How is adaptive potential distributed within species ranges?

Quantitative genetic variation (QGV) represents a major component of adaptive potential and, if reduced toward range-edge populations, could prevent a species' expansion or adaptive response to rapid ecological change. It has been hypothesized that QGV will be lower at the range edge due to small populations-often the result of poor habitat quality-and potentially decreased gene flow. However, whether central populations are higher in QGV is unknown. We used a meta-analytic approach to test for a general QGV-range position relationship, including geographic and climatic distance from range centers. We identified 35 studies meeting our criteria, yielding nearly 1000 estimates of QGV (including broad-sense heritability, narrow-sense heritability, and evolvability) from 34 species. The relationship between QGV and distance from the geographic range or climatic niche center depended on the focal trait and how QGV was estimated. We found some evidence that QGV declines from geographic centers but that it increases toward niche edges; niche and geographic distances were uncorrelated. Nevertheless, few studies have compared QGV in both central and marginal regions or environments within the same species. We call for more research in this area and discuss potential research avenues related to adaptive potential in the context of global change.

Evidence for adaptive responses to historic drought across a native plant species range.

As climatic conditions change, species will be forced to move or adapt to avoid extinction. Exacerbated by ongoing climate change, California recently experienced a severe and exceptional drought from 2011 to 2017. To investigate whether an adaptive response occurred during this event, we conducted a "resurrection" study of the cutleaf monkeyflower (Mimulus laciniatus), an annual plant, by comparing trait means and variances of ancestral seed collections ("pre-drought") with contemporary descendant collections ("drought"). Plants were grown under common conditions to test whether this geographically restricted species has the capacity to respond evolutionarily to climate stress across its range. We examined if traits shifted in response to the recent, severe drought and included populations across an elevation gradient, including populations at the low- and high-elevation edges of the species range. We found that time to seedling emergence in the drought generation was significantly earlier than in the pre-drought generation, a response consistent with drought adaptation. Additionally, trait variation in days to emergence was reduced in the drought generation, which suggests selection or bottleneck events. Days to first flower increased significantly by elevation, consistent with climate adaptation across the species range. Drought generation plants were larger and had greater reproduction, which was likely a carryover effect of earlier germination. These results demonstrate that rapid shifts in trait means and variances consistent with climate adaptation are occurring within populations, including peripheral populations at warm and cold climate limits, of a plant species with a relatively restricted range that has so far not shifted its elevation distribution during contemporary climate change. Thus, rapid evolution may mitigate, at least temporarily, range shifts under global climate change. This study highlights the need for better understanding rapid adaptation as a means for plant communities to cope with extraordinary climate events.

Effect of natural exposure to vaccine-derived North American genotype PRRS virus on the serological response in naïve pigs.

Diagnosis of porcine reproductive and respiratory syndrome virus (PRRSV) is often performed by serological testing, but ELISA does not differentiate between infections with wild-type or vaccine virus. Two attenuated live vaccines [European (EU) or North American (NA) genotype] are used. In addition to wild-type isolates, vaccine or vaccine-derived viruses occur frequently. This is often not considered when the ELISA results are used to differentiate between epizootic and enzootic infections. In this study, an infection with the NA genotype vaccine-derived virus was detected in two herds previously PRRSV negative and ELISA results [sample to positive (s/p) ratios] were analysed. The virus was identified by RT-PCR and nucleotide sequences of ORF5 had 97% (herd A) and 99% (herd B) identity with the genome of a ML PRRSV vaccine belonging to the NA genotype. Pigs of different age became positive with an average s/p ratio of 2.24 (A) and 1.18 (B). The data clearly demonstrate that spontaneous infection with a vaccine-derived virus of the NA genotype induces ELISA s/p ratios similar to those induced by vaccination or by infection with wild-type virus. We conclude that for a correct interpretation of serological results the circulation of vaccine or vaccine-derived virus isolates has to be excluded by RT-PCR, even if vaccination is not ongoing.