Tuesday, December 20, 2005

ENV: Karst Cave Spiders

From Mike Quinn


The U.S. Fish and Wildlife Service announced today that as a result of a comprehensive review, it will not add a cave spider, the Karst Meshweaver (Cicurina cueva), to the list of Federally endangered species.

The Service contracted with a geneticist to perform the study that showed the spider to be genetically indistinguishable from two other Circurina spiders that inhabit 22 caves in southern Travis County and two caves in northern Hays County. As a result of the study the Service has concluded that the karst meshweaver is not a separate species and thus is not eligible for protection under the Endangered Species Act (ESA).

The study was peer reviewed by fourteen scientists with expertise in genetics, morphology and/or conservation biology. Most peer reviewers agreed the study was well done and its methods were scientifically sound.

"Our decision that C. cueva doesn't qualify for ESA protection was based on the best available scientific information," said Bob Pine, Field Supervisor of the Ecological Service's office in Austin. "In the absence of a precise, definitive taxonomic classification, we'll treat the three spiders as one species."

The Service published its decision in the Federal Register on December 19, 2005. A copy of the notice is available on the internet at http://www.fws.gov/ifw2es/AustinTexas/ or by calling 512-490-0057.

Cicurina cueva spends its entire life underground. A member of the Dictynidae family, the spider measures less than one-half inch long. As a response to their underground environment, these spiders exhibit adaptations such as extended legs, no eyes, and no pigment. Subterranean dwelling spiders such as these require stable temperatures and constant, high humidity and rely on a healthy community of native plants and animals on the surfaces above the caves for their continued survival.

The petition to list Cicurina cueva with critical habitat was submitted by Save Our Springs Alliance (SOSA), Save Barton Creek Association, and Austin Regional Group of the Sierra Club in July 2003. The fate of the small spider has been closely watched because some hoped that a positive finding would affect the proposed construction and operation of State Highway 45
South. In reality, the Endangered Species Act has rarely stopped projects - most have been able to move forward while simultaneously providing protection for threatened and endangered species.

Victoria Fox, External Affairs
Southwest Region - USFWS

I couldn't find the Dec. 19, 05 Federal Register, but this appears to be the relevant document detailing the spider research (MQ):

Project Title: Genetic and morphological analysis of species limits in Cicurina spiders (Araneae, Dictynidae) from southern Travis and northern Hays counties (TX), with emphasis on Cicurina cueva Gertsch and relatives

Authors: Pierre Paquin & Marshal Hedin
Department of Biology, San Diego State University

Summary of Project Results:
We have combined genetic and morphological data to understand species limits in cave limited Cicurina spider species (Araneae: Dictynidae) from caves in central Texas. Particular emphasis is placed on Cicurina cueva and close morphological relatives (C. reyesi and C. bandida) found
in southern Travis and northern Hays counties. The project included the collection of specimens from the field, illustration and qualitative comparison of morphological variation, and molecular phylogenetic analysis of mitochondrial DNA sequence data. Our primary findings can be briefly summarized as follows:

When analyzed and compared to a comprehensive sample of Cicurina taxa from the region (Travis, Hays & Williamson counties, TX), sampled populations of C. cueva form a monophyletic group (clade) on a mitochondrial phylogeny. Populations representing both C. bandida and C. reyesi are deeply embedded within this C. cueva genetic clade. This observation, in addition to consideration of female genital morphology, suggests that these three named taxa represent variants of a single species.

This single species is not genetically homogeneous (as might be predicted if there were high levels of gene flow across caves), but instead shows geographic-based genetic structuring. This finding makes biological sense, as we would expect geographically adjacent cave populations to share more genetic similarity than caves that are distant in space. The genetic structuring observed is a natural consequence of the fragmented nature of cave habitats, and the unique habitat limitations of these spiders (these spiders are cave-restricted and totally eyeless).

Despite an overall pattern of geographic-based genetic structuring, there is some evidence for gene flow between caves and cave systems. Furthermore, there is no predictable pattern of morphological variation associated with geography. A similar genital morphology, with slight variations, is shared across the entire distribution of this species.

We do not formally propose synonymy in this report, as such a formal taxonomic decision must be based on publication in a scientific journal. Instead, in this report we informally refer to the morphologically variable and genetically divergent populations within this single species as the "C. cueva complex". Members of this complex are found in over 20 caves from a geographically-confined region. Despite the morphological and genetic variation observed, this single species is clearly distinct and easily distinguished from other Cicurina species in the region.

full text of 21 page PDF file:

Mike Quinn
Invertebrate Biologist, Nongame & Rare Species, Texas Parks & Wildlife

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At 4:20 PM, Blogger skittergitchy said...

Very interesting. Can tell me what cave spiders live in sea caves in Maine?


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