Insect micro- and macroevolution through space and time

This dissertation uses computational molecular phylogenetic methods to study macro-and micro-evolutionary processes that give rise to biodiversity. Insects, the most diverse group of organisms on earth, are an excellent group for studying and testing various evolutionary hypothesis. I used molecular phylogenetic methods to study the population structure of the northern most Arctic dragonfly species Somatochlora sahlbergi. Our results show that this species doesn’t follow a common trend seen in evolutionary biology that is, large geographic distances and geographic barriers lead to increased genetic variation. Not only does S. sahlbergi appears to interbreed across its entire Holarctic range, there also seems to be almost no variation among European and North American populations in their COI gene fragment (the barcode gene), which is usually extremely variable. These findings seem to be unique to this particular species as none other Arctic dragonflies show such genetic patterns. Upon examining four other distantly related dragonfly species, Aeshan juncea, Aeshna subarctica, Sympetrum danae and Libellula quadrimaculata, that have similar Holacrtic distribution as S. sahlbergi, we find that these species indeed show a geographic structure across their range unlike S. sahlbergi. We find that North American and European populations show clear genetic distinction, and this split occurred ~ 400,000 ago, during the Quaternary Period. Lastly, I use the popular divergence time estimation methodology to study the evolutionary past of the Insects and explore how our use of fossil record can influence the outcome of such methods. The results show that fossils can be extremely influential depending on the age of the node (i.e. origin to two lineages). Deep nodes, that represent very old relationships in the evolutionary history, tend to be heavily impacted by the fossil calibrations compared to younger nodes. Older nodes suffer more in their age estimates and the precision around these age estimates in the absence of a fossil. Further, we find that certain groups of insects like flies and butterflies evolve at a much faster rate than most of the other groups of insects.Ph.D.Includes bibliographical reference