Functional diversity of Himalayan bat communities declines at high elevation without the loss of phylogenetic diversity

Abstract

Species richness exhibits well-known patterns across elevational gradients in various taxa, but represents only one aspect of quantifying biodiversity patterns. Functional and phylogenetic diversity have received much less attention, particularly for vertebrate taxa. There is still a limited understanding of how functional, phylogenetic and taxonomic diversity change in concert across large gradients of elevation. Here, we focused on the Himalaya—representing the largest elevational gradients in the world—to investigate the patterns of taxonomic, functional and phylogenetic diversity in a bat assemblage. Combining field data on species occurrence, relative abundance, and functional traits with measures of phylogenetic diversity, we found that bat species richness and functional diversity declined at high elevation but phylogenetic diversity remained unchanged. At the lowest elevation, we observed low functional dispersion despite high species and functional richness, suggesting a niche packing mechanism. The decline in functional richness, dispersion, and divergence at the highest elevation is consistent with patterns observed due to environmental filtering. These patterns are driven by the absence of rhinolophid bats, four congeners with extreme trait values. Our data, some of the first on mammals from the Himalayan region, suggest that in bat assemblages with relatively high species diversity, phylogenetic diversity may not be a substitute to measure functional diversity.

Increasing species richness along elevational gradients is associated with niche packing in bat assemblages

“…The only other study comparing isotopic niche partitioning in bat assemblages of low and high species richness found niche packing with high niche overlap in insectivorous bat assemblages across a latitudinal gradient in Africa (Monadjem et al, 2018). Our results are consistent with these observations and also align with previous research using functional traits along the same elevational gradient (Chakravarty et al, 2021). At the presumably resource‐scarce high elevation, we found large isotopic niche width with low overlap among functional groups.…”

“…The treeline ends above 3000 m leading into alpine meadows (Champion & Seth, 1968). The sanctuary harbours 28 species of bats (Chakravarty et al, 2020(Chakravarty et al, , 2021.…”

Seasonality and interspecific temporal partitioning in a semiarid grassland bat assemblage of northwestern India

“…The audio settings of the recorders were set to a gain of 12 dB, sampling rate of 384 kHz, and triggered when they detected calls with a minimum duration of 1.5 milliseconds and a minimum trigger frequency of 10 kHz, with a trigger level of 12 dB and a trigger window of 1 second. We identified bat species from their echolocation calls based on their unique spectral structure and frequency parameters, using published information on bat calls from India and records of species known for the region (Chakravarty et al, 2021(Chakravarty et al, , 2020Raman and Hughes, 2021;Shah and Srinivasulu, 2020;Srinivasulu et al, 2013;Wordley et al, 2014) as a reference, and verified this using field observations. For the latter, we combined observations of bats visiting waterholes before dark with recordings using a Wildlife Acoustics Echo Meter Touch 2 Pro mobile bat module plugged into an Android device.…”

“…Here, we study seasonality and temporal partitioning in a bat assemblage occupying a semiarid grassland in Northwest India, at the edge of the Thar Desert. There have been very few studies of bat assemblages or communities in the Indian Subcontinent (Chakravarty et al, 2021;Ongole et al, 2018;Wordley et al, 2018), in spite of its high bat diversity, and virtually none on seasonality and temporal activity patterns around water bodies. Passive acoustic monitoring presents a powerful tool to study these questions (Lisón et al, 2019), especially given recent call libraries of bats from the region's vicinity (Shah and Srinivasulu, 2020).…”

Variability in ecological attributes of abundant species increases with taxonomic diversity: insights for assembly mechanisms of Neotropical bat communities

“…Consequently, our results agree with the hypothesis that clade competition can be a process that produces clustering of traits 3 . Although, we could not distinguish the described pattern from that which is produced if the species are lost randomly 32 .…”