Recherche

Poirier, Marc-Antoine; Coltman, David W.; Pelletier, Fanie; Jorgenson, Jon; Festa-Bianchet, Marco — 2018-08-31 Isolation of small populations is expected to reduce fitness through inbreeding and loss of genetic variation, impeding population growth and compromising population persistence. Species with long generation time are the least likely to be rescued by evolution alone. Management interventions that maintain or restore genetic variation to assure population viability are consequently of significant importance. We investigated, over 27 years, the genetic and demographic consequences of a demographic bottleneck followed by artificial supplementation in an isolated population of bighorn sheep (Ovis canadensis). Based on a long-term pedigree and individual monitoring, we documented the genetic decline, restoration and rescue of the population. Microsatellite analyses revealed that the demographic bottleneck reduced expected heterozygosity and allelic diversity by 6.2 and 11.3%, respectively, over two generations. Following supplementation, first-generation admixed lambs were 6.4% heavier at weaning and had 28.3% higher survival to 1 year compared to lambs of endemic ancestry. Expected heterozygosity and allelic diversity increased by 4.6 and 14.3% after two generations through new alleles contributed by translocated individuals. We found no evidence for outbreeding depression and did not see immediate evidence of swamping of local genes. Rapid intervention following the demographic bottleneck allowed the genetic restoration and rescue of this bighorn sheep population, likely preventing further losses at both the genetic and demographic levels. Our results provide further empirical evidence that translocation can be used to reduce inbreeding depression in nature and has the potential to mitigate the effect of human-driven environmental changes on wild population.

Poirier, Marc-Antoine; Kozlovsky, Dovid; Hermer, Ethan; Bertram, Susan; Morand-Ferron, Julie — 2022-06-01 <p>Central place foraging field crickets are an ideal system for studying the adaptive value of learning and memory, but more research is needed on ecology-relevant cognition in these invertebrates. Here, we test the visuospatial place learning of Texas field crickets (<em>Gryllus texensis</em>) in a radial arm maze. Our study expands previous work on <em>G. texensis</em> cognition for accuracy measures and extends our previous findings on females to both sexes. Additionally, our study examines whether crickets use intra- or extra-maze cues to locate a food reward using a maze rotation putting the cues in conflict. We found that male and female crickets improved performance over trials when measured by accuracy variables but not latency variables; thigmotaxis negatively impacted performance in both sexes. In a reward-absent trial, both male and female crickets demonstrated place memory. When intra- and extra-maze cues conflicted during a rotation trial, crickets’ performance was not better than chance. Our rotation results suggest that crickets may experience reciprocal overshadowing of conflicting cues – a result most often seen in other taxa with conflicting multi-modal cues. We conclude that crickets do not rely solely on: (1) a single-cue association; (2) route-following; or (3) their own scent cues to navigate the maze. Instead, male and female Texas field crickets seem to learn the location of the reward using a combination of proximal and distal cues. The possibility to test large numbers of wild-caught or laboratory-reared individuals opens the door to future investigations on the evolutionary ecology of visuospatial learning in these invertebrates.</p>