Reproductive Biology in Relation to Systematics

Abstract

Summary Many of the diverse floral characteristics used by taxonomists in assessing relationships among taxa represent adaptations to specific pollinators or pollinating methods. Therefore, the diversity of reproductive methods that occurs within a phylad has a strong influence on the number of taxa that are generally recognized in the phylad. Such evolutionary phenomena as convergence and adaptive radiation of floral patterns influence the taxonomic status of various phylads or the relationships that are seen among them. Incompatibility systems are generally unassociated with morphological distinctions, but are of practical importance in crossing programs designed to test the presence and nature of genetic isolation between species, since an unawareness of their existence may lead to erroneous taxonomic conclusions. Similarly, unilateral incompatibility is discussed in relation to certain practicalities in hybridization programs. Morphological features associated with dioecism and heterostyly are disscussed as a generally overlooked source of potentially very useful taxonomic characters. The importance of adaptations to different pollinators as a basis of interspecific isolating mechanisms is stressed, as are the possible positive evolutionary (and taxonomic) consequences of a breakdown in this isolation. Floral and other characters associated with autogamy are discussed and examples are given where the relationships of autogamous taxa are uncertain because of their highly specialized reduced flowers. It is suggested that taxonomists should make an attempt to understand the reproductive methods of the plants with which they work, since such an understanding will strengthen the foundation upon which taxonomic judgments are made.

Two New Genera of Podostemaceae from the State of Minas Gerais, Brazil

“…Our analyses failed to support the sectional classification of van Royen (1951) , perhaps due to evolutionary lability in anther dehiscence, which in other plants often correlates with the breeding system (i.e. introrse dehiscence with autogamy and extrorse dehiscence with xenogamy; Ornduff 1969 ). The resolution of Apinagia s. s. in our analysis (clade C) supports the monophyly of section Apinagia as defined by Tulasne (1849Tulasne ( , 1852, but not as modified by van Royen (1951) .…”

THE EVOLUTION OF SELF‐POLLINATION IN GRANITE OUTCROP SPECIES OF ARENARIA (CARYOPHYLLACEAE). I. MORPHOLOGICAL CORRELATES

“…I). The chief morphological differences used to separate the two taxa are associated with the flowers, and all are consistent with those characters typically correlated with a shift to autogamy (Ornduff, 1969). Populations from a given site are relatively uniform in their morphology.…”

“…The only character that fails to vary in the predicted manner is the number ofovules per ovary. Most selfers show a reduction in ovule number compared to their outcrossing relatives (Ornduff, 1969). In A. uniflora, however, the pattern is complex and not clearly related to variation in the breeding system.…”

Genetics of sex allocation in Mimulus (Scrophulariaceae)

“…Several other studies have reported that per flower production of both pollen and ovules is reduced in selfers compared to related outcrossing taxa, suggesting a positive correlation between the two traits, e.g. Eichhornia (Barrett, 1985) and unreported taxa (Ornduff, 1969). However, both Lloyd (1965) and Wyatt (1984) reported no consistent differences in ovule production between outcrossing and selfing taxa of Leavenworthia and Arenaria, respectively, although pollen production was lower in the selfers.…”