Correlative Changes in Life-History Variables in Response to Environmental Change in a Model Organism

Global change alters the environment, including increases in the frequency of (un)favorable events and shifts in environmental noise color. However, how these changes impact the dynamics of populations, and whether these can be predicted accurately has been largely unexamined. Here we combine recently developed population modeling approaches and theory in stochastic demography to explore how life history, morphology, and average fitness respond to changes in the frequency of favorable environmental conditions and in the color of environmental noise in a model organism (an acarid mite). We predict that different life-history variables respond correlatively to changes in the environment, and we identify different life-history variables, including lifetime reproductive success, as indicators of average fitness and life-history speed across stochastic environments. Depending on the shape of adult survival rate, generation time can be used as an indicator of the response of populations to stochastic change, as in the deterministic case. This work is a useful step toward understanding population dynamics in stochastic environments, including how stochastic change may shape the evolution of life histories

Predation risk increases in estuarine bivalves stressed by low salinity

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGSalinity drops in estuaries after heavy rains are expected to increase in frequency and intensity over the next decades, with physiological and ecological consequences for the inhabitant organisms. It was investigated whether low salinity stress increases predation risk on three relevant commercial bivalves in Europe. In laboratory, juveniles of Venerupis corrugata, Cerastoderma edule, and the introduced Ruditapes philippinarum were subjected to low salinities (5, 10 and control 35) during two consecutive days and, afterwards, exposed to one of two common predators in the shellfish beds: the shore crab Carcinus maenas and the gastropod Bolinus brandaris, a non-indigenous species present in some Galician shellfish beds. Two types of choice experiment were done: one offering each predator one prey species previously exposed to one of the three salinities, and the other offering each predator the three prey species at the same time, previously exposed to one of the three salinities. Consumption of both predators and predatory behaviour of C. maenas (handling time, rejections, consumption rate) were measured. Predation rates and foraging behaviour differed, with B. brandaris being more generalist than C. maenas. Still, both predators consumed significantly more stressed (salinity 5 and 10) than non-stressed prey. The overall consumption of the native species C. edule and V. corrugata was greater than that of R. philippinarum, likely due to their vulnerability to low salinity and physical traits (e.g., thinner shell, valve gape). Increasing precipitations can alter salinity gradients in shellfish beds, and thus affect the population dynamics of harvested bivalves via predator–prey interactions.Ministerio de Economía y Competitividad | Ref. CTM2014-51935-RMinisterio de Economía y Competitividad | Ref. BES-2015-074211Xunta de Galicia | Ref. GRC2013-00

General conclusion to the special issue Moving forward on individual heterogeneity

International audienc

Local Competition Between Foraging Relatives: Growth and Survival of Bruchid Beetle Larvae

Kin selection theory states that when resources are limited and all else is equal, individuals will direct competition away from kin. However, when competition between relatives is completely local, as is the case in granivorous insects whose larval stages spend their lives within a single seed, this can reduce or even negate the kin-selected benefits. Instead, an increase in competition may have the same detrimental effects on individuals that forage with kin as those that forage with non-kin. In a factorial experiment we assessed the effects of relatedness and competition over food on the survival and on fitness-related traits of the bruchid beetle Callosobruchus maculatus. Relatedness of competitors did not affect the survival of larvae. Larval survival substantially decreased with increasing larval density, and we found evidence that beetles maturing at a larger size were more adversely affected by competition, resulting in lower survival rates. Furthermore, females showed a reduction in their growth rate with increasing larval density, emerging smaller after the same development time. Males increased their growth rate, emerging earlier but at a similar size when food was more limited. Our results add to the growing number of studies that fail to show a relationship between relatedness and a reduction in competition between relatives in closed systems, and emphasize the importance of the scale at which competition between relatives occurs

DEBBIES Dataset to study Life Histories across Ectotherms

Abstract Demographic models are used to explore how life history traits structure life history strategies across species. This study presents the DEBBIES dataset that contains estimates of eight life history traits (length at birth, puberty and maximum length, maximum reproduction rate, fraction energy allocated to respiration versus reproduction, von Bertalanffy growth rate, mortality rates) for 185 ectotherm species. The dataset can be used to parameterise dynamic energy budget integral projection models (DEB-IPMs) to calculate key demographic quantities like population growth rate and demographic resilience, but also link to conservation status or biogeographical characteristics. Our technical validation shows a satisfactory agreement between observed and predicted longevity, generation time, age at maturity across all species. Compared to existing datasets, DEBBIES accommodates (i) easy cross-taxonomical comparisons, (ii) many data-deficient species, and (iii) population forecasts to novel conditions because DEB-IPMs include a mechanistic description of the trade-off between growth and reproduction. This dataset has the potential for biologists to unlock general predictions on ectotherm population responses from only a few key life history traits

Data from: Life-history differences favor evolution of male dimorphism in competitive games

Many species exhibit two discrete male morphs: fighters and sneakers. Fighters are large and possess weapons but may mature slowly. Sneakers are small and have no weapons but can sneak matings and may mature quickly to start mating earlier in life than fighters. However, how differences in competitive ability and life history interact to determine male morph coexistence has not yet been investigated within a single framework. Here we integrate demography and game theory into a two-sex population model to study the evolution of strategies that result in the coexistence of fighters and sneakers. We incorporate differences in maturation time between the morphs and use a mating-probability matrix analogous to the classic hawk-dove game. Using adaptive dynamics, we show that male dimorphism evolves more easily in our model than in classic game theory approaches. Our results also revealed an interaction between life-history differences and sneaker competitiveness, which shows that demography and competitive games should be treated as interlinked mechanisms to understand the evolution of male dimorphism. Applying our approach to empirical data on bulb mites (Rhizoglyphus robini), coho salmon (Oncorhynchus kisutch), and bullhorned dung beetles (Onthophagus taurus) indicates that observed occurrences of male dimorphism are in general agreement with model predictions