A diet rich in C₃ plants reveals the sensitivity of an alpine mammal to climate change

Abstract

Plant-herbivore interactions provide critical insights into the mechanisms that govern the spatiotemporal distributions of organisms. These interactions are crucial to understanding the impacts of climate change, which are likely to have an effect on the population dynamics of alpine herbivores. The Royle's pika (Ochotona roylei, hereafter pika) is a lagomorph found in the western Himalaya and is dependent on alpine plants that are at risk from climate change. As the main prey of many carnivores in the region, the pika plays a crucial role in trophic interactions. We examined topographical features, plant genera presence and seasonal dynamics as drivers of the plant richness in the pika's diet across an elevational gradient (2,600-4,450 m). We identified 79 plant genera in the faecal pellets of pikas, of which 89% were forbs, >60% were endemic to the Himalaya, and 97.5% of the diet plant genera identified followed the C photosynthetic pathway. We found that, during the premonsoon season, the number of genera in the pika's diet decreased with increasing elevation. We demonstrate that a large area of talus supports greater plant diversity and, not surprisingly, results in higher species richness in the pika's diet. However, in talus habitat with deep crevices, pikas consumed fewer plant genera suggesting they may be foraging suboptimally due to predation risk. The continued increase in global temperature is expected to have an effect on the distribution dynamics of C plants and consequently influence pika diet and distribution, resulting in a significant negative cascading effect on the Himalayan ecosystem.

Noninvasive sampling reveals population genetic structure in the Royle’s pika, Ochotona roylei, in the western Himalaya

“…The Royle's pika often feeds on plants with high levels of secondary metabolites (Bhattacharyya et al, ). The presence of plant secondary metabolites in fecal pellets can hamper downstream genetic analysis by inhibiting enzymatic reactions in polymerase chain reaction (PCR; Weishing, Nybom, Wolff, & Meyer, ).…”

“…For example, climate‐induced heat (Beever, Brussard, & Berger, ), cold, or nutritional stress (Wilkening, Ray, Beever, & Brussard, ) led to historical extinctions of local populations and recent range contraction. While dispersal to higher elevation may allow pikas to persist in suitable microclimate, habitat fragmentation or non‐availability of preferred food plants can impair their ability to cope with the changing environment and pose a threat to their survival and fitness (Bhattacharyya, Dawson, Hipperson, & Ishtiaq, ; Ray, Beever, & Loarie, ; Schloss, Nuñez, & Lawler, ; Walther et al, ).…”

“…The Royle's pika is sensitive to high temperatures (>15°C) that lead to thermal stress and limit overall activity (Bhattacharyya, Adhikari, & Rawat, ). Furthermore, the Royle's pika play a crucial role in trophic interactions in alpine habitat—pikas are the major prey base for many carnivores as well as influencing native plant community structure (Aryal, Sathyakumar, & Kreigenhofer, ; Bhattacharyya et al, ; Bhattacharyya, Dutta, Adhikari, & Rawat, )—their disappearance can have a significant negative cascading effect on overall ecosystem functioning (Gilg, Sittler, & Hanski, ; Tylianakis, Didham, Bascompte, & Wardle, ).…”

“…Similarly, microhabitat characteristics such as rock cover area, availability of rock talus with small crevice size (<15 cm), govern the habitat occupancy in Royle's pika (Bhattacharyya et al, ). A large area of talus supports greater plant diversity and results in higher species richness in the pika's diet (Bhattacharyya et al, ). Therefore, we expect that Royle's pika populations would be influenced by topographical barriers (e.g., river low land valleys) as well as forage availability (e.g., C 3 plants).…”

Introduction: Special issue on species interactions, ecological networks and community dynamics – Untangling the entangled bank using molecular techniques

“…Bhattacharyya et al () analyse the plant contents of faecal pellets of Royle's pika ( Ochotona roylei ), a lagomorph endemic to the Himalayas. They show how the diet of the pika varies with elevation and with habitat structure, likely reflecting constraints and preferences during foraging (Bhattacharyya et al, ).…”