The first time a character changes state on a tree, this state change is given the weight'1'; subsequent changes are less'expensive'and are given smaller weights as the characters tendency for homoplasy becomes more apparent.
42.
If a bird, bat, and a winged insect were scored for the character, " presence of wings ", a homoplasy would be introduced into the dataset, and this could potentially confound the analysis, possibly resulting in a false hypothesis of relationships.
43.
Proboscidea and Sirenia are linked together based on auditory characters in their petrosal bones, but this link may be a homoplasy . ( The Early Eocene family Anthracobunidae has been considered to be a sister group of Tethytheria, but has more recently been assigned to Perissodactyla .)
44.
Therefore, it is often the case that researchers are forced to compromise by developing trees that simply try to minimize homoplasy, finding a maximum-cardinality set of compatible characters, or constructing phylogenies that match as closely as possible to the partitions implied by the characters.
45.
It may still be, however, that the intelligent behaviour is a homoplasy that evolved several times in the " Egernia " genus-group; the fact that " Corucia " is a monotypic and rather distinct genus makes it impossible to decide at present.
46.
In combination, the low incidence of homoplasy together with a clear character polarity make retrotransposon integration markers ideal tools for determining the common ancestry of taxa by a shared systematic biology of mammals depends on the availability of retrotransposons that were actively integrating before the divergence of a particular species.
47.
It can be difficult to decide whether a character state is in fact the same and thus can be classified as a synapomorphy, which may identify a monophyletic group, or whether it only appears to be the same and is thus a homoplasy, which cannot identify such a group.
48.
Construction of phylogenies under the SMM is, however, complicated by the fact that it is possible to either gain or lose a repeat unit, thus alleles that are identical in size are not necessarily identical by descent ( i . e . they show marker-size homoplasy ).
49.
Studies have suggested the lack of a fully resolved hypothesis for the relationships within the family is due to a variety of factors, including difficulties in selecting appropriate outgroups, homoplasy in morphological character states, slow rates of molecular evolution important for the use of standard DNA markers, and character polarization.
50.
Besides reflecting the amount of homoplasy, the metric also reflects the number of taxa in the dataset, ( to a lesser extent ) the number of characters in a dataset, the degree to which each character carries phylogenetic information, and the fashion in which additive characters are coded, rendering it unfit for purpose.
