Hobbs, H.H., and D.C. Culver. 2009

of the L"SA _~arional ~Ylogical Society, Inc. -~- J the ~ational Speleological Society, Inc. 13 Cave Avenue Ennrsville.Alabama 35810-4431, U.S.A. 256-852-1300 E-mail: [email protected] Web page: http://www.caves.org All rights reserved, including the right to reproduce this book or portions thereof in any fonn or by any means, mechanical or electronic, including photocopying, recording, or by any information storage or retrieval system without permission in writing from the publisher. All inquiries should be addressed to the National Speleological Society. Editors: Arthur N. Palmer and Margaret V. Palmer Graphics: M.Y. Palmer andA.N. Palmer Formatting and photograph preparation: A.N. Palmer Library of Congress Control Number: 2007943932 ISBN: 9781879961289 Printed in the U.S.A. ged; and they, their contents, and their biota deserve our protection. Try to leave no trace of your _-hDDiJ:tmcm~ are on private property, and land-owner relations can be delicate. For these reasons, specific ~ ~ ~ IJM inrhuinf in publications of the National Speleological Society. Caves can also pose a danger to those 'T who lack experience. Access to caves, and assistance in meeting the requirements for safe .~ lUI!~aticjeJ i1:r rarwrrring local chapters of the NSS. 15 Cave Biology An Overview of Cave Biology in the USA The transition zone of caves is a dynamic region of constant darkn (aphotic), but where the microclimate is noticeably still affected Horton H. Hobbs III and David C. Culver surface events. Fluctuations in temperature and humidity, decreasi diversity of species, and lower biomass reflect the influences of bo AVES have traditionally been considered exotic and rare habitats, epigean and hypogean environments. Still further from the entrance, the Cbut in reality they are quite widespread. Wherher or not rhey are transition zone grades into a much less variable deep zone. This region - extensive, shallow or deep, or have small or large areas, they share a characterized by permanent darkness, greater environmental consran _ number of important characteristics. Permanent absence of light and and predictability, virtually no food production, and a community thus no phyroproduction (photosynthesis) are key features. Productivity dominated by small, generally rare, troglomorphic, obligate, aquatic is very limited except under rare circumstances. They exhibit relatively terrestrial invertebrates. constant environmental characteristics, at least in comparison with surface conditions, wirh limited variability in temperature and humidity. Ecological classification of cavernicoles Almost all subterranean voids (air- or water-filled) have some biological Historically, organisms residing in subterranean environments have been activity, but biomass is low and numbers and sizes of organisms are classified in various ways, beginning wirh Schiner (1854) and reviewed _ small. Thus, cavernicoles (cave-dwelling organisms) have to cope with Boutin (2004). The level of dependence on underground life, or the ext, complete darkness, limited food, and a reduction in daily and seasonal of adaptation to it, are rhe basis of some classification systems, whereas cues. Because of these unique biotic and abiotic characteristics, caves others are founded on various life-history traits and ecological criteria that are considered to be extreme environments that limit utilization and reflect the diversity of habitats that organisms occupy. Cavernicole is colonization by surface species. .general term applied to an inhabitant of caves (in rhe broad sense) with no restrictions concerning its association wirh rhe cave environment. Although Ecological zonation not necessarily accepted by all biospeleologists, the terms trogwfauna and It is often convenient to divide caves into ecological zones, each having stygofauna are employed for all subterranean terresrrial and aquatic fauna. distinct biological, chemical, and physical properties. The threshold respectively. Trogloxenes ("cave visitors") are terrestrial species rhat spellJ zone (subdivided into entrance and twilight zones, Figs. 15.1-15.2) varying amounts of time in caves (Fig. 15.3) but also are part of epigeaa is an ecotone, functioning as a transition between surface (epigean) and communities. They usually live and feed in surface habitats. For example, subsurface (hypogean) environments (Barr, 1967) and serves as a refuge some surface invertebrates and snakes (Fig. 15.4), birds, and mammals are from temperature and humidity extremes of the surface. Common exceptionally and passively drawn into caves. Troglopbiles ("cave lovers" inhabitants include the cave spider, Meta ova/is (Gertsch), which is well are facultative cavernicoles, able suited to live in this surface-subsurface ecotone; and many entrances ro live and reproduce in caves but in the eastern United States harbor one ro several nests of the phoebe, also in epigean habitats. These Sayomis phoebe (Latham). Migrating trogloxenes (see below; e.g., bats, include rhe cave salamander crickets) pass through this area, which can also be the transit zone Eurycea lucifoga (Fig. 15.5). for much of the organic matter that forms the base of many aquatic Troglobiontsexe permanently and and terrestrial cave communities. Direct sunlight supplies energy exclusively troglomorphic (see to the entrance area, giving it the highest productivity and greatest below), hypogean species such as environmental variability and biodiversity (see Culver and Poulson, blind snails (Fig. 15.6), beetles, 1970). Light diminishes significantly into the twilight zone where time and harvestmen (Fig. 15.7). The of day, season, configuration of the entrance, and external conditions prefix stygo- is applied ro aquatic affect rhe amount of light as well as the temperature and humidity. cavernicoles, and rhus stygoxene, stygophile, and stygobiont have definitions similar to those for the troglofauna categories, ex, that rhey apply only to aquatic cave-dwelling fauna. Aquatic habitats Water in caves comes from sinking surface streams and fro infiltration through the epikarst. Borh introduce various types a1.. quantities of organic material and sediment. It provides a much mo continuous and less restricted habitat than the terrestrial realm. Th epikarst is the zone of solutionally enlarged fissures and pores i the upper few meters of I r ,> • , I, ••' , rhe bedrock, which are generally filled partly or completely with soil. It is a perched aquifer that supports a distinct fauna (and can concentrate pollutants). It transmits Figure 15.4: A colubrid [Seotaphis ail Figure 15.1: Shaft entrance ecotone, Figure 15.2: The threshold (twilight) water, nutrients, and leghariensis (Holbrook)] snake, 55-m-deep Neversink Pit, Alabama. zone, Piercy's Cave, West Virginia. organisms horizontally t~Crack Cave 1, Carter County, Ken o 15: Cave Biology 393 Figure 15.5: The salamander Eurycea lucifuga Rafinesque. inWhite's Cave. Figure 15.9: Main stream passage in Russell Cave, Jackson County, Edmonson County. Kentucky.Visible length -8 ern. Photo by Rick Olson. Alabama, through which floodwaters introduce allochthonous vegetatal material to the ecosystem (see Fig. 15.10). Photo by Horton Hobbs. through poorly integrated voids and vertically rhrough conduits these habitats are located benearh and adjacent or small fissures, ultimately to to streams they are referred to as the hyporheos the phreatic zone (Pipan, 2005; (interstices of streams). In caves this is an Pipan and Culver, 2005). It is insufficiently studied habitat but is known to an ecotone between epigean and host a variety oflife forms (e.g., crustaceans such endogean waters. Aquatic epikarst as Barhynellacea; Gibert et al., 1994, 1997). communities live primarily in the In karst regions, most phreatic water has Figure 15.6: Carychium stygium network of small Hooded or partially slow How rates and long residence times, Call, 2 mm long, Adwell Cave, Hart Hooded cavities above the cave bur with minimal physicochemical fluctuations. County, Kentucky. Length -3 mm. below the surface. Within caves and Aquatic phreatic communities are found Photo by Rick Olson). beneath ceiling speleothems (Fig. in the permanent groundwater at or below 15.8), drip waters can accumulate in the cave itself, including the hyporheos. This depressions, forming isolated pools zone is occupied by stygobionr crustaceans, Figure 15.10: Sprout that harbor fauna (e.g., crustaceans fishes, and salamanders (e.g., the endangered from seed carried into such as copepods) that have washed amp hipod, Stygobromus pecki Holsinger, the Wilson's Cave, Edmon- our of the epikarst and are quite fish Trogloglanis pattersoni Eigenmann, and son County, Kentucky. distinct from cavernicoles inhabiting the endangered salamander, Eurycea rathbuni Photo by Rick Olson. nearby srreams. (Stejneger) in the Edwards Aquifer of south-central Texas (Fig. 15.11). Cave streams with sources largely from percolating epikarstic water Figure 15.7: Phalangodes armata tend to be very stable over time Tellkampf,White's Cave, Edmonson and space, whereas those supplied County, Kentucky.Length, withlegs, primarily from sinking surface -25 mm. Photo by Rick Olson. streams Huctuare grearly in How rate (a few mLlmin to tens of m3/min), and therefore also in physicochemical characteristics. These aquatic stream communities depend ultimately on dissolved and particulate organic matter (DOC and POC) derived from the surface (Fig. 15.9-15.10). Some organisms are free-swimming, open-water nektonic forms, and others are benthic species dwelling

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