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J T Streelman

Publications and source records attributed to J T Streelman.

8 recordsLinked to original sources
PubMed2002

Rapid isolation of CA microsatellites from the tilapia genome.

We have developed (CA)n microsatellite markers for the cichlid fish, Oreochromis niloticus using a variation of the hybrid capture method. The resulting genomic library was highly enriched in repetitive DNA with 96% of clones containing CA repeats. The number of repeats ranged from four to 45 with an average of 19. Two-thirds of the sequenced clones had 12 or more repeats and sufficient flanking sequence to design primers. The resulting markers were tested in an F2 cross of O. niloticus x O. aureus. Nearly 90% of the markers amplified in this cross and 74% of these were informative. This work demonstrates the importance of minimizing the number of polymerase chain reaction (PCR) amplification cycles before and after the enrichment steps to reduce PCR recombination and the generation of chimaeric clones.

Animals↗
PubMed2002

Evolutionary history of the parrotfishes: biogeography, ecomorphology, and comparative diversity.

The family Scaridae comprises about 90 species of herbivorous coral reef, rock reef, and seagrass fishes. Parrotfishes are important agents of marine bioerosion who rework the substrate with their beaklike oral jaws. Many scarid populations are characterized by complex social systems including highly differentiated sexual stages, territoriality, and the defense of harems. Here, we test a hypothesis of relationships among parrotfish genera derived from nearly 2 kb of nuclear and mitochondrial DNA sequence. The DNA tree is different than a phylogeny based on comparative morphology and leads to important reinterpretations of scarid evolution. The molecular data suggest a split among seagrass and coral reef associated genera with nearly 80% of all species in the coral reef clade. Our phylogenetic results imply an East Tethyan origin of the family and the recurrent evolution of excavating and scraping feeding modes. It is likely that ecomorphological differences played a significant role in the initial divergence of major scarid lineages, but that variation in color and breeding behavior has triggered subsequent diversification. We present a two-phase model of parrotfish evolution to explain patterns of comparative diversity. Finally, we discuss the application of this model to other adaptively radiating clades.

Animals↗
PubMed2002

Microsatellite variation associated with prolactin expression and growth of salt-challenged tilapia.

Biologists have long argued that runs of alternating purines and pyrimidines could form alternative DNA structures, which might regulate transcription. Here, we report that simple sequence repeat polymorphisms in the tilapia prolactin 1 (prl 1) promoter are associated with differences in prl 1 gene expression and the growth response of salt-challenged fishes. Individuals homozygous for long microsatellite alleles express less prl 1 in fresh water but more prl 1 in half-seawater than fishes with other genotypes. Our work provides the first in vivo evidence that differences in microsatellite length among individuals may indeed affect gene expression and that variance in expression has concomitant physiological consequences. These results suggest that dinucleotide microsatellites represent an under-appreciated source of genetic variation for regulatory evolution.

Animals↗
PubMed1998

Multilocus phylogeny of cichlid fishes (Pisces: Perciformes): evolutionary comparison of microsatellite and single-copy nuclear loci.

Among vertebrates, cichlid fishes are the paradigmatic example of adaptive radiation and ecological specialization. In turn, molecular genetic studies of cichlids have focused primarily on more recently diverged groups. Here, we present an evolutionary hypothesis of the major lineages of cichlid fishes based on DNA sequence data from two nuclear loci. One marker, Tmo-4C4, is a single-copy locus containing a region of amino acid similarity to the muscle protein TITIN. Flanking sequence from a second, microsatellite, locus Tmo-M27, shows similarity to mammalian RAS guanine nucleotide-releasing factor. We compare and combine data from these loci to evaluate phylogenetic performance. In separate and combined analyses, the sequence data support and clarify previous morphological hypotheses of cichlid major-group relationships. Indian and Malagasy cichlids form a basal, paraphyletic group. Neotropical cichlids are the sister clade to an African assemblage composed of the paraphyletic west and Pan-African lineages and a group of east African rift lake taxa. We use a consensus phylogeny of the Cichlidae to trace evolutionary changes in the microsatellite repeat motif at Tmo-M27. Analysis reveals that the repeat region was nearly lost in the ancestor to cichlids and then amplified extensively in African taxa. Results demonstrate that the two new DNA markers could be widely applied in perciform systematics. Furthermore, the comparative approach can unveil mutational dynamics of simple-sequence repeat loci over long periods of fish evolution. Simple-sequence repeat regions are increasingly being found in introns of important regulatory genes. We address issues involving their function and suggest caution in making assumptions of strict neutrality.

Animals↗
PubMed1997

Reconstructing labroid evolution with single-copy nuclear DNA.

Fifteen per cent of all living fishes are united in a single suborder (Labroidei) and display a dazzling array of behavioural and ecological traits. The labroids are considered monophyletic and members share a pharyngeal jaw apparatus (PJA) modified for crushing and processing prey. Outside of the explicitly functional PJA, there is no corroborative evidence for a monophyletic Labroidei. Here, we report the first molecular phylogenetic analysis of the suborder. Contrary to morphology-based phylogenies, our single-copy nuclear DNA data do not support labroid families as a natural group. Our data indicate that pharyngognathy has evolved independently among labroid families and that characters of the PJA are not reliable markers of perciform evolution. This work 'crushes' conventional views of fish phylogeny and should engender novel concepts of piscine life history evolution.

Animals↗
PubMed1996

Evolutionary conservation of microsatellite flanking regions and their use in resolving the phylogeny of cichlid fishes (Pisces: Perciformes).

A phylogeny of the principal lineages of cichlid fishes and two other fish families of the suborder Labroidei was based on phylogenetic information from DNA sequences of the flanking region of a (CA)n microsatellite locus. Microsatellite (CA)n containing clones from a genomic library of an African cichlid fish from Lake Tanganyika, Tropheus moorii, were sequenced and primers for the polymerase chain reaction designed. All primers amplified the homologous microsatellite loci in many more than the source species and one microsatellite flanking locus (TmoM27) was particularly conserved and amplified in several lineages of perciform fishes that diverged more than 80-100 million years ago. Despite the extensive level of evolutionary conservation of this microsatellite flanking region (MFR), this nuclear region contained reliable phylogenetic information in the form of both point and length mutations. A phylogeny of cichlids based on this MFR agrees with other phylogenetic hypotheses based on morphological, mitochondrial, and anonymous nuclear DNA. Madagascan and Indian cichlids are found to be paraphyletic and the most basal group in the family Cichlidae. African and Neotropical cichlids are both monophyletic and sistergroups. Within African lineages, the East African cichlids are most likely to be monophyletic and the West African cichlids are probably paraphyletic and basal to all African species. The focal microsatellite locus contained much variation in (CA)n repeats in African cichlids and in surfperches (up to 64 repeats), but was short (with only 2-4 repeats) and almost invariant in Neotropical cichlids. The design of phylogenetically highly versatile MFR-primers will be of use not only for phylogeny reconstruction among families of perciform fishes, but also for population-level work in the thousands of species belonging to this highly species-rich suborder of fishes.

Animals↗
PubMedDate not supplied

From phenotype to genotype.

Advances in the field of genomics have made it possible to decipher the genetic and transcriptional changes that underlie differences among organisms. Here we discuss the merits and drawbacks of these strategies as they relate to evolutionary biology. We suggest that the molecular basis of natural variation can best be interpreted via the intersection of genomic and transcriptome approaches. We outline how this might be accomplished in practice and assemble the components of a method to comprehend the evolutionary interplay between genotype and phenotype.

Biological Evolution↗