat content was highest in June. In spring (September) E. delegorguei fed on sap of the trees Combretum imberbe, Combretum molle, Peltophorum africanum, to a lesser degree on Dodonaea viscosa and the grass Pennisetum clandestinum. Copulation occurred in October and November. An overall total of 1752 E. delegorguei eggs were laid by 103 females and incubation time averaged 18.7 ± 9.0 days (range 7,37) at outdoor temperature ranging from 11°C to 25°C. The mean number of eggs in 64 egg masses was 27.4 ± 13.9 (range of 2,56 eggs). Shade cloth (68.8%) was the most commonly used substrate for depositing eggs followed by P. clandestinum (12.5%), C. imberbe (7.8%), P. africanum (6.3%), D. viscosa (1.6%), C. molle (1.6%) and C. erythrophyllum (1.6%). The parasitoid wasp, Anastatus sp. (Hymenoptera: Eupelmidae) infected 57% of the eggs deposited by captive females. Availability of food plants in combination with parasitoid threat may be a reason for seasonal migration between overwintering sites within the mist-belt and summer oviposition sites. Diminishing harvests could be attributed to fuelwood harvesting of food plants in the summer sites. [source] Spatially heterogeneous stochasticity and the adaptive diversification of dormancyJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 10 2009E. Rajon Abstract Diversified bet-hedging, a strategy that leads several individuals with the same genotype to express distinct phenotypes in a given generation, is now well established as a common evolutionary response to environmental stochasticity. Life-history traits defined as diversified bet-hedging (e.g. germination or diapause strategies) display marked differences between populations in spatial proximity. In order to find out whether such differences can be explained by local adaptations to spatially heterogeneous environmental stochasticity, we explored the evolution of bet-hedging dormancy strategies in a metapopulation using a two-patch model with patch differences in stochastic juvenile survival. We found that spatial differences in the level of environmental stochasticity, restricted dispersal, increased fragmentation and intermediate survival during dormancy all favour the adaptive diversification of bet-hedging dormancy strategies. Density dependency also plays a major role in the diversification of dormancy strategies because: (i) it may interact locally with environmental stochasticity and amplify its effects; however, (ii) it can also generate chaotic population dynamics that may impede diversification. Our work proposes new hypotheses to explain the spatial patterns of bet-hedging strategies that we hope will encourage new empirical studies of this topic. [source] Life-history traits of the stone loach Barbatula barbatulaJOURNAL OF FISH BIOLOGY, Issue 1 2010D. Vinyoles The life-history tactics of the stone loach Barbatula barbatula were studied in a Mediterranean-type climate stream (Matarranya River) located in the Ebro River basin (north-east Spain). Maximum observed ages were 2+ years in both sexes (1% of individuals), although only 0+ and 1+ year age groups were well represented. It is the lowest longevity reported for this species in its entire distribution. The seasonal growth period started in June and continued until November, but the pattern observed was different to northern populations. Barbatula barbatula in the Matarranya River was a multiple spawner, releasing small batches of oocytes between April and June. The fecundity of females was higher and the size of oocytes smaller in 1984 than in 1985. The relative fecundity (number of ripening and ripe oocytes g,1 of fish) was lower than in northern European populations. The role of the particular environmental conditions of a Mediterranean stream was discussed in relation to the life-history tactics of B. barbatula. [source] Environment-related life-history trait variations of the red-bellied piranha Pygocentrus nattereri in two river basins of the Bolivian AmazonJOURNAL OF FISH BIOLOGY, Issue 4 2007F. Duponchelle Life-history traits of Pygocentrus nattereri were compared in two populations inhabiting connected tributaries of the upper Madera River: the white water Mamoré River and the clear water Iténez River. As white waters provide better trophic conditions than clear waters, the size at maturity, fecundity, reproductive effort, condition and growth of P. nattereri should be greater in the more productive white water river (Mamoré) than in the less-productive clear water river (Iténez). Breeding periods were highly seasonal and similar in both rivers and under strong influence of photoperiod. Oocyte size-frequency distributions, together with the frequent occurrence of recovering females indicated that an individual female spawns at least twice during the breeding season. As predicted, fish of the Mamoré were significantly larger at maturity and had higher fecundity and condition factor values than those of the Iténez. Fish from both rivers matured as yearlings. The higher growth potential of females was better expressed in the Mamoré than in the Iténez, where growth differences between sexes were weak. Females had a significantly better growth in the Mamoré than in the Iténez. The observed life-history traits associations were consistent with the hypothesis of better trophic conditions in the Mamoré. In addition, previous genetic analyses evidenced that the colonization of the two basins is recent and that extant populations have very similar genetic backgrounds. This suggests that the observed variations in life-history traits of P. nattereri are not related to historical factors (genetic drift) between two phylogeographically distinct lineages, but rather due to the contrasting environmental conditions in the white and clear waters. [source] Life-history traits associated with fragmentation vulnerability of lizards in the Thousand Island Lake, ChinaANIMAL CONSERVATION, Issue 4 2009Y. Wang Abstract Following habitat fragmentation, the remnant faunal community will undergo a period of species loss or ,relaxation.' Theory predicts that species with particular life-history traits, such as a small population size, small geographical range, low fecundity and large body size, should be more vulnerable to fragmentation. In this study, we investigated the relationships between the above life-history traits and the fragmentation vulnerability index (the number of islands occupied) of five lizard species inhabiting recently isolated land-bridge islands in the Thousand Island Lake, China. Data on life-history traits were collected from field surveys (population density) and from the literature (body size, clutch size and geographical range size). The species,area relationships for lizards sampled from the mainland versus on the islands differed significantly (i.e. the number of species inhabiting islands was decreased relative to similar-sized areas on the mainland), indicating that species extinction has occurred on all of the study islands following isolation. For the fragmentation vulnerability index, model selection based on Akaike's information criterion identified natural density at mainland sites as the best correlate of vulnerability to fragmentation, supporting the hypothesis that rare species are most vulnerable to local extinction and will be lost first from fragmented landscapes. In contrast, there was little evidence for an effect of lizards' snout,vent length, clutch size or geographical range size on fragmentation vulnerability. Identification of species traits that render some species more vulnerable to fragmentation than others has important implications for conservation and can be used to aid direct management efforts. [source] Land-use legacies in a central Appalachian forest: differential response of trees and herbs to historic agricultural practicesAPPLIED VEGETATION SCIENCE, Issue 2 2010James M. Dyer Abstract Question: Are contemporary herb and tree patterns explained by historic land use practices? If so, are observed vegetation patterns associated with life-history characteristics, soil properties, or other environmental variables? Location: Southeastern Ohio, USA. Methods: Using archival records, currently forested sites were identified with distinct land use histories: cultivated, pasture (but not plowed), and reference sites which appear to have never been cleared. Trees were recorded by size and species on twenty 20 m × 20 m plots; percent cover was estimated for each herb species in nested 10 m × 10 m plots. Environmental characteristics were noted, and soil samples analysed for nutrient availability and organic matter. Nonmetric multidimensional scaling ordination was performed separately on both tree and herb datasets to graphically characterize community composition among plots. Life-history traits were investigated to explain observed compositional differences. Results: Vegetation patterns were explained by current environmental gradients, especially by land-use history. Cultivated and pasture sites had similar tree composition, distinct from reference sites. Herb composition of pasture and reference sites was similar and distinct from cultivated sites, suggesting the ,tenacity' of some forest herbs on formerly cleared sites. Tilling removes rhizomatous species, and disfavors species with unassisted dispersal. These life-history traits were underrepresented on cultivated sites, although ant-dispersed species were not. Conclusions: Historic land-use practices accounted for as much variation in species composition as environmental gradients. Furthermore, trees and herbs responded differently to past land-use practices. Life-history traits of individual species interact with the nature of disturbance to influence community composition. [source] How do paedomorphic newts cope with lake drying?ECOGRAPHY, Issue 4 2003Mathieu Denoël Paedomorphosis, in which adult individuals retain larval traits, is widespread in newts and salamanders. Most evolutionary models predict the maintenance of this life-history trait in favourable aquatic habitats surrounded by hostile terrestrial environments. Nevertheless, numerous ponds inhabited by paedomorphic individuals are unpredictable and temporary. In an experimental framework, I showed that paedomorphic newts were able to metamorphose and thus survive in the absence of water. However, the mere decrease of water level or the life space do not seem to induce metamorphosis in paedomorphs. On the contrary, drying up induces almost all individuals to move on land and after that to colonize other aquatic sites located nearby. Such terrestrial migrations allow survival in drying conditions without metamorphosis as long as the distances of terrestrial migration are short. These results are consistent with the presence of paedomorphs in drying ponds and are in favor of classic optimality models predicting metamorphosis in unfavorable environments. [source] Life-history, genotypic, and environmental correlates of clutch size in the Glanville fritillary butterflyECOLOGICAL ENTOMOLOGY, Issue 2 2007MARJO SAASTAMOINEN Abstract 1.,Glanville fritillary butterfly (Melitaea cinxia) females lay up to 10 clutches of 50,300 eggs in their lifetime. Clutch size is an important life-history trait as larval group size affects survival throughout larval development. 2.,Two experiments were carried out in a large population cage in the field to investigate the life-history and environmental correlates of clutch size. 3.,Clutch size decreased with the cumulative number of eggs laid previously, increased with both female body weight and the number of days between consecutive clutches. 4.,Genotypic differences among females in the glycolytic enzyme phosphoglucose isomerase had a significant influence on clutch size, partly because females of particular genotypes were able to initiate oviposition earlier in the day and thereby take advantage of the most favourable environmental conditions for oviposition. 5.,Factors influencing clutch size were partly different in two summers, indicating the modulating effect of prevailing environmental conditions on reproductive performance. [source] Dispersal between host populations in field conditions: navigation rules in the parasitoid Venturia canescensECOLOGICAL ENTOMOLOGY, Issue 3 2003E. Desouhant Abstract. 1. Dispersal is a life-history trait that can have great ecological and evolutionary consequences, however understanding of how insects disperse is limited. 2. Navigation rules of the solitary koinobiont parasitoid of the pyralid moth larvae Venturia canescens (Gravenhorst) were studied in conditions that it is likely to meet when dispersing between host populations and in the absence of cues related directly to the presence of hosts. 3. Mark,release,recapture experiments were conducted in a natural host-free habitat, and letting the animals disperse for different periods. 4. In the presence of vegetation, wasps seemed to disperse rapidly (1 h for an area of ,,1 ha) and capture rates were independent of both dispersal time and distance from the release point. 5. The navigation rules of V. canescens during dispersal between tree stands can be summarised as: move up- or down-wind, avoid or pass through open, sunny areas, and go for shady and dense vegetation. 6. The consequences of the navigation rules for host,parasitoid dynamics are discussed in relation to different spatial scales. [source] Senescence of immune defence in Bombus workersECOLOGICAL ENTOMOLOGY, Issue 2 2002Claudie Doums Abstract 1. Senescence in workers of social insects is a particularly intriguing life-history trait as the future fitness of workers relies primarily on age-dependent survival rate. The pattern of senescence of immune defence traits was investigated under laboratory conditions in workers of two bumble bees: Bombus terrestris and B. lucorum. 2. In both species, there was a significant decrease with age in the ability to encapsulate a foreign object (a global measure of the efficiency of immune systems). This pattern of senescence was observed in all colonies in B. terrestris (seven) and B. lucorum (eight) assayed, even though, for the latter, there was some heterogeneity among colonies. 3. In B. terrestris, two other measures of immune defence were taken: the relative percentage of fat body in the abdomen and the concentration of haemocytes (the immune defence cells). The quantity of fat body increased only slightly with age and there was no effect for the concentration of haemocytes. Interestingly, the concentration of haemocytes decreased strongly after an encapsulation response, regardless of the age of workers. 4. The importance of the senescence pattern observed for the immune defence traits is discussed in the context of the social biology of workers. [source] CORRELATED EVOLUTION OF MIGRATION AND SEXUAL DICHROMATISM IN THE NEW WORLD ORIOLES (ICTERUS)EVOLUTION, Issue 12 2009Nicholas R. Friedman The evolution of sexual dimorphism has long been attributed to sexual selection, specifically as it would drive repeated gains of elaborate male traits. In contrast to this pattern, New World oriole species all exhibit elaborate male plumage, and the repeated gains of sexual dichromatism observed in the genus are due to losses of female elaboration. Interestingly, most sexually dichromatic orioles belong to migratory or temperate-breeding clades. Using character scoring and ancestral state reconstructions from two recent studies in Icterus, we tested a hypothesis of correlated evolution between migration and sexual dichromatism. We employed two discrete phylogenetic comparative approaches: the concentrated changes test and Pagel's discrete likelihood test. Our results show that the evolution of these traits is significantly correlated (CCT: uncorrected P < 0.05; ML: LRT = 12.470, P < 0.005). Indeed, our best model of character evolution suggests that gains of sexual dichromatism are 23 times more likely to occur in migratory taxa. This study demonstrates that a life-history trait with no direct relationship with sexual selection has a strong influence on the evolution of sexual dichromatism. We recommend that researchers further investigate the role of selection on elaborate female traits in the evolution of sexual dimorphism. [source] Correcting the short-term effect of food deprivation in a damselfly: mechanisms and costsJOURNAL OF ANIMAL ECOLOGY, Issue 1 2008Melina Campero Summary 1Mass at emergence is a life-history trait strongly linked to adult fitness. Therefore, when faced with transient food shortage in the larval stage, mass-correcting mechanisms are common. 2These correcting mechanisms may carry costs with them. On one hand, these costs may be overestimated because they can be confounded with the direct effects of the transient food shortage itself. On the other hand, costs may be underestimated by ignoring physiological costs. Another largely neglected topic is that correcting mechanisms and costs may critically depend upon other stressors that often co-occur. 3Here, we identify the mass-correcting mechanisms and their associated costs at emergence in the damselfly Coenagrion puella, after being stressed by a transient period of starvation and a subsequent exposure to pesticide stress during the larval stage. We introduce path analysis to disentangle direct costs of starvation and the mass-correcting mechanisms in terms of immune response. 4As predicted, we found no differences in mass at emergence. Starvation directly resulted in a costly delayed emergence and a decreased immune response at emergence. Mass-correcting mechanisms included a prolonged post-starvation period, reduced mass loss at emergence and compensatory growth, although the latter only in females under pesticide stress. 5The mass-correcting mechanisms were associated with beneficial effects on investment in immune response, but only in the absence of pesticide stress. Under pesticide stress, these beneficial effects were mostly undone or overruled, resulting in negative effects of the mass-correcting mechanisms in terms of immune response. 6Our results stress the importance of and introduce a statistical way of disentangling direct costs of starvation and the mass-correcting mechanisms themselves, and the importance of including physiological endpoints in this kind of studies. [source] An invasive species imposes selection on life-history traits of a native frogBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010MATTHEW J. GREENLEES As well as their direct ecological impacts on native taxa, invasive species can impose selection on phenotypic attributes (morphology, physiology, behaviour, etc.) of the native fauna. In anurans, body size at metamorphosis is a critical life-history trait: for most challenges faced by post-metamorphic anurans, larger size at metamorphosis probably enhances survival. However, our studies on Australian frogs (Limnodynastes convexiusculus) show that this pattern can be reversed by the arrival of an invasive species. When metamorph frogs first encounter invasive cane toads (Bufo marinus), they try to eat the toxic invader and, if they are able to do so, are likely to die from poisoning. Because frogs are gape-limited predators, small metamorphs cannot ingest a toad and thus survive long enough to disperse away from the natal pond (and thus from potentially deadly toads). These data show that larger size at metamorphosis can reduce rather than increase anuran survival rates, because larger metamorphs are more easily able to ingest (and thus be poisoned by) metamorph cane toads. Our results suggest that patterns of selection on life-history traits of native taxa (such as size and age at metamorphosis, seasonal timing of breeding and duration of pondside aggregation prior to dispersal) can be modified by the arrival of an invasive species. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 329,336. [source] Integrating species life-history traits and patterns of deforestation in amphibian conservation planningDIVERSITY AND DISTRIBUTIONS, Issue 1 2010C. G. Becker Abstract Aim, To identify priority areas for amphibian conservation in southeastern Brazil, by integrating species life-history traits and patterns of deforestation. Location, State of São Paulo, Brazil. Methods, We used the software Marxan to evaluate different scenarios of amphibian conservation planning. Our approach differs from previous methods by explicitly including two different landscape metrics; habitat split for species with aquatic larvae, and habitat loss for species with terrestrial development. We evaluated the effect of habitat requirements by classifying species breeding habitats in five categories (flowing water, still water permanent, still water temporary, bromeliad or bamboo, and terrestrial). We performed analyses using two scales, grid cells and watersheds and also considered nature preserves as protected areas. Results, We found contrasting patterns of deforestation between coastal and inland regions. Seventy-six grid cells and 14 watersheds are capable of representing each species at least once. When accounting for grid cells already protected in state and national parks and considering species habitat requirements we found 16 high-priority grid cells for species with one or two reproductive habitats, and only one cell representing species with four habitat requirements. Key areas for the conservation of species breeding in flowing and permanent still waters are concentrated in southern state, while those for amphibians breeding in temporary ponds are concentrated in central to eastern zones. Eastern highland zones are key areas for preserving species breeding terrestrially by direct or indirect development. Species breeding in bromeliads and bamboos are already well represented in protected areas. Main conclusions, Our results emphasize the need to integrate information on landscape configuration and species life-history traits to produce more ecologically relevant conservation strategies. [source] Profiling invasive fish species: the importance of phylogeny and human useDIVERSITY AND DISTRIBUTIONS, Issue 4 2005Carles Alcaraz ABSTRACT Understanding the ecological differences between native and invasive species is of considerable scientific and practical interest. We examined such differences between native and invasive inland fish species from the Iberian Peninsula in order to analyse the importance of phylogenetic correction and variability (in addition to central tendency). We collected 26 quantitative and qualitative variables on the ecology, life-history traits and human use of the 69 inland fish species of the Iberian Peninsula, including native, invasive and migratory species. The taxonomic distribution of invasive fish species deviated significantly from world freshwater richness and in contrast to native species, invasive fish belongs to only five taxonomic orders but to a wide spectrum of families not native to the Iberian Peninsula. Because the life-history traits were highly dependent on taxonomy, the results, with or without applying phylogenetic methods, differed and after accounting for phylogeny, invasive species displayed higher and wider latitude in general and a different reproductive season mainly among salmonids and cyprinids. Human use was also significantly different between native and invasive fish species and produced more variability in life-history traits of invasive species and uneven taxonomic distribution because of the high diversity of species introduced. We show that accounting for taxonomy and studying variability in addition to central tendency is important in the comparison of life-history traits between native and invasive species. [source] Conifers as invasive aliens: a global survey and predictive frameworkDIVERSITY AND DISTRIBUTIONS, Issue 5-6 2004David M. Richardson ABSTRACT We summarize information on naturalized and invasive conifers (class Pinopsida) worldwide (data from 40 countries, some with remote states/territories), and contrast these findings with patterns for other gymnosperms (classes Cycadopsida, Gnetopsida and Ginkgoopsida) and for woody angiosperms. Eighty conifer taxa (79 species and one hybrid; 13% of species) are known to be naturalized, and 36 species (6%) are ,invasive'. This categorization is based on objective and conservative criteria relating to consistency of reproduction, distance of spread from founders, and degree of reliance on propagules from the founder population for persistence in areas well outside the natural range of species. Twenty-eight of the known invasive conifers belong to one family (Pinaceae) and 21 of these are in one genus (Pinus). The Cupressaceae (including Taxodiaceae) has six known invasive species (4%) in four genera, but the other four conifer families have none. There are also no known invasive species in classes Cycadopsida, Gnetopsida or Ginkgoopsida. No angiosperm family comprising predominantly trees and shrubs has proportionally as many invasive species as the Pinaceae. Besides the marked taxonomic bias in favour of Pinaceae, and Pinus in particular, invasiveness in conifers is associated with a syndrome of life-history traits: small seed mass (< 50 mg), short juvenile period (< 10 year), and short intervals between large seed crops. Cryptomeria japonica, Larix decidua, Picea sitchensis, Pinus contorta, Pinus strobus, and Pseudotsuga menziesii exemplify this syndrome. Many rare and endangered conifer species exhibit opposite characters. These results are consistent with earlier predictions made using a discriminant function derived from attributes of invasive and noninvasive Pinus species. Informative exceptions are species with small seeds (< 4 mg, e.g. Chamaecyparis spp., Pinus banksiana, Tsuga spp. , mostly limited to wet/mineral substrates) or otherwise ,non-invasive' characters (e.g. large seeds, fleshy fruits, e.g. Araucaria araucana, Pinus pinea, Taxus baccata that are dependent on vertebrates for seed dispersal). Most conifers do not require coevolved mutualists for pollination and seed dispersal. Also, many species can persist in small populations but have the genetic and reproductive capacity to colonize and increase population size rapidly. The underlying mechanisms mediating conifer invasions are thus easier to discern than is the case for most angiosperms. Further information is needed to determine the extent to which propagule pressure (widespread dissemination, abundant plantings, long history of cultivation) can compensate for low ,inherent invasiveness'. [source] Latitudinal patterns in abundance and life-history traits of the mole crab Emerita brasiliensis on South American sandy beachesDIVERSITY AND DISTRIBUTIONS, Issue 2 2004Omar Defeo ABSTRACT Demographic and life-history attributes of the mole crab Emerita brasiliensis were analysed along 2700 km of the Atlantic coast of South America, including sandy beaches at the southernmost limit (Uruguay) and at the core of its geographical range (Brazil). Population features varied markedly within this range and exhibited systematic geographical patterns of variation. Abundance significantly increased from temperate to subtropical beaches, and the same held true for the asymptotic weight of males. Conversely, length at maturity and asymptotic weight of females increased from subtropical to temperate beaches, being inversely related to sea water temperature. Macroecological patterns in abundance and body weight showed the first large-scale evidence of scaling of population density to body size for a sandy beach population. Mortality rates (both sexes) followed a nonlinear increase from low-density temperate beaches to high-density subtropical beaches. The effect of habitat quality and availability could explain discontinuities in the species distribution within its range, and also differential responses in life-history attributes at a local scale. Asymmetries and converse latitudinal trends between sexes suggest that there is not a single general factor determining large-scale patterns in life-history traits of this species. Our results reinforce the view that density-dependent and environmental factors operating together regulate sandy beach populations. The need to develop macroecological studies in sandy beach ecology is highlighted, as knowledge acquired from local to large spatial scales throws light on population structure and regulation mechanisms. [source] Comparative life-history traits in a fig wasp community: implications for community structureECOLOGICAL ENTOMOLOGY, Issue 2 2010MAHUA GHARA 1. Whether life-history traits can determine community composition and structure is an important question that has been well explored theoretically, but has received scant empirical attention. Life-history traits of a seven-member community of galler and parasitoid fig wasp species (Chalcidoidea), developing within the inflorescences (syconia) of Ficus racemosa (Moraceae) in India, were determined and used to examine community structure and ecology. 2. Gallers were pro-ovigenic (all eggs are mature upon adult emergence) whereas parasitoids were synovigenic (eggs mature progressively during adult lifespan). Initial egg load was correlated with body size for some species, and there was a trade-off between egg number and egg size across all species. Although all species completed their development and left the syconium concurrently, they differed in their adult and pre-adult lifespans. Providing sucrose solutions increased parasitoid lifespan but had no effect on the longevity of some galler species. While feeding regimes and body size affected longevity in most species, an interaction effect between these variables was detected for only one species. 3. Life-history traits of wasp species exhibited a continuum in relation to their arrival sequence at syconia for oviposition during syconium development, and therefore reflected their ecology. The largest number of eggs, smallest egg sizes, and shortest longevities were characteristic of the earliest-arriving galling wasps at the smallest, immature syconia; the converse characterised the later-arriving parasitoids at the larger, already parasitised syconia. Thus life history is an important correlate of community resource partitioning and can be used to understand community structure. 4. This is the first comprehensive study of life-history traits in a fig wasp community. The comparative approach revealed constraints and flexibility in trait evolution. [source] Density-dependent polyphenism and geographic variation in size among two populations of lubber grasshoppers (Romalea microptera)ECOLOGICAL ENTOMOLOGY, Issue 5 2009JASON E. JANNOT Abstract. 1. Density-dependent phase polyphenism occurs when changes in density during the juvenile stages result in a developmental shift from one phenotype to another. Density-dependent phase polyphenism is common among locusts (Orthoptera: Acrididae). 2. Previously, we demonstrated a longitudinal geographic cline in adult body size (western populations = small adults; eastern populations = large adults) in the eastern lubber grasshopper (Romalea microptera) in south Florida. As lubbers are confamilial with locusts, we hypothesised that the longitudinal size cline was partly due to density-dependent phase polyphenism. 3. We tested the effect of density, population, and density×population interaction on life-history traits (pronotum length, mass, cumulative development time, growth rate) of, and proportion surviving to, each of the five instars and the adult stage in a 2 × 3 factorial laboratory experiment with two lubber populations, each reared from hatchling to adult at three different densities. 4. The effect of density on life history and survival was independent of the effects of population on life history and survival. Higher densities led to larger adult sizes (pronotum, mass) and lower survivorship. The western population had smaller adult masses, fewer cumulative days to the adult stage, and higher survivorship than the eastern population. 5. Our data suggest that lubber grasshoppers exhibit density-dependent phase polyphenism initiated by the physical presence of conspecifics. However, the plastic response of adult size to density observed in the laboratory is not consistent with the relationship between phenotypes and adult density in the field. Genetic differences between populations observed in the laboratory could contribute to size and life-history differences among lubber populations in the field. [source] Life-history strategy in an oligophagous tephritid: the tomato fruit fly, Neoceratitis cyanescensECOLOGICAL ENTOMOLOGY, Issue 4 2008THIERRY BRÉVAULT Abstract 1.,In phytophagous insects, life-history traits mainly depend on host plant range. Substantial longevity, high fecundity and larval competition are the major traits of polyphagous Tephritidae while species with a restricted host range generally exhibit a lower longevity and fecundity as well as mechanisms to avoid larval competition. Our aim in this study was to investigate the life history of an oligophagous species, the tomato fruit fly, Neoceratitis cyanescens (Bezzi). 2.,We determined life tables under laboratory conditions in order to calculate the main demographic parameters of N. cyanescens and studied the influence of larval and adult diet on life-history traits. 3.,The mean longevity of N. cyanescens females was 40 days. There was a strong synchronisation of female maturity. Oviposition showed an early peak at 9,13 days after a short pre-oviposition period (6 days). The absence of proteins in the adult diet both delayed ovarian maturation and decreased female fecundity. In addition, females originating from tomato fruits produced significantly more eggs than females originating from bugweed or black nightshade, showing that even the larval host plant may strongly affect the subsequent fecundity of adult females. 4.,The traits of N. cyanescens are then discussed in the light of those documented for polyphagous and monophagous tephritids. Neoceratitis cyanescens displayed attributes intermediate between those of polyphagous and monophagous tephritids. Its smaller clutch size compared with polyphagous species and its specialisation on the Solanaceae family whose fruits contain toxic compounds may help in reducing intra- and inter-specific competition, respectively. [source] Selection for discontinuous life-history traits along a continuous thermal gradient in the butterfly Aricia agestisECOLOGICAL ENTOMOLOGY, Issue 6 2005Steve Burke Abstract., 1.,Voltinism may be conceptualised as the product of development rate and the timing of diapause , two components that together translate gradual environmental variation, through periods of growth and development, into ,generational units'. This may result in very different selection pressures on diapause induction and development time in populations with different numbers of generations per year. 2.,Developmental data from univoltine and bivoltine populations of the butterfly Aricia agestis (Lepidoptera: Lycaenidae) in North Wales were used to examine larval development time and the timing of diapause, and their contribution towards voltinism in populations that occur at the same latitude and in geographic proximity to one another along a thermal gradient. 3.,The critical photoperiod for diapause induction in univoltines and bivoltines from the same latitude differed by more than 1.5 h. 4.,Development time also differed significantly between these populations, in line with predictions that bivoltines would need to exhibit shorter development times in order to achieve two complete generations per year. Shorter development times for bivoltines result in lower pupal weights, suggesting a trade-off exists between generation number and body size that may dictate the position of the transition zone between the two life-history strategies. Analysis of development times in a third population, from southern England, with greater thermal availability than those from North Wales, further supports this hypothesised trade-off. 5.,To achieve the conversion of a continuous thermal gradient into the binary biological response from univoltism to bivoltism, bivoltines speed up development, reduce adult body size and shift their diapause induction response. [source] Egg maturation strategy and its associated trade-offs: a synthesis focusing on LepidopteraECOLOGICAL ENTOMOLOGY, Issue 4 2005Mark A. Jervis Abstract., 1.,Insects vary considerably between and within orders, and even within the same genus, in the degree to which the female's lifetime potential egg complement is mature when she emerges as an adult. 2.,The ,ovigeny index' (OI) , the number of eggs females have ready to lay divided by the lifetime potential fecundity , quantifies variation in the degree of early life concentration of egg production, and also variation in initial reproductive effort. 3.,Here, an integrated set of hypotheses is presented, based on a conceptual model of resource allocation and acquisition, concerning trade-offs at the interspecific level between initial investment in egg production (as measured by OI) and other life-history traits in holometabolous insects. 4.,The evidence supporting each of these hypotheses is reviewed, and particular attention is paid to the Lepidoptera, as relevant life-history data are rapidly accumulating for this ecologically and economically important group. 5.,There is evidence at the interspecific level supporting: (i) a link between OI and a trade-off between soma and non-soma in Trichoptera and Hymenoptera (the proportionate allocation to soma decreases with increasing OI); (ii) a negative correlation between OI and dependency on external nutrient inputs (via adult feeding) in Hymenoptera and in Lepidoptera; (iii) a negative correlation between OI and the degree of polyandry (and nuptial gift, i.e. spermatophore, use) in Lepidoptera; (iv) negative correlations between OI and resource re-allocation capabilities (egg and thoracic musculature resorption) in Hymenoptera and in Lepidoptera; (v) a negative correlation between lifespan and OI in Trichoptera, Hymenoptera, and Lepidoptera, indicating a cost of reproduction; (vi) a link between winglessness and an OI of one in Lepidoptera; (vii) a negative correlation between OI and the degree of female mobility in winged Lepidoptera; and (viii) a negative correlation between OI and larval diet breadth (as mediated by oviposition strategy) in Lepidoptera. [source] Host shifting by Operophtera brumata into novel environments leads to population differentiation in life-history traitsECOLOGICAL ENTOMOLOGY, Issue 5 2003Adam J. Vanbergen Abstract., 1. Operophtera brumata L. (Lepidoptera: Geometridae), a polyphagous herbivore usually associated with deciduous trees such as oak Quercus robur L., has expanded its host range to include the evergreen species heather Calluna vulgaris (L.) Hull and, most recently, Sitka spruce Picea sitchensis (Bong.) Carrière. 2. Phenology, morphology, and survival of O. brumata were measured at several life-history stages in populations from the three different host plant communities sampled from a range of geographical locations. The data were used to test for population differences, reflecting the marked differences in host-plant secondary chemistry, growth form, and site factors such as climate. The hypothesis that spruce-feeding populations originated from populations feeding on moorland, commonly sites of coniferous afforestation, was also tested. 3. Altitude, not host plant species, was the major influence on the timing of adult emergence. An effect of insect population independent of altitude was found, implying that additional unidentified factors contribute to this phenological variation. Larval survival and adult size varied between populations reared on different host plant species. Survival of larvae was affected negatively when reared on the novel host plant, Sitka spruce, versus the natal plant (oak or heather) but oak and heather-sourced insects did not differ in survivorship on Sitka spruce. 4. Host range extension into novel environments has resulted in population differentiation to the local climate, demonstrating that host shifts pose challenges to the herbivore population greater than those offered by the host plant alone. The hypothesis that Sitka spruce feeding populations have arisen predominantly from moorland feeding populations was not supported. [source] A minimalist approach to the effects of density-dependent competition on insect life-history traitsECOLOGICAL ENTOMOLOGY, Issue 4 2002Philip Agnew Abstract ,1. Due to its effects on the phenotypic and genotypic expression of life-history traits, density-dependent competition is an important factor regulating the growth of populations. Specifically for insects, density-dependent competition among juveniles is often associated with increased juvenile mortality, delayed maturity, and reduced adult size. 2. The aim of the work reported here was to test whether the established phenotypic effects of density-dependent competition on life-history traits could be reproduced in an experimental design requiring a minimal number of individuals. Larvae of the mosquito Aedes aegypti were reared at densities of one, two, or three individuals per standard Drosophila vial and in six different conditions of larval food availability. This design required relatively few individuals per independent replicate and included a control treatment where individuals reared at a density of one larva per vial experienced no density-dependent interactions with other larvae. 3. Increased larval densities or reduced food availability led to increased larval mortality, delayed pupation, and the emergence of smaller adults that starved to death in a shorter time (indicating emergence with fewer nutritional reserves). 4. Female mosquitoes were relatively larger than males (as measured by wing length) but males tended to survive for longer. These differences increased as larval food availability increased, indicating the relative importance of these two traits for the fitness of each sex. The role of nutritional reserves for the reproductive success of males was highlighted in particular. 5. This minimalist approach may provide a useful model for investigating the effects of density-dependent competition on insect life-history traits. [source] Influence of atmospheric carbon dioxide enrichment on induced response and growth compensation after herbivore damage in Lotus corniculatusECOLOGICAL ENTOMOLOGY, Issue 3 2002Alain Bazin Abstract 1. Plant growth and chemical defence compounds in four Lotus corniculatus genotypes exposed to factorial combinations of ambient and elevated carbon dioxide, and herbivory by caterpillars of Polyommatus icarus were measured to test the predictions of the carbon/nutrient balance hypothesis. 2. Shoot and root biomass, allocation to shoots versus roots, and carbon-based defence compounds were greater under elevated carbon dioxide. Pupal weight of P. icarus was greater and development time shorter under elevated carbon dioxide. 3. Herbivory decreased shoot growth relative to root growth and production of nitrogen-based defence (cyanide). Young leaves contained more defence compounds than old leaves, and this response depended on carbon dioxide and herbivory treatments (significant interactions). 4. Genotype-specific responses of plants to carbon dioxide and herbivory were found for the production of cyanide. Furthermore, maternal butterfly-specific responses of caterpillars to carbon dioxide were found for development time. This suggests the existence of genetic variation for important defence and life-history traits in plants and herbivores in response to rising carbon dioxide levels. [source] Trade-offs and the evolution of life-histories during range expansionECOLOGY LETTERS, Issue 10 2010Olivia J. Burton Ecology Letters (2010) Abstract During range-advance, individuals on the expanding edge of the population face a unique selective environment. In this study, we use a three-trait trade-off model to explore the evolution of dispersal, reproduction and competitive ability during range expansion. We show that range expansion greatly affects the evolution of life-history traits due to differing selection pressures at the front of the range compared with those found in stationary and core populations. During range expansion, dispersal and reproduction are selected for on the expanding population front, whereas traits associated with fitness at equilibrium density (competitive ability) show dramatic declines. Additionally, we demonstrate that the presence of a competing species can considerably reduce the extent to which dispersal is selected upwards at an expanding front. These findings have important implications for understanding both the rate of spread of invasive species and the range-shifting dynamics of native species in response to climate change. [source] The promise and the potential consequences of the global transport of mycorrhizal fungal inoculumECOLOGY LETTERS, Issue 5 2006Mark W. Schwartz Abstract Advances in ecology during the past decade have led to a much more detailed understanding of the potential negative consequences of species' introductions. Moreover, recent studies of mycorrhizal symbionts have led to an increased knowledge of the potential utility of fungal inoculations in agricultural, horticultural and ecological management. The intentional movement of mycorrhizal fungal species is growing, but the concomitant potential for negative ecological consequences of invasions by mycorrhizal fungi is poorly understood. We assess the degree to which introductions of mycorrhizal fungi may lead to unintended negative, and potentially costly, consequences. Our purpose is to make recommendations regarding appropriate management guidelines and highlight top priority research needs. Given the difficulty in discerning invasive species problems associated with mycorrhizal inoculations, we recommend the following. First, careful assessment documenting the need for inoculation, and the likelihood of success, should be conducted prior to inoculation because inoculations are not universally beneficial. Second, invasive species problems are costly and often impossible to control by the time they are recognized. We recommend using local inoculum sources whenever possible. Third, non-sterile cultures of inoculum can result in the movement of saprobes and pathogens as well as mutualists. We recommend using material that has been produced through sterile culture when local inoculum is not available. Finally, life-history characteristics of inoculated fungi may provide general guidelines relative to the likelihood of establishment and spread. We recommend that, when using non-local fungi, managers choose fungal taxa that carry life-history traits that may minimize the likelihood of deleterious invasive species problems. Additional research is needed on the potential of mycorrhizal fungi to spread to non-target areas and cause ecological damage. [source] Phosphorus availability mediates plasticity in life-history traits and predator,prey interactions in DaphniaECOLOGY LETTERS, Issue 10 2005Punidan D. Jeyasingh Abstract We analysed growth plasticity of two Daphnia pulex clones under low-phosphorus (LP) and high phosphorus (HP) conditions, in the presence of Chaoborus kairomones to examine how food quality (P-availability) might impact life-history responses and vulnerability to predation. Overall, clone 1 grew faster, and was larger at maturity. Under HP, both clones responded to kairomones by increasing growth, age and size at maturity, and decreasing fecundity. Under LP, both clones suffered reduced growth, and fecundity. However, the magnitude of response to kairomones depended on a clone by P-availability interaction. Chaoborus presented a 1 : 1 clonal mixture under HP or LP, consumed more individuals under LP. Moreover, fewer clone 1 individuals were consumed. Studying the effects of P-availability on life histories, and predator,prey interactions may help us understand the mechanisms generating and maintaining plasticity, as well as influencing genotypic diversity and microevolutionary processes in natural populations. [source] Predicting competition coefficients for plant mixtures: reciprocity, transitivity and correlations with life-history traitsECOLOGY LETTERS, Issue 4 2001R.P. Freckleton There are few empirical or theoretical predictions of how per capita or per individual competition coefficients for pairs of plant species should relate to each other. In contrast, there are a considerable number of general hypotheses that predict competitive ability as a function of a range of ecological traits, together with a suite of increasingly sophisticated models for competitive interactions between plant species. We re-analyse a data set on competition between all pairwise combinations of seven species and show that competition coefficients relate strongly to differences between the maximum sizes, root allocation, emergence time and seed size of species. Regressions suggest that the best predictor of competition coefficients is the difference in the maximum size of species and that correlations of the other traits with the competition coefficients occur through effects on the maximum size. We also explore the patterns of association between coefficients across the competition matrix. We find significant evidence for coefficient reciprocity (inverse relationships between the interspecific coefficients for species pairs) and transitivity (numerically predictable hierarchies of competition between species) across competition matrices. These results therefore suggest simple null models for plant community structure when there is competition for resources. [source] | |||||||||||||||||||||||||||||||||||||