A Phylogenetic Study of Neotropical Sheet-Weaving Spiders (Araneae, Linyphiidae)

Spiders (Araneae) are a megadiverse group of arthropods, present in all terrestrial ecosystems as top predators, playing a crucial role as main controllers of insect populations. Among the more than 47,000 described species of spiders, the perhaps most emblematic ones are the orb weaver spiders, famous for producing the orb web, one of the most iconic of nature’s constructs. Linyphiidae Blackwall, 1859 is the most species-rich lineage of spiders within orb weavers. Also known as sheet web spiders, linyphiids represent almost 10% of all described spider species. Despite a long history of studies, much about linyphiids are still shrouded in mystery. The knowledge about Neotropical representatives of the group is quite deficient, with many genera and species only known from monographies centuries old. In addition, we are still far from a broad consensual agreement on the internal phylogenetic relations within the family, having non-monophyletic groups yet being used as to define subgroups within the family. In this dissertation, we concentrate our efforts in increase our understanding about poorly known linyphiid spiders from the Neotropics and to provide a modern-standard phylogenetic hypothesis for the family. First while revising the Caribbean monotypic genus Lomaita, we define and establish a new monophyletic grouping within Linyphiidae, the MPME clade, whose main synapomorphic feature are enlarged posterior median eyes (PMEs) placed in mounds (hence MPMEs or “mounded PMEs”). Later, we monographed the genera Jalapyphantes and Selenyphantes and, for the first time, hypothesized its position within Linyphiidae. Jalapyphantes had its species number increased in one and Selenyphantes in five new species. We found that those two genera are sister group to another Neotropical exclusive genus, Pocobletus and together, those three form a monophyletic lineage of their own, the Pocobletus clade. A third section of this study monographed the also monotypic genus Diplothyron, whose was putatively associated with the MPME clade. Diplothyron species numbers increased from one to twelve, of which five were misplaced in different genera while six are newly described. Diplothyron was shown to be distributed along the mountain chains of central America being exclusively found on cloud forest areas. Finally, we gathered the largest dataset ever compiled for the family to produce a new phylogenetic hypothesis for Linyphiidae, with a special focus on Neotropical specimens. Using morphological, behavioral and molecular information, we build upon previous datasets in order to test old and new grouping hypothesis of sheet web spiders. We confirmed that the subfamilies Erigoninae, Mynogleninae and Stemonyphantinae, as well as the newly proposed MPME clade and Pocobletus clade are monophyletic. Nonetheless, other commonly used names such as Linyphiidae, Micronetinae and Ipainae, are not linked to natural groups. We then propose a new arrangement for the family as well as new circumscription for Pimoidae, the sister group of Linyphiidae.

Author

• da Silva Moreira, Thiago

Language

• en

Keyword

• Taxonomy
• Pimoidae
• Neotropical
• Linyphiidae
• Spiders
• Systematics

Date created

• 2019

Type of Work

• Dissertation

License

• All rights reserved

Rights statement

• In Copyright

GW Unit

• Biological Sciences

Degree

• Ph.D.

Advisor

• Hormiga, Gustavo

Committee Member(s)

• Lipscomb, Diana
• Pyron, Alexander
• Wood, Hannah
• Clark, James

Persistent URL

•  https://scholarspace.library.gwu.edu/etd/mp48sd441