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LECTURE 17: LINEAGE SPLITTING (SPECIATION)
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New
Guinea Kinfishers (Tanysiptera spp.)
The "species complex" that goes by the name Tanysiptera hydrocharis
lives on New Guinea and surrounding islands. There are three recognized
"suspecies" (groups of populations) that occur in distinct areas of the
main island (1,2 and 3 in figure); these are morphologically slightly different,
but there are no apparent isolating mechanisms separating these groups.
On the islands, populations have diverged substantially in morphology from
each other and from the mainland populations (4-8, H1 in figure; the area
occupied by H2 was formerly a separate island) . This pattern is
exactly what is expected if the water separating the islands from the mainland
acts as a physical barrier to migration. Moreover, one of these island
populations (H2) established secondary contact with a mainland population
(3) when falling sea levels led to a connection its island to the
mainland. These two groups of populations do not interbreed, indicating
that divergence in allopatry led to the evolution of premating isolation.
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