In a hypothetical species of butterfly, wing spots are controlled by a single locus where BB individuals have blue spots, YY individuals have yellow spots, and BY individuals have green spots. Ten years ago, a previous collector randomly collected 1000 butterflies and reported finding 90 blues, 420 greens, and 490 yellows. You collect 40 blues, 320 greens, and 640 yellows. Has there been evolution in this population? If yes, is natural selection involved?
I have had many attempts at this question I calculated the p and q frequency for each using HW model.
For 10 years ago: 90+90+420/2000=0.3 BB 490+490+420/2000=0.7 YY
For now : 40+40+320/2000=0.2 BB 640+640+320/2000= 0.8YY
But I dont think I can know if evolution happened and natural selection from this (because Y allele in yellow for instance includes heterozygotes as well).
What do I do? Do I calculate the expected number of each and put it in Chi square test but how would I get natural selection from that? Please help