Spatial patterns of species richness and nestedness in ant assemblages along an elevational gradient in a Mediterranean mountain range

Abstract

21The study of biodiversity spatial patterns along ecological gradients can serve to 22 elucidate factors shaping biological community structure and predict ecosystem 23 responses to global change. Ant assemblages are particularly interesting as study cases, 24 because ant species play a key role in many ecosystem processes and have frequently 25 been identified as useful bioindicators. Here we analyzed the response of ant species 26 richness and assemblage composition to elevational gradients in Mediterranean 27 grasslands and subsequently tested whether these responses were stable spatially and 28 temporally. We sampled ant assemblages in two years (2014, 2015) in two mountain 29 ranges (Guadarrama, Serrota) in Central Spain, along an elevational gradient ranging 30 from 685 to 2390 m a.s.l.31 Jackknife estimates of ant species richness ranged from three to 18.5 species and 32 exhibited a hump-shaped relationship with elevation that peaked at mid range values 33 (1100 -1400 m). This pattern was transferable temporally and spatially. Elevation was 34 significantly related to ant assemblage composition and facilitated separation of higher 35 elevation assemblages (> 1700 m) from the remaining lower elevation species groups.36 Ant assemblages were nested; therefore species assemblages with a decreased number 37 of species were a subset of the richer assemblages, although species turnover was more 38 important than pure nestedness in all surveys. The degree of nestedness changed non-39 linearly as a cubic polynomial with elevation. These assembly patterns were observed 40 over time but not between the two study regions. 41 We concluded double environmental stressors typical of Mediterranean mountains 42 explained species richness patterns: drought at low elevations and cold temperatures at 43 high elevations likely constrained richness at both extremes of elevational gradients. 3 44 The fact that species turnover showed a dominant role over pure nestedness suggested 45 current ant assemblages were context-dependent (spatio-temporal factors) and highly 46 vulnerable to global change, which threatens the conservation of present day native ant 47 communities, particularly at high elevations. 48 49 Introduction 50 Predicting the response of biodiversity to the main drivers of Global Change has 51 become a primary goal of modern ecology [1-3]. Consequently, the analysis of species 52 richness and assembly patterns along latitudinal and altitudinal gradients provide clues 53 to project possible effects of climate change on communities [4, 5]. The Mediterranean 54 mountains are particularly suitable for this purpose, given a characteristic combination 55 of temperature and water availability gradients in space and time, which determines a 56 progressively cooler and wetter environment at higher elevations while valleys suffer 57 more severe summer drought conditions [6, 7]. In addition, the Mediterranean Basin 58 will probable face particularly marked increases in aridity, temperature and frequency of 59 extreme climatic...

Diversity and distribution patterns of ants along elevational gradients

“…However, tropical regions of Africa were less diverse than the regions with similar latitude in Australasia or Neotropics (Guenard et al 2012). Sanders (2002) observed a decreasing pattern with the maximum ant species richness at lowland habitats; however, others have reported maximum richness at mid-elevation habitats (Smith et al 2014, Nowrouzi et al 2016, Flores et al 2018. A mid-elevation peak is the most typical (50%) of altitudinal species richness pattern, but a decreasing pattern (25%) has also been frequently reported (Rahbek 2005).…”

“…The global ant elevational diversity patterns appear more complex than those of many vertebrate taxa, and they are further influenced by multiple drivers (Szewczyk & McCain 2016). Flores et al (2018) suggested that drought conditions at low elevations and cold temperatures at high elevations prevent the richness at both extremes of elevational gradients in the Mediterranean mountains. The key hypotheses to explain these broad-scale diversity gradients are based on temperature, water availability, productivity, area, geometric constraints and plant diversity (Peters et al 2016).…”

Modelling the distribution of bat activity areas for conservation in a Mediterranean mountain range

“…This pattern agrees with the usual patterns of species richness in dry mountains where productivity, a main driver of species richness (Cusens et al ., 2012), increases between dry‐low and cold‐high elevations (Rahbek, 2005; McCain, 2009). A similar pattern of increased species richness at intermediate elevations of the Guadarrama Mountains has already been observed in other taxonomic groups (e.g., ants and birds; Flores et al ., 2018) supporting the role of this mountain range as a regional hotspot of biodiversity.…”

Ant assemblage composition explains high predation pressure on artificial caterpillars during early night

“…It is also important to note that ant assemblage composition was influenced not only by time interval but also by study site location, indicating the important role of spatial factors in shaping ant assemblage composition in the monsoonal tropical rainforest (e.g. Mezger & Pfeiffer, ; Flores et al ., ; Yusah et al ., ).…”