Long branch attraction

In phylogenetics, long branch attraction (LBA) is a form of systematic error whereby distantly related lineages are incorrectly inferred to be closely related. LBA arises when the amount of molecular or morphological change accumulated within a lineage is sufficient to cause that lineage to appear similar (thus closely related) to another long-branched lineage, solely because they have both undergone a large amount of change, rather than because they are related by descent. Such bias is more common when the overall divergence of some taxa results in long branches within a phylogeny. Long-branches are often attracted to the base of a phylogenetic tree, because the lineage included to represent an outgroup is often also long-branched. The frequency of true LBA is unclear and often debated. Although often viewed as a failing of parsimony-based methodology, LBA can result from a variety of scenarios and be inferred under multiple analysis paradigms.

Causes

LBA was first recognized as problematic when analyzing discrete morpological character sets under parsimony criteria, however Maximum Likelihood analyses of DNA or protein sequences are also susceptible. A simple hypothetical example can be found in Felsenstein 1978 where it is demonstrated that for certain unknown "true" trees, some methods can show bias for grouping long branches, ultimately resulting in the inference of a false sister relationship. Often this is because convergent evolution of one or more characters included in the analysis has occurred in multiple taxa. Although they were derived independently, these shared traits can be misinterpreted in the analysis as being shared due to common ancestry.

501 Queen

The 501 Queen is an east-west streetcar route in Toronto, Ontario, Canada, operated by the Toronto Transit Commission (TTC). At 24.8 kilometres (15.4 mi), it is the TTC's longest surface route, the longest streetcar route operating in North America and one of the longest streetcar routes operating in the world. It stretches from Long Branch Loop (just west of Browns Line, adjacent to Long Branch GO Station) in the west to Neville Park Loop (just west of Victoria Park Avenue) in the east, running on Lake Shore Boulevard, in a reserved right-of-way at the median of The Queensway, and on Queen Street. The route was instituted in the mid-to-late-19th century by private operators as a horse-drawn line, was later electrified, and was assumed by the TTC upon its creation in 1921. Service is provided 24 hours a day, though the route number changes to 301 Queen late at night.

The 501 Queen is regularly operated with the TTC's double-length ALRVs between Neville Park and Humber and CLRVs from Neville Park to Long Branch. It runs every five to nine minutes between Neville Park and Humber, ten minutes from Humber to Long Branch, and 10 to 30 overnight from approximately 1:00 a.m. until 5:00 a.m. The route connects with Line 1: Yonge-University as part of the TTC's subway system at Queen and Osgoode stations.

Long Branch

Long Branch may refer to:

In geography:

In transportation:

In other fields: