Conference Paper
Hybridization and the colonisation of the cave environment by fish
Cahill, A., Yurgel, M. and Espinasa, L.
Record Number:
3199
Year:
2013
Journal:
AIM 2013
Abstract:
Populations of cave Astyanax have two main types of mitochondrial DNA whose
differences are of such magnitude as to be derived from separate species. The commonly
accepted view is that an old stock colonized the cave environment and a younger stock is
currently found in the surface populations and in some of the cave populations.
Hybridization has occurred between both stocks at multiple cave localities. It is often
assumed that gene flow from this hybridization reduces the level of troglomorphy in cave
population of Astyanax but, are there cases in which the hybridization of two surface
species actually promoted the evolution of troglomorphy in cave fish?
In the case of two populations of the Pennsylvania Grotto Sculpin, the northernmost
cave adapted fish in the world, hybrid populations did show an increase in
troglomorphic development. One of these populations, the Nippenose cave fish, has a
suite of modifications that readily identify them as cave-adapted: Smaller eyes, elongated
pectoral fins, more numerous and enlarged cephalic lateralis pores, and a broader
head/mouth. On the contrary, the population of Tytoona cave fish do not have the
aforementioned suite, with the exception of slightly enlarged cephalic pores.
When
looking at mitochondrial markers, the Tytoona cave population has a single haplotype,
identical to C. bairdi from surrounding surface streams. Interestingly, the more
troglomorphic Nippenose cave population shares mitochondrial haplotypes with two
species of sculpin —Cottus cognatus and C. bairdi. Molecular data as well as
morphology support that in the Nippenose grotto sculpin, a hybridization event of C.
cognatus and C. bairdi generated an adaptationally distinct sculpin lineage, while in those
localities where a single species colonizes the cave, gene flow may have prevented it.
The case of the Pennsylvania Grotto Sculpin raises questions about our
understanding of hybridization in Astyanax. It has become a paradigm that Astyanax cave
forms were established by an ancestral surface-dwelling form that is either extinct, or no
longer present in this region of Mexico. This may be incorrect since surface populations
with mitochondrial haplotypes related to both old and young stocks are current
inhabitants of the surrounding areas of Sierra de El Abra: Rascon, and Tamasopo for the
old stock and Tampaon and Boquillas for the young stock. While questionable, it may be
worth considering that in the evolution of cave Astyanax, a hybridization event could
have been implicated in the successful colonization of the cave environment in light of
the fact that in other cave-adapted fish, hybridization appears to have been important.
Times Cited:
1
Relevent Species:
Related Records:
Stone, R.W. (1953)
Caves of Pennsylvania
Robins, C.R. (1954)A taxonomic revision of the Cottus bairdi and Cottus carolinae species group in eastern North American (Pisces, Cottidae)
Williams, J. D. and Howell, W. M. (1979)An albino sculpin from a cave in the New River drainage of West Virginia (Pisces: Cottidae)
Troester, J.W. and White, W.B. (1984)Seasonal fluctuations in the carbon dioxide partial pressure in a cave atmosphere
Strauss, R.E. (1986)Natural hybrids of the freshwater sculpins Cottus bairdi and Cottus cognatus (Pisces: Cottidae): Electrophoretic and morphometric evidence
Jones, W.R. and Jannsen, J. (1992)Lateral line development and feeding behaviour in the mottled sculpin, Cottus bairdi (Scorpaeniformes, Cottidae)
Coombs, S. (1999)Signal detection theory, lateral‐line excitation patterns and prey capture behaviour of mottled sculpin
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Robins, C.R. (2005)Cottus kanawhae, a new cottid fish from the New River System of Virginia and West Virginia
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Espinasa, L., Cahill, A., McCaffery, S. and Millar, C. (2013)Partial sequence of a gene involved in skin colouration (MC1R) from the Pennsylvanian Grotto Sculpin
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McCaffery, S., Collins, E. and Espinasa, L. (2014)Eye histology of the Tytoona Cave Sculpin: Eye loss evolves slower than enhancement of mandibular pores in cavefish?
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Espinasa, L., Smith, D.M. and Lindquist, J.M. (2021)The Pennsylvania grotto sculpin: population genetics