To improve the ecological functioning of riverine ecosystems, large‐scale floodplain rehabilitation has been carried out in the Rhine–Meuse Delta since the 1990s. This paper evaluates changes in ...abundance of 93 breeding bird species over a period of 10 years in response to rehabilitation, by comparing population changes in 75 rehabilitated sites with 124 non‐rehabilitated reference sites. Such quantitative, multi‐species, large‐scale and long‐term evaluations of floodplain rehabilitation on biodiversity are still scarce, particularly studies that focus on the terrestrial component. We try to understand the effects by relating population trends to ecological and life‐history traits and strategies of breeding birds. More specifically, we try to answer the question whether rehabilitation of vegetation succession or hydro‐geomorphological river processes is the key driver behind recent population changes in rehabilitated sites. Populations of 35 species have significantly performed better in rehabilitated sites compared to non‐rehabilitated floodplains, whereas only 8 have responded negatively to rehabilitation. Differences in effects between species are best explained by the trait selection of nest location. Reproductive investment and migratory behaviour were less strong predictors. Based on these three traits we defined eight life‐history strategies that successfully captured a substantial amount of variation in rehabilitation effects. We conclude that spontaneous vegetation succession and initial excavations are currently more important drivers of population changes than rehabilitation of hydrodynamics. The latter are strongly constrained by river regulation. If rehabilitation of hydro‐geomorphological processes remains incomplete in future, artificial cyclic floodplain rejuvenation will be necessary for sustainable conservation of characteristic river birds.
In the Iberian endemic loach Cobitis paludica, in a small seasonal tributary of the Guadalquivir River, 65–70% of the total growth in length occurred in the first year of life. The maximum ages ...observed were 3+ years in males and 4+ years in females. Both sexes matured at the beginning of their second year of life. There was a significant difference from 1: 1 in the overall sex ratio of 412 males to 674 females. Spawning began in late March and ended in July. Cobitis paludica is a multiple spawner that releases a minimum of two batches of eggs per female each year. Once spawning had started, however, there was no recruitment from the stock of transparent oocytes to the mature stock. The number of eggs decreased from the first batch to the second, but there was no significant difference in the mean egg diameter between batches. Compared with other populations of this species, the present population, from a low latitude, is characterized by a low number of age groups, fast growth, early maturity and high fecundity in multiple spawnings. These life‐history characteristics are typical of species in unstable environments, where adult mortality is high, variable or unpredictable.
Microarthropods show considerable small-scale spatial variation, which on statistical grounds demands the use of numerous samples per experimental unit to obtain a representative density estimate. To ...avoid the identification of all individuals in these samples a sub-sampling technique is desirable. Due to various factors, existing sub-sampling methods perform sub-optimally when working with soil microarthropods. As an alternative, this study evaluated a gel-based sub-sampling method. The method was applied in a practical situation comparing effects of two existing methods of slurry manure application (injection of control slurry and the superficial application of slurry to which an additive was added) on soil inhabiting springtails and mites. In the experiment, special attention was paid to the mediating influence of soil organic matter content.
The gel-based sub-sampling data showed a Poisson distribution, supporting randomness. Furthermore, none of the identified specimens showed morphological damage, strongly suggesting that neither gel-suspension nor amylase treatment had damaged the integuments of the specimens. Therefore, gel-based sub-sampling seems to offer an efficient and safe tool for sub-sampling microarthropods. Of the two slurry applications studied, the surface application of the slurry manure with the additive resulted in the highest abundances of microarthropods, with an average of 17,890
individuals
m
−2 in broadcasted fields, compared to 11,486
individuals
m
−2 in the slit injected fields. A positive correlation between microarthropod abundance and the organic matter content of the soil was found for the fields that were slit injected with unamended slurry. The specially prepared slurry treatment did not show the latter correlation, probably because of the
a priori relatively high organic matter content of most fields receiving this treatment. The relative dominance of surface dwelling species in the superficially applied slurry with additive suggests that the microarthropods responded in particular to the method of slurry manure application rather than to slurry manure type.
In the Iberian endemic loach Cobitis paludica, in a small seasonal tributary of the Guadalquivir River, 65-70% of the total growth in length occurred in the first year of life. The maximum ages ...observed were 3+ years in males and 4+ years in females. Both sexes matured at the beginning of their second year of life. There was a significant difference from 1 : 1 in the overall sex ratio of 412 males to 674 females. Spawning began in late March and ended in July. Cobitis paludica is a multiple spawner that releases a minimum of two batches of eggs per female each year. Once spawning had started, however, there was no recruitment from the stock of transparent oocytes to the mature stock. The number of eggs decreased from the first batch to the second, but there was no significant difference in the mean egg diameter between batches. Compared with other populations of this species, the present population, from a low latitude, is characterized by a low number of age groups, fast growth, early maturity and high fecundity in multiple spawnings. These life-history characteristics are typical of species in unstable environments, where adult mortality is high, variable or unpredictable. Copyright 2002 The Fisheries Society of the British Isles
Examiner les liens existant entre la variabilité environnementale, les traits d'histoire de vie, la dispersion et les décisions d'accouplement est un enjeu central en Ecologie et en Evolution. J'ai ...exploré ces questions chez un amphibien, le sonneur à ventre jaune (Bombina variegata). Dans le premier volet de ma thèse, je me suis intéressé à l'influence des variations spatiotemporelles de l'environnement sur les patrons de covariation entre les traits d'histoire de vie, la dispersion et les types comportementaux à l'échelle inter-populationnelle. J'ai examiné comment le degré de stochasticité interannuel de l'habitat de reproduction régule le positionnement des populations le long du slow-fast continuum et génère des syndromes de dispersion parmi les populations. J'ai ensuite analysé les conséquences de ces syndromes sur les patrons de différenciation génétique au sein des populations. Dans le second volet de ma thèse, je me suis intéressé au rôle de la canalisation environnementale dans la stratégie d'histoire de vie de B. variegata et j'ai évalué comment diverses formes de variations météorologiques pouvaient affecter la dynamique de différentes populations. Dans chacune d'elles, j'ai mesuré l'impact de facteurs météorologiques sur des paramètres démographiques tels que la survie, le recrutement et les probabilités de reproduction. Dans le troisième et dernier volet de ma thèse, je me suis intéressé au choix d'accouplement des femelles, en examinant successivement les hypothèses de bons gènes et de gènes compatibles puis en me focalisant sur le rôle de la qualité et de la disponibilité des sites de reproduction sur les décisions d'accouplement des femelles
Investigating the links between environmental variability and life history traits, dispersal and breeding decisions is critical challenge for ecologists. I have examined this issue in anuran, the yellow-bellied toad (Bombina variegata). In the first part of my thesis, I have examined the influence of spatio-temporal variation of the environment on the covariation patterns between life history traits, dispersal and behavioral types at inter-population scale. I have investigated how the level of breeding habitat stochasticity may regulate the position of B. variegata populations along the slow-fast continuum and may promote dispersal syndromes among populations. Then I have analyzed the consequence of such dispersal syndromes on population genetic differentiation. In the second part of my thesis, I have focused on the role of the environmental canalization in the life history strategy of B. variegata and I have evaluated how various forms of weather variation (mean and extreme events) could affect the dynamics of different populations. In each studied populations, I have quantified the impacts of weather variation on various demographic parameters as survival, recruitment and breeding probabilities. In the third part of my thesis, I have investigated female mate choice in B. variegata by successively examining good genes and compatible gene hypotheses, and then by evaluating the role of breeding habitat quality and availability on mating decisions
Introduced Gambusia holbrooki in a natural lagoon of southern Spain consisted of two age groups: 1992 cohort, 7‐11 months old and 1993 cohort, <4 months old. In the 1992 cohort, females grew even ...during the gestation period at about 0·30 mm day‐1. In the 1993 cohort, females displayed a high growth rate (0·55 mm day‐1) and reached reproductive size in a few weeks, but stopped growing when they matured. All the 1992 cohort reproduced from mid‐May to mid‐June, but only 50% of the 1993 cohort reproduced, from mid‐August to mid‐September. Reproducing females were significantly larger in the 1992 cohort (39·8 mm) than in the 1993 one (34·8 mm). The largest 1992 females cohort had reproduced previously; the 1993 cohort had not. The mean dry weight of intra‐ovarian embryos decreased to a minimum immediately before birth. These metabolic costs represented 29·8 and 31·4% of the initial weights of the 1992 and 1993 embryos, respectively. Mean dry weight of full‐term embryo was significantly higher in the 1992 cohort (0·80 ± 0·129 mg; 95% CL) than in the 1993 one (0·70 ± 0·086 mg; 95% CL). With more females in 1992, cohort fecundity was considerably higher (number of embryos=7151; 63%) than in the 1993 (4193; 37%) cohort. The population completed two generations each year (spring and summer). The spring stock grew slower than the summer one but continued to grow during the gestation period, reaching larger final lengths, with more synchronous reproduction and clearer evidence of a second reproductive event. Each reproductive stock displayed its own life‐history characteristics, with significant differences between mean length of reproducing females, growth rate, mean brood size, offspring size, standard fecundity and minimum length at reproduction.
The breeding phenology of temperate woodlice is strongly seasonal, the result of physiological constraints and precise environmental cues for reproduction. The adaptive value of such mechanisms is ...that the release of offspring coincides with favourable conditions for growth and survival (Willows 1984). We recorded the breeding phenology of Armadillidium vulgare (Latreille) on two grassland sites in Great Britain and found between-site and between-year variation in the onset of reproduction, the duration of reproductive activity, the release of offspring, the size of reproductive females and the number of broods per female. Between 82.7 and 97.7% of gravid females sampled were semelparous at 23 months, with the remainder iteroparous, producing a second brood after 35 months. On one site (Weeting Heath) improved growth conditions during 1984 allowed some females (19.3% of gravid females sampled in that year) to produce a brood after 11 months. There was also an increase in the number of 3-year-old females found to be gravid. An experimental manipulation of the same habitat confirmed that such changes in life history tactics could be phenotypic responses. The observed phenotypic variation was sufficient to produce a range of life history tactics within a population. Mixtures of life history tactics within a population may be typical of invasive species and populations at the edge of the species range. Our results support the idea that phenotypic plasticity can be an appropriate tactic to maximise fitness in a fluctuating environment (Caswell 1983, 1989).
Measurements of reproductive allocation, fertility and iteroparity were made on females of four species of woodlice (Isopoda: Oniscidae) from southern Africa. In three of the species ...between-population comparisons were made. The average body mass of reproductive females was smaller than in temperate woodlice and because of a positive scaling between body mass and fertility: brood sizes were rarely larger than 30 young and usually between 5 and 20. Reproductive allocation ranged from 16 to 27% of female pre-birth live mass and differed significantly between species. Associations between reproductive allocation and body mass were all positive although only significant in two of the populations. A small number of females produced more than one brood during the study and iteroparity appears the most likely reproductive tactic in these species. In woodlice a restriction on body size results in lower fecundity as brood size is ultimately determined by the size of the marsupium. It is postulated that a tactic of repeated reproduction, with a relatively conservative allocation of resources to each reproductive event to enhance survival probabilities, would be favoured, particularly in an environment where juvenile mortality and the chance of complete brood failure is high.
Most salmonid taxa have an anadromous life history strategy, whereby fish migrate to saltwater habitats for a growth period before returning to freshwater habitats for spawning. Moreover, several ...species are characterized by different life history tactics whereby resident and anadromous forms may occur in genetically differentiated populations within a same species, as well as polymorphism within a population. The molecular mechanisms underlying the physiological differences between anadromous and resident forms during the first transition from freshwater to saltwater environments are only partially understood. Insofar research has typically focused on species of the genus Salmo. Here, using a 16,000 cDNA array, we tested the hypothesis that anadromous brook charr Salvelinus fontinalis are characterized by differences in their transcriptome relative to resident brook charr before the anadromous fish migration. Families originating from parapatric populations of anadromous and resident charr were reared in controlled environments mimicking natural temperature and photoperiod, and sampled in spring, while still in fresh water. While anadromous and resident charr showed similar transcriptome profiles in white muscle, they were characterized by striking differences in their gill transcriptome profiles. Genes that were upregulated in the gills of anadromous charr were principally involved in metabolism (mitochondrial electron transport chain, glucose metabolism, and protein synthesis), development (tissue differentiation) and innate immunity. We discuss the nature of these transcriptomic differences in relation to molecular mechanisms underlying the expression of anadromous and resident life history tactics and suggest that the anadromous charr express some of the molecular processes present in other migratory salmonids Current Zoology 58 (1): 158–170, 2012.
