Using community and population approaches to understand how contemporary and historical factors have shaped species distribution in river ecosystems

Aim To examine how the employment of both community‐ and population‐level approaches can provide a wider view of the importance of contemporary and historical factors on current species distribution. We posit that community ecology should provide more information about contemporary factors, whereas population genetics should provide better information about historical factors. Location Rivers of the western Mediterranean Basin, including four subregions differing in geological history: the Iberian Plate, Transitional, Betic and Rif. Methods For a community‐level approach, Trichoptera richness and community composition were compared between subregions using species accumulation curves and a correspondence analysis. For a population‐level approach, the mtDNA cytochrome C oxidase subunit I (COI) gene of specimens of the Trichoptera midstream‐lowland species Chimarra marginata (L.) was sequenced and analysed using phylogeographical methods. Results The community approach revealed that historical events had more influence on headwater communities than contemporary ecological factors, whereas historical events had negligible influence on midstream‐lowland communities. In midstream‐lowland sites, however, the population approach showed that the genetic structure of C. marginata differed significantly between subregions and revealed patterns of historical gene migration. In terms of species richness, the Rif subregion had the lowest value per basin due to local climatic features and isolation. Main conclusions Both community‐ and population‐level approaches yielded information about the effects of historical factors on species distribution. However, the importance of historical events on current Trichoptera communities depends on the river zonation. Unlike headwater sites, midstream‐lowland sites showed signs of historical events at the population level but not at the community level at the scale used, indicating that both approaches should be employed together in biogeographical studies. Lack of detection of historical events at the community level does not necessarily mean that they are negligible. Most likely, the organizational level used is not appropriate. We also stress the importance of implementing conservation measures for rivers in the western Mediterranean, especially under future scenarios of climate change and human disturbances in the Mediterranean Basin.     

Plant invasions in the rivers of the Iberian Peninsula,south-western Europe: A review

Aquatic and riparian ecosystems are known to be highly vulnerable to invasive alien species (IAS), especially when subjected to human-induced disturbances. In the last three decades, we have witnessed a growing increase in plant invasions in Portugal and Spain (Iberian Peninsula, south-western Europe), with very detrimental economic, social and ecological effects. Some of these species, such as the giant reed (Arundo donax L.) and the water hyacinth (Eichhornia crassipes (Mart.) Solms-Laub.), number among the world's worst weeds. We present an appraisal of this invasive alien river flora and the most problematic aquatic weeds. We review various aspects of invasion ecology, including spatial and temporal patterns of invasion, species invasiveness, species traits of invasive weeds, and relationships between human disturbance in rivers and surrounding areas and invasibility, and contextualize them in overall state-of-the-art terms. We also acknowledge the use of IAS as bioindicators of the ecological quality of rivers, wetlands and riparian zones. Remote-sensing tools and Geographic Information Systems for detecting and monitoring IAS in Iberian rivers are presented.     

Heterogeneity of periphyton in French Mediterranean rivers

The ecological niche of periphytic algae can be characterized by a long list of environmental variables: hydrology, substratum, light, water chemistry, temperature, other biota (Rott, 1991). In the french mediterranean area, all the watercourse types are represented; we investigated permanent or intermittent, natural or perturbed streams, large rivers or brooks and tricklets flowing out on limestone or crystalline massifs. Most of studies are based on samples of periphyton from natural substrata (e. g. pebbles, cobbles, sand, silt and clay and macrophytes), but also some from artificial substrata. We also sampled simultaneously measurements of water quality and other relevant environmental variables. All investigations in mediterranean area show the high sensibility of periphyton reacting quickly to environmental parameters; it is shown by a heterogeneous pattern of colonization at different levels.

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Résumé Selon Rott (1991), la niche écologique des algues périphytiques peut être caractérisée par une longue liste de paramètres environnementaux: hydrologie, substratum, lumière, chimie des eaux, température et autres facteurs biotiques. Les peuplements d'algues des rivières du sud-est de la France ont été très longtemps délaissés ou très peu étudiés. Cependant de nombreux types de cours d'eau sont représentés (permanents ou temporaires, naturels ou perturbés, larges rivières ou petits cours d'eau s'écoulant sur des massifs karstiques ou cristallins). La morphométrie de ces cours d'eau est fréquemment et profondément remaniée par les stress hydriques liés aux caractéristiques climatiques de la région.Des études menées depuis plus de dix ans sur des substrats naturels (cailloux, galets, sables, argiles, limons et macrophytes) permettent de constater que, du fait de sa très grande sensibilité, le periphyton réagit rapidement aux variations des conditions expérimentales ce qui se traduit par une très forte hétérogénéité de colonisation.

     

An intercontinental comparison of dung beetle diversity between two mediterranean-climatic regions: local versus regional and historical influences

The species richness of biological communities is influenced by both local ecological, regional ecological, and historical factors. The relative importance of these factors may be deduced by comparison between communities in climatically and ecologically equivalent, but geographically and historically separate regions of the world. This claim is based on the hypothesis that community processes driven by similar local ecological factors lead to convergence in species richness whereas those driven by differing regional or historical factors lead to divergence. An intercontinental comparison between the winter rainfall regions of South Africa and the Iberian Peninsula showed that overall species richness of dung beetles was dissimilar at local, subregional and regional scales in Scarabaeidae s. str. but similar at all scales in Aphodiinae. Removal of species widespread in the summer rainfall region of Africa or the temperate region of Europe (regional component) resulted in dissimilarity in species richness of mediterranean endemics at all scales in both dung beetle taxa. However, the lines joining each set of species richness values were parallel which may indicate similarities in processes between different mediterranean climatic regions despite slight differences in latitudinal range. The dominant pattern of dissimilarity or non-convergence may be related primarily to intercontinental differences in regional biogeographical and evolutionary history (faunal dispersal, glaciation effects in relation to geographical barriers to dispersal, speciation history, long-term disturbance history). The limited pattern of similarity or convergence in overall species richness of Aphodiinae may be a chance result or primarily related to intercontinental similarities in local ecological factors.     

The caddisfly fauna (Insecta, Trichoptera) of the rivers of the Black Sea basin in Kosovo with distributional data for some rare species

Adult caddisflies were collected from 12 stations in the Black Sea basin in Kosovo using UV light traps. Sixty-five of the seventy-six species reported in this paper are first records for the Kosovo caddisfly fauna. The unexpected discovery of several species during this investigation: Agapetus delicatulus McLachlan, 1884, Psychomyia klapaleki Malicky, 1995, Tinodes janssensi Jacquemart, 1957, Hydropsyche emarginata Navas, 1923, Drusus botosaneanui Kumanski, 1968, Potamophylax rotundipennis (Brauer, 1857), Potamophylax schmidi Marinković-Gospodnetić, 1970, Ceraclea albimacula (Rambur, 1842), Helicopsyche bacescui Orghidan & Botosaneanu, 1953, Adicella filicornis (Pictet, 1834), Beraea maurus (Curtis, 1834) and Beraeamyia hrabei Mayer, 1937 illustrates that collections from poorly investigated areas in Europe will almost certainly revise the existing knowledge on the distribution of these and other species.     

Phylogeography,historical demography and habitat suitability modelling of freshwater fishes inhabiting seasonally fluctuating Mediterranean river systems: a case study using the Iberian cyprinid Squalius valentinus

The Mediterranean freshwater fish fauna has evolved under constraints imposed by the seasonal weather/hydrological patterns that define the Mediterranean climate. These conditions have influenced the genetic and demographic structure of aquatic communities since their origins in the Mid‐Pliocene. Freshwater species in Mediterranean‐type climates will likely constitute genetically well‐differentiated populations, to varying extents depending on basin size, as a consequence of fragmentation resulting from drought/flood cycles. We developed an integrative framework to study the spatial patterns in genetic diversity, demographic trends, habitat suitability modelling and landscape genetics, to evaluate the evolutionary response of Mediterranean‐type freshwater fish to seasonal fluctuations in weather. To test this evolutionary response, the model species used was Squalius valentinus, an endemic cyprinid of the Spanish Levantine area, where seasonal weather fluctuations are extreme, although our findings may be extrapolated to other Mediterranean‐type species. Our results underscore the significant role of the Mediterranean climate, along with Pleistocene glaciations, in diversification of S. valentinus. We found higher nuclear diversity in larger drainage basins, but higher mitochondrial diversity correlated to habitat suitability rather than basin size. We also found strong correlation between genetic structure and climatic factors associated with Mediterranean seasonality. Demographic and migration analyses suggested population expansion during glacial periods that also contributed to the current genetic structure of S. valentinus populations. The inferred models support the significant contribution of precipitation and temperature to S. valentinus habitat suitability and allow recognizing areas of habitat stability. We highlight the importance of stable habitat conditions, fostered by typical karstic springs found on the Mediterranean littoral coasts, for the preservation of freshwater species inhabiting seasonally fluctuating river systems.     

Flow regulation by dams affects ecosystem metabolism in Mediterranean rivers

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Composition of Endemic Fish Assemblages in Relation to Exotic Species and River Regulation in a Temperate Stream

Spatial variation in the fish community of the regulated Raia stream (Portugal) was examined during the summer of 1995. Variation in the native fish community (abundance of species-size combinations) was explicitly related to both the abundance of exotic species and habitat variables. The fish community changed in space from assemblages characterised by the high relative abundance of Leuciscus pyrenaicus, Leuciscus alburnoides and the smaller size classes of Barbus bocagei (all Iberian endemics with total length, TL, < 100mm to assemblages characterised by the high relative abundance of Chondrostoma polylepis (Iberian endemic) and B. bocagei with TL > 200mm and of exotics Micropterus salmoides and Lepomis gibbosus (> 100mm TL). The former assemblages used shallow sites far from downstream dams with some current whereas the latter assemblages used deeper sites closer to downstream dams without current velocity and with abundant floating macrophytes. Both exotic species and habitat variables were significant correlates of endemic assemblage composition in the Raia stream and the abundance of M. salmoides > 150mm in TL was the best biotic predictor of endemic assemblage composition. The total variation in the community of endemic fish was partitioned into four components: (i) associated uniquely with exotic species - 12.6%, (ii) associated uniquely with habitat variables - 27.6%, (iii) associated both with exotic species and habitat variables - 14.5%, and (iv) that unexplained - 45.3%. A significant association of exotic species with the endemic fish community remained after accounting for the selected environmental variables and a strong (habitat) x (exotic species) interaction was indicated.     

一种濒危大疣蛛的潜在分布区域以及气候变暖的影响

本研究的目的是i)确定伊比利亚半岛一种大疣蛛(Macrothele calpeiana)分布的气候相关性以预测其潜在分布,ii)详细阐述该物种在伊比利亚半岛的分布假说,iii)通过推断模型预测确认该物种在北非和整个地中海地区的适合区域,iv)预测气候变暖对蜘蛛潜在分布区的影响。基于物种的存在、远离目前环境条件下的可能缺失以及其它的气候参数,使用广义线性模型发展了潜在分布的可预测模型。蜘蛛在伊比利亚半岛上的潜在分布远大于目前已知的分布区,延伸到尚未发现蜘蛛分布的葡萄牙广大地区。本文提出了该种大疣蛛在适合分布区域内没有分布的历史因素。北非具有适合该物种的条件但却没有该属物种的分布支持了大疣蛛(Macrothele)祖先的东方起源假说。对地中海地区蜘蛛分布的推断突出显示了阿根廷地区有合适的分布区,该地区也发现有另一种欧洲大疣蛛。气候变暖将对现存于伊比利亚的M.calpeiana种群产生负面影响,因为气候变暖将减少并破碎化蜘蛛在北非的潜在栖息地。目前,急需确认在葡萄牙广大地区是否存在蜘蛛物种,发展对该属的系统发育研究以确定大疣蛛属起源和扩散史的理论。     

Past distribution and ecology of the cork oak (Quercus suber) in the Iberian Peninsula: a pollen-analytical approach

Abstract.  This study presents pollen-analytical data from continental and offshore Iberian Peninsula sites that include pollen curves of Quercus suber , to provide information on the past distribution and ecology of the cork oak ( Q. suber ). Results centre on a new pollen record of Navarrés (Valencia, eastern Spain), which shows that the cork oak survived regionally during the Upper Pleistocene and was important during a mid-Holocene replacement of a local pine forest by Quercus -dominated communities. This phenomenon appears linked to the recurrence of fire and reinforces the value of the cork oak for reforestation programmes in fire-prone areas. In addition to Navarrés, other Late Quaternary pollen sequences (Sobrestany, Casablanca-Almenara, Padul, SU 8103, SU8113, 8057B) suggest last glacial survival of the cork oak in southern and coastal areas of the Peninsula and North Africa. Important developments also occur from the Late Glacial to the middle Holocene, not only in the west but also in the eastern Peninsula. It is suggested that, in the absence of human influence, Q. suber would develop in non-monospecific forests, sharing the arboreal stratum both with other sclerophyllous and deciduous Quercus and Pinus species.     

Rainfall seasonality determines annual/perennial grass balance in vegetation of Mediterranean Iberian

Much recent attention has been focused on the invasion and dominance of annual grass species in areas thought to have been historically dominated by perennial life forms. Explanations of this phenomenon in the literature have focused on two mechanisms favoring annuals: ruderal strategy associated with disturbance, and stress escaping associated with dry sites or deserts. Here I present evidence from vegetation surveys at 50 sites across a 1,200 km band of the Iberian Peninsula—a source region for many invasive annuals—showing that relative annual versus perennial grass composition is not well correlated with degree of disturbance or average annual precipitation. However, annual dominance is strongly and significantly linked to the seasonality of precipitation, in particular the relative intensity of summer drought. Disturbance was significantly associated with annual grass dominance in Iberia, but with much less explanatory power than summer drought intensity. Slope, aspect, and soil parent material were not significantly correlated with annual versus perennial grass dominance. These results suggest that subtle differences in rainfall seasonality largely drive grass composition in herbaceous Mediterranean vegetation. Furthermore, the patterns of annual grass invasion observed in the world’s other Mediterranean climate regions may be associated with similar climatic drivers.     

Past distribution of epiphyllous liverworts in China: The usability of historical data

Epiphyllous liverworts form a special group of bryophytes that primarily grow on the leaves of understory vascular plants in tropical and subtropical evergreen broadleaf forests. Being sensitive to moisture and temperature changes, epiphyllous liverworts are often considered to be good indicators of climate change and forest degradation. However, they are a poorly collected and taxonomically complicated group, with an only partly identified distribution pattern. In this study, we built four models based on 24 environmental variables at four different spatial resolutions (i.e., 1 km, 5 km, 10 km, and 15 km) to predict the past distribution of epiphyllous liverworts in China, using Maxent model and 63 historical location records (i.e., presence‐only data). Both area under the curve of the receiver operating characteristic (AUC) and true skill statistic (TSS) methods are used to assess the model performance. Results showed that the model with the predictors at a 15‐km resolution achieved the highest predictive accuracy (AUC=0.946; TSS=0.880), although there was no statistically significant difference between the four models (p > 0.05). The most significant environmental variables included aridity, annual precipitation, precipitation of wettest month, precipitation of wettest quarter, and precipitation of warmest quarter, annual mean NDVI, and minimum NDVI. The predicted suitable areas for epiphyllous liverworts were mainly located in the south of Yangtze River and seldom exceed 35°N, which were consistent with the museum and herbarium records, as well as the historical records in scientific literatures. Our study further demonstrated the value of historical data to ecological and evolutionary studies.     

Environmental suitability of new reported localities of the funnelweb spider Macrothele calpeiana: an assessment using potential distribution modelling with presence‐only techniques

Aim The funnelweb spider Macrothele calpeiana is endemic to the southern half of the Iberian Peninsula, but recent occurrence records from localities in Spain, North Africa and other regions of Europe, which are distant from its native populations, suggest human‐mediated dispersal, probably associated with the commercial export of olive trees. The main goal of this study was to assess the environmental suitability of these new records and to discuss the spider’s potential to become an invasive species, mainly in new regions across Central Europe and the Mediterranean Basin. Location Central Europe, Mediterranean Basin. Methods Using presence points from the Iberian native populations of M. calpeiana and a set of climatic variables, four presence‐only algorithms (BIOCLIM, DOMAIN, GARP and Maxent) were applied to model the potential distribution of the spider. The models were transferred to Central Europe and the Mediterranean Basin, and the locations of the new records in both the occupied and potential environmental spaces were screened. Results The four models were generally congruent in predicting the existence of a suitable climate for the species across the Mediterranean Basin, although BIOCLIM and DOMAIN yielded more constrained predictions than GARP and Maxent. Whereas the new records from Central Europe were located far from the occupied and potential climatic spaces, those from the Iberian Peninsula were not. Main conclusions Climatic suitability together with propagule pressure owing to human activities will certainly enhance the opportunities for M. calpeiana to colonize new areas across the Mediterranean Basin. The species has invaded areas beyond its native range, and those new locations located in the Iberian Peninsula and North Africa show environmental suitability for the spider and deserve long‐term monitoring. Although the new locations in Central Europe were not predicted by the climate models and the persistence of the species seems improbable, the possibility of rapid evolution or phenotypic plasticity processes raises the need for caution over the possibility of a future spread of M. calpeiana across Europe. Stronger controls over the transport of trees must be applied, and further studies on the ecology of the spider are imperative to assess the possible impact on the invaded ecosystems.     

The temporal and spatial distribution of nematodes in percolating filters

The spatial and temporal distribution of nematodes in two low rate percolating filter bed sewage treatment plants at Carnforth and Caton, Lancashire, were investigated. Nematodes were abundant reaching densities up to 900 cm⁻² of media surface. Numbers decreased down the bed and species composition displayed spatial differences with bed depth. Eight orders of nematode were represented, members of the sub-family Diplogasterinae and Rhabditinae were particularly common. A seasonal pattern of abundance was clearly apparent; two peaks occurred, one in May and a second during the winter months. Lowest numbers corresponded with periods of highest temperature. The demise of the nematodes in the spring was related to the sloughing of the surface film on the media.