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?

Morphological Characters

1mmsp. 25

Morphological Characters

0.5mm

Dorsal vestiture

simple setae simple & scale like setae

sp. 7 sp. 17

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

Aedeagus (male genitalia)

Morphological Characters

sp. 23 sp. 25 sp. 7

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.

Acknowledgements

My supervisors Dieter Hochuli and Gerry Cassis

My colleagues Michael Wall and Nik Tatarnic

Mike Charleston at the University of Sydney

Gary Nelson at the University of Melbourne

Illustrations by Hannah Finlay

SEMs by Sue Lindsay