Browsing by Author "Coltman, David W."
Now showing 1 - 5 of 5
Results Per Page
Sort Options
Item Ancient hybridization patterns between bighorn and thinhorn sheep(2021) Santos, Sarah H. D.; Peery, Rhiannon M.; Miller, Joshua M.; Dao, Anh; Lyu, Feng-Hua; Li, Xin; Li, Meng-Hua; Coltman, David W.Whole-genome sequencing has advanced the study of species evolution, including the detection of genealogical discordant events such as ancient hybridization and incomplete lineage sorting (ILS). The evolutionary history of bighorn (Ovis canadensis) and thinhorn (Ovis dalli) sheep present an ideal system to investigate evolutionary discordance due to their recent and rapid radiation and putative secondary contact between bighorn and thinhorn sheep subspecies, specifically the dark pelage Stone sheep (O. dalli stonei) and predominately white Dall sheep (O. dalli dalli), during the last ice age. Here, we used multiple genomes of bighorn and thinhorn sheep, together with snow (O. nivicola) and the domestic sheep (O. aries) as outgroups, to assess their phylogenomic history, potential introgression patterns and their adaptive consequences. Among the Pachyceriforms (snow, bighorn and thinhorn sheep) a consistent monophyletic species tree was retrieved; however, many genealogical discordance patterns were observed. Alternative phylogenies frequently placed Stone and bighorn as sister clades. This relationship occurred more often and was less divergent than that between Dall and bighorn. We also observed many blocks containing introgression signal between Stone and bighorn genomes in which coat colour genes were present. Introgression signals observed between Dall and bighorn were more random and less frequent, and therefore probably due to ILS or intermediary secondary contact. These results strongly suggest that Stone sheep originated from a complex series of events, characterized by multiple, ancient periods of secondary contact with bighorn sheep.Item Ewe are what ewe wear: bigger horns, better ewes and the potential consequence of trophy hunting on female fitness in bighorn sheep(2022) Deakin, Samuel; Festa-Bianchet, Marco; Miller, Joshua M.; Pelletier, Fanie; Coltman, David W.In polygynous species, secondary sexual traits such as weapons or elaborate ornaments have evolved through intrasexual competition for mates. In some species, these traits are present in both sexes but are underdeveloped in the sex facing lower intrasexual competition for mates. It is often assumed that these underdeveloped sexually selected traits are a vestige of strong sexual selection on the other sex. Here, we challenge this assumption and investigate whether the expression of secondary sexual traits is associated with fitness in female bighorn sheep. Analyses of 45 years of data revealed that female horn length at 2 years, while accounting for mass and environmental variables, is associated with younger age at primiparity, younger age of first offspring weaned, greater reproductive lifespan and higher lifetime reproductive success. There was no association between horn length and fecundity. These findings highlight a potential conservation issue. In this population, trophy hunting selects against males with fast-growing horns. Intersexual genetic correlations imply that intense selective hunting of large-horned males before they can reproduce can decrease female horn size. Therefore, intense trophy hunting of males based on horn size could reduce female reproductive performance through the associations identified here, and ultimately reduce population growth and viability.Item Indirect effects on fitness between individuals that have never met via an extended phenotype(2019) Fisher, David N.; Haines, Jessica A.; Boutin, Stan; Dantzer, Ben; Lane, Jeffrey E.; Coltman, David W.; McAdam, Andrew G.Interactions between organisms are ubiquitous and have important consequences for phenotypes and fitness. Individuals can even influence those they never meet, if they have extended phenotypes that alter the environments others experience. North American red squirrels (Tamiasciurus hudsonicus) guard food hoards, an extended phenotype that typically outlives the individual and is usually subsequently acquired by non-relatives. Hoarding by previous owners can, therefore, influence subsequent owners. We found that red squirrels breed earlier and had higher lifetime fitness if the previous hoard owner was a male. This was driven by hoarding behaviour, as males and mid-aged squirrels had the largest hoards, and these effects persisted across owners, such that if the previous owner was male or died in mid-age, subsequent occupants had larger hoards. Individuals can, therefore, influence each other's resource-dependent traits and fitness without ever meeting, such that the past can influence contemporary population dynamics through extended phenotypes.Item Sex-specific effects of capital resources on reproductive timing and success in red squirrels(2022) Haines, Jessica A.; Delaney, David M.; Wishart, Andrea E.; McAdam, Andrew G.; Coltman, David W.; Lane, Jeffrey E.; Dantzer, Ben; Boutin, StanReproduction is an energetically expensive activity for both sexes. However, if males and females differ in their annual timing of reproduction, such that peak investment for one sex occurs during a more resource-limited period, there is an opportunity for sex-specific selection to act on the acquisition of energetic resources. Both male and female North American red squirrels (Tamiasciurus hudsonicus) cache conifer cones, although males typically have larger caches than females. Peak energetic investment in reproduction occurs for males during the mating season in winter and early spring (when squirrels rely almost exclusively on cached resources) and for females during lactation (which can align with fresh food availability). We provide evidence that suggests sex differences in cache size are likely driven by a stronger positive connection between cached resources and components of fitness for males than for females. Specifically, males with larger caches have greater siring success than males with smaller caches, whereas for females, only early breeding females experience a positive effect of cache size on the number of recruits produced. We also show that males sire pups and females give birth earlier in the year if they have larger caches compared with squirrels of the same sex with smaller caches. Sexual selection can thus extend beyond traits directly connected to mating behavior, and can act on traits related to acquiring resources needed to fuel reproduction that are expressed months or years in advance of breeding efforts.Item Sexually selected infanticide by male red squirrels in advance of a mast year(2018) Haines, Jessica A.; Coltman, David W.; Dantzer, Ben; Gorrell, Jamieson C.; Humphries, Murray M.; Lane, Jeffrey E.; McAdam, Andrew G.; Boutin, StanNorth American red squirrels (Tamiasciurus hudsonicus) anticipate when white spruce (Picea glauca), their primary food source, will produce large amounts of cones in infrequent and irregular mast years (Boutin et al. 2006). Cones mature in autumn and are then available as food for red squirrels, but females produce larger, and often multiple, litters the preceding spring and summer in anticipation of the upcoming mast. Because this pulse of the cone food resource follows the birth of the litter, it cannot be a source of energy for the female to produce young; instead, there must be cues for increased reproductive investment by the females prior to mast cone production, perhaps through consumption of buds on the masting trees (Boutin et al. 2006, 2013). Boutin et al. (2006) only studied females; whether male behavior anticipates mast years is still unstudied. At our study area in the Yukon, 2014 was a mast year for spruce cone production in late summer (Lamontagne et al. 2005). J. A. Haines was observing male red squirrel mating behavior during spring 2014, giving her an unanticipated opportunity to document the previously unstudied effects of a mast year on male red squirrels.