Average Alpha Diversity Research Articles

Biomass temporal stability increases at two spatial scales during secondary succession

Abstract Ecological stability has long been considered to change over succession, but how secondary succession influences the relationship between diversity and temporal stability of biomass production at different spatial scales is poorly understood. We studied changes in plant diversity, functional temporal stability (biomass production) and compositional temporal stability (the latter two are hereafter referred to as functional stability and compositional stability) and explored the stabilizing roles of plant diversity at two spatial scales (small plots of 0.25 m2 and large transects of 1.25 m2) during secondary succession in a subalpine meadow from 2003 to 2010. Our results showed that both plant diversity and functional and compositional stability increased at the small plot scale and large transect scale during secondary succession. As secondary succession proceeded, higher average alpha diversity (i.e. species diversity at the plot scale) led to higher functional and compositional stability at the plot scale by mainly species stability, predominantly contributing to higher functional and compositional stability at the large transect scale. In addition, Simpson‐based beta diversity (i.e. compositional dissimilarity among communities within the same transect), while unaffected by succession, contributed to functional stability at the large transect scale by promoting asynchronous dynamics among communities. Synthesis. Our study highlights the stabilizing effects of plant diversity across the two spatial scales during secondary succession. Our findings provide the first empirical evidence that biodiversity‐mediated effects on ecosystem temporal stability strengthen over successional time, suggesting that the stabilizing effects of biodiversity should be considered across spatial and temporal scales in the face of global changes and biodiversity loss.

Disentangling dimensions of phytochemical diversity: alpha and beta have contrasting effects on an insect herbivore.

Phytochemical diversity is comprised of two main dimensions-the average (alpha) within-plant neighbors or the difference (beta) in the composition of chemicals between plant neighbors. Research, however, has primarily examined the consequences of phytochemical diversity on herbivore performance through a single dimension, even though diversity is multidimensional. Furthermore, the ecological role of phytochemical diversity is not well understood because each of these dimensions exhibits unique biological effects on herbivore performance. Therefore, it has been difficult to tease apart the relative importance of alpha and beta chemical diversities on plant-herbivore interactions. We experimentally manipulated alpha and beta diversities along a chemical gradient to disentangle the relative effects of these dimensions on the performance of a mobile generalist herbivore, Trichoplusia ni (Hübner), using 16 genotypes from the Solanum pennellii introgression lines. First, we found contrasting effects of alpha and beta diversities on herbivore performance. Second, when comparing diversity across and within chemical classes, herbivore performance was reduced when plant neighbors had greater diversity within chemical classes that are biologically inhibiting at higher quantities (i.e., quantitative defenses such as phenolics and acyl sugars). However, herbivore performance was enhanced when plant neighbors had higher levels of chemical classes that are biologically toxic (i.e., qualitative defenses such as alkaloids). Finally, herbivores performed better on plant dicultures compared to monocultures, and performance was positively associated with plant dicultures only when there were high levels of average alpha diversity within plant neighbors. Our results suggest T. ni generalist caterpillars do better when plant neighbors are chemically different because differences provide options for them to choose or to switch between plants to balance chemical uptake. Overall, herbivores interact with a large diversity of plant chemicals at multiple scales, and our results indicate that not all chemical diversity is equal: specific dimensions of phytochemical diversity have unique effects on the dynamics of herbivore performance.

Altitudinal distribution of alpha, beta, and gamma diversity of pseudoscorpions (Arachnida) in Oaxaca, Mexico

In this study, we describe the spatial and temporal variation in the diversity of pseudoscorpions along an altitudinal gradient in Santiago Comaltepec, Oaxaca, Mexico. Four altitudinal levels were selected (150, 989, 2177, and 2990 m a.s.l.). Species were recorded through monthly sampling from April 2016 to April 2017. Alpha and beta diversities were estimated at every altitude, and gamma diversity was calculated for the entire gradient; diversity was then related to temperature and precipitation. The highest species richness was observed at 989 m a.s.l. and the lowest at 2990 m a.s.l. The months with the lowest number of species and specimens were January, March, and April. The highest Shannon index value was observed at 989 m a.s.l. (H′ = 1.724) and the lowest at 2177 m a.s.l. (H′ = 0.692). Gamma diversity was 2.15 and was mainly affected by the average alpha diversity. Alpha diversity was higher during the dry season and was slightly regulated by precipitation. Moreover, higher species replacement was observed in the dry season than in the wet season, which was mainly associated with changes in temperature. Overall, with the increase in altitude, the diversity of pseudoscorpions decreases.

Diversity, structure and natural history of amphibians in the upper Claro River basin, a buffer zone of the National Natural Park Los Nevados, Central Cordillera of Colombia

We present an assessment on composition, diversity and structure of amphibians in three zones along an elevation gradient (2,400–3,000 m) in the Central Cordillera of Colombia. For this purpose, we carried out two field trips in November 2014 and February 2015, covering rainy and dry seasons, respectively. Diurnal (08:00–12:00 h) and nocturnal (18:00–22:00 h) visual encounter surveys were made without spatial restrictions. The diversity for each zone (alpha) and for the entire landscape (gamma) was evaluated by the effective number of species, and the structure of the communities was analyzed by range-abundance curves. The inequality factor for each of the sampling zones was also calculated. A total of 15 species belonging to seven genera and three families were recorded, all of the order Anura. Craugastoridae with 11 species (73.3% of richness) and Pristimantis (eight species) were the most diverse family and genus, respectively. The average alpha diversity per zone was 6.6 effective species, with zone A being the most diverse with eight species. In terms of beta diversity we found 2.5 effective communities at the landscape level, and differences between zones are given by the rare species, while the most abundant ones (e.g., Pristimantis uranobates) are shared between them. It is presumed that the greater diversity of zone A is due to the lower elevation and better state of conservation if compared to the other two zones. Of the total species recorded, three are threatened with extinction: Endangered (Hypodactylus latens, Osornophryne percrassa), and Critically Endangered (Niceforonia adenobrachia). The finding of three yet undescribed species is highlighted.

Does the protection status of wetlands safeguard diversity of macroinvertebrates and birds in southwestern Ethiopia?

Freshwater ecosystems are highly threatened due to increased population growth, thereby affecting biodiversity. The objective of designating an area as ‘protected’ is to reduce habitat degradation and biodiversity loss. However, most protected areas focus on the conservation of the terrestrial environment and its related biodiversity. Little attention is given to the protection of freshwater biodiversity and consequently far less is known on how freshwater biodiversity differs between wetlands with a different protection status. The objectives of this study was to investigate alpha and beta diversity of macroinvertebrates and wetland dependent birds in wetlands with a different protection status and thus a different level of human impact in southwestern Ethiopia. Data on macroinvertebrates, birds, physico-chemical water quality, human disturbance and vegetation cover were collected from 42 sampling sites during dry and wet season of 2015. Besides the calculation of alpha and beta diversity, multiple regression models were used to identify the main drivers of the variation in beta diversity of macroinvertebrates and birds in these wetlands. Our results revealed that the average alpha diversity of both macroinvertebrates and wetland dependent birds was significantly higher in protected wetlands (low overall human disturbance) compared to unprotected wetlands (high overall human disturbance), whereas beta diversity was higher in unprotected wetlands for wetland dependent birds. Turnover contributed more than nestedeness to total beta diversity for both macroinvertebrates and wetland birds in protected and unprotected areas. Human disturbance, water temperature, pH and dissolved oxygen were significantly related to beta diversity of macroinvertebrates, whereas beta diversity of wetland dependent birds was significantly related to vegetation cover, nutrients and chemical oxygen demand. Conservationists should give attention to both alpha and beta diversity of freshwater wetlands in order to conserve wetland biodiversity maximally.

Drivers of symbiont diversity in freshwater snails: a comparative analysis of resource availability, community heterogeneity, and colonization opportunities.

Decades of community ecology research have highlighted the importance of resource availability, habitat heterogeneity, and colonization opportunities in driving biodiversity. Less clear, however, is whether a similar suite of factors explains the diversity of symbionts. Here, we used a hierarchical dataset involving 12,712 freshwater snail hosts representing five species to test the relative importance of potential factors in driving symbiont richness. Specifically, we used model selection to assess the explanatory power of variables related to host species identity, resource availability (average body size, host density), ecological heterogeneity (richness of hosts and other taxa), and colonization opportunities (wetland size and amount of neighboring wetland area) on symbiont richness in 146 snail host populations in California, USA. We encountered a total of 23 taxa of symbionts, including both obligatory parasites such as digenetic trematodes as well as more commensal, mutualistic, or opportunistic groups such as aquatic insect larvae, annelids, and leeches. After validating richness estimates per host population using species accumulative curves, we detected positive effects on symbiont richness from host body size, total richness of the aquatic community, and colonization opportunities. Neither snail density nor the richness of snail species accounted for significant variation in symbiont diversity. Host species identity also affected symbiont richness, with higher gamma and average alpha diversity among more common host species with higher local abundances. These findings highlight the importance of multiple, concurrent factors in driving symbiont richness that extend beyond epidemiological measures of host abundance or host diversity alone.

Alpha Diversity of the Myrmecofauna of the Natural Protected Area Metlac from Fortin, Veracruz, Mexico

Although the State of Veracruz is a megadiverse entity, it has the highest annual deforestation rates. Protected natural areas are considered strategic to preserve local biodiversity. In this paper, composition and alpha diversity of ant assemblages were analyzed in the natural protected area ‘Metlac’ near Fortin, Veracruz, Mexico. Sampling was conducted at four transects using baited pitfall traps and hand-collection. In total 3,204 ant workers belonging to 36 species, 21 genera, 12 tribes, and seven subfamilies were collected. The average alpha diversity was 16 species and no significant differences between recorded richness in each transect were found. Average sampling completeness was above 80%. Locally, Solenopsis geminata and Nylanderia steinheili dominate the epigeous and shrub strata due probably to their biological, behavioral and ecological plasticity that allows them to easily adapt to disturbed environments. This paper shows that for the small area sampled, the relict of tropical semi-evergreen forest is of great biological value despite heavy human intervention and the space-geographic context in which it is found.

Variation in Taxonomic Diversity of the Fish Assemblage Associated with Soft Bottoms in San Ignacio Lagoon, Baja California Sur, Mexico

The San Ignacio Lagoon is one of the largest in the northwest area of Baja California Sur; it is characterized by high levels of commercial fish catch; however the number of investigations related to taxonomic diversity is low. The variation in taxonomic diversity was determined for the assemblage of fish associated with soft bottoms, at 11 locations in a period from spring of 1998 to winter of 1999. Variation in diversity of the soft bottom fish were evaluated considering the taxonomic distance between species, using the indices of alpha, average alpha, beta and gamma diversity, also the indices of taxonomic distinctness (Δ*) and average taxonomic distinctness (Δ+). Bottom trawls were performed using an experimental net to an average depth of 5 meters, between 9:00 to 17:00 hours. 1361 organisms were observed, belonging to 44 species on 35 genera. According to the average alpha, beta and gamma diversity indices, the season with higher value on average alpha diversity was summer, with 6.68 species followed by spring with 5.73 species. In beta´s case the highest value was observed during spring (21.27%) followed by summer (20.18%). Taking gamma in account, the highest values were observed during spring and summer, both seasons with 27 species each. The lowest values observed according to the average alpha beta and gamma indices, was observed during winter season (5.27, 20.18% and 20 species, respectively). In the spatial analysis, the average taxonomic distinctness index (Δ+) show a significant difference (p ≤ 0.05), while taxonomic distinctness index (Δ*) showed no significant difference (p ≥ 0.05). In the temporal analysis both indices showed no difference (p ≥ 0.05).

Assembly of zooplankton communities in newly created ponds

Summary1. The creation or severe disturbance of habitat patches is generally followed by a phase of community (re)assembly. After such an event, the trajectory of community assembly in habitat patches may be highly variable because of stochasticity during the dispersal and colonization process. Conversely, assembly patterns may also be deterministic if communities are shaped by prevalent environmental conditions in the habitat patches (species sorting), or by systematic differences in the dispersal capacities of species.2. In this study, we investigated the pattern of community assembly of zooplankton species in 25 newly created ponds at 13 different sites in Flanders (Belgium). Over a period of three consecutive years, we assessed at what rate and with what frequency species of the regional species pool colonized the newly created ponds. We also studied the development of community structure over time and tested whether the dynamics were consistent across different ponds at the different locations. In addition, we characterized the dynamics of metacommunity features, such as alpha, beta and gamma diversity in clusters of ponds.3. Even within the first year after their creation, the new ponds were rapidly colonized by a small subset of species from the regional species pool (Daphnia obtusa, Chydorus sphaericus and Simocephalus vetulus). These species dominated the cladoceran assemblages during the subsequent years. Other species in the regional species pools were only sporadically able to colonize ponds.4. During the entire study period, we observed no significant shifts in species lists or in the occurrences of species among years. The low incidence of the majority of species may be the result of dispersal limitation or the failure of immigrants to establish due to priority effects exerted by the first colonizers. There was, nevertheless, a consistent change in the relative abundance of species, which was most probably mediated by differences in the hatching time among species influencing species composition in the first year.5. In contrast to expectations, we observed no increase in average alpha diversity (local species richness) and gamma diversity (total richness of entire pond clusters) during the course of the study period. Beta diversity was relatively low from the beginning and remained constant throughout the study period. These deterministic patterns can mainly be attributed to the dominance of the three first colonizing species and the low success rate of other species in colonizing the ponds.

Diversity Comparisons Between Diked and Undiked Coastal Freshwater Marshes on Lake Erie During a High-water Year

The effect of high water on floristic composition and diversity was compared at a diked, managed marsh, and an undiked, unmanaged marsh. Species richness and alpha diversity were determined for Cells A through D at Pipe Creek Wetland (PCW), a restored, managed marsh, and MHD Wetland, an undiked, unmanaged marsh. Both wetlands are located on Sandusky Bay in the western basin in Lake Erie, Ohio. Water levels were unusually high during 1997 when this study was conducted. Thus, the flora of Cells C and D at PCW in 1997 were compared to results from a vegetation survey of these cells conducted in 1994, a low-water year. Values for species richness in 1997 ranged from 25 (Cell A) to 42 (Cell D). Pipe Creek Wetland, and Cell D in particular, had higher species richness than MHD Wetland. Average alpha diversity values in 1997 ranged from 0.95 to 1.34; Cell D had significantly higher alpha diversity than Cell C at PCW and MHD Wetland. Species richness of Cells C and D at PCW declined substantially between 1994 and 1997 and species composition changed considerably. These findings reflect the combined effects of the very different marsh surfaces, hydrologic regimes, and human influences at Pipe Creek and MHD Wetlands. It is suggested that species richness and alpha diversity at Pipe Creek Wetland would be even higher in a low-water year. However, MHD Wetland would not become more diverse if water levels dropped due to the extreme dominance of stress-tolerant, aggressive plant species at MHD.