Spatial and climatic variables independently drive elevational gradients in ant species richness in the Eastern Himalaya

Abstract

Elevational gradients are considered important for understanding causes behind gradients in species richness due to the large variation in climate and habitat within a small spatial extent. Geometric constraints are thought to interact with environmental variables and influence elevational patterns in species richness. However, the geographic setting of most mountain ranges, particularly continuity with low elevation areas may reduce the effect of geometric constraints at lower elevations. In the present study, we test the effects of climatic gradients and continuity with the low elevation plains of the eastern Himalayan mountain range on patterns of species richness. We studied species richness of ants (Hymenoptera: Formicidae) on an elevational gradient between 600m and 2400m in the Eastern Himalayapart of Himalaya biodiversity hotspot. Ants were sampled in nine elevational bands of 200m with four transects in each band using pitfall and Winkler traps. We used regression models to identify the most important environmental variables that predict species richness and used constrained null models to test the effects of contiguity between the mountain range and plains. We find a monotonic decline in species richness of ants with elevation. Temperature was a more important predictor of species richness than habitat complexity. Geometric constraints model weighted by temperature with a soft lower boundary and hard upper boundary best explained the species richness pattern. This suggests that a combination of climate and geometric constraints drive the elevational species richness patterns of ants.

Patterns and drivers of leaf‐litter ant diversity along a tropical elevational gradient in Mexico

“…Bharti et al, 2013;Longino & Branstetter, 2019), though there are reports of linear decreasing patterns as well (e.g. Marathe et al, 2020;Sanders et al, 2007).…”

“…Bharti et al, 2013; Longino & Branstetter, 2019), though there are reports of linear decreasing patterns as well (e.g. Marathe et al, 2020; Sanders et al, 2007). Many studies have argued that variation in elevational patterns of species richness may depend on the regional factors of the mountain (Rahbek, 1995) or the taxa involved (McCain, 2009, 2010), but global analyses have also pointed out that some inconsistency of patterns may be due to gradient truncation (McCain & Grytnes, 2010).…”

“…Longino & Branstetter, 2019; Machac et al, 2011) and precipitation (e.g. Smith et al, 2014; Szewczyk & McCain, 2016), and in some instances geometric constraints (Marathe et al, 2020; Sanders, 2002), have a strong effect in shaping ant diversity patterns along elevational gradients. Similarly, compositional dissimilarity of litter ants in relation to changes in elevation has also been observed to decrease with elevation (e.g.…”

Diversity and distribution patterns of ants along elevational gradients

“…Species richness is also influenced by different sets of variables among the individual taxonomic groups but temperature is the most important in the majority of taxa (Peters et al 2016). Marathe et al (2020) suggested that elevational richness patterns are driven by a combination of climatic and geometric constraints. Variation in ant species richness over the elevational gradient was partially explained by climate (Sanders et al 2003) and was influenced by the presence of favourable physical conditions and the prey resources (Sabu et al 2008).…”

Intraspecific trait variability and community assembly in hawkmoths (Lepidoptera: Sphingidae) across an elevational gradient in the eastern Himalayas, India

“…New species, of even distinctive vertebrate taxa, continue to be described from the region (e.g., Athreya, 2006a; Captain et al., 2019; Mirza et al., 2020; Sinha et al., 2005; Sondhi & Ohler, 2011). The entire list of research publications on diversity patterns in the region is a short one: elevational gradient of bird diversity (Acharya et al., 2011; Price et al., 2014; Schumm et al., 2020; Surya & Keitt, 2019), tree diversity patterns and population structure (Bhuyan et al., 2003; Rana et al., 2019), and distribution and abundance of arthropods (Ghosh‐Harihar, 2013; Marathe et al., 2020; Supriya et al., 2020).…”