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Open Access Publications from the University of California

The Holarctic Hacklemesh Spider Genus Callobius (Araneae: Amaurobiidae): Morphology, Systematics, and Population Biology

  • Author(s): Lew, Stephen Ellis
  • Advisor(s): Will, Kipling W.
  • et al.

Interest in the California Floristic Province as a study region for scientists interested in biodiversity, evolution, systematics, and phylogeography has been increasing over the last several years. The amaurobiid spider genus Callobius (Chamberlin) occurs throughout the Northern Hemisphere, but is particularly common in western North America and particularly diverse in the California Floristic Province. An understanding of the evolutionary history of Callobius would contribute a great deal to this growing body of work, but the genus has received little attention since being revised in 1972. Since that time, a great deal has changed in the way biodiversity is studied. The Hennigian revolution changed the fundamental framework of systematics, and molecular techniques based on DNA sequences have brought enormous inferential power to bear on questions of systematics and population genetics, as well as almost every other discipline in organismal biology.

In my doctoral work I have approached Callobius in the context of phylogenetic systematics and the biogeography of the California Floristic Province. First, I have taken a broad approach to the morphology of Callobius, particularly the morphology of the copulatory organs, as it might apply to cladistic investigations both within Callobius and more broadly among spiders. Second, I have undertaken a phylogenetic analysis of the subfamily Amaurobiinae, to illuminate evolutionary pattern within Callobius as well as between Callobius and other amaurobiine genera. And thirdly, I have used geometric morphometrics and population genetics to look for divergence within the widespread species Callobius severus.

I have produced an atlas to the genitalic morphology of Callobius, and propose a morphological diagnosis that is more consistent with principles of homology than those previously in use. I have also found and described the male of Callobius pauculus, previously known only from females. Although my phylogenetic analysis did not resolve the relationships between the amaurobiine genera, it does offer some support for the monophyly of Callobius and identifies a clade of California Floristic Province neoendemic species. My study of Callobius severus supports infra-specific structure, and suggests that the geography of the California Floristic Province is influencing the evolution of Callobius in patterns similar to its influence on other taxa.

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