Phylogeny
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What is a phylogeny?
Interpreting trees
Content of tree pages
How to search
Navigating trees
Glossary
 

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What is a phylogeny?

A phylogeny is a means of depicting evolutionary history using a tree. While Charles Darwin was not the first to depict evolutionary relationships using a tree, the notion of an evolutionary tree played a central role in the development of his theory on the origin of species.

Darwin was an astute observer of nature. Darwin was astonished by individual differences observed in nature that not all individual were cast in the same mould. Without understanding the precise mechanism of inheritance, Darwin none-the-less believed that at least some traits were passed from one generation to the next. Darwin thought that that some of these traits enhanced the fitness of those individuals that had inherited the trait. He noted that more species had existed in the past than at the present, hence he postulated a struggle for existence; some species went extinct while others flourished and adapted. Darwin believed the pattern of descent with modification brought about by the process of natural selection could explain the grouping of all organic beings.

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Interpreting the trees

The branching patterns seen in a phylogenetic tree represent lineages that have diverged through time. The point at which two branches diverge represent a speciation event and is called a node, and the distances between nodes are called internodes or edges. The tips of branches, also called terminal nodes, represent the extant taxa in the tree. In a fully dichotomously branched tree each node has two descendants, whereas a node that has more than two descendents is termed a polytomy and generally reflects uncertainty about relationships. A tree is rooted if it has a node that is designated as the root. The branches at the bottom of a rooted tree are the first lineages to diverge and hence represent the oldest branches, while branches at the top of the tree represent more recently diverged lineages. The tips of branches are also called terminal nodes and represent the extant taxa found in the tree. The trees in this site have been oriented, so that the oldest branches are found on the bottom of the page with the tips to the right side of the page.

The indigenous species in the trees are indicated with bold green text whereas the exotic species are coloured brown.

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Content of the tree pages

Breascrumbs Root of tree Nga Tipu link

Breadcrumbs

  Show the seqeunce of trees back from the current tree back to the root tree

Ngā Tipu link Nga Tipu link icon

Indicates that there is a link to Nga Tipu o Aotearoa - New Zealand Plants.  Clicking on the link will open a new window showing the details for the taxon, including information on the distibution, other images, Mäori and vernacular names, and scientific literature.

Root of tree

 Provides a link to the previous tree.

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Glossary

abaxial
the side away from the axis; compare with adaxial

adaxial
the side towards the axis, compare with abaxial.

annulus
line of thick-walled cells along one side of a fern sporangium that aids in the dispersal of spores

caespitose
growing in dense tuffs

clade
a monophyletic group comprising a common ancestor and all of its descendants

classification
systematic arrangement into divisions or groups

Cretaceous
Period extending from 65 to 144.2 million years ago; the age of dinosaurs

disjunct
occurring in widely separated geographic areas

endemic
A species that is restricted to a certain region.

exotic
a species that has been introduced and naturalized

gametophyte
haploid gamete producing generation of the plant reproductive cycle.

indigenous
naturally occurring species

indusium
thin epidemal outgrowth from a fern leaf that covers a sorus

inferior ovary
with floral whorls arising above the overy

internode
The space along a branch between nodes. Also known as an edge.

monad
a single individual

monophyletic
A single evolutionary lineage or branch that includes a common ancestor and all of its descendants. A discrete branch in an evolutionary tree. Compare with paraphyletic and polyphyletic.

neotropics
new world tropics in Central and South America

node
The point at which two branches diverge. A speciation event. Paraphyletic. A single evolutionary lineage that includes a common ancestor and some of its descendants. Part of an evolutionary branch. Compare with monophyletic and polyphyletic Phylogenetic tree. A tree that depicts the branching pattern of lineages diverging through time. Phylogeny. Inference of evolutionary history.

paleotropical
old world tropics in Africa and Asia

panicle
branched inflorescence consisting of a number of racemes

pantropical
widely distributed in tropical regions

paraphyletic
A taxonomic group that includes a common ancestor of some its descendants.

Permian
age of amphibians extending from about 280 to 230 million years ago

phloem
food conducting tissue in vascular plants

phytomelan
dark plant pigment

polyphyletic
A taxonomic group consisting of two or more evolutionary lineages that lack a common ancestor so are not directly related by descent. Two or more unrelated evolutionary branches. Compare with monophyletic and paraphyletic.

protostele
stele with a solid core of vascular tissue, lacking a pith

raceme
unbranched inflorescence with flowers borne along the length of a central axis

reticulate evolution
Netlike rather than tree-like pattern of evolutionary branching. A reticulate pattern of evolution can result from hybridization or lateral gene transfer.

rhizomatous
spreading by underground stems

rhizome
horizontal underground stem

root
ancestral node of a tree

root parasites
Parasites whose roots penetrate and draw nutrients from the roots of another plant.

silica bodies
containing silicon

sisters
The most recent descendants of a common ancestor.

sori
cluster of sporangia on the lower surface of a fern leaf

sporangium
a spore-bearing case or sac

spore
reproductive cell resulting from a meiotic division in a sporangium; the first cell of the gametophyte generation.

stele
the primary conducting tissue in a plant root or stem

stolon
stem creeping along ground, rooting at the nodes and giving rise to a new plant

successive microsporogenesis
Formation of pollen grains in which each mieotic division i is followed by cell wall formation. Characteristic of many monocots.

superior ovary
floral whorls attached below the ovary

synonomy
scientific names used in different nomenclatural systems to designate the same taxon

temperate
the region north of the Tropic of Cancer and south of the arctic circle and south of the Tropic of Capricorn and north of the antarctic circle

tetrad
a group of four

thrysoid
a compact, cylyndrical, or ovate panicle with an indeterminant axis and cymose subaxes

thyrse
a compact, cylyndrical branched inflorescence with an indeterminant axis and cymose subaxes

tips
Represent the extant taxa in a tree. Also called terminal nodes

umbel
inflorescence in which the pedicels arise from the same point

UTC Clade
The UTC clade is one of the two major lineages of green organisms (the other being streptophytes, = embryophytes + charophyceans).

xylem
water conducting tissue in vascular plants

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