Classification, evolution, and phylogeny of the families of Monocotyledons / Aaron Goldberg

Object Details

Summary

To some extent classification is subjective. Taxonomists differ in the relative importance they ascribe to particular characters and in the degree of difference between related taxa they deem sufficient to constitute family or ordinal rank. About 250 monocot family names have been published. Those who have attempted an overview of the system at the family level and above in the last quarter century recognize between 45 and 103 monocot families in 14 to 38 orders. I accept 57 families in 18 orders. In Table 1 I give my ordinal allocation of the families and that of 11 recent authors to indicate where there is agreement and where there are differences to be resolved. I have constructed a dendrogram to suggest relationships and degree of advancement of the orders.I have written concise, uniform descriptions of all the families of monocots emphasizing those characters that show trends between families or occur in more than one family. Each family is illustrated by analytical drawings of the flower, fruit, seed, and usually inflorescence. Several species are usually used to show the range of major variation within families and trends toward related families.Monocots and dicots have existed concurrently for most of their history, have been subjected to many of the same ecological pressures, and consequently show similar evolutionary trends. My approach to understanding evolutionary trends in characters is to relate them to the ecological factors that might be responsible for them by their selective action. The monocots probably originated under warm temperate or subtropical conditions favorable for growth. A major evolutionary trend in them has been the gradual development of characters and character states enabling them to cope with dry and hot or cold conditions and colonize generally unfavorable habitats.A second major trend has been progressively greater specialization for insect pollination. The primitive monocots have flowers with numerous spirally arranged parts; those having flowers with few, opposite or whorled parts are derived.The floral organs are homologous with leaves. Like leaves the parts were initially separate. The connate and adnate conditions are derived.General character states are primitive; specialized states are derived. In attempting to determine which primitive states are most primitive I considered their occurrence among the families. The fewer the families with a particular primitive state, the more primitive the state. This is important in deciding whether a family is low or high on the family tree and the position within its particular order.In accordance with the above rationale, I have constructed a table giving the primitive and derived states for about 85 characters. I also indicate the extent to which I consider the states reversible.To determine a family's phylogeny, it must be compared with other families considered to be close to it. In general, the more characters and character states in common, particularly uncommon ones, the more likely are the subject families to be related. All parts of the plant and many characters should be considered. If a family has more than one state of a character, the state considered primitive for the particular family should be used in attempting to determine the extant family closest to its ancestor. A descendant has at least one more derived character or character state than its ancestor.

Data Source

Smithsonian Libraries

Date

1989

Call number

QK495.A14 G618 1989

Author

Goldberg, Aaron

Type

Classification

Physical description

iii, 74 p. : ill. ; 28 cm

Topic

Monocotyledons

Monocotyledons--Evolution

Monocotyledons--Phylogeny

Record ID

siris_sil_461597

Usage

CC0