Data from: Species collapse via hybridization in Darwin's tree finches

Species hybridization can lead to fitness costs, species collapse, and
novel evolutionary trajectories in changing environments. Hybridization is
predicted to be more common when environmental conditions change rapidly.
Here, we test patterns of hybridization in three sympatric tree finch
species (small tree finch Camarhynchus parvulus, medium tree finch
Camarhynchus pauper, and large tree finch: Camarhynchus psittacula) that
are currently recognized on Floreana Island, Galápagos Archipelago.
Genetic analysis of microsatellite data from contemporary samples showed
two genetic populations and one hybrid cluster in both 2005 and 2010;
hybrid individuals were derived from genetic population 1 (small morph)
and genetic population 2 (large morph). Females of the large and rare
species were more likely to pair with males of the small common species.
Finch populations differed in morphology in 1852–1906 compared with
2005/2010. An unsupervised clustering method showed (a) support for three
morphological clusters in the historical tree finch sample (1852–1906),
which is consistent with current species recognition; (b) support for two
or three morphological clusters in 2005 with some (19%) hybridization; and
(c) support for just two morphological clusters in 2010 with frequent
(41%) hybridization. We discuss these findings in relation to species
demarcations of Camarhynchus tree finches on Floreana Island.