Which finding, if true, would most directly support Mulder and Spellm…

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Mooseberry (Viburnum edule) plants are native to Alaska, where harsh conditions have historically impeded potential invasive species. As the boreal climate has warmed in recent decades, however, common knotgrass (Polygonum aviculare) plants have established themselves in Alaska. It has been suggested that warming-induced delays in the onset of subfreezing temperatures in autumn can benefit invasives more than native species; to evaluate this possibility, biologists Christa Mulder and Katie Spellman tracked V. edule and P. aviculare, along with other native and invasive species, over several years, concluding that invasives are advantaged by delays in subfreezing temperature onset in Alaska.

Which finding, if true, would most directly support Mulder and Spellman's conclusion?

Although V. edule and P. aviculare both tended to produce leaves later into autumn in years with late subfreezing temperature onset, the extension was much greater for P. aviculare than for V. edule.

Although significant interannual variations in subfreezing temperature onset were observed during the study, neither P. aviculare nor V. edule showed any significant interannual variation in the cessation of leaf production.

Although V. edule and P. aviculare tended to stop producing leaves at about the same time in years with historically typical temperature patterns, P. aviculare stopped producing leaves sooner than V. edule did in years with late subfreezing temperature onset.

Although V. edule and P. aviculare both tended to produce more leaves overall in years with late subfreezing temperature onset than they did in years with historically typical temperature patterns, the years with late subfreezing temperature onset also had early growing season onset in spring.