Urban heat island conditions experienced by the Western black widow spider (Latrodectus hesperus): Extreme heat slows development but results in behavioral accommodations

Abstract

While shifts in organismal biology stemming from climate change are receiving increased attention, we know relatively little about how organisms respond to other forms of anthropogenic disturbance. The urban heat island (UHI) effect describes the capture of heat by built structures (e.g. asphalt), resulting in elevated urban temperatures. The UHI is a well-studied phenomenon, but only a handful of studies have investigated trait-based shifts resulting from the UHI, and even fewer have attempted to quantify the magnitude of the UHI experienced at the microclimate scale. Here, using a common urban exploiter, the Western black widow spider ( Latrodectus hesperus ), we show that the UHI experienced by spiders in July in their urban Phoenix, AZ refuges is 6°C hotter (33°C) than conditions in the refuges of spiders from Sonoran Desert habitat outside of Phoenix’s development (27°C). We then use this field microclimate UHI estimate to compare the development speed, mass gain and mortality of replicate siblings from 36 urban lineages reared at ‘urban’ and ‘desert’ temperatures. We show that extreme heat is slowing the growth of spiderlings and increasing mortality. In contrast, we show that development of male spiders to their penultimate moult is accelerated by 2 weeks. Lastly, in terms of behavioral shifts, UHI temperatures caused late-stage juvenile male spiders to heighten their foraging voracity and late-stage juvenile female spiders to curtail their web-building behavior. Trait-based approaches like the one presented herein help us better understand the mechanisms that lead to the explosive population growth of urban (sometimes invasive) species, possibly at the expense of urban biodiversity. Studies of organismal responses to the present day UHI can be used as informative surrogates that help us grasp the impact that projected climate change will have on biodiversity.

Heat wave effects on the behavior and life-history traits of sedentary antlions

“…Other taxa seem to show similar reactions to heat waves to those reported for the E. nostras antlions herein. For example, in Sitobion grain aphids and Western black widow spiderlings, exposure to heat waves prolonged their developmental time ( Jeffs and Leather 2013 ; Johnson et al 2019 ). In fact, the disruption of life histories, especially in terms of life stage shifts, is postulated to be one of the main consequences of extreme climatic events ( Wingfield et al 2016 ).…”

Spatiotemporal variability of urban heat island: Influence of urbanization on seasonal pattern of land surface temperature in the Metropolitan Region of Belém, Brazil

“…In this way, the stronger negative correlation between mean NDVI and mean LST was also expected, since higher NDVI values signify healthier vegetation, improved photosynthesis, and fuller leaf canopies (Kaplan et al, 2018). In fact, important research remains on how to maximize NDVI values in urban ecosystems, but the literature suggests increasing native species (e.g., flora and fauna) richness, complexity, and diversity (Johnson et al, 2019). However, landscape compositions lack detailed information needed by engineers, architects, urban planners, and designers to create solutions in complex urban settings (Lemonsu et al, 2015;Soltani and Sharifi, 2017).…”

Human Impact Enables an Ecological Niche Shift for Invasive Widow Spiders

“…Moreover, since urban areas are known to be heat islands across seasons [102], high HFP could also buffer invasive redback populations against low winter temperatures, although there is currently little information available on this effect for spiders. A group of studies on the desert-adapted North American species Latrodectus hesperus indicate that populations thrive in urban heat island habitats (within its native range [103][104][105]). In the case of L. hesperus, however, urban spiders experience higher temperatures relative to natural habitats (rather than decreased minimum temperatures, as for redbacks in the invasive range), and this change is associated with reduced survival, poor nutritional condition, but also accelerated development and foraging activity, along with other behavioral changes which may allow persistence [105].…”