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?
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
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)
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
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)