Phylogenetics and Host Relationships of Plantbugs Inhabiting Native Cypress Pine Celia Symonds The...
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Transcript of Phylogenetics and Host Relationships of Plantbugs Inhabiting Native Cypress Pine Celia Symonds The...
Phylogenetics and Host Relationships of
Plantbugs Inhabiting
Native Cypress Pine
Celia SymondsThe University of Sydney and the Australian Museum
Honours in Biological Science 2005
Supervisors
Dieter Hochuli & Gerry Cassis
Introduction
“Much of evolution is coevolution”
(John Thompson (2004) The Geographic Mosaic Theory of Coevolution)
However, the study of coevolution has been slow to progress
In part, due to: the complexity of species interactions, and the lack of phylogenies for interacting organisms, to
enable cospeciation analysis.
Coevolution and Cospeciation
Coevolution • reciprocal adaptation between two interacting organisms
e.g. Ehrlich and Raven’s study of butterflies and their larval host plants (1964)
Cospeciation• the joint speciation of two or more lineages that are ecologically
associated• coevolution that occurs in macroevolutionary time
e.g. classic example is between a host and its parasite
Describing Cospeciation
Assessing congruence between phylogenies (relationship trees) of two interacting organisms
Source: Page ed. (2003) Tangled Trees
Gopher Phylogeny
LousePhylogeny
Cospeciation and other processes
• Very few cases, mostly animal parasites and animal hosts.
• Plant-insect associations are one of the most dominant interactions in natural systems.
• Few clear coevolutionary relationships established between plants and insects.
• Noise in the data to date……..
Source: Page ed. (2003) Tangled Trees
The aim of my project
To investigate the potential for cospeciation to explain
the relationship between a host specific group of
undescribed plantbugs and native cypress pine.
Study System - Plantbugs (Miridae)
sp. 22, ex. Callitris preissii, WA
sp. 22, ex. Callitris preissii, WA
sp. 22, ex. Callitris preissii, WA
sp. 25, ex. Callitris rhomboidea, NSW
Native Cypress
PineCallitris &
Actinostrobus
Callitris bayleyi, NSW
Callitris gracilis, VIC
Callitris rhomboidea NSW Callitris rhomboidea NSW
Callitris sp. ‘Emerald Creek’, QLD
Callitris intratropica, QLD
Approach
Species discrimination – morphospecies• Morphological analysis – comparative taxonomic study
• Molecular analysis – sequencing of 2 mitochondrial DNA loci, 16s & COI
Phylogenetic analysis • Separate and combined analysis of morphological and
molecular data using maximum parsimony in PAUP*
Cospeciation analysis
Biogeographic associations?
Pygophore ultimate abdominal segment of male plantbugs
Diagnostic characters include:
• dorsal opening
• lobes
• tubercles
• left and right parameres
Morphological Characters
sp. 23
sp. 25
sp. 7
Dorsal Ventral
Parameres (male “claspers”)
left
right
Morphological Characters
0.1mm
sp. 4 sp. 10 sp. 13 sp. 20 sp. 26
Morphological analysis
Findings:• 66 characters, of which 62 are of the male genitalia
• 31 species from total of 42 localities and 13 Cypress pine species
• complex associations – up to 3 species from the same locality– 29 species of plantbugs found on only one Cypress pine
species – multiple species of plantbugs from a single Callitris species
(up to 10)
Morphology strict consensus tree
sp. 3sp. 11sp. 10sp. 24sp. 25sp. 15sp. 20sp. 22sp. 21sp. 23sp. 6sp. 31sp. 30sp. 16sp. 7sp. 13sp. 28sp. 8sp. 19sp. 18sp. 1sp. 2sp. 5sp. 29sp. 14sp. 12sp. 9sp. 4sp. 26sp. 27Orthotylus marginalisAustromiris viridissimusOrthotylus clermontiella ]
Three main species groups:• One strongly supported
Higher level:• Strong support for species
groups
Basally:• Unresolved
Synapomorphy support for species groupings
outgroup
Bootstrap support 50-79Bootstrap support >80
Molecular analysis
Findings:• 16s - ~500bp sequence for 17 species• COI - ~500bp sequence for 10 species
Limitations:• Incomplete data set
• Generally only one sample per species
Molecular – 16s strict consensus (MP) Similar patterns:• strong support for species
groups observed in morphological data
• basally unresolved
• some conflict with morphology in placing of particular species
• Likelihood analysis supporting parsimony results
sp25
sp24
sp15
sp5
sp12
sp16
sp29
sp8
sp1
sp3
sp10
sp11
sp20
sp21
sp22
sp9
O. clermontiella
sp27
Austromiris sp.
Bootstrap support 50-79Bootstrap support >80
Molecular – COI strict consensus
Similar patterns:• support for species groups
observed in morphology and 16s
• basally unresolved
• some differing placement of species to 16s tree
• artefact of small sample
Bootstrap support 50-79Bootstrap support >80
sp3
sp10
sp29
sp25
sp26
sp28
sp1
sp12
sp16
sp9
O. clermontiella
O. marginalis
Austromiris sp.
Cospeciation analysis
Method:• Tree reconciliation analysis approach using the ‘Jungles’ method in
TreeMap 2.0 (Charleston and Page 2002):
– Mapping of parasites (plantbugs) onto the host (plant) tree generating all potentially optimal solutions
– Assessed for significance against a cospeciation distribution pattern from random host and parasite trees
– Detects:• cospeciation• host switching• duplication (intrahost speciation)• extinctions (sorting events)
• Separate analysis of morphological and molecular trees undertaken, due to unresolved basal relationships in the plantbug phylogenies
Cospeciation analysis Tanglegram for morphological data
Actinostrobus
rhomboidea
endlicheri
Paluma
oblonga
muelleri
intratropica
Emerald Ck
columellaris
glaucophylla
tuberculata
gracilis
sp4sp9sp5
sp14
sp29sp8
sp19
sp12sp7
sp13
sp1sp2
sp16sp30
sp6sp23sp22
sp21sp15sp24
sp25sp3
sp10
sp11
Patterns found:
• high level of host switching
• no clear cut pattern of cospeciation
• most plantbugs species highly specific to one host plant species
• 2 bug species found to inhabit more than one host – host switching phylogenetically conserved
• ‘missing the boat’ or extinction events
• speciation in plantbugs occurring below the level of speciation in the plants
host plant plantbug
Historical BiogeographyMethod: • Three area statement analysis (TAS: Nelson & Ladiges, 1991, Syst. Zool. 40).
• Areas of endemism from Crisp et al. (1995; Syst. Biol. 44) and Cracraft (1991; Aust. Syst. Bot. 4).
Findings:• East / west coast divide
- confers with Crisp et al.
• Novel area relationship- Eyre Peninsula + (Adelaide + Eastern Desert).
From: Crisp et al. (1995)
Conclusions
1. This plantbug and cypress pine interaction is not a clear cospeciation relationship.
2. Biogeography may better explain the plantbug host relationships.
Host specificity is not a sufficient criterion for predicting parallel cladogenesis.
Insect-plant relationships are more complex than conventional host-parasite relationships and thus reciprocal evolution needs to be examined in the context of their:
• direct 1:1 relationships,
• their historical biogeography, and
• other selection pressures.