Systematics & Classification

MARE 390Dr. Turner

Systematics & Classification

Systematics - Study of biological diversity

Phylogeny – evolutionary history of a particular group of animals

Why study?Framework for interpreting biological diversity

Terms & Concepts

Ancestral – preexisting character; primitive

Derived – new character stateancestral – locomotion with hind limbsderived – locomotion with body/tail

Derived characters are used to link groups – specifically monophyletic groups

Terms & Concepts

Monophyletic – a group of taxa that consist of a common ancestor plus all descendants of that ancestor

Paraphyletic and polyphyletic – include a common ancestor and some descendants

Terms & Concepts

Paraphyletic - group contains the most recent common ancestor but does not include all the descendants of this common ancestor e.g. - class Reptilia is paraphyletic because that class does not include birds (class Aves), which are descended from reptiles

Polyphyletic - does not contain the most recent common ancestor of all its members e.g. - homoetherms are polyphyletic - contain both mammals and birds, but the most recent common ancestor of mammals and birds were piokilotherms

Terms & Concepts

Diphyletic - a taxonomic group of organisms derived from two separate ancestral lines

now replaced by poly & para e.g. – pinnipeds mono or diphyletic

Cladogram – a branching diagram that conceptually represents the best estimate of phylogeny

Terms & Concepts

Homology – similarity of features resulting from common ancestry

Homoplasy – similarity not due to homology; (analogous) structures that are the result of convergent evolution or reversal Convergent (parallel) – independent evolution of a similar feature in 2 or more lineages Reversal – loss of a derived feature coupled with establishment of ancestral

Who did the what now?

Homology

Walrus Elephant seal

Common ancestor had flippers

Who did the what now?

Homoplasy - convergent

Bottlenose dolphin Elephant seal

Common ancestor lacked flippers

Who did the what now?

Homoplasy - reversal

Harp seal Elephant seal

Claws not in ancestral phocids but in terrestrial arctoid carnivores

How to do – that thing you do

Cladograms are constructed by:1. Naming and defining all taxa in group2. Select/define characters for each taxon3. Arrange characters4. Determine whether each character is ancestral or derived5. Construct all possible cladograms by grouping taxa based upon common shared derived characters

Testing Phylogenetic Hypotheses

Parsimony - least complex explanation for an observation

Maximum parsimony - the preferred phylogenetic tree is the tree that requires the least number of evolutionary changes

Testing Phylogenetic Hypotheses

Taxonomy & Classification

Taxonomy – the description, identification, and classification of species

Within past 10 years:2 beaked whales described; 1 resurrectedNew dolphin species described3 forms (subspecies) of Orcinus orcaNew species of balaenopterid described

Australian Snubfin Dolphin (Orcaella heinsohni)

Pygmy beaked whale(Mesoplodon peruvianus)

Pygmy Bryde's Whale (Eden's Whale)

Balaenoptera edeni

Omura’s Whale Balaenoptera omurai

Resident Transient

Offshore

Orcinus orca subspecies?

Evolutionary Biogeography

Biogeography – study of geographic distribution of organisms (past & present)

Patterns in distributions of taxonomic groups/species and interprets aspects of both ecology & evolution

1. How did species occupy present range?2. What geologic events shaped distribution?3. How are regional species related?

Ecological Factors

Several adaptations to the ocean

Buoyancy – seawaterFriction resistance to swimmingPoor light transmissionOsmotic challenges – hyperosmotic Heat loss to waterWater temperaturesPrimary productivity

spatial & temporal variation

Temperature & Sea Ice

Marine mammals in contact with cold water

Heat capacity of water 25X air

Sea ice very important to marine mammals

Fast ice – attached to land; Weddell, elephant

Pack ice – free floating; walrus, Steller’s, harp

Primary Productivity

Availability of food established by:1. Pattern of primary production2. Number of trophic levels between 1° producer and marine mammals consumer

Sirenians – directly on 1° productionMysticetes – few trophic levelsOdontocetes & pinnipeds – 5+ levels

Particle Size & Biomass

Seasonal Patterns in 1° Production

Variation in Ocean Production

Water temperature & food resources vary

UpwellingENSO – El Nino-Southern OscillationNAO – North Atlantic Oscillation

Present Patterns of Distribution

Two major patters:1. Cosmopolitan – wide distributions; inhabiting most of the world’s oceans e.g. – common dolphin, harbor seal

2. Disjunct – species pair distribution separated by a geographic barrier e.g. - walrus

Present Patterns of Distribution

Endemic – confined to a particular geographic region e.g. – Hawaiian monk seal

Circumpolar – having distribution around the poles e.g. – narwhal & beluga

Antitropical – species pair – one in northern one in southen hemisphere e.g. N & S right whale dolphin

Past Patterns of Distribution

Past arrangements of continents & ocean basins have affected the distribution of marine mammals

Corridor – route that permits spread from one region to another

Barriers to dispersal: physical (continents), climactic (equator), biotic (low productivity)

Events Affecting Distribution

1- Early cetaceans 2- Early sirenians

Continents in Early Eocene

Continents in Early Miocene(20mya)

1- Early pinnipeds 4- Early pinnipeds

Continents in Middle Miocene(12mya)

1- Early phocids, 2 – Monachines & Odobenids, 3-4 - Phocines