Habitat availability drives the distribution–abundance relationship in phytophagous true bugs in managed grasslands

Abstract

The nearly universal positive relationship between the distribution and abundance of species has been explained by several hypotheses but hitherto no consensus has been reached. Here, we used monitoring data of 105 phytophagous true bug species (Heteroptera) from 150 grassland sites over six years to test how (1) range position, (2) resource use, (3) resource availability, (4) density-dependent habitat selection, (5) metapopulation dynamics, and (6) habitat dispersal affect the distribution-abundance relationship. For the use in a confirmatory path analysis, we constructed causal pathways representing the hypothesized relationships and tested them separately and in a combined analysis. Our results show that the distribution-abundance relationship in phytophagous true bugs is driven by habitat-availability. An increasing local density of the host-plants increases the distribution of the species in the landscape, which in turn increases their local abundance. Thereby habitat availability facilitates dispersal success. We conclude that local abundance of herbivores facing habitat destruction could decline owing to a decrease in population dynamics between sites at the landscape scale. Finally, our results underline the potential of confirmatory path analysis for testing competing hypotheses.

Mobility costs and energy uptake mediate the effects of morphological traits on species' distribution and abundance

“…In line with several previous studies that reported weak and insignificant size‐abundance relationships for other ectothermic taxa (Blackburn et al 1993, 2006, Friess et al 2017), we show that body size does not directly affect the abundance of European butterfly species (Fig. 3, Model 1).…”

“…Integrating these two main components of the energy budget, furthermore established a direct negative effect of body size on the abundance of species that likely reflects the increase in maintenance costs associated with an increase in body size (not explicitly modeled as it lacks appropriate data; Brown et al 2004, White et al 2007. In the context of previous studies (Blackburn et al 1993, 2006, Friess et al 2017, our results thereby highlight that species' energy compensation strategies largely explain the scatter in sizeabundance relationships and that accounting for these strategies might be more important in ectotherms than in endotherms because of their comparatively low maintenance costs (Nagy et al 1999).…”

“…We were particularly interested in the importance of functional traits of species (i.e., intrinsic drivers) of their distribution and abundance. However, it is well known that the distribution and abundance of phytophagous insects is mainly driven by the availability of their habitat (Curtis et al 2015, Friess et al 2017). To account for the potential effect of habitat availability on the distribution and abundance of species, we used gridded distribution information on all 473 larval host plants of butterflies in Switzerland for the years 2003–2016 from the Info Flora Database (accessed on 18 October 2017; a grid of cells with a size of 5 × 5 km).…”

“…Generalized framework of predicted effects of morphological traits of species on their distribution and abundance via proxies for mobility costs and energy uptake. Examples for supported single effects are as follows: L1, Betts and Wootton (1988); L2, Talloen et al (2004); L3, Tiple et al (2009); L4, Corben (1983); L7, Betts and Wootton (1988); L8, Boggs and Freeman (2005); L9, Stevens et al (2012); L12, L13, L14, Friess et al (2017); L15, Brändle and Brandl (2001). These effects have been integrated into our framework in accordance with the main assumption of trait‐based theory that components of the energy budget mediate the effects of morphological traits on the distribution and abundance of species.…”

“…Generalized framework of predicted effects of morphological traits of species on their distribution and abundance via proxies for mobility costs and energy uptake. Examples for supported single effects are as follows: L1,Betts and Wootton (1988); L2,Talloen et al (2004); L3,Tiple et al (2009); L4,Corben (1983); L7,Betts and Wootton (1988); L8,Boggs and Freeman (2005); L9,Stevens et al (2012); L12, L13, L14,Friess et al (2017); L15, Br€ andle and Brandl…”