Local adaptation of reproductive performance during thermal stress

Abstract

Considerable evidence exists for local adaptation of critical thermal limits in ectotherms following adult temperature stress, but fewer studies have tested for local adaptation of sublethal heat stress effects across life-history stages. In organisms with complex life cycles, such as holometabolous insects, heat stress during juvenile stages may severely impact gametogenesis, having downstream consequences on reproductive performance that may be mediated by local adaptation, although this is rarely studied. Here, we tested how exposure to either benign or heat stress temperature during juvenile and adult stages, either independently or combined, influences egg-to-adult viability, adult sperm motility and fertility in high-and low-latitude populations of Drosophila subobscura. We found both population-and temperaturespecific effects on survival and sperm motility; juvenile heat stress decreased survival and subsequent sperm motility and each trait was lower in the northern population. We found an interaction between population and temperature on fertility following application of juvenile heat stress; although fertility was negatively impacted in both populations, the southern population was less affected. When the adult stage was also subject to heat stress, the southern population exhibited positive carry-over effects whereas the northern population's fertility remained low. Thus, the northern population is more susceptible to sublethal reproductive consequences following exposure to juvenile heat stress. This may be common in other organisms with complex life cycles and current models predicting population responses to climate change, which do not take into account the impact of juvenile heat stress on reproductive performance, may be too conservative.

Temperature fluctuations during development reduce male fitness and may limit adaptive potential in tropical rainforest Drosophila

“…Latitudinal clines in responses to thermal stress have been observed in D. subobscura (Porcelli et al ., ). However, there is little evidence for local adaptation in male thermal stress across shorter distances, even when – as in this case – thermal regimes vary at similar magnitudes locally to those observed across a given species' latitudinal range.…”

Hawaiian picture‐winged Drosophila exhibit adaptive population divergence along a narrow climatic gradient on Hawaii Island

“…Understanding how species respond to climate change is a pertinent theoretical question and an immediate conservation priority (Hoffmann & Sgrò 2011;Kellermann et al, 2009;Porcelli, Gaston, Butlin, & Snook, 2017). A recent study of two Hawaii Island endemic picture-winged Drosophila, the rare D. silvestris and the more ubiquitous D. sproati, found strong species-level differences in temperature tolerance (Uy et al, 2015), and previously observed clinal patterns of genetic differentiation in D. silvestris (Craddock & Carson 1989) suggest that temperature may also be driving adaptive population divergence.…”

Honey bee queens are vulnerable to heat-induced loss of fertility

“…Honey bee queens (Kona Queens supplied in a single shipment) were treated at one of five different temperatures (5,10,15,25,38,40, and 42 ͦ C) for 1, 2, or 4 hours, then held at 25 ͦ C for 2 d. Fourteen queens (replicates) were included in the 25 ͦ C treatment (negative control), whereas 8-9 queens were included in all other temperatures and exposure durations (see Table 1 for replication information). Following this, queens were beheaded, and their spermathecae were dissected with fine forceps.…”

“…Climate change is threatening biodiversity around the globe [1][2][3] , and one potential driver is through heatinduced reductions in fertility [4][5][6] . The impact of heat on fertility is far-reaching in the animal kingdom, affecting mammals [7][8][9][10][11] , birds 12 , fish 13 , nematodes 14 , and insects 4,[15][16][17][18][19][20][21] . At temperatures of 40-43 ͦ C, spermatogenesis is compromised 22 , sperm viability drops 4,18,19 , sperm are less competitive 4 , and motility is compromised 15,23,24 .…”

“…The impact of heat on fertility is far-reaching in the animal kingdom, affecting mammals [7][8][9][10][11] , birds 12 , fish 13 , nematodes 14 , and insects 4,[15][16][17][18][19][20][21] . At temperatures of 40-43 ͦ C, spermatogenesis is compromised 22 , sperm viability drops 4,18,19 , sperm are less competitive 4 , and motility is compromised 15,23,24 . Extreme weather events such as heatwaves are increasing in frequency and severity [25][26][27] , which could have widespread effects on populations via reduced reproductive output [4][5][6] .…”