BIO3132 Lecture 10: Week 6. Fish Case Study and Reproduction I
31 May 2018
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;Week 6. Fish Case Study and Reproduction I
FISH CASE STUDY – GEOGRAPHIC VARIATON, DISTRIBUTION AND SPECIATION IN
THE PACIFIC BLUE EYE FISH
• Dispersal abilities of freshwater fish
o Both terrestrial environment an sea can represent a significant barrier to dispersal
between drainages
o As a result most species tend to show strong patterns of population genetic structuring
o Eg. common jolly has marine lifecycle -? Low patterns of genetic structuring because it
can tolerate saline conditions
whereas pygmy perch has high genetic structuring
• Movement between drainages:
o Depends on connectivity of freshwater
-may occur over geological time through changes in sea level or rearrangement of
drainages or river courses
-flood may also connect drainages or release large plumes of freshwater into the sae
(shorter time scales)
o Can leave clues
• Pacific blue eye:
o Small freshwater fish from eastern Australia
o Occur in a range of habitats from rainforest streams to swamps, tidal mangrove creeks
and offshore islands
o Also shows great deal of geographic variation (difference in length and body markings)
THOUGHT QUESTION
What can you infer about the species dispersal ability based on its distribution an habitat? (Pacific
blue eye fish)
- wide distribution -> have high dispersal
- more closely related to common jolly?
- Occur in a range of habitats from rainforest streams to swamps, tidal mangrove creeks and
offshore islands
• Aim: generate a robust phylogeny based on genetic data
o Genetic evidence shows high degree of population structuring
o Means that dispersal between drainages is not so easy for blue eyes
-genetic evidence also suggests this
o Geographic location of the split is significant because it implies biogeographic barrier
(i.e. Burdekin Gap – split between Townsville and cairns, Townsville is a dry region)
find more resources at oneclass.com
find more resources at oneclass.com
THOUGH QUESTION
Phylogenetic results suggest that there are two distinct genetic groups of pacific blue eyes. How
can we test whether these groups represent separate species or maybe even a species on the
verge of splitting into two?
-scan sequence the genome (was expensive back then, can probably do relatively easily now)
-do behavioural stuff – try get them to breed
• Reproductive isolation - Mate recognition is important:
o Cornerstone of the speciation process
o Can vary between and within species
o Divergence of mate recognition systems are correlated with the degree of isolation
between groups
o Degree of genetic differentiation is often inferred from geographic distance
o Assumption is that the more distance = allopatry should reflect less gene flow, longer
isolation and more divergent selective regimes
• Aim: To investigate female preference for local versus foreign males in the Pacific blue-eye fish
o Male morphometric traits (size of fins)
-fish overlap with appearance
-nelligen and willinga overlap
-stone and toss overlap
o Experiment 1: choice between local and foreign males
Opaque barrier between males – see how often female hangs around with
which male
Ross females prefer local males (significant)
Willinga females prefer local (signififcant)
Females prefer local male to a distant population
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Fish case study geographic variaton, distribution and speciation in. Low patterns of genetic structuring because it can tolerate saline conditions whereas pygmy perch has high genetic structuring: movement between drainages, depends on connectivity of freshwater. May occur over geological time through changes in sea level or rearrangement of drainages or river courses. What can you infer about the species dispersal ability based on its distribution an habitat? (pacific blue eye fish) Genetic evidence also suggests this: geographic location of the split is significant because it implies biogeographic barrier (i. e. burdekin gap split between townsville and cairns, townsville is a dry region) Phylogenetic results suggest that there are two distinct genetic groups of pacific blue eyes. Scan sequence the genome (was expensive back then, can probably do relatively easily now) Stone and toss overlap: experiment 1: choice between local and foreign males. Opaque barrier between males see how often female hangs around with which male.
