Phylogenetic Analysis of Apterigote Taxa: Diplura, Collembola, Machilidae, Thysanura

1. Overview of a Phylogenetic Analysis of the Apterigote Taxa of Diplura, Collembola, Machilidae, and Thysanura Presented by Brian Iken October 21, 2009 Bioinformatics for Biologists

2. Introduction to Diplura www.cals.ncsu.edu/.../ soilpix/images/diplura.jpg Ameatabolous arthropod Apterous- Lacks wings Mouthparts retracted inside the head Long antennae and a pair of tail-like cerci Occasionally known as two-pronged bristletails

3. Introduction to Collembola www.idlab.ento.vt.edu/.../ images/collembola.gif Apterous, entognathous hexapod Very large lineage of hexapod Possess a collophore or tubelike structure on the ventral side of the first abdominal segment of the body Also known as springtails for the curled spring-like furcula abdominal appendage that allows for the animal to leap away from predators

4. Introduction to Machilidae Wingless, elongated, if somewhat cylindrical body with a notable humped thorax. Have three tails, two cerci and a long central tail called an epiproct Partially retractable mouthparts and large compound eyes This order is fairly primitive compared to the other hexapods changing little since its origin in the early Devonian period http://k43.pbase.com/.../ 2/59083112.Machilidae1.jpg

5. Introduction to Thsyanura Characterized by their three long tail-like filaments Flattened, elongated or oval bodies with small or no compound eyes Lepismatidae is the largest representative family of Thsyanura with over 200 described species Also referred to as silverfish for the silver glistening scales www.ucmp.berkeley.edu/.../ uniramia/firebrat.gif

6. Current Phylogenetic Viewpoints Sequencing and bioinformatic studies have not yet fully resolved the phylogenetic relationships between these four groups of hexapods . Diplura and Collembola are most commonly grouped together and in some cases are listed as a separate monophyletic class called Entognatha. Historically, however, we have seen the inclusion of the order of Thysanura sometimes called Zygentoma with Diplura and Collembola to form a paraphyletic class termed Apterygota. Machilidae at one time was considered to be part of Thysanura but is now considered to be part of its own separate order called Archeognatha that exists as a part of Apterygota.

7. Methods Used in the Literature for Analysis Utilize molecular markers such ribosomal RNA genes, sequenced protein encoding genes such RNA polymerase, Histone H3, and Elongation Factors, or mitochondrial gene sequences. Maximum Parsimony Trees plus bootstrapping analysis Maximum Likelihood Trees plus bootstrapping analysis Bootstrapping could be nonparametric or parametric Bayesian Analysis Minimum Evolution Analysis of LogDet-Transformed Distances

8. Remaining Questions to be Answered There is conflicting molecular data over whether modern sequencing data supports the inclusion of Collembola with Diplura as a monophyletic group or if the order of Thysanura is possibly monophyletic with the above two orders as well. Is there conclusive molecular support for the monophyletic grouping of the orders of Diplura and Collembola? Is Thysanura monophyletic with Diplura, Collembola, or both? In essence is their support for the formation of the class Entognatha.