Ant diversity patterns across tropical elevation gradients: effects of sampling method and subcommunity

Abstract

Local diversity may be influenced by niche assembly processes involving competition for limited resources, or by niche conservatism and the length of time clades have had to diversify. Midelevation peaks in ant diversity on wet forest elevational gradients are most consistent with niche conservatism effects. However, it is possible that subsets of the ant community vary in the degree to which niche assembly processes are important, and this may be revealed by sampling methods that bias toward particular subsets. A previous study of ant-elevation patterns in Middle American wet forest relied on Winkler sampling, a method that samples much of the ant community that occurs in leaf litter and rotten wood on the forest floor. Here, we evaluate richness patterns at the same sites as the previous study, using two alternative methods: baiting and beating. Baiting attracts ants to a concentrated resource and might be expected to attract a community more shaped by competitive interactions. Diversity patterns at baits were nearly identical to patterns from Winkler samples, for all ants combined and for the genus Pheidole, which are abundant omnivorous ants that are among the most common at baits. There was no evidence that stronger competitive effects influenced the shape of the diversity curve. Beating samples capture ants that forage on low vegetation, a distinct arboreal community with lower phylogenetic diversity than litter ants and inhabiting a more variable microclimate. Arboreal ants differed from litter ants in having a less distinct mid-elevation peak, with less of a decline from 500 m to sea level. The lowland decline in litter ant diversity may be caused by the recent upslope shift in temperature associated with the current interglacial period. Arboreal ants may be buffered from this effect by adaptation to canopy life, tolerating broader extremes of temperature, or by high rates of dispersal from warmer regions.

Collembola (Arthropoda: Hexapoda) Assemblages in the Canopy and Forest Floor along an Elevational Gradient at Mt. Makiling, Philippines

“…A clear distinction in the faunal composition of springtail assemblage in both strata (canopy vs. forest floor) and elevation was observed in a tropical forest in the Philippines. The distinct assemblages along elevation gradients concur with other studies on temperate forest springtails (Maunsell et al 2013) and with other tropical forest arthropods (Nunes et al 2016;Brehm et al 2018;Longino et al 2019). The distinct springtail communities along an elevation gradient may be linked to the known effects of elevation on the properties, temperature, and moisture of soil (Jiang et al 2015).…”

The arboreal ants of a Neotropical rain forest show high species density and comprise one third of the ant fauna

“…All rights reserved alike. Longino et al (2019) hypothesized that arboreal ants were less sensitive than ground ants to warming and elevational range shifts associated with the current interglacial, and thus may be less sensitive to anthropogenic climate warming in the future. This study of the La Selva fauna can facilitate testing of the hypothesis, by creating a benchmark that will allow assessment of changes over time in ant community richness and composition, in parallel with changes in regional land use and local climate.…”

Vertical niche and elevation range size in tropical ants: Implications for climate resilience

“…We test this relationship using the rainforest ant fauna of the Australian Wet Tropics Bioregion. Ants are an excellent study system for testing scaling rules in biogeography as they fill multiple niches in the rainforest environment and occupy space along both vertical and elevation gradients (Blüthgen et al., 2003; Longino et al., 2019). Ant distribution is strongly related to temperature—temperature requirements for brood development and adult foraging success are both important drivers of ant distributions (Kipyatkov & Lopatina, 2015; Penick et al., 2017).…”

“…We test this relationship using the rainforest ant fauna of the Australian Wet Tropics Bioregion. Ants are an excellent study system for testing scaling rules in biogeography as they fill multiple niches in the rainforest environment and occupy space along both vertical and elevation gradients (Blüthgen et al, 2003;Longino et al, 2019).…”