Life History Differences between Rare and Common Flowering Plant Species of California and the British Isles

Generalizations about rare and endangered species are important for the development of conservation management policy and for understanding of the nature of rarity. Therefore, we sought such generalizations by statistically comparing eight life history and reproductive traits of rare and common plant species in two better-studied but climatically and geographically distinct Holarctic floras-those of California and the British Isles. Trends were often similar in both floras. Rare and common species differ significantly for a number of characters. In both floras, a woody habit was significantly more frequent for the rare species than the common species. Also, in both floras, monocarpy was less frequent in the rare species, significantly so in California. The rare species of both floras were, on average, significantly shorter in stature than the common species. This trend in stature remained significant when nonwoody species were compared but did not do so for woody species. Rare and common species differed with regard to their frequency of inflorescence structure types, but these differences were not concordant for both floras. The rare species of the British Isles had significantly higher proportions of mixed and polymorphic flower colors; the trend was not significant in California. In both floras, rare species had a higher frequency of many-seeded fruits, significantly so in California. California's rare species had a significantly higher frequency of dehiscent fruits than common species; the trend was reversed and not significant for the British Isles. We found no significant differences for characters associated with fruit dispersal. Finally, in California, the median altitude of the range of the common species was significantly greater than that of the rare species. At present, these correlates cannot be assigned as possible causes or consequences of rarity. Nonetheless, they may represent "high-risk" traits that could be used to identify other species already at risk or potentially at risk of becoming rarer.     

Florenreichtum als Gegenstand vergleichender Forschung

As the base area of the number of species the author proposed in 1931 the term „concrete flora”︁, that is the flora of an area great enough, to represent all possible sites, and small enough, to secure the universality of the flora in this whole area. In order to illustrate the regularities of quantitative traits of the floras some examples have been selected. The number of species in various concrete floras increases from arctic (0–350) to temperate (700–1100) regions, farther south the number still increases in humid regions (to about 3000), being very low in arid regions. A causal interpretation of these numerical regularities is not yet possible. As the number of species depends not only on the climate but also on the history of the flora, it allows deductions in relation to the history of floras.     

The myth of plant species saturation

Plant species assemblages, communities or regional floras might be termed 'saturated' when additional immigrant species are unsuccessful at establishing due to competitive exclusion or other inter-specific interactions, or when the immigration of species is off-set by extirpation of species. This is clearly not the case for state, regional or national floras in the USA where colonization (i.e. invasion by exotic species) exceeds extirpation by roughly a 24 to 1 margin. We report an alarming temporal trend in plant invasions in the Pacific Northwest over the past 100 years whereby counties highest in native species richness appear increasingly invaded over time. Despite the possibility of some increased awareness and reporting of native and exotic plant species in recent decades, historical records show a significant, consistent long-term increase in exotic species (number and frequency) at county, state and regional scales in the Pacific Northwest. Here, as in other regions of the country, colonization rates by exotic species are high and extirpation rates are negligible. The rates of species accumulation in space in multi-scale vegetation plots may provide some clues to the mechanisms of the invasion process from local to national scales.     

Long‐term non‐equilibrium dynamics of insular floras: a 17‐year record

Aim To document long‐term rates of immigration, extinction and turnover in insular floras and evaluate the relative impacts of recent hurricane activity and climate change. Location Three archipelagos of small islands, in the Exuma Cays, Andros and Abacos, Bahamas. Methods I surveyed the floras of 194 vegetated islands in three archipelagos over several multi‐year periods, spanning up to 17 years. Changes in abundance (foliar cover) of persistent populations were measured on a subset of 14 islands in the Exuma Cays over a 9‐year period. Results Rates of plant turnover were generally low compared with other organisms, but varied among archipelagos and time periods. Turnover rates were usually higher in the second decade of this study, and extinction rates were often dramatically higher than immigration rates in the second decade, resulting in overall decreases in species richness. Turnover did not differ significantly among island types based on generalized location and surrounding water depths, and extinctions were not more likely to occur on more exposed islands. The abundance (foliar cover) of populations that did not go extinct decreased steadily over the second decade of this study, indicating, along with higher extinction rates, a generalized decline in these insular floras. Main conclusions Although some islands may have been at or near a state of dynamic equilibrium in the first decade of this study, average species richness declined in all three archipelagos during the second decade, when extinctions greatly outnumbered immigrations. Four major hurricanes affected the study archipelagos in the second decade of this study, although the available evidence suggests that the hurricanes were not directly responsible for the declines. Indirect effects of hurricanes such as increased herbivory and possible decreased nutrient availability, along with a long‐term (25 years) increase in temperature and decline in rainfall are likely contributing factors.     

Strong indication of an extinction‐based saturation of the flora on the Pacific Robinson Crusoe Islands

Oceanic islands are vulnerable ecosystems and their flora has been under pressure since the arrival of the first humans. Human activities and both deliberately and inadvertently introduced biota have had and continue to have a severe impact on island endemic plants. The number of alien plants has increased nearly linearly on many islands, perhaps resulting in extinction‐based saturation of island floras. Here, we provide evidence for such a scenario in Alejandro Selkirk, Robinson Crusoe Islands (Archipelago Juan Fernández, Chile). We compared species richness and species composition of historical vegetation samples from 1917 with recent ones from 2011. Changes in species’ relative occurrence frequency were related to their taxonomic affiliation, dispersal mode, distribution status, and humidity and temperature preferences. While total species richness of vascular plants remained relatively similar, species composition changed significantly. Plants endemic to the Robinson Crusoe Islands declined, exotic species increased substantially within the period of ca. 100 years. Further, the relative occurrence frequency of plants with preferences for very warm and humid climate decreased, while the opposite was found for plants preferring drier and colder environments. Potential drivers responsible for this dramatic shift in the vegetation within only one century might have been the large goat population affecting especially small populations of endemic plants and climatic changes. Taking into account a substantial extinction debt, we expect further shifts in the vegetation of this small oceanic island toward alien plants. This would have significant negative consequences on global biodiversity, considering that island floras contribute substantially to global plant species richness due to their high proportion of endemics.     

A decline of melanism in the peppered moth Biston betularia in The Netherlands

Melanic forms of the peppered moth Biston betularia were well established in The Netherlands by the end of the 19th century, indeed the first records of the black carbonaria form in 1867 are only about 20 years later than in England. Analysis of extensive sampling data collected by B. J. Lempke for a period of several years beginning in 1969 shows that carbonaria was at a frequency of about 60 to 70% in most of the country where epiphyte communities on trees were reduced due to the effects of air pollution. The pale typica and the three intermediate insularia forms were each at similar, low frequencies. Only in the extreme north and south-east of The Netherlands where epiphyte floras were richer was carbonaria at a lower frequency of less than 40%. Samples collected from seven localities in 1988 show that carbonaria has dramatically declined to a frequency of less than 10%. In contrast to England, the fully black form is being replaced not only by typica but also by the darkest of the insularia phenotypes. The decline in melanism coincides with a period of decreasing levels of sulphur dioxide and of increasing species diversity of lichens on trees.     

Über einige quantitative Wechselbeziehungen der Floren der Erde

Some quantitative correlations of the floras of the world Both the sequence of the 10 families comprising the most species of a flora, and the percentage contributed by these families to the whole species number of the flora, are very constant in different floras of the same floristic region. In contrast, in floras of different floristic regions the list of these 10 richest families, and also their share in the whole species number varies considerably. Therefore, these characters are useful in defining floristic regions. The taxonomic structure of any flora is scarcely influenced by the extent of its area. The De Candolle rule (the percentage of the species-richest families in the whole species number of the flora is the lower, the richer in species the flora) is not generally valid. The complicatness of the taxonomic structure is not only depending on the species number of the flora, but also on its age: The share of the richest families in the whole species number of the flora is rather low, where the flora development was not disturbed for a long time, and it is high, if there were catastrophes in the geological past. The possibilities of florogenetic deductions are demonstrated in the cases of the Mediterranean, Middle Asiatic, dan East Asiatic floras.     

Cretaceous diversification of angiosperms in the western part of the Iberian Peninsula

The classic leaf fossil floras from the Cretaceous of the Lusitanian Basin, Portugal, which were first described more than one hundred years ago, have played an important role in the development of ideas on the early evolution of angiosperms. Insights into the nature of vegetational change in the Lusitanian Basin through the Cretaceous have also come from studies of fossil pollen and spores, but the discovery of a series of mesofossil floras containing well-preserved angiosperm reproductive structures has provided a new basis for understanding the systematic relationships and biology of angiosperms at several stratigraphic levels through the Cretaceous. In the earliest mesofossil floras from the Torres Vedras locality, which are of probable Late Barremian-Early Aptian age, angiosperms are surprisingly diverse with about 50 different taxa. In slightly later mesofossil floras, which are of probable Late Aptian-Early Albian age, the diversity of angiosperms is still more substantial with more than hundred different kinds of angiosperm reproductive structures recognized from the Famalicão locality alone. However, this early diversity is largely among angiosperm lineages that produced monoaperturate pollen (e.g., Chloranthaceae, Nymphaeales) and early diverging monocots (Alismatales). Eudicots are rare in these Early Cretaceous mesofossil floras, but already by the Late Cenomanian the vegetation of the western Iberian Peninsula is dominated by angiosperms belonging to various groups of core eudicots. The Normapolles complex is a particularly conspicuous element in both mesofossil floras and in palynological assemblages. In the Late Cretaceous mesofossil floras from Esgueira and Mira, which are of Campanian-Maastrichtian age, core eudicots are also floristically dominant and flowers show great organisational similarity to fossil flowers from other Late Cretaceous floras described from other localities in Asia, Europe and North America.     

Bryophyte dispersal inferred from colonization of an introduced substratum on Whiteface Mountain, New York

A long-standing debate in bryophyte biogeography concerns the frequency of long-distance spore dispersal. The diversity of bryophytes on mortared rock walls along the Veterans Memorial Highway on Whiteface Mountain, New York, USA, was studied to document the recruitment of species over the 65 years since the highway was constructed. The highway is situated in the Adirondack Mountains, a relatively unpopulated region with a largely acidic flora. The introduction of mortar has increased the bryophyte diversity by 50% above that of native lithic substrata on the mountain. The composition of the native and mortar floras differed greatly, suggesting that the walls were not colonized by locally abundant ruderal species. Many of the species sampled on the walls are typically found only in lower elevation forested sites, distant (～5 km or more) from the highway, and not on anthropogenic calcium carbonate. These results suggest that a bryophyte community consisting of common and uncommon species assembled from distant sites at the rate of at least one species per year in the last 65 years. These data provide the ecological context for experimental and phylogeographic studies and suggest that some bryophytes may be capable of routine dispersal over distances of at least 5 km.     

A comparative study of the distribution of genus size in twenty angiosperm floras

The biodiversity of floras has until recently been measured solely in terms of their species number or species density, with little regard to the breadth of phylogenetic diversity represented by the species. The latter is partly a function of the size of the flora, and partly of the pattern of distribution of the species into higher taxa. To determine whether floras differ in this respect, this study compares the frequency distribution of genus size in 20 island and regional floras. Certain floras (Cape Region, S.W. Australia, New Zealand, Hawaii) are found to have high concentrations of genera containing many species. Others are notably lacking in large genera (Java, Jamaica, Nepal, Niger), though this group tend to be family-rich. In floras with high endemism (Cape, New Zealand, Fiji, Jamaica, Hawaii), the level of endemism is consistently higher in larger genera. Possible reasons for the observed differences between floras are geographic and temporal isolation, level of habitat diversity, climatic history, volcanic, orogenic and tectonic events. Clusters of large genera may indicate recent speciation, possibly following the last glaciation. Genus size may be an important consideration when limited conservation resources have to be targetted to retain the maximum phylogenetic diversity in a threatened flora.     

Survey on the mycoflora of Egyptian wheat grains and their lemmae and paleae

The plating technique has been used to study the fungus floras of covered and uncovered wheat grains and their lemmae and paleae on glucose-cellulose and 40% sucrose-Czapek's agar at 28° C. Seventy-two species and 28 genera were collected from the three microhabitats on the three types of media. On glucose-Czapek's agar the most frequent species were Aspergillus niger, A. flavus, A. terreus, A. nidulans, Alternaria alternata, Cladosporium herbarum and Fusarium Oxysporum. On cellulose and 40% sucrose-Czapek's agar, the composition of fungal floras of the three substrates and the frequency of prevalence of the individual fungi were basically similar to those obtained on glucose agar, but the frequency of some species was promoted or decreased.     

Lichens on dead wood: species‐substrate relationships in the epiphytic lichen floras of the Pacific Northwest and Fennoscandia

Dead wood is an important habitat feature for lichens in forest ecosystems, but little is known about how many and which lichens are dependent on dead wood. We reviewed substrate use by epiphytic lichens in the combined floras of Fennoscandia and the Pacific Northwest of North America based on literature and herbarium data and analyzed substrate affinity relative to life form, reproductive mode and major phylogenetic group within the floras. A total of 550 (43%) of the 1271 epiphytic species in the combined floras use wood, and 132 species (10%) are obligately associated with dead wood in one or both regions. Obligate and facultative wood‐dwelling guilds in the two floras were strongly similar in terms of internal guild structure in each region, but differ somewhat in species composition, while the bark‐dwelling guild differs strongly in both. Most obligate dead wood users are sexually reproducing crustose lichens. The largest numbers of species are associated with forest structural features such as logs and snags that have been greatly reduced by forest practices. Conservation of lichens inhabiting wood requires greater attention to crustose lichen species and the development of conservation strategies that look beyond numbers and volumes of dead wood and consider biologically meaningful dead wood structure types.     

Long-term changes in intertidal flat macrozoobenthos as an indicator of stress by organic pollution

Organic waste-water from beetsugar factories is being discharged by pipeline into the eastern part of the Dutch Wadden Sea since 1969 mainly in September–December. The organic waste load was high in the first four years and diminished considerably from 1974 onwards.From 1968 macrobenthos has been monitored at five permanent stations. Two of these stations were situated relatively close to the outfall of the pipe-line.Data on numerical density of seven macrobenthic species were analysed for synchrony of yearly fluctuations in order to discriminate between pollution-induced changes in population densities and changes due to variation of natural environmental factors.A great deal of concordance in density fluctuations was found between the five stations. Comparison with data from the western part of the Dutch Wadden Sea (150 km apart) revealed a relative good concordance of the density fluctuations in eastern (only 3 stations) and western Wadden Sea. The two stations close to the outfall showed an aberrant pattern of density variations due to the waste discharge.     

Qualitative variation in roadside weed vegetation along an urban–rural road gradient

Information on mechanisms of differentiation or homogenization of urban floras is deficient, despite their importance for urban nature conservation and urban land management. Roads, as a major human promoter of urbanization, can be an initial habitat for plants dispersed by transportations. We assumed that variation in weed vegetation along urban–rural roadside gradients is small, particularly in curbside cracks. We classified vegetation occurring in curbside cracks along the National Route 3 in southern Japan and compared the characteristics of the vegetation types recognized. Species in curbside cracks were recorded on 40 plots. Three vegetation types were classified, in part related to surrounding land-use types. Although the Shannon–Wiener diversity index and the number of native species clearly differed among the vegetation types in the curbside cracks, no significant differences between the three floristic vegetation types were found in the number of non-natives and invasive alien species. This may result from the small specificity and complexity of landscape structures, due to the continuity and connectivity of paved-road networks. Of the 122 species, 44 were non-natives or invasive alien species. The vegetation types generally involved the same plant families, with large numbers of species from the Asteraceae and Poaceae, regardless of vegetation types, but frequency of occurrence of the two families clearly differed between natives and non-natives and invasive alien species. Ephemeral non-natives and invasive alien species, particularly Asteraceae and Poaceae, seem to have advantageous dispersal strategies or low habitat dependency facilitating their occurrence in curbside cracks, regardless of adjacent land uses and the urban–rural landscape gradient. Expansion of these species may cause a homogenization of regional floras along roads.     

Studies on Plover Cove Reservoir, Hong Kong

The species composition and year-month frequency together with the abundance of the four periphytic communities of Plover Cove Reservoir (the epiphyton, epilithon, epipelon and epipsammon) were compared both in terms of all species present and in terms of major (dominant/frequent) species using the ‘circle’ method. All four communities were similar in terms of overall species composition but the richest variety of species occurred in the epiphyton. The diatom floras on wood and rock surfaces closely resembled each other as did the two sand grain floras. The former floras were, however, much more diversified than the latter floras and stood distinctly apart from them. In terms of their dominant/frequent species, the epipelic/epipsammic communities and the epiphytic/epilithic communities had the same number of common taxa (three), a further indication of the closeness between the two communities in each combination. On the other hand, the fact that the three common taxa were different for each combination again reveals the distinct differences between the two combinations. Investigations concerning the effect of the nature of the substrate on diatom growth revealed that it had little effect in qualitative terms. Quantitatively there would appear to be some effect, since differences in abundance and frequency and thus in the seasonal cycle of diatoms growing on different substrates were observed. The conditions in the microhabitats of each substrate undoubtedly determined the dominance and abundance of the flora. However, the effect of the nature of the various substrates on diatom growth varied from species to species and in general, the substrates showed little qualitative selectivity. Thus, no truly differential species were found to any great extent on any of the four substrates. The relationships between the growth of these four periphytic diatom communities and the physical and chemical conditions have also been investigated in terms of cell number and chlorophyll content. Both graphical and statistical analyses of the results are discussed, and it is suggested that fluctuations in water level, temperature and nutrients (especially silica, nitrate and phosphate) are the major factors governing the seasonal patterns of variation in periphyton standing crop. Thus, diatom growth is maximum when nutrient concentrations and water level are high and when water temperature is low, and as temperature increases and nutrients decrease so diatom growth falls. It is probable that an interplay of these factors, together with the detrimental effects of heavy rainfall and typhoons during summer, is responsible for the seasonal changes in periphyton in Plover Cove Reservoir exhibiting a winter peak as opposed to the commonly occurring spring and autumn growth peaks.     

Geochemistry and ecology.

This paper discusses the importance of geochemistry as a determining factor in the evolutionary development of plant assemblages. Three contrasting examples of geochemical systems are described and considered in relation to their effects on plant growth and development. Soils derived from serpentines may contain elevated and sometimes toxic concentrations of Cr and Ni depending on mineral composition and weathering processes. These conditions have so modified plant growth during the past few million years that specialized floras have evolved on particular sites. Extensive areas throughout the world contain high concentrations of Se but these have not always been accompanied by the development of specific floras. Geochemistry can help explain how Se-specific floras have developed in several Western States of America but are absent on Se-rich sites in the Republic of Ireland. Pronounced effects of As toxicity in plants have been recognized in recent years especially from areas polluted by smelter waste and fallout. As-tolerant genotypes have developed during the past 100 years and may still be evolving at the present time.     

The Rhaetian flora of Rögla,northern Scania,Sweden

Abstract: Rögla is the northernmost locality yielding Mesozoic plant fossils in Scania, southern Sweden, and is one of the northernmost Rhaetian assemblages in Europe. The assemblage consists of over 500 specimens collected 50–60 years ago, of which 139 yielded identifiable plant remains referable to 15 plant species; another 19 specimens are tentatively assigned to four species because of their fragmentary preservation. The flora includes sphenophytes, ferns, cycads, bennettitaleans, seed ferns of uncertain alliance, conifers and some leaf remains that are tentatively assigned to ginkgophytes based on their epidermal anatomy. The species‐level composition of the assemblage is consistent with a Rhaetian age and is similar to well‐known floras from nearby Höganäs and Bjuv, except for the absence of cycads belonging to Nilssonia, which are very common in most other Scanian floras. The fossil assemblage is interpreted to derive from multi‐storey vegetation occupying moist habitats on a coastal plain. Strong affinities are evident with the coeval floras of Jameson Land, Greenland, reinforcing the concept of a distinctive North Atlantic floristic sub‐province at the close of the Triassic.     

The effect of a new sewage treatment plant on faecal indicator numbers, campylobacters and bathing water compliance in Morecambe Bay

Until recently, sewage from Morecambe was macerated, but otherwise untreated, and discharged at high water via a short outfall pipe into Morecambe Bay adjacent to a recognized bathing water. In March 1997, a new biological sewage treatment plant came on-line and the effluent was discharged via a longer outfall pipe into the Bay south of Heysham. The effect of the new sewage treatment on the quality of the bathing waters was monitored by testing sea water collected from the three EU designated bathing waters on Morecambe Bay: Morecambe North, Morecambe South and Heysham. After sewage treatment came on-line, the numbers of faecal coliforms and faecal streptococci were lower at Morecambe North and Morecambe South but higher at Heysham. Although the changes in numbers were not always statistically significant, they were sufficient to affect compliance with the EU Bathing Water Directive Imperative (mandatory) standards. Compliance improved markedly at Morecambe North and South but declined at Heysham, the closest bathing site to the new outfall. Numbers of thermophilic campylobacters were similar in both years, which is suggestive of their sources being different from those of the indicator bacteria. Campylobacter lari and urease-positive thermophilic campylobacters (UPTC) were the only species of Campylobacter isolated from Morecambe's bathing waters. Very low numbers of Salmonella were found, with Salm, arizonae the only species isolated.     

A comparison of the sexual systems in the trees from the Australian tropics with other tropical biomes--more monoecy but why?

Rainforests in tropical Australia occupy a very small, discontinuous area (<1% of the continent), yet they are floristically diverse (c. 2800 vascular species) with high endemicity. There is a distinctive Gondwanan and autochthonous element, and some of the world's ancestral links to the basal angiosperms are uniquely found here. The rainforests can be evergreen or deciduous, but there is a distinct dry season with intermittent drought years. With these characters, the evolutionary pressures on species may be very different to that experienced elsewhere. Sexual systems of 1113 tree species (83 families) from northern Australia were compared with published accounts from the paleo- and neotropics. Hermaphroditic systems dominated all tree floras, and within all floras but Australia dioecy was the most common unisexual system. In tropical Australia, however, significantly more monoecy than dioecy occurred at landscape and community levels. Incorporating phylogeny revealed that sex and fruit types are significantly clustered. The Euphorbiaceae and Sapindaceae contributed c. 50% of the monoecious taxa. Inefficient pollinators (e.g., beetles) may have favored the maintenance of monoecy at the expense of dioecy in the Australian tropics although <1% of the flora has been studied for pollinators and none of the monoecious tree species.     

Trophically-based assessment of the impacts of deepwater sewage disposal on a demersal fish community

Synopsis The impacts of sewage disposal on the demersal fish community were identified after approximately 2 years of operation of a deepwater outfall off Sydney, NSW Australia. Gut-content analyses were used as a basis for identifying groups of fish with dietary similarities. Similar results from multivariate analyses (Bray-Curtis dissimilarity measure and MDS) identified 8 trophically-similar groups of fish. The majority of the fish comprising these groups consumed organisms in the soft-bottom community. Only 5 of the 8 trophic groups identified could be analysed in detail as individuals comprising the remaining groups were not caught in sufficient numbers near the outfall. Asymmetrical analyses of variance showed that the numbers of individuals and species in one particular trophic group increased significantly following the commissioning of the Bondi deepwater outfall. However, the proportional representation of individuals in the 5 trophic groups examined did not change. Five hypotheses are advanced to account for the observed impacts. Of these, hypotheses centred around increased habitat complexity and a numerical response to increases in prey abundance warrant further investigation. Directions of future research and the limitations of various designs to assess environmental impacts are discussed in light of these results.