Environmental change often requires evolutionary responses, and therefore understanding the genetic architecture of susceptible populations is essential for predicting their capacity to respond adaptively. However, quantitative genetic studies are rarely targeted at populations considered vulnerable to such environmental perturbations. Here, we assess the level of heritable variation in the ability of embryos to tolerate desiccation stress in Pseudophryne guentheri, a terrestrial-breeding frog that is currently experiencing a drying climate. We applied a North Carolina II breeding design to identify sources of genetic and environmental variance, and genotype-by-environment interactions (GEIs), underlying the expression of embryo survival, hatching times, hatchling mass, size, and shape. Our analysis revealed highly significant effects of water potential and maternal effects on all measured traits, while additive genetic effects were significant for hatchling shape, and nonadditive effects were observed for embryo survival. Interestingly, GEIs, including for some traits complex three-way sire-by-dam-by-environment interactions, were significant, indicating that progeny from certain male-female crosses were more tolerant to water stress than others. These findings suggest a limited capacity of P. guentheri to respond to a drying climate, but also reveal that the detrimental effects of nonviable male-female crosses (i.e., genetic incompatibility) can be masked in benign environments.

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Oceans are a huge sink for the increased heat associated with anthropogenic climate change, and it is vital to understand the heat tolerance of marine organisms at all life stages to accurately predict species’ responses. In broadcast spawning marine invertebrates, reproduction is a vulnerable process in which sperm and eggs are released directly into the open water. Gametes are then exposed to fluctuating environmental conditions that may impact their fertilizing capacity. Using the broadcast spawning Mediterranean mussel, Mytilus galloprovincialis, as a model species, we performed blocks of factorial mating crosses to assess the variance in fertilization rates among individuals under both ambient and elevated temperatures. Overall, we found a small, but significant decline in fertilization rates with elevated temperatures. However, there was substantial plasticity in responses, with particular mussels having increased fertilization under elevated temperatures, although the majority showed decreased fertilization rates. Our results suggest possible future reproductive costs to ocean warming in M. galloprovincialis, although it is also possible that genetic variation for thermal sensitivity may allow for adaptation to changing environmental conditions.

Successful aquaculture operations strive to produce high-quality, healthy fish while minimizing costs. One way to do this is to wean fish off live feed as soon as possible to a formulated dry feed. In this study, Delta Smelt Hypomesus transpacificus were weaned onto a dry feed diet at three life stages: early larval (14 days posthatch [dph]), late larval (60 dph), and juvenile (105 dph), and compared to a control group of fish receiving live prey to 160 dph according to current practices. Delta Smelt did not have high survival or growth when dry feed was introduced at 14 dph, and showed significant increases in growth but low survival when the weaning process was started at 60 dph. Fish going through the experimental weaning process starting at 105 dph showed higher growth and survival rates than the control regime, indicating that this is a more optimal time to wean them off the live prey diet. Our findings suggest that Delta Smelt production methods could be improved by weaning fish earlier than the 160 dph currently implemented at the conservation hatchery.