Adaptive maternal investment in the wild? Links between maternal growth trajectory and offspring size, growth, and survival in contrasting environments

Life history theory predicts that investment per offspring should correlate negatively with the quality of environment offspring are anticipated to encounter; parents may use their own experience as juveniles to predict this environment and may modulate offspring traits such as growth capacity as well as initial size. We manipulated nutrient levels in the juvenile habitat of wild Atlantic salmon Salmo salar to investigate the hypothesis that the egg size maximizing juvenile growth and survival depends on environmental quality. We also tested whether offspring traits were related to parental growth trajectory. Mothers that grew fast when young produced more, smaller offspring than mothers that had grown slowly to reach the same size. Despite their size disadvantage, offspring of faster-growing mothers grew faster than those of slow-growing mothers in all environments, counter to the expectation that they would be competitively disadvantaged. However, they had lower relative survival in environments where the density of older predatory/competitor fish was relatively high. These links between maternal (but not paternal) growth trajectory and offspring survival rate were independent of egg size, underscoring that mothers may be adjusting egg traits other than size to suit the anticipated environment faced by their offspring

Cyprinodontiformes Adult Size & Offspring Size

Species-mean adult size and egg size (g) for Caudata

Perciformes Species & Reference List

List of references used to compile size data for Perciformes, with references specific to each specie

Anura Adult Size & Offspring Size

Species-mean adult size and egg size (g) for Anurans

Cyprinodontiformes Species & Reference List

List of references used to compile the size data for Cyprinodontiformes, with references listed for each species

Perciformes II Adult Size & Offspring Size

Species-mean adult size and offspring size (g) for "Perciformes II" datase

Perciformes I Adult Size & Offspring Size

Species-mean adult size and offspring size (g) for "Perciformes I" datase

Data from: Oxygen limitation at the larval stage and the evolution of maternal investment per offspring in aquatic environments

Many selective agents have been implicated in the evolution of maternal investment per offspring. Although oxygen limitation and surface-area-to-volume relationships were historically thought to constrain investment in individual eggs in aquatic environments, a weight of evidence now indicates that egg size per se does not influence oxygen availability to embryos. Yet, larval size is related to egg size, and hence investment per offspring, thus the scaling of oxygen assimilation efficiency with larval size may still constrain investment per offspring in aquatic environments. We employ comparative methods in the Amphibia to investigate this problem. We demonstrate that the slope of species-mean egg diameter over habitat temperature is negative for species with aquatic larvae, and the decline in egg size is similar whether eggs are laid terrestrially or aquatically. Further, the slope of egg diameter over temperature is more negative for species with aquatic larvae compared to species that feature terrestrial eggs and no larvae. Finally, we show that egg size declines with temperature more strongly for species whose larvae cannot breathe aerially prior to metamorphosis, compared to those that can. Our results suggest that oxygen transport in larvae, not eggs, constrains investment per offspring in aquatic systems. This study also helps reconcile conflicting reports that undermined the generality of temperature-dependent oxygen limitation as a mechanism driving the temperature-size rule in aquatic systems

Experimental evaluation of agonistic behaviour, chemical communication, spacing, and intersexual associations of the red-backed salamander (Plethodon cinereus) near its northern range limit

Territorial behaviour is the use of aggression and advertisement in the defense of a fixed area. In the red-backed salamander (Plethodon cinereus, Green, 1818), territoriality is prevalent in Virginia, near the southern extent of its range, but few studies have examined whether northern populations exhibit territorial behaviour. We tested for some prerequisites of territorial behaviour in P. cinereus at the northern extent its range, near North Bay, Ontario. In laboratory trials, we found that adult male P. cinereus exhibited a modest degree of aggression, and intruding salamanders attempted to escape the experimental chamber more often than residents. We also found that P. cinereus were able to differentiate between familiar and unfamiliar substrates, possibly suggesting pheromonal communication and a potential for territorial advertisement. However, while male-female pairs were common at six sampling sites during the mating season, adult salamanders consistently exhibited a random spatial distribution during the non-mating season. Our study suggests that local P. cinerues exhibit low-level aggression but may not defend fixed areas. One possibility is that P. cinereus may generally not benefit from territorial behaviour in cooler climates, as evapotranspiration rates will be lower and foraging activity less restricted compared to more southern climates.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Data from: Temperature-dependent oxygen limitation and the rise of Bergmann’s Rule in species with aquatic respiration

Bergmann’s Rule is the propensity for species-mean body size to decrease with increasing temperature. Temperature-dependent oxygen limitation has been hypothesized to help drive temperature–size relationships among ectotherms, including Bergmann’s Rule, where organisms reduce body size under warm oxygen-limited conditions, thereby maintaining aerobic scope. Temperature-dependent oxygen limitation should be most pronounced among aquatic ectotherms that cannot breathe aerially, as oxygen solubility in water decreases with increasing temperature. We use phylogenetically-explicit analyses to show that species-mean adult size of aquatic salamanders with branchial or cutaneous oxygen uptake becomes small in warm environments and large in cool environments, whereas body size of aquatic species with lungs (i.e., that respire aerially), as well as size of semi aquatic and terrestrial species do not decrease with temperature. We argue that oxygen limitation drives the evolution of small size in warm aquatic environments for species with aquatic respiration. More broadly, the stronger decline in size with temperature observed in aquatic vs terrestrial salamander species mirrors the relatively strong plastic declines in size observed previously among aquatic vs terrestrial invertebrates, suggesting that temperature-dependent oxygen availability can help drive patterns of plasticity, micro- and macroevolution