Infection Causes Trade-Offs between Development and Growth in Larval Amphibians.

Spatial and temporal variation in length‐at‐age and environmental factors affecting variation in growth rate of juvenile Atlantic salmonSalmo salarwere studied using data from a long‐term study in the River Stjørdalselva, central Norway. Mean annual instantaneous growth rate among 1+ and 2+year juvenile Atlantic salmon varied between 0·59 and 1·50 g g−1 year−1and mean instantaneous daily growth rate of young‐of‐the‐year (YOY) varied between 0·013 and 0·033 g g−1 day−1. Between year variation in growth was larger than the within year intra‐watercourse spatial variation. For YOY and 1+year Atlantic salmon, a major part of the observed between year variation in growth rates was explained by variation in mean daily water discharge and spring temperature. For 2+year juvenile Atlantic salmon, mean daily water discharge and cohort density were the only variables to significantly explain variation in growth rates. A large part of the within water‐course spatial variation could not be explained by temperature variations and juvenile Atlantic salmon in the uppermost areas of the river, experiencing the lowest ambient temperatures during the growth period, displayed the highest growth rates. Within the baselines set by temperature, biotic and abiotic factors connected to water flow regime and variation in food availability are suggested to be a major determinants of the temporal and spatial variation in juvenile Atlantic salmon growth rates.

How demographic factors lead to variation or change in growth rates can be investigated using life table response experiments (LTRE) based on structured population models. Traditionally, LTREs focused on decomposing the asymptotic growth rate, but more recently decompositions of annual 'realized' growth rates using 'transient' LTREs have gained in popularity. Transient LTREs have been used particularly to understand how variation in vital rates translate into variation in growth for populations under long-term study. For these, complete population models may be constructed to investigate how temporal variation in environmental drivers affect vital rates. Such investigations have usually come down to estimating covariate coefficients for the effects of environmental variables on vital rates, but formal ways of assessing how they lead to variation in growth rates have been lacking. We extend transient LTREs to further partition the contributions from vital rates into contributions from temporally varying factors that affect them. The decomposition allows one to compare the resultant effect on the growth rate of different environmental factors, as well as density dependence, which may each act via multiple vital rates. We also show how realized growth rates can be decomposed into separate components from environmental and demographic stochasticity. The latter is typically omitted in LTRE analyses. We illustrate these extensions with an integrated population model (IPM) for data from a 26 years study on northern wheatears (Oenanthe oenanthe), a migratory passerine bird breeding in an agricultural landscape. For this population, consisting of around 50-120 breeding pairs per year, we partition variation in realized growth rates into environmental contributions from temperature, rainfall, population density and unexplained random variation via multiple vital rates, and from demographic stochasticity. The case study suggests that variation in first year survival via the unexplained random component, and adult survival via temperature are two main factors behind environmental variation in growth rates. More than half of the variation in growth rates is suggested to come from demographic stochasticity, demonstrating the importance of this factor for populations of moderate size.

Summary Variation in post‐natal growth rates is substantial among organisms and especially strong among latitudes because tropical and south temperate species typically have slower growth than north temperate relatives. Metabolic rate is thought to be a critical mechanism underlying growth rates after accounting for allometric effects of body mass. However, comparative tests on a large spatial scale are lacking, and the importance of metabolism for growth rates remains unclear both within and particularly across latitudes. Songbirds exhibit strong interspecific variation in growth rates across geographic space, although within latitudes an association between metabolic rate and growth rate has not always been observed. Moreover, the hypothesis that differences in growth rates across latitudes reflect underlying differences in metabolism is untested. Here, we investigate these possibilities across north temperate, south temperate and tropical study sites. Phylogenetic analyses showed that, for a given body mass, metabolic rates of north temperate nestlings were higher than tropical and south temperate species. Metabolic rates controlled for body mass correlated with post‐natal growth rates both within and among latitudes. Offspring body mass explained substantial residual variation in growth rates as expected under classic allometric theory. Our results suggest that variation in metabolic rates has an important influence on broad patterns of avian growth rates at a global scale. We suggest further studies that address the ecological and physiological costs and consequences of variation in metabolism and growth rates.

Whilst changes in freshwater assemblages along gradients of environmental stress have been relatively well studied, we know far less about intraspecific variation to these same stressors. A stressor common in fresh waters worldwide is leachates from terrestrial plants. Leachates alter the physiochemical environment of fresh waters by lowering pH and dissolved oxygen and also releasing toxic compounds such as polyphenols and tannins, all of which can be detrimental to aquatic organisms. We investigated how chronic exposure to Eucalyptus leaf leachate affected the growth and survival of juvenile southern pygmy perch (Nannoperca australis) collected from three populations with different litter inputs, hydrology and observed leachate concentrations. Chronic exposure to elevated leachate levels negatively impacted growth and survival, but the magnitude of these lethal and sublethal responses was conditional on body size and source population. Bigger fish had increased survival at high leachate levels but overall slower growth rates. Body size also varied among populations and fish from the population exposed to the lowest natural leachate concentrations had the highest average stress tolerance. Significant intraspecific variation in both growth and survival caused by Eucalyptus leachate exposure indicates that the magnitude (but not direction) of these stress responses varies across the landscape. This raises the potential for leachate-induced selection to operate at an among-population scale. The importance of body size demonstrates that the timing of leachate exposure during ontogeny is central in determining the magnitude of biological response, with early life stages being most vulnerable. Overall, we demonstrate that Eucalyptus leachates are prevalent and potent selective agents that can trigger important sublethal impacts, beyond those associated with more familiar fish kills, and reiterate that dissolved organic carbon is more than just an energy source in aquatic environments.

Sexual reproduction has been a central topic in evolutionary biology because of its many costs: why have organisms evolved sexual reproduction despite the many costs of sex? To answer the question, researchers have conducted laboratory experiments to measure population growth rates with and without sexual reproduction under a stressor. Here we show that a single episode of sexual reproduction can produce a large amount of variation in population growth rates under dual stressors by laboratory experiments of a green alga, Closterium peracerosum-strigosum-littorale complex. We observed the population dynamics of the alga under dual stressors and confirmed that high salinity and low pH decreased growth rates. By comparing parental and their hybrid F1 populations, we observed larger variations in growth rates of F1 populations (i.e., transgressive segregation) when pH was low. Interestingly, even when parental populations had negative growth rates, some F1 populations showed positive growth rates in severe environmental conditions due to the large variation in population growth. By utilizing the recently obtained genomic information of the alga, we conducted a gene ontology enrichment analysis and found that genes with copy number variations between parental strains were more frequently associated with pH stress-related terms than salt stress-related terms. Our results suggest that recombination and variation in the number of gene copies might produce large genetic variation in the F1 generation. This will be an important step toward a better understanding of evolution of sex and evolutionary rescue where rapid contemporary evolution prevents population extinction in changing environments.

A central goal of comparative plant ecology is to understand how functional traits vary among species and to what extent this variation has adaptive value. Here we evaluate relationships between four functional traits (seed volume, specific leaf area, wood density, and adult stature) and two demographic attributes (diameter growth and tree mortality) for large trees of 240 tree species from five Neotropical forests. We evaluate how these key functional traits are related to survival and growth and whether similar relationships between traits and demography hold across different tropical forests. There was a tendency for a trade-off between growth and survival across rain forest tree species. Wood density, seed volume, and adult stature were significant predictors of growth and/or mortality. Both growth and mortality rates declined with an increase in wood density. This is consistent with greater construction costs and greater resistance to stem damage for denser wood. Growth and mortality rates also declined as seed volume increased. This is consistent with an adaptive syndrome in which species tolerant of low resource availability (in this case shade-tolerant species) have large seeds to establish successfully and low inherent growth and mortality rates. Growth increased and mortality decreased with an increase in adult stature, because taller species have a greater access to light and longer life spans. Specific leaf area was, surprisingly, only modestly informative for the performance of large trees and had ambiguous relationships with growth and survival. Single traits accounted for 9-55% of the interspecific variation in growth and mortality rates at individual sites. Significant correlations with demographic rates tended to be similar across forests and for phylogenetically independent contrasts as well as for cross-species analyses that treated each species as an independent observation. In combination, the morphological traits explained 41% of the variation in growth rate and 54% of the variation in mortality rate, with wood density being the best predictor of growth and mortality. Relationships between functional traits and demographic rates were statistically similar across a wide range of Neotropical forests. The consistency of these results strongly suggests that tropical rain forest species face similar trade-offs in different sites and converge on similar sets of solutions.

Underlying physiological mechanisms of intraspecific variation in growth response to elevated CO2 concentration [CO2] were investigated using two spring wheat (Triticum aestivum L.) cultivars: Yitpi and H45. Leaf blade elongation rate (LER), leaf carbon (C), nitrogen (N) in the expanding leaf blade (ELB, sink) and photosynthesis (A) and C and N status in the last fully expanded leaf blade (LFELB, source) were measured. Plants were grown at ambient [CO2] (~384µmolmol-1) and elevated [CO2] (~550µmolmol-1) in the Australian Grains Free Air CO2 Enrichment facility. Elevated [CO2] increased leaf area and total dry mass production, respectively, by 42 and 53% for Yitpi compared with 2 and 13% for H45. Elevated [CO2] also stimulated the LER by 36% for Yitpi compared with 5% for H45. Yitpi showed a 99% increase in A at elevated [CO2] but no A stimulation was found for H45. There was a strong correlation (r2=0.807) between LER of the ELB and soluble carbohydrate concentration in LFELB. In ELB, the highest spatial N concentration was observed in the cell division zone, where N concentrations were 67.3 and 60.6mg g-1 for Yitpi compared with 51.1 and 39.2mg g-1 for H45 at ambient and elevated [CO2]. In contrast, C concentration increased only in the cell division and cell expansion zone of the ELB of Yitpi. These findings suggest that C supply from the source (LFELB) is cultivar dependent and well correlated with LER, leaf area expansion and whole-plant growth response to elevated [CO2].

In order to investigate the underlying physiological mechanism of intraspecific variation in plant growth and yield response to elevated CO2 concentration [CO2], seven cultivars of spring wheat (Triticum aestivum L.) were grown at either ambient [CO2] (~384μmolmol-1) or elevated [CO2] (700μmolmol-1) in temperature controlled glasshouses. Grain yield increased under elevated [CO2] by an average of 38% across all seven cultivars, and this was correlated with increases in both spike number (productive tillers) (r=0.868) and aboveground biomass (r=0.942). Across all the cultivars, flag leaf photosynthesis rate (A) increased by an average of 57% at elevated [CO2]. The response of A to elevated [CO2] ranged from 31% (in cv. H45) to 75% (in cv. Silverstar). Only H45 showed A acclimation to elevated [CO2], which was characterised by lower maximum Rubisco carboxylation efficiency, maximum electron transport rate and leaf N concentration. Leaf level traits responsible for plant growth, such as leaf mass per unit area (LMA), carbon (C), N content on an area basis ([N]LA) and the C:N increased at elevated [CO2]. LMA stimulation ranged from 0% to 85% and was clearly associated with increased [N]LA. Both of these traits were positively correlated with grain yield, suggesting that differences in LMA play an important role in determining the grain yield response to elevated [CO2]. Thus increased LMA can be used as a new trait to select cultivars for a future [CO2]-rich atmosphere.

Variation in growth among individuals and over time: A case study and simulation experiment involving tagged Antarctic toothfish

BackgroundTo improve our understanding of microbial systems, it is essential to refine the conceptual frameworks that connect microorganisms to their ecological functions. While trait-based approaches can provide nuanced perspectives on how microorganisms influence ecosystem processes, there is ongoing debate over the link between microbial taxonomic classifications and life history traits. Here, we integrate genomic, metagenomic, amplicon sequencing, and experimental (stable isotope probing) data to investigate the scaling of bacterial growth traits from individual taxa to complex assemblages and to identify specific taxonomic groups of soil bacteria that can be used as indicators of community-scale microbial growth.ResultsOur results revealed broadly different distributions of growth rates among bacterial phyla, including significantly different mean and median rates. This, in turn, manifested in strong relationships between relative abundances of some phyla and community-scale growth rates in soil. Specifically, we calculated community weighted mean growth rates using measured growth rates of constituent taxa and found that the fast-growing taxa that had sufficient abundance and ubiquity across samples to contribute to variation in community-average growth were mostly lineages of Proteobacteria (e.g., Sphingomonas). As a result, the relative abundance of phylum Proteobacteria was the single strongest taxonomic predictor of community-average growth, explaining up to ~ 60% of the variation in growth rates across communities. In contrast, Verrucomicrobia were consistent indicators of slower community-average growth. These patterns were especially strong when using taxon-level growth rates measured following carbon and nitrogen additions to soil.ConclusionsOur results demonstrate that phylum relative abundances can be strong indicators of community-level bacterial growth despite the wide variation in growth rates observed within phyla. The stronger phylum-growth relationships for whole assemblages than are apparent for individual taxa are due to relative abundance-weighted trait averaging in complex assemblages, i.e., at the community scale, broad differences in growth traits among phyla become more important than variation within phyla. Overall, our results provide clarity regarding the use of bacterial taxonomic information for inferring traits, demonstrating that high taxonomic ranks can be valid indicators of microbial traits in soil provided that inferences are drawn at the appropriate scale.Supplementary InformationThe online version contains supplementary material available at 10.1186/s40793-025-00790-7.

Variation among bird species in growth rates is traditionally attributed to differences in energy availability and developmental mode. However, the extent and form of competition among siblings for limited food resources may also be an important determinant. Kin-selection-based models of intrabrood competition suggest that nestling growth rates should be highest in those species in which siblings are likely to be less genetically related to one another (half-sibs rather than full-sibs). We test this novel prediction using the frequency of multiple paternity as an index of average sib relatedness within broods. As predicted, we find a significant positive association between the rate of multiple paternity within broods and nestling growth rates. Furthermore, this holds true when we control for the effects of variation in other factors that may be associated with variation in growth rate, such as body size, brood size, mating system and the form of parental care. We suggest, therefore, that variation in growth rate among bird species is not simply dependent on proximate ecological and developmental factors but is also strongly influenced by interactions, over an evolutionary time-scale, among kin.

The geographic variation in growth rate and resulting body size is poorly known for most fish species. In this paper, we used data derived from otoliths to describe patterns of growth in redside shiners Richardsonius balteatus from seven native populations across the southern portion of its range, and we compare growth with latitude, elevation, and growing season to determine which of these environmental factors best predicts the growth patterns among these populations. To determine whether observed differences in growth resulted from environmental or genetic variation, we conducted a common‐environment experiment on fish from three of the seven populations that showed contrasting patterns between latitude and length of growing season. Redside shiners exhibited about a 60% difference in size at age among populations in their natural environments. Growing season length was the best predictor of body size among these populations (Akaike weight = 0.78). In a common environment, temperature‐specific growth rates differed among populations, indicating that some of the observed differences in size at age among populations are genetically based. Although populations of redside shiners with shorter growing seasons exhibited higher field growth rates than expected, the pattern of variation in individual growth rates among populations in a common environment was not consistent with either a countergradient variation model or a local adaptation model of growth.

Comments on the paper of P. Gould

The reasons why growth and developmental rates vary widely among species have remained unclear. Previous examinations of possible environmental influences on growth rates of birds yielded few correlations, leading to suggestions that young may be growing at maximum rates allowed within physiological constraints. However, estimations of growth rates can be confounded by variation in relative developmental stage at fledging. Here, we re-estimate growth rates to control for developmental stage. We used these data to examine the potential covariation of growth and development with environmental variation across a sample of 115 North American passerines. Contrary to previous results, we found that growth rates of altricial nestlings were strongly positively correlated to daily nest predation rates, even after controlling for adult body mass and phylogeny. In addition, nestlings of species under stronger predation pressure remained in the nest for a shorter period, and they left the nest at lower body mass relative to adult body mass. Thus, nestlings both grew faster and left the nest at an earlier developmental stage in species with higher risk of predation. Growth patterns were also related to food, clutch size, and latitude. These results support a view that growth and developmental rates of altricial nestlings are strongly influenced by the environmental conditions experienced by species, and they generally lend support to an adaptive view of interspecific variation in growth and developmental rates.

The reasons why growth and developmental rates vary widely among species have remained unclear. Previous examinations of possible environmental influences on growth rates of birds yielded few correlations, leading to suggestions that young may be growing at maximum rates allowed within physiological constraints. However, estimations of growth rates can be confounded by variation in relative developmental stage at fledging. Here, we reestimate growth rates to control for developmental stage. We used these data to examine the potential covariation of growth and development with environmental variation across a sample of 115 North American passerines. Contrary to previous results, we found that growth rates of altricial nestlings were strongly positively correlated to daily nest predation rates, even after controlling for adult body mass and phylogeny. In addition, nestlings of species under stronger predation pressure remained in the nest for a shorter period, and they left the nest at lower body mass relative to adult body mass. Thus, nestlings both grew faster and left the nest at an earlier developmental stage in species with higher risk of predation. Growth patterns were also related to food, clutch size, and latitude. These results support a view that growth and developmental rates of altricial nestlings are strongly influenced by the environmental conditions experienced by species, and they generally lend support to an adaptive view of interspecific variation in growth and developmental rates.