Ecotypic differentiation between urban and rural populations of the grasshopper Chorthippus brunneus relative to climate and habitat fragmentation

Abstract

Urbanization alters environmental conditions in multiple ways and offers an ecological or evolutionary challenge for organisms to cope with. Urban areas typically have a warmer climate and strongly fragmented herbaceous vegetation; the urban landscape matrix is often assumed to be hostile for many organisms. Here, we addressed the issue of evolutionary differentiation between urban and rural populations of an ectotherm insect, the grasshopper Chorthippus brunneus. We compared mobility-related morphology and climate-related life history traits measured on the first generation offspring of grasshoppers from urban and rural populations reared in a common garden laboratory experiment. We predicted (1) the urban phenotype to be more mobile (i.e., lower mass allocation to the abdomen, longer relative femur and wing lengths) than the rural phenotype; (2) the urban phenotype to be more warm adapted (e.g., higher female body mass); and (3) further evidence of local adaptation in the form of significant interaction effects between landscape of origin and breeding temperature. Both males and females of urban origin had significantly longer relative femur and wing lengths and lower mass allocation to the abdomen (i.e., higher investment in thorax and flight muscles) relative to individuals of rural origin. The results were overall significant but small (2-4%). Body mass and larval growth rate were much higher (+10%) in females of urban origin. For the life history traits, we did not find evidence for significant interaction effects between the landscape of origin and the two breeding temperatures. Our results point to ecotypic differentiation with urbanization for mobility-related morphology and climate-related life history traits. We argue that the warmer urban environment has an indirect effect through longer growth season rather than direct effects on the development.

Effects of within-generation thermal history on flight performance ofCeratitis capitata: colder is better

“…Berwaerts et al, 2002;San Martin y Gomez and Van Dyck, 2012;Ferrer et al, 2013), these effects are less straightforward than what might have been expected based on prior work from Drosophila species, for example. However, we employed a distinctly different approach to typical assessments of rearing temperature on fly morphology.…”

“…Instead, the opposite appears to be more broadly true, such that, low WL or high wing area (for example) is not always associated with flight, but having a high WL or small wing area may well be associated with the failure to achieve flight. Thus, although flight failure could be explained as a result of the absence of a particular morphological trait, the presence of that trait does not necessarily confer greater flight performance, and consequently, dispersal potential (in disagreement with Berwaerts et al, 2002;San Martin y Gomez and van Dyck, 2012). Such a result, if it holds more broadly, may have far-reaching implications for predictions of climate change impacts, or temperature variation, on the dispersal ability of insects as it would complicate the prediction of performance and dispersal from the measurement of only morphological features, as is often undertaken.…”

“…The resulting changes in performance can affect the short-and long-term dispersal capacity of arthropods with significant implications for ecology and evolution (reviewed recently in e.g. Feder et al, 2010;Bonte et al, 2012;Clobert et al, 2012;San Martin y Gomez and van Dyck, 2012).…”

“…To this end, a range of morphological variables [body mass (M b ), wing width, wing length, wing area, wing loading (WL) and aspect ratio (AR)] were examined, as all have previously been implicated as influencing flight performance and manoeuvrability in the field and in the laboratory (e.g. Bartholomew and Casey, 1978;reviewed in Dudley, 2000;Harrison and Roberts, 2000;Berwaerts et al, 2002;San Martin y Gomez and van Dyck, 2012). As proximate explanations for variation in flight performance, whole-animal metabolic rate and the activity of a key aerobic energy pathway enzyme (CCO) were also assessed.…”

Correction to ‘Adaptation to fragmentation: evolutionary dynamics driven by human influences’

“…sorting of dispersive genotypes in Aland archipelago metapopulations of Glanville fritillary butterfly [11]; evolution of mobility related morphology (with putative effect on dispersal) in a grasshopper [72]; selection for increased perceptual range in fragmented landscapes to reduce dispersal costs [73] demographic: allee effects small populations unable to attract pollinators variable herkogamy and autonomous selfing in small and large populations of Gentianella germanica [64] physical: edge effects increased niche breath none none community: altered biotic interactions loss of antagonistic interactions and trait evolution evolution of reduced mobility by relaxed selection from predators on islands [89] reduced defense in Ambrosia artemisiifolia in free enemy invasive areas [89]; rapid decrease in alewife gill-raker spacing caused by predation [90] loss of mutualistic interactions and trait evolution the absence of specialist bee pollinators leading to reduced herkogamy and higher autofertility in Clarkia [91] evolution of selfing in Centaurium erythraea in absence of pollinators [63]; rapid evolutionary changes in seed size consecutive to bird disperser extinction [77] altered multitrophic interactions and co-evolutionary dynamics morphological evolution in naturally clustered plants interacting with both herbivores and pollinators [92]; phytoplankton composition modifies predator-driven life history evolution in Daphnia [93];…”