Character Displacement Through an Evolutionary Change in Ontogenetic Niche Shifts
Abstract
In communities structured by body size, coexistence can occur through
combinations of ontogenetic changes in competitive ability and dietary
niche. Using stable isotopes, we examined ontogenetic niche shifts in
Trinidadian guppies (Poecilia reticulata) and killifish (Rivulus hartii)
in three types of natural communities (both species with predators, KGP;
both without predators, KG; killifish only, KO) and four experimental KG
communities, initiated with KGP guppies and KO killifish between 13 and
45 years ago. In all communities, killifish occupied higher trophic
positions and changed their diet (δ^13 C) with body size. Only KGP
guppies displayed an ontogenetic niche shift. The KG guppies displayed a
significant difference in trophic niche from KGP guppies, a character
displacement that can facilitate coexistence with killifish. In the
experimental communities, the guppy trophic niche was intermediate
between those in KGP and KG communities, indicating that evolution has
driven the niche shift in KG guppies.