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Title:Biogeography and phylogenetics of grassland auchenorrhyncha
Author(s):Catanach, Therese
Director of Research:Dietrich, Christopher H.
Doctoral Committee Chair(s):Dietrich, Christopher H.
Doctoral Committee Member(s):Johnson, Kevin P.; Punyasena, Surangi W.; Suarez, Andrew V.; Whitfield, James B.
Department / Program:School of Integrative Biology
Discipline:Ecol, Evol, Conservation Biol
Degree Granting Institution:University of Illinois at Urbana-Champaign
divergence time estimation
Abstract:Grasslands cover a significant portion of the Earth’s terrestrial surface, yet we know little about the historical biogeography of grassland-restricted lineages. Previous work on the biogeography of grassland taxa has largely focused on large mammals. While these studies have generated some general patterns for the origin and dispersal of grassland animals, these patterns may not be applicable to less studied groups of organisms due to differences in natural history traits, such as dispersal mechanisms. To address this limitation, I examined the historical biogeography of three tribes of Deltocephalinae leafhoppers and a subfamily of planthoppers (Caliscelinae) and compared these data to biogeographic patterns observed in other grassland restricted lineages. In order to correctly infer biogeographic patterns, accurate phylogenies of each lineage are required. Using molecular sequence data from multiple genes, I inferred phylogenies for each Auchenorrhyncha lineage with a thorough sampling of each lineage including representatives from all major grasslands of the world. Along with individual phylogenies of each lineage, a combined dataset of Hecalini, Paralimnini, Deltocephalini, and the taxa included by Zahniser and Dietrich (2013) was also constructed. My phylogenetic analyses were used to both infer biogeographic patterns and to estimate divergence times. Grass feeding in Deltocephalini was inferred to be Palearctic in origin, and Old World origins were inferred for each target lineage. Hecalini and Paralimnini were inferred to be Palearctic in origin, while Deltocephalini + Tetartostylini was more widespread and Caliscelinae was inferred to be Ethiopian. All three leafhopper lineages were estimated to have diverged from their sister tribes around 50 MYA while Caliscelinae was inferred to be significantly older at 71MYA. These lineages therefore predate the formation of large contiguous grasslands, but as grasses were present for tens of millions of years prior to climatic conditions favoring grassland formation, these dates are reasonable. Each group was inferred to have invaded the New World, and in many lineages this invasion occurred approximately 40 MYA (with New World Caliscelinae again predating the Deltocephalinae). All lineages underwent periods of radiation corresponding to the rise of grasslands and the diversification of C4 grasses. In general these insect lineages show different biogeographic patterns from other lineages for which grassland biogeography has been reconstructed. Both horses and camels were inferred to have originated in the New World and then spread to the Old World, while bovids showed a similar Old World to New World spread. These patterns are similar to the Chiasmini, a related tribe of grassland Deltocephalinae, which based on an intuitive interpretation of the phylogeny, was thought to have originated in the Old World and then spread to the New World. Future work should examine additional grassland insect lineages to determine if these patterns are limited to Auchenorrhyncha or are found in a wider variety of grassland insects, such as some beetles and moths. Additional taxon sampling could also allow biogeographic reconstruction to be performed on more regional scales where different factors play a role in determining species ranges.
Issue Date:2014-01-16
Rights Information:Copyright 2013 Therese Catanach
Date Available in IDEALS:2014-01-16
Date Deposited:2013-12

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