When limited availability of data meets with a thorough meta-analysis: A comment on Moore et al.

Peer Reviewe

The relationship between syllable repertoire similarity and pairing success in a passerine bird species with complex song

Repertoire size, i.e. the number of unique song elements that an individual possesses, is thought to be an important target of female preference. However, the use of repertoire size reflects how researchers work with complex songs; while it does not necessary describe biological functions, as listeners of song may also rely on song composition. Specific syllables may have coherent consequences for mate attraction because they are costly to produce, mediate syllable sharing or indicate the dialect of origin. We tested for the relationship between song composition and pairing success in the collared flycatcher (Ficedula albicollis). We applied a tree-clustering method to hierarchically classify males based on the degree of repertoire overlap, and then used a phylogenetic approach to assess the degree by which pairing speed matches the hierarchically structured song data. We found that males using similar syllables also find a breeding partner at a similar speed. Partitioning the variance components of pairing speed, we detected that the consequences of particular syllables for mating are repeatable across males. When assessing the role of repertoire similarity in mediating direct syllable sharing, we derived a positive relationship between the physical distance between pairs of males and their repertoire overlap implying that neighboring males avoid copying each other's song. Finally, we were unable to demonstrate that syllables related to higher mating success are more common in the population, which would support mechanisms based on female preference for local songs. Our results imply that individual-specific song organization may be relevant for sexual selection. © 2011 Elsevier Ltd.Peer Reviewe

Correlated evolution of nucleotide substitution rates and allelic variation in Mhc-DRB lineages of primates

<p>Abstract</p> <p>Background</p> <p>The major histocompatibility complex (MHC) is a key model of genetic polymorphism. Selection pressure by pathogens or other microevolutionary forces may result in a high rate of non-synonymous substitutions at the codons specifying the contact residues of the antigen binding sites (ABS), and the maintenance of extreme MHC allelic variation at the population/species level. Therefore, selection forces favouring MHC variability for any reason should cause a correlated evolution between substitution rates and allelic polymorphism. To investigate this prediction, we characterised nucleotide substitution rates and allelic polymorphism (i.e. the number of alleles detected in relation to the number of animals screened) of several <it>Mhc </it>class II <it>DRB </it>lineages in 46 primate species, and tested for a correlation between them.</p> <p>Results</p> <p>First, we demonstrate that species-specific and lineage-specific evolutionary constraints favour species- and lineage-dependent substitution rate at the codons specifying the ABS contact residues (i.e. certain species and lineages can be characterised by high substitution rate, while others have low rate). Second, we show that although the degree of the non-synonymous substitution rate at the ABS contact residues was systematically higher than the degree of the synonymous substitution rate, these estimates were strongly correlated when we controlled for species-specific and lineage-specific effects, and also for the fact that different studies relied on different sample size. Such relationships between substitution rates of different types could even be extended to the non-contact residues of the molecule. Third, we provide statistical evidence that increased substitution rate along a MHC gene may lead to allelic variation, as a high substitution rate can be observed in those lineages in which many alleles are maintained. Fourth, we show that the detected patterns were independent of phylogenetic constraints. When we used phylogenetic models that control for similarity between species, due to common descent, and focused on variations within a single lineage (<it>DRB1*03</it>), the positive relationship between different substitution rates and allelic polymorphisms was still robust. Finally, we found the same effects to emerge in the analyses that eliminated within-species variation in MHC traits by using strictly single population-level studies. However, in a set of contrasting analyses, in which we focused on the non-functional <it>DRB6 </it>locus, the correlation between substitution rates and allelic variation was not prevalent.</p> <p>Conclusion</p> <p>Our results indicate that positive selection for the generation of allelic polymorphism acting on the functional part of the protein has consequences for the nucleotide substitution rate along the whole exon 2 sequence of the <it>Mhc-DRB </it>gene. Additionally, we proved that an increased substitution rate can promote allelic variation within lineages. Consequently, the evolution of different characteristics of genetic polymorphism is not independent.</p

Using the BirdTree.org website to obtain robust phylogenies for avian comparative studies: A primer

Comparative studies of trait evolution require accounting for the shared evolutionary history. This is done by including phylogenetic hypotheses into statistical analyses of species’ traits, for which birds often serve as excellent models. The online publication of the most complete molecular phylogeny of extant bird species (www.birdtree.org, BirdTree hereafter) now allows evolutionary biologists to rapidly obtain sets of equally plausible phylogenetic trees for any set of species to be incorporated as a phylogenetic hypothesis in comparative analyses. We discuss methods to use BirdTree tree sets for comparative studies, either by building a consensus tree that can be incorporated into standard comparative analyses, or by using tree sets to account for the effect of phylogenetic uncertainty. Methods accounting for phylogenetic uncertainty should be preferred whenever possible because they should provide more reliable parameter estimates and realistic confidence intervals around them. Based on a real comparative dataset, we ran simulations to investigate the effect of variation in the size of the random tree sets downloaded from BirdTree on the variability of parameter estimates from a bivariate relationship between mass-specific productivity and body mass. Irrespective of the method of analysis, using at least 1,000 trees allows obtaining parameter estimates with very small (< 0.15%) coefficients of variation. We argue that BirdTree, due to the ease of use and the major advantages over previous ‘traditional’ methods to obtain phylogenetic hypotheses of bird species (e.g. supertrees or manual coding of published phylogenies), will become the standard reference in avian comparative studies for years to comePeer reviewe

A test on within-individual changes in risk-taking behaviour due to experience to predation in the Collared Flycatcher (Ficedula albicollis)

Different experiences from the past may have influence on individual¿s behaviour through feedback mechanisms that can weaken or preserve the within-individual consistency of behavioural traits. Here, we aimed to find evidence for such feedback mechanisms that may operate on risk-taking behaviour via the effect of former experience to potential predation events in male Collared Flycatchers (Ficedula albicollis). We predicted that risk-taking of males would decrease after experiencing a predator¿s attack in previous breeding seasons (negative feedback). We assessed risk-taking by flight initiation distance (FID) that is the distance at which an individual flees from an approaching predator, which was estimated for 234 individuals from different breeding seasons. Information on predation experience (i.e. occurrence of nest predation, the incidence of capture by human observers) was available from our long-term database on individual life histories. In a horizontal approach, we found no difference in FID when comparing males with former experience to predation with males naive to predators. A longitudinal approach relying on the repeated tests of the same individuals from different years yielded analogous results, we could not show a significant change in the risk-taking behaviour of the males as a consequence of experience to predation in past years. However, we found that individuals systematically took less risk over the years, which might be a consequence of acquiring general experience with agePeer Reviewe

Blood Parasite Infection Intensity Covaries with Risk-Taking Personality in Male Carpetan Rock Lizards (Iberolacerta cyreni)

Identifying evolutionary and developmental mechanisms underlying consistent between-individual differences in behaviour is the main goal in 'animal personality studies'. Here, we explored whether activity and risk-taking varied consistently between individuals and correlated to various - potentially fitness linked - male traits in Carpetan rock lizards (Iberolacerta cyreni). Lizards showed significant consistency within both behaviours, implying the presence of activity and risk-taking personalities. However, there were no correlation between activity and risk-taking, neither on the between- nor on the within-individual levels, implying the absence of a behavioural syndrome. We found a strong link between the intensity of blood parasite (Haemogregarinidae) infection and risk-taking: lizards with higher infection intensity took more risk. While we cannot distinguish cause from causative in the parasite intensity - risk-taking correlation - our results are in line with the asset protection hypothesis predicting that individuals with lower future reproductive value should focus on the current reproductive event and take higher risk.László Zsolt Garamszegi received funds from the Spanish government within the frame of the “Plan Nacional” programme (ref. no. CGL2012- 38262 and CGL2012-40026-C02-01). Pilar López and José Martín were supported by the project MICIIN-CGL2011-24150/BOS.Peer Reviewe

Colony size and foraging range in seabirds

The reasons for variation in group size among animal species remain poorly understood. Using ‘Ashmole's halo’ hypothesis of food depletion around colonies, we predict that foraging range imposes a ceiling on the maximum colony size of seabird species. We tested this with a phylogenetic comparative study of 43 species of seabirds (28 262 colonies), and investigated the interspecific correlation between colony size and foraging ranges. Foraging range showed weak relationships with the low percentiles of colony size of species, but the strength of the association increased for larger percentiles, peaking at the maximum colony sizes. To model constraints on the functional relationship between the focal traits, we applied a quantile regression based on maximum colony size. This showed that foraging range imposes a constraint to species’ maximum colony sizes with a slope around 2. This second-order relationship is expected from the equation of the area of a circle. Thus, our large dataset and innovative statistical approach shows that foraging range imposes a ceiling on seabird colony sizes, providing strong support to the hypothesis that food availability is an important regulator of seabird populations.Peer Reviewe

Do Seasonal Glucocorticoid Changes Depend on Reproductive Investment? A Comparative Approach in Birds

Animals go through different life history stages such as reproduction, moult, or migration, of which some are more energy-demanding than others. Baseline concentrations of glucocorticoid hormones increase during moderate, predictable challenges and thus are expected to be higher when seasonal energy demands increase, such as during reproduction. By contrast, stress-induced glucocorticoids prioritize a survival mode that includes reproductive inhibition. Thus, many species down-regulate stress-induced glucocorticoid concentrations during the breeding season. Interspecific variation in glucocorticoid levels during reproduction has been successfully mapped onto reproductive investment, with species investing strongly in current reproduction (fast pace of life) showing higher baseline and lower stress-induced glucocorticoid concentrations than species that prioritize future reproduction over current attempts (slow pace of life). Here we test the >glucocorticoid seasonal plasticity hypothesis>, in which we propose that interspecific variation in seasonal changes in glucocorticoid concentrations from the non-breeding to the breeding season will be related to the degree of reproductive investment (and thus pace of life). We extracted population means for baseline (for 54 species) and stress-induced glucocorticoids (for 32 species) for the breeding and the non-breeding seasons from the database >HormoneBase>, also calculating seasonal glucocorticoid changes. We focused on birds because this group offered the largest sample size. Using phylogenetic comparative methods, we first showed that species differed consistently in both average glucocorticoid concentrations and their changes between the two seasons, while controlling for sex, latitude, and hemisphere. Second, as predicted seasonal changes in baseline glucocorticoids were explained by clutch size (our proxy for reproductive investment), with species laying larger clutches showing a greater increase during the breeding season-especially in passerine species. In contrast, changes in seasonal stress-induced levels were not explained by clutch size, but sample sizes were more limited. Our findings highlight that seasonal changes in baseline glucocorticoids are associated with a species' reproductive investment, representing an overlooked physiological trait that may underlie the pace of life

Assessing the Effects of Climate on Host-Parasite Interactions: A Comparative Study of European Birds and Their Parasites

[Background] Climate change potentially has important effects on distribution, abundance, transmission and virulence of parasites in wild populations of animals. [Methodology/Principal Finding] Here we analyzed paired information on 89 parasite populations for 24 species of bird hosts some years ago and again in 2010 with an average interval of 10 years. The parasite taxa included protozoa, feather parasites, diptera, ticks, mites and fleas. We investigated whether change in abundance and prevalence of parasites was related to change in body condition, reproduction and population size of hosts. We conducted analyses based on the entire dataset, but also on a restricted dataset with intervals between study years being 5–15 years. Parasite abundance increased over time when restricting the analyses to datasets with an interval of 5–15 years, with no significant effect of changes in temperature at the time of breeding among study sites. Changes in host body condition and clutch size were related to change in temperature between first and second study year. In addition, changes in clutch size, brood size and body condition of hosts were correlated with change in abundance of parasites. Finally, changes in population size of hosts were not significantly related to changes in abundance of parasites or their prevalence. [Conclusions/Significance] Climate change is associated with a general increase in parasite abundance. Variation in laying date depended on locality and was associated with latitude while body condition of hosts was associated with a change in temperature. Because clutch size, brood size and body condition were associated with change in parasitism, these results suggest that parasites, perhaps mediated through the indirect effects of temperature, may affect fecundity and condition of their hosts. The conclusions were particularly in accordance with predictions when the restricted dataset with intervals of 5–15 years was used, suggesting that short intervals may bias findings.The Academy of Finland is acknowledged for a grant to TE (project 8119367) and EK (project 250709). PLP was supported by a research grant (TE_291/2010) offered by the Romanian Ministry of Education and Science. T. Szép received funding from OTKA K69068 and JT from OTKA 75618. JMP was supported by a JAE grant from Consejo Superior de Investigaciones Científicas. SM-JM, FdL-AM, JF, JJS and FV were respectively supported by projects CGL2009-09439, CGL2012-36665, CGL2009- 11445, CGL2010-19233-C03-01 and CGL2008-00562 by the Spanish Ministry of Science and Innovation and FEDER and project EVITAR by the Spanish Ministry of Health. FV was also supported by the European Regional Development Fund. MACT was funded by a predoctoral FPU grant from the Spanish Ministry of Education (AP20043713). PM was supported by grant from the Polish Ministry of Science and Higher Education (project 2P04F07030), and the Foundation for Polish Science