Aphid Population

1
Aphid Population

• Soldier Types and their Association with
  Non-Soldiers

Christina Sartorio Zachary Brady
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Fossil History

• Aphids are related to Adelgids and Phylloxerids
  who evolved about 280 million years ago
• The oldest known fossil is Triassoaphis cubitus
  from the Triassic about 220 million years ago

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Species of Aphids

• There are about 4000 species of aphids in the
  world of which about 250 are serious pests.
• Scientists believe that the number of species
  remained relatively small until the angiosperms
  (flowering plants) became more common, then as
  the aphids adapted to these new and rapidly
  varying plants their species numbers also
  increased.

4
Aphid Range and Appearance

• Twenty-five percent of all plant species are
  infested with aphids, and though it is believed
  the species of aphids has followed that of
  plants, not all groups of plants are equally
  infected with these parasites.
• Aphids are part of the Superfamily Aphidoidae and
  are described as small (1-10 mm) soft bodied
  insects with, or more commonly without, wings.

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Species Variation

• The Compositae, the 3rd most common plant family,
  supports the most aphid species (605 species),
  but the Orchidacea, the 2nd most common plant
  family, only supports 9 species of aphids while
  the Rosaceae which is only the 22nd most common
  plant family supports the 3rd highest number of
  aphid species (293 species).

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Aphid Anatomy

• Aphids possess a proboscis which originates
  between and behind the forelegs, their antennae
  has two thick basal segments and a flagellum
  composed of up to 4 segments, the last of which
  is divided into a proximal part and a thinner
  distal part

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Feeding Habits

• Aphids feed from the phloem of plants which they
  tap into with the stylets of their proboscis.
  They gain access to the phloem vessels from 3
  main parts of the plant, stems, leaves, and
  roots. Their stylets, which are contained within
  the proboscis when the aphid is not feeding, are
  very thin and could suffer damage while being
  pushed into the plant or bend in an unwanted
  direction.

8
Movement

• Most aphids do not have wings, and in general
  they move very little, and their lives consist of
  feeding and giving birth.
• Aphids are weak fliers and in still air they move
  at about 1.6 to 3.2 km per hour. Their migrations
  can be extensive and they often take advantage of
  favorable winds to enhance their flight
  efficiency.

9
Protection

• An aphid will kick out at an attacker and attempt
  to drive it off, if this does not work it will
  pull up its stylets and proboscis and walk away.
• Some species can also exude a special waxy
  solution from their siphunculi over an attacker,
  while doing this it generally releases an alarm
  pheromone alerting nearby aphids that danger is
  close at hand.

10
Predators

• Aphids are relatively common and in the right
  circumstances they occur in large numbers, for
  this reason there are quite a number of animals
  which use aphids as a food source.
• Some include the Chinese praying mantis and the
  ladybug.

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Behavioral Classes

• Some species have soldier aphids and others
  only have non-soldier aphids.
• Soldiers are not as common as non-soldiers, but
  are more apt to fending off predators and various
  dangers than non-soldiers.

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The Project

• Purpose
• To determine whether or not there exists a
  significant genetic difference between soldier
  and non-soldier aphids.
• Hypothesis
• If genetic data from non-soldier and soldier
  aphids are compared, then a significant
  difference between the two will be apparent.

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Procedure

• Using the Student Interface to the Biology
  Workbench, we searched the databases for aphid
  genes.
• We found a common gene named cytochrome oxidase
  subunit I. This gene is the last carrier in the
  electron transport system of cellular respiration.

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Soldiers

• Searching for the cytochrome oxidase subunit
  I gene, we found 8 soldier aphid species
• -Pseudoregma koshunesis
• -Pseudoregma alexanderi
• -Ceratovacuna nekoashi
• -Ceratoglyphina styracicola
• -Nipponaphis distyliicola
• -Tuberaphis taiwana
• -Tuberaphis styraci
• -Pseudoregma bambucicola

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Non-soldiers

• We also found 14 non-soldier species
• -Chaitophorus tremulae
• -Chaitophorus leucomelas
• -Chaitophorus populialbae
• -Sitobion avenae
• -Acryrthosiphon pisum
• -Acryrthosiphon kondoi
• -Macrosiphum creeli
• -Fibriaphis fimbriata
• -Euschizaphis sp.
• -Diuraphis noxia
• -Schizaphis graminum
• -Paradoxaphis plagianthi
• -Paradoxaphis aristoteliae
• -Paradoxaphis plagianthi

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• Using these genes, we created ten groupings, each
  containing genes from six aphid species. There
  were three soldier species and three non-soldier
  species in each group.
• After feeding these groups into the program, we
  used the Clustalw program to align the genetic
  sequences.
• Then, to make the data easier to analyze, we used
  the DrawTree program to make the sequences into
  trees.
• The next 10 slides show the resulting trees.

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Tree 1
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Tree 2
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Tree 3
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Tree 4
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Tree 5
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Tree 6
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Tree 7
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Tree 8
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Tree 9
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Tree 10
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Observations and Results

• The results were varied. Some of the trees
  clearly demonstrated the hypothesis, such as
  numbers 2 and 9.

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• However, the vast majority of the trees were less
  clear. In many of these, one or more of the
  non-soldier aphids were genetically closer to the
  soldier aphids than their fellow non-soldiers.
• This occurred in trees numbered 1, 3, 4, 5, 6, 7,
  8, and 10.

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Conclusion

• Our hypothesis, a significant difference between
  non-soldier and soldier species will be apparent,
  was not supported by our research.

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Further Research

• A possible explanation for our results is that
  the aphid population first split genetically
  according to plant species or geographic area.
  Further research is needed to examine this
  possibility.
• Also, further research can be done using a larger
  sample size of aphid species.