Spatial and temporal analysis of α, β and γ diversities of bats in a fragmented landscape

We test a strategy for analyzing species richness in a landscape. This strategy is based on the joint analysis of (local), (turnover) and (landscape) diversities. We assessed the spatial and temporal relations among , and diversity of bats (Phyllostomidae and Mormoopidae) in a tropical landscape. In a spatial dimension, diversity depends on the diversity of the most species-rich community. The value of spatial diversity between habitats was very low. A high diversity was found in a cornfield, which may be attributed to the reduced extent of the field (compared with a more extensive field) that allows the arrival of individuals from nearby rich communities. In a temporal dimension, within habitat cumulative richness over sampling period may be considerably different from the average richness. These differences are attributed to temporal turnover during short time intervals. Therefore, cumulative richness may be viewed as the temporal equivalent of within-habitat diversity, which results of both average and temporal turnover. We discuss, which value must be taken as an estimate of habitat species richness, the average or the cumulative , and the implications that this decision can have in the evaluation of biodiversity.     

Evolution of incompatibility systems in plants: Complementarity and the mating locus in flowering plants and fungi

Summary The restriction of sexual pairing by a specificity gene is considered to be an ancient development in the plant kingdom. The diversity and general parallelism of incompatibility systems seen amongst the phyla at the present time can be rationalized in terms of the association of various derived forms of the ancestral specificity unit with differing spectra of accessory factors controlling sexual physiology in the different phyla. Sexual morphogenesis has become divided into distinct phases under the control of complementary genes. These phases are initiated by a regulatory system of Co-ordinator genes which control the order in which groups of morphogenetic genes are expressed during development. The entire sexual cycle will be completed only if all the complementary groups are activated in the appropriate sequence. The present article discusses essential features of the evolution of the breeding locus in different phyla. These features are consistent in themselves with the present data and are not dependent on the proposed ancient origin of the specificity gene.The above hypothesis throws light on the (1) evolution of the complex mating loci in flowering plants and fungi; (2) evolution of complementary incompatibility and heteromorphic incompatibility in flowering plants; (3) anomalous cross-compatibility behaviour of mutants in the fungus Schizophyllum commune; (4) nature of homothallism in higher fungi; (5) mode of origin of new functional self-incompatibility alleles; and (6) homogenic and heterogenic incompatibility.     

Avian community structure along elevational gradients in the northeastern United States

Summary Breeding birds were censused along four elevational gradients in the Adirondack Mountains, New York, and the Green Mountains, Vermont. The bird communities of the four gradients were basically similar in species composition, richness and amplitude patterns. Three measures of species diversity decreased with increasing elevation. Low-elevation communities contained higher proportions of rare species and the relative abundances conformed to the broken-stick distribution. At higher elevations the communities showed greater dominance and the dominance-diversity curves approached geometric series. The species characteristic of high-elevation communities had the broadest altitudinal distributions.The upper and lower distributional limits of most species were independent of one another except at ecotones where marked changes in vegetation structure occurred. On each mountain, slightly more than half of the species limits coincided with ecotones. This is a significantly greater proportion than has been found in similar studies of tropical forest bird communities. In further contrast to tropical communities, we found no convincing cases of altitudinal competitive exclusion between species. Interspecific competition in the past seems to have been translated primarily into differences in habitat selection by temperate forest birds.Many of the differences between temperate forest breeding bird communities and tropical ones can be understood in terms of the migratory nature of most of the temperate species and the lower species richness in temperature forests.     

Biodiversity ‘hotspots’, patterns of richness and endemism, and taxonomic affinities of tropical Australian sponges (Porifera)

Hotspots of biodiversity (taxonomic richness, endemism, taxonomic affinities between communities) at small (), medium () and larger () scales of diversity were examined for marine sponge populations throughout tropical and subtropical Australia, with the faunas of Vanuatu, Palau and Thailand used as outgroups for comparison. Spatial and numerical (ordination) models and hierarchic classifications delineated 37 and 13 scale faunas from 1343 investigated localities using a pool of 2324 species. The Australian taxonomic literature was ignored completely to avoid the many still unresolved taxonomic problems and to allow equal treatment of collecting localities. Richness and endemism varied considerably between marine areas, for species and genera at all spatial scales, with gradients strongly corroborated by hierarchic taxonomic relationships between faunas. Richness and endemism were equally effective indicators of biodiversity hotspots, whereas species-level vs. genus-level data produced differing patterns, with the latter substantially underestimating biodiversity and marine area relationships, and consequently a poor 'surrogate for species data. Patterns of taxa shared between adjacent areas were more informative than richness and endemism data alone, as they more accurately reflect the processes in these areas. Latitudinal gradients in sponge diversity were not evident, whereas various environmental factors were prominent at scales and biogeographic factors were prominent at and scales of diversity. An example of a small () scale diversity fauna revealed substantial spatial heterogeneity (mean of 41 spp/locality, 33% apparently endemic, and a total fauna of 226 spp) containing few ubiquitous species (40% or 78 spp), with adjacent reefs having relatively low faunal similarity (mean 33%). Faunas at the medium () scale of diversity were less heterogeneous (mean 127 spp/region, 27% apparently endemic to a particular region, with a total fauna of 2324 spp), containing a significantly larger dataset (829 spp) found in >1 region to assess taxonomic affinities. At the larger () scale of diversity faunas were far more heterogeneous (mean 263 spp/region, 47% apparently endemic to a particular region) containing a smaller dataset (only 588 spp or 26% of the fauna with >1 species/region) to assess taxonomic affinities. Consequently, sponge faunas at the and scales of diversity are ineffective and inappropriate as biodiversity models, respectively, with scale diversity also less relevant as a practical tool for marine resource management and marine area conservation.     

Patterns of floristic diversity in semi-natural coastal vegetation of Lebanon and implications for conservation

The current understanding of the status of the vegetation in Lebanon is largely derived from herbarium data and associated floristic studies produced by early 20th century field botanists. In common with other areas in the Mediterranean, the Lebanese coastline is highly threatened by unregulated development, yet current patterns of species richness along the Lebanese coastal zone are little studied. The objective of this study was to assess the floristic richness of the Lebanese coastal zone and to provide baseline information for conservation planning. For this purpose, permanent sample plots (6m×100m) were established in 26 selected vegetation communities in coastal habitats. Monthly field collections of plant specimens were undertaken between October 1999 and July 2000. A total of 441 species were collected and identified. None of the recorded species are currently considered globally threatened, but two are Lebanese endemics (Matthiola crassifolia Boiss. & Gaill., Origanum ehrenbergii Boiss.). Species richness varied between communities, ranging from six species in a littoral limestone pavement community to 113 in an abandoned terrace community. The similarity between communities, based on Sorensen indices, was low and a large number of species were recorded only once. Cluster analysis showed a grouping of different communities within locations in some instances and the clustering of similar community types regardless of location in others. Species richness in riparian and littoral communities consisted mostly of habitat non-specific species. The low community similarity, patchy species distribution, and predominance of habitat non-specific species all point to the need to complement in situ conservation measures with ex situ conservation.     

Community assembly along a species pool gradient: implications for multiple-scale patterns of species diversity

Various ecological processes influence patterns of species diversity at multiple spatial scales. One process that is potentially important but rarely considered is community assembly. I assembled model communities using species pools of differing size to examine how the history of community assembly may affect multi-scale diversity patterns. The model contained three scales at which diversity could be measured: local community, metacommunity, and species pool. Local species saturation occurred, as expected from the competition and predation built in the model. However, local communities did not become resistant to invasions except when the species pool was very small. Depending on dispersal rate and trophic level, the larger the species pool, the harder it was to predict which species invades which local community at a given time. Consequently, local-community dissimilarity maintained by assembly history increased linearly with pool size, even though local diversity was decoupled from pool size. These results have two implications for multi-scale diversity patterns. First, assembly history may provide an explanation for scale-dependent relationships between local and regional diversity: assembly causes the relationship to be curvilinear at one scale (local community), while linear at another (metacommunity). Second, assembly history influences how -diversity is partitioned into - and -diversity: assembly causes the relative contribution of to increase with pool size. Overall, this study suggests that community assembly history interacts with species pool size to regulate multi-scale patterns of species diversity.     

The expression of Na+/K+-ATPase β-subunit cRNA injected into Xenopus oocytes is affected by coinjection with α-subunit cRNA

The cRNA for Torpedo californica Na⁺/K⁺-ATPase -subunit (cRNA) was injected into Xenopus oocytes alone or with the cRNA for the Na⁺/K⁺-ATPase -subunit (cRNA). When cRNA was injected alone, the amount of the -subunit that accumulated in oocytes increased with increasing amounts of injected cRNA. When cRNA and cRNA were injected simultaneously, less -subunit accumulated than when cRNA was injected alone, whereas the Na⁺/K⁺-ATPase activity increased markedly. The decrease in the accumulation of the -subunit was dose-dependent upon the cRNA. The mutant -subunit unable to assemble with the -subunit accumulated in oocytes independently of cRNA, suggesting that post-translational control mechanisms may serve to reduce the accumulation of the -subunit.This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sports and Culture of Japan (No. 05259226, No. 06454149).     

Distribution of Ground-dwelling Arthropods in Tropical Countryside Habitats

The future of biodiversity depends to a great extent on the conservation value of human-dominated and semi-natural habitats. In a mixed agricultural landscape in southern Costa Rica, we compared the richness and composition of terrestrial arthropod communities occurring in three habitat types along a gradient of increasing disturbance: in a large (227ha) forest fragment, small (3.8–5.3ha) forest fragments, and sun coffee (1–3ha) plantations. Pitfall trap sampling revealed decreasing morphospecies richness with increasing disturbance. Moreover, the number of species unique to a habitat type was lower in the smaller forest fragments and the coffee sites. We found significant changes in community composition associated with habitat at the levels of order (all arthropods), family (beetles), and morphospecies (carabids, scarabs, and ants). We identified no significant correlation of richness among the taxonomic orders, meaning these taxa are unable to serve as biodiversity indicators (for each other or for all arthropods) in the study region. Arthropod diversity presently found in countryside habitats is certainly lower, and perhaps less sustainable, than that of the extensive forested habitats fragmented < 40 years ago. It nonetheless remains substantial, suggesting a conservation opportunity in human-dominated landscapes of the tropics.     

West African rivers as biogeographic islands: species richness of fish communities

Summary Some factors influencing the species richness of West African fish communities were studied in a sample of 26 rivers using four habitat and hydrologic variables. Analysis of a larger sample of 39 rivers showed that species richness was positively related to area. A power function with an exponent of 0.32 gave the best fit. As the surface area used was that of the catchment area and not that (unknown) of the river, the biological significance of this relationship and the possibilities of comparison were limited. Ridge regression analysis and forward stepwise selection indicated that a model that explained ln(species richness) as a function of ln(mean annual discharge) and ln-(catchment surface area) was best, accounting for 90% of the variance of the dependent variable. The combination of surface area and discharge was presumed to act through the volume of water available for the fishes and habitat productivity. Habitat diversity, measured by the diversity of the terrestrial vegetation covering the catchment area, had no significant positive effect when surface area was used in the regression. Rivers (islands) should have fewer species than tributaries of similar size since, for fishes within a river system (continent), there is free circulation between all its branches. The model derived from the river data underestimated the species richness of a sample of 11 tributaries. This was compatible with the hypothesis of higher population extinction rates in insular biotopes. The residuals of the linear model did not show random geographical distribution; the rivers in some areas had more species than expected. The possibility that historical factors, especially Quaternary climatic variations, might cause this distribution is discussed.     

Intersectional cytoplasmic hybrids in Nicotiana

Summary Cybrid plants having the nuclear genomes of one species and either or both plastomes and chondriomes of another species were obtained by fusing protoplasts of Nicotiana sylvestris, as recipients, with X-irradiated protoplasts of N. rustica as donors of chloroplasts and mitochondria. Forty-nine flowering plants, derived from 28 calli, were analysed. As expected, they all had N. sylvestris (i.e. recipients) morphology. Chloroplast DNA restriction patterns indicated that 8 and 41 plants had N. rustica and N. sylvestris plastomes, respectively. Some of the plants with either type of plastomes produced sterile pollen but none showed anther malformation typical to alloplasmic male sterility. Chondriome identification by mitochondrial DNA restriction analysis of cybrid plants revealed only restriction patterns which were either similar or identical to those of N. sylvestris while no cybrids with N. rustica restriction patterns were detected.     

On the meaning and measurement of nestedness of species assemblages

Nestedness of species assemblages occurs when thebiotas of sites with lower numbers of species tend to be subsets of the biotas at richer sites. We develop new quantitative and statistical techniques for measuring, testing, and comparing nestedness, and apply these methods to data from the literature. Significantly nonrandom nestedness was present in all 27 assemblages examined, and tended to be stronger in systems dominated by extinction, such as landbridge islands. Sets of assemblages that were very strongly nested were more likely to have greater species richness on one or a few large sites than on several smaller sites of equivalent total area — that is, to fall toward the single large side of the Single Large Or Several Small (SLOSS) continuum. Our analysis indicates that nestedness, when quantified as a single number for a presence-absence matrix, measures community-wide differences in incidence (the frequency of occurrence or distribution of species). Factors that lead to consistent differences among species in immigration or extinction rates cause strong patterns of nestedness of species assemblages. Nestedness is negatively related to beta diversity: nestedness is low when beta diversity is high, and vice versa. Conservation managers will thus seek to minimize nestedness and the development of nested structure in systems of nature reserves.     

The cloned β-mannanase gene from alkalophilic Bacillus sp. AM-001 produces two β-mannanases in Escherichia coli

The gene encoding -mannanase was cloned from alkalophilic Bacillus sp. AM-001 into Escherichia coli JM 101 by inserting HindIII-generated DNA fragments into the HindIII site of pUC19. A 2.0 kb XbaI-PstI fragment of the donor strain DNA was sufficient for -mannanase synthesis. The amount of -mannanase expressed in E. coli JM101 harboring pMAH3 (containing a 2.4 kb XbaI-HindIII fragment) was about 24% of the activity produced by the donor strain. E. coli JM101 harboring pMAH3 was found to produce two enzymatically active -mannanases (A and B). These two -mannanases were purified to electrophoretically homogenous states. The -mannanase A had enzymatic properties similar to those of the -mannanases M-I and M-II produced by alkalophilic Bacillus sp. AM-001, and the -mannanase B resembled its -mannanase M-III. In contrast to -mannanase production in the donor strain, that in E. coli was not inducible. The NH₂-terminal amino acid sequences from amino acid 1 (Asn) to 9 (Gln) of the three -mannanases purified from alkalophilic Bacillus sp. AM-001 coincide with those from amino acid 4 (Asn) to 12 (Gln) of the two -mannanases purified from E. coli transformant.     

A kinetic analysis of the facultative photoperiodic response in Amaranthus retroflexus L.

The ontogenetic change taking place in the facultative photoperiodic response of A. retroflexus to inductive short-day (SD) conditions was studied by exposing plants to continuous induction after different initial exposures to long-days (LD), and comparing the kinetics of their developmental responses (cumulative number of plants with reproductive apices, flowering stage, and height of the apical dome). As the plants progressed from emergence to autonomous flowering (i.e., in non-inductive conditions), their response to continuous induction became progressively more rapid. Reproductive development was initiated following a progressively shorter lag-phase after the start of induction, but its subsequent rate remained unchanged. Until the onset of reproductive development, the undifferentiated upper part of the shoot apex (apical dome) elongated much more rapidly in SD than in LD. However, in both cases reproductive development was initiated when the apex had elongated to about the same extent, after which its elongation accelerated considerably, but to similar rates in both photoperiods. The data indicate that progress towards reproductive development takes place in inductive (SD), as well as in non-inductive (LD) photoperiods, but one cycle of the latter is as effective as 0.20–0.25 of a cycle of the former. —Plants induced at different stages in ontogeny started to change their subsequent branching pattern (ratio of leafy to leafless branches) as soon as induction was delayed beyond autonomous flowering.Abbreviations LD long-days - SD short-days - RGR Relative Growth Rate     

Diversity of arbuscular mycorrhizal fungi across a fragmented forest in Panama: insular spore communities differ from mainland communities

It is now understood that alterations in the species composition of soil organisms can lead to changes in aboveground communities. In this study, we assessed the importance of spatial scale and forest size on changes in arbuscular mycorrhizal fungal (AMF) spore communities by sampling AMF spores in soils of forested mainland and island sites in the vicinity of Gatun Lake, Republic of Panama. We encountered a total of 27 AMF species or morphospecies, with 17, 8, 1 and 1 from the genera Glomus, Acaulospora, Sclerosystis, and Scutellospora, respectively. At small scales (<100 m²), we found little evidence for spatial structuring of AMF communities (decay of Morisita-Horn community similarity with distance). However, at large spatial scales, we found that the AMF spore community of a mainland plot was more similar to other mainland plots several kilometers (>5) away than to nearby island plots (within 0.7 km). Likewise, most island plots were more similar to other island plots regardless of geographic separation. There was no decay in AMF species richness (number of species), or Shannon diversity (number of species and their spore numbers) either with decreasing forest-fragment size, or with decreasing plant species richness. Of the six most common species that composed almost 70% of the total spore volume, spores of Glomus tsh and G. clavisporum were more common in soils of mainland plots, while spores of Glomus small brown and Acaulospora mellea were more abundant in soils of island plots. None of these common AMF species showed significant associations with soil chemistry or plant diversity. We suggest that the convergence of common species found in AMF spore communities in soils of similar forest sizes was a result of forest fragmentation. Habitat-dependent convergence of AMF spore communities may result in differential survival of tree seedlings regenerating on islands versus mainland.     

Flood disturbance and riparian species diversity on the Colorado River Delta

We investigated the influence of channel migration and expansion on riparian plant species diversity along the lower Colorado River near the United States–Mexico border. Using repeat aerial photography in a GIS we identified and classed areas of low, moderate, and high disturbance frequency caused by channel expansion and migration. Replicate vegetation plots (12m×12m) were sampled in each of the three disturbance classes. One-way ANOVA was used to test for differences in species richness, species diversity (using the Shannon–Weiner Index) and overall percent ground cover of plants between the three disturbance classes. Regardless of disturbance class, plots were dominated by trees or shrubs, especially the non-native Tamarix ramosissima, as well as Pluchea sericea, Baccharis salicifolia and Salix goodingii. Clearly woody species constitute the great bulk of overall species richness, percent ground cover, and species diversity (H) in each disturbance group. No overall statistically significant differences were revealed among the disturbance groups for values of species richness, percent ground cover, or the Shannon–Wiener Index, though paired contrasts of means revealed that total percent ground cover on low disturbance plots was significantly higher than on moderately disturbed plots. Spatial and temporal variability in riparian diversity in the study area appears to hinge on factors other than disturbance frequency such as salt or drought stress. Alternately, our results could be interpreted as suggesting that in the presence of intensive flow regulation, disturbance plays a secondary role to ecological stresses, similar to that demonstrated by others. Intentional flood pulses are advocated as a restorative management strategy for improving plant productivity, management of exotic species (particularly T. ramosissima), and restoration of overall biodiversity.     

Comments on specific categories in flowering plants

The paper offers comments arising from the author's experience as a practising taxonomist on two aspects of what is often called the species problem: the reality of species and species as individuals. Three different meanings of reality are distinguished and discussed in this context: mental reality, biological reality and evolutionary reality. The author holds the view that, on all three definitions, species must be judged to be real. On the argument concerning species as individuals, the opinions ofHull, Ghiselin and others are carefully presented but rejected by the author, who retains the belief that species are classes and not individuals.Dedicated to the memory of JohnS. L. Gilmour.     

The checkerboard score and species distributions

Summary There has been an ongoing controversy over how to decide whether the distribution of species is random — i.e., whether it is not greatly different from what it would be if species did not interact. We recently showed (Roberts and Stone (1990)) that in the case of the Vanuatu (formerly New Hebrides) avifauna, the number of islands shared by species pairs was incompatible with a random null hypothesis. However, it was difficult to determine the causes or direction of the community's exceptionality. In this paper, the latter problem is examined further. We use Diamond's (1975) notion of checkerboard distributions (originally developed as an indicator of competition) and construct a C-score statistic which quantifies checkerboardedness. This statistic is based on the way two species might colonise a pair of islands; whenever each species colonises a different island this adds 1 to the C-score. Following Connor and Simberloff (1979) we generate a control group of random colonisation patterns (matrices), and use the C-score to determine their checkerboard characteristics. As an alternative mode of enquiry, we make slight alterations to the observed data, repeating this process many times so as to obtain another control group. In both cases, when we compare the observed data for the Vanuatu avifauna and the Antillean bat communities with that given by their respective control group, we find that these communities have significantly large checkerboard distributions, making implausible the hypothesis that their species distributions are a product of random colonisation.     

Consequences of harvesting for genetic diversity in American ginseng (<Emphasis Type="Italic">Panax quinquefolius</Emphasis> L.): a simulation study

American ginseng, Panax quinquefolius L., is one of the most heavily traded medicinal plants in North America. The effect of harvest on genetic diversity in ginseng was measured with a single generation culling simulation program. Culling scenarios included random harvest at varying levels, legal limit random harvest and legal limit mature plant harvest. The legal limit was determined by the proportion of legally harvestable plants per population (% mature plants per population). Random harvest at varying levels resulted in significant loss of genetic diversity, especially allelic richness. Relative to initial levels, average within-population genetic diversity (H _e) was significantly lower when plants were culled randomly at the legal limit (Mann–Whitney U=430, p<0.001) or when only mature plants were culled (Mann–Whitney U=394, p<0.01). Within-population genetic diversity was significantly higher with legal limit mature plant harvest (H _e=0.068) than when plants were culled randomly at the legal limit (H _e=0.064; U=202, p<0.01). Based on these simulations of harvest over one generation, we recommend that harvesting fewer than the proportion of mature plants could reduce the negative genetic effects of harvest on ginseng populations.     

Microbial diversity along a sediment detrital particle size gradient

We studied the structural organization of microbial decomposer communities by comparing patterns of genetic complexity over a template defined by site, season and detrital particle size. Epibenthic sediment samples were collected monthly from a Lake Erie coastal wetland and a small woodland stream, and sieved into five fine particulate organic matter (FPOM) size ranges: 1000–500 (500), 500–250 (250), 250–125 (125), 125–63 (63) and 63–38 (38) m. Whole community DNA-DNA hybridizations were used to compare the structural similarity of the microbial communities associated with each sample. Microbial community heterogeneity increased as particle size decreased, and declined from a summer maximum to a late winter minimum. Cluster analysis of hybridization scores partitioned the communities into two groups: one associated with the 500, 250 and 125 m fractions and a second with the 63 and 38 m fractions. The larger particles were easily recognized as comminuted plant detritus; the smaller particles were amorphous, presumably formed through the aggregation of dissolved organic carbon. This disjunction in particle morphology and microbial community diversity that occurs at about 100 m appears to delineate two trophic resources whose origin and fate may be largely independent.     

Fractal geometry and root system structures of heterogeneous plant communities

Above-ground plant growth is widely known in terms of structural diversity. Likewise, the below-ground growth presents a mosaic of heterogeneous structures of differing complexity. In this study, root system structures of heterogeneous plant communities were recorded as integral systems by using the trench profile method. Fractal dimensions of the root images were calculated from image files by the box-counting method. This method allows the structural complexity of such associations to be compared between plant communities, with regard to their potentials for soil resource acquisition and utilization. Distinct and partly significant differences are found (fractal dimension between 1.46±0.09 and 1.71±0.05) in the below-ground structural complexity of plant communities, belonging to different biotope types. The size of the heterogeneous plant community to be examined has an crucial influence on the fractal dimension of the root system structures. The structural heterogeneity becomes particularly evident (fractal dimensions between 1.32 and 1.77) when analysing many small units of a complex root system association. In larger plant communities, a broad variety of below-ground structures is recorded in its entirety, integrating the specific features of single sub-structures. In that way, extreme fractal dimensions are lost and the diversity decreases. Therefore, the analysis of larger units of root system associations provides a general knowledge of the complexity of root system structures for heterogeneous plant communities.