Evolution

The process by which the genetic structure of populations changes over time.

Divergent evolution is the accumulation of differences between groups which can lead to the formation of new species.

Goldfields and Ahinahina (silversword) a highly evolved member of the composite family.

Evolution

Euphorbia and Astrophytum are only distantly related, but have independently converged on a very similar body form.

In convergent evolution, unrelated species become similar in appearance as they adapt to the same kind of environment.

Evolution

Characteristics derived from a common ancestor are termed homologous.

• similar in structure and embryonic • not necessarily similar in function.

Analogous or homoplasy includes convergent evolution.

Similar evolutionary pathways under similar environmental conditions = Similarity of structure in unrelated or distantly-related organisms

A. Equisetum (Division Sphenophyta). B. Casuarina (Division Anthophyta). One is a flowering tree and the other is a non-flowering plant with an apical spore-bearing cone (strobilus).

Coevolution:

describe cases where two (or more) species reciprocally affect each other’s evolution.

Happen when species have close ecological interactions with one another.

• Predator/prey and parasite/host • Competitive species • Mutualistic species

Exclusive “matches” between plants and insects

Evolution

Species = “Kind” Biological species concept (genetic isolation):

A group of organisms capable of interbreeding and producing fertile offspring of both genders, and separated from other such groups with which interbreeding does not normally happen

Morphology is important

Species concept

Morphological species A population or group of populations that differs morphologically from other populations

Heteromorphyc generations Sterile hybrids may become widespread if they are able to reproduce asexually Equisetum x ferressii

Some problems with the species concept

Iris

Platanus x hybrida A fertile hybrid from 2 species isolated for at least 50 million years

Some problems with the species concept

Developmental plasticity. However, through artificial selection Brasica oleracea has proven to be highly flexible and has been bred for its leaves, inflorescence, stalks, leaf buds and roots.

Artificial selection

Broccoli, kohlrabi, cabbage, collard greens, cauliflower, brussel sprouts and kale

Some problems with the species concept

Systematics: the study of biological diversity in an evolutionary context, including taxonomy and phylogenetics.

Taxonomy uses a hierarchical classification system

Linnaean (binomial) system of classification: genus and specific epithet = species name.

Pinus flexilis –Limber pine P. lambertiana – Sugar pine P. morrisonicola – Taiwan white pine P. monticola –Western white pine

- A named taxonomic unit at any level is called a taxon.

Diversity and its order

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Diversity and its order

Members of different taxon may be grouped into subgroups

Subkingdoms Subphylums or Subdivisions Subclass Suborder Subfamily Subgenus Subspecies Varieties*

Binomila name + var. Pinus elliottii var. elliottii Pinus elliottii var. densa

The International Code of Botanical Nomenclature (ICBN) is the set of rules and recommendations dealing with the formal botanical names that are given to plants.

• Only one correct name that is accepted worldwide • The value of a scientific name is that it is an identifier • Not necessarily of descriptive value • Not necessarily accurate

Diversity and its order

The ICBN • Plants • Blue-green algae • Fungi • Photosynthetic protistas and taxonomically • Related non-photosynthetic groups.

Different rules and codes for Fossils

Cultivated plants (International Code of Nomenclature for Cultivated Plants)

Diversity and its order

Diversity and its order

A botanical name is fixed to a taxon by a "type” usually deposited and preserved in a herbarium.

Names in Latin (or Greek)

Authority Navicula tripunctata (O.F. Müller) Bory 1822

Nomen conservandum, to avoid disadvantageous nomenclatural changes

• Family • Genus • Species

Phacelia nashiana = P. campanularia

Navicula tripunctata (O.F. Müller) Bory 1822

Modern phylogenetic systematics are based on cladistic analysis.

A phylogenetic diagram (tree) is also called a cladogram.

A clade is a group of organisms which consist of 1)  all the descendants of an ancestral organism 2)  the ancestor itself.

A B C D E F G H I

Systematics and cladistics

Monophyletic pertains to a taxon that is derived from a single ancestral species. only legitimate cladogram type!

Polyphyletic pertains to a taxon whose members were derived from two or more ancestors not common to all members.

Paraphyletic pertains to a taxon that excludes some members that share a common ancestor with members included in the taxon.

Systematics and cladistics

Systematics and cladistics

Possession of unique features that reflect a common evolutionary origin vs. widespread features present in the common ancestor and lost over the time in some of the members of the group.

Principle of parsimony

Adoption of the simplest assumption in the formulation of a theory or in the interpretation of data, especially in accordance with the rule of Ockham's razor.

Homology is preferred over analogy or homoplasy

A universal evolutionary tree. Ribosomal RNA

Nucleic acids: • Data for understanding evolutionary relationships

• Genes with different rates of change in different lineages

• Non-coding sequence used as neutral markers that reflect past evolutionary events

Serial endosymbiotic theory

Systematics uses diverse approaches:

Morphology Anatomy Palynology Microscopy Biochemistry Molecular Biology Genetics Physiology Ecology Evolution Bioinformatics

Systematics and cladistics Molecular data alone may not provide the most accurate account of phylogenetic relationships