Spatiotemporal variations in density and biomass of rocky reef fish in a biogeographic climatic transition zone: trends over 9 years,inside and outside the only nearshore no-take marine-protected area on the southern Brazilian coast

Biogeographical transition zones are important areas to investigate evolutionary ecological questions, but long-term population monitoring is needed to better understand ecological processes that govern population variations in such edge environments. The southernmost Brazilian rocky reefs are the southern limit of distribution for 96% of the tropical ichthyofauna of the western Atlantic. The Arvoredo Marine Biological Reserve is the only nearshore no-take marine-protected area (MPA) located in this transition zone. The main aim was to investigate how the populations of rocky reef fish species vary in density and biomass in space and over time, inside and outside the Arvoredo MPA. This study presents results based on a 9 year (2008–2017) underwater visual census monitoring study to evaluate the density and biomass of key fish species. Variations in density and biomass were detected for most species. Factors and mechanisms that may have influenced spatial variation are habitat structural complexity and protection from fisheries. Temporal variations, otherwise, may have been influenced by species proximity to their distributional limit, in synergy with density-dependent mechanisms and stochastic winter temperature oscillations. The MPAs harbour higher density and biomass for most species. Nonetheless, a prominent temporal decline in the recruitment of Epinephelus marginatus calls into question the continuous effectiveness of the MPA.     

Divergent natural selection drives the evolution of reproductive isolation in an Australian wildflower

Ecological speciation occurs when reproductive isolation evolves between populations adapting to contrasting environments. A key prediction of this process is that the fitness of hybrids between divergent populations should be reduced in each parental environment as a function of the proportion of local genes they carry, a process resulting in ecologically dependent reproductive isolation (RI). To test this prediction, we use reciprocal transplant experiments between adjacent populations of an Australian wildflower, Senecio lautus, at two locations to distinguish between ecologically dependent and intrinsic genetic reproductive barriers. These barriers can be distinguished by observing the relative fitness of reciprocal backcross hybrids, as they differ in the contribution of genes from either parent while controlling for any intrinsic fitness effects of hybridization. We show ecologically dependent fitness effects in establishment and survival of backcrosses in one transplant experiment, and growth performance in the second transplant experiment. These results suggest natural selection can create strong reproductive barriers that maintain differentiation between populations with the potential to interbreed, and implies a significant role for ecology in the evolutionary divergence of S. lautus.     

Quantitative genetic parameters for wild stream‐living brown trout: heritability and parental effects

Adaptability depends on the presence of additive genetic variance for important traits. Yet few estimates of additive genetic variance and heritability are available for wild populations, particularly so for fishes. Here, we estimate heritability of length‐at‐age for wild‐living brown trout (Salmo trutta), based on long‐term mark‐recapture data and pedigree reconstruction based on large‐scale genotyping at 15 microsatellite loci. We also tested for the presence of maternal and paternal effects using a Bayesian version of the Animal model. Heritability varied between 0.16 and 0.31, with reasonable narrow confidence bands, and the total phenotypic variance increased with age. When introducing dam as an additional random effect (accounting for c. 7% of total phenotypic variance), the level of additive genetic variance and heritability decreased (0.12–0.21). Parental size (both for sires and for dams) positively influenced length‐at‐age for juvenile trout – either through direct parental effects or through genotype‐environment correlations. Length‐at‐age is a complex trait reflecting the effects of a number of physiological, behavioural and ecological processes. Our data show that fitness‐related traits such as length‐at‐age can retain high levels of additive genetic variance even when total phenotypic variance is high.     

Ecology and mode-of-life explain lifespan variation in birds and mammals

Maximum lifespan in birds and mammals varies strongly with body mass such that large species tend to live longer than smaller species. However, many species live far longer than expected given their body mass. This may reflect interspecific variation in extrinsic mortality, as life-history theory predicts investment in long-term survival is under positive selection when extrinsic mortality is reduced. Here, we investigate how multiple ecological and mode-of-life traits that should reduce extrinsic mortality (including volancy (flight capability), activity period, foraging environment and fossoriality), simultaneously influence lifespan across endotherms. Using novel phylogenetic comparative analyses and to our knowledge, the most species analysed to date (n = 1368), we show that, over and above the effect of body mass, the most important factor enabling longer lifespan is the ability to fly. Within volant species, lifespan depended upon when (day, night, dusk or dawn), but not where (in the air, in trees or on the ground), species are active. However, the opposite was true for non-volant species, where lifespan correlated positively with both arboreality and fossoriality. Our results highlight that when studying the molecular basis behind cellular processes such as those underlying lifespan, it is important to consider the ecological selection pressures that shaped them over evolutionary time.     

Heterozygosity-fitness correlations in a migratory bird: an analysis of inbreeding and single-locus effects

Studies in a multitude of taxa have described a correlation between heterozygosity and fitness and usually conclude that this is evidence for inbreeding depression. Here, we have used multilocus heterozygosity (MLH) estimates from 15 microsatellite markers to show evidence of heterozygosity-fitness correlations (HFCs) in a long-distance migratory bird, the light-bellied Brent goose. We found significant, positive heterozygosity-heterozygosity correlations between random subsets of the markers we employed, and no evidence that a model containing all loci as individual predictors in a multiple regression explained significantly more variation than a model with MLH as a single predictor. Collectively, these results lend support to the hypothesis that the HFCs we have observed are a function of inbreeding depression. However, we do find that fitness correlations are only detectable in years where population-level productivity is high enough for the reproductive asymmetry between high and low heterozygosity individuals to become apparent. We suggest that lack of evidence of heterozygosity-fitness correlations in animal systems may be because heterozygosity is a poor proxy measure of inbreeding, especially when employing low numbers of markers, but alternatively because the asymmetries between individuals of different heterozygosities may only be apparent when environmental effects on fitness are less pronounced.     

Host–parasite coevolution: genetic variation in a virus population and the interaction with a host gene

Host–parasite coevolution is considered to be an important factor in maintaining genetic variation in resistance to pathogens. Drosophila melanogaster is naturally infected by the sigma virus, a vertically transmitted and host‐specific pathogen. In fly populations, there is a large amount of genetic variation in the transmission rate from parent to offspring, much of which is caused by major‐effect resistance polymorphisms. We have found that there are similarly high levels of genetic variation in the rate of paternal transmission among 95 different isolates of the virus as in the host. However, when we examined a transmission‐blocking gene in the host, we found that it was effective across virus isolates. Therefore, the high levels of genetic variation observed in this system do not appear to be maintained because of coevolution resulting from interactions between this host gene and parasite genes.     

The influence of phylogeny and life history on telomere lengths and telomere rate of change among bird species: A meta‐analysis

Longevity is highly variable among animal species and has coevolved with other life‐history traits, such as body size and rates of reproduction. Telomeres, through their erosion over time, are one of the cell mechanisms that produce senescence at the cell level and might even have an influence on the rate of aging in whole organisms. However, uneroded telomeres are also risk factors of cell immortalization. The associations of telomere lengths, their rate of change, and life‐history traits independent of body size are largely underexplored for birds. To test associations of life‐history traits and telomere dynamics, we conducted a phylogenetic meta‐analysis using studies of 53 species of birds. We restricted analyses to studies that applied the telomere restriction fragment length (TRF) method, and examined relationships between mean telomere length at the chick (Chick TL) and adult (Adult TL) stages, the mean rate of change in telomere length during life (TROC), and life‐history traits. We examined 3 principal components of 12 life‐history variables that represented: body size (PC1), the slow–fast continuum of pace of life (PC2), and postfledging parental care (PC3). Phylogeny had at best a small‐to‐medium influence on Adult and Chick TL (r ² = .190 and .138, respectively), but a substantial influence on TROC (r ² = .688). Phylogeny strongly influenced life histories: PC1 (r ² = .828), PC2 (.838), and PC3 (.613). Adult TL and Chick TL were poorly associated with the life‐history variables. TROC, however, was negatively and moderate‐to‐strongly associated with PC2 (unadjusted r = −.340; with phylogenetic correction, r = −.490). Independent of body size, long‐lived species with smaller clutches, and slower embryonic rate of growth may exhibit less change in telomere length over their lifetimes. We suggest that telomere lengths may have diverged, even among closely avian‐related species, yet telomere dynamics are strongly linked to the pace of life.