Conference Paper
A year in the life of two populations of Astyanax mexicanus.
Bonaroti, N., Rutkowski, J., Rétaux, S., Collins, E., Ornelas García, P., Heintz, C. and Espinasa, L.
Record Number:
3267
Year:
2017
Journal:
AIM 2017
Abstract:
Has evolution actually been observed as it happens by anyone? The answer is yes. One
famous example is the Darwin finches. The Grants spent twenty years in the Galapagos to show
that after a severe drought, the struggle to survive favored larger birds with strong beaks for
opening hard seeds.
However, has anyone seen evolution occur in nature, in a charismatic vertebrate, in the
cave environment? While most DNA and EvoDevo studies support evolution, these studies have
analyzed ex post facto events of evolution. Their data is typically based on characters that resulted
from evolution, after it has taken place. The purpose of this research was to follow a population of
cavefish where change in heritable traits are tracked over real physical time.
Río Subterráneo Cave contains a wide array of intermediate, hybrid phenotypes living
alongside surface fish. This is due to seasonal migration of surface fish into the cave after flooding
and subsequent introgression in the existing cave population. The population was tracked
throughout an entire year, with field trips every two months. Condition factor, as an estimate of
fish health, and environmental conditions such as carbon content of the debris were tracked. As
the dry season progressed, food is limiting and characters that give an advantage for survival were
selected for. At the end of a year-long study, it is expected that we will be able to document
selection in situ through demographic analyses of the variations in phenotypes (troglomorphic or
non troglomorphic) along the year and according to seasonal environmental variations in a
population of Astyanax.
A similar year-long study from Pachón cave showed that fry are efficient predators of
aquatic micro-crustaceans. Food regimes change between post-larval and adult stages to become
more dependent on partially decomposed material and guano. Surprisingly, the environment
appears to be less “food poor” for juvenile cavefish during the dry season than in the rainy season.
Times Cited:
1
Relevent Species: