Accidental Species Research Articles

Species Richness, Species Rarity and Conservation Evaluation of Rich-Fen Vegetation in Lowland England and Wales

(1) The botanical resource of rich-fen sites in England and Wales is analysed, based on a survey between 1972-85 of most known sites. The 464 plant species recorded in the survey are segregated into those (153) for which fens are a major habitat (principal fen species), those (203) that are as well or better represented in other habitats as in fens (affiliated species) and those (108) essentially atypical of fens (accidental species). (2) The occurrence of principal fen species of low frequency (occurring in < 5% of samples) (i.e. rare species) is analysed from 2900 quadrats from herbaceous and wooded fen vegetation. Many rare species occur mainly in just a few distinctive herbaceous vegetation types of low crop mass. Most do not occur at all in fen carr. (3) Variation in species richness (number of species 100 m-2) in 2100 samples of herbaceous fen vegetation is analysed. Very species-rich stands are infrequent and referable to just a few vegetation types. These are the ones that also contain most rare species. (4) Individual fen plant species (principal and affiliated species) occupy a discrete range of vegetation species-richness (the 'associated-richness') in herbaceous fen vegetation samples. Those species which show only small variation in the associated-richness values (interquartile range <50% median associated-richness value) are 'richness indicator species' and their occurrence can be used to predict the species-richness of herbaceous fen vegetation. (5) Regressions of total number of species and number of common species against number of rare species within vegetation samples both show a strong (P < 0 0001) positive relationship. The proportion of rare species within the vegetation also increases with increasing species richness. (6) The present infrequency of species-rich vegetation (and its associated rare species) in undrained fens is probably mainly due to increase in vegetation crop mass at many sites, caused by the abandonment of traditional management regimes perhaps exacerbated by increased net productivity caused by fertilizer run-off from the catchments. (7) A few rare species are most characteristic of comparatively species-poor vegetation of fairly high crop-mass. The reasons for their current rarity are not known. (8) The data on species-richness and rarity provide a basis for conservation priorities in rich-fens. Four possible indices, based on richness and rarity, for the evaluation of fen sites for conservation are proposed and fifteen sites are evaluated using these.

A new genus for Chirosia hirtipes Stein, and a reassessment of Heterostylodes Hennig (Diptera: Anthomyiidae)

[Boreophorbia hirtipes (Stein, 1907), new genus and new combination, is a tiny anthomyiid occurring in subarctic and montane zones of the Holarctic. It was previously treated in Chirosia Rondani, but evidence is provided that hirtipes belongs to the Delia group of genera, and that Boreophorbia (monobasic) is the sister group of Phorbia Robineau-Desvoidy. Heterostylodes Hennig, the alledged sister group of Phorbia + Boreophorbia, is reassessed. 9 species are recognized in Heterostylodes, among them annularis (Tiensuu, 1946), caledonica (d'Assis Fonseca, 1966), laevis (Stein, 1898) and nuditibia (d'Assis Fonseca, 1966), new combinations. H. obscura (Macquart, 1835) is a valid senior name for denigrata (Zetterstedt, 1845), new synonymy. Delia ricta (Ackland, 1971), new combination, is removed from Heterostylodes., Apatania zonella is an accidental or facultative parthenogenetic species; the percentage of males observed in various West Norwegian populations ranges from 0% to 5.2%. On the Hardangervidda mountain plateau (over 800 m a.s.l.), the species has a flight period from late June to mid-September, and supposedly has a two year life cycle. In the western lowlands the species has a bimodal flight pattern: the first flight period is from mid-May to late June, the second flight period from early August to late October. Females with mature eggs have been taken during both flight periods, and the species supposedly has two more or less separate cohorts each with a one year life cycle. Morphometric variation of A. zonella in seven West Norwegian populations was studied using multivariate statistical methods. Specimens collected in three lowland populations in June were found to differ from specimens collected in the same populations in autumn, but they were obviously more similar to autumn specimens from the same locality than to specimens from the other localities. Most of the samples from the lowlands collected in autumn and the samples from the mountainous eastern areas were found to differ significantly. The specimens from the eastern mountain populations were generally larger than the specimens from the western lowland populations. Clinal shape variation was established, following more strongly a west - east gradient than an altitudinal gradient. The specimens in the eastern populations had generally smaller eyes, narrower heads and longer, narrower front wings.]

Structure comparée du peuplement avien dans trois sites de forêt primaire en Guyane

The bird communities of three rain forest areas of southern French Guiana, two of them “virgin” and the third hunted, are described. The sampling procedure involved 408 one hour, 250 m long, transect counts randomly distributed over a 70 km²surface area, and seven 3-days periods of mistnetting along similar 250 m lines. The 361 resident species identified certainly did not represent the whole bird community, as the species/area curves would not reach an asymptote without a 2-fold increase of the sampling effort. The overall calculated density ranged from 1,226 to 1,615 birds/km². Mistnet lines gave a mean hourly catch in the low undergrowth similar to the results of the transect counts, but the proportions of the species were different. The total biomass (fresh weight) reaches at least 70 to 150 kg/km². The three more important guilds were, by number of individuals, the insectivores (54-65 %), the omnivores (16-20 %), and the frugivores (13-15 %) ; if these guilds were ranked by weight, the results was reversed (15-25 %, 24 %, and 38-50 %, respectively), because of the large size of many frugivores. About 1 % of the species were common, 10 % regular with moderate densities, the rest being occasional to accidental species together making up half the total of the species present. 79 to 85 % of the species appeared in less than 5 % of the sample counts, although each count included on average 20-25 birds of 10-13 species. Consequently, the diversity index was high. Species densities were lognormaly distributed and taxonomic diversity was high (72 genera per 100 species). The differences in species richness, turnover rate, relative abundance, population structure, density and total biomass were greater between sites than within site plots, and higher than expected from habitat distribution — which means that vegetation alone could not account for the differences observed. Frugivores had a bimodal vertical distribution 74-82 % of their biomass being found at ground level and in the canopy ; insectivores were the dominant guild in the intermediate layers. More than half the consuming biomass was found in the canopy, but the maximum number of species per volume unit of vegetation was found in the low undergrowth. Most of the species were randomly dispersed along the transect lines and widely spaced : for one third of those recorded, successive contacts were more than 23 km apart, on average, and for only 2 % of the species the mean spacing was less than 1 km. Most species were habitat or food specialists, and 135 were recorded in mixed feeding flocks. Hunting pressure significantly reduced species richness, diversity, density and biomass. Not only game birds, but also raptors and insectivores were affected, probably through complex interactions and the disappearance of top predators. Changes in community structure included a greater abundance of the more common species, and the scarcity if not the disappearance of rare species. The 3-fold decrease of the biomass of frugivores might have a detrimental effect on the seed dispersal of some trees, and therefore lead to a longterm modification of the forest structure. Bird biomass, but not density, is significantly higher in tropical than in temperate forests. The higher species richness of the former is therefore due to a tighter species packing, with a lower mean density of individuals. If the size of a self-supporting, isolated population is of 1,000 breeding pairs, i.e. about 5,000 individuals, then one third of these primary forest species would need a reserve of more than one million hectares to survive according to the estimated densities, and without allowing for the distributional gaps and the seasonal movements of unknown extent which also occur.

The Lake Tega, the Former Home of Waterfowl

After its half a century activity at Shibuya, Tokyo, the Yamashina Institute for Ornithology has been opened on 1 December 1984 at its new site near lake Tega, Abiko City, Chiba Prefecture.The lake Tega had been one of the four marshy lakes, Imba, Wada, Ushiku and Tega, which provided the most important winterquarters for waterfowl in central Honshu. Geese, the Bean and White-fronted, concentrated at lake Wada and ducks preferred Tega where joint duck-netting grounds existed since old tims. A pair of ducks caught were annually presented to Toyotomi and then Tokugawa Shogunates. The pochard, Aythya ferina was characteristic wintering species of the lake and many rare and accidental species of waterfowl had been obtained and observed, including Snow Goose, Canada Goose, Canvasback, Long-tailed Duck, Rudy Shelduck, etc.After the world war II, ducks were persecuted by indiscriminate gun-hunters and traditional netting came to the end. Moreover, main area of waterfowl resort was reclaimed for rice fields.However, remaining water surface is now protected from hunting and is still visited and inhabited by ducks, coots, moorhens and reed buntings, etc. The water pollution of lake Tega has been reputed as worst of lakes, but measures of water purification are being advanced. We saw and heard a green pheasant, an Ural owl and other birds in back-hill wood of new institute site, and it would be a tempting idea to have, in future, a waterfowl laboratory somewhere along the lake coast.

Adventive flora of Israel — Phytogeographical, ecological and agricultural aspects

73 adventive wild species occur in the flora of Israel: 39 are of tropical origin, 20 are North American. The geographical distribution pattern suggests that about two thirds of the species reached Israel through neighbouring countries, while only one third arrived directly from their countries of origin. — Three patterns of population dynamics can be recognized: accidental species (7), colonizing species (30), and species penetrating into natural habitats (3). There is insufficient information about the remaining species. — About 20 species are widespread noxious weeds which now have economic significance in Israel, 20 others are known to have similar ecological tendencies in other countries. These species soon may become aggressive weeds in Israel.

Nordic equiseticolous Pyrenomycetes

The Pyrenomycete flora on Equisetum has been studied, mainly on Nordic material. With regard to frequency and host specificity these fungi can be divided into three groups, viz. 1) true Equisetum fungi; 2) common species but not restricted to Equisetum; 3) accidental species. An annotated list is given of the two first categories which comprise the following taxa. 1: Didymosphaeria equiseti–hiemalis, Phaeosphaeria berlesei, P. equiseti, Mycosphaerella equiseti, M. equiseticola, Scirrhia castagnei, S. silvalica, and probably Didymella equisetina. 2: Phaeosphaeria eustoma, P. fuckelii, Mycosphaerella cf. aspidii.Two new taxa and one new combination are published, viz. Phaeosphaeria equiseti (Karst.) L. &amp; K. Holm comb, nov., P. equiseti var. lindii L. &amp; K. Holm var. nov., Scirrhia silvalica L. &amp; K. Holm sp. nov.

Spring areas: ecology, vegetation, and comments on similarity coefficients applied to plant communities

Spring areas: ecology, vegetation, and comments on similarity coefficients applied to plant communities

Spider Associations in Coastal Sand Dunes

An investigation of the dune-living spiders was made during 1960-1962 in a coastal sand dune area of 40 ha at Sandhammaren, Province SkAne, Sweden. Eleven subdivisions were recognized for a vegetational survey; 821 samples from areas of 1 m2 each collected. 33 875 spiders were obtained, belonging to 152 species of which 80 were accidental species. Testing by means of an association method based on presence or absence data for 35 species in all samples, seven association groups were distinguished. By means of another grouping method using distance functions with an adjustable index, taxicoenoses, and their habitats were fixed.

Nesting Record of European Skylark in Washington State

The Skylark (Alauda arvensis) was introduced to Vancouver Island, British Columbia, Canada, in 1903 and 1913 (Carl and Guiget, British Columbia Provincial Museum Handbook 14, 1958). Bruce (Condor 63:418, 1961) gives a sight record for the species on San Juan Island, Washington, and Larrison (Washington Birds, Seattle Audubon Society, Seattle, 1968) includes it in an undocumented Rare and Accidental Species list. In 1969 Leslie Hall, a student at Western Washington State College, noted the species at the south end of San Juan Island. Further investigation showed several singing birds in an area of open, grassy habitat approximately one mile long and onethird mile wide. We searched the area, located at the monument marking the site of the American Camp during the Pig War of 1859-73, on 17 May 1970. After flushing an adult Skylark we found a nest containing three eggs, and we then followed food-carrying adults to a second nest containing four young birds a few days old. Both nests were within one-fourth mile of the monument. We estimated about 12 pairs of Skylarks in the area. Other species apparently nesting there included Savannah Sparrows (Passerculus sandwichensis) and Vesper Sparrows (Pooecetes gramineus). The area is heavily populated with European Rabbits (Oryctolagus cuniculus) and attracts numbers of eagles and hawks as well as foxes and other predators. Although the species may have introduced itself on San Juan Island years ago from Vancouver Island (about 15 miles away), as far as we can ascertain, this record is the first proof of its nesting in the state of Washington, and the only current record for the continental United States.

Habitats and Zoogeography of Alpine Tundra Arachnida and Carabidae (Coleoptera) in Colorado

Between 3500 and 4270m elevation (11,500-14,000 ft.) 174 pitfall jars were placed in a variety of habitats. In 1967, 71 species and 16,342 sepcimens of spiders, phalangids, mites, and ground beetles were collected. Species within the same genus usually occur in different habitats, as defined by vegetation cover and soil moisture. All tundra species, for which adequate records exist, also occur at elevations below tree-line. Accidental species of spiders may occur on the tundra, after having been blown up from lower elevations. Three species of arachnids differ in mean adult size between tundra areas 77km apart; one of these species also differs in size between 3650m and 4270m elevation. Many Colorado alpine tundra arachnid and carabid species also occur on other Nearctic mountains and in the northern taiga. The same spider genera and families dominate arctic and alpine tundra areas on several different continents.

Mixed Bird Parties in the Tropics, with Special Reference to Northern Rhodesia

IN a previous paper (1943), I gave an account of the woodland bird parties [flocks] of the Barotse and Eastern Provinces of Northern Rhodesia and suggested that most of the species found in them fell into two categories: species, always found in parties, either mixed or pure; and circumference species, which formed the mixed parties, as a rule, by attaching themselves to parties of species. This method of formation is not invariable, since mixed parties are sometimes found without any nucleus species, or with two or more nucleus species. I also suggested that while both protection and the disturbance caused by the party were possible reasons for their formation, neither was likely to be of as great value as had sometimes been supposed. While nucleus species often communicated the alarm from one individual to another of their own species, other members of the party often paid little attention; the advantage of disturbance depended greatly on the feeding habits of the species concerned and this, for some common members (woodpeckers) of bird parties, was nil. A most important study, based on very detailed and abundant data, has been published by D. E. Davis (1946). Stanford's paper (1947) on the bird parties in Northern Burma revealed the essential similarity of Asiatic and African bird parties. Davis, although no more successful than the rest of us in giving a really convincing explanation of the reason for this flocking habit, has written a most illuminating paper on their natural history. He divided birds found in the bird parties into regular and accidental, the former being, as the name implies, normally found in bird parties and only abnormally outside them, while the latter only join the flocks occasionally and are normally found outside them. I divided the members of the African birdparties into two categories also, and circumference, and Davis is inclined to equate these with his regular and accidental species, respectively. If I understand his definitions correctly, however, this is not the case, though the drongo, Dicrurus a. adsimilis, is, as Davis pointed out, a typical accidental species. The other common circumference species, such as Dryoscopus, Batis and Sylvietta are regular in Davis's sense. Apart from Dicrurus which occupies a unique position, a number of other African species occur as accidentals in bird parties, but they are infrequent and do not seem to me to affect the theoretical implications. An example from

A Study of Raunkaier's Law of Frequence

Numerous investigators in plant ecology have emphasized the importance of an accurate means of expressing the frequence of the different species in a plant association. It has long been recognized that one cannot, by looking at an association or a photograph of it, form an adequate conception as to the abundance of its various members; and it is even harder to convey a correct idea in writing because of the vagueness of such terms as ' rare,' ' occasional,' 'common,' abundant' and the like. Rubel ('20), who gives an excellent summary of the development of plant sociology, calls attention to the fact that these terms are not only indefinite in numerical significance but that they are often used ambiguously, referring either to geographical extent in a region or to sociological extent as a part of a particular formation. Probably the first to use numerical scales was Heer ('35), who designated relative abundance by the numbers one to ten, and degree of association of individuals of a species by the same series of numbers. For example 2: 9 would indicate that the plant is rather rare, but where found occurs in considerable masses. Lecoq ('44) used the same sort of scale for relative abundance, io signifying dominant species, 9 to 6, essential species, 5 to 3, accessory species and 2 to I, accidental species. A similar scale was suggested by Norrlin ('70) and employed by Hult ('8i). The latter was the first to use such a system extensively in evaluating the proportional numbers of species in the association. The numbers on his scale signify as follows: