20th International Congress of Arachnology

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DENVER MUSEUM OF NATURE & SCIENCE REPORTS | No. 3, July 2, 2016
20th International Congress of Arachnology
supplementing this AE dataset with previously published
transcriptome data from representatives of the Dionycha
and other RTA-clade members, to further resolve basal
salticid relationships and explore which dionychan families
are plausible sister groups to the salticids. We hope to not
only improve the resolution of deep relationships among
these taxa, but also gain a general understanding of how
these different methods of genome-wide sequencing can be
integrated in phylogenetic analyses.
Oral presentation
Unraveling the Chelicerata tree of life:
phylogenomic resolution of chelicerate inter-
relationships based on deep taxon sampling
Rosa Fernández1, Caitlin Baker 1, Julia Cosgrove1 ,
Prashant Sharma2, Gonzalo Giribet1
1Museum of Comparative Zoology & Department of
Organismic and Evolutionary Biology, Harvard Uni-
versity. 26 Oxford Street, Cambridge MA, USA 02128;
2Department of Zoology, The University of Wisconsin
- Madison. 250 N Mills St, Madison, WI, USA 53706
Chelicerates constitute the second largest branch of the
arthropod tree of life and include several iconic lineages,
such as spiders, scorpions, harvestmen or horseshoe crabs.
For decades, scientific endeavors aiming to resolve the
internal phylogeny of chelicerates have resulted in discrep-
ant hypotheses, with different authors proposing discordant
topologies based both on molecules and morphology. While
considerable effort has been paid to resolve the relation-
ships within several chelicerate orders, the backbone of
the chelicerate tree of life remains unsettled, with several
studies showing strong systemic conflicts in phylogenetic
signal even after exhaustive analysis of several thousand
orthologous genes. The open questions about how the main
groups of chelicerates are related limit how we interpret
the timing of the diversification of this major component
of the arthropod biota. Building upon previous efforts
based on transcriptome sequencing, we contribute to this
discussion by presenting a large injection of novel Illumina
transcriptome data for virtually all chelicerate lineages,
including previously unsampled orders such as Palpigradi
and Opilioacarida, and a substantially expanded taxonomic
coverage, especially for orders such as Pseudoscorpiones,
Schizomida and Amblypygi. For this, we analyzed close to
seventy transcriptomes of chelicerates and constructed an
array of data sets to independently optimize gene number,
gene occupancy, phylogenetic informativeness, or gene con-
servation and analyzed them using different phylogenetic
methods and evolutionary models. In this contribution, we
will discuss our findings in the context of previous phyloge-
netic hypotheses and explore the diversification timing
of one of the oldest arthropod groups with a fossil record
extending back to the Cambrian.
Keywords: Chelicerata, transcriptomics, systematics,
phylogenomics
Student - oral presentation
Volatile chemical communication in female
Latrodectus sp.
Andreas Fischer1, Manfred Ayasse1, Maydianne Andrade2
1Institute of Evolutionary Ecology and Conservation
Genomics University of Ulm, Germany 2Integrative
Behaviour & Neuroscience Group University of
Toronto Scarborough, Canada
Volatile chemical communication allows information
transfer over long distances, and is important at many
stages of spiders’ life cycles. Volatile chemicals are impor-
tant for attracting mating partners, and this has been
well-studied. Although this communication pathway is
likely also important for choosing nesting sites, we know
very little about the use of this type of information in
decision-making about web building sites. In this study,
we tested the reaction of adult females to volatile cues of
other females in two widow spiders (Latrodectus hasselti
and L. hesperus). Other studies have shown that males
can detect the feeding status, behavioral type and maturity
of potential mates based on volatiles, so we assumed this
same information would be available to adult females. We
performed dual choice olfactory experiments in y-tubes in
which we exposed adult virgin L. hesperus or L. hasselti
females to controls (empty tubes) and a variety of volatile
stimuli whose source (females) varied in terms of feeding