Polyphyly, hybridization, and cryptic biodiversity among Micropterus (Teleostei: Centrarchidae)

Authors: Justin C. Bagley, Richard L. Mayden, Kevin J. Roe, Wallace Holznagel, Phillip M. Harris

Year: 2008 (xl)

Abstract

Phylogenetic relationships and mtDNA variation among Micropterus were examined using complete sequences of the mitochondrial cytochrome b gene for 174 individuals from seven species, three subspecies, and an undescribed putative species. We tested (i) whether nominal species formed natural groups, (ii) whether intra- and interspecific relationships within Micropterus could be estimated with greater confidence with increased within-taxon sampling compared to results from increased character sampling regimes (i.e., Near et al., 2004, 2005), and (iii) for existence of new, potentially cryptic biodiversity within Micropterus. Eight major clades were obtained from maximum parsimony and maximum likelihood analyses: (1) M. dolomieu, M. p. punctulatus, and M. treculi; (2) M. coosae (‘Bartram’s bass’) nested within a clade of M. cataractae; (3) M. coosae and M. p. henshalli; (4) M. notius; (5) M. sp. cf. punctulatus, eastern Gulf Coastal Plain (GCP) rivers; (6) M. punctulatus, GCP rivers just west of the Mississippi River + M. treculi; (7) M. salmoides; and (8) M. floridanus nested within M. salmoides. M. coosae, M. floridanus, M. p. henshalli, M. p. punctulatus, and M. treculi were recovered as poly-/paraphyletic. We found evidence for eight putative hybridization/introgression events: M. dolomieu Á— M. p. punctulatus, M. p. punctulatus Á— M. p. henshalli, M. p. henshalli Á— M. coosae, M. cataractae Á— M. coosae, M. punctulatus Á— M. treculi, M. salmoides Á— M. coosae, M. salmoides Á— M. punctulatus, and M. salmoides Á— M. floridanus. M. floridanus, a former subspecies of M. salmoides, and M. dolomieu velox were recovered nested within monophyletic groups of conspecifics and exhibited low (1-2%) sequence divergence suggesting they are not distinct at cyt b based on increased within-taxon sampling. In combination with recent data on M. punctulatus morphology, our results support cryptic biodiversity within this species in GCP rivers just east of the Mississippi River, where populations appear more closely related to M. treculi than other M. punctulatus.