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Showing papers on "Species richness published in 1969"


Journal ArticleDOI
01 Sep 1969-Ecology
TL;DR: It is suggested that the regulation of diversity by either the species richness or relative abundance components represent alternative strategies which are suited to predictable/nonrigorous and unpredictable/rigorous environments, respectively.
Abstract: Shannon's diversity index H' = Σpi log2 pi was calculated for 267 breeding bird censuses. The index was resolved into its components, species richness and relative abundance, to determine which components played a larger role in the determination of diversity patterns. Changes in diversity were correlated closely with species richness (r = 0.972), while the relative abundance component remained stable. Among the nine community types represented, diversity and species richness increased with foliage height diversity. The relatively abundance component was strikingly low in the marshes due to the presence of gregarious birds which nest in colonies and feed outside the community. Photoplankton differ from birds in that the relative abundance component is not stable from one collection to the next. This is attributed to differences in the environmental uncertainty encountered by the two groups, plankton inhabiting relatively uncertain environments and being "opportunistic," while birds occupy predictable environments and therefore "equilibrium" species. The distribution of relative abundances in birds is more even than in trees, herbaceous—shrub communities, or phytoplankton. Since this is in part the result of intraspecific territoriality, it is predicted that nonbreeding bird populations, species' relative abundances will be less even than they are during the breeding season. It is suggested that the regulation of diversity by either the species richness or relative abundance components represent alternative strategies which are suited to predictable/nonrigorous and unpredictable/rigorous environments, respectively. Therefore, differences similar to those observed between birds and phytoplankton might be expected in other groups of organisms.

250 citations


Journal ArticleDOI
01 Jan 1969-Ecology
TL;DR: When compared with other aquatic environments, the bottom fauna of the stream has oligotrophic features, including a large number of species and an annual standing crop of poor to intermediate richness.
Abstract: Seasonal changes in the distribution and abundance of insects species were studied in a small cool woodland stream where the primary food material was fallen leaves. Between March 1966 and March 1967, weekly quantitative samples were taken from sand, gravel, stone, leaf, and leaf detritus habitats. The number of insects per unit area of each habitat was least in sand and increased through gravel, stones, leaves, and detritus. Biomass per unit area was least in gravel and increased through detritus, sand, leaves, and stone. The annual standing crop of the stream as a whole was approximately 3,000 insects/m2 and 2 g/m2 (dry wt.). The number of insect species in any one habitat varied according to apparent spatial heterogeneity of the environment, to substrate stability, and to food resources. Leaves supported the highest number of species (92), sand the least (61). Species diversity was higher during summer and winter than during spring and autumn. When compared with other aquatic environments, the bottom fauna of the stream has oligotrophic features, including a large number of species and an annual standing crop of poor to intermediate richness.

114 citations


Journal ArticleDOI
TL;DR: Examination of the relative importance of the two components in the diversity index indicated that the variability of the index can in large part be attributed to the component of equitability as expressed in the 10 to 15 most abundant species.
Abstract: Seasonal observations on the diversity of phytoplankton communities were made in three lakes in Wisconsin. Extremes in nutrient availability and morphometry in the lakes yielded a range in diversity indexes calculated from Shannon's formula. Examination of the relative importance of the two components in the index indicated that the variability of the index can in large part be attributed to the component of equitability as expressed in the 10 to 15 most abundant species. It appears that with additional species, the positive effect of the component of species richness is countered by the negative effect of the equitability component. Species of low abundance appear to have a minor effect on the index of diversity. The response of the components is discussed in terms of interactions, relationships, and problems associated with estimating the diversity of indefinitely large communities.

78 citations


Journal ArticleDOI
TL;DR: The biological interest of chalk grassland is discussed under three headings: the richness of the flora and fauna, the presence of more than 60 species of plants in England alone which are restricted to the chalk or other calcareous grasslands, and the concept that chalk grasslands is a well-defined ecosystem as mentioned in this paper.

50 citations


Journal ArticleDOI
TL;DR: Ants can be used as indicators of forest recovery at La Planada Reserve, at southwestern Andine slope in Narino, Colombia, and taxonomic composition was associated with the successional stage (Simple Matching Coefficient).
Abstract: We evaluate the potential use of ants as indicator taxa of cloud forest recovery in La Planada Reserve, at southwestern Andine slope in Narino, Colombia. The ants were sampled from February through August 1995, using pitfall traps, tuna baits and manual collection, in seven localities representing forest successional stages: cattle ground, grassland (three year old), two ten year old forests and 20 year old, exploit and primary forests. We found 63 species (29 genera) with a 20-26 species richness per locality, with the exception of the ten year old forest (12 species). There were no any statistical differences in species richness and diversity among sam- ples and study sites. Nevertheless taxonomic composition was associated with the successional stage (Simple Matching Coefficient). Ants can be used as indicators of forest recovery at La Planada.

30 citations


Journal ArticleDOI
TL;DR: In this article, the origin of knowledge about fish species richness in the Tuxpan-Tampamachoco estuarine system, in Veracuz, Mexico, was analyzed.
Abstract: We analyze the origin of knowledge about fish species richness in the Tuxpan-Tampamachoco estuarine system, in Veracuz, Mexico. A complete inventory of the fish species known to date for this system (N=179) was elaborated from published lists and from sampling seagrass meadows of Tampamachoco Lagoon, which yielded 14 previously unknown species. W hen compared, the different Iists showed a low similarity that may reflect differences in sampling methods and collecting strategies. Current data suggest that fish species richness in Mexican coastal lagoons (Gulf of Mexico) is not related with iagoon surface area, as has been suggested, but with the number of inventories available for each lagoon, being these a reflection of the sampling effort. A sampling design for the assessment of fish species richness in estuarine systems should consider: a) using the highest possible variety of sampling fishing gears, b) col!ecting in al! microhabitat types and c) the preference of bimonthly or quarterly samplings for two or more years over monthly samplings in a single year

13 citations


Journal ArticleDOI
TL;DR: The chaetognaths of the Campeche Bank were studied in April-May, 1986 and Flaccisagitta enflata was the most abundant and widely distributed species in the study area; Sagitta tenuis was the second most abundant species and it ocurred in 79% of the sampling stations.
Abstract: The chaetognaths of the Campeche Bank were studied in April-May, 1986. Organisms were collected at 24 sampling stations with bongo trawls. The taxonomical identity of the specimens collected was determined with basis on McLelland's key and descriptions. We calculated density (expressed as a number of organisms per 100m3), frequency of occurrence and Importance Value (as the sum of relative density and frequency) for each species and species richness for each sampling station. A dendrogram of sampling stations was constructed using the Morisitas similarity index and the unweighted pair-group method that uses arithmetic means. Twelve spe- cies were recorded. The highest species richness was found at sampling stations located near the continental slo- pe, whereas only one or two species were recorded at the Campeche Sound. Flaccisagitta enflata was the most abundant and widely distributed species in the study area; Sagitta tenuis was the second most abundant species and it ocurred in 79% of the sampling stations. Krohnitta pacifica and Flaccisagitta lyra were the least frequent species. The highest density of quetognaths (>5 000 organisms/100m3) was recorded at some stations located at the Campeche Sound; values from 1 000 to 5 000 orgs./100m3 were recorded in the Western part of the Yucatan Peninsula. Three species groups could be recognised with basis on the speciesImportance Values: The first group (IV:> 75) includes F. enflata, S. tenuis, Ferosagitta hispida, K. subtilis and Serratosagitta serratodentata. The second group (IV:>36) comprises four species and the third group (IV:<15) includes the least frequent and abundant species Mesosagitta decipiens, K. pacifica and Flaccisagita lyra. From the dendrogram constructed from the Morisitas similarity index, five groups of sampling stations were distinguished. The first group inclu- ded two stations located off the Northern part of the continental slope, where M. minima was the dominant spe- cies and the Simpsons dominance index reached its lowest value (0.215). Most of the species recorded in the- se stations have an oceanic distribution. The second group comprised seven stations located near the upwelling zone, where F. enflata coexists with five to nine other species and the Simpsons dominance index had an inter- mediate value (0.243). The species recorded in these stations have an essentially oceanic distribution and occur northwards from Cabo Catoche. The third group included 10 stations, most of which were located westward from the Campeche Sound and another one in the Yucatan Channel. In these stations F. enflata was the domi- nant species and the Simpsons index reached its highest value (0.683). The fourth group included one station located in the upwelling zone, were the dominance index has its lowest value and S. serratodentata was the do- minant species. The fifth group included coastal stations where F. enflata was the dominant species and the Simpsons index reached high values. The most important characteristics of the study area during this period we- re: 1. Two distinct zones. The Campeche Sound in the Western part of the area and the Northern coastal stations, where F. enflata was the dominant species and the Simpsons dominance index reached its highest values, and the oceanic Northern zone off the Yucatan Peninsula where F. enflata had low abundance and there was a hig- her abundance and diversity of other chaetognath species. 2. F. enflata, S. tenuis, F. hispida and K. subtilis we- re the dominant chaetognath species.

4 citations


Journal ArticleDOI
TL;DR: Apogonalia imitatrix represents the first report of the species for Puerto Rico, and may be potential vectors of Xf in plantings of coffee, Coffea arabica L., in Puerto Rico.
Abstract: Xylella fastidiosa (Xf) is a xylem-limited bacterium that is the causal agent of coffee leaf scorch (CLS) in Central America. The purpose of this research was to survey potential vectors of Xf in plantings of coffee, Coffea arabica L., in Puerto Rico. These surveys were conducted from June to November 2006 on four farms, located in the municipalities of Yauco, Juana Diaz and Adjuntas. Insects were collected at each site at 15-day intervals. The 7,423 individuals collected belonged to five families and 12 species. Cicadellidae was the primary family in both number of species and number of individuals. Indexes of dominance, abundance, frequency and constancy showed Agallia pulchra, Apogonalia imitatrix, Caribovia coffeacola and Hortensia similis to be the predominant species. Indexes also showed significant differences among locations, with higher diversity and equitability on Yauco farms, and higher dominance in Adjuntas. Of the four dominant species, Apogonalia imitatrix, C. coffeacola and H. similis are all xylem fluid feeders, and thus may be potential vectors of Xf. Apogonalia imitatrix represents the first report of the species for Puerto Rico.

3 citations


Journal ArticleDOI
TL;DR: The most common species were Psarocolius montezuma, Ramphocelus passerinii (Passerini's Tanager), and Oryzoborus funereus (Thick-billed Seed-Finch).
Abstract: Southern Caribbean avifauna associated with altered ecosystems in Limon, Costa Rica. The Caribbean coast of Costa Rica, one of the areas with higher bird species richness in the country, is the main migratory route in Central America. We sampled the coast with visual counts (April-October 2002) and counted 1 639 individuals of 123 species in 14 sample sites from Moin to Cahuita. The most common species were Psarocolius montezuma (Montezuma Oropendola), Ramphocelus passerinii (Passerini's Tanager) and Oryzoborus funereus (Thick-billed Seed-Finch). Most were in cattle land with isolated trees, followed by rivers and streams and the logged forest. Penshurt had the highest relative abundance, followed by Miravalles and Tuba Creek; the site with the lowest relative abundance was Tomatal. A cluster model indicated significant differences in avifauna composition. Pastures with trees, gardens, and mixed stands were the most diverse and had more birds. Vulnerable forest species occur in these forest remnants that are important for their conservation.

1 citations