Mechanisms of speciation and coexistence in corydoradinae catfishes

Abstract

Nothing in evolutionary ecology makes sense except in the light of comparative
multidisciplinary evidence. In light of this view, I employed a variety of techniques to study the mechanisms of speciation and coexistence in Corydoradinae catfishes.
Specifically I used a combination of molecular phylogenetics (using mitochondrial
and nuclear markers), stable isotope analyses (of carbon and nitrogen), geometric
morphometrics, colour pattern analyses, and quantification of total nuclear DNA
content. These data have been combined and analyzed using comparative frameworks in order to address the following hypotheses: (a) that positive interactions among mimetic species outweigh the negative effects of competition for resources; (b) that genome duplications drive diversification; (c) a number of available hypothesis that account for Corydoradinae patterns of historical biogeography. I establish the first comprehensive molecular phylogenetic framework for the Corydoradinae supporting the existence of nine well supported lineages. I show that in at least 24 sympatric assemblages, Corydoradinae catfishes form Müllerian mimicry rings composed of ecologically, morphologically and phylogenetically differentiated species. Genome size estimation and phylogenetic analysis revealed that polyploid lineages are derived
in comparison to diploid lineages, and that polyploids are significantly more species rich than diploids. Furthermore, biogeographic analyses show that the majority of cladogenesis occurred within basins and not as a result of paleobasin vicariance.
These results support the following conclusions: (a) that negative interactions, such as competition for resources, and phylogeny determine community structure among mimetic species thereby outweighing the effects of positive interactions such as mimicry; (b) that ancestral genome duplication within the Corydoradinae accelerates diversification rates; (c) Taxon Pulses, Paleogeography and Hydrology, and Phylogenetic Niche Conservatism account for spatiotemporal patterns of distribution. Moreover, I discuss a number of different mechanisms of speciation (colour pattern convergence, morphological divergence, genome duplication and allopatric speciation) and coexistence (resource partitioning, mutual defence through shoaling and colour pattern convergence in sympatry) relating to the Corydoradinae. All results are discussed in the context of evolutionary ecology at different temporal and spatial scales, in order to shed more light on the complex history of these fascinating catfishes.

Date of Award	Mar 2011
Original language	English
Awarding Institution	Bangor University
Sponsors	Natural Environment Research Council (NERC)
Supervisor	Martin Taylor (Supervisor)