Positive effect of spring advance on the diet quality of an alpine herbivore

Fecal DNA metabarcoding reveals seasonal and annual variation in willow ptarmigan diet

Understanding spatio-temporal variation in the diet of alpine herbivores is important to predict how a changing climate will affect these species in the future. We examined the spatio-temporal variation in willow ptarmigan (Lagopus l. lagopus) diet using DNA metabarcoding of fecal pellets sampled from winter to early summer over three consecutive years. Furthermore, we assessed how snow cover and vegetation phenology affected diet variation. We also investigated sex differences in diet composition. We identified 18 important diet taxa and the genera Betula, Vaccinium and Empetrum occurred most frequently. Diet composition and richness varied within and between years. Seasonally, there was a shift from a narrow winter diet dominated by trees and dwarf shrubs to a broader spring diet with more nutritious field vegetation. This seasonal progression differed among years. The temporal variation in diet was better explained by day of year than by snow cover and vegetation phenology. Females had a more diverse diet than males, but there were no sex differences in diet composition. Our results demonstrate that metabarcoding of fecal samples provides the opportunity to assess factors affecting diet composition of species in alpine ecosystems in the context of a changing climate.

Faecal nutrient deposition of domestic and wild herbivores in an alpine grassland

The contribution of herbivores to ecosystem nutrient fluxes through dung deposition has the potential to, directly and indirectly, influence ecosystem functioning. This process can be particularly important in nutrient-limited ecosystems such as alpine systems. However, herbivore dung content (carbon, C; nitrogen, N; phosphorus, P; potassium, K) and stoichiometry (C/N) may differ among species due to differences in diet, seasonality, body type, feeding strategy, and/or digestive system with consequences for soil biogeochemistry. Here we explore how species, body size, and seasonality may result in differences in dung stoichiometry for four alpine herbivores (chamois, sheep, horse, and cattle). We found that herbivore dung nutrient content often varies among species as well as with body size, with the dung of small herbivores having larger C, N, and P faecal content. Seasonality also showed marked effects on faecal nutrient content, with a general pattern of decreasing levels of faecal P, N and an increase of C/N as the summer progresses following the loss of nutrient value of the vegetation. Moreover, we showed how herbivores play an important role as natural fertilizers of C, N, and P in our study area, especially cattle. Our study highlights the importance of considering the relative contribution of different herbivores to ecosystem nutrient fluxes in management practices, especially with ongoing changes in wild and domestic herbivore populations in alpine ecosystems.

Testis Size Variation and Its Environmental Correlates in Andrew's Toad (Bufo andrewsi)

Reproductive investments influenced by environmental conditions vary extensively among geographically distinct populations. However, investigations of patterns of intraspecific variation in male reproductive investments and the mechanisms shaping this variation in anurans remain scarce. Here, we focused on the variation in testis size in 14 populations of the Andrew's toad Bufo andrewsi, a species with weak dispersal ability but wide distribution in southwestern China, to establish whether male reproductive investment varies on an environmental gradient. Our analysis revealed a significant variation in relative testis size across populations, and a positive correlation between testis size and body condition. We, however, found no geographic trends explaining the variability in the testis size. The relative testis size did not increase with increasing latitude or altitude. We also found no relationship between relative testis size and rainfall, but a negative correlation with the coefficient of variation of temperature, with larger testes under stable environments. These findings suggest that the decreased male reproductive investment of this species may be a consequence of harsher or fluctuating environmental conditions.