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Energy budgets Several different energetic scenarios were modeled in this study using potential crayfish diets and resource supply rates so that the energy-limitation hypothesis could be explored from an energy-dynamics perspective. Collectively, the energy budgets constructed for O. australis do not show that crayfish demand is higher than resource supply rates, which indicates that resource deficits do not exist and that these populations do not require more resources than are present within the cave stream channels. In this study, the energetic demands of crayfish populations were bracketed between strict detritivory and strict predation. While leaf and wood supply rates were large enough in all caves to fulfill crayfish demand, it is unlikely that O. australis feeds strictly on detritus because: i) the majority of growth in juvenile surface crayfish taxa has been attributed to the consumption of animal material (Whitledge & Rabeni 1997), ii) both surface and cave crayfish are known to be omnivorous (Weingartner, 1977; Nystrӧm, 2002; Parkyn et al., 2001), and iii) O. australis maintained in the laboratory does not consume conditioned leaf litter (M.P. Venarsky, personal observation). Thus, these populations of O. australis were most likely supported by macroinvertebrate production, rather than organic matter. The energetic models based on a macroinvertebrate diet suggest that the Hering and Tony Sinks populations of O. australis consumed all of the macroinvertebrate production, while a very small surplus of macroinvertebrate production was present in Limrock. These results suggest O. australis is likely limited by macroinvertebrate production, which is not a feature unique to cave ecosystems. The near complete consumption of prey production by predators has been observed in several surface streams (see Huryn & Wallace, 2000). Because of the limited potential for prey surpluses, competition for resources among O. australis and other predators in these cave 115
systems is likely high, especially in Tony Sinks and Limrock where the large variability in macroinvertebrate biomass indicates that large quantities of resources are concentrated into small areas. Thus, the energetic budgets constructed for O. australis in this study provide the first quantitative explanation of why K-selected life history characteristics, highly efficient physiologies, and enhanced sensory systems for food acquisition are an evolutionary advantage to obligate cave predators. Conclusions Support for the energy-limitation hypothesis has historically come from either laboratorybased studies focused on individual physiological characteristics (e.g. metabolic rates) of obligate cave species or field based population- or community-level studies looking for correlations between resource availability and species biomass or productivity. While each approach has its strengths, neither typically places its results within the context of energy dynamics of actual cave ecosystems (e.g. resource supply rates vs. consumption and growth). The trophic basis of production approach (sensu Benke & Wallace, 1980) used in this study incorporated all aspects of the physiology and life history of O. australis and placed them within the context of potential resource supply rates. Collectively, the results from this study provide robust support for the energy-limitation hypothesis and add to the body of evidence supporting the energy-limitation hypothesis in cave and groundwater ecosystems (e.g., Datry et al., 2005; Cooney & Simon, 2009; Huntsman et al., 2011b; Chapters 3). Additionally, this study shows that populations sizes of obligate cave species can be much larger than visual surveys would suggest and that cave ecosystems are capable of supporting larger populations of obligate cave species than previously appreciated. 116
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THE INFLUENCE OF ENERGY AVAILABILIT
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ABSTRACT Detritus from surface envi
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LIST OF ABBREVIATIONS AND SYMBOLS m
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NC IL ON U.K. VIAT VIE Fig. North C
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AIC K-S Akaike information criterio
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laboratory work and was an excellen
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LIST OF TABLES TABLE 2.1 TABLE 2.2
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LIST OF FIGURES FIGURE 2.1 (a) Box
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FIGURE 4.3 Growth models for Orcone
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chemolithoautotrophy-based systems;
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ecology, 51, 31-53. Gibert J. & Cul
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CHAPTER 2 EFFECTS OF ORGANIC MATTER
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community structure in cave “pits
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communities and how variation in co
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the different source locations was
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of natural-log transformed data (%
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peak in organic matter in Big Mouth
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Figs. 5a, b). The breakdown rate of
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per litter bag. Similarly, Huntsman
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ags was the greater retention of li
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Historically, limited resource inpu
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Culver, D.C. & Pipan, T. (2009) The
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Merritt, R.W., Cummins, K.W. & Berg
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Table 1. Mean (1 S.D.) macroinverte
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Table 2. Mean (±1 S.D.) daily temp
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Figure 1. (a) Box and whisker plot
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Figure 3. Non-metric multidimension
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Figure 5. Box and whisker plot of l
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streams, while the obligate-cave sp
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More recent observational and exper
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of netting (mesh size 2.5×1.5-cm)
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the two end-members. This conservat
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crop organic matter significantly i
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macroinvertebrate biomass to levels
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and surface streams (20-35,000 g m
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these factors, the stable isotope a
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surface streams. Thus, it is likely
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subsides to ecosystem dynamics have
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populations. Journal of Applied Eco
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Poulson T.L. & Lavoie K.H. (2001) T
Page 81 and 82: Wood P., Gunn J. & Perkins J. (2002
Page 83 and 84: Table 2. Mean (±1 standard deviati
Page 85 and 86: Table 2. Continued Chironomini Para
Page 87 and 88: Figure 1. Mean (bars are standard e
Page 89 and 90: Figure 3. Non-metric multidimension
Page 91 and 92: CHAPTER 4 REXAMINING EXTREME LONGEI
Page 93 and 94: individuals, he predicted that it w
Page 95 and 96: A phylogeographic study by Buhay &
Page 97 and 98: differences in size structure among
Page 99 and 100: and females in Tony Sinks Cave were
Page 101 and 102: Estimates of life span for O. austr
Page 103 and 104: available size-classes were well re
Page 105 and 106: References Anonymous (1999) Cave Sc
Page 107 and 108: Huryn A.D. & Wallace J.B. (1987) Pr
Page 109 and 110: Whitmore N. & Huryn A.D. (1999) Lif
Page 111 and 112: Table 2. Estimated life span (years
Page 113 and 114: Figure 1. Annual growth increment (
Page 115 and 116: Figure 3. Growth models for Orconec
Page 117 and 118: CHAPTER 5 CONSUMER-RESOURCE DYNAMIC
Page 119 and 120: following incidental inputs of orga
Page 121 and 122: Temperature data were not available
Page 123 and 124: minimum (Venarsky et al., 2012b). A
Page 125 and 126: 100% organic matter (i.e., maximum
Page 127 and 128: Macroinvertebrate biomass varied si
Page 129 and 130: Discussion The energy-limitation hy
Page 131: crayfish captured in most months we
Page 135 and 136: function of microbial films in grou
Page 137 and 138: Crustacean Biology, 4, 35-54. Momot
Page 139 and 140: Whitmore N. & Huryn A. (1999) Life
Page 141 and 142: Table 2. Assimilation efficiencies
Page 143 and 144: Table 3. Continued Tanypodinae 0.03
Page 145 and 146: Table 5. Estimates of mean wood and
Page 147 and 148: Figure 1. (A) Box and whisker plot
Page 149 and 150: CHAPTER 6 OVERALL CONCLUSIONS Due t
Page 151 and 152: characteristics (e.g., higher growt
Page 153 and 154: characteristics, highly efficient p
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