Are habitats important in mediating range shifts in tropical fishes? Hayden Beck PhD Candidate...
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Transcript of Are habitats important in mediating range shifts in tropical fishes? Hayden Beck PhD Candidate...
Are habitats important in mediating range shifts in tropical fishes?
Hayden BeckPhD Candidate
Supervisors: Prof. David Booth and Dr David Feary
GREAT BARRIER REEFEAST AUSTRALIAN
CURRENT
• Recruitment of tropical reef fishes along SE Australian coast during summer
• Hotspot of climate change: establishment of permanent populations
• Importance of physical habitats for early life stages of tropical fishes?
Model System: SE Australia
1500km
AUSTRALIA
1. Selection for habitat generalists (i.e. no coral dwellers)
Predictions: importance of habitats in core range
2. Larger-scales: organisation of distributions by interactions between wave-exposure and swimming abilities
3. Finer-scales: association with specific benthic habitats
Result 1. Only habitat generalists observed• 5695 individuals belonging to 30 species (Underwater surveys: 2
years, 4 latitudes, estuarine and coastal reef sites – 100s m apart)
NO CORAL DWELLERSPlanktivores (51%) Invertivores (24%)
Grazers (24%) Piscivores (1%)Images: D. Harasti and Australian museum
Result 2. Association with wave-exposure
0 0.05 0.1 0.15 0.2 0.25 0.3 0.350
50
100
150
200
250
300
350
400
450
500
Wave-exposure (Index 0-1)
Den
sity
(Ind
ivid
uals
/100
0m²)
• Significant correlation of densities of tropical fishes with wave-exposure on larger-scales
Result 2. Association with wave-exposure
0 0.05 0.1 0.15 0.2 0.25 0.3 0.350
5
10
15
20
25
Wave-exposure (Index 0-1)
Spec
ies
Rich
ness
(Spe
cies
/100
0m²)
• Significant correlation of species richness of tropical fishes with wave-exposure on larger-scales
• No correlation with water temperatures, benthic complexity, predator densities or substrate composition
Result 3: Swimming modes match wave-exposure
Pectoral Pectoral-Caudal Caudal0
10
20
30
40
50
60
70
80
90
100 95.7998211902358
16.1660937396936
3.38363501474252
Primary swimming mode
Mea
n (±
SE) p
ropo
rtion
of a
ssem
blag
e (%
)
*
* Coastal reefs
High swimming performance
*
Poor swimming performances
Estuarine reefs
Result 4. Association with sea urchin barrens• 1028 individuals belonging to 15 species (Underwater surveys: 2
years, 7 coastal reef sites; barrens and kelp habitats - 10s m apart)
NO species associated with kelp habitat
Images: D. Harasti
Conclusions
•4
Within new range lacking coral: • Habitat generalists successful
• Wave-exposure: strong structuring mechanism on larger-scales
• Benthic habitat: organise finer-scale distribution