Ecology 19. Which best describes Lack\'s tradeoff? (a) Offspring number versus o

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Ecology 19. Which best describes Lack's tradeoff? (a) Offspring number versus offspring survival (b) Reproducing this year versus survival and/or reproduction in future years (c) Juvenile survival versus adult reproduction (d) Adult survival to next breeding season versus fecundity next breeding season 20. Consider a sympatric species pairs of Benthic and Limnetic sticklebacks in a lake in British Columbi All freshwater sticklebacks in this part of the world arose from Marine ancestors, so Marine sticklebacks are the outgroup. There are two proposed hypotheses for their origins. 1. Marines colonized (invaded) the lake twice. The first colonization event resulted in the evolution of Benthic sticklebacks, and the second colonization event resulted in the evolution of limnetic sticklebacks. 2 Marines colonized the lake, and subsequently Benthics and Limnetics diverged from each other withi the lake via sympatric speciation. Which phylogenetic tree below would you expect if hypothesis 1 or hypothesis 2 is true? Benthic Marine Limnetic Benthic (a) Hypothesis 1 would be supported by phylogeny A; and Hypothesis 2 would be supported by phylogenyB (b) Hypothesis 1 would be supported by phylogeny B; and, Hypothesis 2 would be supported by phylogeny A (c) Both a and b are false (d) You cannot address this question with phylogenetic trees 21. The genus of flies, known as Rhagoletis, forms two genetically distinct populations. One of the populations lives on hawthorn trees; the other on apple trees. Because these two species of host plants have different flowering times, these two populations of flies are reproductively isolated. This f species is exhibiting (a) Sympatric speciation (b) Parapatric speciation (c) Allopatric speciation (d) None of the above

Explanation / Answer

Answer

(b) Reproducing this year versus survival and/or reproduction in future years.

Explanation:

Lack (1948) proposed that optimal reproduction is what in which most offspring survives. Thus, the optimum of intermediate reproduction is known as Lack’s clutch size.

Lack’s clutch size is based on a physiological selection with constant relative finesses, with a trade-off between survival (p) and lifetime reproduction (R)

p = p*L e1 – R/R*L

where p*L is the probability to survive and reproduce, and R*L lifetime reproduction, at Lack’s optimum (*L). With fitness being r = ln (p R), we obtain the fitness profile.

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