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 of life-history traits, like 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 ageing 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 post-fledging parental care (PC3). Phylogeny had at best a small-to-medium influence on Adult and Chick TL (r² = 0.190 and 0.138, respectively), but a substantial influence on TROC (r² = 0.688). Phylogeny strongly influenced life histories: PC1 (r² = 0.828), PC2 (0.838), and PC3 (0.613). 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 = -0.340; with phylogenetic correction, r = -0.490). Independent of body size, long-lived species with smaller clutches and slower embryonic rate of growth may exhibited 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.

Sociality and migration predict hybridization across birds

Hybridization represents a natural experiment that can provide insight into processes of speciation and diversification. Though considerable research has focused on hybrid zone dynamics, macroevolutionary investigations of the factors that influence hybridization are few. Here, we compile a database of avian hybrids and perform comparative analyses to determine whether several social and life-history variables influence broad patterns of hybridization. We perform three main analyses: phylogenetic logistic regression to examine variables that are associated with the presence of hybridization, phylogenetic Poisson regression of only those species exhibiting hybridization to determine which variables are associated with the extent of hybridization, and a phylogenetic logistic regression on a subset of data to assess potential pseudoreplication. After testing several social and life-history variables, we found that social bond duration is associated with the presence and extent of hybridization. Specifically, lengthy social bonds are negatively associated with the presence and extent of hybridization. In addition to social bond length, migration is positively linked with a greater likelihood of hybridization. The broad-scale correlations between species-specific traits and hybridization across diverse avian lineages suggest commonalities in the fine-scale processes involved in mating with heterospecifics, which in turn has implications for how we think about, study and understand hybridization processes and their influence on evolutionary trajectories.

The Ecological Brain

In this chapter, I examine the evidence for a role for the preeminent selection pressure, ecology, in shaping animal brains and in causing changes in brain size within and among species. I describe what ‘ecology’ has meant in comparative analyses, e.g. foraging, range size, and life history variables. I provide evidence for a clear association between ecology and the size of sensory-motor brain regions and go on to use the relationship between space and the hippocampus to show the generality of this relationship beyond food storing. I discuss the strength of the data showing that migration, foraging, and domestication have caused changes in brain size. I conclude that while there is evidence of domestication, in particular, having changed whole brain size, it is at the level of brain regions that there is overwhelming evidence for an effect of ecology on brain size.

Multiple separate cases of pseudogenized meiosis genes Msh4 and Msh5 in Eurotiomycete fungi: associations with Zip3 sequence evolution and homothallism, but not Pch2 losses

The overall process of meiosis is conserved in many species, including some lineages that have lost various ancestrally present meiosis genes. The extent to which individual meiosis gene losses are independent from or dependent on one another is largely unknown. Various Eurotiomycete fungi were investigated as a case system of recent meiosis gene losses after BLAST and synteny comparisons found Msh4, Msh5, Pch2, and Zip3 to be either pseudogenized or undetected in Aspergillus nidulans yet intact in congeners such as A. fumigatus. Flanking gene-targeted degenerate PCR primers applied to 9 additional Aspergillus species found (i) Msh4, Msh5, and Zip3 pseudogenized in A. rugulosus (sister taxon to A. nidulans) but intact in all other amplified sequences; and (ii) Pch2 not present at the syntenic locus in most of the 9 species. Topology tests suggested two independent Pch2 losses in genus Aspergillus, neither directly coinciding with pseudogenization of the other three genes. The A. nidulans-A. conjunctus clade Pch2 loss was not associated with significant Ka/Ks changes for Msh4, Msh5, or Zip3; this suggests against prior Pch2 loss directly altering sequence evolution constraints on these three genes. By contrast, Zip3 Ka/Ks tended to be elevated in several other Eurotiomycete fungi with independently pseudogenized Msh4 and Msh5 (Talaromyces stipitatus, Eurotium herbariorum). The coinciding Ka/Ks elevation and/or clear pseudogenization of Zip3 in taxa with pseudogenized Msh4 and Msh5 is consistent with some degree of molecular coevolution. Possible molecular, environmental, and life history variables (e.g., homothallism) that may be associated with these numerous independent meiosis gene losses (Msh4: 3, Msh5: 3, Zip3: ≥ 1, Pch2: 4) are discussed.

Interspecific effects of the cladoceran- (Moina macrocopa) and the rotifer- (Brachionus calyciflorus) conditioned medium on main life history variables in relation to temperature and algal density

Current research on the effects of cladoceran allelochemicals on rotifers has been inconclusive and the allelopathic effects of rotifers on cladocerans are unknown. We sought to fill this knowledge gap with life table demography experiments assessing the interspecific effects of Moina macrocopa-conditioned mediums (MCM) and Brachionus calyciflorus-conditioned mediums (CCM) on the main life history variables under different temperatures and algal densities. Our results demonstrate that, when compared to the allelopathic effects of M. macrocopa on B. calyciflorus, M. macrocopa had higher sensitivity to the allelochemicals from B. calyciflorus. When compared to the controls, the chemically-mediated effects of M. macrocopa on the net reproductive rate (R0), intrinsic rate of population growth (rm) and total number of offspring (NO) of B. calyciflorus were non-significant in many cases while in a few the impacts were stimulatory or inhibitory under different concentrations of MCM, temperatures, and food densities. However, when compared to the controls, the allelopathic effects of B. calyciflorus on the R0, rm and NO of M. macrocopa were stimulatory in many cases; some impacts were inhibitory or non-significant under different concentrations of CCM, temperatures, and food densities. In addition, life expectancy at birth (e0), generation time (T), and average lifespan (LS) of B. calyciflorus and M. macrocopa cultured in the conditioned medium nearly did not differ significantly from the controls. Our results suggest that the interspecific allelopathic effects of B. calyciflorus and M. macrocopa are dependent on the origin and concentration of the allelochemical, life history variable, temperature, and food (algal) density. Additionally, the underlying mechanisms should be further investigated.

Reproduction in the Baka pygmies and drop in their fertility with the arrival of alcohol

To understand the diversity of human growth and development from an evolutionary point of view, there is an urgent need to characterize the life-history variables of vanishing forager societies. The small body size of the Baka pygmies is the outcome of a low growth rate during infancy. While the ages at sexual maturity, menarche, and first delivery are similar to those in other populations, fertility aspects are unknown. In the Le Bosquet district in Cameroon, thanks to systematic birth records kept from 1980 onwards, we were able to assign ages to individuals with certainty. This study, based on chronological records and on data collected from 2007 to 2017, presents life-history variables related to fertility and mortality among the Baka pygmies: total fertility rate, age-specific fertility rate, completed family size, reproductive span, age at menopause, and infant and juvenile mortality. The Baka present low infant and juvenile mortality, and their fertility pattern differs from that of other forager societies in the higher age-specific fertility rates found in the two lower age classes. Future studies will need to assess whether this particular pattern and the short interbirth interval are related to highly cooperative childrearing, which in the Baka is associated with slow growth. The fertility rate has fallen drastically since 2011, and this matches the arrival of cheap alcohol in the community. Our data provide a first-hand record of the impact of alcohol on fertility in a hunter-gatherer society which appears to be seriously compromising the survival of the Baka.

Reply to Van Lange et al.: Proximate and ultimate distinctions must be made to the CLASH model

Transcending reviewed proximate theories, Van Lange et al.'s CLASH model attempts to ultimately explain the poleward declension of aggression and violence. Seasonal cold is causal, but, we contend, principally as an ecologically relevant evolutionary pressure. We further argue that futurity and restraint are life history variables, and that Life History Theory evolutionarily explains the biogeography of aggression and violence as strategic adaptation.