Studies on the Cave- Spider Family Leptonetidae
- Author(s): Ledford, Joel M.
- Advisor(s): Griswold, Charles E
- Roderick, George R
- et al.
The spider family Leptonetidae Simon, 1890 includes 17 genera and 213 species worldwide. They are broadly distributed in the Holarctic and typically associated with cool, moist habitats such as leaf litter, moss, rotting logs, and caves. The North American fauna is divided into two subfamilies, the Archoleptonetinae and Leptonetinae, with representatives in California through the Southern U.S. and Mexico. Five genera are currently recognized (Platnick, 2010), the most diverse of which is Neoleptoneta Brignoli, 1972 with a center of diversity in Texas where most species are known only from caves (Gertsch, 1974). Their restricted distributions and specialized biology have made them conservation priorities and two Texas species, Neoleptoneta microps (Gertsch, 1974) and N. myopica (Gertsch, 1974), are listed under the U.S. Endangered Species Act.
The impetus for this study was a series of collections produced over the past thirty years which have dramatically increased the number of records for the family, including the discovery of several unknown sexes and new species. Additionally, detailed morphological study using scanning electron microscopy (SEM) has revealed a wealth of new characters many of which have implications for relationships within the family and among spiders as a whole. Lastly, fresh collections for several genera in Alabama, California, Mexico, and Texas have facilitated the use of molecular data to develop phylogenetic hypotheses within the family for the first time. The primary objective for the study is to revise the systematics of the North American genera, with particular emphasis on the taxonomy and relationships within the Archoleptonetinae and the Texas cave fauna. The study is divided into three chapters, the results of which are briefly summarized below.
In the first chapter, a detailed morphological study of the genus Archoleptoneta revealed the presence of a cribellum an calamistrum representing the first cribellate member of the Leptonetidae. The morphology and relationships for the family are reviewed and the genus Darkoneta is described to include the ecribellate archoleptonetines. Three new species are also described from California, Mexico, and Guatemala.
The second chapter uses molecular sequence variation from three genes to produce a phylogeny for the North American Leptonetidae, with emphasis on the relationships of Neoleptoneta Brignoli, 1972. The placement of two incertae sedis species, Leptoneta brunnea (Gertsch, 1974) and Leptoneta sandra (Gertsch, 1974) are also considered and four new genera are described. Morphological data are traced on the molecular phylogeny and patterns of cave evolution are discussed.
The third chapter revises the taxonomy of the genus Tayshaneta, including the descriptions of ten new species from Texas. All Tayshaneta species are diagnosed and keyed, and comparative images using scanning electron and compound light microscopy are provided. Relationships among Tayshaneta are also discussed, including detailed descriptions of their morphology. Lastly, the karst faunal region (KFR) conservation strategy in Central Texas is evaluated using revised species distributions.