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145 results for “life history variation”

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dryad28/100

Data from: Seasonal time constraints reduce genetic variation in life history traits along a latitudinal gradient

1. Time constraints cause strong selection on life history traits, because populations need to complete their life cycles within a shorter time. We therefore expect lower genetic variation in these traits in high- than in low-latitude populations, since the former are more time constrained. 2. The aim was to estimate life history traits and their genetic variation in an obligately univoltine damselfly along a latitudinal gradient of 2,730 km. 3. Populations were grown in the laboratory at temperatures and photoperiods simulating those at their place of origin. In a complementary experiment individuals from the same families were grown in constant temperature and photoperiod that mimicked average conditions across the latitude. 4. Development time and size was faster and smaller, respectively, and growth rate was higher at northern latitudes. Additive genetic variance was very low for life history traits and estimates for egg development time and larval growth rate showed significant decreases towards northern latitudes. The expression of genetic effects in life history traits differed considerably when individuals were grown in constant rather than simulated and naturally variable conditions. 5. Our results support strong selection by time constraints. They also highlight the importance of growing organisms in their native environment for correct estimates of genetic variance at their place of origin. Our results also suggest that the evolutionary potential of life history traits is very low at northern compared to southern latitudes, but that changes in climate could alter this pattern.

opencc-zeroDec 2014View details →

dryad28/100

Data from: Antagonistic pleiotropy in species with separate sexes, and the maintenance of genetic variation in life-history traits and fitness

Antagonistic pleiotropy (AP) – where alleles of a gene increase some components of fitness at a cost to others – can generate balancing selection, and contribute to the maintenance of genetic variation in fitness traits, such as survival, fecundity, fertility, and mate competition. Previous theory suggests that AP is unlikely to maintain variation unless antagonistic selection is strong, or AP alleles exhibit pronounced differences in genetic dominance between the affected traits. We show that conditions for balancing selection under AP expand under the likely scenario that the strength of selection on each fitness component differs between the sexes. Our model also predicts that the vast majority of balanced polymorphisms have sexually antagonistic effects on total fitness, despite the absence of sexual antagonism for individual fitness components. We conclude that AP polymorphisms are less difficult to maintain than predicted by prior theory, even under our conservative assumption that selection on components of fitness is universally sexually concordant. We discuss implications for the maintenance of genetic variation, and for inferences of sexual antagonism that are based on sex-specific phenotypic selection estimates – many of which are based on single fitness components.

opencc-zeroDec 2017View details →

dryad28/100

Data from: Patterns and drivers of intraspecific variation in avian life history along elevational gradients: a meta-analysis

Elevational gradients provide powerful natural systems for testing hypotheses regarding the role of environmental variation in the evolution of life-history strategies. Case studies have revealed shifts towards slower life histories in organisms living at high elevations yet no synthetic analyses exist of elevational variation in life-history traits for major vertebrate clades. We examined (i) how life-history traits change with elevation in paired populations of bird species worldwide, and (ii) which biotic and abiotic factors drive elevational shifts in life history. Using three analytical methods, we found that fecundity declined at higher elevations due to smaller clutches and fewer reproductive attempts per year. By contrast, elevational differences in traits associated with parental investment or survival varied among studies. High-elevation populations had shorter and later breeding seasons, but longer developmental periods implying that temporal constraints contribute to reduced fecundity. Analyses of clutch size data, the trait for which we had the largest number of population comparisons, indicated no evidence that phylogenetic history constrained species-level plasticity in trait variation associated with elevational gradients. The magnitude of elevational shifts in life-history traits were largely unrelated to geographic (altitude, latitude), intrinsic (body mass, migratory status), or habitat covariates. Meta-population structure, methodological issues associated with estimating survival, or processes shaping range boundaries could potentially explain the nature of elevational shifts in life-history traits evident in this data set. We identify a new risk factor for montane populations in changing climates: low fecundity will result in lower reproductive potential to recover from perturbations, especially as fewer than half of the species experienced higher survival at higher elevations.

opencc-zeroDec 2014View details →

zenodo28/100

Fig. 6 in Life-history of the South American darter, Characidium pterostictum (Crenuchidae): evidence for small scale spatial variation in a piedmont stream

Fig. 6. Seasonal variation of mean condition factor (K) of Characidium pterostictum in the Lajeado river (southern Brazil). PA, upstream site; PB, downstream site. * In PA no specimen was captured in Summer.

opencc-by-4.0Dec 2008View details →

dryad28/100

Dataset for: Spatial and environmental effects on Coho Salmon life-history trait variation

<p>Adult size, egg mass, fecundity and mass of gonads are affected by trade-offs between reproductive investment and environmental conditions shaping the evolution of life-history traits among populations for widely distributed species. Coho salmon <i>Oncorhynchus kisutch</i> have a large geographic distribution and different environmental conditions are experienced by populations throughout their range. We examined the effect of environmental variables on female size, egg size, fecundity, and reproductive investment of populations of Coho Salmon from across British Columbia using an information theoretic approach. Female size increased with latitude and decreased with migration distance from the ocean to spawning locations. Egg size decreased with average intragravel temperature during incubation, migration distance, in larger rivers, but increased in rivers that were lake headed. Fecundity increased with latitude, warmer temperature during the spawning period, and river size, but decreased in rivers that were lake headed compared to rivers with tributary sources. Gonadal somatic index increased with latitude and decreased with migration distance. Latitude of spawning grounds, migratory distance and temperatures experienced by a population, but also hydrologic features – river size and headwater source – are influential in shaping patterns of reproductive investment, particularly egg size. The lack of an effect of latitude on egg size suggest that local optima for egg size may drive the positive relationship between egg number and latitude – a pattern that is partially off-set by larger female size and gonadal somatic index with latitude.</p>

opencc-zeroSep 2021View details →

dryad28/100