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Abstract Considerable research describes the interactions between seagrasses and their sedimentary environment, but there is little information on how populations differ in their innate versus plastic responses to these differences. Here, we test whether sediment contributes to eelgrass population differentiation and the nature of plastic responses to different sediment environments. We do this via a 15-week, fully crossed common garden experiment with two populations and their native sediment types. Plants from the warmer-temperature, clay-dominated site (90% silt + clay, 10% sand) consistently maintained greater biomass than plants from the cooler, sand-dominated site (60% sand, 40% silt + clay). Plants from both populations were highly plastic for root length and clonal shoot size, with both increasing when planted in clay-dominated compared to sand-dominated sediment. Plants from the clay-dominated site grew longer rhizomes in foreign sediment while plants from the sand-dominated site had no change in this plant trait, indicating some measure of home site advantage with respect to sediment conditions. Porewater sulfide also exhibited this pattern where concentrations were very low in clay-dominated sediment for all plants, but in the sand-dominated treatment, only plants native to sand-dominated sediment maintained porewater sulfide concentrations below toxic levels. These patterns may be mediated by microbiome differences between populations as roots from plants native to clay-dominated sediment had more fixed microbiomes between treatments compared to plants native to sand-dominated sediment. These results support that sediment type partially mediates home site advantage in eelgrass populations and suggest differential population responses may be mediated by the associated microbiome. 

Megachile rotundata exhibits a facultative prepupal diapause but the cues regulating diapause initiation are not well understood. Possible cues include daylength and temperature. Megachile rotundata females experience changing daylengths over the nesting season that may influence diapause incidence in their offspring through a maternal effect. Juvenile M . rotundata spend their developmental period confined in a nesting cavity, potentially subjected to stressful temperatures that may affect diapause incidence and survival. To estimate the impact of daylength and nest cavity temperature on offspring diapause, we designed a 3D printed box with iButtons that measured nest cavity temperature. We observed nest building throughout the season, monitored nest cavity temperature, and followed offspring through development to measure diapause incidence and mortality. We found that daylength was a cue for diapause, and nest cavity temperature did not influence diapause incidence. Eggs laid during long days had a lower probability of diapause. Siblings tended to have the same diapause status, explaining a lot of the remaining variance in diapause incidence. Some females established nests that contained both diapausing and nondiapausing individuals, which were distributed throughout the nest. Nest cavities reached stressful temperatures, which decreased survival. Mortality was significantly higher in nondiapausing bees and the individuals that were laid first in the nest. In conclusion, we demonstrate a maternal effect for diapause that is mediated by daylength and is independent of nest box temperature. 

Abstract The temperature of the nest influences fitness in cavity-nesting bees. Females may choose nest cavities that mitigate their offspring’s exposure to stressful temperatures. This study aims to understand how cavity temperature impacts the nesting preference of the solitary bee Megachile rotundata (Fabricius) under field conditions. We designed and 3D printed nest boxes that measured the temperatures of 432 cavities. Nest boxes were four-sided with cavity entrances facing northeast, northwest, southeast, and southwest. Nest boxes were placed along an alfalfa field in Fargo, ND and were observed daily for completed nests. Our study found that cavity temperature varied by direction the cavity faced and by the position of the cavity within the nest box. The southwest sides recorded the highest maximum temperatures while the northeast sides recorded the lowest maximum temperatures. Nesting females filled cavities on the north-facing sides faster than cavities on the south-facing sides. The bees preferred to nest in cavities with lower average temperatures during foraging hours, and cavities that faced to the north. The direction the cavity faced was associated with the number of offspring per nest. The southwest-facing cavities had fewer offspring than nests on the northeast side. Our study indicates that the nesting box acts as a microclimate, with temperature varying by position and direction of the cavity. Variation in cavity temperature affected where females chose to nest, but not their reproductive investment.