Multi‐trait evolution in a cave fish,<i>Astyanax mexicanus</i>

Protas, Meredith E.; Tabansky, Inna; Conrad, Melissa D.; Gross, Joshua B.; Vidal, Oriol; Tabin, Clifford J.; Borowsky, Richard

doi:10.1111/j.1525-142x.2008.00227.x

Cited by 175 publications

(260 citation statements)

References 48 publications

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“…In this regard, multiple causes of eye degeneration are consistent with the recent discovery of as many as 12 quantitative trait loci, and thus genes, governing eye loss in cavefish (Protas et al, 2008). This opens the possibility that several different evolutionary forces could synergistically drive eye regression.…”

supporting

confidence: 52%

“…In the past, three theories have been proposed to explain the loss of eyes in cave organisms: (1) neutral mutation and genetic drift, (2) positive selection against eyes due to energy conservation or their possible liability and (3) indirect selection against eyes based on increase in beneficial traits that are negatively linked to optic development by pleiotropy. The first idea was favored until about the turn of this century (Culver and Wilkens, 2000), but since then new genetic and developmental evidence has tipped the scale toward the third idea-pleiotropy (Jeffery, 2005;Protas et al, 2008). In this review, Wilkens (2010) re-evaluates the genetic and developmental data and concludes that there is no validity for the second or third (selectionist) theories, reverting to neutral mutation as the most plausible explanation for eye degeneration.…”

mentioning

confidence: 99%

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Pleiotropy and eye degeneration in cavefish

Jeffery

2010

Heredity

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supporting

confidence: 52%

mentioning

confidence: 99%

Pleiotropy and eye degeneration in cavefish

Jeffery

2010

Heredity

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“…This would be expected given the extensive genomic rearrangements that have occurred among even closely related species over the course of genomic evolution. Nonetheless, for several linkage groups (Astyanax LGI 8,11,14,18,21,23,24), we found that every syntenic hit resides on a single Danio chromosome (Danio chromosomes 1, 18, 2, 10, 1, 17, 7, respectively).…”

Section: Resultsmentioning

confidence: 99%

“…1, LGI 10). Many of these genomic markers span the critical region(s) of QTL identified in our phenotypic analyses (14). Thus, the addition of genes to the linkage map can be used directly to seek associations between a gene of interest and a particular trait.…”

Section: Gene Position In Astyanax Is Reliably Predicted By Homologoumentioning

confidence: 99%

“…This linkage map, based on recombination frequencies of hundreds of microsatellite and candidate gene markers, has helped illuminate key aspects of Astyanax biology (13,14). The first trait identified using quantitative trait locus (QTL) analyses in Astyanax was the genetic basis of albinism, shown to be a consequence of independent genetic lesions affecting the gene ocular and cutaneous albinism type II (Oca2) in two different cave populations (12).…”

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Synteny and candidate gene prediction using an anchored linkage map of Astyanax mexicanus

Gross

Protas

Conrad

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

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The blind Mexican cave tetra, Astyanax mexicanus, is a unique model system for the study of parallelism and the evolution of cave-adapted traits. Understanding the genetic basis for these traits has recently become feasible thanks to production of a genome-wide linkage map and quantitative trait association analyses. The selection of suitable candidate genes controlling quantitative traits remains challenging, however, in the absence of a physical genome. Here, we describe the integration of multiple linkage maps generated in four separate crosses between surface, cave, and hybrid forms of A. mexicanus. We performed exhaustive BLAST analyses of genomic markers populating this integrated map against sequenced genomes of numerous taxa, ranging from yeast to amniotes. We found the largest number of identified sequences (228), with the most expect (E) values <10 ؊5 (95), in the zebrafish Danio rerio. The most significant hits were assembled into an ''anchored'' linkage map with Danio, revealing numerous regions of conserved synteny, many of which are shared across critical regions of identified quantitative trait loci (QTL). Using this anchored map, we predicted the positions of 21 test genes on the integrated linkage map and verified that 18 of these are found in locations homologous to their chromosomal positions in D. rerio. The anchored map allowed the identification of four candidate genes for QTL relating to rib number and eye size. The map we have generated will greatly accelerate the production of viable lists of additional candidate genes involved in the development and evolution of cave-specific traits in A. mexicanus.sequence homology ͉ physical genome ͉ evolution ͉ quantitative trait locus

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Cave Evolution

Gross

2012

Encyclopedia of Life Sciences

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Cave‐dwelling animals are fascinating because of the phenotypic extremes they frequently exhibit, such as a reduced or complete loss of vision and pigmentation. Equally interesting is the fact that irrespective of taxonomic position, organisms colonising the subterranean environment converge on highly similar phenotypic deficits and improvements. Thus, a predictable suite of morphological, physiological and behavioural changes evolve in response to low nutrient conditions of the subterranean environment. Despite several decades of enquiry, the precise genetic and molecular underpinnings of cave‐associated changes are only beginning to be elucidated through the use of high‐resolution contemporary molecular and genetic techniques. Regressive phenotypic changes, those traits that are lost in derived lineages, are particularly interesting since they evolve in the absence of obvious selective value to the organism. Continuing research utilising an increasing number of emerging cave‐dwelling models offers the exciting prospect of clarifying longstanding problems in contemporary evolutionary biology. Key Concepts: Widespread convergence on cave‐associated (troglomorphic) characteristics is often attributed to the paucity of nutrition and overall stability of the cave environment. Cave‐adapted organisms are excellent models for the study of regressive phenotypic evolution, that is the loss of traits in derived organisms. The evolutionary mechanism(s) accounting for phenotypic loss in cave‐dwelling organisms (neutralism versus selection) remains unknown. Hybrid crosses between cave‐dwelling and intra‐specific ‘surface’ forms reveal numerous morphological changes associated with cave adaptation are recessive. Phenotypic analyses in subsequent generations reveal many cave‐associated characteristics arise through Mendelian (single locus) and complex (polygenic) patterns of inheritance. The cave environment likely represents an attractive habitat given that over 50 000 cave‐limited species are known worldwide, distributed across broad taxonomic groups. Contemporary cave research has advanced significantly over the last decade thanks to integrative analyses combining developmental, genetic, genomic, behavioural, physiological and population‐level approaches.

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Multi‐trait evolution in a cave fish,Astyanax mexicanus

Cited by 175 publications

References 48 publications

Pleiotropy and eye degeneration in cavefish

Pleiotropy and eye degeneration in cavefish

Synteny and candidate gene prediction using an anchored linkage map of Astyanax mexicanus

Cave Evolution

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