Climatic changes and the fate of mountain herbivores

Mountains are strongly seasonal habitats, which require special adaptations in wildlife species living on them. Population dynamics of mountain ungulates are largely determined by the availability of rich food resources to sustain lactation and weaning during summer. Increases of temperature affect plant phenology and nutritional quality. Cold-adapted plants occurring at lower elevations will shift to higher ones, if available. We predicted what could happen to populations of mountain ungulates based on how climate change could alter the distribution pattern and quality of high-elevation vegetation, using the “clover community-Apennine chamois Rupicapra pyrenaica ornata” system. From 1970 to 2014, increasing spring temperatures (2 °C) in our study area led to an earlier (25 days) onset of green-up in Alpine grasslands between 1700 and 2000 m, but not higher up. For 1970–2070, we have projected trends of juvenile winter survival of chamois, by simulating trajectories of spring temperatures and occurrence of clover, through models depicting four different scenarios. All scenarios have suggested a decline of Apennine chamois in its historical core range, during the next 50 years, from about 28% to near-extinction at about 95%. The negative consequences of climate changes presently occurring at lower elevations will shift to higher ones in the future. Their effects will vary with the species-specific ecological and behavioural flexibility of mountain ungulates, as well as with availability of climate refugia. However, global shifts in distributional ranges and local decreases or extinctions should be expected, calling for farsighted measures of adaptive management of mountain-dwelling herbivores.

Epicotyl morphophysiological dormancy and storage behaviour of seeds of Strychnos nux-vomica, Strychnos potatorum and Strychnos benthamii (Loganiaceae)

We hypothesized that Strychnos nux-vomica and Strychnos potatorum in seasonal tropical ecosystems have dormant desiccation-tolerant seeds, while those of Strychnos benthamii growing in aseasonal wet habitats have non-dormant desiccation-sensitive seeds. Germination, imbibition, the effect of gibberellic acid on germination and changes in the embryo to seed length ratio (E:S) during incubation were determined for the three species. Seed storage behaviour was identified with the hundred seed test. Time taken for epicotyl emergence was recorded. Radicle emergence of S. nux-vomica, S. potatorum and S. benthamii at 25°C under light/dark conditions (12/12 h) was completed within 76, 49 and 11 d, respectively. S. nux-vomica and S. potatorum seeds incubated on GA3 germinated to a higher percentage than non-treated seeds. E:S of S. nux-vomica, S. potatorum and S. benthamii had increased by 38.2, 34.5 and 25.5%, respectively, at radicle emergence. Shoot emergence of S. nux-vomica, S. potatorum and S. benthamii was observed after 76, 74 and 45 d from radicle emergence, respectively. Thus, it can be concluded that the seeds of all three species have epicotyl morphophysiological dormancy. Hundred seed tests revealed that S. nux-vomica and S. potatorum seeds were desiccation-tolerant, while those of S. benthamii were desiccation-sensitive. Our study showed that species from seasonal habitats (S. nux-vomica and S. potatorum) have desiccation-tolerant morphophysiologically dormant seeds, while those from an aseasonal habitat (S. benthamii) have desiccation-sensitive morphophysiologically dormant seeds, revealing that their dormancy and desiccation tolerance behaviour are adaptations to their environment.

Seasonal environments drive convergent evolution of a faster pace-of-life in tropical butterflies

ABSTRACTGlobal change can trigger shifts in habitat stability and shape the evolution of organismal life-history strategies, with unstable habitats typically favouring a faster pace-of-life. We test this hypothesis in species-rich Mycalesina butterflies that have undergone parallel radiations in Africa, Asia, and Madagascar. First, our ancestral state reconstruction of habitat preference, using ~85% of extant species, revealed that early forest-linked lineages began to invade seasonal savannahs during the Late Miocene-Pliocene. Second, rearing replicate pairs of forest and savannah species from the African and Malagasy radiation in a common garden experiment, and utilising published data from the Asian radiation, demonstrated that savannah species consistently develop faster, have smaller bodies, higher fecundity with an earlier investment in reproduction, and reduced longevity, compared to forest species across all three radiations. We argue that time-constraints for reproduction favoured the evolution of a faster pace-of-life in savannah species that facilitated their persistence in seasonal habitats.

Circadian clock mechanism driving mammalian photoperiodism

The annual photoperiod cycle provides the critical environmental cue synchronizing rhythms of life in seasonal habitats. In 1936, Bünning proposed a circadian-based coincidence timer for photoperiodic synchronization in plants. Formal studies support the universality of this so-called coincidence timer, but we lack understanding of the mechanisms involved. Here we show in mammals that long photoperiods induce the circadian transcription factor BMAL2, in the pars tuberalis of the pituitary, and triggers summer biology through the eyes absent / thyrotrophin (EYA3 / TSH) pathway. Conversely, long-duration melatonin signals on short photoperiods induce circadian repressors including DEC1, suppressing BMAL2 and the EYA3/TSH pathway, triggering winter biology. These actions are associated with progressive genome-wide changes in chromatin state, elaborating the effect of the circadian coincidence timer. Hence, circadian clock-pituitary epigenetic pathway interactions form the basis of the mammalian coincidence timer mechanism. Our results constitute a blueprint for circadian-based seasonal timekeeping in vertebrates.