Question

twinflower (linnaea borealis) plants are native to alaska, where harsh conditions have historically impeded potential invasive species. as the boreal climate has warmed in recent decades, however, narrowleaf hawksbeard (crepis tectorum) 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 l. borealis and c. tectorum, 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 spellmans conclusion? a) although l. borealis and c. tectorum 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. b) although significant interannual variations in subfreezing temperature onset were observed during the study, neither c. tectorum nor l. borealis showed any significant interannual variation in the cessation of leaf production. c) although l. borealis and c. tectorum tended to stop producing leaves at about the same time in years with historically typical temperature patterns, c. tectorum stopped producing leaves sooner than l. borealis did in years with late subfreezing temperature onset. d) although l. borealis and c. tectorum both tended to produce leaves later into autumn in years with late subfreezing temperature onset, the extension was much greater for c. tectorum than for l. borealis.

Explanation:

The conclusion is that invasive species in Alaska are advantaged by delays in sub - freezing temperature onset. Option D shows that the invasive C. tectorum has a much greater extension of leaf - production into autumn in years with late sub - freezing temperature onset compared to the native L. borealis, directly supporting the idea that invasives benefit from such delays.

Answer:

D. Although L. borealis and C. tectorum both tended to produce leaves later into autumn in years with late subfreezing temperature onset, the extension was much greater for C. tectorum than for L. borealis.