Marine Biogeography

Question 1

Describe Marine biogeography

Answer 1

High diversity:
- Ecosystems, habitats, species, evolutionary histories, life histories, reproductive strategies
Adaptation is driven by horizontal and vertical clines

Light levels also affect primar productivity

Question 2

Describe global thermohaline circulation

Answer 2

Ocean conveyor belt. Oceans exchange water, driven by differences in temperature, salinity, density nd the turning of the earth.
Warm water rises, cold water sinks and very salty water has a higher density

Question 3

Describe marine biogeography and biological processes

Answer 3

Variety of biological processing influencing the distribution of marine species:
Evolutionary history - For example, fish species of the Central Indo-Pacific contain more species than any other ocean across all taxa

Question 4

Why is the Central Indo-Pacific so diverse?

Answer 4

Miller et al. (2018) used phylogenetic approaches and constructed hypotheses to make comparisons of the relative importance of colonization time, number of colonization events, and diversification rates (speciation minus extinction).
Estimated regional richness using distribution data for approximately 72% of all marine fishes and approximately 33% of all freshwater fishes.
The authors found that in CIP there were many, relatively old (5.3–34 m.y ago) colonizations that allowed greater time to accrue species richness (through in situ speciation) than in other regions.

Question 5

What other factors influence marine species distributions?

Answer 5

• Physiological limits
• Prey and predator distributions
• Species competition
• Dispersal ability
  Species richness decreases with increasing depth.
  Biological connectivity duration of larval phase increases with increasing depth

Question 6

Describe global species richness and hotspots across taxa

Answer 6

• 13 major species groups ranging from zooplankton to marine mammals
• Two patterns: Coastal species max diversity Western Pacific, oceanic groups peaked across broad mid-latitudinal areas of all oceans.
• Fundamental role of temperature or kinetic energy in structuring marine biodiversity

Question 7

Where is the largest migration on Earth?

Answer 7

The mesopelagic. Organisms migrate to deeper depths during the day.

Question 8

Describe marine mammals

Answer 8

• Polyphyletic group
• Species do not have a common ancestor
• Grouped due to convergent evolution leading to an aquatic lifestyle

Question 9

Describe cetaceans

Answer 9

• Arose circa 50 m.y.a. from terrestrial ancestors
• Currently the most dominant group of marine mammal in terms of taxonomic and ecological diversity and geographic range
• Inhabit both marine and freshwater ecosystems, ~ 86 species

Question 10

Describe mysticetes

Answer 10

Suborder Mysticeti (baleen whales or mysticetes) comprises ~ 14 species in four families, for example, humpback, right and blue whales

Question 11

Describe odontocetes

Answer 11

Suborder Odontoceti (toothed whales or odontocetes) comprises ~ 72 species in 10 families, for example sperm whales, dolphins, killer whales and beaked whales

Question 12

Why are cetaceans highly efficient top predators?

Answer 12

They are generalists and specialists

• Mysticetes and odontocetes – highly efficient top predators with two different adaptive foraging strategies,
• Mysticetes – enormous amounts of small prey by filtering,
• Odontocetes – biosonar to locate the vertically migrating mesopelagic, or other fish and mammals
• Ecologically important and efficient nutrient cyclers – moving nutrients within ocean basins

Question 13

Describe diversity of core habitats, life histories and behaviours

Answer 13

Key features – long life span, low fecundity and extended parental care and for some species, complex behaviour and social structures

Cetaceans include a diverse variety of habitats, social structures, foraging strategies and behaviours:

Question 14

Describe species or population specific features

Answer 14

• Sperm whales – social structures very different across populations,
• Killer whales – highly specialized ecotypes, mammal versus fish eaters, stark differences in dispersal,
• Pilot whales – different social structures in different populations.

Question 15

Describe the humpback whale

Answer 15

• Cosmopolitan distribution – breeds in tropical regions, feeds in polar regions,
• Generalist forager, small fish and krill, (some feeding during migration),
• mtDNA show highly structured populations / meta-populations, some overlap in feeding areas,
• Cultural transmission in song (males), cultural ‘memory’ of calving grounds

Question 16

Describe sperm whale

Answer 16

• Cosmopolitan distribution – females and immature distributed in lower latitudes, males in polar regions then migrate for breeding,
• Specialized deep divers –squid eaters (teuthivorous),
• Sophisticated multilevel social organization – matrilineal groups and vocal clans – ocean basin differences, cultural differences
• Low mtDNA diversity (rapid population expansion) with highly structured populations (female philopatry)
• Both geographic and social philopatry drive population structure

Question 17

Describe killer whales

Answer 17

Cosmopolitan distribution but specialized populations and ecotypes that overlap their ranges.

Different preferred prey species by ecotype (use slides)

Question 18

Describe stepping stone radiation

Answer 18

Phylogeographic study hypothesizes the radiation of Cephalorhynchus from South Africa, east to New Zealand (I), east to South America (II).

South American dolphin population moved northwards with glaciation of Tierra del Fuego to form the Chilean dolphin (IIIa) and Commerson’s dolphin (IIIb).

More recently Commerson’s dolphins founded a population at Kerguelen Islands (IVa).

Question 19

Describe Hector’s and Maui’s dolphins

Answer 19

• Hector’s, Cephalorhynchus hectori
• Maui’s, North Island sub-species Cephalorhynchus hectori maui
  Small, (~1.5 m) endemic dolphin of - - New Zealand,
• Low abundance,
• Highly fragmented populations with little migration,
• Reproductive isolation in Maui’s,
• Conservation priority as subject to the impact of human activities – mainly fisheries bycatch

Question 20

Describe beaked whales

Answer 20

• Offshore distribution, extremely deep-divers foraging on squid and small fish,
• Small body size, small group size,
• Elusive surface behaviour, few that are studied
• NZ Cetacean Tissue Archive – University of Auckland
• NZ very high diversity of cetaceans, 13 species beaked whales
• Second most common cetacean to strand, Gray’s beaked whale
• Multi-disciplinary methods to identify patterns of strandings, morphological variation, genetic population structure and kinship
• Genetic signature of high genetic diversity and large population size
• Long term stability in gene frequencies
• High levels of gene flow across study area (~6000 km from NZ to West Australia

Question 21

Give some general facts about Grey’s beaked whale from the research

Answer 21

• Social structure. Gray’s beaked whales that strand together are generally unrelated - both sexes disperse, sub-adults form affiliations with unrelated individuals
• No fathers were found within the groups, few mixed-sex groups
• Consistent with a ‘fission-fusion’ society as seen in some oceanic dolphins