Question

In the phylogeny above, Mendelson and Shaw reconstructed the historical patterns of relatedness among 25 species of Hawaiian cricket. They noted that often the closest relative of a species was another species that lived on the same island. They interpreted this as evidence that ___________________________.

1) new species formed primarily when crickets migrated from one island to another
2) crickets from the same island had adapted to different ecological habitats on each island
3) many of the cricket "species" were not actually true species

Answer 1

The closest relative of a Hawaiian cricket species typically being another species from the same island indicates that new species formed through habitat isolation within the same island, which is evidence of allopatric speciation and ecological adaptation, making option 2 the correct answer.

Step-by-step explanation:

In the context of the phylogeny of 25 species of Hawaiian cricket constructed by Mendelson and Shaw, the observation that the closest relative of a species was typically another species from the same island suggests that new species formed predominantly through allopatric speciation within the same island rather than by migration between islands.

The various examples presented, such as the crickets preferring different soil types (Gryllus pennsylvanicus on sandy soil and Gryllus firmus on loamy soil), the finches from the Galápagos and the Hawaiian silverswords, all support the theory that species can become genetically isolated and diverge into new species even when their habitats are in close proximity.

This habitat isolation leads to species divergence through natural selection pressures, mutation, and genetic drift, resulting in adaptations to specific ecological niches. Therefore, the correct interpretation is that crickets from the same island have adapted to different ecological habitats on each island, making option 2 the appropriate answer.