Patterns Of Species Accumulation Research Articles

Spatial scaling of plant and bird diversity from 50 to 10,000\xa0ha in a lowland tropical rainforest

While there are numerous studies of diversity patterns both within local communities and at regional scales, the intermediate scale of tens to thousands of km2 is often neglected. Here we present detailed local data on plant communities (using 20 × 20 m plots) and bird communities (using point counts) for a 50 ha ForestGEO plot in lowland rainforest at Wanang, Papua New Guinea. We compare these local diversity patterns with those documented in the surrounding 10,000 ha of lowland rainforest. Woody plant species richness was lower within 50 ha (88% of 10,000 ha richness), even when both were surveyed with identical sampling effort. In contrast, bird communities exhibited identical species accumulation patterns at both spatial scales. Similarity in species composition (Chao-Jaccard) remained constant while similarity in dominance structure (Bray–Curtis) decreased with increased distance between samples across the range from < 1 to 13.8 km for both plant and bird communities. The similarity decay was more rapid in plants, but in both cases was slow. The results indicate low to zero beta-diversity at the spatial scale represented here, particularly for birds but also for woody plants. A 50 ha plot provided a highly accurate representation of broader-scale diversity and community composition within 10,000 ha for birds, and a relatively good representation for woody plants. This suggests potential for wider generalization of data from ForestGEO plots which are almost always locally unreplicated, at least for those in lowland tropical forest.

Reactive oxygen species accumulation patterns of alfalfa root nodules identified using an optimized method.

Reactive oxygen species accumulation patterns of alfalfa root nodules identified using an optimized method.

Greater tree species richness in eastern North America compared to Europe is coupled to denser, more clustered functional trait space filling, not to trait space expansion

AbstractAimDetermine if differences in species richness between currently climatically similar regions correlate to dissimilarities in functional diversity.LocationEurope and eastern North America.Time periodNeogene and Quaternary.Major taxa studiedTemperate trees of Europe and eastern North America.MethodsUsing classic functional traits defining distinct ecological strategies, we described the trait spaces of European and eastern North American tree floras. The trait space of each region was described based on the occupied area, species accumulation pattern, and the trait‐space size, dispersion and clustering. We then evaluated if the species richness differences between these two climatically similar regions correlate to dissimilarities in both occupied areas and species accumulation patterns; as well as differences in the trait‐space size, dispersion and clustering.ResultsDifferences in species richness between climatically similar regions do not necessarily result in functional dissimilarities. Regardless of eastern North American species having a larger trait‐space, occupied areas and species accumulation patterns converged. Although in both regions species clumped towards the trait‐space centroid, we observed statistically significant differences between Europe and eastern North America in the dispersion and clustering but not in size of the trait space. Moreover, traits from species in genera still present in eastern North America but lost from Europe during the Neogene and Quaternary were fully contained within the currently occupied European trait space.Main conclusionsPositional convergence between European and eastern North American trait spaces suggests that this species richness anomaly does fully translate to the functional space. Our results suggest that species accumulation within a region occurs within a climatically restricted trait space, and not via trait‐space expansion. Moreover, the consistent aggregation of species towards the trait‐space centre aligns with the idea of a directional section towards a generalized morphology, which might provide the best way to interact with a broad array of environmental conditions.

When the species–time–area relationship meets island biogeography: Diversity patterns of avian communities over time and space in a subtropical archipelago

AbstractAimThe species–area (SAR) and species–time relationships (STR) are of vital importance in community ecology. Previous studies suggest that a unified, general species–time–area relationship (STAR) may hold, with non‐independent scaling of richness across space and time. Most STAR studies to date have considered species accumulation curves in relatively homogeneous habitats. Here, we test the generality of the STAR in an island system and assess how factors other than area influence species richness, accumulation and turnover through time.LocationThousand Island Lake, China.MethodsWe surveyed bird communities on 36 islands using line transects, and calculated annual species richness of breeding birds from 2007 to 2015. We built island STAR models at island (island STAR; ISTAR) and transect levels (local community–time–area relationship; LCTAR). We employed partial correlations and multiple regressions to examine potential influences of island attributes other than area (i.e. isolation, edge effect and habitat richness) on slopes of STRs.ResultsISTAR and LCTAR models explained 88.8% and 83.1% of total variance, respectively, and both models have a negative space–time interaction. Richness scales comparably in space and time, for both whole‐island and transect‐level analyses. The partial correlation analysis showed that distance to mainland and perimeter‐to‐area ratio are significantly positively correlated with the time scalar (w), and habitat richness and w are negatively correlated. Multiple regression models identify perimeter‐to‐area ratio as particularly influential.Main conclusionsThe STAR pattern generalized to an island system where species turnover is high, indicating an interdependency of time and space in determining species richness. Islands have attributes other than area that influence patterns of species accumulation and turnover through time. Ecologists should consider the interdependence of space and time when characterizing species richness patterns.

Biogeography and diversification rates in hornworts: The limitations of diversification modeling

AbstractHornworts comprise ca. 220 species and are among the oldest landplant lineages, even though their precise phylogenetic position remains unclear. Deep within–hornwort divergences, highly uneven species numbers per genus, and the assumed high stem age together suggest a history of changing diversification (i.e., speciation minus extinction) rates. To study the geographic distribution of modern hornworts and their patterns of species accumulation, we generated a mitochondrial and plastid DNA matrix for 103 species representing all major groups and then applied molecular–clock dating, using a different calibration approach than in earlier work. We used the BAMM software to fit rate–variable and constant–rate birth–death diversification models to the dataset, and we also inferred ancestral areas to a time depth of 55 Ma (Early Eocene). We analyzed diversification rates for all hornworts and separately for species–rich subclades. Under BAMM's variable–rates model (which fits the data better than a constant–rate birth–death model, but still assumes that each species has the same speciation and extinction probability regardless of its age), hornworts have gradually increasing rates of speciation and a constant background extinction rate. No shifts in diversification rate could be detected. The implausible finding of a constant background extinction rate illustrates the limitations of diversification modeling especially as regards extinction rates.

Chironomidae (Diptera: Insecta) in oceanic islands: New records for the Azores and biogeographic notes

Oceanic islands freshwater systems are unique due to their volcanic origin, oceanic situation, catchment morphology and the presence of distinct freshwater communities when compared with continental systems. This study provides an update of Azorean chironomid fauna records, distribution data and includes biogeographical comments, based on collections covering a range of freshwater habitats on several islands over 2005 to 2008. Island species area-relationships or ISAR was performed as a descriptive model for species accumulation patterns in each island in relation to their area. Six new chironimid species records are given for the Azores archipelago: Orthocladiinae: Orthocladius (Eudactylocladius) fuscimanus (Kieffer, 1908), Pseudo- rthocladius (Pseudorthocladius) curtistylus (Goetghebuer, 1921), Synorthocladius semivirens (Kieffer, 1909), Parachaetocladius abnobaeus (Wulker, 1959); Chironominae: Chironomus (Chironomus) annularis (Meigen, 1818), Parachironomus tenuicaudatus (Malloch, 1915). As a result, the Azorean chironomid fauna has in- creased from 38 to 44 species, spread across 33 genera. Most recorded chironomids are primarily of western Palaearctic origin; Nearctic, Oriental and Neotropical regions are comparatively poorly represented. A check- list is provided, incorporating and updating previous records. Chirononidae distribution pattern among the islands is analyzed and island species area-relationship (ISAR) analyses, performed to provide a descriptive model for species accumulation patterns in each island, indicated a positive correlation between species rich- ness (number of species) and the area of the Azorean islands, supporting MacArthur and Wilson 's equili- brium theory of island biogeography. Chironomidae could be promising for searching candidate bioindicators to answer the demand of Water Frame Directive.

Patterns of Species Richness at Varying Scales in Western Kenya: Planning for Agroecosystem Diversification

Agroforestry tree domestication research is geared at promoting diversification of on-farm tree species composition. A survey was conducted in western Kenya with the objective of exploring possibilities for diversification for a particular agroecosystem, involving a complete tree census, tree measurement and collection of ethnobotanical information in 201 small-scale farms. Various approaches to landscape diversification were explored, including random distribution of trees to increase alpha richness and species richness at higher scales in the landscape, and random distribution of species composition over villages to increase the average richness of villages. The results showed that random distribution would result in increments of average species richness in the landscape, without requiring increments of total and average abundance. A new, fast and exact method of calculating site-based species accumulation curves was presented. The method yielded results that were extremely close to classical algorithms using 10,000 randomisations. Four use-groups (beverage, fodder, charcoal and soil fertility enhancement) were identified as use-groups with alpha richness smaller than one species, but only beverage and fodder had lowest richness at all scales (fruit and construction wood joined the four use-groups of lowest average species richness at higher scales in the landscape). The novel approaches used in this study could be used in future biodiversity studies on species accumulation patterns, or on spatial distribution patterns of species richness in a landscape.

DIVERGENT TIMING AND PATTERNS OF SPECIES ACCUMULATION IN LOWLAND AND HIGHLAND NEOTROPICAL BIRDS

Late Pliocene and Pleistocene climatic instability has been invoked to explain the buildup of Neotropical biodiversity, although other theories date Neotropical diversification to earlier periods. If these climatic fluctuations drove Neotropical diversification, then a large proportion of species should date to this period and faunas should exhibit accelerated rates of speciation. However, the unique role of recent climatic fluctuations in promoting diversification could be rejected if late Pliocene and Pleistocene rates declined. To test these temporal predictions, dateable molecular phylogenies for 27 avian taxa were used to contrast the timing and rates of diversification in lowland and highland Neotropical faunas. Trends in diversification rates were analyzed in two ways. First, rates within taxa were analyzed for increasing or decreasing speciation rates through time. There was a significant trend within lowland taxa towards decreasing speciation rates, but no significant trend was observed within most highland taxa. Second, fauna wide diversification rates through time were estimated during one-million-year intervals by combining rates across taxa. In the lowlands, rates were highest during the late Miocene and then decreased towards the present. The decline in rates observed both within taxa and for the fauna as a whole probably resulted from density dependent cladogenesis. In the highlands, faunawide rates did not vary greatly before the Pleistocene but did increase significantly during the last one million years of the Pleistocene following the onset of severe glacial cycles in the Andes. These contrasting patterns of species accumulation suggest that lowland and highland regions were affected differently by recent climatic fluctuations. Evidently, habitat alterations associated with global climate change were not enough to promote an increase in the rate of diversification in lowland faunas. In contrast, direct fragmentation of habitats by glaciers and severe altitudinal migration of montane vegetation zones during climatic cycles may have resulted in the late Pleistocene increase in highland diversification rates. This increase resulted in a fauna with one third of its species dating to the last one million years.

DIVERGENT TIMING AND PATTERNS OF SPECIES ACCUMULATION IN LOWLAND AND HIGHLAND NEOTROPICAL BIRDS

Late Pliocene and Pleistocene climatic instability has been invoked to explain the buildup of Neotropical biodiversity, although other theories date Neotropical diversification to earlier periods. If these climatic fluctuations drove Neotropical diversification, then a large proportion of species should date to this period and faunas should exhibit accelerated rates of speciation. However, the unique role of recent climatic fluctuations in promoting diversification could be rejected if late Pliocene and Pleistocene rates declined. To test these temporal predictions, dateable molecular phylogenies for 27 avian taxa were used to contrast the timing and rates of diversification in lowland and highland Neotropical faunas. Trends in diversification rates were analyzed in two ways. First, rates within taxa were analyzed for increasing or decreasing speciation rates through time. There was a significant trend within lowland taxa towards decreasing speciation rates, but no significant trend was observed within most highland taxa. Second, fauna wide diversification rates through time were estimated during one-million-year intervals by combining rates across taxa. In the lowlands, rates were highest during the late Miocene and then decreased towards the present. The decline in rates observed both within taxa and for the fauna as a whole probably resulted from density dependent cladogenesis. In the highlands, faunawide rates did not vary greatly before the Pleistocene but did increase significantly during the last one million years of the Pleistocene following the onset of severe glacial cycles in the Andes. These contrasting patterns of species accumulation suggest that lowland and highland regions were affected differently by recent climatic fluctuations. Evidently, habitat alterations associated with global climate change were not enough to promote an increase in the rate of diversification in lowland faunas. In contrast, direct fragmentation of habitats by glaciers and severe altitudinal migration of montane vegetation zones during climatic cycles may have resulted in the late Pleistocene increase in highland diversification rates. This increase resulted in a fauna with one third of its species dating to the last one million years.

Temporal Patterns of Species Accumulation in a Survey of Lepidoptera in a Beech-Maple Forest

One of the most significant challenges to insect conservation is lack of information concerning species diversity and distribution. Because a complete inventory of all species in an area is virtually impossible, interest has turned to developing statistical techniques to guide sampling design and to estimate total species richness within a site. We used two such techniques, diversity partitioning and non-parametric richness estimation, to determine how variation in sampling effort over time affected species accumulation for a survey of Lepidoptera in an old-growth beech-maple forest. Temporal scaling of sampling effort had significant effects on two measures of species diversity. Increases in species richness were primarily driven by changes in species occurrences with season, while Shannon diversity was largely determined at the scale of individual sampling units (i.e. by spatial effects). Variation in sampling effort affected the values of the two most widely regarded richness estimators (ICE and Chao 2); neither diversity estimator achieved stable values across a range of sampling efforts. Even after 52 trap-nights and accounting for seasonality, rare species (singletons and uniques) remained a significant component of the moth community. To the extent that moth communities in other forest systems are similarly comprised of many rare species, non-parametric richness estimators should be expected to yield variable estimates with increased effort and should only be used to provide a minimum benchmark for predicting the number of species remaining to be sampled. Our results suggest the best strategy for a short-term survey of forest Lepidoptera should emphasize spreading sampling intervals throughout a given year rather than focusing on intensive sampling during a short time period or prolonged sampling over many years.

Quantitative floristics as a tool for the assessment of plant diversity in Tuscan forests

The results of a floristic survey in six forests owned and managed by the regional administration of Tuscany are reported in this paper. These forests are undergoing a monitoring program, which includes biodiversity as one of the status indicators. Vascular plants are used as indicator species group to quantify biodiversity and they are assessed by means of quantitative floristics. This approach involves the collection of floristic information on the basis of a sampling design. Floristic and structural data were collected in 109 plots, each 400 m 2 large, and analysed at both the plot and forest scales. At the plot scale, species richness was found to be unimodally related to elevation and negatively related to tree stem density and total basal area. At the forest scale, the six forests differed in their patterns of species accumulation, with the highest number of species for a given number of sites sampled observed in the intermediate elevation forests. The analysis of the life-form spectrum showed, for both the plot and forest scales, a decreasing importance of the relative abundance of phanerophytes and an increasing importance of the relative abundance of hemicriptophytes in relation to elevation. The use of the approach adopted for future monitoring is also discussed.

Community assembly through adaptive radiation in Hawaiian spiders.

Communities arising through adaptive radiation are generally regarded as unique, with speciation and adaptation being quite different from immigration and ecological assortment. Here, I use the chronological arrangement of the Hawaiian Islands to visualize snapshots of evolutionary history and stages of community assembly. Analysis of an adaptive radiation of habitat-associated, polychromatic spiders shows that (i) species assembly is not random; (ii) within any community, similar sets of ecomorphs arise through both dispersal and evolution; and (iii) species assembly is dynamic with maximum species numbers in communities of intermediate age. The similar patterns of species accumulation through evolutionary and ecological processes suggest universal principles underlie community assembly.

Predictions of Mammal Diversity on Four Land Masses

Knowledge about the number of living species is fundamental to the practice of conservation biology, but we are far from knowing the number of species even for relatively well‐known groups such as mammals. We analyzed a database that contained information on the year of description, distribution, size class, and taxonomic order of each known mammalian species. Our goal was to predict the size class, order, and number of mammalian species on each of four land masses—America, Eurasia, Africa, Oceania. We constructed cumulative functions of species described versus year of description, and we fitted a logarithmic model to calculate instantaneous rates of species description in 1992 and 2032 and to estimate the number of species to be described in each group in the 40‐year interval. Africa and Eurasia had the highest absolute number of species today and the greatest number of species expected to be described in species‐rich orders (except for Rodentia, in which the highest number of known and expected species was in the American land mass). Per unit area, Oceania had the highest number of known species and the greatest number of species expected to be described. Our estimates, based on the historical patterns of species accumulation, place the total number of mammalian species in the year 2032 at 4875, which is 247 more than in 1992. The majority of the new species will be small (&lt;100 g) and will be in the orders Insectivora, Chiroptera, and Rodentia. Our analyses will help identify particular groups and land masses for which field surveys, conservation efforts, and taxonomic study deserve particular attention.