Ecology of a shell convergence between subfamilies of polygyrid land snails

The shell convergence between Neohelix dentifera and Inflectarius ferrissi is an important key to understanding the unusual evolutionary pattern of polygyrid land snails in eastern North America. This group is characterized by conchologically distinct shell-static clades that have radiated ecologically to the extent that shell shape and habitat are not detectably correlated at the species level; furthermore, entire shell-static clades converge conchologically between anatomically distinct lineages (triodopsines and polygyrines). The triodopsine N. dentifera and the polygyrine I. ferrissi both represent unique, drastic shifts from their shell-static clades, and thus are possible founders of new shell-static clades. This study shows that, within a context of high intraspecific variance, N. dentifera and I. ferrissi exhibit ecological parallelism or convergence in addition to conchological convergence. In coarse-grained ecology, both are more associated with acidic, anionic, deep, low- density soils in talus in high-altitude, exposed non-oak-hickory forests than are their close relatives, even though the two are not very close to each other. In fine-grained ecology, N. dentifera converges on I. ferrissi by increased rock-association relative to outgroups, and I. ferrissi likewise converges on N. dentifera by decreased log association. Thus the shell shape unique to these two species appears to be adaptive, whereas their intraspecific ecological variances appear high enough to permit ecological radiation.     

Molecular systematics of the Amazonian endemic genus Hylexetastes (Aves: Dendrocolaptidae): taxonomic and conservation implications

Hylexetastes woodcreepers are endemic to the terra firme forests of the Amazon basin. Currently, most taxonomic sources recognize two species of Hylexetastes (H. perrotii and H. stresemanni), each divided into three subspecies. Some authors maintain that the H. perrotii subspecies should be elevated to full species status. In particular, Hylexetastes perrotii brigidai is endemic to the eastern Amazon, the second Amazonian area of endemism (Xingu) most affected by deforestation and habitat degradation. Consequently, the taxonomic status of H. p. brigidai is of particular concern for conservation. Thus far, only morphological characters have been evaluated for the taxonomic delimitation of species and subspecies of Hylexetastes. We present a molecular phylogenetic analysis of all subspecies to help delimit Hylexetastes interspecific limits. Fragments of two mitochondrial (Cytb and ND2) and three nuclear genes (FGB5, G3PDH and MUSK) from 57 Hylexetastes specimens were sequenced. An ecological niche model was estimated to describe more accurately the potential distributions of taxa and to evaluate their vulnerability to ongoing deforestation. Phylogenetic analyses support the paraphyly of the polytypic H. perrotii as currently delimited and the elevation of Hylexetastes perrotii uniformis to full species rank, as well as the presence of three evolutionary significant units (ESUs) within this newly delimited species, including one grouping all H. p. brigidai specimens. Alternatively, under lineage-based species concepts, our results support at least five evolutionary species in Hylexetastes: H. stresemanni, H. undulatus, H. perrotii, H. uniformis and H. brigidai. Each of these taxa and ESUs are distributed in different interfluvial areas of the Amazon basin, which have different degrees of disturbance. Because they occupy the most heavily impacted region among all Hylexetastes ESUs, regular assessments of the conservation statuses of H. p. brigidai and both H. uniformis ESUs are paramount.     

Understanding global patterns of mammalian functional and phylogenetic diversity

Documenting and exploring the patterns of diversity of life on Earth has always been a central theme in biology. Species richness despite being the most commonly used measure of diversity in macroecological studies suffers from not considering the evolutionary and ecological differences among species. Phylogenetic diversity (PD) and functional diversity (FD) have been proposed as alternative measures to overcome this limitation. Although species richness, PD and FD are closely related, their relationships have never been investigated on a global scale. Comparing PD and FD with species richness corroborated the general assumptions of surrogacy of the different diversity measures. However, the analysis of the residual variance suggested that the mismatches between the diversity measures are influenced by environmental conditions. PD increased relative to species richness with increasing mean annual temperature, whereas FD decreased with decreasing seasonality relative to PD. We also show that the tropical areas are characterized by a FD deficit, a phenomenon, that suggests that in tropical areas more species can be packed into the ecological space. We discuss potential mechanisms that could have resulted in the gradient of spatial mismatch observed in the different biodiversity measures and draw parallels to local scale studies. We conclude that the use of multiple diversity measures on a global scale can help to elucidate the relative importance of historical and ecological processes shaping the present gradients in mammalian diversity.     

Speciation in sympatric species of land snails from the genus Trochulus (Gastropoda,Hygromiidae)

The identification and designation of land snail species in the genus Trochulus on the basis of shell characteristics are problematic because of their great phenotypic plasticity. Some genetic analyses have proved inconclusive, with much variation within populations and apparent gene flow among them. We examined this issue by morphometric and molecular approaches on the morphologically similar species T. coelomphala, T. hispidus and T. striolatus, co‐occurring in the Alpenvorland of Germany. While these species differed in shell and reproductive system morphology, there were forms that turned out intermediate in shell characters between T. coelomphala and T. hispidus but had genital morphology similar to T. coelomphala. Phylogenetic analysis, however, showed that these forms clustered neither with T. coelomphala nor T. hispidus but are sister to T. striolatus from the same region, which suggests that they evolved by way of sympatric speciation. Further, these analyses suggest that T. coelomphala diverged within T. hispidus; a crossing experiment indicated that they were interfertile. Expanding the study to include all available Trochulus sequences enabled us to infer evolutionary relationships between them and showed that T. hispidus is polyphyletic. Some Trochulus samples of one nominal species were grouped within others. The combination of phenotypic plasticity and possible mitochondrial DNA introgression illustrates the complex nature of evolutionary processes and the need for caution in the application of traditional taxonomic practice.     

Decoupling of taxonomic diversity and morphological disparity during decline of the Cambrian trilobite family Pterocephaliidae

Although discordance between taxonomic diversity and morphological disparity is common, little is known about the underlying dynamics that drive this decoupling. Early in the history of the Cambrian trilobite family Pterocephaliidae, there was an increase in taxonomic diversity and morphological diversity. As taxonomic diversity declined in the later history of the clade, range of variation stayed high and disparity continued to increase. However, per‐branch rates of morphological evolution estimated from a recent phylogeny decreased with time. Neither within‐trait nor within‐species variation increased or decreased, suggesting that the declining rates of morphological evolution were more likely related to ecological opportunity or niche partitioning, rather than increasing intrinsic constraints. This is further supported by evidence for increased biofacies associations throughout the time period. Thus, the high disparity seen at low taxonomic diversity late in the history of this clade was due to extinction – either random or targeting mean forms – rather than increased rates of morphological evolution. This pattern also provides a scenario that could account for instances of low taxonomic diversity but high morphological disparity in modern groups.     

Palaeo‐islands as refugia and sources of genetic diversity within volcanic archipelagos: the case of the widespread endemic Canarina canariensis (Campanulaceae)

Geographical isolation by oceanic barriers and climatic stability has been postulated as some of the main factors driving diversification within volcanic archipelagos. However, few studies have focused on the effect that catastrophic volcanic events have had on patterns of within‐island differentiation in geological time. This study employed data from the chloroplast (cpDNA haplotypes) and the nuclear (AFLPs) genomes to examine the patterns of genetic variation in Canarina canariensis, an iconic plant species associated with the endemic laurel forest of the Canary Islands. We found a strong geographical population structure, with a first divergence around 0.8 Ma that has Tenerife as its central axis and divides Canarian populations into eastern and western clades. Genetic diversity was greatest in the geologically stable ‘palaeo‐islands’ of Anaga, Teno and Roque del Conde; these areas were also inferred as the ancestral location of migrant alleles towards other disturbed areas within Tenerife or the nearby islands using a Bayesian approach to phylogeographical clustering. Oceanic barriers, in contrast, appear to have played a lesser role in structuring genetic variation, with intra‐island levels of genetic diversity larger than those between‐islands. We argue that volcanic eruptions and landslides after the merging of the palaeo‐islands 3.5 Ma played key roles in generating genetic boundaries within Tenerife, with the palaeo‐islands acting as refugia against extinction, and as cradles and sources of genetic diversity to other areas within the archipelago.     

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

Aim 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.     

On the relationship between plant species diversity and genetic diversity of Plantago lanceolata (Plantaginaceae) within and between grassland communities

Aims and Methods The relationship between genetic diversity and species diversity and the underlying mechanisms are of both fundamental and applied interest. We used amplified fragment length polymorphism (AFLP) and vegetation records to investigate the association between genetic diversity of Plantago lanceolata and plant species diversity using 15 grassland communities in central Germany. We used correlation and partial correlation analyses to examine whether relationships between genetic and species diversity were direct or mediated by environmental differences between habitats.Important findings Both within- and between-population genetic diversity of P. lanceolata were significantly positively correlated with plant species diversity within and between sites. Simple and partial correlations revealed that the positive correlations indirectly resulted from the effects of abiotic habitat characteristics on plant species diversity and, via abundance, on genetic diversity of P. lanceolata. Thus, they did not reflect a direct causal relationship between plant species diversity and genetic diversity of P. lanceolata, as would have been expected based on the hypothesis of a positive relationship between plant species diversity and niche diversity.     

Molecular and morphological data reveal cryptic taxonomic diversity in the terrestrial slug complex Arion subfuscus/fuscus (Mollusca, Pulmonata, Arionidae) in continental north-west Europe

The importance and abundance of cryptic species among invertebrate taxa is well documented. Nowadays, taxonomic, phylogenetic and conservation biological studies frequently use molecular markers to delineate cryptic taxa. Such studies, however, often face the problem of the differential resolution of the molecular markers and techniques involved. This issue is explored in the present study of cryptic taxa within the terrestrial slug complex Arion subfuscus/fuscus in continental north-west Europe. To this end, morphological, allozyme and mitochondrial 16S rDNA sequence data have been jointly evaluated. Using allozyme data and gonad type, two distinct groups were consistently delineated, even under sympatric conditions. The 16S rDNA data strongly supported both those groups and even suggested the presence of three distinct taxa within one of them. However, in view of: (1) the allopatric distribution of three OTUs, (2) the lack of allozyme or morphological differentiation, and (3) the extremely high degree of intraspecific mtDNA variation reported in pulmonate gastropods, they are, for the time being, not regarded as valid species under the biological species concept. By means of 16S rDNA and allozyme data, the position of type and topotype material of A. subfuscus s.s. and A. fuscus relative to the newly defined OTUs was determined, thus clarifying the nomenclature of this species complex. Additionally, gonad type proved to be a useful character for distinguishing the two species in north-west Europe.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 83 , 23–38.     

Impacts of taxonomic inertia for the conservation of African ungulate diversity: an overview

We review the state of African ungulate taxonomy over the last 120 years, with an emphasis on the introduction of the polytypic species concept and the discipline's general neglect since the middle of the 20th century. We single out negative consequences of ‘orthodox’ taxonomy, highlighting numerous cases of neglect of threatened lineages, unsound translocations that led to lineage introgression, and cases of maladaptation to local conditions including parasitic infections. Additionally, several captive breeding programmes have been hampered by chromosome rearrangements caused by involuntary lineage mixing. We advocate that specimen‐based taxonomy should regain its keystone role in mammal research and conservation biology, with its scientific values augmented with genomic evidence. While integration with molecular biology, ecology and behaviour is needed for a full understanding of ungulate alpha diversity, we stress that morphological diversity has been neglected despite its tremendous practical importance for some groups of ‘utilizers’ such as trophy hunters, wildlife tourists and conservationists. We conclude that there is no evidence that purported ‘taxonomic inflation’ has adverse effects on ungulate conservation: rather, it is taxonomic inertia that has such adverse effects. We stress that sound science, founded on robust taxonomy, should underpin effective sustainable management (hunting, ranching, captive breeding and reintroduction programmes) of this unique African natural resource.     

Links between global taxonomic diversity,ecological diversity and the expansion of vertebrates on land

Tetrapod biodiversity today is great; over the past 400 Myr since vertebrates moved onto land, global tetrapod diversity has risen exponentially, punctuated by losses during major extinctions. There are links between the total global diversity of tetrapods and the diversity of their ecological roles, yet no one fully understands the interplay of these two aspects of biodiversity and a numerical analysis of this relationship has not so far been undertaken. Here we show that the global taxonomic and ecological diversity of tetrapods are closely linked. Throughout geological time, patterns of global diversity of tetrapod families show 97 per cent correlation with ecological modes. Global taxonomic and ecological diversity of this group correlates closely with the dominant classes of tetrapods (amphibians in the Palaeozoic, reptiles in the Mesozoic, birds and mammals in the Cenozoic). These groups have driven ecological diversity by expansion and contraction of occupied ecospace, rather than by direct competition within existing ecospace and each group has used ecospace at a greater rate than their predecessors.     

When North and South don’t mix: genetic connectivity of a recently endangered oceanic cycad,Cycas micronesica,in Guam using EST‐microsatellites

Subject to environmental changes and recurrent isolation in the last ca. 250 Ma, cycads are often described as relicts of a previously common lineage, with populations characterized by low genetic variation and restricted gene flow. We found that on the island of Guam, the endemic Cycas micronesica has most of the genetic variation of 14 EST‐microsatellites distributed within each of 18 genetic populations, from 24 original sampling sites. There were high levels of genetic variation in terms of total number of alleles and private alleles, and moderate levels of inbreeding. Restricted but ongoing gene flow among populations within Guam reveals a genetic mosaic, probably more typical of cycads than previously assumed. Contiguous cycad populations in the north of Guam had higher self‐recruitment rates compared to fragmented populations in the south, with no substantial connection between them except for one population. Guam’s genetic mosaic may be explained by the influence of forest continuity, seed size, edaphic differences, and human transport of cycads. Also important are the extent of synchrony among flushes of reproductive female seed‐bearing sporophylls and restricted pollen movement by an obligate mutualist and generalist insects. An NADH EST‐locus under positive selection may reflect pressure from edaphic differences across Guam. This and three other loci are ideal candidates for ecological genomic studies. Given this species’ vulnerability due to the recent introduction of the cycad aulacaspis scale, we also identify priority populations for ex situ conservation, and provide a genetic baseline for understanding the effects of invasive species on cycads in the Western Pacific, and islands in general.     

城市绿地昆虫群落结构及多样性——以成都市为例

为研究成都城市绿地昆虫群落功能团结构及其多样性的变化,于2020年6-10月,采用扫网、网捕、搜寻、目测和振落等方法对成都3种功能绿地(公园绿地、生产绿地和道路绿地)昆虫进行调查。调查共采集昆虫29 382号,隶属15目130科747种。其中半翅目Hemiptera、膜翅目Hymenoptera、双翅目Diptera在3种功能绿地中均属于优势类群;在不同功能绿地,植食性昆虫的丰富度总体高于寄生性、捕食性和中性昆虫;不同功能集团在各功能绿地的α多样性指数均无显著差异,植食性-捕食性昆虫(Ph-Pr)、植食性-寄生性(Ph-Pa)昆虫个体数在生产绿地中呈显著正相关(P<0.05),公园绿地和生产绿地昆虫群落结构最为相似;S_s/S_i和S_n/S_p两个稳定性指标表明：3种生境昆虫群落最稳定的时期是9月。结果表明,成都城市绿地昆虫物种多样性较为丰富,3种绿地昆虫群落组成较相似,各绿地间功能团结构特征无显著差异;各绿地功能团丰富度时序变化趋势基本一致,9月是成都市绿地昆虫群落结构最稳定的时期。     

Reconstructing the demise of Tethyan plants: climate‐driven range dynamics of Laurus since the Pliocene

Aim Climate changes are thought to be responsible for the retreat and eventual extinction of subtropical lauroid species that covered much of Europe and North Africa during the Palaeogene and early Neogene; little is known, however, of the spatial and temporal patterns of this demise. Herein we calibrate ecological niche models to assess the climatic requirements of Laurus L. (Lauraceae), an emblematic relic from the Tethyan subtropical flora, subsequently using these models to infer how the range dynamics of Laurus were affected by Plio‐Pleistocene climate changes. We also provide predictions of likely range changes resulting from future climatic scenarios. Location The Mediterranean Basin and Macaronesian islands (Canaries, Madeira, Azores). Methods We used a maximum‐entropy algorithm (Maxent) to model the relationship between climate and Laurus distribution over time. The models were fitted both to the present and to the middle Pliocene, based on fossil records. We employed climatic reconstructions for the mid‐Pliocene (3 Ma), the Last Glacial Maximum (21 ka) and a CO₂‐doubling future scenario to project putative species distribution in each period. We validated the model projections with Laurus fossil and present occurrences. Results Laurus preferentially occupied warm and moist areas with low seasonality, showing a marked stasis of its climatic niche. Models fitted to Pliocene conditions successfully predicted the current species distribution. Large suitable areas existed during the Pliocene, which were strongly reduced during the Pleistocene, but humid refugia within the Mediterranean Basin and Macaronesian islands enabled long‐term persistence. Future climate conditions are likely to re‐open areas suitable for colonization north of the current range. Main conclusions The climatic requirements of Laurus remained virtually unchanged over the last 3 Myr. This marked niche conservatism imposed largely deterministic range dynamics driven by climate conditions. This species's relatively high drought tolerance might account for the survival of Laurus in continental Europe throughout the Quaternary whilst other Lauraceae became extinct. Climatic scenarios for the end of this century would favour an expansion of the species's range towards northern latitudes, while severely limiting southern populations due to increased water stress.     

The geography and ecology of plant speciation: range overlap and niche divergence in sister species

A goal of evolutionary biology is to understand the roles of geography and ecology in speciation. The recent shared ancestry of sister species can leave a major imprint on their geographical and ecological attributes, possibly revealing processes involved in speciation. We examined how ecological similarity, range overlap and range asymmetry are related to time since divergence of 71 sister species pairs in the California Floristic Province (CFP). We found that plants exhibit strikingly different age-range correlation patterns from those found for animals; the latter broadly support allopatric speciation as the primary mode of speciation. By contrast, plant sisters in the CFP were sympatric in 80% of cases and range sizes of sisters differed by a mean of 10-fold. Range overlap and range asymmetry were greatest in younger sisters. These results suggest that speciation mechanisms broadly grouped under ‘budding’ speciation, in which a larger ranged progenitor gives rise to a smaller ranged derivative species, are probably common. The ecological and reproductive similarity of sisters was significantly greater than that of sister–non-sister congeners for every trait assessed. However, shifts in at least one trait were present in 93% of the sister pairs; habitat and soil shifts were especially common. Ecological divergence did not increase with range overlap contrary to expectations under character displacement in sympatry. Our results suggest that vicariant speciation is more ubiquitous in animals than plants, perhaps owing to the sensitivity of plants to fine-scale environmental heterogeneity. Despite high levels of range overlap, ecological shifts in the process of budding speciation may result in low rates of fine-scale spatial co-occurrence. These results have implications for ecological studies of trait evolution and community assembly; despite high levels of sympatry, sister taxa and potentially other close relatives, may be missing from local communities.     

广州城区生态安全岛典型植物群落的结构及物种多样性研究

以广州城区生态安全岛典型的自然和半自然型植物群落为研究对象,通过样方调查,对物种组成、区系成分、群落结构、珍稀濒危种、物种丰富度和多样性等要素进行了研究,结果表明:广州城区6处生态安全岛3.238hm²的调查样方中,共记录到维管束植物145科342属495种,热带亚热带区系特征明显。不同保护级别的珍稀濒危植物6科7属7种;群落垂直结构复杂,乔木层一般都能划分亚层。物种丰富度Partrick指数值在22-100之间变化、Shannon-Wiener多样性指数值在0.3861-3.0901之间变化、Simpson优势度指数值在0.1380-0.9261之间变化以及Pielou均匀度指数值J_sw在0.1289-0.9427之间变化,相似性系数S和Bray-Curtis指数存在一定差异。目前广州城区生态安全岛的植物群落随着正向演替的进行,物种多样性在不断增加。在区系上,生态安全岛与具有南亚热带地带性典型植被的鼎湖山联系较密切,虽然在物种多样性方面尚有一定差距,但演替时间较长的生态安全岛植物群落的物种多样性已相当于鼎湖山南亚热带地带性植被演替的后期阶段。植被之间的空间距离、与城市中心距离的远近等生境条件差异、人为干扰均对群落的物种多样性产生影响。因此,需加强保护,才能在高度城市化的区域保存这样一些具有地带性顶级群落的结构和物种多样性特征的植物群落。     

Quantitative metrics of overlaps in Grinnellian niches: advances and possible drawbacks

Aim Studies of environmental niche shift/niche conservatism that are based on species distribution modelling require a quantification of niche purity and potential overlap. Although various metrics have been proposed for this task, no comparisons of their performance are available yet that express the linearity of range shifts and error‐proneness. Herein, we assess the performance of six niche overlap metrics using three sister pairs of plethodontid salamanders as well as artificial species to test for linearity of overlap curves, impacts of varying potential distribution sizes and study area sizes. Location North America, artificial environments. Methods Species distribution models for the salamanders were performed with Maxent , and artificial species were created in the R environment. Potential distributions of species with varying range sizes and extents of the study area were compared using the Bray–Curtis distance BC, Schoener's D, two different modifications of the Hellinger distance I_mod, I_cor, Pianka's O and Horn's R. Niche overlaps in ecological space were compared using linear discriminant analyses based on principal components. Results Simulations of niche overlaps revealed strong variations in the performance of the niche overlap metrics. In artificial species, BC and D performed best, followed by O, R and I_cor, but the modified Hellinger distance I_mod showed a nonlinear slope and a truncated range. Furthermore, the simulations suggest that, in proportionally small potential distributions on large grids, an inclusion of a high proportion of grid cells with low occurrence probabilities representing background noise may bias assessments of niche overlaps. Main conclusions Both the salamander examples and simulations suggest that Schoener's D and the Bray–Curtis distance BC are best suited to compute niche overlaps from potential distributions derived from species distribution models. However, like all analysed metrics, both D and BC are seriously affected by the inclusion of high numbers of grid cells where the species are probably absent, i.e. with low occurrence probabilities. Therefore, pre‐processing to eliminate background noise in the potential distribution grids is highly recommended.