**Article Title:** An experimentally introduced population of *Brassica rapa* (Brassicaceae). 2. Rapid evolution of phenotypic traits **Authors:** Michael R. Sekor and Steven J. Franks **Source:** *Plant Ecology and Evolution*, 2018, Vol. 151, No. 3, pp. 293-302 **Published by:** Royal Botanical Society of Belgium and the Botanic Garden Meise **URL:** [https://www.jstor.org/stable/14945392](https://www.jstor.org/stable/14945392) --- **Abstract:** **Background and aims:** Introduced populations can potentially experience strong selection and rapid evolution. While some retrospective studies have shown rapid evolution in introduced populations in the past, few have directly tested for and characterized evolution as it occurs. Here we put an experimental introduction to observe and quantify evolution of multiple traits in a plant population introduced to a novel environment. **Methods:** We experimentally introduced seeds of the annual plant *Brassica rapa* L. (Brassicaceae) from a location in southern California into multiple replicated plots in New York. We allowed the populations to naturally evolve. Following the introduction approach, we compared ancestral and descendant plants grown for three generations in New York to main phenotypic traits. **Key results:** Within only three generations, there was significant evolution of several morphological, phenological, and fitness traits, as well as substantial variation among families. Selection for lower size during the three generations following introduction, there was evolution of smaller size, earlier flowering, and a larger duration of flowering. Although there were rapid evolutionary changes in traits, descendants did not have greater fitness than ancestors in New York, indicating a lack of evidence for adaptive evolution, at least over this time-frame of the study. **Conclusions:** This study found rapid evolution of several morphological and phenological traits, including smaller plant size and shorter time to flowering, following introduction, confirming that evolution can rapidly occur during the early stages of colonization. Markers were utilized in the comparison between ancestors and contemporary descendant samples, which shows that the resurrection approach can unveil unexpected evolutionary changes and can be very useful for studying contemporary evolution. **Key words:** Rapid evolution, plant, resurrection approach, morphology, flowering time, *Brassica rapa*, experimental introduction, introduced species. --- **Introduction:** The image includes text detailing a scientific study on the rapid evolution **Introduction:** Recent studies have shown substantial evidence that rapid evolution can occur in natural populations over short timescales. This process is particularly noted when there is a mismatch between organisms and their environments, often caused by anthropogenic changes such as climate change or pesticide use. Research indicates that rapid evolution is most evident in introduced populations, especially in invasive species. However, the specific mechanisms of fast-paced evolution in these cases remain not entirely understood. **Table 1 – Summary of Environmental Variables in the Source and Introduced Environment:** - **Source Environment:** - **State:** California - **Latitude:** 33.661 - **Longitude:** -117.851 - **Climate type:** Mediterranean - **Soil type:** Clay loam - **Vegetation type:** Mediterranean Coastal Scrub - **Growing season dates:** December–April - **Average high/low temp in January:** 19°C/9°C - **Average high/low temp in July:** 26°C/19°C - **Average precipitation in January:** 7.6 cm - **Average precipitation in July:** 0 cm - **Introduced Environment:** - **State:** New York - **Latitude:** 41.127 - **Longitude:** -73.737 - **Climate type:** Temperate - **Soil type:** Loam - **Vegetation type:** Eastern Deciduous Forest - **Growing season dates:** April–September - **Average high/low temp in January:** 4°C/-5°C - **Average high/low temp in July:** 28°C/19°C - **Average precipitation in January:** 9.6 cm - **Average precipitation in July:** 10.1 cm **Summary:** The study investigates rapid evolution in experimentally introduced populations of plants. Using techniques like reciprocal transplantations and experimental introductions, researchers aim to understand the evolutionary processes in newly inhabited environments versus the original habitats. This involves studying various traits and survival strategies of plants over time and space, observing how they adapt to different climates and conditions.