Population Life History Traits Research Articles

Life-History traits of Hollandichthys multifasciatus (Eigenmann & Norris, 1900) (Characiformes: Characidae) in coastal Atlantic Forest blackwater streams from Southeastern Brazil

Ecological and life history traits have been used to understand the basic ecology of fishes. This study aimed to examine the existence of plasticity in life history traits of populations of Hollandichthys multifasciatus in ten blackwater streams. This is an inseminating Characidae, endemic to the Atlantic coastal drainages of Brazil. Different aspects of the life-history of the species, such as mean length, sex ratio, absolute and relative fecundity, gonadosomatic index, condition factor, length-weight relationship and the growth parameter (b) of 185 specimens were studied during the period of low precipitation (June-September). Fish samples were obtained along a 100 m stretch of each stream, and some habitat variables recorded. ANOVA and Kruskal-Wallis tests indicated a similarity in most of the analyzed traits, with exception of the mean length of immatures, Gonadosomatic Index of mature males and condition factor of immatures and mature adults. Also, slope tests of the length-weight relationship were significantly different for immatures. The observed differences were attributed to heterogeneity in food availability and/or other site-specific factors, which may influence growth and/or breeding aspects among the studied localities. The approach used herein may improve understanding of trait plasticity under natural conditions, helping to understand fish-community responses to anthropogenic changes.

Spatial variation of life-history traits in Bulinus truncatus, the intermediate host of schistosomes, in the context of field application of niclosamide in C\xf4te d\u2019Ivoire

BackgroundControl of intermediate host snails using molluscicides for the control and/or elimination of schistosomiasis is a strategy in line with WHO recommendations. Niclosamide is the main chemical molluscicide recommended by WHO. However, except the immediate killing of the snail, the extent of the impact of the molluscicide application on the evolution of snail life-history traits, in relation to recolonization of treated sites is not well known. This study aimed to characterize the spatial variation of life-history traits of populations of the freshwater snail Bulinus truncatus, in relation to niclosamide spraying in the field.From 2016 to 2018, we conducted a trial, using niclosamide to control the intermediate host snails for interrupting the seasonal transmission of urinary schistosomiasis in northern and central Côte d’Ivoire. Five villages (sites) were considered, including three test and two control villages. In the test villages, the molluscicide was sprayed in habitats harboring B. truncatus snails three times a year (November, February–March and June). We sampled six B. truncatus populations: two populations from the control villages without any treatment; one collected before treatment and three sampled 2–3 months after treatment of the site with niclosamide. The snail populations were monitored for several life-history traits, including survival, growth, fecundity and hatchability, under laboratory conditions, over one generation (G1). We tested the population, region (North/Centre) and treatment status (treated/untreated) effects on the variation of the measured life-history traits and correlations between pairs of traits were estimated.ResultsOn the whole, the traits varied among populations. The risk of death was lower in northern populations compared to central ones. The age at first reproduction was reached earlier with a smaller size of snails in northern populations. Values of first reproduction features (size and fecundity) were lower in treated snail populations. The overall growth of untreated populations was higher than that of treated ones. The late fecundity and egg hatching were higher in northern than in central snails. At first reproduction, age was negatively correlated with some fecundity parameters. However, growth was positively associated with fecundity.ConclusionsOur study showed a spatial variation of life-history traits in B. truncatus snails. The mollusciciding seems to have led to the depression of some life-history traits in the snail populations. However, investigations should be carried out over several generations of snails to better clarify the impact of niclosamide on the evolution of the life-history traits.

Geographical variability in life-history traits of a midslope dogfish: the brier shark Deania calcea.

Deania calcea (n = 420) were collected from the catch of deep-water trawlers in the southern and eastern scalefish and shark fishery in southern Australia during the years 2008-2011. The total length (LT ) range varied between sexes, females being larger (n = 264; 280-1530 mm) than males (n = 156; 310-921 mm). The reproductive cycle in this population is non-continuous and asynchronous. The estimated LT at which 50% of males are mature is 807 mm and is 914 mm for females. Populations of D. calcea in higher latitudes appear to mature at a larger size than conspecifics in lower latitudes, in both the northern and southern hemispheres. Litters ranged from three to 10 embryos with a 1:1 sex ratio, but litter size does not increase with maternal LT . Deania calcea shows geographical variability in its biological parameters and gathering information on life-history traits of populations is vital to understand the trade-offs made by this species in response to environmental conditions and to predict intraspecific spatial differences. Such information is a basis for specific spatial management to protect populations from excessive fishing.

Ontogenetic phenomena, temporal aspect, and ecological factors in the successful invasion of round goby Neogobius melanostomus in the River Danube

Plasticity in life-history traits is thought to be one of the key factors that contribute to adaptation of invasive species to the novel environment at the beginning of an invasion. It has been found that round gobies Neogobius melanostomus from freshly invaded areas (invasion front) exhibit different life-history traits than individuals from core or central areas with well-established populations. The theory of alternative ontogeny and invasive potential predicts such differences. Nevertheless, it is difficult to distinguish between the effects of intrinsic ontogenetic phenomena and the effects of particular ecological factors on life-history traits of populations at various stages of invasion. Thus, the main aim of this study was to test the prediction that two sub-populations of round gobies from two habitats exposed to a different intensity of anthropogenic pressures in the River Danube, but at the same stage of invasion, will have significant differences in their reproductive parameters. Females from the relatively undisturbed habitat were predicted to have 1) larger oocytes, 2) lower absolute number of oocytes, and 3) lower real absolute fecundity. For two parameters (1 and 3), differences were statistically significant, as predicted. For parameter 2, the difference was as predicted, though not significant. Several studies suggest that changes in life-history traits observed over the progressing invasions of fishes are typical rather than accidental. They appear to be related to the stage of the invasion and closely associated with ontogenetic phenomena (the capability to generate alternative ontogenies). However, ecological factors also play an important role in this process. If the habitat is exposed to permanent disturbances, the established invasive population will probably keep the same life-history traits as at the beginning of the invasion.

Brazilian sandy beach macrofauna production: a review

The state of the art of the studies on the production of Brazilian sandy beach macrofauna was analyzed on the basis of the data available in the literature. For this purpose, the representativeness of the production dataset was examined by latitudinal distribution, degree of exposure and morphodynamic state of beaches, taxonomic groups, and methods employed. A descriptive analysis was, further, made to investigate the trends in production of the more representative taxonomic groups and species of sandy beach macrofauna. A total of 69 macrofauna annual production estimates were obtained for 38 populations from 25 studies carried out between 22º56'S and 32º20'S. Production estimates were restricted to populations on beaches located on the southern and southeastern Brazilian coast. Most of the populations in the dataset inhabit exposed dissipative sandy beaches and are mainly represented by mollusks and crustaceans, with a smaller number of polychaetes. The trends in production among taxonomic groups follow a similar pattern to that observed on beaches throughout the world, with high values for bivalves and decapods. The high turnover rate (P/B ratio) of the latter was due to the presence of several populations of the mole crab Emerita brasiliensis, which can attain high values of productivity, in the dataset. Most of the studies focus on the comparison of production and, especially, of P/B ratio according to life history traits in populations of the same species/taxonomic group. Despite the importance of life history-production studies, other approaches, such as the effect of man-induce disturbances on the macrofauna, should be undertaken in these threatened environments.

Sensitivity of marine systems to climate and fishing: Concepts, issues and management responses

Modern fisheries research and management must understand and take account of the interactions between climate and fishing, rather than try to disentangle their effects and address each separately. These interactions are significant drivers of change in exploited marine systems and have ramifications for ecosystems and those who depend on the services they provide. We discuss how fishing and climate forcing interact on individual fish, marine populations, marine communities, and ecosystems to bring these levels into states that are more sensitive to (i.e. more strongly related with) climate forcing. Fishing is unlikely to alter the sensitivities of individual finfish and invertebrates to climate forcing. It will remove individuals with specific characteristics from the gene pool, thereby affecting structure and function at higher levels of organisation. Fishing leads to a loss of older age classes, spatial contraction, loss of sub-units, and alteration of life history traits in populations, making them more sensitive to climate variability at interannual to interdecadal scales. Fishing reduces the mean size of individuals and mean trophic level of communities, decreasing their turnover time leading them to track environmental variability more closely. Marine ecosystems under intense exploitation evolve towards stronger bottom–up control and greater sensitivity to climate forcing. Because climate change occurs slowly, its effects are not likely to have immediate impacts on marine systems but will be manifest as the accumulation of the interactions between fishing and climate variability — unless threshold limits are exceeded. Marine resource managers need to develop approaches which maintain the resilience of individuals, populations, communities and ecosystems to the combined and interacting effects of climate and fishing. Overall, a less-heavily fished marine system, and one which shifts the focus from individual species to functional groups and fish communities, is likely to provide more stable catches with climate variability and change than would a heavily fished system.

Thermal responses to environmental constraints in two populations of the oviparous lizard Liolaemus bibronii in Patagonia, Argentina

Ectotherms change their thermoregulation behaviour according to the available temperatures, photoperiod, and radiation present in their local environment. The influences of the abiotic environment not only affect the body temperature but also most life history traits of populations. The thermal biology of one of the southernmost oviparous lizards, Liolaemus bibronii, was studied at high- and low-latitude sites in Patagonia, Argentina, following the methodology of Hertz et al. [1993. Evaluating temperature regulation by field-active ectotherms: the fallacy of the inappropriate question. Am. Nat. 142, 796–818]. Our results show that L. bibronii lives under thermal–environmental constraints, behaves as a moderate thermoregulator, and shows the lowest body temperature (28 °C) for oviparous liolaemids.

Heritability of dispersal rate and other life history traits in the Glanville fritillary butterfly

Knowing the variances and heritabilities (h(2)) of life history traits in populations living under natural conditions is necessary for a mechanistic understanding of respective evolutionary processes. I estimated heritabilities of several life history traits, including dispersal rate, body mass, age at first reproduction, egg mass, clutch size and lifetime reproductive success, in the Glanville fritillary butterfly (Melitaea cinxia) using parent-offspring regression. Experiments were conducted under field conditions in a large population cage (32 x 26 m). Heritability estimates ranged from zero to almost one and several were significantly different from zero. Body size for both sexes, female age at first reproduction and egg weight were all moderately to highly heritable, whereas heritabilities were low or non-existent in clutch size and lifetime egg production. Heritability estimates for dispersal rate varied between the sexes, so that dispersal was heritable from mother to her female offspring only. This finding is consistent with previous results showing that the F1 female but not male offspring of females that naturally established new populations in the field are significantly more dispersive than butterflies in old populations.

Rapid evolution in response to introduced predators I: rates and patterns of morphological and life-history trait divergence.

BackgroundIntroduced species can have profound effects on native species, communities, and ecosystems, and have caused extinctions or declines in native species globally. We examined the evolutionary response of native zooplankton populations to the introduction of non-native salmonids in alpine lakes in the Sierra Nevada of California, USA. We compared morphological and life-history traits in populations of Daphnia with a known history of introduced salmonids and populations that have no history of salmonid introductions.ResultsOur results show that Daphnia populations co-existing with fish have undergone rapid adaptive reductions in body size and in the timing of reproduction. Size-related traits decreased by up to 13 percent in response to introduced fish. Rates of evolutionary change are as high as 4,238 darwins (0.036 haldanes).ConclusionSpecies introductions into aquatic habitats can dramatically alter the selective environment of native species leading to a rapid evolutionary response. Knowledge of the rates and limits of adaptation is an important component of understanding the long-term effects of alterations in the species composition of communities. We discuss the evolutionary consequences of species introductions and compare the rate of evolution observed in the Sierra Nevada Daphnia to published estimates of evolutionary change in ecological timescales.

Life-history traits of Fossaria cubensis (Gastropoda: Lymnaeidae) under experimental exposure to Fasciola hepatica (Trematoda: Digenea).

The effect of exposing the lymnaeid snail Fossaria cubensis to the trematode Fasciola hepatica on the snail population's life-history traits was studied under laboratory conditions. Exposed individuals showed a lower survival rate than control snails, although from week 7 onward a slower decrease of this parameter in relation to the control group was observed. There were higher values of fecundity rate for the controls compared to the exposed group except during weeks 9, 10, 11 and 12, which was the time that followed the period when almost all of the infected snails died. Both the intrinsic and finite rates of natural increase were significantly higher for the control group, but exposed snails still attained a lower mean generation time. Age-specific trade-offs were found, mainly for the weekly increase in size versus the number of eggs per mass, the weekly increase in size versus the number of viable eggs per mass, the number of masses versus the hatching probability and the number of eggs versus the hatching probability. All these negative associations were significant for juveniles of both control and exposed snails and not for adults; however, exposed young individuals exhibited much higher values of the correlation coefficient than control animals.

Genetic variation and covariation among life history traits in populations of Acanthoscelides obtectus maintained on different hosts

AbstractWe explored the extent to which two populations of Acanthoscelides obtectus (Coleoptera: Bruchidae), maintained in the laboratory for about 60 generations on common bean (Phaseolus vulgaris) and chickpea (Cicer arietinum) seeds, differ genetically in life history traits. Using a half‐sib breeding design, we screened for genetic variation in oviposition preference for two hosts within both populations, and examined whether this variation is correlated with weevil pre‐adult (egg‐to‐adult viability and egg‐to‐adult developmental time) and adult (female fecundity and longevity) fitness components on these two hosts. Significant differences between the Phaseolus and Cicer population were detected in viability, developmental time and oviposition preference, but not in female fecundity and longevity. The absence of a significant population × host interaction in all traits, except for developmental time in males, indicates that the Cicer population has not attained the status of ‘host race’. The estimated narrow‐sense heritabilities within population within host plant were in the low‐to‐moderate level (range: 1%–79%), with an overall average of about 24%. Within the population maintained on the chickpeas we detected significant genetic correlations between female developmental time on chickpea seeds and preference for chickpeas. In the population maintained on the primary host of this weevil species (the ‘Phaseolus’ population) we found no significant preference/performance genetic correlations. Data are also presented on the genetic correlations of preference and performance across host seeds within both populations. These correlations are found to be positive for all traits in both populations, indicating the absence of trade‐offs in either performance or behavioural response that might impose selection for host specialization within populations.

Rapid evolution of life history traits in populations of Poa annua L.

AbstractTwo populations of Poa annua L., one from an irrigated area and one from a dry area, were studied to test the following hypothesis: different life cycles should be selected in habitats of contrasting mortality regime. Plants from the irrigated area exhibited a typical perennial habit (indeterminate growth and low reproductive effort) while those from the dry area showed traits characteristic of annuals (determinate growth, high reproductive effort and flowering synchrony) although total annuality was not achieved. The antagonism between growth and reproduction was expressed at the individual tiller level and was reflected in the life history traits of the populations. The characters studied exhibited a high broad sense heritability which is required for a rapid evolution of life cycles when selection pressures are strong. Different levels of constraints (ecological, evolutionary, physiological and developmental) have to be taken into account in order to understand this evolution.

OPTIMIZATION MODELS, QUANTITATIVE GENETICS, AND MUTATION.

The process of selection on a multivariate set of characters subject to functional constraints is considered from the points of view of both evolutionary optimization theory and quantitative genetics. Special attention is given to life-history characteristics. It is shown that, under suitable conditions (including weak selection), useful approximate formulas for the relations between the functional constraints and the additive genetic variance-covariance matrix can be derived. These can be used to show that the conditions for equilibrium under selection according to the two different approaches are approximately equivalent. Although large negative genetic correlations are to be expected between some pairs of life-history traits in populations at equilibrium under selection, in general some small negative genetic correlations and some positive genetic correlations will also be present. Thus, the observation of a positive genetic correlation between a pair of life-history traits does not necessarily refute the possibility of trade-offs among a multivariate set of traits that contains the pair in question. The relation between the pattern of functional constraints and the genetic correlations is often complex, and little insight into the former can be derived from the latter. The effects of mutations that lower the overall efficiency of resource utilization, thereby creating a positive component to the genetic covariances among life-history traits, are also considered for a specific model. Although such mutations can have a substantial effect on the form of the life history, extreme conditions seem to be needed for them to produce a large effect on the pattern of genetic correlations in a random-mating population. They can, however, cause the appearance of positive correlations following inbreeding, due to the exposure of deleterious recessive or partially recessive mutations. The analysis also suggests that the population means of individual components of a constrained multivariate system may often equilibrate at values that are far from the optima that would be attained if they were selected in isolation from the other members of the system.

HERITABLE LIFE HISTORY VARIATION IN WIDELY SEPARATED POPULATIONS OFMESOCYCLOPS EDAX(CRUSTACEA: COPEPODA)

Additive genetic variances were estimated for several life history traits of north temperate Michigan and subtropical Florida populations of the freshwater copepod Mesocyclops edax (Crustacea: Copepoda). Estimates were obtained by rearing animals at 25° C and using a paternal half sib design. Considerable additive genetic variance was revealed in female and male body sizes of the Florida population and in female and male maturation times in the Michigan population. Female maturation time and clutch size in the Florida population and female body size and clutch size in the Michigan population exhibited low additive genetic variance. These findings provide further evidence of substantial additive genetic variance in life history traits of natural populations. The contrasting trends in additive genetic variance underlying life history traits of these populations are interpreted as reflecting differences in the potential to respond to selection and possibly also the different selective regimes of the Michigan and Florida environments.

Population ecology of Psammobates oculifer in a semi-arid environment

We studied the ecology of Psammobates oculifer over 13 months near Kimberley, South Africa, to ascertain if the population's life history traits conform to chelonian patterns in arid environments. Capture rates were highest in spring and lowest in winter when environmental conditions were respectively most and least favourable for tortoise activity. Body condition did not change from autumn to spring, but reached lower values during the summer drought. Capture effort averaged 5 hours/tortoise, which corresponds closely to that of species with low population densities in arid regions. Population size structure was skewed towards adults, indicative of low recruitment and/or low juvenile survivorship. Females were larger and heavier than males, confirming sexual dimorphism in this species. Body size of cohorts scaled to annuli counts, indicating a close correspondence between body size and age. Telemetered adults deposited one or no growth ring in the year of study; consequently, annuli counts could underestimate adult age. Regression analyses showed that male and female growth rates did not differ, but males matured at a smaller size and younger age than females. The smallest male showing reproductive behaviour had 12 annuli and a shell volume of 157 cm3, while similar measures for females were 14 annuli and 185 cm3. The sex ratio of the population did not differ from 1:1 but the bias towards males in spring, and towards females in autumn, indicates that studies limited to particular seasons can misrepresent life history traits of populations. We concluded that the life history of P. oculifer conforms to chelonian patterns in arid regions.