PLESIOGAMY, A TERM CONTRASTING WITH HERKOGAMY

Guy L. Nesom

2925 Hartwood Drive

Fort Worth, Texas 76109

gu3nes0m@sbcgI0bal.net

ABSTRACT

Plesiogamy is proposed for use as the term referring to a close positioning of stigma and
anthers, which usually leads to autogamy. Herkogamy, the contrasting term, refers to a spatial
separation of the stigma and anthers, thus increasing the likelihood of outcrossing.

KEY WORDS: herkogamy and allogamy, plesiogamy and autogamy, dichogamy, synchronogamy

Herkogamy (Greek herkos, wall or fence, and gamos, marriage; Brown 1956) refers to a
spatial separation of the stigma and anthers, thus increasing the likelihood of outcrossing and
production of genetically variable offspring. In "approach herkogamy," the most common form of
herkogamy, the stigma is above the level of the anthers: in "reverse herkogamy" the stigma is below
the anthers.

No term appears to exist, however, in reference to the contrasting situation, where stamens
and stigma of a single flower are at the same level, in essentially the same position, thus making it
likely that self-pollination occurs. The term plesiogamy (Greek, plesios, near, alluding to the
proximity of the stamens and stigma) is proposed here for this arrangement and is used in several
studies dealing with the taxonomy of Mimulus sensu lato (e.g., Nesom 2012). Plesiomorphic refers to
an unspecialized condition (in contrast to plesiogamy, which usually is interpreted as a specialization),
but the word itself (Greek, plesios, near, morphe, form) intends to convey the sense of nearness to the
original morphological form, i.e., primitive.

Perhaps "non-herkogamy" would serve just as well as a contrasting term to herkogamy, but a
positive term (vs. one that simply negates the opposing condition) seems useful. We prefer electron
to "non-proton," past to "non-future," yang to "non-yin," etc, and the contrasting autogamy/allogamy
and chasmogamy/cleistogamy have long been in use.

Autogamy (self-pollination, from anthers to stigma of a single individual, commonly within
the same flower) is the mode implied by plesiogamous arrangment of anthers and stigma. Allogamy
(cross-pollination, pollination between flowers of different individuals; synonyms or near-synonyms
exogamy, xenogamy) is the usual mode of pollination and fertilization implied by herkogamous
' anthers and stigma.

Dichogamy (in plants) refers to a temporal separation of pollen shedding and stigma
receptivity. Protandry and protogyny describe conditions when anthers or stigmas mature first.
Apparently no contrasting term exists for dichogamy, and it's suggested that, if necessary or desirable,
synchronogamy (Greek, syn, same or together, chronos, time) could be used to indicate that pollen
shedding and stigma receptivity occur simultaneously.

To complete the brief survey of opposing "-gamy" terms, chasmogamy refers to the

condition in which corollas are open at anthesis, exposing the anthers and stigma and usually leading

Nesom: Plesiogamy and herkogamy 2

g. Cleistogamy refers to corollas that are closed at anthesis, strongly correlated, with
self-pollination.

Geitonogamy (Greek, geiton, neighbor) is another related term. It refers to the pollination —
by insects or by wind — of a flower with the pollen from another flower on the same plant. The
result of geitonogamy is genetically similar to autogamy.

ACKNOWLEDGEMENTS

Many thanks to Beryl Simpson. Steve Weller, and Michelle Dudash for helpful comments.

LITERATURE CITED

Brown, R.W. 1956. Composition of Scientific Words (rev. ed.). Smithsonian Institution Press,

Washington, DC.
Nesom, G.L. 2012. Taxonomy of Erythranthe sect. Simiola (Phrymaceae) in the USA and Mexico.

Phytoneuron 2012-40: 1-123.