Microclimatic buffering in forest, agricultural, and urban landscapes through the lens of a grass‐feeding insect

Abstract

For small ectotherm species, dealing with microclimatic variation during sensitive stages of their development is a critical component of their ecological interactions within and among different landscape settings. However, it is often unknown whether the use of habitats in different landscape settings may affect microclimatic conditions at the level of microhabitats (e.g., at host plants for herbivorous insects). As opposed to standard ecological monitoring experiments, we aim to identify the microclimatic variables that accurately represent the environment in which a small arthropod spends most of its life. As a case study, we selected grassy sites that corresponded to the microhabitat of grass-feeding insects in general, and larvae of the butterfly Pararge aegeria in particular, as this insect recently expanded its habitat use from forest (edges) to agricultural and urban environments. We tested the extent to which local microclimates and microclimatic buffering capacity differed between tufts of grass in forest and in two anthropogenic (i.e., agricultural and urban) landscape settings by measuring microclimatic variables with sensors at the level of the grasses. We compared temperature, relative humidity, and vapor pressure deficit (VPD) during an exceptionally warm and dry summer period with parallel data from weather stations and tested for differences between microclimatic profiles among the three landscape settings. Microclimatic conditions correspond only partly to variables based on weather station data. Differences are particularly significant for relative humidity and VPD, but not for day and night temperatures. Effects of canopy openness on the variability of microclimatic variables are landscape-specific. Host plants in agricultural settings experience strong microclimatic fluctuations and low short-term variability in VPD. In urban settings, urban heat island effects increase night temperature but also show microclimatic buffering effects similar to the ones in forest settings. Our findings stress the functional implications of landscape-specific microclimatic profiles at the appropriate organism-centered scale. We discuss

Continent‐wide parallel urban evolution of increased heat tolerance in a common moth

“…( 2019 ), for a similar reasoning regarding Drosophila melanogaster ). This, in combination with some scope for larval behavioral thermoregulation by moving toward lower and cooler positions within the evapotranspiration‐ and shade‐providing grass sward (Braem et al., 2023 ), could mean that the larval heat tolerance limit is not often reached—meaning no selection for increased heat tolerance—even in the hotter urban environments. While the scope for larval behavioral thermoregulation within the vegetation may be similar in urban and non‐urban grasslands, the scope for adult behavioral thermoregulation may be lower in urban settings because this happens at a larger spatial scale, and suitable habitat—within the hot urban matrix—is typically reduced and more fragmented in urban settings (Merckx et al., 2018 ).…”

“…Under global change, the frequency and intensity of high temperatures have increased and continue to increase, particularly in thermally stressful environments like grasslands and cities. This has obvious fitness consequences for grassland Lepidoptera and other insect taxa (Ma et al., 2021 ), especially since microclimate is far more relevant than the background climate for relatively small organisms such as insects (Braem et al., 2023 ; Suggitt et al., 2011 ). Because thermal extremes are key causes of insect responses to global change (Ma et al., 2021 ) and are known to induce evolution of thermal tolerance (Buckley & Huey, 2016 ; Hoffmann et al., 2013 ), we believe that the relative difference in tolerance of extreme temperatures we find here will be relevant to ecological and evolutionary processes in nature.…”

Topography influences diurnal and seasonal microclimate fluctuations in hilly terrain environments of coastal California

“…These features give rise to spatio-temporal heterogeneity expressed on local scales, affecting minimum and maximum temperatures, and the resulting magnitude of diurnal (daily maximum vs. minimum) and seasonal (summer vs. winter) temperature variations [9,17]. Furthermore, the resulting minimum and maximum extreme temperatures, are known to structure plant and animal distributions [18][19][20]. In topographically heterogeneous landscapes in particular, steep topographic gradients create strong microclimate heterogeneity [21].…”

“…When a location has a high buffering capacity, it can effectively reduce the magnitude of temperature variations, providing more stable and moderated temperature conditions. Alternatively, a reduced buffering capacity implies that the location is less effective at mitigating temperature fluctuations, resulting in more pronounced and variable temperature changes [20]. Vegetation canopies have important buffering effects, with lower daytime maxima and higher nighttime minima [24][25][26], and buffering of temperature extremes in comparison with a forest clearing e.g., clearcuts [27][28][29].…”

Effects of microclimate on disease prevalence across an urbanization gradient

“…Importantly, urbanization is a process that produces not only landscape‐level changes but also a high degree of heterogeneity in natural and built features at local scales within and between urbanized habitats (Cadenasso et al, 2007). Habitat heterogeneity within urban settings has the potential to impact the timing, likelihood, and outcome of the myriad species interactions that contribute to ecosystem functioning (e.g., pollination; Theodorou et al, 2022), herbivory (Braem et al, 2023; Egerer et al, 2017), predation (Kotze et al, 2022), and parasitism (Murdock et al, 2017; van Dijk et al, 2022). However, a major challenge for understanding how urbanization alters species interactions is to determine how the effects of environmental factors vary across spatial scales, from landscapes to microhabitats.…”