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Rosemary G Gillespie
Faculty
University of California Berkeley
Environmental Science Policy and Management
Berkeley, CA USA
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| Archaeid spiders and their relatives (Araneae, Archaeidae): fossil placement, biogeography and evolution of the carapace morphology |
| Author(s) |
Hannah M Wood, Rosemary G Gillespie, Charles Griswold |
| Info |
Poster category:
Systematics |
| Abstract |
Molecular and morphological phylogenetic analyses are performed for living and extinct archaeids and for outgroup taxa representing 20 different spider families sampling throughout the Araneomorphae. Fossil archaeids are examined using X-ray Computed Tomography in order to understand phylogenetic placement of extinct lineages. Additionally, a molecular phylogenetic analysis of living archaeids is performed to elucidate relationships among extant species from Australia, Madagascar and South Africa. Biogeographic findings within different continents as well as between continents are discussed. The limits of the superfamily Palpimanoidea is examined. Furthermore, evolution of the carapace shape is examined from a phylogenetic context. |
| Evolution of a complex, novel structure, the trap-jaw mechanism, in spiders (Mecysmaucheniidae, Araneae) |
| Author(s) |
Hannah M Wood, Rosemary G Gillespie, Charles Griswold, Damian O Elias |
| Info |
Talk category:
Systematics |
| Abstract |
Trap jaw mechanisms have been described for the ant genus Odontomachus but is virtually unknown in one of the largest arthropod classes, the arachnids. The trap jaw mechanism has evolved twice independently in spiders, once in the family Pararchaeidae and once in the family Mecysmaucheniidae. The underlying structural mechanism for employing a trap jaw is unique in both families, with Mecysmaucheniids achieving the fastest known movements in arachnids. Within the mecysmaucheniids there is variation in both carapace and jaw shape and in the speeds of the jaws closing. Phylogenetic analyses of molecular data results in a mecysmaucheniid phylogeny that can be used to examine the evolution of this trait among lineages from New Zealand and Chile as well as to examine how this trait relates to distribution patterns. The biomechanical properties of this complex trait are examined among different lineages. |
| Transcriptomics of exuberantly color polymorphic Theridion species (Araneae: Theridiidae). |
| Author(s) |
Peter J Croucher, Geoff S Oxford, Rosemary G Gillespie |
| Info |
Talk category:
Molecular Evolution |
| Abstract |
Parallel evolution of complex traits provides some of the most remarkable examples of evolution through natural selection. Among spiders, an interesting example of this phenomenon is provided by the demonstration among disparately related members of the Theridiidae of complex color polymorphisms consisting of multiple combinations of yellow, red and black dorso-abdominal pigmentation that are considered to consist of ommochromes In all studied species evidence suggests that the polymorphism is maintained by balancing selection. Given the similarity among phenotypes, and the presumed role of selection, the question is: How and to what extent is the similarity due to independent evolution on non-homologous pathways, versus differential expression of homologous pathways. In order understand the molecular basis of this parallel evolution of color polymorphism and generate a battery of spider genomic resources, we have used Illumina next-generation sequencing technology to reconstruct the transcriptomes of the two highly polymorphic spiders T. californicum and T. grallator and the genome of T. grallator. Here we focus on the assembly and annotation of tens of thousands of T. californicum gene transcripts and the identification of expressed color-pigment metabolic pathways. Results to date have given intriguing insights into numerous homologies across the genome, as well as allowing characterization of a surprisingly rich endo-symbiotic/parasitic community including nematodes and bacteria. Most importantly, we have identified key enzymes in a variety of pigment pathways, including ommochrome, pteridine, papiliochrome, heme and possibly melanin; suggesting that the potential array of pigments available to these spiders may be far greater than previously believed. |
| Population genomics in a changing landscape: Area effects and natural selection in the exuberantly polymorphic spider Theridion californicum (Araneae: Theridiidae). |
| Author(s) |
Peter J Croucher, Geoff S Oxford, Athena Lam, Rosemary G Gillespie |
| Info |
Poster category:
Molecular Evolution |
| Abstract |
The spider Theridion californicum exhibits a dramatic dorso-abdominal color polymorphism comprising at least 12 color morphs. Using nuclear (AFLP) and mitochondrial genetic markers (CO1) we explore the population genetic structure of this species in the San Francisco Bay area. Focusing on Charles Lee Tilden Park, an area, like many in the region, that has experienced a return to a ‘natural’ (forested) landscape following centuries of human management (rangeland), we demonstrate a lack of isolation-by-distance in this species, instead revealing a pattern of ‘area effects’ indicating recent expansion of populations from scattered refugial pockets of native vegetation. Comparisons among AFLP markers and the color locus indicate that many AFLP loci, together with the color polymorphism itself, are likely to be maintained by balancing selection. As would be predicted, these markers show little of the population genetic structuring revealed by the neutral AFLP and mtDNA loci. |
| Adaptive radiation on remote islands: Comparison of diversification across the remote archipelagos of Polynesia |
| Author(s) |
Rosemary G Gillespie |
| Info |
Talk category:
Systematics |
| Abstract |
The Pacific Ocean contains more islands than the rest of the world's oceans combined. The most remote high islands are those of Polynesia, notably the Hawaiian Islands, and the three archipelagos of French Polynesia: the Society, Marquesas, and Australs. Each of these archipelagos is a hotspot, with islands arranged chronologically from the south east. While patterns of adaptive radiation are relatively well known in Hawaii, comparable patterns in the other archipelagos of Polynesia are less well known. Here I will compare patterns of diversification of spider lineages across the archipelagos to assess the similarity in species, pattern and rate of diversification, and dynamics of community assembly. The Societies show high endemism, in particular on the youngest high island of Tahiti, with the genus Tetragnatha a prominent element of the spider biota at both high and middle elevations; relationships appear to be horizontal, with cloud forest species closely related to each other. The Marquesas show high endemism, with Tetragnatha again a prominent element, the highest diversity being on the older islands. The Austral Islands are an older, smaller, and lower archipelago; here, the dominant lineages are Tangaroa tahitiensis (Uloboridae) and Misumenops rapaensis (Thomisidae). These taxa are endemic to the archipelago rather than an individual island, yet there are large genetic distances between island populations, with sequential colonization of islands. Compared to Hawaii, diversification is less pronounced, and community assembly on the youngest island matches to the second youngest island of the Hawaiian chain. |
| Investigating the genetic basis of the color polymorphism in Theridion californicum |
| Author(s) |
Franziska S Brunner, Christopher J Winchell, Grace L Anderson, Andrew Yee, Peter J Croucher, Rosemary G Gillespie |
| Info |
Poster category:
Molecular Evolution |
| Abstract |
The leaf-dwelling spider Theridion californicum displays a remarkable polymorphism in abdominal color pattern, exhibiting more than 12 color morphs. The evolutionary history and ecological significance of this polymorphism is a topic of ongoing research. A recent population genetic study using AFLPs has demonstrated that, similar to T. californium's congener the Hawaiian Happy Face spider T. grallator, the polymorphism is maintained by frequency-dependent (balancing) selection. A next important step in the investigation of the evolutionary basis of this polymorphism is the identification of genes involved in color expression and patterning. Ommochrome pigment genes, such as vermilion and cinnabar, belong to a widely conserved pathway that has previously been demonstrated to contribute to color patterning in many arthropods including Heliconius butterflies, Drosophila melanogaster and Tribolium castaneum. We show that several ommochrome genes are expressed in the abdominal epidermis of T. californicum, making them likely candidates for the genetic basis underlying the color polymorphism. By performing in situ hybridization experiments on the abdominal epidermis, we are comparing spatial expression patterns of the aforementioned ommochrome pathway genes to the different color morphs to investigate the individual significance of those genes in T.californicum for color pattern development. Differentially expressed genes could be suitable candidates for further population genetic and phylogenetic investigations into the molecular basis and role of natural selection in shaping the independent evolution of remarkably similar color polymorphisms in multiple representatives across the family Theridiidae. |
| Does Hawaiian Tetragnatha venom composition vary with feeding strategy? |
| Author(s) |
Andrew W Wood, Rosemary G Gillespie, Greta J Binford |
| Info |
Poster category:
Other |
| Abstract |
Spider venoms are a rich source of largely unexplored biodiversity, and we have much to learn about the evolutionary mechanisms that generate this stunning diversity. The Hawaiian radiation of Tetraghatha offers a unique system with which to address this question. The majority of the 35 Hawaiian Tetragnatha species are orb-weaving spiders, however, a recently derived lineage has abandoned this ancestral state to adopt a cursorial feeding strategy, and have become obligate wanderers (Gillespie 1999). Binford (2001) demonstrates some differences between the venoms of these two species, but was unable to specifically identify venom components. In this study, I apply transcriptomic methods to 1) characterize the venom of two species of Hawaiian Tetragnatha (one orb-weaving and one wandering) and 2) analyze differences and similarities between them. After screening cDNA libraries for both species I identified a total of 5 distinct putative toxins including homologs of theraphotoxins and lycotoxins, none of which were common to both species. However, the vast majority of cDNAs that I identified were ribosomal or other ‘housekeeping’ sequences. This study demonstrates that after methodological optimization, the venom of Hawaiian Tetragnatha can be successfully characterized and will be useful to address questions regarding the evolution of chemical biodiversity. |
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