species-energy relationships in the deep sea (marine lecture 3) Flashcards

1
Q

Why are there ecogeographic gradients in diversity?

A
  • biodiversity not evenly distributed worldwide
  • why?
  • hypotheses: climate, age, area, geometry
  • availability of environmental energy may be key
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2
Q

What is the relationship between energy, productivity and diversity?

  • productivity-diversity relationships
A
  • productivity determines food availability
  • higher productivity should therefore support more species
  • but diversity may decrease at highest productivities
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3
Q

What is the relationship between energy, productivity and diversity?

  • species-energy theory
A
  • aka “more individuals hypothesis”
  • higher productivity increases abundances of individual species
  • therefore higher productivity increases likelihood of rare species reaching viable population sizes
  • may also increase population growth/ speed post disturbance recovery rate
  • at highest productivities may lead to competitive dominance, decreasing diversity
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4
Q

What is the relationship between energy, productivity and diversity?

  • resource ratio theory
A
  • if productivity isn’t limiting, something else is
  • different species dominate either end of productivity spectrum
  • coexistence and diversity highest at intermediate productivities
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5
Q

What is the relationship between energy, productivity and diversity?

  • more specialisation theory
A
  • resources too rare at low productivities to support specialisation
  • more energy, more opportunities for specialists to escape competitive exclusion
  • more productivity therefore = more diversity
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6
Q

What is the relationship between energy, productivity and diversity?

  • one more trophic level
A
  • higher productivity allows for greater food chain length
  • increases predator diversity
  • higher predator diversity can prevent competitive exclusion at lower trophic levels
  • higher productivity = higher diversity
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7
Q

What is the relationship between energy, productivity and diversity?

  • competitive exclusion
A
  • competition increases in high productivities
  • dominant species exclude inferior competitors
  • higher productivity = lower diversity
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8
Q

What are the challenges explaining relationships between energy, productivity and diversity?

A
  • several hypotheses make similar descriptions
  • what is the scale? taxonomic/spatial/temporal
  • what do we mean by diversity? energy?
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9
Q

What do we mean by energy?

  • how is this measured on land
  • problem with terrestrial studies
A
  • energy available to life
  • on land quantified by productivity, measured by NDVI
  • terrestrial studies problem is that productivity is always highly correlated with other factors proposed to explain diversity e.g. temperature/ precipitation
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10
Q

How can deep sea studies be test-beds for species-energy theory?

A
  • basically 0 in situ productivity
  • quantify productivity as C flux (food availability)
  • productivity decoupled from temperature as is cold everywhere in deep sea
  • chemical/thermal energy potentially isolated from each other
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11
Q

What are species-energy relationships in deep-sea molluscs?

A
  • strong unimodal relationship b/w energy and diversity in deep-sea gastropods and bivalves
  • relationship much stronger than between diversity w temperature or depth
  • chemical energy drives mollusc diversity from continental shelf onto abyssal plain
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12
Q

Is energy always more important than temperature?

A
  • temperature drives organismal processes (e.g. metabolic rate), no evidence that chemical energy does
  • variation in c flux instead drives patterns of biomass, abundance and diversity
  • temperature more important on continental shelf/upper slopes
  • C flux more important in deep sea
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13
Q

How do wood falls provide a deep sea energy source?

A
  • wood transported in great quantities from rivers to ocean
  • saturates and sinks
  • energetically isolated food source in deep sea
  • rapidly colonise by a range of organisms, mostly wood fall specialists entirely dependent on wood for energy
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14
Q

How can experimental wood falls be used to test species-energy relationships in deep sea? Do they support them?

A
  • wood of varying size placed in deep sea
  • discrete habitat boundaries
  • whole communities collected and analysed for easy quantification of diversity on wood with different amount of energy (size)
  • individuals increase with resource (wood) size
  • so do species
  • richness is a function of abundance, supporting species-energy hypothesis
  • some evidence for rarer species on larger logs
  • more specialisation, narrower niches
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