Dispersal + Connectivity

Question 1

European pink sea fans?

Answer 1

Compared genetic profiles of European populations.
Irish fans genetically different from other European pops - more geographically isolated.
Irish fans more vulnerable (can’t be replenished by other pops) = need more protection.

Question 2

Invertebrate life cycles?

Answer 2

Adults mostly sessile = rely on larvae for dispersal.
Release gametes into ocean - fertilised + form embryo.
Larvae move in water column, then settle.

Question 3

Coral reef fish life cycles?

Answer 3

Juveniles live in seagrass/mangroves away from predators.
Some adults don’t disperse far (eg: gobies + blennies stay in small area whole life).
Some take huge migrations (eg: tuna).

Question 4

Dispersal + pop structure?

Answer 4

Recent studies suggest more barriers to connectivity than originally thought - more genetic structure than expected, given high dispersal potential + oceanographic conditions. 
3 possible dispersal scenarios:
 - Large-scale gene flow + mixing. 
 - Local pop structure. 
 - Local retention.

Question 5

Theoretical dispersal models?

Answer 5

Island model: All pops self-recruit + contribute evenly to well-mixed larval pool.
Stepping stone model: Pops exchange larvae w/ nearest neighbours = isolation by distance.

Question 6

Quantifying source + sink of larvae?

Answer 6

Oceanography.
Larval biology in lab.
Genetics of adult pops.

Question 7

Pelagic larval duration?

Answer 7

= Length of time larvae viable in water column.

Question 8

Types of larvae?

Answer 8

Lecithotrophic: Non-feeding = depend on yolk provided by parents.
Planktivores: Feed on plankton as they travel = longer PLD.

Question 9

Delayed settlement?

Answer 9

Obligate larval period = dispersal. Develop into competent larvae when ready to settle. Delay settlement until suitable conditions. 
Urchin (A. fragilis) can delay settlement up to 252 days. 
Sea slug (A. Juliana) can delay up to 311 days.

Question 10

Scheltema study?

Answer 10

Distributions of teleplanic larvae across pacific.
Drift bottles indicated currents could carry larvae 2000-4000km.
Larval duration significantly correlated w/ dispersal distance, but many exceptions.

Question 11

Geochemical tags?

Answer 11

Natural tags generated by natural variations in environmental conditions (temp, salinity, water chem) - recorded by elemental/isotopic composition of calcified structures (otoliths, statoliths, scales, shells).
Inject enriched barium into adult females = pass isotope tag to offspring.

Question 12

Geochemical tags + mussels?

Answer 12

Found difference in 2 mussel species recruitment, despite originating in same area - use different current systems to disperse.

Question 13

Larval tagging of fish?

Answer 13

Tetracycline dye in post-natal eggs can be traced in otoliths.
Eg: Used in 10 million Ambon damselfish. Found evidence of 15-60% self-recruitment in pop.

Question 14

Lagrangian models?

Answer 14

= Particle-tracking simulations coupled w/ hydrodynamic models. Used to produce larval dispersal kernels. High computational costs.

Question 15

Dispersal kernels?

Answer 15

= Probability that larvae will settle a given distance from release location.

Question 16

Cowen et al (2000).

Answer 16

Transport endpoints created for 10,000 virtual larvae (clownfish + damselfish) along west coast of Barbados.
Avoid east-west surface layer = enhance local retention.

Question 17

Coastal boundary layer?

Answer 17

Dispersal distance up to 59% shroter in simulations w/ CBL, + self-recruitment increased by up to 3 orders of magnitude.

Question 18

Microsatellite markers?

Answer 18

Genetic marker for parentage analysis - calculate Fst value.

Question 19

Planes et al (2009).

Answer 19

Kimbe Island clownfish.
40% clownfish larvae settled into anemones derived from parents resident in that reserve.
But juveniles found as far as 35km away (longest distance marine larvae has been tracked) = 10% of recruitment in adjacent MPAs.

Question 20

PLD + genetic structure?

Answer 20

Poor correlation between genetic structure (Fst) + PLD.

Question 21

Larval behaviour + dispersal?

Answer 21

Ontogenic vertical migration enhances retention of meroplanktonic larvae in coastal zones.

Question 22

Butler et al (2011).

Answer 22

Caribbean spiny lobster (P. argus): Early stage larvae positively phototactic - moved closer to light.
Behavioural transition in response to light occurred 100 days after hatching (negatively phototactic).

Question 23

Jones et al (2005).

Answer 23

1/3 clownfish settle within 2ha from birth site. Most settle within 100m.
Marine reserves benefit recruitment both inside + outside boundaries.

Question 24

Harrison et al (2012).

Answer 24

Patterns of larval dispersal on GBR.
83% coral trout + 55% stripy snapper offspring ended up on fished reefs.
Reserves = 28% local reef area, but produce half juvenile recruitment to fished reefs within 30km.
Marine reserves effective tool for sustaining future fishing.

Question 25

Cowen et al (2006).

Answer 25

Typical larval dispersal distance of reef fish = 10-100km.

But most data collected from species w/ short larval durations + dispersal distances.