Abstract
Human-induced global climate change is exerting increasingly strong selective pressures on a myriad of fitness traits that affect organisms. These traits, in turn, are influenced by a variety of environmental parameters such as temperature and precipitation, particularly in ectothermic taxa such as amphibians and reptiles. Over the past several decades, severe and prolonged episodes of drought are becoming commonplace throughout North America. Documentation of responses to this environmental crisis, however, is often incomplete, particularly in cryptic species. Here, we investigated reproduction in a population of pitviper snakes (copperhead, Agkistrodon contortrix), a live-bearing capital breeder. This population experienced a severe drought from 2012 through 2016. We tested whether declines in number of progeny were linked to this drought. Decline in total number offspring was significant, but offspring length and mass were unaffected. Reproductive output was positively impacted by precipitation and negatively impacted by high temperatures. We hypothesized that severe declines of prey species (e.g., cicada, amphibians, and small mammals) reduced energy acquisition during drought, negatively impacting reproductive output of the snakes. Support for this view was found using the periodical cicada (Magicicada spp.) as a proxy for prey availability. Various climate simulations, including our own qualitative analysis, predict that drought events will continue unabated throughout the geographic distribution of copperheads which suggests that long-term monitoring of populations are needed to better understand geographic variation in drought resilience and cascading impacts of drought phenomena on ecosystem function.
Highlights
The onset of the Anthropocene has ushered in an epoch defined by rapid, human-induced global climate change[1], for which profound negative effects on the health, survival, and diversity of Earth’s biota are projected[2,3,4,5,6,7]
Because many ectothermic taxa are capital breeders and reproduction in females is dependent on energy acquired in previous seasons[41,42,59,60,61], we investigated whether a food staple of copperheads[62], the northern 17-year periodical cicada (Magicicada), was linked with specific reproductive parameters in copperheads [Fig. S1]
In 2018, the first year following a return to normal precipitation, a substantial increase in the number of pregnant females (N = 16) conferred an increase in total progeny N = 100, mean = 6.25) compared with 2016 (N = 1 reproductive female, 5 total progeny) and 2017 (N = 0 females and 0 total progeny)
Summary
The onset of the Anthropocene has ushered in an epoch defined by rapid, human-induced global climate change[1], for which profound negative effects on the health, survival, and diversity of Earth’s biota are projected[2,3,4,5,6,7]. As ectotherms, life-history traits (e.g., maturity, fecundity, and offspring size) of amphibians[22,31,32,33] and reptiles[34,35,36] are strongly influenced by climate and weather, temperature and precipitation[19,37]. During unfavorable conditions these taxa are especially prone to alter or entirely shut down reproduction as a trade-off[38,39]. To the best of our knowledge, similar assessments have not been performed on North American pitvipers
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