Patterns Of Invertebrate Diversity Research Articles

Patterns of invertebrate diversity highlight the vulnerability of aquatic and terrestrial ecosystems over a 45-year period

Patterns of invertebrate diversity highlight the vulnerability of aquatic and terrestrial ecosystems over a 45-year period

Invertebrate by-catch from vertebrate pitfall traps can be useful for documenting patterns of invertebrate diversity

There is a pressing need to develop simplified sampling protocols that allow invertebrates to be routinely incorporated into terrestrial faunal surveys for informing conservation planning. This study assesses the usefulness of sampling invertebrate by-catch from standard vertebrate bucket pitfall traps for documenting spatial patterns of terrestrial invertebrates. We compare among-site (N = 78) patterns of species richness and composition of ten invertebrate families (comprising ants, beetles and spiders) captured in vertebrate bucket traps with those captured in two different arrays of invertebrate-specific pitfall traps. For three families (Formicidae, Carabidae and Lycosidae) patterns of richness and composition captured in the vertebrate traps were comparable with those captured in the invertebrate-specific trap arrays. Thus, in some cases, vertebrate traps appeared to be as useful in detecting patterns of invertebrate diversity as were invertebrate-specific traps. Our findings show that sampling invertebrate by-catch from vertebrate bucket traps can be a reliable and robust simplified protocol for documenting biodiversity patterns for some key groups of terrestrial invertebrates. This simplified protocol can take terrestrial invertebrates out of the ‘too-hard basket’ for biodiversity assessment and monitoring, breaking the positive-feedback loop that currently maintains ignorance of invertebrate diversity and distribution and that prevents their inclusion in conservation planning.

Freshwater vertebrate and invertebrate diversity patterns in an Andean-Amazon basin: implications for conservation efforts

The Napo Basin in Ecuador is an important drainage of the Amazon Basin, the most biodiverse ecosystem for freshwater species. At the same time, this basin has conspicuous information gaps on its biodiversity patterns and human threats. Here, we estimated the diversity distribution patterns of freshwater vertebrates and invertebrates in the Napo Basin, as a tool for present and future management and conservation efforts. Also, we assessed the spatial congruence of the diversity patterns observed between aquatic vertebrates and invertebrates. For this, we compiled occurrence records for 481 freshwater vertebrate species (amphibians, birds, mammals, reptiles, and fish), and 54 invertebrate families obtained across an altitudinal gradient of the basin (200–4500 m). Using these occurrence records and environmental variables, we modeled the distribution of each vertebrate species and invertebrate family. Then, we stacked these distributions to build species richness maps for vertebrates, and a family richness map for invertebrates. We found that the most diverse areas for vertebrate species are the lowlands (<600 m), whereas richness of invertebrate families peaks at higher elevations (lower montane forests). Congruence among species richness patterns of the five vertebrate groups was high (r = 0.66), with fish being the best predictor for vertebrates (r = 0.78). However, congruence decreased at higher elevations (r = 0.14), suggesting that specific species or habitat-based approaches should be used in the highlands. Also, we found a high correlation between species and family richness of freshwater invertebrates (r = 0.66), suggesting that family richness of invertebrates could be used as a surrogate of species richness in this basin. We highlight this correlation because, at the watershed scale, it allows working with family groups where species-level taxonomy is challenging. Our results provide the first comprehensive representation of freshwater biodiversity patterns at high resolution in an Andean-Amazon basin, and calls attention to the need for incorporating different taxonomic groups when assessing diversity patterns. Given these different diversity patterns, conservation programs for this basin should incorporate both vertebrate and invertebrate groups as biodiversity indicators. Finally, our study provides a practical methodological guidance in the estimation of freshwater diversity in regions of scarce information with high conservation priority, such as the Andean-Amazon basins.

Flow intermittency alters longitudinal patterns of invertebrate diversity and assemblage composition in an arid‐land stream network

Summary1. Temporary streams comprise a large proportion of the total length of most stream networks, and the great majority of arid‐land stream networks, so it is important to understand their contribution to biotic diversity at both local and landscape scales.2. In late winter 2010, we sampled invertebrate assemblages in 12 reaches of a large arid‐land stream network (including perennial and intermittent headwaters, intermittent middle reaches and perennial rivers) in south‐east Arizona, U.S.A. Intermittent reaches had then been flowing for c. 60 days, following a dry period of more than 450 days. We sampled a subset of the perennial study reaches three more times between 2009 and 2011. Since intermittent reaches were dry during these additional sampling periods, we used assemblage data from two other intermittent streams in the study network (sampled in 2004–05 and 2010) to explore interannual variability in intermittent stream assemblage composition.3. Invertebrate richness was lowest in intermittent reaches, despite their often being connected to species‐rich perennial reaches. The assemblages of these intermittent reaches were not simply a subset of the species in perennial streams, but rather were dominated by a suite of stoneflies, blackflies and midges with adaptations to intermittency (e.g. egg and/or larval diapause). On average, 86% of individuals in these samples were specialists or exclusive to intermittent streams. Predators were 7–14 times more abundant in perennial than in intermittent reaches.4. Despite being separated by long distances (12–25 km) and having very different physical characteristics, the assemblages of perennial headwaters and rivers were more similar to one another than to intervening intermittent reaches, emphasising the prime importance of local hydrology in this system.5. The duration and recurrence intervals of dry periods, and the relative importance of dispersal from perennial refuges, probably influence the magnitude of biological differences between neighbouring perennial and temporary streams. Although perennial headwaters supported the highest diversity of invertebrates, intermittent reaches supported a number of unique or locally rare species and as such contribute to regional species diversity and should be included in conservation planning.

Estimating and conserving patterns of invertebrate diversity: a test case of New Zealand land snails

AbstractAim Using New Zealand land snails as a case study, we evaluated recent spatial modelling approaches for the analysis of diversity in species‐rich invertebrate groups. Applications and prospects for improved conservation assessment were investigated.Location New Zealand.Methods The study used a spatially extensive and taxonomically comprehensive, plot‐based dataset on community structure in New Zealand land snails. Generalized regression analysis and spatial prediction (GRASP) was used to model and predict species richness as a function of environmental variables (including aspects of climate, soils and vegetation). Generalized dissimilarity modelling (GDM) was used to model turnover in species composition in relation to environmental and geographical distances, and to assess community similarity and the representativeness of the reserve network.Results Observed land snail richness in 20 × 20 m plots ranged from 1 to 74 (mean 17.5). The GRASP model explained a modest 27% of the variation in richness. The GDM model explained 57% of the variation in species turnover and indicated approximately equal amounts related to environmental (Cody’s beta diversity) and geographical distance (Cody’s gamma diversity). Temperature and moisture were the most important environmental variables. Results indicate that snail distributions are not only sorted by environment but are also strongly influenced by historical effects consistent with those expected of poorly dispersing taxa that have persisted in refugia during past climatic change. The GDM model enabled spatial classifications of snail communities, highlighting diverse communities in heterogeneous regions, such as the South Island mountains, and also enabled continuous depictions of community similarity and adequacy of New Zealand’s protected natural areas network.Main conclusions The GRASP and GDM analyses allowed us to model and depict spatial patterns of diversity in land snail communities involving 845 species, and produce community classifications and estimates of community similarity. These tools advance conservation assessment in species‐rich groups, but require further conceptual and methodological development.

Interaction between disturbance and primary productivity in determining stream invertebrate diversity

Invertebrate diversity patterns were examined in 10 streams that differed in substrate disturbance rates, in Taranaki, New Zealand, between April 1999 and January 2000. Two sites on each stream were sampled, one under native forest canopy where light was postulated to limit periphyton growth and a similar site 225–3800 m downstream in open grassland. Periphyton biomass was considerably higher at open stable sites than at closed or unstable sites. Associated with the higher algal biomass, species number and total abundance of animals were higher at open canopy sites. Species number exhibited a negative linear relationship with disturbance but only at open sites. In contrast, rarefied species richness exhibited a negative linear relationship with disturbance at both open and closed sites. This was a result of communities at the more disturbed sites being numerically dominated by only a few taxa compared to the more evenly distributed communities at stable sites. The observed patterns provide little support for contemporary diversity disturbance models but suggest diversity of invertebrates in streams is a function of time since the last disturbance, mediated through recovery of the food base in autotrophic streams.

Patterns of invertebrate diversity in streams and freshwater springs in Northern Spain

Invertebrate diversity patterns were examined in six rheocrene springs and six nearby, runoff-fed streams in Cantabria, Northern Spain. Periphyton biomass, organic matter and biomass of moss were always higher in springs than streams. Species densities (number of species/area) and rarified species richness (number of species/number of individuals) were lower and invertebrate densities greater in spring habitats. Of 22 variables chlorophyll-a was the best predictor of species richness, whereas total organic matter was the best predictor of invertebrate density, although neither relationship was strong. Spring habitats had invertebrate communities dominated by non-insect taxa (e. g., Echinogammarus, and Hydrobiidae and Neritidae snails), in contrast to the insect dominated communities in runoff-fed streams (e. g., Baetis, Ecdyonurus, Elmis, Prosimulium, Scirtes and Chironomidae). Echinogammarus had the highest densities in springs; an order of magnitude greater than any other taxa. The effects of biotic processes, such as predation from Echinogammarus on community structure may be more marked in springs because predated individuals cannot be as readily replaced by drifting animals from upstream reaches. The reduced diversity in springs compared to streams could be a result of several factors including increased predation from animals such as Echinogammarus or the unusually constant thermal characteristics.

Predicting invertebrate diversity from disturbance regimes in forest streams

The link between substrate disturbance and stream invertebrate species richness is often complicated by the fact that substrate disturbance removes both invertebrates and periphyton (a potential food source). It is never clear whether disturbance acts directly on species diversity by removing animals or indirectly by reducing one of their food sources. To examine this relationship invertebrate diversity patterns were examined in 25 forest streams in Urewera National Park, New Zealand, where light attenuation from the forest canopy was postulated to limit periphyton biomass and remove the confounding influence of periphyton on the link between substrate disturbance and invertebrate diversity. Invertebrate species richness declined linearly with increasing substrate disturbance. Although periphyton biomass was comparatively low, species richness was more strongly related to periphyton biomass than to any disturbance measure. The highly mobile nature and terrestrial reproductive stage of many lotic invertebrates suggest that colonisation dynamics may have a more important influence on diversity patterns than monopolisation of resources for population growth. Although both the intermediate disturbance hypothesis and the dynamic equilibrium model encompass colonisation as a critical determinant of diversity both models also require a trade‐off between the colonising and competitive ability of individual species; a phenomenon which does not appear to occur widely in lotic communities. Rather, it is postulated that resource levels will set an upper limit to the species richness of a benthic community that can be achieved through colonisation of taxa in the absence of disturbance, while disturbance removes taxa and resets the colonisation process.

Diversity Patterns in Stream Benthic Invertebrate Communities: The Influence of Habitat Stability

Invertebrate diversity patterns were examined in 11 freshwater habitats (10 streams and a windswept lake shore) of similar physicochemical nature but different thermal and hydrologic stability in the Cass—Craigieburn region, New Zealand. Species richness and density were markedly higher at the more stable sites, but species evenness peaked at sites of intermediate stability. Of the 20 environmental variables examined, a multivariate instability index incorporating temporal variation in depth, temporal variation in current speed, substrate stability, the Pfankuch channel stability index, temperature range, and stream reach tractive force was the single best predictor of the number of species, whereas epilithic pigment concentration was the single best predictor of invertebrate density. The pattern in species richness did not support any of three diversity hypotheses considered. In contrast, the pattern in species evenness suggested competitive exclusion may be occurring patchily and that Hutson's dynamic equilibrium model may have some validity, at least at the level of the patch. However, the strong link between productivity and stability apparent in these habitats, and a lack of information on the effects of increased productivity on competition in stream benthic communities makes any firm assessment of the latter model difficult. The observed diversity patterns are, however, consistent with the idea that high diversity is maintained in these habitats by an interaction between low levels of disturbance and habitat patchiness.