Population genetics of incipient speciation in two species of jumping spiders (Salticidae: Habronattus) on the sky islands of southeast Arizona

Persistent Link:
http://hdl.handle.net/10150/284016
Title:
Population genetics of incipient speciation in two species of jumping spiders (Salticidae: Habronattus) on the sky islands of southeast Arizona
Author:
Masta, Susan Elaine
Issue Date:
1999
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
The population genetic forces that promote speciation, although well understood theoretically, are poorly known in nature. This dissertation focuses on the population genetics of allopatric speciation, using a system of jumping spiders (Araneae: Salticidae) whose populations are subdivided among the disjunct patches of mountain woodland habitat called "sky islands" in southeastern Arizona. I studied two species of salticids that apparently share similar histories of range fragmentation but differ greatly in their amount of intraspecific phenotypic divergence. Using sequence data from neutrally evolving mitochondrial genes, I investigated the population genetic factors influencing divergence. Analyses of gene trees for Habronattus oregonensis and H. pugillis revealed that neither gene flow, effective population size, mutation rate, nor differences in divergence time can explain the interspecific difference in phenotypic divergence. Instead, selection--in these animals, presumably sexual selection--must have acted differentially on traits encoded by nuclear loci to produce the discrepancy. A phylogeographic study of populations of H. pugillis may help clarify the influence of post-Pleistocene vegetational change on organisms dependent upon montane woodlands. Gene trees suggest limited migration between mountain ranges, but offer stronger evidence for incomplete lineage sorting. The trees provide no clear indication of the chronological sequence of woodland fragmentation, but suggest an old geographic division between northern and southern populations. Dates estimated for population divergence range from 26,000 to 291,000 years ago, but rely on molecular clock estimates from non-arachnid arthropods. Divergence estimates based on vegetation change data would require that the mutation rate be considerably faster in these spiders than in non-arachnid arthropods. Whereas there is no fossil-based molecular clock calibration for arachnids to judge whether this is likely, analyses of mitochondrial sequences from three Habronattus species do reveal other highly unusual features. For example, secondary structures that were inferred from DNA sequences of tRNA genes lack the TPsiC arm, and therefore are predicted not to form the standard tRNA cloverleaf. In addition, the 3' half of the gene encoding ribosomal 16S RNA appears to fold to a normal arthropod-like secondary structure, but the 5' half is extremely divergent and truncated with respect to other arthropods.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Biology, General.; Biology, Ecology.; Biology, Genetics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Ecology and Evolutionary Biology
Degree Grantor:
University of Arizona
Advisor:
Maddison, Wayne P.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titlePopulation genetics of incipient speciation in two species of jumping spiders (Salticidae: Habronattus) on the sky islands of southeast Arizonaen_US
dc.creatorMasta, Susan Elaineen_US
dc.contributor.authorMasta, Susan Elaineen_US
dc.date.issued1999en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThe population genetic forces that promote speciation, although well understood theoretically, are poorly known in nature. This dissertation focuses on the population genetics of allopatric speciation, using a system of jumping spiders (Araneae: Salticidae) whose populations are subdivided among the disjunct patches of mountain woodland habitat called "sky islands" in southeastern Arizona. I studied two species of salticids that apparently share similar histories of range fragmentation but differ greatly in their amount of intraspecific phenotypic divergence. Using sequence data from neutrally evolving mitochondrial genes, I investigated the population genetic factors influencing divergence. Analyses of gene trees for Habronattus oregonensis and H. pugillis revealed that neither gene flow, effective population size, mutation rate, nor differences in divergence time can explain the interspecific difference in phenotypic divergence. Instead, selection--in these animals, presumably sexual selection--must have acted differentially on traits encoded by nuclear loci to produce the discrepancy. A phylogeographic study of populations of H. pugillis may help clarify the influence of post-Pleistocene vegetational change on organisms dependent upon montane woodlands. Gene trees suggest limited migration between mountain ranges, but offer stronger evidence for incomplete lineage sorting. The trees provide no clear indication of the chronological sequence of woodland fragmentation, but suggest an old geographic division between northern and southern populations. Dates estimated for population divergence range from 26,000 to 291,000 years ago, but rely on molecular clock estimates from non-arachnid arthropods. Divergence estimates based on vegetation change data would require that the mutation rate be considerably faster in these spiders than in non-arachnid arthropods. Whereas there is no fossil-based molecular clock calibration for arachnids to judge whether this is likely, analyses of mitochondrial sequences from three Habronattus species do reveal other highly unusual features. For example, secondary structures that were inferred from DNA sequences of tRNA genes lack the TPsiC arm, and therefore are predicted not to form the standard tRNA cloverleaf. In addition, the 3' half of the gene encoding ribosomal 16S RNA appears to fold to a normal arthropod-like secondary structure, but the 5' half is extremely divergent and truncated with respect to other arthropods.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectBiology, General.en_US
dc.subjectBiology, Ecology.en_US
dc.subjectBiology, Genetics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineEcology and Evolutionary Biologyen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMaddison, Wayne P.en_US
dc.identifier.proquest9927470en_US
dc.identifier.bibrecord.b39560284en_US
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