Which of the following is not listed as a contributor to Franklin's bumblebee decline?

• A. Increased genetic diversity.
• B. Historically small effective population sizes.
• C. Environmental instability.
• D. Long-term reduced genetic diversity.

Answer: (D)

When studying declines in pollinators like Franklin's bumblebee, the big picture is that small, isolated populations experience genetic drift and inbreeding, environmental stress, and a loss of genetic diversity over time, all of which reduce a population’s fitness and ability to cope with change. Increased genetic diversity, however, would generally bolster a population’s resilience, not contribute to its decline. More diversity means more potential immune variation, better adaptation to changing conditions, and less inbreeding depression, helping the population persist.

The other factors described align with known risks: historically small effective population sizes amplify drift and inbreeding, environmental instability creates fluctuating resources and habitats that stress populations, and long-term reduced genetic diversity is a consequence of bottlenecks and drift that lowers adaptability.