An evolutionary lineage is a temporal series of populations, organisms, cells, or genes connected by a continuous line of descent from ancestor to descendant. Lineages are subsets of the evolutionary tree of life . Lineages are often determined by the techniques of molecular systematics .
6-501: The PACMAD clade (previously PACCMAD, PACCAD, or PACC) is one of two major lineages (or clades ) of the true grasses ( Poaceae ), regrouping six subfamilies and about 5700 species, more than half of all true grasses. Its sister group is the BOP clade . The PACMAD lineage is the only group within the grasses in which the C 4 photosynthesis pathway has evolved; studies have shown that this happened independently multiple times. The name of
12-519: A new distinct descendant clade. Just as a map is a scaled approximation of true geography , a phylogenetic tree is an approximation of the true complete evolutionary relationships. For example, in a full tree of life, the entire clade of animals can be collapsed to a single branch of the tree. However, this is merely a limitation of rendering space. In theory, a true and complete tree for all living organisms or for any DNA sequence could be generated. Nevertheless, phylogenies can sometimes appear in
18-440: A non-treelike form. Branches on the tree of life may grow together, a phenomenon called reticulation , which occurs due to different biological processes. Another process, introgression , occurs when hybrids between distinct lineages transfer novel genetic material through subsequent crossing. In other cases, hybrid speciation takes place when lineages hybridize to form a new, distinct lineage. Horizontal gene transfer, involving
24-623: Is a stub . You can help Misplaced Pages by expanding it . Lineage (evolution) Lineages are typically visualized as subsets of a phylogenetic tree . A lineage is a single line of descent or linear chain within the tree, while a clade is a (usually branched) monophyletic group, containing a single ancestor and all its descendants. Phylogenetic trees are typically created from DNA , RNA or protein sequence data. Apart from this, morphological differences and similarities have been, and still are used to create phylogenetic trees. Sequences from different individuals are collected and their similarity
30-480: Is quantified. Mathematical procedures are used to cluster individuals by similarity. Members of a species are considered to evolve as a single unit (or lineage) when they repeatedly share the same genes. The nodes would represent a split in lineage due to a breaking of genetic connections: when a single lineage is divided into two subsets, with the individuals not exchanging genes, they will accumulate differences in genes. If they do not fuse back again, it will create
36-761: The clade comes from the first initials of the included subfamilies Panicoideae , Arundinoideae , Chloridoideae , Micrairoideae , Aristidoideae , and Danthonioideae . It has no defined taxonomic rank but is used frequently because it refers to a well-defined monophyletic group with a distinct ecology. Phylogeny of the PACMAD clade, with photosynthetic pathways for each subfamily: Anomochlooideae Pharoideae Puelioideae BOP clade Aristidoideae C 3 & C 4 Panicoideae C 3 & C 4 Chloridoideae C 3 & C 4 Danthonioideae C 3 Arundinoideae C 3 Micrairoideae C 3 & C 4 This Poaceae article
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