Biology subjects

Smith, J. H.

Publications and source records attributed to Smith, J. H..

3 recordsLinked to original sources

bioRxiv2026

The social structure of a captive group of Rüppell's vultures (Gyps rueppellii)

Studies on the evolution of intelligence have so far mainly focused on mammals, primates in particular, and only few avian taxa, mainly corvids and parrots. Vultures, however, have relatively large brains too, and those of the Gyps genus are highly social. Their obligate scavenging lifestyle and sociality make them an excellent taxon for investigating the role of social and ecological selective pressures on the evolution of intelligence. However, little is known of Gyps vultures, particularly regarding their social complexity (sensu Social Brain Hypothesis). To investigate the complexity within their social structure, we studied the dominance hierarchy and social bonds of a captive group (n {equiv} 23) of Ruppell's vultures (Gyps rueppellii) over two consecutive years. Our results revealed that dominance ranks and affiliative bonds were stable, although there were some differences between breeding and non-breeding seasons. During the breeding season, pair-bonded individuals were more dominant and less social than unpaired individuals. Pair-bond status, age and season influenced dyadic bond strength. Most notably, pair-bonded dyads had substantially stronger bonds, but maintained multiple other strong bonds, too. Our results highlight that multiple forces shape the dominance hierarchy and affiliative network of captive Ruppell's vultures. Individual characteristics shape social bonds, social relationships are differentiated, and changes between the breeding and non-breeding season can result in social uncertainty, adding to the complexity of this system. The complexity of Ruppell's vultures' social structure seems comparable to that of some social corvid and parrot species, where it has been linked to their sophisticated cognition. Future socio-cognitive work on this and other less social vulture species could further identify the social challenges they face, and reveal whether a complex social environment may have been a selection pressure on the evolution of intelligence, both in general, and in this promising new taxonomic group for cognition studies specifically.

animal behavior and cognition↗

bioRxiv2026

Environmentally-mediated yield effects of vernalization and photoperiod alleles in historic winter wheat trials

In common wheat (Triticum aestivum L.), variation at the Vrn1 and Ppd1 loci changes plant phenology, resulting in differential adaptation useful to breeders. Because the effects of phenology on grain yield are conditional on environmental factors, the incorporation of markers for Vrn1 and Ppd1 alleles into breeding approaches has proven difficult. Historic phenotypic, genotypic, and environmental data can provide insight into the relationship between major phenology alleles and grain yield as mediated by environmental variables. Analyses of eight years of breeding trials (1,038 lines at 219 site-years) determined that weak vrn1 alleles and Ppd1 insensitivity alleles have variable effects. These effects change depending on an environment's winter temperature and latitude, respectively, but the environmentally-driven changes in effect of vrn1 alleles are much more variable than effects of Ppd1 alleles. Mediation analyses showed phenologically-dependent environmental variables are one mechanism through which phenological changes created by vrn1 and Ppd1 variants alter yield across multiple developmental stages. Environmentally-driven relationships between flowering time and yield were modeled to estimate yield allele effects as a function of effects on phenology and environmental variables. Weak winter alleles at vrn1 may play a stabilizing role on yield, due to the correlation of winter conditions that drive larger effects with later-season warm temperatures that penalize later maturity. A better mechanistic understanding of how these loci drive environment-specific yield effects may facilitate utilization of markers for these alleles and improve predictive modeling of yield.

genetics↗

bioRxiv2023

Bearded or Smooth? Awns Improve Yield when Wheat Experiences Heat Stress During Grain Fill

The presence or absence of awns - whether wheat heads are "bearded" or "smooth"- is the most visible phenotype distinguishing wheat cultivars. Previous studies suggest that awns may improve yields in heat or water-stressed environments, but the exact contribution of awns to yield differences remains unclear. Here we leverage historical phenotypic, genotypic, and climate data to estimate the yield effects of awns under different environmental conditions over a 12-year period in the Southeast US. Lines were classified as awned or awnless based on sequence data, and observed heading dates were used to associate grain fill periods of each line in each environment with climatic data and grain yield. In most environments, awn suppression was associated with higher yields, but awns were associated with better performance in heat-stressed environments more common at southern locations. Wheat breeders in environments where awns are only beneficial in some years may consider selection for awned lines to reduce year-to-year yield variability, and with an eye towards future climates.

genetics↗