Intraspecific relationships among the stygobitic shrimp Typhlatya mitchelli, by analyzing sequence data from mitochondrial DNA

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dc.contributor.advisor Iliffe , Thomas en_US
dc.contributor.committeeMember Wicksten , Mary en_US
dc.creator Webb , Michael Scott en_US 2004 -09 -30T01 :40 :14Z 2014 -02 -18T22 :28 :01Z 2004 -09 -30T01 :40 :14Z 2014 -02 -18T22 :28 :01Z 2003 -05 en_US 2004 -09 -30T01 :40 :14Z
dc.identifier.uri http : / /hdl .handle .net /1969 .1 /14
dc.description.abstract Intraspecific relationships among the anchialine cave shrimp Typhlatya mitchelli were examined by sequencing a total of 1505 bp from portions of three mitochondrial DNA genes . Cytochrome b , cytochrome oxidase I , and 16S rRNA were partially sequenced and analyzed for specimens from six different cenotes (water -filled caves ) across the Yucatan Peninsula , Mexico . The conspecific Typhlatya pearsei that is sympatric with T . mitchelli was also sequenced and used as the outgroup . Comparisons among specimens of T . mitchelli yielded low sequence divergence values (0 -1 .7 % ) , with the majority being less than 0 .4 % . Phylogenetic tree topologies reconstructed with neighbor -joining , maximum likelihood , and maximum parsimony were in agreement in regards of the resolution of deep branches . Also , there was no obvious geographic differentiation among the majority of T . mitchelli samples , with the exception of specimens from Cenote San Antonio Chiich (Yokdzonot , Yucatan , Mexico ) which all clustered into an extremely well supported monophyletic group . The level of differentiation of this group , together with the nearly total absence of differentiation among T . mitchelli from distant cave systems , suggests that this is an Evolutionary Significant Unit (ESU ) , which may correspond to a new species . This unidentified Typhlatya from Cenote San Antonio Chiich was helpful in establishing a period in which the epigean ancestor colonized the cenotes . Based on pairwise distance data and previously published shrimp molecular clocks (Baldwin et al . , 1998 ) , T . mitchelli and the putative new Typhlatya species last shared a common ancestor between 3 -5 million years ago (mya ) , during the mid -Pliocene era , while T . mitchelli and T . pearsei was approximately 7 -10 mya (middle to late Miocene ) . The ancestor to T . mitchelli and the unidentified Typhlatya species abandoned its shallow coastal water existence in the early Pliocene and eventually expanded its range across the peninsula . Approximately 4 mya , Cenote San Antonio Chiich became isolated from the remaining gene pool thereby halting gene flow . As the regional water table fluctuated in response to the rise and fall of Pleistocene sea levels , T . mitchelli actively colonized the peninsula . The discovery of a single , continuous subterranean freshwater system provides for a better understanding of anchialine biogeography within the Yucatan Peninsula . en_US
dc.format.extent 889891 bytes
dc.format.medium electronic en_US
dc.format.mimetype application /pdf
dc.language.iso en _US en_US
dc.publisher Texas A &M University en_US
dc.subject mitochondrial en_US
dc.title Intraspecific relationships among the stygobitic shrimp Typhlatya mitchelli , by analyzing sequence data from mitochondrial DNA en_US
dc.type Book en
dc.type.genre Electronic Thesis en_US
dc.type.material text en_US
dc.format.digitalOrigin born digital en_US


Intraspecific relationships among the stygobitic shrimp Typhlatya mitchelli, by analyzing sequence data from mitochondrial DNA. Available electronically from http : / /hdl .handle .net /1969 .1 /14 .

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