The reproductive biology of Sophora fernandeziana (Leguminosae), a vulnerable endemic species from Isla Robinson Crusoe

Sophora fernandeziana is the only legume endemic to Isla Robinson Crusoe (Archipelago Juan Fernández, Chile); it is uncommon and becoming rare. Although its preservation status is listed as "vulnerable," as with many species, little is known of its reproductive biology. Flowering phenology, floral morphology, nectar features, breeding system, and visitors were analyzed in two populations. Flowering is from late winter to early spring. Flowers last 6 d and have a number of ornithophilous features. A floral nectary begins to secrete highly concentrated nectar 48 h after flowers open. Nectar secretion increases as the flower ages but culminates in active nectar reabsorption as the flower senesces. Nectar production is negatively affected by nectar removal. Self-pollen germinates and tubes grow down the style. However, pollen tubes were only observed to enter the ovaries in open pollinated styles, suggesting the possibility of an ovarian self-incompatibility mechanism. Both sexes of the two hummingbird species that inhabit the island are regular visitors. Low fruit and seed set, low genetic diversity, and a shrinking number of populations all contribute to increased concern about the future of this species-and perhaps the hummingbirds that depend on it.     

The reproductive biology of Cybistax antisyphilitica (Bignoniaceae), a characteristic tree of the South American savannah-like “Cerrado” vegetation

Bignoniaceous woody species are very important ecological components of neotropical forests, but the reproductive biology of many species, such as Cybistax antisyphilitica, remains virtually unknown. Most species of Bignoniaceae are characteristically self-sterile, despite typically exhibiting normal pollen tube growth throughout the style, combined with slow rates of ovule penetration, fertilisation and endosperm initiation in selfed pistils. Uniform abortion occurs within a few days of anthesis, indicating the occurrence of late-acting self-incompatibility (LSI). However, breeding system studies have been performed in fewer than 7% of species, and other types of breeding systems (e.g., self-compatibility and apomixis) have been reported in this family. In the present study, the reproductive biology of C. antisyphilitica was investigated by field observation of flower visitors and floral events. Moreover, reproductive biology of this species was examined through experimental pollinations, analyses of pollen tube growth and ovule penetration using fluorescence microscopy, verification of pistil longevity, and a histological analysis of unpollinated vs. self-pollinated pistils. Finally, morphological aspects, quantities and germination were investigated in seeds that resulted from different pollination treatments. Natural pollination was effected by large- and medium-sized bees, and their visiting behaviour favours a high proportion of geitonogamy and no pollen limitation. Self-pollinated flowers produced no fruits, and all of the characteristic post-pollination events cited above were verified, witnessing the occurrence of LSI with post-zygotic rejection of selfed pistils in C. antisyphilitica. Although some indications of extended pistil longevity were found in selfed pistils, this feature seemed to be affected by unidentified environmental factors. The seeds were always monoembryonic and with high viability. A larger variation in the number of viable seeds was found in fruits derived from natural pollination. A low fruit set was observed after both natural and cross-pollination, and most crossed fruits underwent abortion at several points during the juvenile phase, even when protected against herbivory. The formation of surplus flowers/juvenile fruits and the apparently wasteful selfing mechanism control implied in LSI are discussed in the context of the perennial life style of tropical woody plant species.     

Ovariolar dimorphism and repagula formation in some South American Ascalaphidae (Neuroptera)

An account is given of the occurrence, in six genera of Ascalaphidae, of two distinct forms of ovariole, and the production of repagula by the modified form is described.     

Population biology of Senecio integrifolius (Compositae), a rare plant in Sweden

In a study of natural populations of Senecio integrifolius in southern Sweden (1979–1983) seeds were found to disperse from mid-June to late July and most of them germinated in autumn. No soil seed bank was observed. On a heavily grazed site few seeds were produced but the percentage of estimated germination was high (c. 75%). In two moderately grazed habitats 8–10% of the estimated number of seeds produced in permanent plots germinated. In a lightly grazed habitat many seeds were produced but only a small percentage germinated (1.4%). In field experiments the average germination was 50–53% when newly harvested seeds were sown where the vegetation had been removed, and 20–33% when sown in undisturbed vegetation at a moderately grazed site. Germination was much lower in a lightly grazed habitat (3–12%). Survival of seedlings was much higher in heavily and moderately grazed habitats than in lightly grazed habitats. Mortality tended to be higher during the growing season (mid-April to early November) than during the winter, and increased markedly during a drought period in the summer of 1982. The half-life of plants established in 1980 varied from 39.3 years at the most intensively grazed site to 7.2 at the lightly grazed site. The number of flowering stems varied between years mainly according to weather. Few plants in the permanent plots flowered every year, the flowering being most frequent at heavily grazed sites. It is concluded that heavy grazing by cattle after seed dispersal is the appropriate management for maintaining S. integrifolius in Sweden.     

Karyotype analysis and chromosome evolution in South American species of Lathyrus (Leguminosae)

The karyotypes of 10 species and one variety of South American Lathyrus were determined and compared with those obtained of five entities from the Northern Hemisphere. Although all the species have a chromosome number of 2n = 14, they could be differentiated by their karyotype formula and quantitative parameters of the karyotypes. Phenetic distance and principal component analysis showed that in spite of the differences observed among entities, they can be grouped in clusters that coincide with the taxonomic sections established by F. K. Kupicha and with the life cycle of the species. South American species form a homogeneous group and can be distinguished by the presence of a subtelocentric pair, which has a macrosatellite in the long arm, and the lack of a short metacentric pair characteristic of most species of the Northern Hemisphere. From an evolutionary point of view, variation in total chromosome length without major changes in the karyotype formula suggests that changes in the amounts of genomic DNA are proportional to the relative length of each chromosome arm and that species of Notolathyrus evolved in a concerted fashion. Variation in genome size, however, is congruent with morphological variation of some reproductive organs as well as with the life cycle and minimum generation time, as predicted by the nucleotype hypothesis.     

Genetic diversity in Cytisus aeolicus Guss. (Leguminosae), a rare endemite of the Italian flora

ABSTRACT

Cytisus aeolicus Guss, is an endemic plant restricted to the isles of Vulcano, Stromboli and Alicudi in the Aeolian archipelago. All known populations were assayed for genetic variability using enzyme polymorphism. Allozyme variation at 16 loci coding for 10 enzyme systems was examined. The great majority of loci turned out to be monomorphic or fixed heterozygous. The observed genetic depauperation is indicative of historical factors, such as the bottleneck effect associated with migration, and the founder effect in population re-establishment. The low genetic diversity is largely partitioned within rather than among populations, indicating that extant populations have not been established long enough for divergence to have occurred. The genetic uniformity, combined with the scattered distribution of small populations, and the negative shift of population size point to a critically endangered species. Strategies for conservation are considered.     

The taxonomy, reproductive biology and economic potential of Parkia (Leguminosae: Mimosoideae) in Africa and Madagascar

The taxonomy, reproductive biology and economic potential of Parkia (Leguminosae: Mimosoideae) in Africa and Madagascar. Three species of the pantropical woody genus Parkia are recognized from continental Africa (including São Tomé), P. biglobosa, P. bicolor and P.filicoidea. A fourth species, P. madagascariensis , is confined to Madagascar. All have capitula of similar structure although details of shape vary. Relatives sharing this capitulum structure occur in the Far East and the Neotropics. Patterns of infraspecific variation are described for the mainland species. Parkia biglobosa shows clinal variation in several leaf characters and P. clappertoniana must be regarded as synonymous. Parkia bicolor shows geographical variation especially in capitulum shape and pod width, and P. filicoidea varies geographically in its pod morphology. The red, balllike capitula are pollinated by bats; other visitors include birds, insects and non-flying mammals. In P. biglobosa a proportion of the capitula is functionally male. The pods of the African species contain mealy pulp. Dispersal involves mammals, especially primates, and birds. Information on uses, chemical composition of the seeds and insect pests is summarized.     

The Chilean coastal range: a vanishing center of biodiversity and endemism in South American temperate rainforests

Temperate forests of southern South America are globally important because of their high level of endemism. I argue here that within southern South America, rainforests of the Chilean Coastal Range should be the primary target for new conservation efforts. Historically, most protected areas in southern South America have been designated to preserve forests above 600 m, mainly in the Andes. However, Coastal Range forests have higher species richness and are under greater threat than Andean forests at similar latitudes. Coastal forests are characterized by the presence of numerous narrow-range endemics, among them two monotypic plant families. The higher frequency of endemic species in Coastal Range forests is attributed to its more stable biogeographic history compared to the Andes, particularly during the glacial events of the Quaternary. Due to the extent of human impact, the remaining fragments of coastal forests are quite distant from one another, and are disconnected from the larger protected areas of Andean forests. Only 439000 ha of Valdivian coastal forest still remain, including some remnants of primary forest. New private or public reserves should be created to protect the last remnants of continuous forest remaining on the Coastal Range of the Valdivian region (40–42° S). A different conservation strategy should be applied north of 40° S, where protected areas are too small and fragments are too scattered to maintain viable populations of most vertebrates. In this latter area, I recommend expanding existing reserves, restoring native forests, and interconnecting remnant forests through a corridor network.     

Genetic diversity and reproductive biology in Warea carteri (Brassicaceae), a narrowly endemic Florida scrub annual

Carter's mustard (Warea carteri) is an endangered, fire-stimulated annual endemic of the Lake Wales Ridge, Florida, USA. This species is characterized by seed banks and large fluctuations in plant numbers, with increases occurring in postdisturbance habitat. We investigated the mating system, patterns of isozyme variation, and effective population sizes of W. carteri to better understand its population biology and to comment on reserve designs and management proposals relevant to this species. Warea carteri is self-compatible and autogamous, and probably largely selfing. Measures of genetic variation in W. carteri were lower than values reported for species with similar ecological and life history traits (6.6% of loci polymorphic within populations, 1.87 alleles per polymorphic locus, and 0.026 and 0.018 expected and observed heterozygosity, respectively). The high average value for Nei's genetic identity (0.989) reflects the paucity of genetic diversity. Genetic variation within populations was not correlated with aboveground population size, effective population size estimates (N(e)), or recent disturbance history. Much of the diversity detected was found among populations (F(ST) = 0.304). A significant cline in allele frequencies at one locus and a significant negative correlation between geographic distance and Nei's genetic identity also point to spatial organization of genetic diversity. As a result we propose that reserve design should include the entire geographic range of W. carteri. We also recommend that the natural fire regime be mimicked.     

Grindelia mendocina (Asteraceae, astereae), a new South American species

Taxonomic revision of South American species of Grindelia Willd. has revealed a new species from Argentina, with homogamous capitula and cushion-shaped habit. The taxon is here described and illustrated.     

Genista valsecchiae (Leguminosae), a new species from Sardinia

Genista valsecchiae from SW Sardinia is described and illustrated as a species new to science. It is very similar toG. ephedroides and can be distinguished by morphological differences of habit and inflorescence. It typically occurs in the garigue or maquis and is widespread in SW Sardinia.     

Conditional male dimorphism and alternative reproductive tactics in a Neotropical arachnid (Opiliones)

In arthropods, most cases of morphological dimorphism within males are the result of a conditional evolutionarily stable strategy (ESS) with status-dependent tactics. In conditionally male-dimorphic species, the status’ distributions of male morphs often overlap, and the environmentally cued threshold model (ET) states that the degree of overlap depends on the genetic variation in the distribution of the switchpoints that determine which morph is expressed in each value of status. Here we describe male dimorphism and alternative mating behaviors in the harvestman Serracutisoma proximum. Majors express elongated second legs and use them in territorial fights; minors possess short second legs and do not fight, but rather sneak into majors’ territories and copulate with egg-guarding females. The static allometry of second legs reveals that major phenotype expression depends on body size (status), and that the switchpoint underlying the dimorphism presents a large amount of genetic variation in the population, which probably results from weak selective pressure on this trait. With a mark-recapture study, we show that major phenotype expression does not result in survival costs, which is consistent with our hypothesis that there is weak selection on the switchpoint. Finally, we demonstrate that switchpoint is independent of status distribution. In conclusion, our data support the ET model prediction that the genetic correlation between status and switchpoint is low, allowing the status distribution to evolve or to fluctuate seasonally, without any effect on the position of the mean switchpoint.     

Germination and reproductive biology in salty conditions of Asplenium marinum (Aspleniaceae), a European coastal fern

Although there are several species of ferns that are important components of many coastal ecosystems, the adaptations that allow these species to live in salty conditions have been studied only in two Acrostichum species. We have studied the effects of salt on germination, development of the gametophyte and sexual expression of the fern Asplenium marinum, which lives on coastal cliffs of Europe. Cultures at four different levels of salt concentration, 0%, 0.98%, 1.96% and 3.26%, were established for this purpose. Salt caused a significant delay in spore germination, and prevented it completely at high concentrations (3.26%). However, spores were able to recover germination ability after a period of seawater incubation once salinity concentrations decreased. Variable salinity conditions are a typical feature of sea cliffs where halophytes can grow. A salty culture medium also affects the development of the prothalli. Higher salinity of the substrate produced a significant decrease in gametophyte sizes, and affected the development of gametangia as well. Only males were found in a 0.98%-salt medium, and no gametangia were observed in cultures at 1.96%-salt medium. Recovered spores after one and a half month in high salinity concentration, 3.26%, were able, when transplanted to 0%-salt medium, to develop normal sexual prothalli, and this occurred in a shorter time than spores without any prior treatment. A. marinum can be considered as a halophyte fern that is able to germinate and grow in salty conditions. But it takes advantage of rainy periods that cause decrease of salt concentration, which seems to be important in particular for gametangia development and fertilization.     

Predispersal reproductive biology of female Osyris quadripartita (Santalaceae), a hemiparasitic dioecious shrub of Mediterranean scrublands

Female Osyris quadripartita plants exhibit uninterrupted reproductive activity throughout the year, due to the long duration of successive stages in the cycle and marked within-crop developmental asynchrony. Cycles corresponding to the flowering seasons of consecutive years overlap in each individual. Flowering takes place in spring, and fruits develop in the dry summer season and ripen at any time of the year. Variation in flowering time explains a negligible proportion of variation in ripening time. The greatest reproductive losses are incurred in the phase extending from closed flowers through unripe fruits, mostly due to ovary abortion. Only 30% of closed flowers eventually reach this latter stage. In contrast, 75% of unripe fruits complete their development, with subsequent dispersal of seeds. The probability of the setting of ripe fruit steadily decreases from early to late season flowers, due to increased ovary abortion rates. Resource limitation in the dry summer season seems responsible for this pattern of selective fruit maturation.     

Dispersal biology of Liatris scariosa var. novae-angliae (Asteraceae), a rare New England grassland perennial

Propagule dispersal biology is a crucial avenue of research for rare plant species, especially those adapted to disturbance, such as northern blazing star (Liatris scariosa var. novae-angliae), a rare, early-successional New England grassland perennial. We examined the dispersal ability of northern blazing star propagules collected from 14 populations covering the entire latitudinal range of the taxon. Multiple regression demonstrated that dispersal ability, as measured by drop time in still air and flight distance in a low-speed wind tunnel, decreased significantly with propagule size and achene length, and increased with achene width and (for flight distance) pappus length. We used this multiple regression model to test for differences in predicted dispersal capability among maternal families, populations, and inland, coastal, and island habitats. Dispersal capability differed significantly among families and populations but not regions, and allometric relationships between morphological measurements were consistent across populations. Overall, dispersal capability was negatively correlated with germination success in a common greenhouse environment. However, germination success for a given dispersal ability, as well as achene shape, differed among populations. These results suggest specific populations to be targeted for management efforts promoting dispersal and establishment.     

Reduced sexual dimorphism in upper arm muscle circumference associated with protein-deficient diet in a South American population

Animal experiments have demonstrated that individuals exhibit differing tendencies to arrest growth and resorb muscle tissue under nutritional stress. Since placental and adrenocortical hormones are active in promoting muscle tissue resorption, sex differences may exist. In order to identify such sex differences, the upper arm circumferences of 362 individuals, aged one to 60 years, living in an area of chronic protein-calorie malnutrition were compared by age and sex with published data collected from U.S. and highland Peruvian populations. Sexual dimorphism for arm muscle circumference in the malnourished population is less than in U.S. samples of comparable age-categories. The highland population is closer to U.S. samples in the degree of dimorphism. The reduction in muscle circumference of males in the malnourished population appears to be the cause of the comparatively greater similarity of the sexes where protein-calorie malnutrition is experienced from infancy through adolescence. High muscle relief and excellent tonus in these same males indicate that reduced muscle circumference is not the result of flaccidity or higher ratios of compressible fat to muscle tissue. Reduction of muscle tissue in undernourished males is a reduction in total metabolic demand. Such reductions are adaptive in areas of chronic nutritional stress.