Selection and evolution: explain question

In a study of flower petal length, samples were taken from a wild population and a cultivated population of the same plant species. The data are shown below.

The t-test formula is: $t = \frac{\bar{x}_1 - \bar{x}_2}{\sqrt{\frac{s_1^2}{n_1} + \frac{s_2^2}{n_2}}}$

A student calculated the t-value as 4.63. The critical value for a two-tailed test at the 5% significance level with 18 degrees of freedom is 2.10.

Explain what this result indicates about the variation in petal length between the two populations. Refer to the concepts of continuous variation and the roles of genetic and environmental factors in your answer.