Birds as surrogates for mammals and reptiles: Are patterns of cross-taxonomic associations stable over time in a human-modified landscape?

Cross-taxonomic surrogates can be feasible alternatives to direct measurements of biodiversity in conservation if validated with robust data and used with explicit goals. However, few studies of cross-taxonomic surrogates have examined how temporal changes in composition or richness in one taxon can drive variation in concordant patterns of diversity in another taxon, particularly in a dynamic and heavily modified landscape. We examined this problem by assessing changes in cross-taxonomic associations over time between the surrogate (birds) and target vertebrate taxa (mammals, reptiles) that demand high sampling effort, in a heterogeneous mosaic landscape comprising pine monoculture, eucalypt woodland remnants and agricultural land. Focussing on four study years (1999, 2001, 2011, 2013) from a dataset spanning 15 years, we: (1) investigated temporal changes in cross-taxonomic congruency among three animal taxa, (2) explored how temporal variation in composition and species richness of each taxon might account for variation in cross-taxonomic congruency, and (3) identified habitat structural variables that are strongly correlated with species composition of each taxon. We found the strength of cross-taxonomic congruency varied between taxa in response to both landscape context and over time. Among the three taxa, overall correlations were weak but were consistently positive and strongest between birds and mammals, while correlations involving reptiles were usually weak and negative. We also found that stronger species richness and composition correlations between birds and mammals were not only more prevalent in woodland remnants in the agricultural matrix, but they also increased in strength over time. Temporal shifts in species composition differed in rate and extent among the taxa even though these changes were significant over time, while important habitat structural correlates were seldom shared across taxa. Our study highlights the role of the landscape matrix and time in shaping animal communities and the resulting cross-taxonomic associations in the woodland remnants, especially after a major perturbation event (i.e. plantation establishment). In such dynamic landscapes, differing and taxon-specific shifts in diversity over time can influence the strength, direction and consistency of cross-taxonomic correlations, therefore posing a ‘temporal’ problem for the use of surrogates like birds in monitoring and assessments of biodiversity, and conservation management practices.     

Taxonomic sufficiency in ecological studies of terrestrial invertebrates

The concept of taxonomic sufficiency (identifying organisms only to a level of taxonomic resolution sufficient to satisfy the objectives of a study) has received little attention in ecological studies of terrestrial invertebrate assemblages. Here we critically evaluate three approaches to taxonomic sufficiency: the use of morphospecies, genera and functional groups. The objective was to compare estimates of richness (α diversity) and turnover (β diversity) of ant assemblages generated by these data with estimates produced using data for ant species. Ground-active ants were sampled using pitfall trapping within three habitat types: a eucalypt plantation, woodland regrowth patches and the surrounding grassland at a study site in the upper Hunter Valley, New South Wales. Comparisons of assemblage richness and turnover among taxonomic data sets and habitats and after different data transformations used univariate (simple correlation and ANOVA ) and multivariate (Mantel tests, ANOSIM and SSHMDS ) techniques. Our study found: (i) morphospecies and genus richness was highly correlated with species richness over the study area; (ii) ordination scatterplots using species, morphospecies and genus data revealed similar patterns of site separation for the three habitats; (iii) the results were very similar using untransformed, log transformed and binary data; (iv) functional group ordinations separated all three habitat types for untransformed abundance data; and (v) estimates of species turnover were highly correlated with estimates of morphospecies and genus turnover. These results are discussed in relation to future monitoring of ant community structure.     

Biogeographical concordance and efficiency of taxon indicators for establishing conservation priority in a tropical rainforest biota

Prioritizing areas for conservation requires the use of surrogates for assessing overall patterns of biodiversity. Effective surrogates will reflect general biogeographical patterns and the evolutionary processes that have given rise to these and their efficiency is likely to be influenced by several factors, including the spatial scale of species turnover and the overall congruence of the biogeographical history. We examine patterns of surrogacy for insects, snails, one family of plants and vertebrates from rainforests of northeast Queensland, an area characterized by high endemicity and an underlying history of climate-induced vicariance. Nearly all taxa provided some level of prediction of the conservation values for others. However, despite an overall correlation of the patterns of species richness and complementarity, the efficiency of surrogacy was highly asymmetric; snails and insects were strong predictors of conservation priorities for vertebrates, but not vice versa. These results confirm predictions that taxon surrogates can be effective in highly diverse tropical systems where there is a strong history of vicariant biogeography, but also indicate that correlated patterns for species richness and/or complementarity do not guarantee that one taxon will be efficient as a surrogate for another. In our case, the highly diverse and narrowly distributed invertebrates were more efficient as predictors than the less diverse and more broadly distributed vertebrates.     

Are protected areas maintaining bird diversity?

Evaluating the effectiveness of protected areas for sustaining biodiversity is crucial to achieving conservation outcomes. While studies of effectiveness have improved our understanding of protected‐area design and management, few investigations (< 5%) have quantified the ecological performance of reserves for conserving species. Here, we present an empirical evaluation of protected‐area effectiveness using long‐term measures of a vulnerable assemblage of species. We compare forest and woodland bird diversity in the Australian Capital Territory over 11 yr on protected and unprotected areas located in temperate eucalypt woodland and matched by key habitat attributes. We examine separately the response of birds to protected areas established prior to 1995 and after 1995 when fundamental changes were made to regional conservation policy. Bird diversity was measured in richness, occurrence of vulnerable species, individual species trajectories and functional trait groups. We found that protected areas were effective in maintaining woody vegetation cover in the study region, but were less effective in the protection of the target bird species assemblage. Protected areas were less species rich than unprotected areas, with significant declines in richness across sites protected prior to 1995. Small, specialised and vulnerable species showed stronger associations with unprotected areas than protected areas. Our findings indicate that recently established reserves (post‐1995) are performing similarly to unprotected woodland areas in terms of maintaining woodland bird diversity, and that both of these areas are more effective in the conservation of woodland bird populations than reserves established prior to 1995. We demonstrate that the conservation value of protected areas is strongly influenced by the physical characteristics, as well as the landscape context, of a given reserve and can diminish with changes in surrounding land use over time. Both protected areas and off‐reserve conservation schemes have important roles to play in securing species populations.     

Differences in leaf‐litter invertebrate assemblages between radiata pine plantations and neighbouring native eucalypt woodland

Abstract We investigated the structure, composition and environmental correlates of leaf‐litter invertebrate assemblages in Pinus radiata plantations and in neighbouring native eucalypt woodland in the Jenolan Caves Karst Conservation Reserve, south‐east Australia. Invertebrate assemblages of plantations were compared with remnant eucalypt woodland located well away from the influence of plantations to determine the direct effects of plantations as a result of habitat‐replacement with a non‐native plantation species. We also included in our comparisons edge habitat of eucalypt woodland located immediately adjacent to plantations. This unique edge habitat is exposed to the intrusion of large volumes of pine leaf‐litter from plantations, which has the potential to affect indirectly invertebrate assemblages of surrounding woodland. We found that species richness of invertebrates was significantly lower in pine plantations compared with remnant eucalypt woodland. There was a complete absence of species from 12 invertebrate orders that were found in surrounding eucalypt woodland. A rich and abundant native plant understorey that provides increased habitat heterogeneity is the most likely explanation for the richer invertebrate assemblage found in remnant eucalypt woodland. The total abundance of all invertebrate taxa in pine plantations in winter was significantly higher than in remnant eucalypt woodland, pine‐litter edges and pine‐free edges. Plantations were characterized by particularly high abundances of species in two orders, Acari and Collembola. High abundances of acarine and collembolan species in plantations were associated with a decompositional environment represented by comparatively higher moisture contents and higher C : N ratios of both leaf‐litter and soil, higher soil conductivity and lower soil pH. We suggest that implementation of The Plantation Biodiversity Benefits Score will be a fruitful way forward to assess the environmental benefits that can be gained from pine plantations in this region of south‐eastern Australia.     

Eucalypt plantings on farms benefit woodland birds in south‐eastern Australia

Abstract Most of the original forest and woodland cover on the western slopes of New South Wales and the northern plains of Victoria has been cleared for agriculture (wheat, sheep and cattle) and what remains is highly fragmented and modified by a long history of disturbance. Over the past three decades, native eucalypt trees and shrubs have been planted extensively in a part of this region to provide a range of environmental benefits. Our aim was to determine the extent to which these plantings could improve biological diversity in agricultural landscapes in south‐eastern Australia and to identify the variables influencing their effectiveness. We sampled birds at 120 sites encompassing the range of available patch sizes, stand ages, floristic and structural conditions, and habitat attributes for revegetated areas and remnants of native vegetation, and we compared these to nearby paddocks. Eucalypt plantings were found to provide significant improvements in bird population density compared with cleared or sparsely treed paddocks, and mixed eucalypt and shrub plantings had similar bird communities to remnant native forest and woodland in the region. Birds displayed a strong response to patch size, with both larger (≥5–20 ha) eucalypt plantings and larger (≥5–20 ha) remnants having more species and more individuals per unit area than smaller (<5 ha) patches of these vegetation types. Older (10–25 years) plantings had more bird species and individuals than young (<10 years) plantings. The distance from remnant forest and woodland (habitat connectivity) appeared to be an important variable influencing bird species richness in eucalypt plantings. The main differences were due to the greater numbers of species classified as woodland‐dependent in the larger‐sized patches of plantings and remnants. Eucalypt plantings provided useful habitat for at least 10 declining woodland‐dependent species, notably for the Speckled Warbler, Red‐capped Robin and Rufous Whistler. The Brown Treecreeper and Dusky Woodswallow appeared to be the species most limited by the extent of remnant forest and woodland in the region. Plantings of all shapes and sizes, especially those larger than 5 ha, have an important role to play in providing habitat for many bird species. Restoration efforts are more likely to be successful if eucalypt plantings are established near existing remnant vegetation.     

Modelling spatial patterns of biodiversity for conservation prioritization in North-eastern Mexico

Relationships between spatial patterns of bird and mammal species richness in north‐eastern Mexico were analysed in relation to the location of three biosphere reserves (El Abra‐Tanchipa, El Cielo, and Sierra Gorda) and 13 priority areas recently identified for conservation. Ecological niches were modelled and potential distributions delimited for 285 bird and 114 mammal species using a genetic algorithm based on locality information from museum specimens and 15 selected environmental attributes. Potential distributions were transformed into hypothesized current distributions based on species–habitat associations as reflected in a recent land‐use map. Although species richness was lower when distributions were reduced from potential to current, spatial patterns of potential and current richness were similar. Heuristic, complementarity‐based prioritization procedures were used to identify combinations of areas and sites with maximal species representation: the biosphere reserves included 79% of birds and 74% of mammal species; eight priority areas provided an additional 11% of birds and 13% of mammals; the remaining 10% of birds and 13% of mammals were concentrated in new sites across the study area.     

Geographic variation in plant species richness patterns within temperate eucalypt woodlands of eastern Australia

Species density, pattern diversity and species pool are often studied in isolation and correlated individually to environmental gradients. However analysis of how these three measures interrelate can give insights into the interpretation of local and regional processes. In addition, an understanding of how these diversity measures change across the natural distribution of a community may help in decision making processes regarding reservation. Temperate eucalypt woodlands in eastern Australia are one of the most visible and ubiquitous communities in eastern Australia, but have undergone one of the most significant modification and fragmentation processes due to past and current pressure to clear for agriculture. Data from 176 vascular plant survey sites sampled across 14 woodland assemblages are used here to analyse geographic gradients in species density, pattern diversity and species pool size. It was discovered that species density was significantly correlated to pattern diversity and species pool size but that pattern diversity and species pool size were uncorrelated. There was a significant relationship whereby species density increased as pattern diversity decreased. These patterns may be explained by the maintenance of interconnectedness, dispersal and rescue effects at this scale of investigation but local interactions cannot be ruled out as important. Generally species density and species pool size increased from west to east in the study area and pattern diversity was strongly correlated to the coldest minimum winter temperatures. It is suggested that if local woodland richness is maintained by low pattern diversity and greater habitat connectedness then larger reserves are required in order to maintain the largest area of contiguous habitat. In such situations small isolated patches, which are increasingly fragmented by the pressure to clear for agriculture will accumulate larger extinction debts.     

Conservation of biodiversity in coffee agroecosystems: a tri-taxa comparison in southern Mexico

We compare species richness of birds, fruit-feeding butterflies and ground-foraging ants along a coffee intensification gradient represented by a reduction in the number of species of shade trees and percentage of shade cover in coffee plantations. We sampled the three taxa in the same plots within the same period of time. Two sites were selected in the Soconusco region of the state of Chiapas, Mexico. Within each site four habitat types were selected and within each habitat type four points were randomly selected. The habitat types were forest, rustic coffee, diverse shade coffee, and intensive coffee (low density of shade). We found different responses of the three taxa along the intensification gradient. While ants and butterflies generally decrease in species richness with the decrease of shade cover, birds declined in one site but increased in the other. Ant species richness appears to be more resistant to habitat modification, while butterfly species richness appears to be more sensitive. Bird species richness was correlated with distance from forest fragments but not with habitat type, suggesting that scale and landscape structure may be important for more mobile taxa. For each of these taxa, the rustic plantation was the one that maintained species richness most similar to the forest. We found no correlation between the three taxa, suggesting that none of these taxa are good candidates as surrogates for each other. We discuss the implications of these results for the conservation of biodiversity in coffee plantations, in particular, the importance of distinguishing between different levels of shade, and the possibility that different taxa might be responding to habitat changes at different spatial scales.     

Site vegetation characteristics are more important than landscape context in determining bird assemblages in revegetation

The effectiveness of revegetation in providing habitat for fauna is expected to be determined both by within‐site factors and attributes of the landscape in which a revegetation site occurs. Most studies of fauna in revegetation have been conducted in landscapes that have been extensively cleared, modified or fragmented, and in Australia, predominantly in the southern temperate zone. We investigated how within‐site vegetation attributes and landscape context attributes were related to bird species richness and composition in a chronosequence of post‐mining rehabilitation sites within an otherwise intact landscape in tropical northern Australia. Our working hypothesis was that bird species richness in rehabilitating sites would be positively related to site vegetation structure and landscape context including (1) proximity to woodland and (2) the proportion of woodland within a 500‐m buffer of rehabilitation sites. Within each of 67 sites, we sampled vegetation once and surveyed for birds eight times over 16 months. Landscape context variables were calculated using GIS. There were large differences between bird assemblages of woodland and rehabilitation sites and between age classes of rehabilitation. Bird assemblages were strongly related to site vegetation attributes across all rehabilitation sites. Proximity to woodland was only related to bird assemblages in rehabilitation sites older than 4 years old. We conclude that the relative importance of landscape context and site variables at any point in time will be a function of how closely vegetation within the revegetation site matches the habitat resource requirements of individual species.     

Indicators of Diptera diversity in wet grassland habitats are influenced by environmental variability,scale of observation,and habitat type

In low intensity agri-ecosystems such as wet grassland habitats, the inclusion of invertebrates in conservation assessments and monitoring is usually limited to charismatic groups such as bees or butterflies. However, wet grasslands support a wide range of inveterate groups, some of which may exhibit limited movement not generally represented by more mobile groups such as those typically examined. The use of surrogate species which exemplify broader invertebrate diversity has been suggested as a possible means of including these overlooked invertebrates (such as Diptera) in conservation planning within these habitats. Based on collections made by Malaise trap, we utilized two families of Diptera (Sciomyzidae and Syrphidae) as indicators of a wider range of dipteran diversity (nine Diptera families identified to parataxonomic unit level [PUs]) in wet grassland habitats. We examined the role of environmental variability, spatial scale, and habitat type on patterns of cross-taxon congruence for all three assemblages. Both environmental correlation and community congruence were significantly stronger among assemblages when examined at low spatial scales, highlighting the need to examine dipteran groups at scales untypical of current agri-environmental assessments; namely field and farm level. Furthermore, when wet grasslands were differentiated into two habitat categories (sedge and rush dominated grasslands), the significance of the community congruence increased markedly. This correlation was particularly strong between Sciomyzidae and PUs which demonstrated similar differentiation based on habitat type, implying that assemblages which exhibit comparable ecological partitioning are more likely to be useful surrogates of one another. Correlations between richness, abundance and Shannon’s diversity were highly variable among groups, suggesting compositional analysis as the most appropriate examination of dipteran diversity for surrogacy studies. The results indicate that cross-assemblage congruence of Diptera is influenced by similarity of response to environmental variability, scale of observation, and examination of assemblages differentiated into appropriate habitat categories. The results illustrate the need to investigate invertebrate biodiversity surrogates at scales appropriate to the indicator groups and examine congruence among assemblages within specific habitat categories. Such an approach has the potential to maximise gamma diversity in areas where wet grasslands are under threat of intensification or abandonment.     

Habitat heterogeneity drives bird species richness,nestedness and habitat selection by individual species in fluvial wetlands of the Paraná River,Argentina

We assessed the relationship between habitat heterogeneity and bird species richness and composition within wetlands of the floodplain of the Middle Paraná River, Argentina. Given the high habitat heterogeneity in these wetland systems, we sought to determine whether (i) there was a positive relationship between bird species richness and habitat heterogeneity; (ii) whether bird species richness was associated with certain types of individual habitat types; (iii) whether there was a pattern of species nestedness and turnover between sites as a function of habitat heterogeneity and composition, respectively; and (iv) whether individual species exhibited associations with habitat heterogeneity. Point counts were used to survey birds at 60 sites. We estimated the area of eight habitat types found within a 200‐m radius from the centre of each site and calculated number and Pielou's evenness of habitat types. These indices, together with area proportion of each habitat type, were used as explanatory factors of bird species richness in linear regression models. Habitat heterogeneity per se rather than area of individual habitat types was a more important predictor of species richness in these fluvial wetlands. Sites with more habitat types supported more bird species. Results showed that individual bird species were associated with different habitat types and, therefore, sites that contained more habitat types contained more species. Number of habitat types accounted for species nestedness between sites whereas composition of habitat types accounted for species turnover between sites. Results suggest that selection of heterogeneous sites by individual species could help explain the positive heterogeneity–species richness relationship. Our findings highlight the importance of habitat heterogeneity per se resulting from flood disturbances in maintaining bird richness in fluvial systems.     

Plant functional types and traits as biodiversity indicators for tropical forests: two biogeographically separated case studies including birds, mammals and termites

Multi-taxon surveys were conducted in species-rich, lowland palaeotropical and neotropical forested landscapes in Sumatra, Indonesia and Mato Grosso, Brazil. Gradient-directed transects (gradsects) were sampled across a range of forested land use mosaics, using a uniform protocol to simultaneously record vegetation (vascular plant species, plant functional types (PFTs) and vegetation structure), vertebrates (birds, mammals) and invertebrates (termites), in addition to measuring site and soil properties, including carbon stocks. At both sites similar correlations were detected between major components of structure (mean canopy height, woody basal area and litter depth) and the diversities of plant species and PFTs. A plant species to PFT ratio [spp.:PFTs] was the best overall predictor of animal diversity, especially termite species richness in Sumatra. To a notable extent vegetation structure also correlated with animal diversity. These surrogates demonstrate generic links between habitat structural elements, carbon stocks and biodiversity. They may also offer practical low-cost indicators for rapid assessment in tropical forest landscapes.     

Bird communities of highway verges: Influence of adjacent habitat and roadside management

We have investigated the effects of landscape traversed and roadside structure on the use of highway verges by birds. Three contrasted landscapes were chosen in terms of human land use and vegetation structure: an intensive farmland, a pine plantation, and a matoral. The roadside sections varied in vegetation structure, width and profile. We recorded birds present in roadsides and adjacent habitats by transect counts over all seasons. Roadside bird species appeared for a great part similar to those of adjacent habitats. However, diversity and abundance in verges did not depend on that of adjacent habitats. Woody roadsides were comparable to hedges, as trees (and shrubs) in verges enhanced species richness and abundance of birds in the farmland and woodland sites. Width and profile of verges had less influence. In all sites, typical species of the habitat traversed partly avoided roadsides. On the contrary, numerous species associated with ‘rare’ habitats in one site preferred roadsides, provided that verge vegetation contrasted with the dominant habitat. It is concluded that birds responses to highways can vary greatly with landscape traversed and verge vegetation. Highway verges could be favorable to birds, if they constitute a complementary habitat to the dominant habitat within a landscape.     

Equal diversity in disparate species assemblages: a comparison of native and exotic woodlands in California

The species richness of ecosystems can remain stable over time, despite changes in species composition and changes in the dominant plant species. While this pattern of stability is known to occur temporally, it has been examined poorly in a spatial context. To examine this spatially, the species richness, diversity and composition of native woodlands (of oak and bay trees) and exotic woodlands (of eucalypt trees) were compared in California. Species richness was nearly identical for understorey plants, leaf‐litter invertebrates, amphibians and birds; only rodents had significantly fewer species in eucalypt sites. Species diversity patterns (using the Shannon–Wiener Index) were qualitatively identical to those for species richness, except for leaf‐litter invertebrates, which were significantly more diverse in eucalypt sites during the spring. Species composition was different between sites, as evidenced by a principal components analysis, coefficients of similarity, and the relatively few species shared between native and eucalypt sites. Thus, the consistency in richness and diversity observed for most groups, in most seasons, occurred despite significant differences in species composition. These results are consistent with previous demonstrations of temporal stability, suggesting that species richness may often be stable, both temporally and spatially, despite changes in composition and regardless of the dominant vegetation.     

Seasonality,habitat type and locality influenced bird assemblage structure in Nigeria

This is the first report of the avian assemblage in the study area of Dutse, Nigeria. In addition to recording bird species, the effects of season, dominant vegetation structure, locality and anthropogenic activities on bird abundance, species richness and diversity were investigated. Using the point transect method, 264 points on 48 km of transect were used to count birds between 06:30 and 11:00 from August 2015 to February 2016. A total of 122 bird species of 41 families were recorded. Highest bird species richness was recorded in Warwade, highest abundance in Model, and highest diversity in Malamawa. The dry season and woodland habitat showed higher bird species richness, abundance and diversity than the wet season and shrubland habitat. Tree density was more important in increasing bird abundance than shrub density. Small-scale anthropogenic activities and habitat modification, such as farming, grazing, wood removal and human interference did not appear to have impacted the birds; however, loss of high tree-density woodland habitats may pose a major threat to the bird community in Dutse. The presence of birds of concern in the area suggests the need for conservation efforts of avifauna and as well as the forested habitats in Dutse.     

Biotope prioritisation in the Central Apennines (Italy): species rarity and cross-taxon congruence

The conservation status of invertebrates is usually lesser known than that of vertebrates, and strategies to identify biotopes to preserve invertebrate diversity are typically based on a single surrogate taxon, or even on the use of vertebrates as surrogates. Aim of this research is to illustrate a method for biotope prioritisation that can be easily adapted to different animal groups and geographical contexts. A two-step protocol for biotope prioritisation is proposed on the basis of a multidimensional characterisation of species vulnerability. Firstly, species vulnerability is estimated from rarity measures which include geographical range, abundance and biotope specialisation. Then, these values of vulnerability are used to rank biotopes. The method was applied here to the tenebrionid beetles, the butterflies, the birds and the mammals of the Central Apennines, a montane area of high conservation concern for South Europe. This study provides evidence for the importance of including insects in conservation decisions, because vertebrates are poor surrogates for insects. Conservation efforts in the reserves included in the study area are mostly focused on vertebrates, for which woodlands are considered particularly important. However high altitude open biotopes are crucial for both tenebrionids and butterflies, and preservation of such kind of biotopes would be beneficial also for vertebrates. The approach applied here demonstrates that (1) vertebrates are poor surrogates for insects, and (2) measures of species rarity, typically used in vertebrate conservation, can be obtained also for insects, for which a veritable amount of data are hidden in specialised literature and museum collections.     

Hot,dry and different: Australian lizard richness is unlike that of mammals,amphibians and birds

Aims (1) To map the species richness of Australian lizards and describe patterns of range size and species turnover that underlie them. (2) To assess the congruence in the species richness of lizards and other vertebrate groups. (3) To search for commonalities in the drivers of species richness in Australian vertebrates. Location Australia. Methods We digitized lizard distribution data to generate gridded maps of species richness and β‐diversity. Using similar maps for amphibians, mammals and birds, we explored the relationship between species richness and temperature, actual evapotranspiration, elevation and local elevation range. We used spatial eigenvector filtering and geographically weighted regression to explore geographical patterns and take spatial autocorrelation into account. We explored congruence between the species richness of vertebrate groups whilst controlling for environmental effects. Results Lizard richness peaks in the central deserts (where β‐diversity is low) and tropical north‐east (where β‐diversity is high). The intervening lowlands have low species richness and β‐diversity. Generally, lizard richness is uncorrelated with that of other vertebrates but this low congruence is strongly spatially structured. Environmental models for all groups also show strong spatial heterogeneity. Lizard richness is predicted by different environmental factors from other vertebrates, being highest in dry and hot regions. Accounting for environmental drivers, lizard richness is weakly positively related to richness of other vertebrates, both at global and local scales. Main conclusions Lizard species richness differs from that of other vertebrates. This difference is probably caused by differential responses to environmental gradients and different centres of diversification; there is little evidence for inter‐taxon competition limiting lizard richness. Local variation in habitat diversity or evolutionary radiations may explain weak associations between taxa, after controlling for environmental variables. We strongly recommend that studies of variation in species richness examine and account for non‐stationarity.     

Species richness and assemblages of bats along a forest elevational transect in Papua New Guinea

Over the past decades, elevational gradients have become a powerful tool with which to understand the underlying cause(s) of biodiversity. The Mt. Wilhelm elevational transect is one such example, having been used to study the birds, insects, and plants of Papua New Guinea (PNG). However, a survey of mammals from this forest elevational transect was lacking. We thus aimed to investigate patterns in the community structure and species richness of bats (Chiroptera) along the transect, link the species to available regional data, and explain the observed patterns by including environmental characteristics. Bat assemblages were surveyed between 200 m and a timberline at 3700 m a.s.l. at eight study sites separated by 500 m in elevation. We conducted mist-netting and acoustic surveys to detect and identify species at each site. Regional data were compiled to compare local with regional diversity. Finally, biotic (i.e., food availability, habitat features) and abiotic (i.e., mean daily temperature) factors were included in our analyses to disentangle the ecological drivers underlying bat diversity. Results revealed that species richness decreases with ascending elevation and was best explained by a corresponding decrease in temperature. We observed both turnover and nestedness of the species composition at regional scale whereas turnover was dominant at local scale. Extensions and shifts of bat elevational ranges were also found in Mt. Wilhelm. Consequently, despite that the study was restricted to one mountain in PNG, it demonstrates how basic inventory surveys can be used to address ecological questions in other similar and undisturbed tropical mountains.     

Relationships between land snail assemblage patterns and soil properties in temperate-humid forest ecosystems

Aim The objectives were to (1) analyse the combined effects of soil pH, Ca content and soil moisture on total density and species richness of land snails in forest ecosystems, (2) explore relationships between the quantitative composition of snail assemblages and habitat characteristics, (3) investigate the relationships between soil pH and density of some of the most frequent species, and (4) compare the data with those from studies conducted in other temperate‐humid regions of Europe. Location Study sites were selected from 15 landscape types including different lithologies within the area of Baden‐Württemberg (35,000 km²), SW Germany. Methods Snails were recorded quantitatively from 83 study sites, with four plots representing a total of 0.25 m² per site. Topsoil samples from each site were analysed for pH, exchangeable Ca, and Ca content of carbonates. Three categories of soil moisture (dry, intermediate and wet) were established and defined according to the (climatic) water balance. Numbers of individuals and species were brought in relation to soil moisture and soil pH. Cluster analyses were conducted to identify groups of quantitatively similar snail species assemblages. Results Topsoil pH (2.7–7.5) and soil Ca contents were closely correlated. On dry soils, total snail density and species richness are generally low and do not change with pH, but clearly increase with increasing pH on intermediate moisture soils and on wet soils. On the latter, numbers of individuals and species are generally much higher compared with intermediate moisture sites at the same value of soil pH. Changes of density in relation to soil pH vary between species. Depending on the species, density increases only in the lower or only in the higher range of pH, is not related to pH, or decreases with increasing pH. Furthermore, these patterns vary within the same species depending on the region. This became evident from comparisons with other studies, particularly between sites in SW Germany and southern Scandinavia. From cluster analyses, subgroups of snail assemblages of high quantitative similarity were identified. Group formation is explained by soil pH to some extent, and one subgroup showed a connection with coniferous woodland sites on acidic soils. No further environmental factors available from our data could explain the clustering of snail assemblages more detailed. Main conclusions Soil moisture is the strongest determinant of snail density and species richness at undisturbed woodland sites, but effects of soil moisture and soil pH on these patterns are closely interrelated on intermediate moisture soils and wet soils. However, the quantitative species composition of the land snail assemblages is related to soil properties to a lower degree than snail density and species richness, and other habitat characteristics such as vegetation or litter quality, can be important for species dominance in addition.