Molecular phylogeny and population biology of the senita cactus (Lophocereus schottii) and its obligate mutualistic moth pollinator (Upiga virescens).

摘要

Work described in this study focuses on the phylogeny and population biology of the recently discovered obligate pollination mutualism between the senita cactus (Lophocereus) and its moth pollinator ( Upiga virescens).; I first determined the relationships among Lophocereus taxa (L. schottii schottii, L. s. australis, L. s. tenuis, L. gatesii ) and established the phylogenetic position of Lophocereus within the North American columnar cacti. Screening over 20 kb of intergenic organellar regions of the senita cactus, I found no polymorphisms within this genus and concluded that senita taxa are conspecific. I determined that Lophocereus is sister to the hummingbird pollinated Pachycereus marginatus and discussed implications for the evolution of moth pollination.; I next wanted to determine the genetic population structure of the senita cactus and its moth pollinator, and to test for co-speciation of these interacting taxa (parallel cladogenesis). I first evaluated rDNA sequences for their use as a phylogeographic marker. Results showed that senita has two distinct rDNA operons, one that is functional and one that is a pseudogene. Remarkably, I found high levels of coding region heterogeneity both within and between operons. I determined the evolutionary origin of the pseudogene and concluded that the duplication of operons occurred in the common ancestor of Lophocereus and Pachycereus marginatus.; The second nuclear sequence I used for phylogeographic analysis of the senita cactus was the first intron in the conserved coding region of the triose phosphate isomerase gene. My population analyses showed that the senita cactus was recently established from Pleistocene refugia in the south. Phylogenetic analyses demonstrated that different taxa within the genus are not evolutionarily independent lineages. This is in agreement with organellar sequence analyes and suggests conspecificity of these senita taxa.; Using mitochondrial sequences to determine the population structure of the senita moth, I concluded that the Gulf of California is not a barrier to gene flow, and that moths found on the different senita taxa do not form monophyletic lineages. Finally, my combined results for the senita cactus and its moth pollinator do not provide evidence for co-speciation or parallel cladogenesis of the senita cactus and its moth pollinator.