Invasive species that penetrate habitat boundaries are likely to experience strong selection and rapid evolution. This study documents evolutionary shifts in tolerance and performance following the invasion of fresh water by the predominantly estuarine and salt marsh copepod Eurytemora affinis. Common-garden experiments were performed on freshwater-invading (Lake Michigan) and ancestral saline (St. Lawrence marsh) populations to measure shifts in adult survival (at 0, 5, and 25 PSU), and survival during development and development time (both using full-sib clutches split across 0, 5, 15, and 25 PSU). Results showed clear evidence of heritable shifts in tolerance and performance associated with freshwater invasions. The freshwater population exhibited a gain in low-salinity tolerance and a reduction in high-salinity tolerance relative to the saline population, suggesting tradeoffs. These tradeoffs were supported by negative genetic correlations between survival at fresh (0 PSU) versus higher salinities. Mortality in response to salinity occurred primarily before metamorphosis, suggesting that selection in response to salinity had acted primarily on the early life-history stages. The freshwater population exhibited curious patterns of life-history evolution across salinities, relative to the saline population, of retarded development to metamorphosis but accelerated development from metamorphosis to adulthood. This pattern might reflect tradeoffs between development rate and survival in fresh water at the early life-history stages, but some other selective force acting on later life-history stages. Significant effects of clutch (genotype) and clutch-by-salinity interaction (G × E) on survival and development time in both populations indicated ample genetic variation as substrate for natural selection. Variation for high-salinity tolerance was present in the freshwater population despite negative genetic correlations between high- and low-salinity tolerance. Results implicate the importance of natural selection and document the evolution of reaction norms during freshwater invasions.

While natural selection might in some cases facilitate invasions into novel habitats, few direct measurements of selection response exist for invasive populations. This study examined selection response to changes in salinity using the copepod Eurytemora affinis. This copepod has invaded fresh water from saline habitats multiple times independently throughout the Northern Hemisphere. Selection response to a constant intermediate salinity (5 PSU) was measured in the laboratory for saline source and freshwater invading populations from the St. Lawrence drainage (North America). These populations were reared under three conditions: (1) native salinities (0 or 15 PSU) for at least two generations, (2) 5 PSU for two generations, and (3) 5 PSU for six generations. Full-sib clutches taken from populations reared under these three conditions were split across four salinities (0, 5, 15, and 25 PSU) to determine reaction norms for survival and development time. Contrasts in survival and development time across the three rearing conditions were treated as the selection response. Selection at 5 PSU resulted in a significant decline in freshwater (0 PSU) tolerance for both the saline and freshwater populations. Yet, evolutionary differences in freshwater tolerance persisted between the saline and freshwater populations. The saline and freshwater populations converged in their high-salinity (25 PSU) tolerance, with an increase in the freshwater population and decline in the saline population. Development time did not shift greatly in response to selection at 5 PSU. For all three rearing conditions, the freshwater population exhibited retarded larval development and accelerated juvenile development relative to the saline population. Results from this study indicate that both the saline and freshwater populations exhibit significant responses to selection for a fitness-related trait critical for invasions into a novel habitat.

Summary1. Agriculture comprises the largest global land use, makes it a leading cause of habitat loss. It is therefore critical to identify how to best construct agricultural systems that can simultaneously provide food and other ecosystem services. This challenge requires that we determine how to maximize win-win relationships and minimize trade-offs between services. 2. Through meta-analysis, we tested whether within-field crop diversification (polyculture) can lead to win-win relationships between two ecosystem services: yield of a focal crop species and biocontrol of crop pests. We selected only studies that recorded both services (N = 26 studies; 301 observations), allowing us to better determine the underlying mechanisms of our principal findings. We calculated log-response ratios for both ecosystem services in monoand polycultures. 3. We found win-win relationships between per-plant yield of the primary crop and biocontrol in polyculture systems that minimized intraspecific competition via substitutive planting. Additionally, we found beneficial effects on biocontrol with no difference in per-unit area yield of the primary crop in polyculture fields at high cropping densities (additive planting) where legumes were used as the secondary crop. These results suggest that there is a strong potential for win-win relationships between biocontrol and per-unit area yield under certain scenarios. Our findings were consistent across geographical regions and by type of primary crop. We did not find evidence that biocontrol had an effect on yield, but rather, both were independently affected by polycultural cropping. 4. Synthesis and applications. We show that well-designed polycultures can produce win-win outcomes between per-plant, and potentially per-unit area, primary crop yield and biocontrol. Biocontrol services are consistently enhanced in polycultures, so polyculture management that focuses on yield optimization is likely to be the best strategy for maximizing both services. In doing so, we suggest that practitioners utilize polycultures that decrease plant-plant competition through a substitution of relatively large quantities of the primary crop for compatibly harvestable secondary crops. Additionally, if planting at high cropping densities, it is important that legumes be the secondary crop.

Genetic factors have been estimated to account for at least 30% of a woman’s risk to develop breast cancer. We have developed a rat model using Wistar Furth (WF) and Wistar Kyoto (WKy) strains to genetically identify mammary cancer susceptibility loci. The WKy allele of the mammary carcinogenesis susceptibility locus Mcs5c, was previously shown to reduce carcinoma multiplicity after 7,12-dimethylbenz-[a] anthracene (DMBA) exposure. In this study, Mcs5c was fine-mapped using WF.WKy congenic lines. Mcs5c was located to a region of approximately 176 Kb on rat chromosome 5. One of the Mcs5c congenic lines containing a narrow Mcs5c WKy interval displayed a 40% decrease in average carcinoma number compared to WF-homozygous congenic controls after mammary carcinogenesis induction using two different models. As genetically mapped, the Mcs5c locus is located in a gene desert and thus is devoid of genes and annotated RNAs; thus, a genetic element in Mcs5c was hypothesized to regulate the expression of genes outside the locus. Tenascin c (Tnc) was identified as a candidate gene due to its reduced expression in thymus and ovarian tissues of Mcs5c WKy-homozygous congenic females compared to WF-homozygous congenic controls. This allele specific differential expression is environmentally controlled.

The BP Deepwater Horizon Oil Disaster was the most catastrophic offshore oil spill in U.S. history, yet we still have a poor understanding of how organisms could evolve in response to the toxic effects of crude oil. This study offers a rare analysis of how fitness‐related traits could evolve rapidly in response to crude oil toxicity. We examined evolutionary responses of populations of the common copepod Eurytemora affinis residing in the Gulf of Mexico, by comparing crude oil tolerance of populations collected before versus after the Deepwater Horizon oil spill of 2010. In addition, we imposed laboratory selection for crude oil tolerance for ~8 generations, using an E. affinis population collected from before the oil spill. We found evolutionary increases in crude oil tolerance in the wild population following the oil spill, relative to the population collected before the oil spill. The post‐oil spill population showed increased survival and rapid development time in the presence of crude oil. In contrast, evolutionary responses following laboratory selection were less clear; though, development time from metamorphosis to adult in the presence of crude oil did become more rapid after selection. We did find that the wild population, used in both experiments, harbored significant genetic variation in crude oil tolerance, upon which selection could act. Thus, our study indicated that crude oil tolerance could evolve, but perhaps not on the relatively short time scale of the laboratory selection experiment. This study contributes novel insights into evolutionary responses to crude oil, in directly examining fitness‐related traits before and after an oil spill, and in observing evolutionary responses following laboratory selection.