Search

Seventeen species of Parahebe are recognised for New Zealand, an increase of six from the most recent Flora treatment. The new species result from division of P. catarractae sens. lat. into P. catarractae (now confined to Fiordland), P. martinii (Marlborough), and P. lanceolata (North Island and North‐West Nelson); two new species (P. senex in North‐West Nelson and P. spectabilis in the Takitimu Range); and acceptance of P. brevistylis and P. laxa at species rank. We also describe two subspecies in P. cheesemanii: subsp. cheesemanii from Nelson and subsp. flabellata from Arthur's Pass. Species limits are discussed in terms of morphological and flavonoid evidence, and some limited data on natural and artificial hybrids are also presented. Problems of the generic limits in the Veroniceae are discussed in relation to Parahebe. Parahebe appears to be paraphyletic and future changes in nomenclature are likely. This treatment covers the New Zealand plants treated as Parahebe in recent Floras.

The frequent occurrence of gender dimorphism has long been recognised as one of the distinctive features of the New Zealand flora. We list 83 seed plant genera in which gender dimorphism occurs, and document habit, pollination, and dispersal characters for each genus. This means that gender dimorphism is represented in 23% of the genera in the flora; however, not all of these genera are uniformly dimorphic in gender—40% of them include some species or populations that lack gender dimorphism. We estimate that gender dimorphism has arisen autochthonously in 17 of the 83 genera— therefore, gender dimorphism evolved elsewhere in most cases (80%), and was established in New Zealand by subsequent migration. A comparison of the genera in which gender dimorphism occurs with the remainder of the flora shows that gender dimorphism is strongly correlated with fleshy fruits, and with woody habits. No correlation was found between gender dimorphism and pollination mode, perhaps because relatively unspecialise...

Inbreeding depression caused by self-fertilisation was examined in the gynodioecious shrub Hebe subalpina under two planting regimens, non-competitive and competitive. We found differences among families in the magnitude of inbreeding depression, ranging from 0.31 to 0.63. On average, outcrossed progeny grew nearly twice as large as selfed progeny, and the coefficients of variation (CVs) for dry mass were lower for outcrossed progeny than selfed progeny within the non-competitive regimen. Planting regime had a highly significant effect on dry mass, such that plants grown in the competitive regimen were an order of magnitude smaller than those in the non-competitive regimen, and they also had higher CVs. However, planting regimen did not significantly affect the magnitude of inbreeding depression. Our results suggest that intrinsic differences exist in the growth rate of selfed and outcrossed individuals, and that inbreeding depression helps to maintain females at a high frequency in the populatio...

Dichogamy is the separation of the presentation of pollen and stigmas in time within a plant. It is a common but neglected feature of outcrossing angiosperms. Dichogamy has been almost universally interpreted as an outcrossing mechanism, but many dichogamous species are also self-incompatible (and sometimes also herkogamous and/or with unisexual flowers). In outcrossing species, there is almost invariably a clash between selection to place pollen and stigmas in similar positions for effective pollination and selection to keep the androecia and gynoecia apart to avoid interference between them. We suggest that the separation of pollen and stigmas acts in general to reduce this self-interference and it often also reduces self-fertilisation. Mechanisms preventing self-fertilisation primarily increase maternal fitness, whereas mechanisms avoiding self-interference primarily promote paternal fitness. Five independent ways of subdividing dichogamy are recognised: protandry or protogyny; intrafloral or ...

The flowering and fruiting of Melicytus lanceolatus, M. ramiflorus, and M. micranthus are described. The three species show striking contrasts. M. lanceolatus flowers in early spring and the plants flower profusely and synchronously over several weeks. M. ramiflorus flowers over the late spring and summer in a series of distinct episodes. This pattern was observed in three flowering seasons and at several localities in New Zealand. The number of flowering episodes per season varies between plants, localities, and seasons. Flower production varies with the age of wood on which the flowers are produced and between flowering episodes. Fruits may be produced in any episode and are present in large numbers through late summer and autumn. M. micranthus has an extended flowering season from spring until autumn. The plants flower asynchronously and produce a few flowers at a time over a long period. Fruit are also present in low numbers over a long period (summer, autumn, and winter). Factors which may b...

The gender of plants of populations of two New Zealand montane shrub species during two flowering seasons is described: Discaria toumatou has hermaphrodite flowers and Leptospermum scoparium is andromonoecious. Individuals in such species that are monomorphic for their sexual type are often considered to behave equally as pollen and ovule parents in sexual reproduction. Counts of the numbers of pollen- and fruit-bearing flowers on a sample of plants demonstrate, however, that in one season individuals within each population span the range from exclusively pollen- to predominantly ovule-contributors in functional gender (the proportions of genes that are likely to be transmitted through pollen and ovules, based on parental investments). The distribution of gender within a population changes somewhat between years but is basically consistent. Gender in successive years is not correlated among individuals within a population, indicating that the environment influences femaleness. Femaleness is not c...

Plants of Cotula section Leptinella have evolved a prostrate habit from suberect ancestors. Seedlings establish the prostrate habit after several crowded leaves have been produced; an inflorescence is initiated and horizontal branches with long internodes grow out from the flowering node and several nodes immediately behind it. Cotula featherstonii has secondarily evolved an erect woody habit; seedlings produce long internodes on the pnmary axis without flowering and stems remain erect. Many other genera in New Zealand have evolved a reduced stature, in some instances including prostrate habits. The reverse direction of evolution towards increased stature and woodiness has probably occurred less frequently. In this respect, New Zealand may be exceptional among isolated islands because of its continental origin and the relatively recent appearance of xeric and montane conditions favouring reduced stature.

Gender (maleness or femaleness) is a quantitative phenomenon in plants. For accurate descriptions of gender, numerical estimates of the relative capabilities of plants as pollen and ovule parents have advantages over the verbal morphological descriptions of gender that are traditionally used. Full descriptions require the distribution of gender among subsets of a sexual class (e.g., among individual plants) to be indicated as well as the average condition. Estimates of gender can be based on the pollen and ovule or seed production of each subset independently (phenotypic gender), or else the pollen and ovule or seed production of the whole population can be taken into account to assess the functional gender of any subset. The functional gender of a plant estimates the proportions of its genes which are transmitted through pollen (its maleness) or through ovules (its femaleness). Prospective estimates of functional gender are based on the relative maternal and paternal investments before anthesis ...

Sex ratios are reported for 53 populations of species of Gingidia, Scandia, Lignocarpa , Anisotome, and Aciphylla (Umbelliferae, Apioideae). In 43 populations there is a significant preponderance of male plants; in 6 populations the sexes are approximately equally common, and in 4 no females were found. The ratio (male/female) of the average number of inflorescences per plant is significantly correlated with the average number of inflorescences per plant (male and female averages combined) in dioecious but not in gynodioecious species. This result indicates that populations with higher average inflorescence numbers per plant are able to use inflorescence number as part of sex differential strategies for optimally deploying reprodutive effort. The results are consistent with a hypothesis of greater cost of reproduction to females than to males, resulting in differential longevity of the sexes.

In investigations of the reproductive biology of New Zealand plants, breeding systems have received much attention but there has been little work on pollination and still less on seed biology. New Zealand plants, in general, have flowers that lack bright colours, are of small size, and have simple unspecialised structures. Dish and (especially at higher altitudes) tube blossoms abound, whereas bell, brush, gullet, and flag blossoms are relatively uncommon. There is an unusually high frequency (c. 18 per cent) of genera with separate sexes. New Zealand has few specialised pollinators. The unspecialised flowers are interpreted as adaptations to fluctuating combinations of promiscuous pollinators. The high frequency of separate sexes is associated with unspecialised pollinators and fleshy bird-dispersed fruits. A number of larger genera show considerable evolution of flower structure accompanying respecialisation to different pollinators. The occurrence of conspicuous floral displays on certain outl...

Summary The taxonomic position, status, and characters of Cotula, and its subdivision into three sections are briefly described. Section Leptinella is considered a well-defined taxon and its characters and relationships are discussed. Twenty-five species from New Zealand, the Subantarctic islands, and South America are described and classified into two series, Elongata and Radiata. The following new taxa and names are described: series Oligoleima (from Australia and New Guinea), Elongata and Radiata; five new species, C. dispersa, C. serrulata, C. calcarea, C. intermedia, and C. nana; two new names, C. albida and C. membranacea; five new combinations, C. rotundata, C. traillii subsp. pulchella, C. pectinata subsp. villosa, C. pectinata subsp. willcoxii, and C. pyrethrifolia var. linearifolia; four new subspecies, C. dispersa subsp. rupestris, C. dioica subsp. monoica, C. squalida subsp. mediana, and C. atrata subsp. luteola.

Ten patches of turf containing Coprosma pumila were collected from Macquarie Island during the 1977–78 flowering season. Three.patches contained only male flowers three patches contained only female flowers and fruIt, and four patches had male flowers' and also female flowers and/or fruit. Single branches from all patches were invariably unisexual. C. pumila is considered to be dioecious on Macquarie Island, rather than monoecious as previously reported.