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are potentially capable of supporting relatively large populations of obligate cave species. Additionally, the energetic budgets provide the first quantitative explanation of why K-selected life-history characteristics and highly efficient physiologies are an evolutionary advantage to obligate cave species. Introduction The movement of resources among ecosystems, commonly referred to as resource subsidies (sensu Polis & Strong, 1996), is an ever-present feature within the ecological landscape. The roles that such subsidies play in structuring recipient ecosystems can vary widely as a function of resource quantity, quality (e.g., C:N:P ratios), and type (e.g., nutrient vs. organic matter vs. prey; see Cebrian, 1999; Moore et al., 2004; Marczak et al., 2007). Cave ecosystems, however, appear to represent an extreme endpoint along the resource subsidy spectrum because the lack of light prevents primary production, which causes nearly all caves (except those systems based on chemolithoautotrophy; see Engel et al., 2004) to be reliant on inputs of organic matter from surface environments to support biological productivity (Poulson & Lavoie, 2001; Simon et al. 2007). However, reduced surface connectivity typically limits allochthonous inputs, which has caused caves to be characterized as energy-limited ecosystems (Hüppop, 2001 & 2005). One line of evidence that indicates cave ecosystems are energy-limited environments is the remarkable set of traits that are shared among many obligate cave species, such as lower metabolic rates, increased starvation resistance, and more K-selected life-history characteristics (e.g. long life span, slow growth rate, and reduced fecundity; see Hüppop, 2001 & 2005; Venarsky et al., 2012b). Energy limitation also appears to be an important factor structuring entire cave communities, as several studies have reported community shifts or increased biomass 101
following incidental inputs of organic pollutants (Sinton, 1984; Smith et al., 1986; Madsen et al., 1991; Notenboom et al., 1994; Simon & Buikema, 1997; Sket, 1999). However, evidence from such studies is confounded because organic pollution is typically a heterogeneous mixture of organic and inorganic material (i.e., organic matter, dissolved nutrients, microbes, and toxins), making it impossible to discern which component or combination of components causes changes in recipient communities. More recent studies have found that consumer biomass and productivity are positively related to energy availability in cave and groundwater ecosystems unaffected by pollution (Datry et al., 2005; Cooney & Simon, 2009; Huntsman et al., 2011b). While these previous physiological and ecological studies have provided a general test of the energy-limitation hypothesis, they have not placed the demands (e.g. consumption and growth) of the cave community within the context of energy dynamics (e.g. resource supply rates). Consequently, it is not known if cave communities are actually energy-limited in the sense that they are consuming all or a large proportion of the available resources, which has been shown in a number of surface aquatic systems (sensu the Allen Paradox; see Huryn, 1996; Huryn & Wallace, 2000). In this study, the energetic demands of the obligate cave crayfish Orconectes australis were compared to resource availability in its cave stream habitat. This study was conducted in three separate cave systems with varying quantities of resources (e.g. organic matter and macroinvertebrates) to test two hypotheses. First, the energy-limitation hypothesis predicts that consumer productivity is limited by energy availability. Consequently we tested the hypothesis that secondary production of O. australis is positively correlated with standing crop organic matter and macroinvertebrate prey biomass using a 5+-year mark-recapture data set. Second, since O. australis is the dominant macroconsumer by biomass in these cave systems, we 102
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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
Page 67 and 68: macroinvertebrate biomass to levels
Page 69 and 70: and surface streams (20-35,000 g m
Page 71 and 72: these factors, the stable isotope a
Page 73 and 74: surface streams. Thus, it is likely
Page 75 and 76: subsides to ecosystem dynamics have
Page 77 and 78: populations. Journal of Applied Eco
Page 79 and 80: 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: CHAPTER 5 CONSUMER-RESOURCE DYNAMIC
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 and 132: crayfish captured in most months we
Page 133 and 134: systems is likely high, especially
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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