Now showing 1 - 5 of 10
- ItemMorphological and molecular evolution of sea anemones as revealed by an emerging model organism, Aiptasia (Cnidaria, Actiniaria, Aiptasiidae)(2014-01-01) Grajales, Alejandro.;Sea anemones (Cnidaria: Actiniaria) of the family Aiptasiidae Carlgren, 1924 are conspicuous members of shallow-water environments and several species within the family are widely used as model systems for studies of cnidarian-dinoflagellate symbiosis and coral bleaching. Although previously published phylogenetic studies of sea anemones recovered the family Aiptasiidae as monophyletic, they only included partial sampling of its diversity. This study explores the diversity within this group of organisms in an integrative way, from the family to population levels. In this study, I explored the morphological and molecular diversity of the group using newly collected material covering the distribution of most of the described genera and species. The family Aiptasiidae was found to be a monophyletic lineage. Similarly, most of the genera within the family represent monophyletic lineages, with the exception of the genus Aiptasia, now divided into Aiptasia and Exaiptasia. Bellactis Dube, 1983 and Ragactis Andres, 1883 are now genera included within Aiptasiidae, in agreement with previous morphological studies and the morphological homogeneity observed here by the members of this family. In addition, I discovered new diagnostic morphological characters supporting the relationships among the major clades within the family. The molecular phylogenetic results provided evidence to diagnose two species within Exaiptasia: E. pallida -- a single widespread species -- and a new cryptic species, E. brasilensis sp. nov. -- restricted geographically to the southwestern Caribbean Sea and the southwestern Atlantic Ocean. Finally, although the algal diversity within the group showed no evidence of coevolution at the family level, an interesting pattern of adaptation and cladogenesis of the endosymbiotic algae (Symbiodinium spp.) was found within host species.
- ItemAnts (Hymenoptera, Formicidae) through space, time, and sociality : a history from amber.(2015-06) Barden, Phillip.With over 13,000 ecologically diverse species exhibiting worldwide ubiquity in vegetated terrestrial ecosystems, ants are one of nature's greatest success stories. Colonies range from a few dozen tiny workers housed inside of an acorn to millions of nomadic army ants known to consume even vertebrates. The ant fossil record is very rich, comprising thousands of amber and impression specimens spanning a hundred million years, the vast majority of which is Cenozoic. Until very recently, early ant history has been obfuscated by a lack of well-preserved fossils from the Cretaceous. Here, utilizing CT-scanning methodology and traditional methods, diverse species of ~99 million-year-old Cretaceous ants are described from Burmese amber, which together comprise over one-third of all known Cretaceous ants. Among them are trap-jaw predators with scythelike mandibles not known in any living or extinct ants, as well as enigmatic feeders with hair-coated mouthparts, and several species with morphology analogous to that found in modern ants while retaining plesiomorphic features. These and other unusual Cretaceous taxa are contextualized for the first time, with results that challenge traditional viewpoints regarding the diversity, phylogenetic placement, and sociality of the earliest ants known. In the age of molecular phylogenetics the role of fossils can be unclear. Most frequently, fossils are included in analyses solely as calibration points for divergence date estimates, a practice that relies on assumed taxonomy and excludes biogeographic information. To explore alternative roles for fossils in molecular-based biogeographic, phylogenetic, and temporal reconstruction, combined analysis methodology is explored -- first, with respect to a small genus, and then finally applied to a large sampling of all ant subfamilies. The genus Leptomyrmex is endemic to eastern Australia, New Caledonia and New Guinea. Over 25 years ago, a putative fossil Leptomyrmex was described from Dominican amber dated to the Miocene. In the absence of compelling evidence other than taxonomic discussions in literature, researchers have typically excluded the Dominican fossil from phylogenetic and biogeographic reconstruction. To test the placement of the fossil, published molecular sequences for modern Leptomyrmex and related groups were merged with a novel morphological matrix. Through combined analysis the fossil was recovered among modern Australasian Leptomyrmex, indicating that the current distribution is a reflection of a great contraction and more complex biogeographic history. This same methodology is applied to a much larger dataset including members of all modern ant subfamilies in a preliminary total-evidence analysis of ants.
- ItemMolecular and morphometric phylogenetics of Dryinidae and Bethylidae (Hymenoptera, Chrysidoidea)(2015-09) Tribull, C. M.Aculeata (Hymenoptera) is largely known for its bees, ants, and social wasps, from which most people would immediately recognize honey bees and paper wasps. However, sister to the clade of Apoidea and Vespoidea is the much smaller, and infinitely more enigmatic Chrysidoidea, which contains seven extant families that are relatively understudied. Unlike the other superfamilies, Chrysidoidea is exclusively parasitic -- although this behavior ranges from ectoparasitoidism to endoparasitoidism to cleptoparasitism (targeting solitary wasps and bees), as seen in Chrysididae (the cuckoo wasps). Dryinidae, which contains about 1700 species worldwide in 16 subfamilies, are parasitoids of Auchenorrhyncha (leafhoppers, planthoppers, and their allies) and are known to attack major rice and fruit crop pests. In Chapters II and III, the relationships within the family were investigated at the subfamily level. In Chapter II, a phylogeny reconstructed from 18S, 28S, Cytochrome Oxidase I (COI) and Cytochrome b (CytB) resulted in the resurrection of Thaumatodryinus to Thaumatodryininae to preserve the monophyly of Dryininae. Chapter III examined the utility of landmark analysis in parsimony using the methods implemented by Catalano et al. (2010) and subsequent publications. The trees constructed from the landmark analyses were incongruent with the combined molecular and morphological phylogeny, but landmark analyses could be utilized effectively to reconstruct species-level phylogenies for Dryinus and Gonatopus, both of which were found as nonmonophyletic in Chapters II and III. Chapters IV and V focused on Epyris, the largest genus within the subfamily Epyrinae, and Bethylidae as a whole. Epyris has long been suspected of being a taxonomic wastebasket, but the molecular phylogeny reconstructed from 16S, 18S, 28S, COI, and CytB is the first phylogeny to sample the worldwide breadth of its species diversity. Epyris was shown to be nonmonophyletic, although the type specimen, Epyris niger Westwood, was recovered in a clade with a distinct synapomorphy of large, nearly touching, scutellar pits. In Chapter V, five new species from Epyris sensu stricto were described from Western Australia and Queensland, and a key was provided to the known female Epyris of Australia.
- ItemPhylogenetic studies of apoid wasps (Hymenoptera, Apoidea) with insights into the evolution of complex behaviors.(2014-09-30) Payne, Ansel.The wasp superfamily Apoidea -- a group composed of more than 20,000 species of solitary, cleptoparasitic, and social bees, as well as a paraphyletic grade of more than 9,600 species of predatory and cleptoparasitic wasps -- has played an outsized role in the history of behavioral research. Favorite subjects of field naturalists and ethologists for more than two hundred years, these insects have evolved a tremendous diversity of behavioral strategies, each one an equally successful variation on a shared ancestral groundplan. Understanding the course of these evolutionary derivations and innovations is an important part of understanding insect behavior in toto, and one that requires a phylogenetically informed, comparative approach. As a contribution to ongoing efforts in apoid phylogenetic systematics -- and by extension to the study of behavioral evolution within the group -- the current work presents four phylogenetic studies of apoid taxa, with an additional fifth study examining the placement of Apoidea within Hymenoptera as a whole. Each provides some insight into the evolution of a complex behavioral syndrome, namely the development of predatory behavior from within a parasitoid wasp clade (Chapter II), the origins of cleptoparasitism in apid bees (Chapter III), trends in prey choice among philanthine wasps (Chapters IV and V), and innovations in nesting behavior within thread-waisted wasps (Chapter VI). In the first of these studies, I use a combination of direct optimization phylogeny reconstruction and clade sensitivity analysis to re-examine a previously published total evidence dataset based on 111 taxa from across Hymenoptera. This new analysis simultaneously reveals and formalizes deep topological instabilities within this important insect order, and shows how such instability can complicate back-of-the-envelope reconstructions of behavioral evolution (e.g., the origins of aculeate predatory behavior from within a paraphyletic "Parasitica"). In the second, I demonstrate once again the importance of combining multiple classes of phylogenetically informative characters through a simultaneous reanalysis of the bee family Apidae. By merging previously published datasets based on molecular, behavioral, and adult and larval morphological characters (and by providing new adult and larval character codings for taxa previously represented by molecular data alone), I add qualified support to a recently published, nucleotide-derived hypothesis concerning the origins of cleptoparasitism. This hypothesis -- that the trait evolved fewer times than previously supposed, with the nomadine and "melectine" lineages sharing a common cleptoparasitic ancestor -- is corroborated under a variety of different transformation cost parameters and appears relatively robust to the addition of morphological and behavioral data. The next two studies present the results of the most taxonomically comprehensive phylogenetic analyses of the digger wasp subfamily Philanthinae (Apoidea: Crabronidae) to date. While Chapter IV represents the first molecular analysis of the group to include species level terminals from all eight genera and all four tribes, Chapter V expands that work to include 66 newly coded morphological and behavioral characters. Although basal relationships among the four tribes remain either ambiguous or poorly supported, monophyly of the hyperdiverse, cosmopolitan genus Cerceris is strongly suggested for the first time -- a finding that challenges previous notions concerning the evolution of prey choice within the "beetlewolf" tribe Cercerini. Finally, the last study briefly examines relationships among the so-called "thread-waisted wasps" of the family Sphecidae sensu stricto as a prelude to a larger study of nest evolution within the group. While maximum parsimony analysis of 16 nest-related behavioral characters produces a largely unresolved topology, cladistic analysis of a three-gene dataset reveals new cases of paraphyly at both the tribal and generic levels. I briefly discuss the implications of this latter topology for our understanding of nest evolution within the group.
- ItemSystematics and morphological diversification of the Cordylidae (Squamata)(2013-09-05) Stanley, Edward L., 1982-The Cordylidae is a species poor but ecologically and morphologically diverse family of lizards endemic to sub-Saharan Africa. Although the majority of the cordylid species are strictly rupicolous (rock dwelling), the family also contains a diverse array of other specialist ecotypes. Due to this concentrated ecological and morphological variation, the family is an excellent system for studying macroevolutionary processes. Previous studies have hypothesized that the majority of diversity in the family evolved rapidly at the base of the viviparous subfamily (Cordylinae), possibly representing an adaptive radiation, but this has not been investigated empirically. The four central chapters of this thesis were designed to be synergistic, with each chapter providing information and helping develop hypotheses in the others. Chapter two places the phylogenetic relationships of the Cordylidae into a temporal framework using relaxed clock Bayesian analyses on an 11 gene, squamate-wide dataset with ten fossil calibrations. These analyses recover the viviparous cordylines as undergoing a period of rapid cladogenesis across the Oligocene-Miocene boundary, radiating into nine well-supported lineages, distributed around the edge of the great escarpment in South Africa. Chapters three and four focused on two different cordylid groups with complicated and unresolved taxomomic histories. By investigating species boundaries within the Smaug warreni species complex (chapter three) and Hemicordylus capensis (chapter four) I address whether the current taxonomy of the family accurately captures the actual species diversity of the family. A combination of phylogenetic, biogeographic and morphological analyses reveals new species within both groups. The fifth chapter attempts to test the hypothesis that the Cordylidae underwent an adaptive radiation following the evolution of viviparity. Morphological variation of the Cordylidae was represented through a combination of standardized ecomorphological measurements and novel, volumetric measurements of osteoderm distributions recovered using High-Resolution CT scanning. Ecological data for known cordylid localities was extracted from multiple commonly used climate layers. Morphological variation was correlated with microhabitat choice, but not with climatic variation. Existing analytical techniques and new methods reveal that the viviparous cordylids experienced an early burst of morphological diversification, while the oviparous subfamily, Platysaurinae, did not. These findings strongly support the hypothesis that the Cordylinae underwent a period of adaptive radiation during the Oligocene, possibly as a result of shifts in the climate and geological uplift of South Africa's Great Escarpment.