Importance of Bees in Environmental Monitoring

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Importance of Bees in Environmental Monitoring

• The obvious utility of bees in pollination of
  crops and wild plants is obvious and generally
  well understood (at least by those of us here).
• The potential of bees for environmental
  monitoring is less well understood and this is
  what I wish to try to explain.

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Sex and death in bees

• The take home message is
  the unusual sex determining mechanism
  of bees renders them more susceptible to
  extinction than almost all other organisms.
• Haplodiploidy results in healthy haploid males
  and healthy diploid females, but sterile,
  inviable or triploid offspring producing diploid
  males.
• This is because sex in bees is determined by
  genotype at a single gene locus.

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DIPLOID MALESresult from homozygosity at the sex
locus
And are attempts at female production
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Diploid Males two categories
Diploid males
Colletes inaequalis
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Diploid Males and Extinction

• Large populations have many sex alleles and low
  diploid male frequencies.
• Small populations have few sex alleles and high
  levels of diploid male production.
• Small populations will therefore enter a special
  case of the extinction vortex.

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The Diploid Male Vortex
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Probability of extinction in haplodiploid
populations with and without DMP
NO DMP
DMP w/Inviable Diploid Males
DMP w/Sterile Diploid Males
Zayed and Packer 2005
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Genetically-induced extinction risk comes from
more than diploidy at the sex locus the genetic
load is associated with lethal and deleterious
alleles. Haplodiploids are though
to have less of this.
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DMP versus inbreeding depression in diploids

• Genetic load in a survey of threatened diploid
  animals accounted for an average increase in P(E)
  of 9.9 over ecological factors
  
  (Brooks et al 2002)
• When haplodiploid populations with similar sizes
  and growth parameters were modeled, DMP
  contributed to an average increase in P(E) by
• 52.7 - with inviable diploid males
• 63.2 - with effectively sterile diploid males

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Bees

• Found in almost every terrestrial ecosystem.
• Numerous guilds can be considered among the bees,
  some of these are
• Specialist/generalist floral hosts
• Below ground/above ground nesting
• Solitary/social
• Nesting/cleptoparasitic
• Are some of these likely to be more useful than
  others?

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Yes Bee traits as indicators of ecosystem health

• Specialist/generalist floral hosts
• Below ground/above ground nesting
• Solitary/social
• Nesting/cleptoparasitic

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Oligolectic bees
Centris mixta on Prosopis tamarugales
Caupolicana ruficollis on Loasa tricolor
Nolanomelissa toroi on Nolana
Hexp
Packer et al.,2005
Colletinae
Diphaglossine Colletine Panurgine
Megachilid Centris
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Bumble bees, as social bees, are also expected
to be at high risk
Bombus affinis a species that may be extinct
soon.
Courtesy Sheila Colla
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Cleptoparasitic bee species with a single host
bee Epeolus bifasciatus has a single host
species Colletes latitarsis which is a floral
specialists on Physalis
Images by Tai Roulston
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FINAL TAKE HOME MESSAGE

• Not only are bees important, they (with other
  haplodiploids) are likely to be excellent
  indicators of terrestrial ecosystem health.