Expert: Florence M Rollwagen - 3/8/2009

Question
Hello,

I have been searching the internet and my text book and can't seem to come up with the correct answer to this question.

Which of the following has contributed the most towards the development of flora and fauna in the Hawaiian Islands (considered a great showcase of evolution)?

1.  hybrid vigor and allopatric speciation
2.  cross-specific mating and reinforcement
3.  allopolyploidy and sympatric speciation
4.  adaptive radiation and allopatric speciation

Thanks for any help you could offer.

Answer
Hi Debbi:  Thanks for your question.  What you need to do is determine the definitions of each pair of choices and decide if they apply to evolution on Hawaii.   You won't find the answer on the internet, that's why this is an AP question [grin]

Here's what I found out.

Definitions:

Choice 1:

Hybrid vigor:  Would apply when two strains mate and the offspring are more suited to the environment.  

Allopatric speciation:  The formation of species in different locations.  This would definitely apply to Hawaii because of the varied biomes present.

This pair could lead to new species, but in Hawaii, individuals came to the island, so mating with closely related species would not be possible.  It might apply in later generations, but I think your question is related to early evolution on the islands

Choice 2:

Cross-specific mating: Mating between two distinct species often results in sterile offspring, so would not be a mechanism for evolution.

Reinforcement:  The tendency for different species to stay separate and avoid cross-specific (sterile) mating.

This pair would not apply to speciation in any scenario

Choice 3:

Allopolyploidy:  The acquisition of extra chromosome sets from other species.  This can happen in protista, and some plants, but has not been demonstrated in higher animals.

Sympatric speciation:  The formation of new species in areas where there is species overlap.  In other words, not separated by some geography.

This pair could work for some species, but probably would not apply to the entire biome of Hawaii

Choice 4:

Adaptive radiation:  The rapid speciation from a single species in a new environment.

Allopatric speciation:  The formation of new species in different geographical locations.  

This pair is my choice for evolution on Hawaii.  They both apply to all animals and plants and the varied geography present on the islands.

Here’s a great book that discusses it all:

http://books.nap.edu/openbook.php?record_id=10865


Just for the record, I found your test online:
http://www.eeescience.utoledo.edu/Faculty/Dwyer/Syll/Biodiversity%20Exam%201.htm

Hope this helps.  Write back if you have more questions.

FM Rollwagen, PhD